WorldWideScience

Sample records for single short pulse

  1. 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.

  2. Temperature field analysis of single layer TiO2 film components induced by long-pulse and short-pulse lasers.

    Science.gov (United States)

    Wang, Bin; Zhang, Hongchao; Qin, Yuan; Wang, Xi; Ni, Xiaowu; Shen, Zhonghua; Lu, Jian

    2011-07-10

    To study the differences between the damaging of thin film components induced by long-pulse and short-pulse lasers, a model of single layer TiO(2) film components with platinum high-absorptance inclusions was established. The temperature rises of TiO(2) films with inclusions of different sizes and different depths induced by a 1 ms long-pulse and a 10 ns short-pulse lasers were analyzed based on temperature field theory. The results show that there is a radius range of inclusions that corresponds to high temperature rises. Short-pulse lasers are more sensitive to high-absorptance inclusions and long-pulse lasers are more easily damage the substrate. The first-damage decision method is drawn from calculations. © 2011 Optical Society of America

  3. Temperature field analysis of single layer TiO2 film components induced by long-pulse and short-pulse lasers

    International Nuclear Information System (INIS)

    Wang Bin; Zhang Hongchao; Qin Yuan; Wang Xi; Ni Xiaowu; Shen Zhonghua; Lu Jian

    2011-01-01

    To study the differences between the damaging of thin film components induced by long-pulse and short-pulse lasers, a model of single layer TiO 2 film components with platinum high-absorptance inclusions was established. The temperature rises of TiO 2 films with inclusions of different sizes and different depths induced by a 1 ms long-pulse and a 10 ns short-pulse lasers were analyzed based on temperature field theory. The results show that there is a radius range of inclusions that corresponds to high temperature rises. Short-pulse lasers are more sensitive to high-absorptance inclusions and long-pulse lasers are more easily damage the substrate. The first-damage decision method is drawn from calculations.

  4. Pain score of patients undergoing single spot, short pulse laser versus conventional laser for diabetic retinopathy.

    Science.gov (United States)

    Mirshahi, Ahmad; Lashay, Alireza; Roozbahani, Mehdi; Fard, Masoud Aghsaei; Molaie, Saber; Mireshghi, Meysam; Zaferani, Mohamad Mehdi

    2013-04-01

    To compare pain score of single spot short duration time (20 milliseconds) panretinal photocoagulation (PRP) with conventional (100 milliseconds) PRP in diabetic retinopathy. Sixty-six eyes from 33 patients with symmetrical severe non-proliferative diabetic retinopathy (non-PDR) or proliferative diabetic retinopathy (PDR) were enrolled in this prospective randomized controlled trial. One eye of each patient was randomized to undergo conventional and the other eye to undergo short time PRP. Spot size of 200 μm was used in both laser types, and energy was adjusted to achieve moderate burn on the retina. Patients were asked to mark the level of pain felt during the PRP session for each eye on the visual analog scale (VAS) and were examined at 1 week, and at 1, 2, 4 and 6 months. Sixteen women and 17 men with mean age 58.9 ± 7.8 years were evaluated. The conventional method required a mean power of 273 ± 107 mW, whereas the short duration method needed 721 ± 406 mW (P = 0.001). An average of 1,218 ± 441 spots were delivered with the conventional method and an average of 2,125 ± 503 spots were required with the short duration method (P = 0.001). Average pain score was 7.5 ± 1.14 in conventional group and 1.75 ± 0.87 in the short duration group (P = 0.001). At 1 week, 1 month, and 4 months following PRP, the mean changes of central macular thickness (CMT) from baseline in the conventional group remained 29.2 μm (P = 0.008), 40.0 μm (P = 0.001), and 40.2 μm (P = 0.007) greater than the changes in CMT for short time group. Patient acceptance of short time single spot PRP was high, and well-tolerated in a single session by all patients. Moreover, this method is significantly less painful than but just as effective as conventional laser during 6 months of follow-up. The CMT change was more following conventional laser than short time laser.

  5. Short pulse neutron generator

    Science.gov (United States)

    Elizondo-Decanini, Juan M.

    2016-08-02

    Short pulse neutron generators are described herein. In a general embodiment, the short pulse neutron generator includes a Blumlein structure. The Blumlein structure includes a first conductive plate, a second conductive plate, a third conductive plate, at least one of an inductor or a resistor, a switch, and a dielectric material. The first conductive plate is positioned relative to the second conductive plate such that a gap separates these plates. A vacuum chamber is positioned in the gap, and an ion source is positioned to emit ions in the vacuum chamber. The third conductive plate is electrically grounded, and the switch is operable to electrically connect and disconnect the second conductive plate and the third conductive plate. The at least one of the resistor or the inductor is coupled to the first conductive plate and the second conductive plate.

  6. Pulse pile-up. I: Short pulses

    International Nuclear Information System (INIS)

    Wilkinson, D.H.

    1990-07-01

    The search for rare large pulses against an intense background of smaller ones involves consideration of pulse pile-up. Approximate methods are presented, based on ruin theory, by which the probability of such pile-up may be estimated for pulses of arbitrary form and of arbitrary pulse-height distribution. These methods are checked against cases for which exact solutions are available. The present paper is concerned chiefly with short pulses of finite total duration. (Author) (5 refs., 24 figs.)

  7. Short-wavelength soft-x-ray laser pumped in double-pulse single-beam non-normal incidence

    International Nuclear Information System (INIS)

    Zimmer, D.; Ros, D.; Guilbaud, O.; Habib, J.; Kazamias, S.; Zielbauer, B.; Bagnoud, V.; Ecker, B.; Aurand, B.; Kuehl, T.; Hochhaus, D. C.; Neumayer, P.

    2010-01-01

    We demonstrated a 7.36 nm Ni-like samarium soft-x-ray laser, pumped by 36 J of a neodymium:glass chirped-pulse amplification laser. Double-pulse single-beam non-normal-incidence pumping was applied for efficient soft-x-ray laser generation. In this case, the applied technique included a single-optic focusing geometry for large beam diameters, a single-pass grating compressor, traveling-wave tuning capability, and an optimized high-energy laser double pulse. This scheme has the potential for even shorter-wavelength soft-x-ray laser pumping.

  8. Numerical simulations of single and double ionization of H2 in short intense laser pulses

    International Nuclear Information System (INIS)

    Baier, Silvio

    2008-01-01

    Rescattering is the dominant process leading to double ionization in atoms and molecules interacting with linearly polarized laser pulses with wavelengths around 800 nm and in an intensity regime of 10 14 to 10 15 W/cm 2 . Using numerical integrations of the two-electron Schroedinger equation of the Hydrogen molecule in appropriate reduced dimensions two mechanisms, namely correlated emission of the electrons and excitation followed by field ionization after rescattering, could be identified and characterized. With the help of a planar model in reduced dimensions these mechanisms were quantitatively compared by their dependence on the molecular alignment with respect to the polarization axis. Two additional mechanisms, which are also related to rescattering, could be identified as well. (orig.)

  9. Dynamics of Al/Fe{sub 2}O{sub 3} MIC combustion from short single-pulse photothermal initiation and time-resolved spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stiegman, Albert E.; Park, Chi-Dong; Mileham, Melissa; Van de Burgt, Lambertus J. [Department of Chemistry and Biochemistry, Florida State University Tallahassee, FL (United States); Kramer, Michael P. [AFRL/MNME Eglin AFB, FL (United States)

    2009-08-15

    Time-resolved spectroscopy was used to study the dynamics of the photothermal ignition of Al/Fe{sub 2}O{sub 3} metastable intermolecular composites after single short-pulse laser initiation. The dynamics were recorded in several time domains from nanosecond to microsecond to quantify the dynamics from initial laser excitation to combustion. Time-averaged spectral data were also collected for the overall emission occurring during combustion. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  10. Picosecond, single pulse electron linear accelerator

    International Nuclear Information System (INIS)

    Kikuchi, Riichi; Kawanishi, Masaharu

    1979-01-01

    The picosecond, single pulse electron linear accelerators, are described, which were installed in the Nuclear Engineering Laboratory of the University of Tokyo and in the Nuclear Radiation Laboratory of the Osaka University. The purpose of the picosecond, single pulse electron linear accelerators is to investigate the very short time reaction of the substances, into which gamma ray or electron beam enters. When the electrons in substances receive radiation energy, the electrons get high kinetic energy, and the energy and the electric charge shift, at last to the quasi-stable state. This transient state can be experimented with these special accelerators very accurately, during picoseconds, raising the accuracy of the time of incidence of radiation and also raising the accuracy of observation time. The outline of these picosecond, single pulse electron linear accelerators of the University of Tokyo and the Osaka University, including the history, the systems and components and the output beam characteristics, are explained. For example, the maximum energy 30 -- 35 MeV, the peak current 1 -- 8 n C, the pulse width 18 -- 40 ps, the pulse repetition rate 200 -- 720 pps, the energy spectrum 1 -- 1.8% and the output beam diameter 2 -- 5 mm are shown as the output beam characteristics of the accelerators in both universities. The investigations utilizing the picosecond single pulse electron linear accelerators, such as the investigation of short life excitation state by pulsed radiation, the dosimetry study of pulsed radiation, and the investigation of the transforming mechanism and the development of the transforming technology from picosecond, single pulse electron beam to X ray, vacuum ultraviolet ray and visual ray, are described. (Nakai, Y.)

  11. A Single-Pulse Integrator

    DEFF Research Database (Denmark)

    Miller, Arne

    1974-01-01

    A single-pulse integrator is described. It gives a relative measure of the integral of the output signal from a coil monitor on the Risø 10 MeV linear accelerator, and displays the value on a digital voltmeter. The reproduccibility is found to be better than ±1% for an accelerated pulse charge...

  12. Short Pulse Laser Applications Design

    International Nuclear Information System (INIS)

    Town, R.J.; Clark, D.S.; Kemp, A.J.; Lasinski, B.F.; Tabak, M.

    2008-01-01

    demonstrate FI. Our design work has focused on the NIF, which is the only facility capable of forming a full-scale hydro assembly, and could be adapted for full-scale FI by the conversion of additional beams to short-pulse operation.

  13. Ultrawide spectral broadening and compression of single extremely short pulses in the visible, uv-vuv, and middle infrared by high-order stimulated Raman scattering

    International Nuclear Information System (INIS)

    Kalosha, V. P.; Herrmann, J.

    2003-01-01

    We present the results of a comprehensive analytical and numerical study of ultrawide spectral broadening and compression of isolated extremely short visible, uv-vuv and middle infrared (MIR) pulses by high-order stimulated Raman scattering in hollow waveguides. Spectral and temporal characteristics of the output pulses and the mechanism of pulse compression using dispersion of the gas filling and output glass window are investigated without the slowly varying envelope approximation. Physical limitations due to phase mismatch, velocity walk off, and pump-pulse depletion as well as improvements through the use of pump-pulse sequences and dispersion control are studied. It is shown that phase-locked pulses as short as ∼2 fs in the visible and uv-vuv, and 6.5 fs in the MIR can be generated by coherent scattering in impulsively excited Raman media without the necessity of external phase control. Using pump-pulse sequences, shortest durations in the range of about 1 fs for visible and uv-vuv probe pulses are predicted

  14. Broadband and short (10-ps) pulse generation on Nova

    International Nuclear Information System (INIS)

    Perry, M.D.; Browning, D.; Bibeau, C.; Patterson, F.G.; Wilcox, R.; Henesian, M.

    1990-01-01

    The ability to produce high power broadband pulses for purposes of focal spot beam smoothing has recently become an important issue in inertial confinement fusion (ICF). As the first step toward the generation and propagation of such pulses on Nova, the authors have performed a series of experiments with 10-ps pulses. Aside from the inherently broad bandwidth, these short pulses have important applications in ICF experiments and x-ray laser research. The author's experimental results are discussed. The short pulses were produced by diffraction grating pulse compression of chirped pulses formed from self-phase modulation in a single-mode 10-m fused silica fiber. Use of such a short fiber produces a nonlinearly chirped spectrum of 0.74 nm. The central nearly linearly chirped 0.26 nm is selected by polarization discrimination and compressed using 1800-line/mm diffraction gratings to a nearly Gaussian pulse of 10 ps FWHM with an energy contrast ratio of 20:1. This 1-nJ pulse is injected into a Nova amplifier chain with selected amplifiers unfired

  15. 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...

  16. 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...

  17. Fine-scale movement responses of free-ranging harbour porpoises to capture, tagging and short-term noise pulses from a single airgun

    DEFF Research Database (Denmark)

    van Beest, Floris; Teilmann, Jonas; Hermannsen, Line

    2018-01-01

    , with natural behaviour resumed in less than or equal to 24 h. When we exposed porpoises to airgun pulses at ranges of 420–690 m with noise level estimates of 135–147 dB re 1 µPa2s (sound exposure level), one individual displayed rapid and directed movements away from the exposure site and two individuals used...... them to a single 10 inch3 underwater airgun producing high-intensity noise pulses (2–3 s intervals) for 1 min. All five porpoises responded to capture and tagging with longer, faster and more directed movements as well as with shorter, shallower, less wiggly dives immediately after release...... to the noise exposure. Changes in natural behaviour following anthropogenic disturbances may reduce feeding opportunities, and evaluating potential population-level consequences should be a priority research area....

  18. Controlled generation of a single Trichel pulse and a series of single Trichel pulses in air

    Science.gov (United States)

    Mizeraczyk, Jerzy; Berendt, Artur; Akishev, Yuri

    2018-04-01

    In this paper, a simple method for the controlled generation of a single Trichel pulse or a series of single Trichel pulses of a regulated repetition frequency in air is proposed. The concept of triggering a single Trichel pulse or a series of such pulses is based on the precise controlling the voltage inception of the negative corona, which can be accomplished through the use of a ramp voltage pulse or a series of such pulses with properly chosen ramp voltage pulse parameters (rise and fall times, and ramp voltage pulse repetition frequency). The proposal has been tested in experiments using a needle-to-plate electrode arrangement in air, and reproducible Trichel pulses (single or in a series) were obtained by triggering them with an appropriately designed voltage waveform. The proposed method and results obtained have been qualitatively analysed. The analysis provides guidance for designing the voltage ramp pulse in respect of the generation of a single Trichel pulse or a series of single Trichel pulses. The controlled generation of a single Trichel pulse or a series of such pulses would be a helpful research tool for the refined studies of the fundamental processes in a negative corona discharge in a single- (air is an example) and multi-phase gaseous fluids. The controlled generation of a single Trichel pulse or a series of Trichel pulses can also be attractive for those corona treatments which need manipulation of the electric charge and heat portions delivered by the Trichel pulses to the object.

  19. Integrable discretizations of the short pulse equation

    International Nuclear Information System (INIS)

    Feng Baofeng; Maruno, Ken-ichi; Ohta, Yasuhiro

    2010-01-01

    In this paper, we propose integrable semi-discrete and full-discrete analogues of the short pulse (SP) equation. The key construction is the bilinear form and determinant structure of solutions of the SP equation. We also give the determinant formulas of N-soliton solutions of the semi-discrete and full-discrete analogues of the SP equations, from which the multi-loop and multi-breather solutions can be generated. In the continuous limit, the full-discrete SP equation converges to the semi-discrete SP equation, and then to the continuous SP equation. Based on the semi-discrete SP equation, an integrable numerical scheme, i.e. a self-adaptive moving mesh scheme, is proposed and used for the numerical computation of the short pulse equation.

  20. Complementarity of long pulse and short pulse spallation sources

    Energy Technology Data Exchange (ETDEWEB)

    Mezei, F [Hahn-Meitner-Institut Berlin GmbH (Germany)

    1995-11-01

    The complementarity of short pulse spallation sources (SPSS) and steady state (CW) reactors is a widely accepted concept. SPSS and long pulse spallation sources (LPSS) are complementary in two ways: (a) in their performance in neutron scattering experiments LPSS closely emulate CW reactors. In this respect two facets of the time-of-flight (TOF) monochromator method adequate for LPSS will be discussed: the superiority of the TOF approach to the crystal monochromator method in high resolution powder diffraction, and the novel technique of repetition rate multiplication in TOF spectroscopy, (b) LPSS combined with adequate chopper systems can also emulate SPSS in a number of applications. It will be shown that the LPSS method of producing short neutron pulses is more efficient for cold and thermal neutrons (below an energy of about 100 MeV), while SPSS is the more favourable approach for hot, epithermal neutrons, i.e. in the slowing down regime in contrast to the moderated regime. These two aspects of complementarity of LPSS and SPSS lead to the conclusions that for about 75% of the spectrum of neutron scattering experiments as known of today the LPSS approach is the most advantageous one with a feasible neutron intensity exceeding that available at ILL by a factor of about 30, while for the remaining 25% of applications the SPSS technique is superior with a well-known potential of a similar gain over present day performances. (author) 7 figs., 6 refs.

  1. Complementarity of long pulse and short pulse spallation sources

    International Nuclear Information System (INIS)

    Mezei, F.

    1995-01-01

    The complementarity of short pulse spallation sources (SPSS) and steady state (CW) reactors is a widely accepted concept. SPSS and long pulse spallation sources (LPSS) are complementary in two ways: a) in their performance in neutron scattering experiments LPSS closely emulate CW reactors. In this respect two facets of the time-of-flight (TOF) monochromator method adequate for LPSS will be discussed: the superiority of the TOF approach to the crystal monochromator method in high resolution powder diffraction, and the novel technique of repetition rate multiplication in TOF spectroscopy, b) LPSS combined with adequate chopper systems can also emulate SPSS in a number of applications. It will be shown that the LPSS method of producing short neutron pulses is more efficient for cold and thermal neutrons (below an energy of about 100 MeV), while SPSS is the more favourable approach for hot, epithermal neutrons, i.e. in the slowing down regime in contrast to the moderated regime. These two aspects of complementarity of LPSS and SPSS lead to the conclusions that for about 75% of the spectrum of neutron scattering experiments as known of today the LPSS approach is the most advantageous one with a feasible neutron intensity exceeding that available at ILL by a factor of about 30, while for the remaining 25% of applications the SPSS technique is superior with a well-known potential of a similar gain over present day performances. (author) 7 figs., 6 refs

  2. DURATION LIMIT OF LASER PULSES EMITTED FROM A Ce-DOPED CRYSTAL SHORT CAVITY

    Directory of Open Access Journals (Sweden)

    Le Hoang Hai

    2017-11-01

    Full Text Available Based on the rate equation set for broadband cavities, the dependence of pulse duration on cavity and pumping parameters is analyzed. The cavity uses a Ce-doped crystal as a gain medium. Computation results show the variation of the pulse width with the change of cavity length, mirror reflectivity, pumping energy and pumping pulse duration. A significant influence of multiple-pulse operation in limiting pulse duration is realized and a pulse-width of the order 200 ps is found to be the limit for the direct generation of ultraviolet single picosecond pulses from a Ce:LLF short cavity.

  3. Non-vacuum, single-step conductive transparent ZnO patterning by ultra-short pulsed laser annealing of solution-deposited nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Daeho; Pan, Heng; Kim, Eunpa; Grigoropoulos, Costas P. [University of California, Department of Mechanical Engineering, Berkeley, CA (United States); Ko, Seung Hwan [Korea Advanced Institute of Science and Technology (KAIST), Department of Mechanical Engineering, Daejeon (Korea, Republic of); Park, Hee K. [AppliFlex LLC, Sunnyvale, CA (United States)

    2012-04-15

    A solution-processable, high-concentration transparent ZnO nanoparticle (NP) solution was successfully synthesized in a new process. A highly transparent ZnO thin film was fabricated by spin coating without vacuum deposition. Subsequent ultra-short-pulsed laser annealing at room temperature was performed to change the film properties without using a blanket high temperature heating process. Although the as-deposited NP thin film was not electrically conductive, laser annealing imparted a large conductivity increase and furthermore enabled selective annealing to write conductive patterns directly on the NP thin film without a photolithographic process. Conductivity enhancement could be obtained by altering the laser annealing parameters. Parametric studies including the sheet resistance and optical transmittance of the annealed ZnO NP thin film were conducted for various laser powers, scanning speeds and background gas conditions. The lowest resistivity from laser-annealed ZnO thin film was about 4.75 x 10{sup -2} {omega} cm, exhibiting a factor of 10{sup 5} higher conductivity than the previously reported furnace-annealed ZnO NP film and is even comparable to that of vacuum-deposited, impurity-doped ZnO films within a factor of 10. The process developed in this work was applied to the fabrication of a thin film transistor (TFT) device that showed enhanced performance compared with furnace-annealed devices. A ZnO TFT performance test revealed that by just changing the laser parameters, the solution-deposited ZnO thin film can also perform as a semiconductor, demonstrating that laser annealing offers tunability of ZnO thin film properties for both transparent conductors and semiconductors. (orig.)

  4. Lax representations for matrix short pulse equations

    Science.gov (United States)

    Popowicz, Z.

    2017-10-01

    The Lax representation for different matrix generalizations of Short Pulse Equations (SPEs) is considered. The four-dimensional Lax representations of four-component Matsuno, Feng, and Dimakis-Müller-Hoissen-Matsuno equations are obtained. The four-component Feng system is defined by generalization of the two-dimensional Lax representation to the four-component case. This system reduces to the original Feng equation, to the two-component Matsuno equation, or to the Yao-Zang equation. The three-component version of the Feng equation is presented. The four-component version of the Matsuno equation with its Lax representation is given. This equation reduces the new two-component Feng system. The two-component Dimakis-Müller-Hoissen-Matsuno equations are generalized to the four-parameter family of the four-component SPE. The bi-Hamiltonian structure of this generalization, for special values of parameters, is defined. This four-component SPE in special cases reduces to the new two-component SPE.

  5. Extremely Short Optical Pulses and Ads/CFT Compliance

    Directory of Open Access Journals (Sweden)

    Konobeeva N.N.

    2015-01-01

    Full Text Available Dynamics of few cycle optical pulses in non-Fermi liquid was considered. Energy spectrum of non-Fermi liquid was taken from the AdS/CFT compliance. Conditions of quasiparticle excitation existence were defined. Non-Fermi liquid parameters impact on the shape of few cycle pulses were estimated. It was shown that extremely short optical pulse propagation in the non-Fermi liquid is a stable pattern. The value of chemical potential has a significant impact on extremely short pulse shape. An increase in initial pulse amplitude does not result in pulse-shape distortions under its propagation in considered medium that is why the non-Fermi liquid can be used in applications inherent in extremely short pulse processing.

  6. 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.)

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

    International Nuclear Information System (INIS)

    Schimpf, Damian Nikolaus

    2010-01-01

    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.)

  8. Stimulated brillouin backscatter of a short-pulse laser

    International Nuclear Information System (INIS)

    Hinkel, D.E.; Williams, E.A.; Berger, R.L.

    1994-01-01

    Stimulated Brillouin backscattering (SBBS) from a short-pulse laser, where the pulse length is short compared to the plasma length, is found to be qualitatively different than in the long pulse regime, where the pulse length is long compared to the plasma length. We find that after an initial transient of order the laser pulse length transit time, the instability reaches a steady state in the variables x' = x - V g t, t' = t, where V g is the pulse group velocity. In contrast, SBBS in a long pulse can be absolutely unstable and grows indefinitely, or until nonlinearities intervene. We find that the motion of the laser pulse induces Doppler related effects that substantially modify the backscattered spectrum at higher intensities, where the instability is strongly coupled (i.e. , has a growth rate large compared to the ion acoustic frequency)

  9. Evaluation of cytogenetic effects of very short laser pulsed radiations

    International Nuclear Information System (INIS)

    Guedeney, G.; Courant, D.; Malarbet, J.-L.; Dolloy, M.-T.; Court, L.

    1992-01-01

    The aim of this study is to evaluate the capacity of a laser, delivering very short pulses in the near infrared spectrum with a high pulse ratio frequency, to induce genetic modification on biological tissues. Chromatid exchanges and chromosomal aberrations studies are used to test potential effect on human lymphocytes. The laser irradiation induces a significant increase of acentric fragments but the absence of dicentric suggests that a repetitive very short pulses irradiation has a relatively low capacity to induce genetic abnormalities. (author)

  10. 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.

  11. 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.

  12. Ultra-short laser pulses. Petawatt and femtosecond

    International Nuclear Information System (INIS)

    Lemoine, P.

    1999-01-01

    This book deals with a series of new results obtained thanks to the use of ultra-short laser pulses. This branch of physics has made incredible progresses during the last 25 years. Ultra-short laser pulses offer the opportunity to explore the domain of ultra-high energies and of ultra-short duration events. Applications are various, from controlled nuclear fusion to eye surgery and to more familiar industrial applications such as electronics. (J.S.)

  13. Single flux pulses affecting the ensemble of superconducting qubits

    Science.gov (United States)

    Denisenko, M. V.; Klenov, N. V.; Satanin, A. M.

    2018-02-01

    The present study is devoted to development of a technique for numerical simulation of the wave function dynamics the single Josephson qubits and arrays of noninteracting qubits controlled by ultra-short pulses. We wish to demonstrate the feasibility of a new principle of basic logical operations on the picosecond timescale. The influence of the unipolar pulse ("fluxon") form on the evolution of the state during the execution of the quantum one-qubit operations - "NOT", "READ" and " √{N O T } " - is investigated in the presence of decoherence. In the array of non interacting qubits, the question of the influence of the spread of their energy parameters (tunnel constants) is studied. It is shown that a single unipolar pulse can control a huge array of artificial atoms with 10% spread of geometric parameters in the array.

  14. Concepts for the Temporal Characterization of Short Optical Pulses

    Directory of Open Access Journals (Sweden)

    Walmsley Ian A

    2005-01-01

    Full Text Available Methods for the characterization of the time-dependent electric field of short optical pulses are reviewed. The representation of these pulses in terms of correlation functions and time-frequency distributions is discussed, and the strategies for their characterization are explained using these representations. Examples of the experimental implementations of the concepts of spectrography, interferometry, and tomography for the characterization of pulses in the optical telecommunications environment are presented.

  15. 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.

  16. Single-pulse and multi-pulse femtosecond laser damage of optical single films

    International Nuclear Information System (INIS)

    Yuan Lei; Zhao Yuan'an; He Hongbo; Shao Jianda; Fan Zhengxiu

    2006-01-01

    Laser-induced damage of a single 500 nm HfO 2 film and a single 500 nm ZrO 2 film were studied with single- and multi-pulse femtosecond laser. The laser-induced damage thresholds (LIDT) of both samples by the 1-on-1 method and the 1000-on-1 method were reported. It was discovered that the LIDT of the HfO 2 single film was higher than that of the ZrO 2 single film by both test methods, which was explained by simple Keldysh's multiphoton ionization theory. The LIDT of multi-pulse was lower than that of single-pulse for both samples as a result of accumulative effect. (authors)

  17. Characteristics of short pulse grid pulser for an electron LINAC

    International Nuclear Information System (INIS)

    Wang Guicheng; Fang Zhigao; Hong Jun

    1996-01-01

    An equivalent circuit is used to obtain the output waveform of a short pulse grid pulser for an electron LINAC, and the amplitude of the output pulse is studied as a function of number of switching transistors for some kinds of transistor. Two pulsers were fabricated to fulfill the requirements of the 200 MeV LINAC at NSRL

  18. High-mechanical-strength single-pulse draw tower gratings

    Science.gov (United States)

    Rothhardt, Manfred W.; Chojetzki, Christoph; Mueller, Hans Rainer

    2004-11-01

    The inscription of fiber Bragg gratings during the drawing process is a very useful method to realize sensor arrays with high numbers of gratings and excellent mechanical strength and also type II gratings with high temperature stability. Results of single pulse grating arrays with numbers up to 100 and definite wavelengths and positions for sensor applications were achieved at 1550 nm and 830 nm using new photosensitive fibers developed in IPHT. Single pulse type I gratings at 1550 nm with more than 30% reflectivity were shown first time to our knowledge. The mechanical strength of this fiber with an Ormocer coating with those single pulse gratings is the same like standard telecom fibers. Weibull plots of fiber tests will be shown. At 830 nm we reached more than 10% reflectivity with single pulse writing during the fiber drawing in photosensitive fibers with less than 16 dB/km transmission loss. These gratings are useful for stress and vibration sensing applications. Type II gratings with reflectivity near 100% and smooth spectral shape and spectral width of about 1 nm are temperature stable up to 1200 K for short time. They are also realized in the fiber drawing process. These gratings are useful for temperature sensor applications.

  19. High-energy, short-pulse, carbon-dioxide lasers

    International Nuclear Information System (INIS)

    Fenstermacher, C.A.

    1979-01-01

    Lasers for fusion application represent a special class of short-pulse generators; not only must they generate extremely short temporal pulses of high quality, but they must do this at ultra-high powers and satisfy other stringent requirements by this application. This paper presents the status of the research and development of carbon-dioxide laser systems at the Los Alamos Scientific Laboratory, vis-a-vis the fusion requirements

  20. Radiation and propagation of short acoustical pulses from underground explosions

    International Nuclear Information System (INIS)

    Banister, J.R.

    1982-06-01

    Radiation and propagation of short acoustical pulses from underground nuclear explosions were analyzed. The cone of more intense radiation is defined by the ratio of sound speeds in the ground and air. The pressure history of the radiated pulse is a function of the vertical ground-motion history, the range, the burial depth, and the velocity of longitudinal seismic waves. The analysis of short-pulse propagation employed an N-wave model with and without enegy conservation. Short pulses with initial wave lengths less than 100 m are severely attenuated by the energy loss in shocks and viscous losses in the wave interior. The methods developed in this study should be useful for system analysis

  1. SHORT-PULSE ELECTROMAGNETIC TRANSPONDER FOR HOLE-TO-HOLE USE.

    Science.gov (United States)

    Wright, David L.; Watts, Raymond D.; Bramsoe, Erik

    1983-01-01

    Hole-to-hole observations were made through nearly 20 m of granite using an electromagnetic transponder (an active reflector) in one borehole and a single-hole short-pulse radar in another. The transponder is inexpensive, operationally simple, and effective in extending the capability of a short-pulse borehole radar system to allow hole-to-hole operation without requiring timing cables. A detector in the transponder senses the arrival of each pulse from the radar. Each pulse detection triggers a kilovolt-amplitude pulse for retransmission. The transponder 'echo' may be stronger than that of a passive reflector by a factor of as much as 120 db. The result is an increase in range capability by a factor which depends on attenuation in the medium and hole-to-hole wavepath geometry.

  2. Assessment and mitigation of electromagnetic pulse (EMP) impacts at short-pulse laser facilities

    International Nuclear Information System (INIS)

    Brown, C G Jr; Bond, E; Clancy, T; Dangi, S; Eder, D C; Ferguson, W; Kimbrough, J; Throop, A

    2010-01-01

    The National Ignition Facility (NIF) will be impacted by electromagnetic pulse (EMP) during normal long-pulse operation, but the largest impacts are expected during short-pulse operation utilizing the Advanced Radiographic Capability (ARC). Without mitigation these impacts could range from data corruption to hardware damage. We describe our EMP measurement systems on Titan and NIF and present some preliminary results and thoughts on mitigation.

  3. Self triggered single pulse beam position monitor

    International Nuclear Information System (INIS)

    Rothman, J.L.; Blum, E.B.

    1993-01-01

    A self triggered beam position monitor (BPM) has been developed for the NSLS injection system to provide single pulse orbit measurements in the booster synchrotron, linac, and transport lines. The BPM integrates the negative going portion of 3 nS wide bipolar pickup electrode signals. The gated, self triggering feature confines critical timing components to the front end, relaxing external timing specifications. The system features a low noise high speed FET sampler, a fiber optic gate for bunch and turn selection, and an inexpensive interface to a standard PC data acquisition system

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

    International Nuclear Information System (INIS)

    Wiggins, Samuel Mark

    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 ≤ 3 MW, a duration ≥ 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-amplified coherent spontaneous emission (SACSE). BWO spikes were produced with a peak power ≤ 63 MW and a pulse duration ∼ 250 ps in the Ka-band and ≤ 12 MW and ∼ 170 ps in the W-band. Evidence of superradiant evolution has been observed in the measurements of scaling laws such as power scaling with the current squared and duration scaling inversely with the fourth root of the power. An X-band free-electron maser amplifier, in which a short (1.0ns) injected radiation pulse interacts with a long (∼ 140 ns) electron beam, has been investigated. The interaction is shown to evolve in the linear regime. The peak output power was 320 kW, which corresponded to a gain, approximately constant across the band, of 42 dB. Changes to the spectrum, that occur when the input radiation pulse is injected into electrons with an energy gradient, have been analysed. (author)

  5. Studying the mechanism of micromachining by short pulsed laser

    Science.gov (United States)

    Gadag, Shiva

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

  6. Forge: a short pulse x-ray diagnostic development facility

    International Nuclear Information System (INIS)

    Stradling, G.L.; Hurry, T.R.; Denbow, E.R.; Selph, M.M.; Ameduri, F.P.

    1985-01-01

    A new short pulse x-ray calibration facility has been brought on line at Los Alamos. This facility is being used for the development, testing and calibration of fast x-ray diagnostic systems. The x-ray source consists of a moderate size, sub-nanosecond laser focused at high intensity on an appropriate target material to generate short pulses of x-ray emission from the resulting plasma. Dynamic performance parameters of fast x-ray diagnostic instruments, such as x-ray streak cameras, can be conveniently measured using this facility

  7. High-voltage short-fall pulse generator

    International Nuclear Information System (INIS)

    Dolbilov, G.V.; Fateev, A.A.; Petrov, V.A.

    1986-01-01

    Powerful high-voltage pulses with short fall times and relatively low afterpulse amplitude are required for the deflection systems of accelerators. A generator is described that provides, into a 75-ohm load, a voltage pulse of up to 100 kV with a fall time of less than 1 nsec and a relative afterpulse amplitude of less than or equal to 15%. The generator employs a short-circuited ferrite-filled line in which shock waves are formed. A magnetic section is used to increase power. The switch is a TGI1-2500/50 thyratron. The main causes of afterpulses and methods for reducing their amplitude are examined

  8. 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.

  9. Short-pulse lasers for weather control

    Science.gov (United States)

    Wolf, J. P.

    2018-02-01

    Filamentation of ultra-short TW-class lasers recently opened new perspectives in atmospheric research. Laser filaments are self-sustained light structures of 0.1–1 mm in diameter, spanning over hundreds of meters in length, and producing a low density plasma (1015–1017 cm‑3) along their path. They stem from the dynamic balance between Kerr self-focusing and defocusing by the self-generated plasma and/or non-linear polarization saturation. While non-linearly propagating in air, these filamentary structures produce a coherent supercontinuum (from 230 nm to 4 µm, for a 800 nm laser wavelength) by self-phase modulation (SPM), which can be used for remote 3D-monitoring of atmospheric components by Lidar (Light Detection and Ranging). However, due to their high intensity (1013–1014 W cm‑2), they also modify the chemical composition of the air via photo-ionization and photo-dissociation of the molecules and aerosols present in the laser path. These unique properties were recently exploited for investigating the capability of modulating some key atmospheric processes, like lightning from thunderclouds, water vapor condensation, fog formation and dissipation, and light scattering (albedo) from high altitude clouds for radiative forcing management. Here we review recent spectacular advances in this context, achieved both in the laboratory and in the field, reveal their underlying mechanisms, and discuss the applicability of using these new non-linear photonic catalysts for real scale weather control.

  10. Selective laser melting of hypereutectic Al-Si40-powder using ultra-short laser pulses

    Science.gov (United States)

    Ullsperger, T.; Matthäus, G.; Kaden, L.; Engelhardt, H.; Rettenmayr, M.; Risse, S.; Tünnermann, A.; Nolte, S.

    2017-12-01

    We investigate the use of ultra-short laser pulses for the selective melting of Al-Si40-powder to fabricate complex light-weight structures with wall sizes below 100 μ {m} combined with higher tensile strength and lower thermal expansion coefficient in comparison to standard Al-Si alloys. During the cooling process using conventional techniques, large primary silicon particles are formed which impairs the mechanical and thermal properties. We demonstrate that these limitations can be overcome using ultra-short laser pulses enabling the rapid heating and cooling in a non-thermal equilibrium process. We analyze the morphology characteristics and micro-structures of single tracks and thin-walled structures depending on pulse energy, repetition rate and scanning velocity utilizing pulses with a duration of 500 {fs} at a wavelength of 1030 {nm}. The possibility to specifically change and optimize the microstructure is shown.

  11. Experimental investigation of plasma dynamics in dc and short-pulse magnetron discharges

    International Nuclear Information System (INIS)

    Seo, Sang-Hun; In, Jung-Hwan; Chang, Hong-Young

    2006-01-01

    The spatiotemporal evolution of the electron energy distribution function (EEDF) and of plasma parameters such as the electron density, the electron temperature and the plasma and floating potentials has been investigated using spatially and temporally resolved single Langmuir probe measurements in dc and mid-frequency, short-pulse magnetron discharges with a repetition frequency of 10 kHz and a duty cycle of 10%. In the pulsed discharge of the short duty cycle, a peak electron temperature higher than 10 eV was observed near the cathode fall region during the early phase of the pulse-on, which is about three times higher than the steady-state value of the electron temperature in the dc discharge. The temporal evolution of the measured EEDFs showed the initial efficient electron heating during the early phase of the pulse-on and the subsequent relaxation of electron energy by the inelastic collisions and the diffusive loss. The high-energy electrons generated during the pulse-on phase diffused the downstream region toward the grounded substrate, resulting in a bi-Maxwellian EEDF consisting of the background low-energy electrons and the high-energy electrons. The results of the spatially and temporally resolved probe measurements will be presented and the enhanced efficiency of the electron heating in the short-pulse discharge will be explained on the basis of the global model of a pulsed discharge

  12. Short-pulse propagation in fiber optical parametric amplifiers

    DEFF Research Database (Denmark)

    Cristofori, Valentina

    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...... is implemented to obtain an all-fiber system. The advantages of all fiber-systems are related to their reliability, long-term stability and compactness. Fiber optical parametric chirped pulse amplification is promising for the amplification of such signals thanks to the inherent compatibility of FOPAs with fiber...

  13. 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)

  14. 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,

  15. High-repetition-rate short-pulse gas discharge.

    Science.gov (United States)

    Tulip, J; Seguin, H; Mace, P N

    1979-09-01

    A high-average-power short-pulse gas discharge is described. This consists of a volume-preionized transverse discharge of the type used in gas lasers driven by a Blumlein energy storage circuit. The Blumlein circuit is fabricated from coaxial cable, is pulse-charged from a high-repetition-rate Marx-bank generator, and is switched by a high-repetition-rate segmented rail gap. The operation of this discharge under conditions typical of rare-gas halide lasers is described. A maximum of 900 pps was obtained, giving a power flow into the discharge of 30 kW.

  16. Short-pulse optical parametric chirped-pulse amplification for the generation of high-power few-cycle pulses

    International Nuclear Information System (INIS)

    Major, Zs.; Osterhoff, J.; Hoerlein, R.; Karsch, S.; Fuoloep, J.A.; Krausz, F.; Ludwig-Maximilians Universitaet, Muenchen

    2006-01-01

    Complete test of publication follows. In the quest for a way to generate ultrashort, high-power, few-cycle laser pulses the discovery of optical parametric amplification (OPA) has opened up to the path towards a completely new regime, well beyond that of conventional laser amplification technology. The main advantage of this parametric amplification process is that it allows for an extremely broad amplification bandwidth compared to any known laser amplifier medium. When combined with the chirped-pulse amplification (CPA) principle (i.e. OPCPA), on one hand pulses of just 10 fs duration and 8 mJ pulse energy have been demonstrated. On the other hand, pulse energies of up to 30 J were also achieved on a different OPCPA system; the pulse duration in this case, however, was 100 fs. In order to combine ultrashort pulse durations (i.e. pulses in the few-cycle regime) with high pulse energies (i.e. in the Joule range) we propose tu pump on OPCPA chain with TW-scale short pulses (100 fs - 1 ps instead of > 100 ps of previous OPCPA systems) delivered by a conventional CPA system. This approach inherently improves the conditions for generating high-power ultrashort pulses using OPCPA in the following ways. Firstly, the short pump pulse duration reduces the necessary stretching factor for the seed pulse, thereby increasing stretching and compression fidelity. Secondly, also due to the shortened pump pulse duration, a much higher contrast is achieved. Finally, the significantly increased pump power makes the use of thinner OPCPA crystals possible, which implies an even broader amplification bandwidth, thereby allowing for even shorter pulses. We carried out theoretical investigations to show the feasibility of such a set-up. Alongside these studies we will also present preliminary experimental results of an OPCPA system pumped by the output of our Ti:Sapphire ATLAS laser, currently delivering 350 mJ in 43 fs. An insight into the planned scaling of this technique to petawatt

  17. 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.

  18. 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.

  19. High Average Power, High Energy Short Pulse Fiber Laser System

    Energy Technology Data Exchange (ETDEWEB)

    Messerly, M J

    2007-11-13

    Recently continuous wave fiber laser systems with output powers in excess of 500W with good beam quality have been demonstrated [1]. High energy, ultrafast, chirped pulsed fiber laser systems have achieved record output energies of 1mJ [2]. However, these high-energy systems have not been scaled beyond a few watts of average output power. Fiber laser systems are attractive for many applications because they offer the promise of high efficiency, compact, robust systems that are turn key. Applications such as cutting, drilling and materials processing, front end systems for high energy pulsed lasers (such as petawatts) and laser based sources of high spatial coherence, high flux x-rays all require high energy short pulses and two of the three of these applications also require high average power. The challenge in creating a high energy chirped pulse fiber laser system is to find a way to scale the output energy while avoiding nonlinear effects and maintaining good beam quality in the amplifier fiber. To this end, our 3-year LDRD program sought to demonstrate a high energy, high average power fiber laser system. This work included exploring designs of large mode area optical fiber amplifiers for high energy systems as well as understanding the issues associated chirped pulse amplification in optical fiber amplifier systems.

  20. 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.

  1. Interaction of solitary pulses in single mode optical fibres | Usman ...

    African Journals Online (AJOL)

    Two solitary waves launched, by way of incidence, into an optical fibre from a single pulse if the pulses are in-phase as understood from results of inverse scattering transform method applied to the cubic nonlinear Schrödinger equations, (CNLSE\\'s). The single CNLSE is then understood to describe evolution of coupled ...

  2. 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%.

  3. Picosecond chirped pulse compression in single-mode fibers

    International Nuclear Information System (INIS)

    Wenhua Cao; Youwei Zhang

    1995-01-01

    In this paper, the nonlinear propagation of picosecond chirped pulses in single mode fibers has been investigated both analytically and numerically. Results show that downchirped pulses can be compressed owing to normal group-velocity dispersion. The compression ratio depends both on the initial peak power and on the initial frequency chirp of the input pulse. While the compression ratio depends both on the initial peak power and on the initial frequency chirp of the input pulse. While the compression ratio increases with the negative frequency chirp, it decreases with the initial peak power of the input pulse. This means that the self-phase modulation induced nonlinear frequency chirp which is linear and positive (up-chirp) over a large central region of the pulse and tends to cancel the initial negative chirp of the pulse. It is also shown that, as the negative chirped pulse compresses temporally, it synchronously experiences a spectral narrowing

  4. Generation of short optical pulses for laser fusion. M.L. report No. 2451

    International Nuclear Information System (INIS)

    Kuizenga, D.J.

    1975-06-01

    This report considers some of the problems involved in generating the required short pulses for the laser-fusion program. Short pulses are required to produce the laser fusion, and pulses produced synchronously with this primary pulse are required for plasma diagnostics. The requirements of these pulses are first described. Several methods are considered in order to generate pulses at 1.064 μ to drive the Nd:Glass amplifiers to produce laser fusion. Conditions for optimum energy extraction per short pulse for Nd:YAG and Nd:Glass lasers are given. Four methods are then considered to produce these pulses: (1) using a fast switch to chop the required pulse out of a much longer Q-switched pulse; (2) active mode locking; (3) passive mode locking; and (4) a combination of active and passive mode locking. The use of cavity dumping is also considered to increase the energy per short pulse

  5. A comparison between short pulse spallation source and long pulse spallation source

    Energy Technology Data Exchange (ETDEWEB)

    Aizawa, Kazuya; Watanabe, Noboru; Suzuki, Jun-ichi; Niimura, Nobuo; Morii, Yukio; Katano, Susumu; Osakabe, Toyotaka; Teshigawara, Makoto [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Mezei, F.

    1997-11-01

    The performance for a 5 MW short pulse spallation source (SPSS) and a 4.5 MW long pulse spallation source (LPSS) in a JAERI program which is based on the availability of a 1.5 GeV superconducting linac with a 30 mA peak current for both proton and H{sup -} beams is discussed. We have examined the superiority of SPSS to LPSS. While a LPSS facility is a second option, we propose an SPSS facility as a first option. (author)

  6. A comparison between short pulse spallation source and long pulse spallation source

    International Nuclear Information System (INIS)

    Aizawa, Kazuya; Watanabe, Noboru; Suzuki, Jun-ichi; Niimura, Nobuo; Morii, Yukio; Katano, Susumu; Osakabe, Toyotaka; Teshigawara, Makoto; Mezei, F.

    1997-01-01

    The performance for a 5 MW short pulse spallation source (SPSS) and a 4.5 MW long pulse spallation source (LPSS) in a JAERI program which is based on the availability of a 1.5 GeV superconducting linac with a 30 mA peak current for both proton and H - beams is discussed. We have examined the superiority of SPSS to LPSS. While a LPSS facility is a second option, we propose an SPSS facility as a first option. (author)

  7. Single-cycle Optical Pulses and Isolated Attosecond Pulse Generation

    Science.gov (United States)

    2012-02-29

    picosecond green light from a frequency-doubled hybrid cryogenic Yb:YAG laser system,” 36 UFO /HFSW 2009 (Arcachon, France, Aug. 31-Sept. 4, 2009...High Fields Short Wavelength,” ( UFO VII – HFSW XIII), Arcachon, France, August 31 – September 4, 2009 (invited). 25) Kyung-Han Hong, Juliet Gopinath

  8. Bunching phase evolution of short-pulse FEL oscillator system

    CERN Document Server

    Song, S B; Choi, D I

    2000-01-01

    We studied numerically the short-pulse FEL oscillator system using properly defined bunching phase theta sub B and PSI sub B. In stable operation, we have found that the optical field 'locks' the phase to pi/2 at the trailing edge, which gives the maximum gain. Moreover, electrons can be detrapped from ponderomotive bucket due to the spatial variation of the optical field, and this detrapping effect is a major cause of the limit cycle oscillation of the system. The 'bump' of the output power during the amplification usually exists at the near-perfect cavity synchronism regime, which can be explained as the change of the matching condition between electron micropulse and optical pulse.

  9. Traveling waves of the regularized short pulse equation

    International Nuclear Information System (INIS)

    Shen, Y; Horikis, T P; Kevrekidis, P G; Frantzeskakis, D J

    2014-01-01

    The properties of the so-called regularized short pulse equation (RSPE) are explored with a particular focus on the traveling wave solutions of this model. We theoretically analyze and numerically evolve two sets of such solutions. First, using a fixed point iteration scheme, we numerically integrate the equation to find solitary waves. It is found that these solutions are well approximated by a finite sum of hyperbolic secants powers. The dependence of the soliton's parameters (height, width, etc) to the parameters of the equation is also investigated. Second, by developing a multiple scale reduction of the RSPE to the nonlinear Schrödinger equation, we are able to construct (both standing and traveling) envelope wave breather type solutions of the former, based on the solitary wave structures of the latter. Both the regular and the breathing traveling wave solutions identified are found to be robust and should thus be amenable to observations in the form of few optical cycle pulses. (paper)

  10. 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.

  11. Behavioral changes induced by single and multiple electron beam pulses

    International Nuclear Information System (INIS)

    Pease, V.P.; McNulty, P.J.

    1985-01-01

    The effects of single, and low-dose, high-dose-rate and multiple electron beam pulses on passive avoidance behavior in mice were studied. Passive avoidance was measured by recording the time that an animal took to enter a chamber from a narrow platform. There were four conditions in the experiment: (1) no shock no radiation-control, (2) radiation only, (3) shock only, and (4) radiation plus shock. Forty animals were run for each data point. Dose rate was held constant at 9 x 10/sup 7/ rads/sec. Average doses for the two single pulses were 7.18 and 8.72 rads. The average total dose for a 25 pulse per second condition was 324.0 rads. The differences between the single versus multiple pulse radiation-only conditions were significant with longer avoidance latencies in the multiple pulse condition. Avoidance latencies were also significantly longer in the shock plus radiation condition for the multiple beam pulse than the single pulse. It is concluded that single and multiple electron beam pulses significantly effect behavior, in this case producing avoidance

  12. A single chip pulse processor for nuclear spectroscopy

    International Nuclear Information System (INIS)

    Hilsenrath, F.; Bakke, J.C.; Voss, H.D.

    1985-01-01

    A high performance digital pulse processor, integrated into a single gate array microcircuit, has been developed for spaceflight applications. The new approach takes advantage of the latest CMOS high speed A/D flash converters and low-power gated logic arrays. The pulse processor measures pulse height, pulse area and the required timing information (e.g. multi detector coincidence and pulse pile-up detection). The pulse processor features high throughput rate (e.g. 0.5 Mhz for 2 usec gausssian pulses) and improved differential linearity (e.g. + or - 0.2 LSB for a + or - 1 LSB A/D). Because of the parallel digital architecture of the device, the interface is microprocessor bus compatible. A satellite flight application of this module is presented for use in the X-ray imager and high energy particle spectrometers of the PEM experiment on the Upper Atmospheric Research Satellite

  13. Briquetting of titanium shavings with using of short electrical pulses

    International Nuclear Information System (INIS)

    Abramova, K.B.; Samujlov, S.D.; Filin, Yu.A.

    1998-01-01

    It is proposed and tested a new technology of briquetting of metallic shavings. The technology includes pressing of shavings with comparatively low pressure and processing it by means of short pulse of high density electrical current. Strength of the briquette arrears as a result of the sport electric welding of the contacts between the shaving particles. The technology permits: to produce firm briquettes from the shavings or other scrap of any metal or alloy, for example from titanium; to produce briquettes practically of any porosity; to decrease the compression and abandon heating almost for high-strength alloy in comparison with existing methods [ru

  14. High-order harmonic generation with short-pulse lasers

    International Nuclear Information System (INIS)

    Schafer, K.J.; Krause, J.L.; Kulander, K.C.

    1992-12-01

    Recent progress in the understanding of high-order harmonic conversion from atoms and ions exposed to high-intensity, short-pulse optical lasers is reviewed. We find that ions can produce harmonics comparable in strength to those obtained from neutral atoms, and that the emission extends to much higher order. Simple scaling laws for the strength of the harmonic emission and the maximium observable harmonic are suggested. These results imply that the photoemission observed in recent experiments in helium and neon contains contributions from ions as well as neutrals

  15. Searching for Single Pulses Using Heimdall

    Science.gov (United States)

    Walsh, Gregory; Lynch, Ryan

    2018-01-01

    In radio pulsar surveys, the interstellar medium causes a frequency dependent dispersive delay of a pulsed signal across the observing band. If not corrected, this delay substantially lowers S/N and makes most pulses undetectable. The delay is proportional to an unknown dispersion measure (DM), which must be searched over with many trial values. A number of new, GPU-accelerated codes are now available to optimize this dedispersion task, and to search for transient pulsed radio emission. We report on the use of Heimdall, one such GPU-accelerated tree dedispersion utility, to search for transient radio sources in a Green Bank Telescope survey of the Cygnus Region and North Galactic Plane. The survey is carried out at central frequency of 820 MHz with a goal of finding Fast Radio Bursts, Rotating Radio Transients, young pulsars, and millisecond pulsars. We describe the the survey, data processing pipeline, and follow-up of candidate sources.

  16. PSPICE simulation of bipolar pulse converter based on short-circuited coaxial transmission line

    International Nuclear Information System (INIS)

    Shi Lei; Fan Yajun

    2010-01-01

    The operating principle of the bipolar pulse converter based on short-circuited coaxial transmission line type is given. The output bipolar pulses are simulated by using PSPICE program on condition of different electric length and different impedance of the short-circuited coaxial transmission line. The bipolar pulses are generated by using unipolar pulse with pulse width of 2 ns in experiment, the experimental result fit well with the simulation result. (authors)

  17. Upconversion imaging using short-wave infrared picosecond pulses

    DEFF Research Database (Denmark)

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

    2017-01-01

    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...... 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...... by an improved model that considers the combined image blurring effect due to finite pump beam size, thick nonlinear crystal, and polychromatic infrared illumination....

  18. 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".

  19. High intensive short laser pulse interaction with submicron clusters media

    International Nuclear Information System (INIS)

    Faenov, A. Ya

    2008-01-01

    The interaction of short intense laser pulses with structured targets, such as clusters, exhibits unique features, stemming from the enhanced absorption of the incident laser light compared to solid targets. Due to the increased absorption, these targets are heated significantly, leading to enhanced emission of x rays in the keV range and generation of electrons and multiple charged ions with kinetic energies from tens of keV to tens of MeV. Possible applications of these targets can be an electron/ion source for a table top accelerator, a neutron source for a material damage study, or an x ray source for microscopy or lithography. The overview of recent results, obtained by the high intensive short laser pulse interaction with different submicron clusters media will be presented. High resolution K and L shell spectra of plasma generated by superintense laser irradiation of micron sized Ar, Kr and Xe clusters have been measured with intensity 10"17"-10"19"W/cm"2"and a pulse duration of 30-1000fs. It is found that hot electrons produced by high contrast laser pulses allow the isochoric heating of clusters and shift the ion balance toward the higher charge states, which enhances both the X ray line yield and the ion kinetic energy. Irradiation of clusters, produced from such gas mixture, by a fs Ti:Sa laser pulses allows to enhance the soft X ray radiation of Heβ(665.7eV)and Lyα(653.7eV)of Oxygen in 2-8 times compare with the case of using as targets pure CO"2"or N"2"O clusters and reach values 2.8x10"10"(∼3μJ)and 2.7x10"10"(∼2.9μJ)ph/(sr·pulse), respectively. Nanostructure conventional soft X ray images of 100nm thick Mo and Zr foils in a wide field of view (cm"2"scale)with high spatial resolution (700nm)are obtained using the LiF crystals as soft X ray imaging detectors. When the target used for the ion acceleration studies consists of solid density clusters embedded into the background gas, its irradiation by high intensity laser light makes the target

  20. Enhancement of beam pulse controllability for a single-pulse formation system of a cyclotron

    International Nuclear Information System (INIS)

    Kurashima, Satoshi; Miyawaki, Nobumasa; Kashiwagi, Hirotsugu; Okumura, Susumu; Taguchi, Mitsumasa; Fukuda, Mitsuhiro

    2015-01-01

    The single-pulse formation technique using a beam chopping system consisting of two types of high-voltage beam kickers was improved to enhance the quality and intensity of the single-pulse beam with a pulse interval over 1 μs at the Japan Atomic Energy Agency cyclotron facility. A contamination rate of neighboring beam bunches in the single-pulse beam was reduced to less than 0.1%. Long-term purification of the single pulse beam was guaranteed by the well-controlled magnetic field stabilization system for the cyclotron magnet. Reduction of the multi-turn extraction number for suppressing the neighboring beam bunch contamination was achieved by restriction of a beam phase width and precise optimization of a particle acceleration phase. In addition, the single-pulse beam intensity was increased by a factor of two or more by a combination of two types of beam bunchers using sinusoidal and saw-tooth voltage waveforms. Provision of the high quality intense single-pulse beam contributed to improve the accuracy of experiments for investigation of scintillation light time-profile and for neutron energy measurement by a time-of-flight method

  1. Generation of a single-cycle optical pulse

    International Nuclear Information System (INIS)

    Shverdin, M.Y.; Walker, D.R.; Yavuz, D.D.; Yin, G.Y.; Harris, S.E.

    2005-01-01

    We make use of coherent control of four-wave mixing to the ultraviolet as a diagnostic and describe the generation of a periodic optical waveform where the spectrum is sufficiently broad that the envelope is approximately a single-cycle in length, and where the temporal shape of this envelope may be synthesized by varying the coefficients of a Fourier series. Specifically, using seven sidebands, we report the generation of a train of single-cycle optical pulses with a pulse width of 1.6 fs, a pulse separation of 11 fs, and a peak power of 1 MW

  2. Laser system using ultra-short laser pulses

    Science.gov (United States)

    Dantus, Marcos [Okemos, MI; Lozovoy, Vadim V [Okemos, MI; Comstock, Matthew [Milford, MI

    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.

  3. Generation of ultra short pulses by auto injection in the Nd: YAG laser

    International Nuclear Information System (INIS)

    Faria, I.C. de.

    1986-01-01

    Yhe work presented here, was concerned to the construction of a coherent light source in the near infrared region with pulses of 10 -10 seconds. The auto-injection technique was employed for generating these short pulses with posterior extraction of the pulse applied to a Nd=YAG-pulsed laser. (author) [pt

  4. Modelling hot electron generation in short pulse target heating experiments

    Directory of Open Access Journals (Sweden)

    Sircombe N.J.

    2013-11-01

    Full Text Available Target heating experiments planned for the Orion laser facility, and electron beam driven fast ignition schemes, rely on the interaction of a short pulse high intensity laser with dense material to generate a flux of energetic electrons. It is essential that the characteristics of this electron source are well known in order to inform transport models in radiation hydrodynamics codes and allow effective evaluation of experimental results and forward modelling of future campaigns. We present results obtained with the particle in cell (PIC code EPOCH for realistic target and laser parameters, including first and second harmonic light. The hot electron distributions are characterised and their implications for onward transport and target heating are considered with the aid of the Monte-Carlo transport code THOR.

  5. Delayed neutron spectra from short pulse fission of uranium-235

    International Nuclear Information System (INIS)

    Atwater, H.F.; Goulding, C.A.; Moss, C.E.; Pederson, R.A.; Robba, A.A.; Wimett, T.F.; Reeder, P.; Warner, R.

    1986-01-01

    Delayed neutron spectra from individual short pulse (∼50 μs) fission of small 235 U samples (50 mg) were measured using a small (5 cm OD x 5 cm length) NE 213 neutron spectrometer. The irradiating fast neutron flux (∼10 13 neutrons/cm 2 ) for these measurements was provided by the Godiva fast burst reactor at the Los Alamos Critical Experiment Facility (LACEF). A high speed pneumatic transfer system was used to transfer the 50 mg 235 U samples from the irradiation position near the Godiva assembly to a remote shielded counting room containing the NE 213 spectrometer and associated electronics. Data were acquired in sixty-four 0.5 s time bins and over an energy range 1 to 7 MeV. Comparisons between these measurements and a detailed model calculation performed at Los Alamos is presented

  6. Simulation of intense short-pulse laser-plasma interaction

    International Nuclear Information System (INIS)

    Yamagiwa, Mitsuru

    2000-01-01

    We have completed the massive parallelization of a 2-dimensional giga-particle code and have achieved a 530-fold acceleration rate with 512 processing elements (PE's). Using this we have implemented a simulation of the interaction of a solid thin film and a high intensity laser and have discovered a phenomenon in which high quality short pulses from the far ultraviolet to soft X-rays are generated at the back surface of the thin layer. We have also introduced the atomic process database code (Hullac) and have the possibility for high precision simulations of X-ray laser radiation. With respect to laser acceleration we have the possibility to quantitatively evaluate relativistic self-focusing assumed to occur in higher intensity fields. Ion acceleration from a solid target and an underdense plasma irradiated by an intense and an ultra intense laser, respectively, has also been studied by particle-in-cell (PIC) simulations. (author)

  7. Ion acceleration with ultra intense and ultra short laser pulses

    International Nuclear Information System (INIS)

    Floquet, V.

    2012-01-01

    Accelerating ions/protons can be done using short laser pulse (few femto-seconds) focused on few micrometers area on solid target (carbon, aluminum, plastic...). The electromagnetic field intensity reached on target (≥10 18 W.cm -2 ) allows us to turn the solid into a hot dense plasma. The dynamic motion of the electrons is responsible for the creation of intense static electric field at the plasma boundaries. These electric fields accelerate organic pollutants (including protons) located at the boundaries. This acceleration mechanism known as the Target Normal Sheath Acceleration (TNSA) has been the topic of the research presented in this thesis.The goal of this work has been to study the acceleration mechanism and to increase the maximal ion energy achievable. Indeed, societal application such as proton therapy requires proton energy up to few hundreds of MeV. To proceed, we have studied different target configurations allowing us to increase the laser plasma coupling and to transfer as much energy as possible to ions (target with microspheres deposit, foam target, grating). Different experiments have also dealt with generating a pre-plasma on the target surface thanks to a pre-pulse. On the application side, fluorescent material such as CdWO 4 has been studied under high flux rate of protons. These high flux rates have been, up to now, beyond the conventional accelerators capabilities. (author) [fr

  8. Temporal dynamics of high repetition rate pulsed single longitudinal ...

    Indian Academy of Sciences (India)

    ing (GIG) cavity, single-mode dye laser pumped by high repetition rate ... in a high loss cavity, a detailed theoretical study and optimization of cavity ..... rate for high conversion efficiency and longer pulse width of the single-mode dye laser.

  9. Ultrafast geometric control of a single qubit using chirped pulses

    International Nuclear Information System (INIS)

    Hawkins, Patrick E; Malinovskaya, Svetlana A; Malinovsky, Vladimir S

    2012-01-01

    We propose a control strategy to perform arbitrary unitary operations on a single qubit based solely on the geometrical phase that the qubit state acquires after cyclic evolution in the parameter space. The scheme uses ultrafast linearly chirped pulses and provides the possibility of reducing the duration of a single-qubit operation to a few picoseconds.

  10. S-process studies using single and pulsed neutron exposures

    Science.gov (United States)

    Beer, H.

    The formation of heavy elements by slow neutron capture (s-process) is investigated. A pulsed neutron irradiation leading to an exponential exposure distribution is dominant for nuclei from A = 90 to 200. For the isotopes from iron to zirconium an additional 'weak' s-process component must be superimposed. Calculations using a single or another pulsed neutron exposure for this component have been carried out in order to reproduce the abundance pattern of the s-only and s-process dominant isotopes. For the adjustment of these calculations to the empirical values, the inclusion of new capture cross section data on Se76 and Y89 and the consideration of the branchings at Ni63, Se79, and Kr85 was important. The combination of an s-process with a single and a pulsed neutron exposure yielded a better representation of empirical abundances than a two component pulsed s-process.

  11. S-process studies using single and pulsed neutron exposures

    International Nuclear Information System (INIS)

    Beer, H.

    1986-01-01

    The formation of heavy elements by slow neutron capture (s-process) is investigated. A pulsed neutron irradiation leading to an exponential exposure distribution is dominant for nuclei from A=90 to 200. For the isotopes from iron to zirconium an additional ''weak'' s-process component must be superimposed. Calculations using a single or another pulsed neutron exposure for this component have been carried out in order to reproduce the abundance pattern of the s-only and s-process dominant isotopes. For the adjustment of these calculations to the empirical values, including new capture cross section data on Se76 and Y89 and the consideration of the branchings at Ni63, Se79, and Kr85 was important. The combination of a s-process with a single and a pulsed neutron exposure yielded a better representation of empirical abundances than a two component pulsed s-process

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

    International Nuclear Information System (INIS)

    Glotin, F.; Jaroszynski, D.; Marcouille, O.

    1995-01-01

    Previous spectral and laser pulse length measurements carried out on the CLIO FEL at wavelength λ=8.5 μm 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 Nλ. 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 μm have already been performed to validate the technic, leading to results similar to those obtained with our previous Michelson set-up

  13. 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

    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...

  14. 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.

  15. Single pulse two photon fluorescence lifetime imaging (SP-FLIM) with MHz pixel rate.

    Science.gov (United States)

    Eibl, Matthias; Karpf, Sebastian; Weng, Daniel; Hakert, Hubertus; Pfeiffer, Tom; Kolb, Jan Philip; Huber, Robert

    2017-07-01

    Two-photon-excited fluorescence lifetime imaging microscopy (FLIM) is a chemically specific 3-D sensing modality providing valuable information about the microstructure, composition and function of a sample. However, a more widespread application of this technique is hindered by the need for a sophisticated ultra-short pulse laser source and by speed limitations of current FLIM detection systems. To overcome these limitations, we combined a robust sub-nanosecond fiber laser as the excitation source with high analog bandwidth detection. Due to the long pulse length in our configuration, more fluorescence photons are generated per pulse, which allows us to derive the lifetime with a single excitation pulse only. In this paper, we show high quality FLIM images acquired at a pixel rate of 1 MHz. This approach is a promising candidate for an easy-to-use and benchtop FLIM system to make this technique available to a wider research community.

  16. Enhancement and stabilization of plasma using collinear long-short double-pulse laser-induced breakdown spectroscopy

    Science.gov (United States)

    Cui, Minchao; Deguchi, Yoshihiro; Wang, Zhenzhen; Fujita, Yuki; Liu, Renwei; Shiou, Fang-Jung; Zhao, Shengdun

    2018-04-01

    A collinear long-short dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) method was employed to enhance and stabilize the laser-induced plasma from steel sample. The long-pulse-width laser beam with the pulse width of 60 μs was generated by a Nd: YAG laser which was operated at FR (free running) mode. The comparative experiments were carried out between single pulse LIBS (SP-LIBS) and long-short DP-LIBS. The recorded results showed that the emission intensities and the temperature of plasma were enhanced by long-short DP-LIBS. The plasma images showed that the plasma was bigger and had a longer lifetime in long-short DP-LIBS situation. Through the calculation of time-resolved plasma temperature and intensity ratio, it can be concluded that the plasma was stabilized by the long-pulse-width laser beam. The long-short DP-LIBS method also generated the stable plasma condition from the samples with different initial temperatures, which overcame the difficulties of LIBS in the online measurement for steel production line.

  17. Pulse patterning effect in optical pulse division multiplexing for flexible single wavelength multiple access optical network

    Science.gov (United States)

    Jung, Sun-Young; Kim, Chang-Hun; Han, Sang-Kook

    2018-05-01

    A demand for high spectral efficiency requires multiple access within a single wavelength, but the uplink signals are significantly degraded because of optical beat interference (OBI) in intensity modulation/direct detection system. An optical pulse division multiplexing (OPDM) technique was proposed that could effectively reduce the OBI via a simple method as long as near-orthogonality is satisfied, but the condition was strict, and thus, the number of multiplexing units was very limited. We propose pulse pattern enhanced OPDM (e-OPDM) to reduce the OBI and improve the flexibility in multiple access within a single wavelength. The performance of the e-OPDM and patterning effect are experimentally verified after 23-km single mode fiber transmission. By employing pulse patterning in OPDM, the tight requirement was relaxed by extending the optical delay dynamic range. This could support more number of access with reduced OBI, which could eventually enhance a multiple access function.

  18. XPS studies of short pulse laser interaction with copper

    International Nuclear Information System (INIS)

    Stefanov, P.; Minkovski, N.; Balchev, I.; Avramova, I.; Sabotinov, N.; Marinova, Ts.

    2006-01-01

    The effect of laser ablation on copper foil irradiated by a short 30 ns laser pulse was investigated by X-ray photoelectron spectroscopy. The laser fluence was varied from 8 to 16.5 J/cm 2 and the velocity of the laser beam from 10 to 100 mm/s. This range of laser fluence is characterized by a different intensity of laser ablation. The experiments were done in two kinds of ambient atmosphere: air and argon jet gas. The chemical state and composition of the irradiated copper surface were determined using the modified Auger parameter (α') and O/Cu intensity ratio. The ablation atmosphere was found to influence the size and chemical state of the copper particles deposited from the vapor plume. During irradiation in air atmosphere the copper nanoparticles react with oxygen and water vapor from the air and are deposited in the form of a CuO and Cu(OH) 2 thin film. In argon atmosphere the processed copper surface is oxidized after exposure to air

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

    International Nuclear Information System (INIS)

    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

  20. Multi-time-scale heat transfer modeling of turbid tissues exposed to short-pulsed irradiations.

    Science.gov (United States)

    Kim, Kyunghan; Guo, Zhixiong

    2007-05-01

    A combined hyperbolic radiation and conduction heat transfer model is developed to simulate multi-time-scale heat transfer in turbid tissues exposed to short-pulsed irradiations. An initial temperature response of a tissue to an ultrashort pulse irradiation is analyzed by the volume-average method in combination with the transient discrete ordinates method for modeling the ultrafast radiation heat transfer. This response is found to reach pseudo steady state within 1 ns for the considered tissues. The single pulse result is then utilized to obtain the temperature response to pulse train irradiation at the microsecond/millisecond time scales. After that, the temperature field is predicted by the hyperbolic heat conduction model which is solved by the MacCormack's scheme with error terms correction. Finally, the hyperbolic conduction is compared with the traditional parabolic heat diffusion model. It is found that the maximum local temperatures are larger in the hyperbolic prediction than the parabolic prediction. In the modeled dermis tissue, a 7% non-dimensional temperature increase is found. After about 10 thermal relaxation times, thermal waves fade away and the predictions between the hyperbolic and parabolic models are consistent.

  1. Semi-classical description of Rydberg atoms in strong, single-cycle electromagnetic pulses

    International Nuclear Information System (INIS)

    Jensen, R.V.; Sanders, M.M.

    1993-01-01

    Recent experimental measurements of the excitation and ionization of Rydberg atoms by single-cycle, electromagnetic pulses have revealed a variety of novel features. Because many quantum states are strongly coupled by the broadband radiation in the short pulse, the traditional methods of quantum mechanics are inadequate to account for the experimental results. We have therefore developed a semi-classical description of the interaction of both hydrogenic and non-hydrogenic atoms with single-cycle pulses of intense, electromagnetic radiation which is based on the strong correspondence theory of Percival and Richards. This theory, which was originally introduced for the description of strong atomic collisions, accounts for some of the surprising features of the experimental measurements and provides new predictions for future experimental studies

  2. 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

  3. Structural science using single crystal and pulse neutron scattering

    International Nuclear Information System (INIS)

    Noda, Yukio; Kimura, Hiroyuki; Watanabe, Masashi; Ishikawa, Yoshihisa; Tamura, Itaru; Arai, Masatoshi; Takahashi, Miwako; Ohshima, Ken-ichi; Abe, Hiroshi; Kamiyama, Takashi

    2008-01-01

    The application to single crystal neutron structural analysis is overviewed. Special attention is paid to the pulse neutron method, which will be available soon under J-PARC project in Japan. New proposal and preliminary experiment using Sirius at KENS are described. (author)

  4. LASER PROCESSING ON SINGLE CRYSTALS BY UV PULSE LASER

    OpenAIRE

    龍見, 雅美; 佐々木, 徹; 高山, 恭宜

    2009-01-01

    Laser processing by using UV pulsed laser was carried out on single crystal such as sapphire and diamond in order to understand the fundamental laser processing on single crystal. The absorption edges of diamond and sapphire are longer and shorter than the wave length of UV laser, respectively. The processed regions by laser with near threshold power of processing show quite different state in each crystal.

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

    Energy Technology Data Exchange (ETDEWEB)

    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. Isolated grid electron gun and pulser system for long/short pulse operation

    International Nuclear Information System (INIS)

    Koontz, R.F.; Feathers, L.; Kilbourne, C.; Leger, G.; McKinney, T.

    1984-04-01

    The new NPI gun at SLAC serves the dual functions of producing long pulse (up to 5 μsec, 180 pps) electron bursts for nuclear physics experiments, and also short (1 nsec) pulses for filling Stanford Synchrotron Radiation Laboratory (SSRL). This is accomplished by means of a newly designed, isolated grid gun, cathode pulsed with a solid state long pulse pulser, and grid pulsed with a fast recharging avalanche type short pulse (1 nsec) grid pulser. The grid pulser is bipolar so that a fast blackout notch can be placed in the long cathode pulse. This fast notch can be seen by Stanford Linear Collider (SLC) instrumentation and allows the long pulse beam to be computer controlled by SLC intensity and beam position monitors

  7. An isolated grid electron gun and pulser system for long/short pulse operation

    International Nuclear Information System (INIS)

    Koontz, R.F.; Feathers, L.; Kilbourne, C.; Leger, G.; McKinney, T.

    1984-01-01

    The new NPI gun at SLAC serves the dual functions of producing long pulse (up to 5 μsec, 180 pps) electron bursts for nuclear physics experiments, and also short ( 1 nsec) pulses for filling Stanford Synchrotron Radiation Laboratory (SSRL). This is accomplished by means of a newly designed, isolated grid gun, cathode pulsed with a solid state long pulse pulser, and grid pulsed with a fast recharging avalanche type short pulse (1 nsec) grid pulser. The grid pulser is bipolar so that a fast blackout notch can be placed in the long cathode pulse. This fast notch can be seen by Stanford Linear Collider (SLC) instrumentation and allows the long pulse beam to be computer controlled by SLC intensity and beam position monitors. (orig.)

  8. Dose rate effect on micronuclei induction in human blood lymphocytes exposed to single pulse and multiple pulses of electrons.

    Science.gov (United States)

    Acharya, Santhosh; Bhat, N N; Joseph, Praveen; Sanjeev, Ganesh; Sreedevi, B; Narayana, Y

    2011-05-01

    The effects of single pulses and multiple pulses of 7 MV electrons on micronuclei (MN) induction in cytokinesis-blocked human peripheral blood lymphocytes (PBLs) were investigated over a wide range of dose rates per pulse (instantaneous dose rate). PBLs were exposed to graded doses of 2, 3, 4, 6, and 8 Gy of single electron pulses of varying pulse widths at different dose rates per pulse, ranging from 1 × 10(6) Gy s(-1) to 3.2 × 10(8) Gy s(-1). Different dose rates per pulse were achieved by changing the dose per electron pulse by adjusting the beam current and pulse width. MN yields per unit absorbed dose after irradiation with single electron pulses were compared with those of multiple pulses of electrons. A significant decrease in the MN yield with increasing dose rates per pulse was observed, when dose was delivered by a single electron pulse. However, no reduction in the MN yield was observed when dose was delivered by multiple pulses of electrons. The decrease in the yield at high dose rates per pulse suggests possible radical recombination, which leads to decreased biological damage. Cellular response to the presence of very large numbers of chromosomal breaks may also alter the damage.

  9. Sensitive detection of chlorine in iron oxide by single pulse and dual pulse laser-induced breakdown spectroscopy

    Science.gov (United States)

    Pedarnig, J. D.; Haslinger, M. J.; Bodea, M. A.; Huber, N.; Wolfmeir, H.; Heitz, J.

    2014-11-01

    The halogen chlorine is hard to detect in laser-induced breakdown spectroscopy (LIBS) mainly due to its high excited state energies of 9.2 and 10.4 eV for the most intense emission lines at 134.72 nm and 837.59 nm, respectively. We report on sensitive detection of Cl in industrial iron oxide Fe2O3 powder by single-pulse (SP) and dual-pulse (DP) LIBS measurements in the near infrared range in air. In compacted powder measured by SP excitation (Nd:YAG laser, 532 nm) Cl was detected with limit of detection LOD = 440 ppm and limit of quantitation LOQ = 720 ppm. Orthogonal DP LIBS was studied on pressed Fe2O3 pellets and Fe3O4 ceramics. The transmission of laser-induced plasma for orthogonal Nd:YAG 1064 nm and ArF 193 nm laser pulses showed a significant dependence on interpulse delay time (ipd) and laser wavelength (λL). The UV pulses (λL = 193 nm) were moderately absorbed in the plasma and the Cl I emission line intensity was enhanced while IR pulses (λL = 1064 nm) were not absorbed and Cl signals were not enhanced at ipd = 3 μs. The UV laser enhancement of Cl signals is attributed to the much higher signal/background ratio for orthogonal DP excitation compared to SP excitation and to the increased plasma temperature and electron number density. This enabled measurement at a very short delay time of td ≥ 0.1 μs with respect to the re-excitation pulse and detection of the very rapidly decaying Cl emission with higher efficiency.

  10. 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...

  11. Molecular spinning by a chiral train of short laser pulses

    Science.gov (United States)

    Floß, Johannes; Averbukh, Ilya Sh.

    2012-12-01

    We provide a detailed theoretical analysis of molecular rotational excitation by a chiral pulse train, a sequence of linearly polarized pulses with the polarization direction rotating from pulse to pulse by a controllable angle. Molecular rotation with a preferential rotational sense (clockwise or counterclockwise) can be excited by this scheme. We show that the directionality of the rotation is caused by quantum interference of different excitation pathways. The chiral pulse train is capable of selective excitation of molecular isotopologs and nuclear spin isomers in a mixture. We demonstrate this using 14N2 and 15N2 as examples for isotopologs and para- and ortho-nitrogen as examples for nuclear-spin isomers.

  12. Numerical simulations of single and double ionization of H{sub 2} in short intense laser pulses; Numerische Simulation zur Einfach- und Doppelionisation von H{sub 2} in kurzen intensiven Laserpulsen

    Energy Technology Data Exchange (ETDEWEB)

    Baier, Silvio

    2008-07-01

    Rescattering is the dominant process leading to double ionization in atoms and molecules interacting with linearly polarized laser pulses with wavelengths around 800 nm and in an intensity regime of 10{sup 14} to 10{sup 15} W/cm{sup 2}. Using numerical integrations of the two-electron Schroedinger equation of the Hydrogen molecule in appropriate reduced dimensions two mechanisms, namely correlated emission of the electrons and excitation followed by field ionization after rescattering, could be identified and characterized. With the help of a planar model in reduced dimensions these mechanisms were quantitatively compared by their dependence on the molecular alignment with respect to the polarization axis. Two additional mechanisms, which are also related to rescattering, could be identified as well. (orig.)

  13. Generation of attosecond electron beams in relativistic ionization by short laser pulses

    Science.gov (United States)

    Cajiao Vélez, F.; Kamiński, J. Z.; Krajewska, K.

    2018-03-01

    Ionization by relativistically intense short laser pulses is studied in the framework of strong-field quantum electrodynamics. Distinctive patterns are found in the energy probability distributions of photoelectrons, which are sensitive to the properties of a driving laser field. It is demonstrated that these electrons are generated in the form of solitary attosecond wave packets. This is particularly important in light of various applications of attosecond electron beams such as in ultrafast electron diffraction and crystallography, or in time-resolved electron microscopy of physical, chemical, and biological processes. We also show that, for intense laser pulses, high-energy ionization takes place in narrow regions surrounding the momentum spiral, the exact form of which is determined by the shape of a driving pulse. The self-intersections of the spiral define the momenta for which the interference patterns in the energy distributions of photoelectrons are observed. Furthermore, these interference regions lead to the synthesis of single-electron wave packets characterized by coherent double-hump structures.

  14. Single event effects in pulse width modulation controllers

    International Nuclear Information System (INIS)

    Penzin, S.H.; Crain, W.R.; Crawford, K.B.; Hansel, S.J.; Kirshman, J.F.; Koga, R.

    1996-01-01

    SEE testing was performed on pulse width modulation (PWM) controllers which are commonly used in switching mode power supply systems. The devices are designed using both Set-Reset (SR) flip-flops and Toggle (T) flip-flops which are vulnerable to single event upset (SEU) in a radiation environment. Depending on the implementation of the different devices the effect can be significant in spaceflight hardware

  15. Gating circuit for single photon-counting fluorescence lifetime instruments using high repetition pulsed light sources

    International Nuclear Information System (INIS)

    Laws, W.R.; Potter, D.W.; Sutherland, J.C.

    1984-01-01

    We have constructed a circuit that permits conventional timing electronics to be used in single photon-counting fluorimeters with high repetition rate excitation sources (synchrotrons and mode-locked lasers). Most commercial time-to-amplitude and time-to-digital converters introduce errors when processing very short time intervals and when subjected to high-frequency signals. This circuit reduces the frequency of signals representing the pulsed light source (stops) to the rate of detected fluorescence events (starts). Precise timing between the start/stop pair is accomplished by using the second stop pulse after a start pulse. Important features of our design are that the circuit is insensitive to the simultaneous occurrence of start and stop signals and that the reduction in the stop frequency allows the start/stop time interval to be placed in linear regions of the response functions of commercial timing electronics

  16. Production of ozone using nanosecond short pulsed power

    OpenAIRE

    Shimomura, N.; Wakimoto, M.; Togo, H.; Namihira, Takao; Akiyama, Hidenori; ナミヒラ, タカオ; アキヤマ, ヒデノリ; 浪平, 隆男; 秋山, 秀典

    2003-01-01

    Production of ozone is one of the most typical industrial and commercial applications of electrical discharge. The demand of ozone will be increasing for wholesome and environment-friendly sterilizations. The production of ozone using the pulsed power discharge will apply electron accelerations around the head of streamer discharge. The breakdowns in reactor, however, often limit the efficient production. The pulse shape should be controlled for dimension of the reactor. On the other hand, th...

  17. Development of short pulse laser pumped x-ray lasers

    International Nuclear Information System (INIS)

    Dunn, J; Osterheld, A L; Hunter, J R; Shlyaptsev, V N

    2000-01-01

    X-ray lasers have been extensively studied around the world since the first laboratory demonstration on the Novette laser at LLNL in 1984 [l]. The characteristic properties of short wavelength, high monochromaticity, collimation and coherence make x-ray lasers useful for various applications. These include demonstrations of biological imaging within the water window, interferometry of laser plasmas and radiography of laser-heated surfaces. One of the critical issues has been the high power pump required to produce the inversion. The power scaling as a function of x-ray laser wavelength follows a -k4 to law. The shortest x-ray laser wavelength of ∼ 35 (angstrom) demonstrated for Ni-like All was at the limit of Nova laser capabilities. By requiring large, high power lasers such as Nova, the shot rate and total number of shots available have limited the rapid development of x-ray lasers and applications. In fact over the last fifteen years the main thrust has been to develop more efficient, higher repetition rate x-ray lasers that can be readily scaled to shorter wavelengths. The recent state of progress in the field can be found in references. The objective of the project was to develop a soft x-ray laser (XRL) pumped by a short pulse laser of a few joules. In effect to demonstrate a robust, worlung tabletop x-ray laser at LLNL for the first time. The transient collisional scheme as proposed by Shlyaptsev et al [8, 9] was the candidate x-ray laser for study. The successful endeavour of any scientific investigation is often based upon prudent early decisions and the choice of this scheme was both sound and fruitful. It had been demonstrated very recently for Ne-like Ti at 326 A using a small tabletop laser [10] but had not yet reached its full potential. We chose this scheme for several reasons: (a) it was a collisional-type x-ray laser which has been historically the most robust; (b) it had the promise of high efficiency and low energy threshold for lasing; (c) the

  18. Chirped or time modulated excitation compared to short pulses for photoacoustic imaging in acoustic attenuating media

    Science.gov (United States)

    Burgholzer, P.; Motz, C.; Lang, O.; Berer, T.; Huemer, M.

    2018-02-01

    In photoacoustic imaging, optically generated acoustic waves transport the information about embedded structures to the sample surface. Usually, short laser pulses are used for the acoustic excitation. Acoustic attenuation increases for higher frequencies, which reduces the bandwidth and limits the spatial resolution. One could think of more efficient waveforms than single short pulses, such as pseudo noise codes, chirped, or harmonic excitation, which could enable a higher information-transfer from the samples interior to its surface by acoustic waves. We used a linear state space model to discretize the wave equation, such as the Stoke's equation, but this method could be used for any other linear wave equation. Linear estimators and a non-linear function inversion were applied to the measured surface data, for onedimensional image reconstruction. The proposed estimation method allows optimizing the temporal modulation of the excitation laser such that the accuracy and spatial resolution of the reconstructed image is maximized. We have restricted ourselves to one-dimensional models, as for higher dimensions the one-dimensional reconstruction, which corresponds to the acoustic wave without attenuation, can be used as input for any ultrasound imaging method, such as back-projection or time-reversal method.

  19. THE CRAB PULSAR AT CENTIMETER WAVELENGTHS. II. SINGLE PULSES

    Energy Technology Data Exchange (ETDEWEB)

    Hankins, T. H.; Eilek, J. A. [Physics Department, New Mexico Tech, Socorro, NM 87801 (United States); Jones, G., E-mail: thankins@aoc.nrao.edu [Columbia University, New York, NY 10027 (United States)

    2016-12-10

    We have carried out new, high-frequency, high-time-resolution observations of the Crab pulsar. Combining these with our previous data, we characterize bright single pulses associated with the Main Pulse, both the Low-Frequency and High-Frequency Interpulses, and the two  High-Frequency Components. Our data include observations at frequencies ranging from 1 to 43 GHz with time resolutions down to a fraction of a nanosecond. We find that at least two types of emission physics are operating in this pulsar. Both Main Pulses and Low-Frequency Interpulses, up to ∼10 GHz, are characterized by nanoshot emission—overlapping clumps of narrowband nanoshots, each with its own polarization signature. High-Frequency Interpulses, between 5 and 30 GHz, are characterized by spectral band emission—linearly polarized emission containing ∼30 proportionately spaced spectral bands. We cannot say whether the longer-duration High-Frequency Components pulses are due to a scattering process, or if they come from yet another type of emission physics.

  20. Absorption of short-pulse electromagnetic energy by a resistively loaded straight wire

    International Nuclear Information System (INIS)

    Miller, E.K.; Deadrick, F.J.; Landt, J.A.

    1975-01-01

    Absorption of short-pulse electromagnetic energy by a resistively loaded straight wire is examined. Energy collected by the wire, load energy, peak load currents, and peak load voltages are found for a wide range of parameters, with particular emphasis on nuclear electromagnetic pulse (EMP) phenomena. A series of time-sequenced plots is used to illustrate pulse propagation on wires when loads and wire ends are encountered

  1. Heat wave propagation in a thin film irradiated by ultra-short laser pulses

    International Nuclear Information System (INIS)

    Yoo, Jae Gwon; Kim, Cheol Jung; Lim, C. H.

    2004-01-01

    A thermal wave solution of a hyperbolic heat conduction equation in a thin film is developed on the basis of the Green's function formalism. Numerical computations are carried out to investigate the temperature response and the propagation of the thermal wave inside a thin film due to a heat pulse generated by ultra-short laser pulses with various laser pulse durations and thickness of the film

  2. Generation of strong pulsed magnetic fields using a compact, short pulse generator

    Science.gov (United States)

    Yanuka, D.; Efimov, S.; Nitishinskiy, M.; Rososhek, A.; Krasik, Ya. E.

    2016-04-01

    The generation of strong magnetic fields (˜50 T) using single- or multi-turn coils immersed in water was studied. A pulse generator with stored energy of ˜3.6 kJ, discharge current amplitude of ˜220 kA, and rise time of ˜1.5 μs was used in these experiments. Using the advantage of water that it has a large Verdet constant, the magnetic field was measured using the non-disturbing method of Faraday rotation of a polarized collimated laser beam. This approach does not require the use of magnetic probes, which are sensitive to electromagnetic noise and damaged in each shot. It also avoids the possible formation of plasma by either a flashover along the conductor or gas breakdown inside the coil caused by an induced electric field. In addition, it was shown that this approach can be used successfully to investigate the interesting phenomenon of magnetic field enhanced diffusion into a conductor.

  3. Long-duration nano-second single pulse lasers for observation of spectra from bulk liquids at high hydrostatic pressures

    International Nuclear Information System (INIS)

    Thornton, Blair; Sakka, Tetsuo; Masamura, Tatsuya; Tamura, Ayaka; Takahashi, Tomoko; Matsumoto, Ayumu

    2014-01-01

    The influence of laser pulse duration on the spectral emissions observed from bulk ionic solutions has been investigated for hydrostatic pressures between 0.1 and 30 MPa. Transient pressure, shadowgraph imaging and spectroscopic measurements were performed for single pulses of duration 20 and 150 ns. The transient pressure measurements show that for hydrostatic pressures up to 30 MPa, propagation of the high-pressure shockwave generated by the focused laser causes the local pressure to reduce below ambient levels during the time frame that spectroscopic measurements can be made. The pressure impulse and subsequent reduction in pressure are larger, with the latter lasting longer for the 150 ns pulse compared to a 20 ns pulse of the same energy. The 150 ns pulse generates larger cavities with significant enhancement of the spectral emissions observed compared to the 20 ns duration pulse for pressures up to 30 MPa. The results demonstrate that laser-induced breakdown using a long ns duration pulse offers an advantage over conventional, short ns duration pulses for the analysis of bulk ionic solutions at hydrostatic pressures between 0.1 and 30 MPa. - Highlights: • Long-ns-duration laser pulses enhance the spectra observed from bulk solutions. • Laser-induced shockwaves momentarily reduce pressures to below ambient levels. • 150 ns pulses generate larger cavities than 20 ns pulses of the same energy. • Hydrostatic pressures < 30 MPa have no significant effect on the observed spectra

  4. A Test Bed for Short Pulse OA Detection of Optical Directors in Amphibious Operations

    National Research Council Canada - National Science Library

    Ertem, M

    1999-01-01

    ...) system to detect optical directors of potential threats in amphibious operations. The use of a short pulse duration allows discrimination of retroreflections from natural sources such as rock formations and vegetation...

  5. Alignment of symmetric top molecules by short laser pulses

    DEFF Research Database (Denmark)

    Hamilton, Edward; Seideman, Tamar; Ejdrup, Tine

    2005-01-01

    -resolved photofragment imaging. Using methyliodide and tert-butyliodide as examples, we calculate and measure the alignment dynamics, focusing on the temporal structure and intensity of the revival patterns, including their dependence on the pulse duration, and their behavior at long times, where centrifugal distortion......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...

  6. 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)

  7. Modular High Voltage Pulse Converter for Short Rise and Decay Times

    NARCIS (Netherlands)

    Mao, S.

    2018-01-01

    This thesis explores a modular HV pulse converter technology with short rise and decay times. A systematic methodology to derive and classify HV architectures based on a modularization level of power building blocks of the HV pulse converter is developed to summarize existing architectures and

  8. Short-circuited coil in a solenoid circuit of a pulse magnetic field

    International Nuclear Information System (INIS)

    Kivshik, A.F.; Dubrovin, V.Yu.

    1976-01-01

    A short-circuited coil at the end of a long pulse solenoid attenuates the dissipation field by 3-5 times. A plug-configuration field is set up in the middle portion of the pulse solenoid incorporating the short-circuited coils. Shunting of the coils with the induction current by resistor Rsub(shunt) provides for the adjustment of the plug ratio γ

  9. Influence of short heat pulses on the helium boiling heat transfer rate

    International Nuclear Information System (INIS)

    Andreev, V.K.; Deev, V.I.; Savin, A.N.; Kutsenko, K.V.

    1987-01-01

    Investigation results on heat transfer in the process of helium boiling on a heated wall under conditions of pulsed heat effect are described. Results of the given study point to one of possible ways of heat exchange intensification in boiling helium by supplying short heat pulse to the heater. Even short-time noncontrolled or incidental increase in the heater capacity during experiment with boiling helium can result in a considerable disagreement of experimental data on heat transfer

  10. 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.

  11. Initial color development in radiochromic dye films after a short intense pulse of accelerated electrons

    International Nuclear Information System (INIS)

    Uribe, R.M.; Barcelo, M.; Rios, J.; McLaughlin, W.L.; Buenfil, A.E.

    1990-01-01

    The radiation response of different dye precursors in several host plastics has been investigated after a single short-pulse irradiation with 2.5-MeV electrons. It was observed that in most films the radiation-initiated color development proceeds mainly during the first 300 seconds, after such high dose-rate irradiation (∼ 10 12 Gy/s). Absorption spectra show that the main absorption band increases at the expense of a shorter-wavelength precursor absorption band, showing an isosbestic point approximately midway bwetwen the two absorption bands. It was found that a certain combination of dye precursor and host plastic (namely a polyamide containing an aromatic group) constitutes a film which shows a very fast increase in optical density of the main absorption band, making it suitable for immediate dosimetric analysis in very high dose-rate installations. (author)

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

    CSIR Research Space (South Africa)

    Botha, LR

    2006-09-01

    Full Text Available High pressure CO2 lasers are good candidates for amplifying picosecond mid infrared pulses. High pressure CO2 lasers are notorious for being unreliable and difficult to operate. In this paper a high pressure CO2 laser is presented based on well...

  13. 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...

  14. 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.

  15. Radiobiological response to ultra-short pulsed megavoltage electron beams of ultra-high pulse dose rate.

    Science.gov (United States)

    Beyreuther, Elke; Karsch, Leonhard; Laschinsky, Lydia; Leßmann, Elisabeth; Naumburger, Doreen; Oppelt, Melanie; Richter, Christian; Schürer, Michael; Woithe, Julia; Pawelke, Jörg

    2015-08-01

    In line with the long-term aim of establishing the laser-based particle acceleration for future medical application, the radiobiological consequences of the typical ultra-short pulses and ultra-high pulse dose rate can be investigated with electron delivery. The radiation source ELBE (Electron Linac for beams with high Brilliance and low Emittance) was used to mimic the quasi-continuous electron beam of a clinical linear accelerator (LINAC) for comparison with electron pulses at the ultra-high pulse dose rate of 10(10) Gy min(-1) either at the low frequency of a laser accelerator or at 13 MHz avoiding effects of prolonged dose delivery. The impact of pulse structure was analyzed by clonogenic survival assay and by the number of residual DNA double-strand breaks remaining 24 h after irradiation of two human squamous cell carcinoma lines of differing radiosensitivity. The radiation response of both cell lines was found to be independent from electron pulse structure for the two endpoints under investigation. The results reveal, that ultra-high pulse dose rates of 10(10) Gy min(-1) and the low repetition rate of laser accelerated electrons have no statistically significant influence (within the 95% confidence intervals) on the radiobiological effectiveness of megavoltage electrons.

  16. Interaction of ultra-short ultra-intense laser pulses with under-dense plasmas

    International Nuclear Information System (INIS)

    Solodov, A.

    2000-12-01

    Different aspects of interaction of ultra-short ultra-intense laser pulses with underdense plasmas are studied analytically and numerically. These studies can be interesting for laser-driven electron acceleration in plasma, X-ray lasers, high-order harmonic generation, initial confinement fusion with fast ignition. For numerical simulations a fully-relativistic particle code WAKE was used, developed earlier at Ecole Polytechnique. It was modified during the work on the thesis in the part of simulation of ion motion, test electron motion, diagnostics for the field and plasma. The studies in the thesis cover the problems of photon acceleration in the plasma wake of a short intense laser pulse, phase velocity of the plasma wave in the Self-Modulated Laser Wake-Field Accelerator (SM LWFA), relativistic channeling of laser pulses with duration of the order of a plasma period, ion dynamics in the wake of a short intense laser pulse, plasma wave breaking. Simulation of three experiments on the laser pulse propagation in plasma and electron acceleration were performed. Among the main results of the thesis, it was found that reduction of the plasma wave phase velocity in the SM LWFA is crucial for electron acceleration, only if a plasma channel is used for the laser pulse guiding. Self-similar structures describing relativistic guiding of short laser pulses in plasmas were found and relativistic channeling of initially Gaussian laser pulses of a few plasma periods in duration was demonstrated. It was shown that ponderomotive force of a plasma wake excited by a short laser pulse forms a channel in plasma and plasma wave breaking in the channel was analyzed in detail. Effectiveness of electron acceleration by the laser field and plasma wave was compared and frequency shift of probe laser pulses by the plasma waves was found in conditions relevant to the current experiments. (author)

  17. Formation of very short pulse by neutron spin flip chopper for J-PARC

    International Nuclear Information System (INIS)

    Ebisawa, T.; Soyama, K.; Yamazaki, D.; Tasaki, S.; Sakai, K.; Oku, T.; Maruyama, R.; Hino, M.

    2004-01-01

    We have developed neutron spin flip choppers with high S/N ratio and high intensity for pulsed sources using multi-stage spin flip choppers. It is not easy for us to obtain a very short neutron pulse less than 10 μs using a spin flip chopper, due to the time constant L/R in the normal LR circuit. We will discuss a method obtaining a very short neutron pulse applying the modified push-pull circuit proposed by Ito and Takahashi [4] to the double spin flip chopper with polarizing guides

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

    International Nuclear Information System (INIS)

    André, Jean-Michel; Jonnard, Philippe

    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. (paper)

  19. 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.

  20. Feedback stabilization system for pulsed single longitudinal mode tunable lasers

    Science.gov (United States)

    Esherick, Peter; Raymond, Thomas D.

    1991-10-01

    A feedback stabilization system for pulse single longitudinal mode tunable lasers having an excited laser medium contained within an adjustable length cavity and producing a laser beam through the use of an internal dispersive element, including detection of angular deviation in the output laser beam resulting from detuning between the cavity mode frequency and the passband of the internal dispersive element, and generating an error signal based thereon. The error signal can be integrated and amplified and then applied as a correcting signal to a piezoelectric transducer mounted on a mirror of the laser cavity for controlling the cavity length.

  1. Symmetry issues in a class of ion beam targets using short direct drive pulses

    International Nuclear Information System (INIS)

    Mark, J.W.K.; Lindl, J.D.

    1986-01-01

    We address a class of modified ion beam targets where the symmetry issues are ameliorated in the regime of short bursts of direct drive pulses. Short pulses are here defined so that the fractional change in target radii of peak beam energy deposition are assumed to be small (during each such direct drive burst with a fixed beam focal radius). This requirement is actually not stringent on the temporal pulse-length. In fact we show an explicit example where this can be satisfied by a ≥ 60 ns direct drive pulse-train. A new beam placement scheme is used which systematically eliminated low order spherical harmonic asymmetries. The residual asymmetries of such pulses are studied with both simple model and numerical simulations

  2. Coherent harmonics generated by a super-short electron pulse

    International Nuclear Information System (INIS)

    Ding Wu

    1996-01-01

    A novel mechanism generating superradiance harmonics is found. In this superradiance harmonics, the temporal width of harmonics is extremely short, the ratio of high harmonic fundamental wave is much higher than the known superradiance harmonics

  3. 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.

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

    International Nuclear Information System (INIS)

    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

  5. 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.

  6. High beam quality and high energy short-pulse laser with MOPA

    Science.gov (United States)

    Jin, Quanwei; Pang, Yu; Jiang, JianFeng; Tan, Liang; Cui, Lingling; Wei, Bin; Sun, Yinhong; Tang, Chun

    2018-03-01

    A high energy, high beam quality short-pulse diode-pumped Nd:YAG master oscillator power-amplifier (MOPA) laser with two amplifier stages is demonstrated. The two-rod birefringence compensation was used as beam quality controlling methods, which presents a short-pulse energy of 40 mJ with a beam quality value of M2 = 1.2 at a repetition rate of 400Hz. The MOPA system delivers a short-pulse energy of 712.5 mJ with a pulse width of 12.4 ns.The method of spherical aberration compensation is improved the beam quality, a M2 factor of 2.3 and an optical-to-optical efficiency of 27.7% is obtained at the maximum laser out power.The laser obtained 1.4J out energy with polarization integration.

  7. 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....

  8. Harp, a short pulse, high current electron beam accelerator

    International Nuclear Information System (INIS)

    Prestwich, K.R.

    1974-01-01

    A 3 MV, 800 kA, 24 ns electron beam accelerator is described and the results of initial switching experiments are discussed. The generator will provide a source for studying the physics of processes leading to electron beam driven, inertially confined fusion. The major components of the accelerator are two diodes with a common anode, twelve oil-dielectric Blumleins with low jitter (less than 2 ns) multichannel switches, three intermediate storage capacitors, a trigger pulse generator and two Marx generators. (U.S.)

  9. Applying short-duration pulses as a mean to enhance volatile organic compounds removal by air sparging.

    Science.gov (United States)

    Ben Neriah, Asaf; Paster, Amir

    2017-10-01

    Application of short-duration pulses of high air pressure, to an air sparging system for groundwater remediation, was tested in a two-dimensional laboratory setup. It was hypothesized that this injection mode, termed boxcar, can enhance the remediation efficiency due to the larger ZOI and enhanced mixing which results from the pressure pulses. To test this hypothesis, flow and transport experiments were performed. Results confirm that cyclically applying short-duration pressure pulses may enhance contaminant cleanup. Comparing the boxcar to conventional continuous air-injection shows up to a three-fold increase in the single well radius of influence, dependent on the intensity of the short-duration pressure-pulses. The cleanup efficiency of Toluene from the water was 95% higher than that achieved under continuous injection with the same average conditions. This improvement was attributed to the larger zone of influence and higher average air permeability achieved in the boxcar mode, relative to continuous sparging. Mixing enhancement resultant from recurring pressure pulses was suggested as one of the mechanisms which enhance the contaminant cleanup. The application of a boxcar mode in an existing, multiwell, air sparging setup can be relatively straightforward: it requires the installation of an on-off valve in each of the injection-wells and a central control system. Then, turning off some of the wells, for a short-duration, result in a stepwise increase in injection pressure in the rest of the wells. It is hoped that this work will stimulate the additional required research and ultimately a field scale application of this new injection mode. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. PROTO-II: a short pulse water insulated accelerator

    International Nuclear Information System (INIS)

    Martin, T.H.; VanDevender, J.P.; Johnson, D.L.; McDaniel, D.H.; Aker, M.

    1975-01-01

    A new accelerator, designated Proto-II, is presently under construction at Sandia Laboratories. Proto-II will have a nominal output of 100 kJ into a two-sided diode at a voltage of 1.5 MV and a total current of over 6 MA for 24 ns. This accelerator will be utilized for electron beam fusion experiments and for pulsed power and developmental studies leading to a proposed further factor of five scale-up in power. The design of Proto-II is based upon recent water switching developments and represents a 10-fold extrapolation of those results. Initial testing of Proto-II is scheduled to begin in 1976. Proto-II power flow starts with eight Marx generators which charge 16 water-insulated storage capacitors. Eight triggered, 3 MV, SF 6 gas-insulated switches next transfer the energy through oil-water interfaces into the first stage of 16 parallel lines. Next, the 16 first stages transfer their energy into the pulse forming lines and fast switching sections.The energy is then delivered to two converging, back-to-back, disk-shaped transmission line. Two back-to-back diodes then form the electron beams which are focused onto a common anode

  11. 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.; Lange, D.F. de; Huis in 't Veld, A.J.

    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

  12. Research on imploded plasma heating by short pulse laser for fast ignition

    International Nuclear Information System (INIS)

    Kodama, R.; Kitagawa, Y.; Mima, K.

    2001-01-01

    Since the peta watt module (PWM) laser was constructed in 1995, investigated are heating processes of imploded plasmas by intense short pulse lasers. In order to heat the dense plasma locally, a heating laser pulse should be guided into compressed plasmas as deeply as possible. Since the last IAEA Fusion Conference, the feasibility of fast ignition has been investigated by using the short pulse GEKKO MII glass laser and the PWM laser with GEKKO XII laser. We found that relativistic electrons are generated efficiently in a preformed plasma to heat dense plasmas. The coupling efficiency of short pulse laser energy to a solid density plasma is 40% when no plasmas are pre-formed, and 20% when a large scale plasma is formed by a long pulse laser pre-irradiation. The experimental results are confirmed by numerical simulations using the simulation code 'MONET' which stands for the Monte-Carlo Electron Transport code developed at Osaka. In the GEKKO XII and PWM laser experiments, intense heating pulses are injected into imploded plasmas. As a result of the injection of heating pulse, it is found that high energy electrons and ions could penetrate into imploded core plasmas to enhance neutron yield by factor 3∼5. (author)

  13. Ultrashort and coherent single-electron pulses for diffraction at ultimate resolutions

    International Nuclear Information System (INIS)

    Kirchner, Friedrich Oscar

    2013-01-01

    Ultrafast electron diffraction is a powerful tool for studying structural dynamics with femtosecond temporal and sub-aangstroem spatial resolutions. It benefits from the high scattering cross-sections of electrons compared X-rays and allows the examination of thin samples, surfaces and gases. One of the main challenges in ultrafast electron diffraction is the generation of electron pulses with a short duration and a large transverse coherence. The former limits the temporal resolution of the experiment while the latter determines the maximum size of the scattering structures that can be studied. In this work, we strive to push the limits of electron diffraction towards higher temporal and spatial resolutions. The decisive step in our approach is to eliminate all detrimental effects caused by Coulomb repulsion between the electrons by reducing the number of electrons per pulse to one. In this situation, the electrons' longitudinal and transverse velocity distributions are determined solely by the photoemission process. By reducing the electron source size on the photocathode, we make use of the small transverse velocity spread to produce electron pulses with a transverse coherence length of 20 nm, which is about an order of magnitude larger than the reported values for comparable experiments. The energy distribution of an ensemble of single-electron pulses from a photoemission source is directly linked to the mismatch between the photon energy and the cathode's work function. This excess energy can be reduced by using a photon energy close to the material's work function. Using a tunable source of ultraviolet pulses, we demonstrate the reduction of the velocity spread of the electrons, resulting in a shorter duration of the electron pulses. The reduced electron pulse durations achieved by a tunable excitation or by other approaches require new characterization techniques for electron pulses. We developed a novel method for the characterization of electron pulses at

  14. Chromium carbide thin films deposited by ultra-short pulse laser deposition

    International Nuclear Information System (INIS)

    Teghil, R.; Santagata, A.; De Bonis, A.; Galasso, A.; Villani, P.

    2009-01-01

    Pulsed laser deposition performed by a laser with a pulse duration of 250 fs has been used to deposit films from a Cr 3 C 2 target. Due to the different processes involved in the laser ablation when it is performed by an ultra-short pulse source instead of a conventional short pulse one, it has been possible to obtain in vacuum films containing only one type of carbide, Cr 3 C 2 , as shown by X-ray photoelectron spectroscopy. On the other hand, Cr 3 C 2 is not the only component of the films, since a large amount of amorphous carbon is also present. The films, deposited at room temperature, are amorphous and seem to be formed by the coalescence of a large number of particles with nanometric size. The film composition can be explained in terms of thermal evaporation from particles ejected from the target.

  15. Coherent, Short-Pulse X-ray Generation via Relativistic Flying Mirrors

    Directory of Open Access Journals (Sweden)

    Masaki Kando

    2018-04-01

    Full Text Available Coherent, Short X-ray pulses are demanded in material science and biology for the study of micro-structures. Currently, large-sized free-electron lasers are used; however, the available beam lines are limited because of the large construction cost. Here we review a novel method to downsize the system as well as providing fully (spatially and temporally coherent pulses. The method is based on the reflection of coherent laser light by a relativistically moving mirror (flying mirror. Due to the double Doppler effect, the reflected pulses are upshifted in frequency and compressed in time. Such mirrors are formed when an intense short laser pulse excites a strongly nonlinear plasma wave in tenuous plasma. Theory, proof-of-principle, experiments, and possible applications are addressed.

  16. A nuclear pulse amplitude acquisition system based on 80C31 single-chip microcomputer

    International Nuclear Information System (INIS)

    Zhao Xiuliang; Qu Guopu; Guo Lanying; Zhang Songbai

    1999-01-01

    A kind of multichannel nuclear pulse amplitude signal acquisition system is described, which is composed of pulse peak detector, integrated S/H circuit, A/D converter and 80C31 single-chip microcomputer

  17. Updating the induction module from single-pulse to double-pulses

    International Nuclear Information System (INIS)

    Huang Ziping; Wang Huacen; Deng Jianjun

    2002-01-01

    A double-pulse Linear Induced Accelerator (LIA) module is reconstructed based on a usual simple-pulse LIA module. By changing the length of one of the cables between the inductive cell and the Blumlein pulse forming line, two induction pulses with 90 ns FWHM and 150 kV pulse voltage are generated by the ferrite cores inductive cell. The interval time of the pulses is adjustable by changing the lengths of the cable

  18. UV saturable absorber for short-pulse KrF laser systems.

    Science.gov (United States)

    Nishioka, H; Kuranishi, H; Ueda, K; Takuma, H

    1989-07-01

    A derivative of the linear tricyclic compound, acridine, is shown to be useful as a saturable absorber for short-pulse KrF lasers. The saturation characteristics and absorption recovery of a methanol solution of acridine for a 20-psec KrF laser pulse are reported. We obtain a saturation fluence of 1.2 mJ/cm(2) and a ratio of the primary to the excited absorption cross section of 6.25:1.

  19. UV saturable absorber for short-pulse KrF laser systems

    Energy Technology Data Exchange (ETDEWEB)

    Nishioka, H.; Kuranishi, H.; Ueda, K.; Takuma, H.

    1989-07-01

    A derivative of the linear tricyclic compound, acridine, is shown to beuseful as a saturable absorber for short-pulse KrF lasers. The saturationcharacteristics and absorption recovery of a methanol solution of acridine for a20-psec KrF laser pulse are reported. We obtain a saturation fluence of 1.2mJ/cm/sup 2/ and a ratio of the primary to the excited absorption cross sectionof 6.25:1.

  20. Multiloop soliton and multibreather solutions of the short pulse model equation

    International Nuclear Information System (INIS)

    Matsuno, Yoshimasa

    2007-01-01

    We develop a systematic procedure for constructing the multisoliton solutions of the short pulse (SP) model equation which describes the propagation of ultra-short pulses in nonlinear medica. We first introduce a novel hodograph transformation to convert the SP equation into the sine-Gordon (sG) equation. With the soliton solutions of the sG equation, the system of linear partial differential equations governing the inverse mapping can be integrated analytically to obtain the soliton solutions of the SP equation in the form of the parametric representation. By specifying the soliton parameters, we obtain the multiloop and multibreather solutions. We investigate the asymptotic behavior of both solutions and confirm their solitonic feature. The nonsingular breather solutions may play an important role in studying the propagation of ultra-short pulses in an optical fibre. (author)

  1. 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’.

  2. Verification of the validity of the short-pulse approximation for one-dimensional Rydberg atoms

    International Nuclear Information System (INIS)

    Kopyciuk, T; Grajek, M

    2011-01-01

    In this paper, we investigate the short-pulse approximation (SPA) for one-dimensional Rydberg atoms. We analyse the limits that SPA has to fulfil in order to be applicable. These concern the shape, the duration and the displacement caused by the pulse. The correctness of SPA is tested by comparing the results obtained using SPA with a numerical solution of the set of time-dependent Schroedinger equations. We show that the limit for the displacement caused by the pulse is of greatest importance. Violation of the limit for the duration of the pulse is shown to lead to concurrent violation of the limit for the displacement. We also show that the shape of the pulse has no influence on the created wave packet.

  3. 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.

  4. Short electron bunches generated by perpendicularly crossing laser pulses.

    Czech Academy of Sciences Publication Activity Database

    Horný, Vojtěch; Petržílka, Václav; Klimo, Ondřej; Krůs, Miroslav

    2017-01-01

    Roč. 24, č. 10 (2017), č. článku 103125. ISSN 1070-664X R&D Projects: GA ČR GA15-03118S; GA MŠk(CZ) LM2015083; GA MŠk(CZ) CZ.02.1.01/0.0/0.0/16_013/0001552; GA MŠk LQ1606; GA MŠk(CZ) LD14089 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:61389021 ; RVO:68378271 Keywords : Laser pulses * Particle beam bunching * Plasma simulation * Particle acceleration * Lasers * Particle-in-cell metthod * Particle beams * Electrostatics Subject RIV: BL - Plasma and Gas Discharge Physics; BL - Plasma and Gas Discharge Physics (FZU-D) OBOR OECD: Fluids and plasma physics (including surface physics); Fluids and plasma physics (including surface physics) (FZU-D) Impact factor: 2.115, year: 2016 http://aip.scitation.org/doi/10.1063/1.5007889

  5. GINGER simulations of short-pulse effects in the LEUTL FEL

    International Nuclear Information System (INIS)

    Huang, Z.; Fawley, W.M.

    2001-01-01

    While the long-pulse, coasting beam model is often used in analysis and simulation of self-amplified spontaneous emission (SASE) free-electron lasers (FELs), many current SASE demonstration experiments employ relatively short electron bunches whose pulse length is on the order of the radiation slippage length. In particular, the low-energy undulator test line (LEUTL) FEL at the Advanced Photon Source has recently lased and nominally saturated in both visible and near-ultraviolet wavelength regions with a sub-ps pulse length that is somewhat shorter than the total slippage length in the 22-m undulator system. In this paper we explore several characteristics of the short pulse regime for SASE FELs with the multidimensional, time-dependent simulation code GINGER, concentrating on making a direct comparison with the experimental results from LEUTL. Items of interest include the radiation gain length, pulse energy, saturation position, and spectral bandwidth. We address the importance of short-pulse effects when scaling the LEUTL results to proposed x-ray FELs and also briefly discuss the possible importance of coherent spontaneous emission at startup

  6. 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....

  7. Self-reflection of extremely short light pulses in nonlinear optical waveguides

    Science.gov (United States)

    Kurasov, Alexander E.; Kozlov, Sergei A.

    2004-07-01

    An equation describing the generation of reflected radiation during the propagation of high-intensity extremely short pulses in a nonlinear optical waveguide is derived. The phenomena taking place during the strong self-inducted changes of the temporal structure of the forward wave are studied. It is shown that the duration of the backward pulse is much greater than the duration of the forward pulse and that the main part of the energy of the backward wave is carried by lower frequencies than the central frequency of the forward wave.

  8. Propagation and spatiotemporal coupling characteristics of ultra-short Gaussian vortex pulse

    Science.gov (United States)

    Nie, Jianye; Liu, Guodong; Zhang, Rongzhu

    2018-05-01

    Based on Collins diffraction integral formula, the propagation equation of ultra-short Gaussian vortex pulse beam has been derived. Using the equation, the intensity distribution variations of vortex pulse in the propagation process are calculated. Specially, the spatiotemporal coupling characteristics of ultra-short vortex beams are discussed in detail. The results show that some key parameters, such as transverse distance, transmission distance, pulse width and topological charge number will influence the spatiotemporal coupling characteristics significantly. With the increasing of transverse distance, the waveforms of the pulses distort obviously. And when transmission distance is far than 50 mm, the distribution curve of transverse intensity gradually changes into a Gaussian type. In addition, initial pulse width will affect the distribution of light field, however, when initial pulse width is larger than 3 fs, the spatiotemporal coupling effect will be insignificant. Topological charge number does not affect the time delay characteristics, since with the increasing of topological charge number, the waveform of the pulse distorts gradually but the time delay does not occur.

  9. Efficient and controllable thermal ablation induced by short-pulsed HIFU sequence assisted with perfluorohexane nanodroplets.

    Science.gov (United States)

    Chang, Nan; Lu, Shukuan; Qin, Dui; Xu, Tianqi; Han, Meng; Wang, Supin; Wan, Mingxi

    2018-07-01

    A HIFU sequence with extremely short pulse duration and high pulse repetition frequency can achieve thermal ablation at a low acoustic power using inertial cavitation. Because of its cavitation-dependent property, the therapeutic outcome is unreliable when the treatment zone lacks cavitation nuclei. To overcome this intrinsic limitation, we introduced perfluorocarbon nanodroplets as extra cavitation nuclei into short-pulsed HIFU-mediated thermal ablation. Two types of nanodroplets were used with perfluorohexane (PFH) as the core material coated with bovine serum albumin (BSA) or an anionic fluorosurfactant (FS) to demonstrate the feasibility of this study. The thermal ablation process was recorded by high-speed photography. The inertial cavitation activity during the ablation was revealed by sonoluminescence (SL). The high-speed photography results show that the thermal ablation volume increased by ∼643% and 596% with BSA-PFH and FS-PFH, respectively, than the short-pulsed HIFU alone at an acoustic power of 19.5 W. Using nanodroplets, much larger ablation volumes were created even at a much lower acoustic power. Meanwhile, the treatment time for ablating a desired volume significantly reduced in the presence of nanodroplets. Moreover, by adjusting the treatment time, lesion migration towards the HIFU transducer could also be avoided. The SL results show that the thermal lesion shape was significantly dependent on the inertial cavitation in this short-pulsed HIFU-mediated thermal ablation. The inertial cavitation activity became more predictable by using nanodroplets. Therefore, the introduction of PFH nanodroplets as extra cavitation nuclei made the short-pulsed HIFU thermal ablation more efficient by increasing the ablation volume and speed, and more controllable by reducing the acoustic power and preventing lesion migration. Copyright © 2018. Published by Elsevier B.V.

  10. Single and double long pulse laser ablation of aluminum induced in air and water ambient

    International Nuclear Information System (INIS)

    Akbari Jafarabadi, Marzieh; Mahdieh, Mohammad Hossein

    2017-01-01

    Highlights: • Laser ablation of aluminum target by single and double pulse (∼ 5 ns delay) in ambient air and distilled water • Comparing with air, in ambient water, plasma confinement results in higher crater depth. • In comparison with single pulse laser ablation, the absorption of the laser pulse energy is higher for double pulse regime. • As a result of ablated material expansion, the crater depth is decreased if the target is placed at lower depth. - Abstract: In this paper, single pulse and double pulse laser ablation of an aluminum target in two interaction ambient was investigated experimentally. The interaction was performed by nanosecond Nd:YAG laser beam in air and four depths (i.e. 9, 13, 17, and 21 mm) of distilled water ambient. The irradiation was carried out in single and collinear double pulse configurations in both air and liquid ambient. Crater geometry (depth and diameter) was measured by an optical microscope. The results indicated that the crater geometry strongly depends on both single pulse and double pulse configurations and interaction ambient. In single pulse regime, the crater diameter is higher for all water depths compared to that of air. However, the crater depth, depend on water depth, is higher or lower than the crater depth in air. In double pulse laser ablation, there are greater values for both crater diameters and crater depths in the water.

  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. Correction of echo shift in reconstruction processing for ultra-short TE pulse sequence

    International Nuclear Information System (INIS)

    Takizawa, Masahiro; Ootsuka, Takehiro; Abe, Takayuki; Takahashi, Tetsuhiko

    2010-01-01

    An ultra-short echo time (TE) pulse sequence is composed of a radial sampling that acquires echo signals radially in the K-space and a half-echo acquisition that acquires only half of the echo signal. The shift in the position of the echo signal (echo shift) caused by the timing errors in the gradient magnetic field pulses affects the image quality in the radial sampling with the half-echo acquisition. To improve image quality, we have developed a signal correction algorithm that detects and eliminates this echo shift during reconstruction by performing a pre-scan within 10 seconds. The results showed that image quality is improved under oblique and/or off-centering conditions that frequently cause image distortion due to hardware error. In conclusion, we have developed a robust ultra-short TE pulse sequence that allows wide latitude in the scan parameters, including oblique and off-centering conditions. (author)

  13. Experimental approach to interaction physics challenges of the shock ignition scheme using short pulse lasers.

    Science.gov (United States)

    Goyon, C; Depierreux, S; Yahia, V; Loisel, G; Baccou, C; Courvoisier, C; Borisenko, N G; Orekhov, A; Rosmej, O; Labaune, C

    2013-12-06

    An experimental program was designed to study the most important issues of laser-plasma interaction physics in the context of the shock ignition scheme. In the new experiments presented in this Letter, a combination of kilojoule and short laser pulses was used to study the laser-plasma coupling at high laser intensities for a large range of electron densities and plasma profiles. We find that the backscatter is dominated by stimulated Brillouin scattering with stimulated Raman scattering staying at a limited level. This is in agreement with past experiments using long pulses but laser intensities limited to 2×10(15)  W/cm2, or short pulses with intensities up to 5×10(16)  W/cm2 as well as with 2D particle-in-cell simulations.

  14. 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...

  15. Allowable propagation of short pulse laser beam in a plasma channel and electromagnetic solitary waves

    International Nuclear Information System (INIS)

    Zhang, Shan; Hong, Xue-Ren; Wang, Hong-Yu; Xie, Bai-Song

    2011-01-01

    Nonparaxial and nonlinear propagation of a short intense laser beam in a parabolic plasma channel is analyzed by means of the variational method and nonlinear dynamics. The beam propagation properties are classified by five kinds of behaviors. In particularly, the electromagnetic solitary wave for finite pulse laser is found beside the other four propagation cases including beam periodically oscillating with defocussing and focusing amplitude, constant spot size, beam catastrophic focusing. It is also found that the laser pulse can be allowed to propagate in the plasma channel only when a certain relation for laser parameters and plasma channel parameters is satisfied. For the solitary wave, it may provide an effective way to obtain ultra-short laser pulse.

  16. 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

  17. Numerical analysis of short-pulse laser interactions with thin metal film

    Directory of Open Access Journals (Sweden)

    E. Majchrzak

    2010-10-01

    Full Text Available Thin metal film subjected to a short-pulse laser heating is considered. The hyperbolic two-temperature model describing the temporal andspatial evolution of the lattice and electrons temperatures is discussed. 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.

  18. Streak camera measurements of laser pulse temporal dispersion in short graded-index optical fibers

    International Nuclear Information System (INIS)

    Lerche, R.A.; Phillips, G.E.

    1981-01-01

    Streak camera measurements were used to determine temporal dispersion in short (5 to 30 meter) graded-index optical fibers. Results show that 50-ps, 1.06-μm and 0.53-μm laser pulses can be propagated without significant dispersion when care is taken to prevent propagation of energy in fiber cladding modes

  19. Features of the mechanoluminescence of thin metal films, excited by short and long laser pulses

    International Nuclear Information System (INIS)

    Banishev, A.F.; Panchenko, V.Ya.; Shishkov, A.V.

    2004-01-01

    The results of the study on the deformation-induced luminescence of the fine grain metal films, originating by the impact of the short (submicrosecond) and long (millisecond) laser pulses, are presented. The supposition os made relative to the luminescence excitation mechanism [ru

  20. Ultra-short laser pulses: review of the 3. physics talks, September 17-18, 1998

    International Nuclear Information System (INIS)

    Lemoine, P.

    1999-01-01

    This book deals with the operation of lasers with ultra-short pulses and with the laser beam-matter interaction. The applications in concern are: the acceleration of particles, the production of X-ray or photon sources, the micro-machining, the fast ignition in thermonuclear fusion, the production of thin films and the surgery of cornea. (J.S.)

  1. 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

  2. Dynamic behavior of HTSC opening switch models controlled by short over-critical current pulses

    International Nuclear Information System (INIS)

    Agafonov, A.V.; Krastelev, E.G.; Voronin, V.S.

    1999-01-01

    We present results of experimental research of dynamical properties of thin films of YBa 2 Cu 3 O 7 HTSC-switch models under action of short overcritical current pulses to test this method of control of fast high-power opening switches for accelerator applications

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

    International Nuclear Information System (INIS)

    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.

    2003-01-01

    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 20 photons/s/0.1% bandwidth/mm 2 /mrad 2 . Initial results are reported and compared to theoretical calculations

  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. Some models of propagation of extremely short electromagnetic pulses in a nonlinear medium

    International Nuclear Information System (INIS)

    Maimistov, Andrei I

    2000-01-01

    Some cases of model media considered in this paper allow analytical solutions to nonlinear wave equations to be found and the time dependence of the electric field strength to be determined in the explicit form for arbitrarily short electromagnetic pulses. Our analysis does not employ any assumptions concerning a harmonic carrier wave or the variation rate of the field in such pulses. The class of models considered includes two-level resonance and quasi-resonance systems. Nonresonance media are analysed in terms of models of anharmonic oscillators - the Duffing and Lorentz models. In most cases, only particular solutions describing the stationary propagation of a video pulse (a unipolar transient of the electric field or a pulse including a small number of oscillations of the electric field around zero) can be found. These solutions correspond to sufficiently strong electromagnetic fields when the dispersion inherent in the medium is suppressed by nonlinear processes. (invited paper)

  6. Multiphoton atomic ionization in the field of a very short laser pulse

    International Nuclear Information System (INIS)

    Popov, V.S.

    2001-01-01

    Closed analytic expressions are derived for the probability of multiphoton atomic and ionic ionization in a variable electric field E(t), which are applicable for arbitrary Keldysh parameters γ. Dependencies of the ionization probability and photoelectron pulse spectrum on the shape of a very short laser pulse are analyzed. Examples of pulse fields of various forms, including a modulated light pulse with a Gaussian or Lorentz envelope, are considered in detail. The interference effect in the photoelectron energy spectrum during atomic ionization by a periodic field of a general form is examined. The range of applicability of the adiabatic approximation in the multiphoton ionization theory is discussed. The imaginary time method is used in the calculations, which allows the probability of particle tunneling through oscillating barriers to be effectively calculated

  7. 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.

  8. 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.

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

    International Nuclear Information System (INIS)

    Teghil, R; De Bonis, A; Galasso, A; Santagata, A; Albano, G; Villani, P; Spera, D; Parisi, G P

    2008-01-01

    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.

  10. MOSFET-based high voltage short pulse generator for ultrasonic transducer excitation

    Science.gov (United States)

    Hidayat, Darmawan; Setianto, Syafei, Nendi Suhendi; Wibawa, Bambang Mukti

    2018-02-01

    This paper presents the generation of a high-voltage short pulse for the excitation of high frequency ultrasonic transducers. This is highly required in the purpose of various ultrasonic-based evaluations, particularly when high resolution measurement is necessary. A high voltage (+760 V) DC voltage source was pulsated by an ultrafast switching MOSFET which was driven by a pulse generator circuit consisting of an astable multivibrator, a one-shot multivibrator with Schmitt trigger input and a high current MOSFET driver. The generated pulses excited a 200-kHz and a 1-MHz ultrasonic transducers and tested in the transmission mode propagation to evaluate the performances of the generated pulse. The test results showed the generator were able to produce negative spike pulses up to -760 V voltage with the shortest time-width of 107.1 nanosecond. The transmission-received ultrasonic waves show frequency oscillation at 200 and 961 kHz and their amplitudes varied with the voltage of excitation pulse. These results conclude that the developed pulse generator is applicable to excite transducer for the generation of high frequency ultrasonic waves.

  11. 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.

  12. Unresolved spectral structures emitted from heavy atom plasmas produced by short pulse laser

    International Nuclear Information System (INIS)

    Fraenkel, M.; Zigler, A.

    1999-01-01

    Spectra of rare earth elements emitted from ultra short pulse laser produced plasma were recorded using simultaneously high and low resolution, spectrometers. A study of the broad band emission of the Δn = 1 transitions in highly ionized Ba and Sm plasma showed that this band is completely unresolved. The spectra were analyzed using the LTE based on super-transition array (STA) model. The theory reconstructs the entire Ba spectrum using a single temperature and density, whereas for Sm the discrepancies between the theory and experiment are not reconcilable. The agreement in the Ba case is attributed to the fact that BaF 2 target is transparent to the laser's prepulse effects, producing a homogeneous dense plasma, whereas for Sm the dilute plasma created by the prepulse is far from LTE. The obtained results posses a significant implication to the applicability of the STA model, in particular for calculations of opacities and conversion of laser light to X-rays. (orig.)

  13. Unresolved spectral structures emitted from heavy atom plasmas produced by short pulse laser

    Energy Technology Data Exchange (ETDEWEB)

    Fraenkel, M.; Zigler, A. [Hebrew Univ., Jerusalem (Israel). Racah Inst. of Physics; Bar-Shalom, A.; Oreg, J. [Israel Atomic Energy Commission, Beersheba (Israel). Nuclear Research Center-Negev; Faenov, A.Ya.; Pikuz, T.A. [Multicharged Ions Spectra Data Center of VNIIFTRI, Russian Committee of Standards Moscow region (Russian Federation)

    1999-09-01

    Spectra of rare earth elements emitted from ultra short pulse laser produced plasma were recorded using simultaneously high and low resolution, spectrometers. A study of the broad band emission of the {delta}n = 1 transitions in highly ionized Ba and Sm plasma showed that this band is completely unresolved. The spectra were analyzed using the LTE based on super-transition array (STA) model. The theory reconstructs the entire Ba spectrum using a single temperature and density, whereas for Sm the discrepancies between the theory and experiment are not reconcilable. The agreement in the Ba case is attributed to the fact that BaF{sub 2} target is transparent to the laser's prepulse effects, producing a homogeneous dense plasma, whereas for Sm the dilute plasma created by the prepulse is far from LTE. The obtained results posses a significant implication to the applicability of the STA model, in particular for calculations of opacities and conversion of laser light to X-rays. (orig.)

  14. 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

  15. Effect of pulse slippage on resonant second harmonic generation of a short pulse laser in a plasma

    International Nuclear Information System (INIS)

    Nitikant; Sharma, A K

    2004-01-01

    The process of second harmonic generation of an intense short pulse laser in a plasma is resonantly enhanced by the application of a magnetic wiggler. The wiggler of suitable wave number k-vector 0 provides necessary momentum to second harmonic photons to make harmonic generation a resonant process. The laser imparts an oscillatory velocity to electrons and exerts a longitudinal ponderomotive force on them at (2ω 1 ,2k-vector 1 ), where ω 1 and k-vector 1 are the frequency and the wave number of the laser, respectively. As the electrons acquire oscillatory velocity at the second harmonic, the wiggler magnetic field beats with it to produce a transverse second harmonic current at (2ω 1 ,2k-vector 1 +k-vector 0 ), driving the second harmonic electromagnetic radiation. However, the group velocity of the second harmonic wave is greater than that of the fundamental wave, hence, the generated pulse slips out of the main laser pulse and its amplitude saturates

  16. Photodetachment of H- by a short laser pulse in crossed static electric and magnetic fields

    International Nuclear Information System (INIS)

    Peng Liangyou; Wang Qiaoling; Starace, Anthony F.

    2006-01-01

    We present a detailed quantum mechanical treatment of the photodetachment of H - by a short laser pulse in the presence of crossed static electric and magnetic fields. An exact analytic formula is presented for the final state electron wave function (describing an electron in both static electric and magnetic fields and a short laser pulse of arbitrary intensity). In the limit of a weak laser pulse, final state electron wave packet motion is examined and related to the closed classical electron orbits in crossed static fields predicted by Peters and Delos [Phys. Rev. A 47, 3020 (1993)]. Owing to these closed orbit trajectories, we show that the detachment probability can be modulated, depending on the time delay between two laser pulses and their relative phase, thereby providing a means to partially control the photodetachment process. In the limit of a long, weak pulse (i.e., a monochromatic radiation field) our results reduce to those of others; however, for this case we analyze the photodetachment cross section numerically over a much larger range of electron kinetic energy (i.e., up to 500 cm -1 ) than in previous studies and relate the detailed structures both analytically and numerically to the above-mentioned, closed classical periodic orbits

  17. Evaluation of temperature history of a spherical nanosystem irradiated with various short-pulse laser sources

    Science.gov (United States)

    Lahiri, Arnab; Mondal, Pranab K.

    2018-04-01

    Spatiotemporal thermal response and characteristics of net entropy production rate of a gold nanosphere (radius: 50-200 nm), subjected to a short-pulse, femtosecond laser is reported. In order to correctly illustrate the temperature history of laser-metal interaction(s) at picoseconds transient with a comprehensive single temperature definition in macroscale and to further understand how the thermophysical response of the single-phase lag (SPL) and dual-phase lag (DPL) frameworks (with various lag-ratios') differs, governing energy equations derived from these benchmark non-Fourier frameworks are numerically solved and thermodynamic assessment under both the classical irreversible thermodynamics (CIT) as well as extended irreversible thermodynamics (EIT) frameworks is subsequently carried out. Under the frameworks of SPL and DPL with small lag ratio, thermophysical anomalies such as temperature overshooting characterized by adverse temperature gradient is observed to violate the local thermodynamic equilibrium (LTE) hypothesis. The EIT framework, however, justifies the compatibility of overshooting of temperature with the second law of thermodynamics under a nonequilibrium paradigm. The DPL framework with higher lag ratio was however observed to remain free from temperature overshooting and finds suitable consistency with LTE hypothesis. In order to solve the dimensional non-Fourier governing energy equation with volumetric laser-irradiation source term(s), the lattice Boltzmann method (LBM) is extended and a three-time level, fully implicit, second order accurate finite difference method (FDM) is illustrated. For all situations under observation, the LBM scheme is featured to be computationally superior to remaining FDM schemes. With detailed prediction of maximum temperature rise and the corresponding peaking time by all the numerical schemes, effects of the change of radius of the gold nanosphere, the magnitude of fluence of laser, and laser irradiation with

  18. Generating high-power short terahertz electromagnetic pulses with a multifoil radiator.

    Science.gov (United States)

    Vinokurov, Nikolay A; Jeong, Young Uk

    2013-02-08

    We describe a multifoil cone radiator capable of generating high-field short terahertz pulses using short electron bunches. Round flat conducting foil plates with successively decreasing radii are stacked, forming a truncated cone with the z axis. The gaps between the foil plates are equal and filled with some dielectric (or vacuum). A short relativistic electron bunch propagates along the z axis. At sufficiently high particle energy, the energy losses and multiple scattering do not change the bunch shape significantly. When passing by each gap between the foil plates, the electron bunch emits some energy into the gap. Then, the radiation pulses propagate radially outward. For transverse electromagnetic waves with a longitudinal (along the z axis) electric field and an azimuthal magnetic field, there is no dispersion in these radial lines; therefore, the radiation pulses conserve their shapes (time dependence). At the outer surface of the cone, we have synchronous circular radiators. Their radiation field forms a conical wave. Ultrashort terahertz pulses with gigawatt-level peak power can be generated with this device.

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

    OpenAIRE

    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.; Lange, D.F. de; Huis in 't Veld, A.J.

    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 advantageous for the processing of thin films. A precise control of the heat affected zone, as small as tens of nanometers, depending on the material and laser conditions, can be achieved. It enab...

  20. 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.

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

    International Nuclear Information System (INIS)

    Chen Hui; Hazi, A. U.; Maren, R. van; Chen, S. N.; Le Pape, S.; Rygg, J. R.; Shepherd, R.; Fuchs, J.; Gauthier, M.

    2010-01-01

    The ultraintense short pulse laser pulses incident on solid targets can generate energetic protons. In addition 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 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 nonimaging magnetic spectrometers. The basic characterizations and sample data from this instrument are presented.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chen Hui; Hazi, A. U.; Maren, R. van; Chen, S. N.; Le Pape, S.; Rygg, J. R.; Shepherd, R. [Lawrence Livermore National Laboratory, Livemore, California 94551 (United States); Fuchs, J.; Gauthier, M. [LULI Ecole Polytechnique, 91128 Palaiseau Cedex (France)

    2010-10-15

    The ultraintense short pulse laser pulses incident on solid targets can generate energetic protons. In addition 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 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 nonimaging magnetic spectrometers. The basic characterizations and sample data from this instrument are presented.

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

    CSIR Research Space (South Africa)

    Ngcobo, S

    2010-09-01

    Full Text Available , Development of High Average Power Picosecond Laser Systems, Opto- Electronic Devices, (2002). INTRODUCTION A Nd:YVO4 modelocked laser has been constructed using a resonator designed according to the theoretical parameters. The laser produced pulses... 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...

  4. Features of single and double ionization processes induced by few cycle laser pulses

    International Nuclear Information System (INIS)

    Starace, A.F.

    2005-01-01

    Full text: The advent of laser pulses with attosecond pulse lengths ushers in the regime of few cycle laser pulse interactions with atoms and ions, including the interesting cases of single and half cycle laser pulses. In this talk I will present results of recent studies of single electron ionization/detachment and double electron ionization/detachment produced by a few cycle laser pulse. For the former case, we shall demonstrate that the ionized/detached electron momentum distribution reflects the interference of electron probability wave packets produced by each half cycle of a single cycle pulse. Also, that the ionized/detached electron momentum distribution uniquely characterizes the phase of the single cycle laser pulse within the laser pulse envelope. Regarding double ionization/detachment, our numerical experiments have shown that single cycle and double half cycle pulses produce different electron angular distributions. Some double ionization features that are present only in the single cycle case can only have been produced by electron impact ionization during rescattering of an initially ionized electron and thus represent a sensitive measure of the rescattering process. Refs. 2 (author)

  5. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    Science.gov (United States)

    Balogh, Emeric; Kovacs, Katalin; Dombi, Peter; Fulop, Jozsef A.; Farkas, Gyozo; Hebling, Janos; Tosa, Valer; Varju, Katalin

    2011-08-01

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  6. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    International Nuclear Information System (INIS)

    Balogh, Emeric; Kovacs, Katalin; Dombi, Peter; Farkas, Gyozo; Fulop, Jozsef A.; Hebling, Janos; Tosa, Valer; Varju, Katalin

    2011-01-01

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  7. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Balogh, Emeric [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged (Hungary); Kovacs, Katalin [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged (Hungary); National Institute for R and D of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania); Dombi, Peter; Farkas, Gyozo [Research Institute for Solid State Physics and Optics, H-1525 Budapest (Hungary); Fulop, Jozsef A.; Hebling, Janos [Department of Experimental Physics, University of Pecs, H-7624 Pecs (Hungary); Tosa, Valer [National Institute for R and D of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania); Varju, Katalin [HAS Research Group on Laser Physics, University of Szeged, H-6701 Szeged (Hungary)

    2011-08-15

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  8. Single- and multi-pulse femtosecond laser ablation of optical filter materials

    International Nuclear Information System (INIS)

    Krueger, J.; Lenzner, M.; Martin, S.; Lenner, M.; Spielmann, C.; Fiedler, A.; Kautek, W.

    2003-01-01

    Ablation experiments employing Ti:sapphire laser pulses with durations from 30 to 340 fs (centre wavelength 800 nm, repetition rate 1 kHz) were performed in air. Absorbing filters (Schott BG18 and BG36) served as targets. The direct focusing technique was used under single- and multi-pulse irradiation conditions. Ablation threshold fluences were determined from a semi-logarithmic plot of the ablation crater diameter versus laser fluence. The threshold fluence decreases for a shorter pulse duration and an increasing number of pulses. The multi-pulse ablation threshold fluences are similar to those of undoped glass material (∼1 J cm -2 ). That means that the multi-pulse ablation threshold is independent on the doping level of the filters. For more than 100 pulses per spot and all pulse durations applied, the threshold fluence is practically constant. This leads to technically relevant ablation threshold values

  9. Examination of vocal fold movement by ultra-short pulse X radiography

    International Nuclear Information System (INIS)

    Noscoe, N.J.; Berry, R.J.; Brown, N.J.

    1983-01-01

    Antero-posterior radiographs of the larynx lack spatial and temporal resolution, due to the movement of the vocal folds during phonation. By utilising the electrolaryngograph to monitor vocal fold movement, single X-ray pulses of 30 nanoseconds duration have been triggered at pre-determined points during the cycle of vocal fold movement to visualise these in normal phonation. (author)

  10. Towards shorter wavelength x-ray lasers using a high power, short pulse pump laser

    International Nuclear Information System (INIS)

    Tighe, W.; Krushelnick, K.; Valeo, E.; Suckewer, S.

    1991-05-01

    A near-terawatt, KrF* laser system, focussable to power densities >10 18 W/cm 2 has been constructed for use as a pump laser in various schemes aimed at the development of x-ray lasing below 5nm. The laser system along with output characteristics such as the pulse duration, the focal spot size, and the percentage of amplified spontaneous emission (ASE) emitted along with the laser pulse will be presented. Schemes intended to lead to shorter wavelength x-ray emission will be described. The resultant requirements on the pump laser characteristics and the target design will be outlined. Results from recent solid target experiments and two-laser experiments, showing the interaction of a high-power, short pulse laser with a preformed plasma, will be presented. 13 refs., 5 figs

  11. A differential optical interferometer for measuring short pulses of surface acoustic waves.

    Science.gov (United States)

    Shaw, Anurupa; Teyssieux, Damien; Laude, Vincent

    2017-09-01

    The measurement of the displacements caused by the propagation of a short pulse of surface acoustic waves on a solid substrate is investigated. A stabilized time-domain differential interferometer is proposed, with the surface acoustic wave (SAW) sample placed outside the interferometer. Experiments are conducted with surface acoustic waves excited by a chirped interdigital transducer on a piezoelectric lithium niobate substrate having an operational bandwidth covering the 200-400MHz frequency range and producing 10-ns pulses with 36nm maximum out-of-plane displacement. The interferometric response is compared with a direct electrical measurement obtained with a receiving wide bandwidth interdigital transducer and good correspondence is observed. The effects of varying the path difference of the interferometer and the measurement position on the surface are discussed. Pulse compression along the chirped interdigital transducer is observed experimentally. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Development of transient collisional excitation x-ray laser with ultra short-pulse laser

    International Nuclear Information System (INIS)

    Kado, Masataka; Kawachi, Tetsuya; Hasegawa, Noboru; Tanaka, Momoko; Sukegawa, Kouta; Nagashima, Keisuke; Kato, Yoshiaki

    2001-01-01

    We have observed lasing on Ne-like 3s-3p line from titanium (32.4 nm), Ni-like 4p-4d line from silver (13.9 nm) and tin (11.9 nm) with the transient collisional excitation (TCE) scheme that uses combination of a long pre-pulse (∼ns) and a short main pulse (∼ps). A gain coefficient of 23 cm -1 was measured for plasma length up to 4 mm with silver slab targets. We have also observed lasing on Ne-like and Ni-like lines with new TCE scheme that used pico-seconds laser pulse to generate plasma and observed strong improvement of x-ray laser gain coefficient. A gain coefficient of 14 cm -1 was measured for plasma length up to 6 mm with tin targets. (author)

  13. Compressing and focusing a short laser pulse by a thin plasma lens

    International Nuclear Information System (INIS)

    Ren, C.; Duda, B. J.; Hemker, R. G.; Mori, W. B.; Katsouleas, T.; Antonsen, T. M.; Mora, P.

    2001-01-01

    We consider the possibility of using a thin plasma slab as an optical element to both focus and compress an intense laser pulse. By thin we mean that the focal length is larger than the lens thickness. We derive analytic formulas for the spot size and pulse length evolution of a short laser pulse propagating through a thin uniform plasma lens. The formulas are compared to simulation results from two types of particle-in-cell code. The simulations give a greater final spot size and a shorter focal length than the analytic formulas. The difference arises from spherical aberrations in the lens which lead to the generation of higher-order vacuum Gaussian modes. The simulations also show that Raman side scattering can develop. A thin lens experiment could provide unequivocal evidence of relativistic self-focusing

  14. Nonlinear interaction of powerful short electromagnetic pulses with an electron plasma

    International Nuclear Information System (INIS)

    Rao, N.N.; Yu, M.Y.; Shukla, P.K.

    1990-01-01

    The nonlinear interaction of powerful short electromagnetic pulses with a plasma consisting of two groups of electrons and immobile ions has been studied. It is shown that the interaction is governed by a nonlinear equation for the electromagnetic wave envelope and a driven nonlinear equation for the low-frequency electron fluctuations. The driver for the latter depends explicitly on the spatio-temporal evolution of the electromagnetic wave flux. It is found that, depending on the cold-to-hot electron density ratio, the localized pulse can propagate with sub- as well as supersonic velocities accompanied by compressional or rarefactional density perturbations. The conditions of existence for the different types of solitary pulses are obtained. The present investigation may be relevant to the study of wave-plasma interaction devices such as inertial fusion confinement as well as to ionospheric modification experiments. (author)

  15. 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.

  16. Measurement and deconvolution of detector response time for short HPM pulses: Part 1, Microwave diodes

    International Nuclear Information System (INIS)

    Bolton, P.R.

    1987-06-01

    A technique is described for measuring and deconvolving response times of microwave diode detection systems in order to generate corrected input signals typical of an infinite detection rate. The method has been applied to cases of 2.86 GHz ultra-short HPM pulse detection where pulse rise time is comparable to that of the detector; whereas, the duration of a few nanoseconds is significantly longer. Results are specified in terms of the enhancement of equivalent deconvolved input voltages for given observed voltages. The convolution integral imposes the constraint of linear detector response to input power levels. This is physically equivalent to the conservation of integrated pulse energy in the deconvolution process. The applicable dynamic range of a microwave diode is therefore limited to a smaller signal region as determined by its calibration

  17. Control of ion beam generation in intense short pulse laser target interaction

    International Nuclear Information System (INIS)

    Nagashima, T.; Izumiyama, T.; Barada, D.; Kawata, S.; Gu, Y.J.; Wang, W.M.; Ma, Y.Y.; Kong, Q.

    2013-01-01

    In intense laser plasma interaction, several issues still remain to be solved for future laser particle acceleration. In this paper we focus on a control of generation of high-energy ions. In this study, near-critical density plasmas are employed and are illuminated by high intensity short laser pulses; we have successfully generated high-energy ions, and also controlled ion energy and the ion energy spectrum by multiple-stages acceleration. We performed particle-in-cell simulations in this paper. The first near-critical plasma target is illuminated by a laser pulse, and the ions accelerated are transferred to the next target. The next identical target is also illuminated by another identical large pulse, and the ion beam introduced is further accelerated and controlled. In this study four stages are employed, and finally a few hundreds of MeV of protons are realized. A quasi-monoenergetic energy spectrum is also obtained. (author)

  18. Digital quantification of rolling circle amplified single DNA molecules in a resistive pulse sensing nanopore.

    Science.gov (United States)

    Kühnemund, M; Nilsson, M

    2015-05-15

    Novel portable, sensitive and selective DNA sensor methods for bio-sensing applications are required that can rival conventionally used non-portable and expensive fluorescence-based sensors. In this paper, rolling circle amplification (RCA) products are detected in solution and on magnetic particles using a resistive pulse sensing (RPS) nanopore. Low amounts of DNA molecules are detected by padlock probes which are circularized in a strictly target dependent ligation reaction. The DNA-padlock probe-complex is captured on magnetic particles by sequence specific capture oligonucleotides and amplified by a short RCA. Subsequent RPS analysis is used to identify individual particles with single attached RCA products from blank particles. This proof of concept opens up for a novel non-fluorescent digital DNA quantification method that can have many applications in bio-sensing and diagnostic approaches. Copyright © 2014 Elsevier B.V. All rights reserved.

  19. Quantum computer based on activated dielectric nanoparticles selectively interacting with short optical pulses

    International Nuclear Information System (INIS)

    Gadomskii, Oleg N; Kharitonov, Yu Ya

    2004-01-01

    The operation principle of a quantum computer is proposed based on a system of dielectric nanoparticles activated with two-level atoms - cubits, in which electric dipole transitions are excited by short intense optical pulses. It is proved that the logical operation (logical operator) CNOT (controlled NOT) is performed by means of time-dependent transfer of quantum information over 'long' (of the order of 10 4 nm) distances between spherical nanoparticles owing to the delayed interaction between them in the optical radiation field. It is shown that one-cubit and two-cubit logical operators required for quantum calculations can be realised by selectively exciting dielectric particles with short optical pulses. (quantum calculations)

  20. 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.

  1. Temporal analysis of reflected optical signals for short pulse laser interaction with nonhomogeneous tissue phantoms

    International Nuclear Information System (INIS)

    Trivedi, Ashish; Basu, Soumyadipta; Mitra, Kunal

    2005-01-01

    The use of short pulse laser for minimally invasive detection scheme has become an indispensable tool in the technological arsenal of modern medicine and biomedical engineering. In this work, a time-resolved technique has been used to detect tumors/inhomogeneities in tissues by measuring transmitted and reflected scattered temporal optical signals when a short pulse laser source is incident on tissue phantoms. A parametric study involving different scattering and absorption coefficients of tissue phantoms and inhomogeneities, size of inhomogeneity as well as the detector position is performed. The experimental measurements are validated with a numerical solution of the transient radiative transport equation obtained by using discrete ordinates method. Thus, both simultaneous experimental and numerical studies are critical for predicting the optical properties of tissues and inhomogeneities from temporal scattered optical signal measurements

  2. Development of a short pulsed corona discharge ionization source for ion mobility spectrometry

    International Nuclear Information System (INIS)

    An Yuan; Aliaga-Rossel, R.; Choi, Peter; Gilles, Jean-Paul

    2005-01-01

    The development of a pulsed corona discharge ionization source and its use in ion mobility spectrometry (IMS) is presented. In a point-plane electrode geometry, an electrical pulse up to 12 kV, 150 ns rise time and 500 ns pulse width was used to generate a corona discharge in air. A single positive high voltage pulse was able to generate about 1.6x10 10 ions at energy consumption of 22 μJ. Since the temporal distribution of ions is in a pulsed form, the possibility of removal the ion gate has been investigated. By purposely arranging the interface between discharge field and drift field, nearly 10 7 positive ions were drawn into the drift region with absence of the ion gate after every single discharge. The positive spectrum of acetone dimer (working at room temperature) was obtained with a resolving power of 20 by using this configuration. The advantages of this new scheme are the low power consumption compared with the dc method as well as the simplicity of the IMS cell structure

  3. Toeless pulse shaping with a single delay-line network

    International Nuclear Information System (INIS)

    Tauhata, L.; Binns, D.C.

    1976-04-01

    New unipolar delay-line clippers producing negligible cancellation remnant have been developed. Near perfect clipping is achieved using a combination of several types of coaxial cable tranformers working as a phase inverter, a new pulse adder, or an impedance transformer. Only passive elements are used in the bridge network. The construction is simple and the performance is extremely stable and wide in dynamic range and frequency band width. Completely symmetrical bipolar pulses are also easily obtained using this technique

  4. Resonant-enhanced above-threshold ionization of atoms by XUV short laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, V.D. [Departamento de Fisica, FCEyN, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina)], E-mail: vladimir@df.uba.ar; Macri, P.A. [Instituto de Investigaciones Fisicas de Mar del Plata (IFIMAR), Departamento de Fisica, FCEyN, Universidad Nacional de Mar del Plata, CONICET, Funes 3350, 7600 Mar del Plata (Argentina); Arbo, D.G. [Instituto de Astronomia y Fisica del Espacio, UBA-CONICET, CC 67 Suc 28 Buenos Aires (Argentina)

    2009-01-15

    Above-threshold ionization of atoms by XUV short laser pulses is investigated close to the resonant 1s-2p transitions. Both ab initio TDSE and a theoretical Coulomb-Volkov like theory are used to study the enhancement in the ionization probabilities. Our modified Coulomb-Volkov theory, fully accounting for the important 1s-2p transition is able to explain the spectrum as well as the total ionization cross sections.

  5. Electron emission from insulator surfaces by ultra-short laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Acuna, M; Gravielle, M S, E-mail: mario@iafe.uba.a, E-mail: msilvia@iafe.uba.a [Institutes de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina)

    2009-11-01

    Photoelectron emission from insulator surfaces induced by ultra-short laser pulses is studied within a time-dependent distorted wave method. The proposed approach combines the Volkov phase, which takes into account the laser interaction, with a simple representation of the unperturbed surface states, given by the Tight-binding method. The model is applied to evaluate the photoelectron emission from a LiF(001) surface, finding effects of interference produced by the crystal lattice.

  6. 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.

  7. 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.

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

    International Nuclear Information System (INIS)

    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

    2015-01-01

    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"1"0 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.

  9. Self-focusing and guiding of short laser pulses in ionizing gases and plasmas

    International Nuclear Information System (INIS)

    Esarey, E.; Sprangle, P.; Krall, J.; Ting, A.

    1997-01-01

    The propagation of intense laser pulses in gases and plasmas is relevant to a wide range of applications, including laser-driven accelerators, laser-plasma channeling, harmonic generation, supercontinuum generation, X-ray lasers, and laser-fusion schemes. Here, several features of intense, short-pulse (≤1 ps) laser propagation in gases undergoing ionization and in plasmas are reviewed, discussed, and analyzed. The wave equations for laser pulse propagation in a gas undergoing ionization and in a plasma are derived. The source-dependent expansion method is discussed, which is a general method for solving the paraxial wave equation with nonlinear source terms. In gases, the propagation of high-power (near the critical power) laser pulses is considered including the effects of diffraction, nonlinear self-focusing, ionization, and plasma generation. Self-guided solutions and the stability of these solutions are discussed. In plasmas, optical guiding by relativistic effects, ponderomotive effects, and preformed density channels is considered. The self-consistent plasma response is discussed, including plasma wave effects and instabilities such as self-modulation. Recent experiments on the guiding of laser pulses in gases and in plasmas are briefly summarized

  10. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Dynamics of splashing of molten metals during irradiation with single CO2 laser pulses

    Science.gov (United States)

    Arutyunyan, R. V.; Baranov, V. Yu; Bol'shov, Leonid A.; Dolgov, V. A.; Malyuta, D. D.; Mezhevov, V. S.; Semak, V. V.

    1988-03-01

    An experimental investigation was made of the dynamics of the loss of the melt as a result of interaction with single-mode CO2 laser radiation pulses of 5-35 μs duration. The dynamics of splashing of the melt during irradiation with short pulses characterized by a Gaussian intensity distribution differed from that predicted by models in which the distribution of the vapor pressure was assumed to be radially homogeneous.

  11. Study on irradiation effects of nucleus electromagnetic pulse on single chip computer system

    International Nuclear Information System (INIS)

    Hou Minsheng; Liu Shanghe; Wang Shuping

    2001-01-01

    Intense electromagnetic pulse, namely nucleus electromagnetic pulse (NEMP), lightning electromagnetic pulse (LEMP) and high power microwave (HPM), can disturb and destroy the single chip computer system. To study this issue, the authors made irradiation experiments by NEMPs generated by gigahertz transversal electromagnetic (GTEM) Cell. The experiments show that shutdown, restarting, communication errors of the single chip microcomputer system would occur when it was irradiated by the NEMPs. Based on the experiments, the cause on the effects on the single chip microcomputer system is discussed

  12. Single pulse analysis of intracranial pressure for a hydrocephalus implant.

    Science.gov (United States)

    Elixmann, I M; Hansinger, J; Goffin, C; Antes, S; Radermacher, K; Leonhardt, S

    2012-01-01

    The intracranial pressure (ICP) waveform contains important diagnostic information. Changes in ICP are associated with changes of the pulse waveform. This change has explicitly been observed in 13 infusion tests by analyzing 100 Hz ICP data. An algorithm is proposed which automatically extracts the pulse waves and categorizes them into predefined patterns. A developed algorithm determined 88 %±8 % (mean ±SD) of all classified pulse waves correctly on predefined patterns. This algorithm has low computational cost and is independent of a pressure drift in the sensor by using only the relationship between special waveform characteristics. Hence, it could be implemented on a microcontroller of a future electromechanic hydrocephalus shunt system to control the drainage of cerebrospinal fluid (CSF).

  13. Soft error rate analysis methodology of multi-Pulse-single-event transients

    International Nuclear Information System (INIS)

    Zhou Bin; Huo Mingxue; Xiao Liyi

    2012-01-01

    As transistor feature size scales down, soft errors in combinational logic because of high-energy particle radiation is gaining more and more concerns. In this paper, a combinational logic soft error analysis methodology considering multi-pulse-single-event transients (MPSETs) and re-convergence with multi transient pulses is proposed. In the proposed approach, the voltage pulse produced at the standard cell output is approximated by a triangle waveform, and characterized by three parameters: pulse width, the transition time of the first edge, and the transition time of the second edge. As for the pulse with the amplitude being smaller than the supply voltage, the edge extension technique is proposed. Moreover, an efficient electrical masking model comprehensively considering transition time, delay, width and amplitude is proposed, and an approach using the transition times of two edges and pulse width to compute the amplitude of pulse is proposed. Finally, our proposed firstly-independently-propagating-secondly-mutually-interacting (FIP-SMI) is used to deal with more practical re-convergence gate with multi transient pulses. As for MPSETs, a random generation model of MPSETs is exploratively proposed. Compared to the estimates obtained using circuit level simulations by HSpice, our proposed soft error rate analysis algorithm has 10% errors in SER estimation with speed up of 300 when the single-pulse-single-event transient (SPSET) is considered. We have also demonstrated the runtime and SER decrease with the increment of P0 using designs from the ISCAS-85 benchmarks. (authors)

  14. A UV pre-ionized dual-wavelength short-pulse high-power CO{sub 2} laser facility for laser particle acceleration research

    Energy Technology Data Exchange (ETDEWEB)

    Ebrahim, N A; Mouris, J F; Davis, R W

    1994-12-01

    In this report we describe the Chalk River dual-wavelength, short-pulse, single-mode, high-power CO{sub 2} laser facility for research in laser particle acceleration and CANDU materials modifications. The facility is designed and built around UV-preionized transversely-excited atmospheric-pressure (TEA) Lumonics CO{sub 2} laser discharge modules. Peak focussed power densities of up to 2 x 10{sup 14} W/cm{sup 2} in 500 ps pulses have been obtained. (author). 10 refs., 9 figs.

  15. Observation of self-pulsing in singly resonant optical second-harmonic generation with competing nonlinearities

    DEFF Research Database (Denmark)

    Bache, Morten; Lodahl, Peter; Mamaev, Alexander V.

    2002-01-01

    We predict and experimentally observe temporal self-pulsing in singly resonant intracavity second-harmonic generation under conditions of simultaneous parametric oscillation. The threshold for self-pulsing as a function of cavity tuning and phase mismatch are found from analysis of a three...

  16. Single-pulse and burst-mode ablation of gold films measured by quartz crystal microbalance

    Science.gov (United States)

    Andrusyak, Oleksiy G.; Bubelnik, Matthew; Mares, Jeremy; McGovern, Theresa; Siders, Craig W.

    2005-02-01

    Femtosecond ablation has several distinct advantages: the threshold energy fluence for the onset of damage and ablation is orders of magnitude less than for traditional nanosecond laser machining, and by virtue of the rapid material removal of approximately an optical penetration depth per pulse, femtosecond machined cuts can be cleaner and more precise than those made with traditional nanosecond or longer pulse lasers. However, in many materials of interest, especially metals, this limits ablation rates to 10-100 nm/pulse. We present the results of using multiple pulse bursts to significantly increase the per-burst ablation rate compared to a single pulse with the same integrated energy, while keeping the peak intensity of each individual pulse below the air ionization limit. Femtosecond ablation with pulses centered at 800-nm having integrated energy of up to 30 mJ per pulse incident upon thin gold films was measured via resonance frequency shifts in a gold-electrode-coated quartz-crystal oscillator. Measurements were performed using Michelson-interferometer-based burst generators, with up to 2 ns pulse separations, as well as pulse shaping by programmable acousto-optic dispersive filter (Dazzler from FastLite) with up to 2 ps pulse separations.

  17. Aurora: A short-pulse multikilojoule KrF inertial fusion laser system

    International Nuclear Information System (INIS)

    Rosocha, L.A.

    1985-01-01

    Aurora is a laser system that serves as an operating technology demonstration prototype for large-scale high-energy KrF laser systems of interest for inertial fusion applications. This system will incorporate the following elements to achieve an end-to-end 248-nm laser fusion concept demonstration: an injection-locked oscillator-amplifier front end; an optical angular multiplexer to produce 96 encoded optical channels each of 5-nsec duration; a chain of four electron-beam-driven KrF laser amplifiers; automated alignment systems for beam alignment; a decoder to provide for pulse compression of some fraction of the total beam train to be delivered to target, and a target chamber to house and diagnose fusion targets. The front end configuration uses a stable resonator master oscillator to drive an injection-locked unstable resonator slave oscillator. An extension of existing technology has been used to develop an electrooptic switchout at 248 nm that produces a 5-nsec pulse from the longer slave oscillator pulse. This short pulse is amplified by a postamplifier. Using these discharge lasers, the front end then delivers at least 250 mJ of KrF laser light output to the optical encoder

  18. Development of the dense plasma focus for short-pulse applications

    Science.gov (United States)

    Bennett, N.; Blasco, M.; Breeding, K.; Constantino, D.; DeYoung, A.; DiPuccio, V.; Friedman, J.; Gall, B.; Gardner, S.; Gatling, J.; Hagen, E. C.; Luttman, A.; Meehan, B. T.; Misch, M.; Molnar, S.; Morgan, G.; O'Brien, R.; Robbins, L.; Rundberg, R.; Sipe, N.; Welch, D. R.; Yuan, V.

    2017-01-01

    The dense plasma focus (DPF) has long been considered a compact source for pulsed neutrons and has traditionally been optimized for the total neutron yield. In this paper, we describe the efforts to optimize the DPF for short-pulse applications by introducing a reentrant cathode at the end of the coaxial plasma gun. The resulting neutron pulse widths are reduced by an average of 21 ±9 % from the traditional long-drift DPF design. Pulse widths and yields achieved from deuterium-tritium fusion at 2 MA are 61.8 ±30.7 ns FWHM and 1.84 ±0.49 ×1012 neutrons per shot. Simulations were conducted concurrently to elucidate the DPF operation and confirm the role of the reentrant cathode. A hybrid fluid-kinetic particle-in-cell modeling capability demonstrates correct sheath velocities, plasma instabilities, and fusion yield rates. Consistent with previous findings that the DPF is dominated by beam-target fusion from superthermal ions, we estimate that the thermonuclear contribution is at the 1% level.

  19. Phonon transport in a curved aluminum thin film due to laser short pulse irradiation

    Science.gov (United States)

    Mansoor, Saad Bin; Yilbas, Bekir Sami

    2018-05-01

    Laser short-pulse heating of a curved aluminum thin film is investigated. The Boltzmann transport equation is incorporated to formulate the heating situation. A Gaussian laser intensity distribution is considered along the film arc and time exponentially decaying of pulse intensity is incorporated in the analysis. The governing equations of energy transport in the electron and lattice sub-systems are coupled through the electron-phonon coupling parameter. To quantify the phonon intensity distribution in the thin film, equivalent equilibrium temperature is introduced, which is associated with the average energy of all phonons around a local point when the phonon energies are redistributed adiabatically to an equilibrium state. It is found the numerical simulations that electron temperature follows similar trend to the spatial distribution of the laser pulse intensity at the film edge. Temporal variation of electron temperature does not follow the laser pulse intensity distribution. The rise of temperature in the electron sub-system is fast while it remains slow in the lattice sub-system.

  20. Extremely short light pulses: generation; diagnostics, and application in attosecond spectroscopy

    International Nuclear Information System (INIS)

    Iakovlev, V.

    2003-06-01

    The scope of the thesis includes the design of chirped mirrors, as well as theoretical investigations in the fields of high-harmonic generation and laser-dressed Auger decay, the unifying aspect being the presence of extremely short light pulses and physical processes taking place on a femtosecond scale. The main results of the research are the following: 1) It was shown that efficient global optimization of chirped mirrors is possible with an adapted version of the memetic algorithm (also known as hybrid genetic algorithm). 2) The analysis of high-harmonic spectra generated by a few-cycle laser pulse can reveal the electric field of the pulse in the vicinity of its envelope peak. The method developed for this purpose can also be regarded as a method to measure the carrier-envelope phase of laser pulses, which is more robust and has a larger range of applicability compared to the simple analysis of the cut-off region of high-harmonic spectra. 3) A quantum theory of time-resolved Auger spectroscopy was developed. Based on the essential states method, closed-form expressions for probability amplitudes were derived. The theory lays the foundation for the interpretation of experiments that probe electronic motion during atomic excitation, deexcitation, and ionization. (author)

  1. Study of the fast inversion recovery pulse sequence. With reference to fast fluid attenuated inversion recovery and fast short TI inversion recovery pulse sequence

    International Nuclear Information System (INIS)

    Tsuchihashi, Toshio; Maki, Toshio; Suzuki, Takeshi

    1997-01-01

    The fast inversion recovery (fast IR) pulse sequence was evaluated. We compared the fast fluid attenuated inversion recovery (fast FLAIR) pulse sequence in which inversion time (TI) was established as equal to the water null point for the purpose of the water-suppressed T 2 -weighted image, with the fast short TI inversion recovery (fast STIR) pulse sequence in which TI was established as equal to the fat null point for purpose of fat suppression. In the fast FLAIR pulse sequence, the water null point was increased by making TR longer. In the FLAIR pulse sequence, the longitudinal magnetization contrast is determined by TI. If TI is increased, T 2 -weighted contrast improves in the same way as increasing TR for the SE pulse sequence. Therefore, images should be taken with long TR and long TI, which are longer than TR and longer than the water null point. On the other hand, the fat null point is not affected by TR in the fast STIR pulse sequence. However, effective TE was affected by variation of the null point. This increased in proportion to the increase in effective TE. Our evaluation indicated that the fast STIR pulse sequence can control the extensive signals from fat in a short time. (author)

  2. A randomised comparative study of the short term clinical and biological effects of intravenous pulse methylprednisolone and infliximab in patients with active rheumatoid arthritis despite methotrexate treatment

    OpenAIRE

    Durez, P; Nzeusseu, T; Lauwerys, B; Manicourt, D; Verschueren, P; Westhovens, R; Devogelaer, J; Houssiau, F

    2004-01-01

    OBJECTIVES: To compare the short term clinical and biological effects of intravenous (i.v.) pulse methylprednisolone (MP) and infliximab (IFX) in patients with severe active rheumatoid arthritis (RA) despite methotrexate (MTX) treatment. METHODS: Patients with active RA despite MTX treatment were randomly allocated to receive a single i.v. infusion of MP (1 g) or three i.v. infusions of IFX (3 mg/kg) on weeks 0, 2, and 6. Patients were "blindly" evaluated for disease activity measures. Qualit...

  3. 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.

  4. Flame Motion In Gas Turbine Burner From Averages Of Single-Pulse Flame Fronts

    Energy Technology Data Exchange (ETDEWEB)

    Tylli, N.; Hubschmid, W.; Inauen, A.; Bombach, R.; Schenker, S.; Guethe, F. [Alstom (Switzerland); Haffner, K. [Alstom (Switzerland)

    2005-03-01

    Thermo acoustic instabilities of a gas turbine burner were investigated by flame front localization from measured OH laser-induced fluorescence single pulse signals. The average position of the flame was obtained from the superposition of the single pulse flame fronts at constant phase of the dominant acoustic oscillation. One observes that the flame position varies periodically with the phase angle of the dominant acoustic oscillation. (author)

  5. Short-pulse CO2-laser damage studies of NaCl and KCl windows

    International Nuclear Information System (INIS)

    Newnam, B.E.; Nowak, A.V.; Gill, D.H.

    1979-01-01

    The damage resistance of bare surfaces and the bulk interior of NaCl and KCl windows was measured with a short-pulse CO 2 laser at 10.6 μm. Parametric studies with 1.7-ns pulses indicated that adsorbed water was probably the limiting agent on surface thresholds in agreement with previous studies at long pulsewidths. Rear-surface thresholds up to 7 J/cm 2 were measured for polished NaCl windows, whereas KCl surfaces damaged at approximately 60% of this level. The breakdown electric-field thresholds of exit surfaces were only 50% of the value of the bulk materials. The pulsewidth dependence of surface damage from 1 to 65 ns, in terms of incident laser fluence, increased as t/sup 1/3/

  6. High power, short pulses ultraviolet laser for the development of a new x-ray laser

    International Nuclear Information System (INIS)

    Meixler, L.; Nam, C.H.; Robinson, J.; Tighe, W.; Krushelnick, K.; Suckewer, S.; Goldhar, J.; Seely, J.; Feldman, U.

    1989-04-01

    A high power, short pulse ultraviolet laser system (Powerful Picosecond-Laser) has been developed at the Princeton Plasma Physics Laboratory (PPPL) as part of experiments designed to generate shorter wavelength x-ray lasers. With the addition of pulse compression and a final KrF amplifier the laser output is expected to have reached 1/3-1/2 TW (10 12 watts) levels. The laser system, particularly the final amplifier, is described along with some initial soft x-ray spectra from laser-target experiments. The front end of the PP-Laser provides an output of 20--30 GW (10 9 watts) and can be focussed to intensities of /approximately/10 16 W/cm 2 . Experiments using this output to examine the effects of a prepulse on laser-target interaction are described. 19 refs., 14 figs

  7. 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.

  8. 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.

  9. Characterization of a high repetition-rate laser-driven short-pulsed neutron source

    Science.gov (United States)

    Hah, J.; Nees, J. A.; Hammig, M. D.; Krushelnick, K.; Thomas, A. G. R.

    2018-05-01

    We demonstrate a repetitive, high flux, short-pulsed laser-driven neutron source using a heavy-water jet target. We measure neutron generation at 1/2 kHz repetition rate using several-mJ pulse energies, yielding a time-averaged neutron flux of 2 × 105 neutrons s‑1 (into 4π steradians). Deuteron spectra are also measured in order to understand source characteristics. Analyses of time-of-flight neutron spectra indicate that two separate populations of neutrons, ‘prompt’ and ‘delayed’, are generated at different locations. Gamma-ray emission from neutron capture 1H(n,γ) is also measured to confirm the neutron flux.

  10. The Israeli EA-FEL Upgrade Towards Long Pulse Operation for Ultra-High Resolution Single Pulse Coherent Spectroscopy

    CERN Document Server

    Gover, A; Kanter, M; Kapilevich, B; Litvak, B; Peleg, S; Socol, Y; Volshonok, M

    2005-01-01

    The Israeli Electrostatic Accelerator FEL (EA-FEL) is now being upgraded towards long pulse (1005s) operation and ultra-high resolution (10(-6)) single pulse coherent spectroscopy. We present quantitative estimations regarding the applications of controlled radiation chirp for spectroscopic applications with pulse-time Fourier Transform limited spectral resolution. Additionally, we describe a novel extraction-efficiency-improving scheme based on increase of accelerating voltage (boosting) after saturation is achieved. The efficiency of the proposed scheme is confirmed by theoretical and numerical calculations. The latter are performed using software, based on 3D space-frequency domain model. The presentation provides an overview of the upgrade status: the high-voltage terminal is being reconfigured to accept the accelerating voltage boost system; a new broad band low-loss resonator is being manufactured; multi-stage depressed collector is assembled.

  11. Cooling the vertical surface by conditionally single pulses

    Directory of Open Access Journals (Sweden)

    Karpov Pavel

    2017-01-01

    Full Text Available You Sprays with periodic supply of the droplet phase have great opportunities to control the heat exchange processes. Varying pulse duration and frequency of their repetition, we can achieve the optimal conditions of evaporative cooling with minimization of the liquid flow rate. The paper presents experimental data on studying local heat transfer on a large subcooled surface, obtained on the original setup with multinozzle controlled system of impact irrigation by the gas-droplet flow. A contribution to intensification of the spray parameters (flow rate, pulse duration, repetition frequency per a growth of integral heat transfer was studied. Data on instantaneous distribution of the heat flux value helped us to describe the processes occurring on the studied surface. These data could describe the regime of “island” film cooling.

  12. Cooling the vertical surface by conditionally single pulses

    Science.gov (United States)

    Karpov, Pavel; Nazarov, Alexander; Serov, Anatoly; Terekhov, Victor

    2017-10-01

    You Sprays with periodic supply of the droplet phase have great opportunities to control the heat exchange processes. Varying pulse duration and frequency of their repetition, we can achieve the optimal conditions of evaporative cooling with minimization of the liquid flow rate. The paper presents experimental data on studying local heat transfer on a large subcooled surface, obtained on the original setup with multinozzle controlled system of impact irrigation by the gas-droplet flow. A contribution to intensification of the spray parameters (flow rate, pulse duration, repetition frequency) per a growth of integral heat transfer was studied. Data on instantaneous distribution of the heat flux value helped us to describe the processes occurring on the studied surface. These data could describe the regime of "island" film cooling.

  13. Dynamical resonance shift and unification of resonances in short-pulse laser-cluster interaction

    Science.gov (United States)

    Mahalik, S. S.; Kundu, M.

    2018-06-01

    Pronounced maximum absorption of laser light irradiating a rare-gas or metal cluster is widely expected during the linear resonance (LR) when Mie-plasma wavelength λM of electrons equals the laser wavelength λ . On the contrary, by performing molecular dynamics (MD) simulations of an argon cluster irradiated by short 5-fs (FWHM) laser pulses it is revealed that, for a given laser pulse energy and a cluster, at each peak intensity there exists a λ —shifted from the expected λM—that corresponds to a unified dynamical LR at which evolution of the cluster happens through very efficient unification of possible resonances in various stages, including (i) the LR in the initial time of plasma creation, (ii) the LR in the Coulomb expanding phase in the later time, and (iii) anharmonic resonance in the marginally overdense regime for a relatively longer pulse duration, leading to maximum laser absorption accompanied by maximum removal of electrons from cluster and also maximum allowed average charge states for the argon cluster. Increasing the laser intensity, the absorption maxima is found to shift to a higher wavelength in the band of λ ≈(1 -1.5 ) λM than permanently staying at the expected λM. A naive rigid sphere model also corroborates the wavelength shift of the absorption peak as found in MD and unequivocally proves that maximum laser absorption in a cluster happens at a shifted λ in the marginally overdense regime of λ ≈(1 -1.5 ) λM instead of λM of LR. The present study is important for guiding an optimal condition laser-cluster interaction experiment in the short-pulse regime.

  14. Broadband excitation by chirped pulses: application to single electron spins in diamond

    International Nuclear Information System (INIS)

    Niemeyer, I; Shim, J H; Zhang, J; Suter, D; Taniguchi, T; Teraji, T; Abe, H; Onoda, S; Yamamoto, T; Ohshima, T; Isoya, J; Jelezko, F

    2013-01-01

    Pulsed excitation of broad spectra requires very high field strengths if monochromatic pulses are used. If the corresponding high power is not available or not desirable, the pulses can be replaced by suitable low-power pulses that distribute the power over a wider bandwidth. As a simple case, we use microwave pulses with a linear frequency chirp. We use these pulses to excite spectra of single nitrogen–vacancy centres in a Ramsey experiment. Compared to the conventional Ramsey experiment, our approach increases the bandwidth by at least an order of magnitude. Compared to the conventional continuous wave-ODMR experiment, the chirped Ramsey experiment does not suffer from power broadening and increases the resolution by at least an order of magnitude. As an additional benefit, the chirped Ramsey spectrum contains not only ‘allowed’ single quantum transitions, but also ‘forbidden’ zero- and double quantum transitions, which can be distinguished from the single quantum transitions by phase-shifting the readout pulse with respect to the excitation pulse or by variation of the external magnetic field strength. (paper)

  15. Optimization And Single-Shot Characterization Of Ultrashort Thz Pulses From A Laser Wakefield Accelerator

    International Nuclear Information System (INIS)

    Plateau, G.R.; Matlis, N.H.; van Tilborg, J.; Geddes, C.G.R.; Toth, Cs.; Schroeder, C.B.; Leemans, W.P.

    2009-01-01

    We present spatiotemporal characterization of μJ-class ultrashort THz pulses generated from a laser wakefield accelerator (LWFA). Accelerated electrons, resulting from the interaction of a high-intensity laser pulse with a plasma, emit high-intensity THz pulses as coherent transition radiation. Such high peak-power THz pulses, suitable for high-field (MV/cm) pump-probe experiments, also provide a non-invasive bunch-length diagnostic and thus feedback for the accelerator. The characterization of the THz pulses includes energy measurement using a Golay cell, 2D sign-resolved electro-optic measurement and single-shot spatiotemporal electric-field distribution retrieval using a new technique, coined temporal electric-field cross-Correlation (TEX). All three techniques corroborate THz pulses of ∼ 5 μJ, with peak fields of 100's of kV/cm and ∼ 0.4 ps rms duration.

  16. Optical π phase shift created with a single-photon pulse.

    Science.gov (United States)

    Tiarks, Daniel; Schmidt, Steffen; Rempe, Gerhard; Dürr, Stephan

    2016-04-01

    A deterministic photon-photon quantum logic gate is a long-standing goal. Building such a gate becomes possible if a light pulse containing only one photon imprints a phase shift of π onto another light field. We experimentally demonstrate the generation of such a π phase shift with a single-photon pulse. A first light pulse containing less than one photon on average is stored in an atomic gas. Rydberg blockade combined with electromagnetically induced transparency creates a phase shift for a second light pulse, which propagates through the medium. We measure the π phase shift of the second pulse when we postselect the data upon the detection of a retrieved photon from the first pulse. This demonstrates a crucial step toward a photon-photon gate and offers a variety of applications in the field of quantum information processing.

  17. Self-phase modulation of a single-cycle THz pulse

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, M. C.

    2013-01-01

    We demonstrate self-phase modulation (SPM) of a single-cycle THz pulse in a semiconductor, using bulk n-GaAs as a model system. The SPM arises from the heating of free electrons in the electric field of the THz pulse. Electron heating leads to an ultrafast reduction of the plasma frequency, which...... results in a strong modification of the THz-range dielectric function of the material. THz SPM is observed directly in the time domain as a characteristic reshaping of single-cycle THz pulse. In the frequency domain, it corresponds to a strong frequency-dependent refractive index nonlinearity of n...

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

    Energy Technology Data Exchange (ETDEWEB)

    Mundus, M., E-mail: markus.mundus@ise.fraunhofer.de; Giesecke, J. A.; Fischer, P.; Hohl-Ebinger, J.; Warta, W. [Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstraße 2, 79110 Freiburg (Germany)

    2015-02-28

    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 (I{sub SC}) 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 I{sub SC} values. We validate the theoretical model by I{sub SC} 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 I{sub SC} 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 I{sub SC} 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 I{sub SC} measurement.

  19. Theory of suppressing avalanche process of carrier in short pulse laser irradiated dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Deng, H. X., E-mail: hxdeng@uestc.edu.cn, E-mail: xtzu@uestc.edu.cn, E-mail: kaisun@umich.edu; Zu, X. T., E-mail: hxdeng@uestc.edu.cn, E-mail: xtzu@uestc.edu.cn, E-mail: kaisun@umich.edu; Xiang, X. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Zheng, W. G.; Yuan, X. D. [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Sun, K., E-mail: hxdeng@uestc.edu.cn, E-mail: xtzu@uestc.edu.cn, E-mail: kaisun@umich.edu [Department of Materials Engineering and Sciences, University of Michigan, 413B Space Research Building, Ann Arbor, Michigan 48109-2143 (United States); Gao, F. [Pacific Northwest National Laboratory, P. O. Box 999, Richland, Washington 99352 (United States)

    2014-05-28

    A theory for controlling avalanche process of carrier during short pulse laser irradiation is proposed. We show that avalanche process of conduction band electrons (CBEs) is determined by the occupation number of phonons in dielectrics. The theory provides a way to suppress avalanche process and a direct judgment for the contribution of avalanche process and photon ionization process to the generation of CBEs. The obtained temperature dependent rate equation shows that the laser induced damage threshold of dielectrics, e.g., fused silica, increase nonlinearly with the decreases of temperature. Present theory predicts a new approach to improve the laser induced damage threshold of dielectrics.

  20. Extremely short pulses via stark modulation of the atomic transition frequencies.

    Science.gov (United States)

    Radeonychev, Y V; Polovinkin, V A; Kocharovskaya, Olga

    2010-10-29

    We propose a universal method to produce extremely short pulses of electromagnetic radiation in various spectral ranges. The essence of the method is a resonant interaction of radiation with atoms under the conditions of adiabatic periodic modulation of atomic transition frequencies by a far-off-resonant control laser field via dynamic Stark shift of the atomic levels and proper adjustment of the control field intensity and frequency, as well as the optical depth of the medium. The potential of the method is illustrated by an example in a hydrogenlike atomic system.

  1. Spectral phase encoding of ultra-short optical pulse in time domain for OCDMA application.

    Science.gov (United States)

    Wang, Xu; Wada, Naoya

    2007-06-11

    We propose a novel reconfigurable time domain spectral phase encoding (SPE) scheme for coherent optical code-division-multiple-access application. In the proposed scheme, the ultra-short optical pulse is stretched by dispersive device and the SPE is done in time domain using high speed phase modulator. The time domain SPE scheme is robust to wavelength drift of the light source and is very flexible and compatible with the fiber optical system. Proof-of-principle experiments of encoding with 16-chip, 20 GHz/chip binary-phase-shift-keying codes and 1.25 Gbps data transmission have been successfully demonstrated together with an arrayed-wave-guide decoder.

  2. Meterwavelength Single-pulse Polarimetric Emission Survey. III. The Phenomenon of Nulling in Pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Basu, Rahul; Mitra, Dipanjan; Melikidze, George I., E-mail: rahulbasu.astro@gmail.com [Janusz Gil Institute of Astronomy, University of Zielona Góra, ul. Szafrana 2, 65–516 Zielona Góra (Poland)

    2017-09-10

    A detailed analysis of nulling was conducted for the pulsars studied in the Meterwavelength Single-pulse Polarimetric Emission Survey. We characterized nulling in 36 pulsars including 17 pulsars where the phenomenon was reported for the first time. The most dominant nulls lasted for a short duration, less than five periods. Longer duration nulls extending to hundreds of periods were also seen in some cases. A careful analysis showed the presence of periodicities in the transition from the null to the burst states in 11 pulsars. In our earlier work, fluctuation spectrum analysis showed multiple periodicities in 6 of these 11 pulsars. We demonstrate that the longer periodicity in each case was associated with nulling. The shorter periodicities usually originate from subpulse drifting. The nulling periodicities were more aligned with the periodic amplitude modulation, indicating a possible common origin for both. The most prevalent nulls last for a single period and can be potentially explained using random variations affecting the plasma processes in the pulsar magnetosphere. On the other hand, longer-duration nulls require changes in the pair-production processes, which need an external triggering mechanism for the changes. The presence of periodic nulling puts an added constraint on the triggering mechanism, which also needs to be periodic.

  3. Study of the oncogenic expression in human fibroblast cells after exposure to very short pulsed laser radiations

    International Nuclear Information System (INIS)

    Dormont, D.; Freville, Th.; Raoul, H.; Courant, D.; Court, L.

    1992-01-01

    The aim of this study is to evaluate the capacity of a laser, delivering very short pulses in the near infrared spectrum with a high pulse ratio frequency, to induce genetic modification on biological tissues. The absence of dicentric among chromosomal aberrations on human lymphocytes suggests that a repetitive very short pulses irradiation has a relatively low capacity to induce genetic abnormalities. The studies of the radiation effects on the cellular growth and the oncogenic expression show that the modifications, induced at the cellular level, do not seem the origin of a cellular transformation and a possible mechanism of carcinogenesis. (author)

  4. SINGLE-PULSE RADIO OBSERVATIONS OF THE GALACTIC CENTER MAGNETAR PSR J1745–2900

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Zhen; Shen, Zhi-Qiang; Wu, Ya-Jun; Zhao, Rong-Bing; Fan, Qing-Yuan; Hong, Xiao-Yu; Jiang, Dong-Rong; Li, Bin; Liang, Shi-Guang; Ling, Quan-Bao; Liu, Qing-Hui; Qian, Zhi-Han; Zhang, Xiu-Zhong; Zhong, Wei-Ye; Ye, Shu-Hua [Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China); Wu, Xin-Ji [Department of Astronomy, Peking University, Beijing 100871 (China); Manchester, R. N. [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia); Weltevrede, P. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Yuan, Jian-Ping [Key Laboratory of Radio Astronomy, Chinese Academy of Sciences (China); Lee, Ke-Jia, E-mail: yanzhen@shao.ac.cn [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)

    2015-11-20

    In this paper, we report radio observations of the Galactic Center magnetar PSR J1745–2900 at six epochs between 2014 June and October. These observations were carried out using the new Shanghai Tian Ma Radio Telescope at a frequency of 8.6 GHz. Both the flux density and integrated profile of PSR J1745–2900 show dramatic changes from epoch to epoch, showing that the pulsar was in its “erratic” phase. On MJD 56836, the flux density of this magnetar was about 8.7 mJy, which was 10 times larger than that reported at the time of discovery, enabling a single-pulse analysis. The emission is dominated by narrow “spiky” pulses that follow a log-normal distribution in peak flux density. From 1913 pulses, we detected 53 pulses whose peak flux densities are 10 times greater than that of the integrated profile. They are concentrated in pulse phase at the peaks of the integrated profile. The pulse widths at the 50% level of these bright pulses were between 0.°2 and 0.°9, much narrower than that of the integrated profile (∼12°). The observed pulse widths may be limited by interstellar scattering. No clear correlation was found between the widths and peak flux density of these pulses and no evidence was found for subpulse drifting. Relatively strong spiky pulses are also detected in the other five epochs of observation, showing the same properties as those detected in MJD 56836. These strong spiky pulses cannot be classified as “giant” pulses but are more closely related to normal pulse emission.

  5. Physics and technology of tunable pulsed single longitudinal mode ...

    Indian Academy of Sciences (India)

    Design and technology demonstration of compact, narrow bandwidth, high repetition rate, tunable SLM dye lasers in two different configurations, namely Littrow and grazing incidence grating (GIG), were carried out in our lab at BARC, India. The single longitudinal mode (SLM) dye laser generates single-mode laser beams ...

  6. Atomistic simulations of ultra-short pulse laser ablation of aluminum: validity of the Lambert-Beer law

    Science.gov (United States)

    Eisfeld, Eugen; Roth, Johannes

    2018-05-01

    Based on hybrid molecular dynamics/two-temperature simulations, we study the validity of the application of Lambert-Beer's law, which is conveniently used in various modeling approaches of ultra-short pulse laser ablation of metals. The method is compared to a more rigorous treatment, which involves solving the Helmholtz wave equation for different pulse durations ranging from 100 fs to 5 ps and a wavelength of 800 nm. Our simulations show a growing agreement with increasing pulse durations, and we provide appropriate optical parameters for all investigated pulse durations.

  7. Time-resolved measurement of the quantum states of photons using two-photon interference with short-time reference pulses

    International Nuclear Information System (INIS)

    Ren Changliang; Hofmann, Holger F.

    2011-01-01

    To fully utilize the energy-time degree of freedom of photons for optical quantum-information processes, it is necessary to control and characterize the temporal quantum states of the photons at extremely short time scales. For measurements of the temporal coherence of the quantum states beyond the time resolution of available detectors, two-photon interference with a photon in a short-time reference pulse may be a viable alternative. In this paper, we derive the temporal measurement operators for the bunching statistics of a single-photon input state with a photon from a weak coherent reference pulse. It is shown that the effects of the pulse shape of the reference pulse can be expressed in terms of a spectral filter selecting the bandwidth within which the measurement can be treated as an ideal projection on eigenstates of time. For full quantum tomography, temporal coherence can be determined by using superpositions of reference pulses at two different times. Moreover, energy-time entanglement can be evaluated based on the two-by-two entanglement observed in the coherences between pairs of detection times.

  8. Resonant third-harmonic generation of a short-pulse laser from electron-hole plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Kant, Niti [Department of Physics, Lovely Professional University, Phagwara, Punjab 144 402 (India); Nandan Gupta, Devki [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India); Suk, Hyyong [Advanced Photonics Research Institute (APRI) and Graduate Program of Photonics and Applied Physics, Gwangju Institute of Science and Technology, Gwangju 500 712 (Korea, Republic of)

    2012-01-15

    In semiconductors, free carriers are created in pairs in inter-band transitions and consist of an electron and its corresponding hole. At very high carrier densities, carrier-carrier collisions dominate over carrier-lattice collisions and carriers begin to behave collectively to form plasma. Here, we apply a short-pulse laser to generate third-harmonic radiation from a semiconductor plasma (electron-hole plasma) in the presence of a transverse wiggler magnetic-field. The process of third-harmonic generation of an intense short-pulse laser is resonantly enhanced by the magnetic wiggler, i.e., wiggler magnetic field provides the necessary momentum to third-harmonic photons. In addition, a high-power laser radiation, propagating through a semiconductor imparts an oscillatory velocity to the electrons and exerts a ponderomotive force on electrons at the third-harmonic frequency of the laser. This oscillatory velocity produces a third-harmonic longitudinal current. And due to the beating of the longitudinal electron velocity and the wiggler magnetic field, a transverse third-harmonic current is produced that drives third-harmonic electromagnetic radiation. It is finally observed that for a specific wiggler wave number value, the phase-matching conditions for the process are satisfied, leading to resonant enhancement in the energy conversion efficiency.

  9. Resonant third-harmonic generation of a short-pulse laser from electron-hole plasmas

    International Nuclear Information System (INIS)

    Kant, Niti; Nandan Gupta, Devki; Suk, Hyyong

    2012-01-01

    In semiconductors, free carriers are created in pairs in inter-band transitions and consist of an electron and its corresponding hole. At very high carrier densities, carrier-carrier collisions dominate over carrier-lattice collisions and carriers begin to behave collectively to form plasma. Here, we apply a short-pulse laser to generate third-harmonic radiation from a semiconductor plasma (electron-hole plasma) in the presence of a transverse wiggler magnetic-field. The process of third-harmonic generation of an intense short-pulse laser is resonantly enhanced by the magnetic wiggler, i.e., wiggler magnetic field provides the necessary momentum to third-harmonic photons. In addition, a high-power laser radiation, propagating through a semiconductor imparts an oscillatory velocity to the electrons and exerts a ponderomotive force on electrons at the third-harmonic frequency of the laser. This oscillatory velocity produces a third-harmonic longitudinal current. And due to the beating of the longitudinal electron velocity and the wiggler magnetic field, a transverse third-harmonic current is produced that drives third-harmonic electromagnetic radiation. It is finally observed that for a specific wiggler wave number value, the phase-matching conditions for the process are satisfied, leading to resonant enhancement in the energy conversion efficiency.

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

    International Nuclear Information System (INIS)

    Giri, Ashutosh; Hopkins, Patrick E.

    2015-01-01

    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

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

    International Nuclear Information System (INIS)

    Zhigilei, Leonid V.; Ivanov, Dmitriy S.

    2005-01-01

    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

  12. Efficient amplitude-modulated pulses for triple- to single-quantum coherence conversion in MQMAS NMR.

    Science.gov (United States)

    Colaux, Henri; Dawson, Daniel M; Ashbrook, Sharon E

    2014-08-07

    The conversion between multiple- and single-quantum coherences is integral to many nuclear magnetic resonance (NMR) experiments of quadrupolar nuclei. This conversion is relatively inefficient when effected by a single pulse, and many composite pulse schemes have been developed to improve this efficiency. To provide the maximum improvement, such schemes typically require time-consuming experimental optimization. Here, we demonstrate an approach for generating amplitude-modulated pulses to enhance the efficiency of the triple- to single-quantum conversion. The optimization is performed using the SIMPSON and MATLAB packages and results in efficient pulses that can be used without experimental reoptimisation. Most significant signal enhancements are obtained when good estimates of the inherent radio-frequency nutation rate and the magnitude of the quadrupolar coupling are used as input to the optimization, but the pulses appear robust to reasonable variations in either parameter, producing significant enhancements compared to a single-pulse conversion, and also comparable or improved efficiency over other commonly used approaches. In all cases, the ease of implementation of our method is advantageous, particularly for cases with low sensitivity, where the improvement is most needed (e.g., low gyromagnetic ratio or high quadrupolar coupling). Our approach offers the potential to routinely improve the sensitivity of high-resolution NMR spectra of nuclei and systems that would, perhaps, otherwise be deemed "too challenging".

  13. Technical advantages of disk laser technology in short and ultrashort pulse processes

    Science.gov (United States)

    Graham, P.; Stollhof, J.; Weiler, S.; Massa, S.; Faisst, B.; Denney, P.; Gounaris, E.

    2011-03-01

    This paper demonstrates that disk-laser technology introduces advantages that increase efficiency and allows for high productivity in micro-processing in both the nanosecond (ns) and picosecond (ps) regimes. Some technical advantages of disk technology include not requiring good pump beam quality or special wavelengths for pumping of the disk, high optical efficiencies, no thermal lensing effects and a possible scaling of output power without an increase of pump beam quality. With cavity-dumping, the pulse duration of the disk laser can be specified between 30 and hundreds of nanoseconds, but is independent of frequency, thus maintaining process stability. TRUMPF uses this technology in the 750 watts average power laser TruMicro 7050. High intensity, along with fluency, is important for high ablation rates in thinfilm removal. Thus, these ns lasers show high removal rates, above 60 cm2/s, in thin-film solar cell production. In addition, recent results in paint-stripping of aerospace material prove the green credentials and high processing rates inherent with this technology as it can potentially replace toxic chemical processes. The ps disk technology meanwhile is used in, for example, scribing of solar cells, wafer dicing and drilling injector nozzles, as the pulse duration is short enough to minimize heat input in the laser-matter interaction. In the TruMicro Series 5000, the multi-pass regenerative amplifier stage combines high optical-optical efficiencies together with excellent output beam quality for pulse durations of only 6 ps and high pulse energies of up to 0.25 mJ.

  14. Millijoule Pulse Energy Second Harmonic Generation With Single-Stage Photonic Bandgap Rod Fiber Laser

    DEFF Research Database (Denmark)

    Laurila, Marko; Saby, Julien; Alkeskjold, Thomas Tanggaard

    2011-01-01

    In this paper, we demonstrate, for the first time, a single-stage Q-switched single-mode (SM) ytterbium-doped rod fiber laser delivering record breaking pulse energies at visible and UV light. We use a photonic bandgap rod fiber with a mode field diameter of 59μm based on a new distributed...

  15. Magnetic phases in Pt/Co/Pt films induced by single and multiple femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Kisielewski, J., E-mail: jankis@uwb.edu.pl; Kurant, Z.; Sveklo, I.; Tekielak, M.; Maziewski, A. [Faculty of Physics, University of Białystok, Ciołkowskiego 1L, 15-245 Białystok (Poland); Wawro, A. [Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw (Poland)

    2016-05-21

    Ultrathin Pt/Co/Pt trilayers with initial in-plane magnetization were irradiated with femtosecond laser pulses. In this way, an irreversible structural modification was introduced, which resulted in the creation of numerous pulse fluence-dependent magnetic phases. This was particularly true with the out-of-plane magnetization state, which exhibited a submicrometer domain structure. This effect was studied in a broad range of pulse fluences up to the point of ablation of the metallic films. In addition to this single-pulse experiment, multiple exposure spots were also investigated, which exhibited an extended area of out-of-plane magnetization phases and a decreased damage threshold. Using a double exposure with partially overlapped spots, a two-dimensional diagram of the magnetic phases as a function of the two energy densities was built, which showed a strong inequality between the first and second incoming pulses.

  16. Magnetic phases in Pt/Co/Pt films induced by single and multiple femtosecond laser pulses

    International Nuclear Information System (INIS)

    Kisielewski, J.; Kurant, Z.; Sveklo, I.; Tekielak, M.; Maziewski, A.; Wawro, A.

    2016-01-01

    Ultrathin Pt/Co/Pt trilayers with initial in-plane magnetization were irradiated with femtosecond laser pulses. In this way, an irreversible structural modification was introduced, which resulted in the creation of numerous pulse fluence-dependent magnetic phases. This was particularly true with the out-of-plane magnetization state, which exhibited a submicrometer domain structure. This effect was studied in a broad range of pulse fluences up to the point of ablation of the metallic films. In addition to this single-pulse experiment, multiple exposure spots were also investigated, which exhibited an extended area of out-of-plane magnetization phases and a decreased damage threshold. Using a double exposure with partially overlapped spots, a two-dimensional diagram of the magnetic phases as a function of the two energy densities was built, which showed a strong inequality between the first and second incoming pulses.

  17. Method for single-shot measurement of picosecond laser pulse-lengths without electronic time dispersion

    International Nuclear Information System (INIS)

    Kyrala, G.A.

    1987-01-01

    A two-source shear pattern recording is proposed as a method for single-shot measurement of the pulse shape from nearly monochromatic sources whose pulse lengths are shorter than their coherence times. The basis of this method relies on the assertion that if two identical electromagnetic pulses are recombined with a time delay greater than the sum of their pulse widths, the recordable spatial pattern has no fringes in it. At an arbitrary delay, translated into an actual spatial recording position, the recorded modulated intensity will sample the corresponding laser intensity at that delay time, but with a modulation due to the coherence function of the electromagnetic pulse. Two arrangements are proposed for recording the pattern. The principles, the design parameters, and the methodologies of these arrangements are presented. Resolutions of the configurations and their limitations are given as well

  18. Single-chip pulse programmer for magnetic resonance imaging using a 32-bit microcontroller.

    Science.gov (United States)

    Handa, Shinya; Domalain, Thierry; Kose, Katsumi

    2007-08-01

    A magnetic resonance imaging (MRI) pulse programmer has been developed using a single-chip microcontroller (ADmicroC7026). The microcontroller includes all the components required for the MRI pulse programmer: a 32-bit RISC CPU core, 62 kbytes of flash memory, 8 kbytes of SRAM, two 32-bit timers, four 12-bit DA converters, and 40 bits of general purpose I/O. An evaluation board for the microcontroller was connected to a host personal computer (PC), an MRI transceiver, and a gradient driver using interface circuitry. Target (embedded) and host PC programs were developed to enable MRI pulse sequence generation by the microcontroller. The pulse programmer achieved a (nominal) time resolution of approximately 100 ns and a minimum time delay between successive events of approximately 9 micros. Imaging experiments using the pulse programmer demonstrated the effectiveness of our approach.

  19. A pulsed single-frequency Nd:GGG/BaWO4 Raman laser

    Science.gov (United States)

    Liu, Zhaojun; Men, Shaojie; Cong, Zhenhua; Qin, Zengguang; Zhang, Xingyu; Zhang, Huaijin

    2018-04-01

    A single-frequency pulsed laser at 1178.3 nm was demonstrated in a crystalline Raman laser. A crystal combination of Nd:GGG and BaWO4 was selected to realize Raman conversion from a 1062.5 nm fundamental wave to a 1178.3 nm Stokes wave. An entangled cavity was specially designed to form an intracavity Raman configuration. Single-longitudinal-mode operation was realized by introducing two Fabry-Perot etalons into the Raman laser cavity. This laser operated at a pulse repetition rate of 50 Hz with 2 ms long envelopes containing micro pulses at a 30 kHz repetition rate. The highest output power was 41 mW with the micro pulse duration of 15 ns. The linewidth was measured to be less than 130 MHz.

  20. Dielectric breakdown and healing of anodic oxide films on aluminium under single pulse anodizing

    International Nuclear Information System (INIS)

    Sah, Santosh Prasad; Tatsuno, Yasuhiro; Aoki, Yoshitaka; Habazaki, Hiroki

    2011-01-01

    Research highlights: → We examined dielectric breakdown of anodic alumina by single pulse anodizing. → Current transients and morphology of discharge channels are dependent upon electrolyte and voltage. → There is a good correlation between current transient and morphology of discharge channel. → Healing of open discharge pores occurs in alkaline silicate, but not in pentaborate electrolyte. - Abstract: Single pulse anodizing of aluminium micro-electrode has been employed to study the behaviour of dielectric breakdown and subsequent oxide formation on aluminium in alkaline silicate and pentaborate electrolytes. Current transients during applying pulse voltage have been measured, and surface has been observed by scanning electron microscopy. Two types of current transients are observed, depending on the electrolyte and applied voltage. There is a good correlation between the current transient behaviour and the shape of discharge channels. In alkaline silicate electrolyte, circular open pores are healed by increasing the pulse width, but such healing is not obvious in pentaborate electrolyte.

  1. 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.

  2. Instant recording of the duration of a single mode-locked Nd:YAG laser pulse

    International Nuclear Information System (INIS)

    Lompre, L.A.; Mainfray, G.; Thebault, J.

    1975-01-01

    An electro-optic streak camera incorporating a storage memory video system has been developed and used to instantly visualize and record the shape of a 1.06-μ-wavelength pulse generated by a mode-locked Nd:YAG laser. The duration of a single laser pulse (approximately 30 psec) has been directly measured with and without laser amplification. (U.S.)

  3. Output pulse-shapes of position-sensitive proportional counters using high resistance single wire

    International Nuclear Information System (INIS)

    Iwatani, Kazuo; Nishiyama, Fumitaka; Hasai, Hiromi

    1980-01-01

    The measurements and model analysis of the output pulse-shapes from a single wire proportional counter (SWPC) which has a high resistance anode are described. The characteristics of the observed pulse-shapes are determined by only one parameter which is a function of anode resistance and load resistance and they are reproduced by a simple model. Using this model, the methods for position read-out are discussed in a systematical way. (author)

  4. A Single-Chip CMOS Pulse Oximeter with On-Chip Lock-In Detection

    OpenAIRE

    Diwei He; Stephen P. Morgan; Dimitrios Trachanis; Jan van Hese; Dimitris Drogoudis; Franco Fummi; Francesco Stefanni; Valerio Guarnieri; Barrie R. Hayes-Gill

    2015-01-01

    Pulse oximetry is a noninvasive and continuous method for monitoring the blood oxygen saturation level. This paper presents the design and testing of a single-chip pulse oximeter fabricated in a 0.35 ?m CMOS process. The chip includes photodiode, transimpedance amplifier, analogue band-pass filters, analogue-to-digital converters, digital signal processor and LED timing control. The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the...

  5. Control quantum evolution speed of a single dephasing qubit for arbitrary initial states via periodic dynamical decoupling pulses.

    Science.gov (United States)

    Song, Ya-Ju; Tan, Qing-Shou; Kuang, Le-Man

    2017-03-08

    We investigate the possibility to control quantum evolution speed of a single dephasing qubit for arbitrary initial states by the use of periodic dynamical decoupling (PDD) pulses. It is indicated that the quantum speed limit time (QSLT) is determined by initial and final quantum coherence of the qubit, as well as the non-Markovianity of the system under consideration during the evolution when the qubit is subjected to a zero-temperature Ohmic-like dephasing reservoir. It is shown that final quantum coherence of the qubit and the non-Markovianity of the system can be modulated by PDD pulses. Our results show that for arbitrary initial states of the dephasing qubit with non-vanishing quantum coherence, PDD pulses can be used to induce potential acceleration of the quantum evolution in the short-time regime, while PDD pulses can lead to potential speedup and slow down in the long-time regime. We demonstrate that the effect of PDD on the QSLT for the Ohmic or sub-Ohmic spectrum (Markovian reservoir) is much different from that for the super-Ohmic spectrum (non-Markovian reservoir).

  6. Measurement of flow fluctuations in single longitudinal mode pulsed ...

    Indian Academy of Sciences (India)

    2014-02-12

    Feb 12, 2014 ... Page 1 ... Keywords. Dye lasers; single longitudinal mode; flow fluctuations. PACS Nos 42.55.Mv; 42.60.Mi; 42.60.By. 1. Introduction. Narrow-band dye lasers offer ... stabilized tunable laser source plays an important role for many applications as mentioned above [1]. For tight wavelength control, the ...

  7. Physics and technology of tunable pulsed single longitudinal mode ...

    Indian Academy of Sciences (India)

    precious materials. In particular, single-longitudinal mode dye lasers are useful ... to the longitudinal mode spacing of 10 GHz. Grating of 3300 .... the band of wavelength covering 3 pm and SLM operation was shown in the band of 0.5 pm.

  8. Integrated single grating compressor for variable pulse front tilt in simultaneously spatially and temporally focused systems.

    Science.gov (United States)

    Block, Erica; Thomas, Jens; Durfee, Charles; Squier, Jeff

    2014-12-15

    A Ti:Al(3)O(2) multipass chirped pulse amplification system is outfitted with a single-grating, simultaneous spatial and temporal focusing (SSTF) compressor platform. For the first time, this novel design has the ability to easily vary the beam aspect ratio of an SSTF beam, and thus the degree of pulse-front tilt at focus, while maintaining a net zero-dispersion system. Accessible variation of pulse front tilt gives full spatiotemporal control over the intensity distribution at the focus and could lead to better understanding of effects such as nonreciprocal writing and SSTF-material interactions.

  9. Modelling of Ne-like copper X-ray laser driven by 1.2 ps short pulse and 280 ps background pulse configuration

    International Nuclear Information System (INIS)

    Demir, A.; Kenar, N.; Goktas, H.; Tallents, G.J.

    2004-01-01

    Detailed simulations of Ne-like Cu x-ray laser are undertaken using the EHYBRID code. The atomic physics data are obtained using the Cowan code. The optimization calculations are performed in terms of the intensity of background and the time separation between the background and the short pulse. The optimum value is obtained for the conditions of a Nd:glass laser with 1.2 ps pulse at 4.4 x 10 15 W cm -2 irradiance pumping a plasma pre-formed by a 280 ps duration pulse at 5.4 x 10 12 W cm -2 with peak-to-peak pulse separation set at 300 ps. X-ray resonance lines between 6 A and 15 A emitted from copper plasmas have been simulated. Free-free and free-bound emission from the Si-, Al-, Mg-, Na-, Ne- and F-like ions is calculated in the simulation. (author)

  10. Role of third-order dispersion in chirped Airy pulse propagation in single-mode fibers

    Science.gov (United States)

    Cai, Wangyang; Wang, Lei; Wen, Shuangchun

    2018-04-01

    The dynamic propagation of the initial chirped Airy pulse in single-mode fibers is studied numerically, special attention being paid to the role of the third-order dispersion (TOD). It is shown that for the positive TOD, the Airy pulse experiences inversion irrespective of the sign of initial chirp. The role of TOD in the dynamic propagation of the initial chirped Airy pulse depends on the combined sign of the group-velocity dispersion (GVD) and the initial chirp. If the GVD and chirp have the opposite signs, the chirped Airy pulse compresses first and passes through a breakdown area, then reconstructs a new Airy pattern with opposite acceleration, with the breakdown area becoming small and the main peak of the new Airy pattern becoming asymmetric with an oscillatory structure due to the positive TOD. If the GVD and chirp have the same signs, the finite-energy Airy pulse compresses to a focal point and then inverses its acceleration, in the case of positive TOD, the distance to the focal point becoming smaller. At zero-dispersion point, the finite-energy Airy pulse inverses to the opposite acceleration at a focal point, with the tight-focusing effect being reduced by initial chirp. Under the effect of negative TOD, the initial chirped Airy pulse disperses and the lobes split. In addition, in the anomalous dispersion region, for strong nonlinearity, the initial chirped Airy pulse splits and enters a soliton shedding regime.

  11. Single channel analog pulse processor Asic for gas proportional counters and SI detector

    International Nuclear Information System (INIS)

    Chandratre, V.B.; Sarkar, Soumen; Kataria, S.K.; Viyogi, Y.P.

    2005-01-01

    The paper presents the design and development of a single channel pulse processor in short Singleplex ASIC targeted for gas proportional counters/Si detectors. The design is optimized for the dynamic range of +500 fC to -500 fC with provision for externally adjusted pole-zero cancellation. A dedicated filter based on the de-convolution principle is used for the cancellation of the long hyperbolic signal tail produced by the slow drift of ions, typical in gas proportional with the filter time constants derived from the actual detector input signal shape. The pole-zero adjustment can be done by external dc voltage to achieve perfect base-line recovery to 1% after 5 μs. The simulated 0 pf noise is 500 e - rms for the peaking time of 1.2 μs with noise slope of 7e - -. The gain is 3.4 mv/fC over the entire linear dynamic range with power dissipation of 13 mW. This design is a modified version of Indiplex chip with features dynamic range equal gain on both polarities with nearly same noise and serves as diagnostic chip for Indiplex. The chip can be used for radiation monitoring instruments. (author)

  12. SCREAMER: a single-line pulsed-power design tool

    International Nuclear Information System (INIS)

    Kiefer, M.L.; Widner, M.M.

    1985-01-01

    SCREAMER is a special purpose circuit code developed as a design tool for single module accelerators. It is fast, accurate, flexible, and user-friendly. Its development was motivated by the excessive costs and long turn-around times incurred when using the SCEPTRE circuit analysis code to perform simulations of circuits with large numbers of nodes and with nonlinear components. Comparable simulations between SCREAMER running on a VAX 11/780 and SCEPTRE running on a CRAY-1S show that turn-around times and costs can be two orders of magnitude lower when using SCREAMER

  13. SCREAMER - A single-line pulsed-power design tool

    International Nuclear Information System (INIS)

    Kiefer, M.L.; Widner, M.M.

    1985-01-01

    SCREAMER is a special purpose circuit code developed as a design tool for single module accelerators. it is fast, accurate, flexible, and user-friendly. Its development was motivated by the excessive costs and long turn-around times incurred when using the SCEPTRE circuit analysis code to perform simulations of circuits with large numbers of modes and with nonlinear components. Comparable simulations between SCREAMER running on a VAX 11/780 and SCEPTRE running on a CRAY-1S show that turn-around times and costs can be two orders of magnitude lower when using SCREAMER

  14. 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.

  15. Erosion of CFC, pyrolytic and boronated graphite under short pulsed laser irradiation

    International Nuclear Information System (INIS)

    Kraaij, G.J.; Bakker, J.; Stad, R.C.L. van der

    1992-07-01

    The effect of short pulsed laser irradiation of '0/3' ms and up to 10 MJ/m 2 on different types of carbon base materials is described. These materials are investigated as candidate protection materials for the Plasma Facing Components of NET/ITER. These materials are: carbon fibre composite graphite, pyrolytic graphite and boronated graphite. The volume of the laser induced craters was measured with an optical topographic scanner, and these data are evaluated with a simple model for the erosion. As a results, the enthalpy of ablation is estimated as 30±3 MJ/kg. A comparison is made with finite element numerical calculations, and the effect of lateral heat transfer is estimated using an analytical model. (author). 8 refs., 23 figs., 4 tabs

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

    International Nuclear Information System (INIS)

    Beleznai, Sz; Mihajlik, G; Richter, P; Maros, I; Balazs, L

    2008-01-01

    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 * 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

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

    International Nuclear Information System (INIS)

    Anders, A.; Brown, I.; MacGill, R.; Dickinson, M.

    1996-01-01

    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 μs) 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

  18. High ion charge states in a high-current, short-pulse, vacuum arc ion source

    International Nuclear Information System (INIS)

    Anders, A.; Brown, I.; MacGill, R.; Dickinson, M.

    1995-09-01

    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 micros) 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

  19. Hot-electron surface retention in intense short-pulse laser-matter interactions.

    Science.gov (United States)

    Mason, R J; Dodd, E S; Albright, B J

    2005-07-01

    Implicit hybrid plasma simulations predict that a significant fraction of the energy deposited into hot electrons can be retained near the surface of targets with steep density gradients illuminated by intense short-pulse lasers. This retention derives from the lateral transport of heated electrons randomly emitted in the presence of spontaneous magnetic fields arising near the laser spot, from geometric effects associated with a small hot-electron source, and from E fields arising in reaction to the ponderomotive force. Below the laser spot hot electrons are axially focused into a target by the B fields, and can filament in moderate Z targets by resistive Weibel-like instability, if the effective background electron temperature remains sufficiently low. Carefully engineered use of such retention in conjunction with ponderomotive density profile steepening could result in a reduced hot-electron range that aids fast ignition. Alternatively, such retention may disturb a deeper deposition needed for efficient radiography and backside fast ion generation.

  20. Integrable discretizations and self-adaptive moving mesh method for a coupled short pulse equation

    International Nuclear Information System (INIS)

    Feng, Bao-Feng; Chen, Junchao; Chen, Yong; Maruno, Ken-ichi; Ohta, Yasuhiro

    2015-01-01

    In the present paper, integrable semi-discrete and fully discrete analogues of a coupled short pulse (CSP) equation are constructed. The key to the construction are the bilinear forms and determinant structure of the solutions of the CSP equation. We also construct N-soliton solutions for the semi-discrete and fully discrete analogues of the CSP equations in the form of Casorati determinants. In the continuous limit, we show that the fully discrete CSP equation converges to the semi-discrete CSP equation, then further to the continuous CSP equation. Moreover, the integrable semi-discretization of the CSP equation is used as a self-adaptive moving mesh method for numerical simulations. The numerical results agree with the analytical results very well. (paper)

  1. Control of the spin polarization of photoelectrons/photoions using short laser pulses

    International Nuclear Information System (INIS)

    Nakajima, Takashi

    2004-01-01

    We present a generic pump-probe scheme to control spin polarization of photoelectrons/photoions by short laser pulses. By coherently exciting fine structure manifolds of a multi-valence-electron system by the pump laser, a superposition of fine structure states is created. Since each fine structure state can be further decomposed into a superposition of various spin states of valence electrons, each spin component evolves differently in time. This means that varying the time delay between the pump and probe lasers leads to the control of spin states. Specific theoretical results are presented for two-valence-electron atoms, in particular for Mg, which demonstrate that not only the degree of spin polarization but also its sign can be manipulated through time delay. Since the underline physics is rather general and transparent, the presented idea may be potentially applied to nanostructures such as quantum wells and quantum dots

  2. Short-pulsed laser for the treatment of tattoos, pigmented lesions, scars and rejuvenation.

    Science.gov (United States)

    Tanghetti, Emil A; Hoffmann, Kristina Andrea; Hoffmann, Klaus

    2017-12-01

    This review describes the use of picosecond lasers for the treatment of tattoos, pigmented lesions, scars, and their use in rejuvenation. These devices have delivered enhanced efficacy for the treatment of tattoos and pigmented lesions when compared to the older 40-50 nanosecond devices. The fractional delivery with the picosecond devices have opened up a new method of rejuvenation for photodamaged skin and the treatment of scars. The delivery of these high-energy short pulses have created zones of injury in the skin referred to as areas of laser-induced optical breakdown. These areas of damage appear to produce cytokines and chemokines which result in epidermal and dermal repair and remodeling. The dual use of these devices with the flat and the fractional optics have made these devices useful in many ways that have been unanticipated. ©2017 Frontline Medical Communications.

  3. Collisionless energy absorption in the short-pulse intense laser-cluster interaction

    International Nuclear Information System (INIS)

    Kundu, M.; Bauer, D.

    2006-01-01

    In a previous paper [Phys. Rev. Lett. 96, 123401 (2006)] we have shown by means of three-dimensional particle-in-cell simulations and a simple rigid-sphere model that nonlinear resonance absorption is the dominant collisionless absorption mechanism in the intense, short-pulse laser cluster interaction. In this paper we present a more detailed account of the matter. In particular we show that the absorption efficiency is almost independent of the laser polarization. In the rigid-sphere model, the absorbed energy increases by many orders of magnitude at a certain threshold laser intensity. The particle-in-cell results display maximum fractional absorption around the same intensity. We calculate the threshold intensity and show that it is underestimated by the common overbarrier ionization estimate

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

    Science.gov (United States)

    Sokolowski-Tinten, Klaus; Ziegler, Wolfgang; von der Linde, Dietrich; Siegal, Michael P.; Overmyer, D. L.

    2005-03-01

    Short-pulse-laser-induced damage and ablation of thin films of amorphous, diamond-like carbon have been investigated. Material removal and damage are caused by fracture of the film and ejection of large fragments. The fragments exhibit a delayed, intense and broadband emission of microsecond duration. Both fracture and emission are attributed to the laser-initiated relaxation of the high internal stresses of the pulse laser deposition-grown films.

  5. Recrystallization and grain growth behavior of rolled tungsten under VDE-like short pulse high heat flux loads

    International Nuclear Information System (INIS)

    Yuan, Y.; Greuner, H.; Böswirth, B.; Krieger, K.; Luo, G.-N.; Xu, H.Y.; Fu, B.Q.; Li, M.; Liu, W.

    2013-01-01

    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 max was found. ► Activation energy for grain growth in T evolution up to T 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 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 max ) was found and accordingly the activation energy for grain growth in temperature evolution up to T 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

  6. Ultra-short laser pulse ablation using shear-force feedback: Femtosecond laser induced breakdown spectroscopy feasibility study

    International Nuclear Information System (INIS)

    Samek, Ota; Kurowski, Andre; Kittel, Silke; Kukhlevsky, Sergei; Hergenroeder, Roland

    2005-01-01

    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

  7. VCSELs in short-pulse operation for time-of-flight applications

    Science.gov (United States)

    Moench, Holger; Gronenborn, Stephan; Gu, Xi; Gudde, Ralph; Herper, Markus; Kolb, Johanna; Miller, Michael; Smeets, Michael; Weigl, Alexander

    2018-02-01

    VCSEL arrays are the ideal light source for 3D imaging applications. The narrow emission spectrum and the ability for short pulses make them superior to LEDs. Combined with fast photodiodes or special camera chips spatial information can be obtained which is needed in diverse applications like camera autofocus, indoor navigation, 3D-object recognition, augmented reality or autonomously driving vehicles. Pulse operation at the ns scale and at low duty cycle can work with significantly higher current than traditionally used for VCSELs in continuous wave operation. With reduced thermal limitations at low average heat dissipation very high currents become feasible and tens of Watts output power have been realized with small VCSEL chips. The optical emission pattern of VCSELs can be tailored to the desired field of view using beam shaping elements. Such optical elements also enable laser safe class 1 products. A detailed analysis of the complete system and the operation mode is required to calculate the maximum permitted power for a safe system. The good VCSEL properties like robustness, stability over temperature and the potential for integrated solutions open a huge potential for VCSELs in new mass applications in the consumer and automotive markets.

  8. Short-pulse-width micromachining of hard materials using DPSS Nd:YAG lasers

    Science.gov (United States)

    Heglin, Michael; Govorkov, Sergei V.; Scaggs, Michael J.; Theoharidis, Haris; Schoelzel, T.

    2002-06-01

    The material processing of an industrial, short-pulse duration DPPS YAG laser producing peak powers greater than 0.2MW is discussed in this paper. This peak power provides sufficient materials processing capability to meet the micro machining needs in the automotive, semiconductor, micro- electronic, medical and telecommunication industries. All hard and soft materials including: plastics, metals, ceramics, diamond and other crystalline materials are suitable candidates for the processing capability of this laser. Micro level features can be machined in these materials to a depth in excess of 1mm with high quality results. In most applications feature sizes can be achieved that are not possible or economical with existing technologies. The optical beam delivery system requirements, and overall micro-machining set-up are also described. The drilling and cutting versatility down to feature sizes of less than 7 micrometers , as well as, complex shapes are shown. The wavelength, pulse length, and peakpower are described and relate to their effect on recast, micro-cracking and material removal rates. Material removal effects related to progressive penetration into the material will be reviewed. The requirements of this DPSS laser technology to meet the operational requirements for high duty cycle operation in industrial environments is covered along with processing flexibility and lower operating cost.

  9. Lattice Boltzmann method for short-pulsed laser transport in a multi-layered medium

    International Nuclear Information System (INIS)

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

    2015-01-01

    We construct a lattice Boltzmann method (LBM) for transient radiative transfer in one-dimensional multi-layered medium with distinct refractive index in each layer. The left boundary is irradiated normally by a short-pulsed laser. The Fresnel interfaces conditions, which incorporate reflection and refraction, are used at the boundaries and the interfaces. Based on the Fresnel's law and Snell's law, the interfacial intensity formulas are introduced. The collimated and diffuse intensities are treated individually. At a transient time step, the collimated component is first solved by LBM and then embedded into the transient radiative transfer equation as a source term. To keep the consistency of the directions in all the layers, angular interpolation of the intensities at the interfaces is adopted. The transient radiative transfer in a two-layer medium is first investigated, and the time-resolved results are validated by comparing with those by the Monte Carlo method (MCM). Of particular interest, the angular intensities along the slab at different times are presented to illustrate a variety of interesting phenomena, and the discontinuous nature of the intensity at the interfaces is discussed. The effects of various parameters on the time-resolved signals are examined. - Highlights: • Transient radiative transfer in a multi-layered medium is solved by LBM. • The boundary and interfaces are all considered as Fresnel surfaces. • The LBM solution for the collimated pulse is derived. • Discontinuous nature of the intensity at the interface is illustrated and discussed

  10. A short-pulse mode for the SPHINX LTD Z-pinch driver

    Science.gov (United States)

    D'Almeida, Thierry; Lassalle, Francis; Zucchini, Frederic; Loyen, Arnaud; Morell, Alain; Chuvatin, Alexander

    2015-11-01

    The SPHINX machine is a 6MA, 1 μs, LTD Z-pinch driver at CEA Gramat (France) and primarily used for studying radiation effects. Different power amplification concepts were examined in order to reduce the current rise time without modifying the generator discharge scheme, including the Dynamic Load Current Multiplier (DLCM) proposed by Chuvatin. A DLCM device, capable of shaping the current pulse without reducing the rise time, was developed at CEA. This device proved valuable for isentropic compression experiments in cylindrical geometry. Recently, we achieved a short pulse operation mode by inserting a vacuum closing switch between the DLCM and the load. The current rise time was reduced to ~300 ns. We explored the use of a reduced-height wire array for the Dynamic Flux Extruder in order to improve the wire array compression rate and increase the efficiency of the current transfer to the load. These developments are presented. Potential benefits of these developments for future Z pinch experiments are discussed.

  11. 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.

  12. Cold cathode electron guns in the LASL high power short-pulse CO2 laser program

    International Nuclear Information System (INIS)

    Singer, S.; Ladish, J.S.; Nutter, M.J.

    1975-01-01

    The Electron Beam Controlled Discharge CO 2 Laser is now firmly established as the only high power short pulse laser amplifier that has been demonstrated to have scaling capabilities to large apertures and energies much greater than 100 J. These devices require a beam of energetic electrons to control the gas discharge that produces the required population inversion. Until recently, the electron source was usually a thermionic emitter, even for rather large lasers, whose heater requirements dwarfed the pulsed energies associated with the transient operation of the laser. With the advent of reliable cold-cathode electron guns, the operation of these lasers has been greatly simplified. At LASL, there are four electron beam controlled laser systems which are in operation, under construction, or in design: the 1 kJ system, now operational; the 2.5 kJ system; the 10 kJ system; and the 100 kJ system. Only the first uses thermionic-emitter electron guns; the remainder use or will use cold cathode sources. The operation of the 200 x 35 cm 2 two sided cold cathode electron gun used in the 2.5 kJ laser system and to be used in the 10 kJ laser is described

  13. 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.

  14. 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.

  15. Simulation of primary processes for laser-induced plasma by short laser pulses in KDP crystal

    International Nuclear Information System (INIS)

    Gayet, R.; Jequier, S.; Bachau, H.; Rodriguez, V.; Duchateau, G.; Dyan, A.; Mathis, H.

    2006-01-01

    Complete test of publication follows. A theoretical approach designed for the description of local micro-plasma formation induced by short laser pulses in KH 2 PO 4 (KDP) crystal is addressed. Indeed, when such a crystal is illuminated by short pulses, the early stage of photo-production, enhanced by local defects, leads to a subsequent strong electronic absorption revealing a transient metallic-like behavior. The lattice then is rapidly heated up by electron-phonon coupling at temperature as high as 10000 K. This results in the local formation of a micro-plasma whose initial electronic energy distribution, which can be used in Particle-In-Cell codes, may be predicted by the present approach. The latter includes both, electron promotion from the valence band to the conduction band, and the subsequent interaction with phonons and photons. The electron promotion is described by a theoretical method based on Coulomb-Volkov (CV) wave functions whereas the electron diffusion in the conduction band is described by the standard Boltzmann's formalism. Although results about diffusion are shown, the present work focuses on the photo-production step. Hence, an extension of a previous theory, which has been developed essentially to describe ionization of atoms or molecules by intense femtosecond laser pulses, in under way. The first theory gives reliable predictions whenever both, (i) the photon energy is greater than the ionization potential, and (ii) perturbation conditions prevail. The restriction (i) prevents from intermediate state contribution to the ionization mechanism. The CV approach has been improved by introducing these states in the initial wave function, thus leading to an excellent agreement with predictions based on a full numerical solution to the time-dependent Schroedinger equation. Further, keeping the restriction (i), one can discard the condition (ii) by introducing a time-dependent initial state population in a CV approach. Since defects induce

  16. Novel short-pulse laser diode source for high-resolution 3D flash lidar

    Science.gov (United States)

    Canal, Celine; Laugustin, Arnaud; Kohl, Andreas; Rabot, Olivier

    2017-06-01

    Imaging based on laser illumination is present in various fields of applications such as medicine, security, defense, civil engineering and in the automotive sector. In this last domain, research and development to bring autonomous vehicles on the roads has been intensified the recent years. Among the various technologies currently studied, automotive lidars are a fast-growing one due to their accuracy to detect a wide range of objects at distances up to a few hundreds of meters in various weather conditions. First commercialized devices for ADAS were laser scanners. Since then, new architectures have recently appeared such as solid-state lidar and flash lidar that offer a higher compactness, robustness and a cost reduction. Flash lidars are based on time-of-flight measurements, with the particularity that they do not require beam scanners because only one short laser pulse with a large divergence is used to enlighten the whole scene. Depth of encountered objects can then be recovered from measurement of echoed light at once, hence enabling real-time 3D mapping of the environment. This paper will bring into the picture a cutting edge laser diode source that can deliver millijoule pulses as short as 12 ns, which makes them highly suitable for integration in flash lidars. They provide a 100-kW peak power highly divergent beam in a footprint of 4x5 cm2 (including both the laser diode and driver) and with a 30-% electrical-to-optical efficiency, making them suitable for integration in environments in which compactness and power consumption are a priority. Their emission in the range of 800-1000 nm is considered to be eye safe when taking into account the high divergence of the output beam. An overview of architecture of these state-of-the-art pulsed laser diode sources will be given together with some solutions for their integration in 3D mapping systems. Future work leads will be discussed for miniaturization of the laser diode and drastic cost reduction.

  17. Advances in High Power Calorimetric Matched Loads for Short Pulses and CW Gyrotrons

    International Nuclear Information System (INIS)

    Bin, W.M.; Bruschi, A.; Cirant, S.; Gandini, F.; Granucci, G.; Mellera, V.; Muzzini, V.; Nardone, A.; Sozzi, C.; Spinicchia, N.

    2006-01-01

    The development of high power gyrotrons for plasma physics research needs proper matched and calorimetric loads able to absorb and measure the power, which nowadays is foreseen to be as high as 2 MW during CW operations. To this end IFP/CNR has developed a family of matched loads useful in the mm-wave frequency band for applications ranging from a few ms to CW in pulse length. The different loads in the family, made of an integrating sphere with a partially reflecting coating on the inner wall, are characterized by having the same absorbing geometry for the incoming beam and a different heat removal system for the specific application. Some important advances have been recently achieved from the point of view of the uniformity of power distribution on the absorbing wall and of the load construction. With high precision achieved in the coating thickness a better control of the heating power distribution is possible by proper shaping of the local reflectivity, in addition to the shaping of the mirror dispersing the input beam. A more sophisticated model describing the power distribution has been developed, taking into account a variable thickness of the absorbing coating, the proper shape of the spreading mirror, the frequency of the incoming radiation and the shape of the input beam. Lower coating thickness is shown to be preferable, at equal local reflectivity, from the point of view of a lower peak temperature and thermal stress. The paper describes a load with variable coating thickness along the meridian of the sphere, showing a uniform power deposition on the inner walls. The cooling pipe is completely electroformed on the spherical copper shell, ensuring the maintenance of the correct curvature of the inner surface and a fast heat conduction from the absorbing coating to the water through the thin copper body. For CW use all heated parts of the load must be cooled and this is achieved by 16 electroformed spiral channels. Both short pulse loads (0.1-1 s) and

  18. Pulse-height defect in single-crystal CVD diamond detectors

    Energy Technology Data Exchange (ETDEWEB)

    Beliuskina, O.; Imai, N. [The University of Tokyo, Center for Nuclear Study, Wako, Saitama (Japan); Strekalovsky, A.O.; Aleksandrov, A.A.; Aleksandrova, I.A.; Ilich, S.; Kamanin, D.V.; Knyazheva, G.N.; Kuznetsova, E.A.; Mishinsky, G.V.; Pyatkov, Yu.V.; Strekalovsky, O.V.; Zhuchko, V.E. [JINR, Flerov Laboratory of Nuclear Reactions, Dubna, Moscow Region (Russian Federation); Devaraja, H.M. [Manipal University, Manipal Centre for Natural Sciences, Manipal, Karnataka (India); Heinz, C. [II. Physikalisches Institut, Justus-Liebig-Universitaet Giessen, Giessen (Germany); Heinz, S. [II. Physikalisches Institut, Justus-Liebig-Universitaet Giessen, Giessen (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Hofmann, S.; Kis, M.; Kozhuharov, C.; Maurer, J.; Traeger, M. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Pomorski, M. [CEA, LIST, Diamond Sensor Laboratory, CEA/Saclay, Gif-sur-Yvette (France)

    2017-02-15

    The pulse-height versus deposited energy response of a single-crystal chemical vapor deposition (scCVD) diamond detector was measured for ions of Ti, Cu, Nb, Ag, Xe, Au, and of fission fragments of {sup 252} Cf at different energies. For the fission fragments, data were also measured at different electric field strengths of the detector. Heavy ions have a significant pulse-height defect in CVD diamond material, which increases with increasing energy of the ions. It also depends on the electrical field strength applied at the detector. The measured pulse-height defects were explained in the framework of recombination models. Calibration methods known from silicon detectors were modified and applied. A comparison with data for the pulse-height defect in silicon detectors was performed. (orig.)

  19. Excitation of random intense single-cycle light-pulse chains in optical fiber

    International Nuclear Information System (INIS)

    Ding, Y C; Zhang, F L; Gao, J B; Chen, Z Y; Lin, C Y; Yu, M Y

    2014-01-01

    Excitation of intense periodic single-cycle light pulses in a stochastic background arising from continuous wave stimulated Brillouin scattering (SBS) in a long optical fiber with weak optical feedback is found experimentally and modeled theoretically. Such intense light-pulse chains occur randomly and the optical feedback is a requirement for their excitation. The probability of these forms, among the large number of experimental output signals with identifiable waveforms, appearing is only about 3%, with the remainder exhibiting regular SBS characteristics. It is also found that pulses with low period numbers appear more frequently and the probability distribution for their occurrence in terms of the pulse power is roughly L-shaped, like that for rogue waves. The results from a three-wave-coupling model for SBS including feedback phase control agree well qualitatively with the observed phenomena. (paper)

  20. Catastrophic optical mirror damage in diode lasers monitored during single-pulse operation

    DEFF Research Database (Denmark)

    Zegler, M.; Tomm, J.W.; Reeber, D.

    2009-01-01

    is achieved. The thermal runaway process is unambiguously related to the occurrence of a “thermal flash.” A one-by-one correlation between nearfield, thermal flash, thermal runaway, and structural damage is observed. The single-pulse excitation technique allows for controlling the propagation...

  1. Visual CRO display of pulse height distribution including discriminator setting for a single channel X-ray analyser

    International Nuclear Information System (INIS)

    Shaw, S.E.

    1979-01-01

    An outline for a simple pulse spectroscope which attaches to a standard laboratory CRO is presented. The peak amplitude voltage of each pulse from the linear amplifier of a single channel X-ray analyser is stored for the duration of one oscilloscope trace. For each amplifier pulse, input from the discriminator is tested and if these is coincidence of pulses the oscilloscope beam is blanked for approximately the first 2 cm of its traverse across the screen. Repetition of pulses forms a pulse height distribution with a rectangular dark area marking the position of the discriminator window. (author)

  2. Short pulse generation from a passively mode-locked fiber optical parametric oscillator with optical time-stretch.

    Science.gov (United States)

    Qiu, Yi; Wei, Xiaoming; Du, Shuxin; Wong, Kenneth K Y; Tsia, Kevin K; Xu, Yiqing

    2018-04-16

    We propose a passively mode-locked fiber optical parametric oscillator assisted with optical time-stretch. Thanks to the lately developed optical time-stretch technique, the onset oscillating spectral components can be temporally dispersed across the pump envelope and further compete for the parametric gain with the other parts of onset oscillating sidebands within the pump envelope. By matching the amount of dispersion in optical time-stretch with the pulse width of the quasi-CW pump and oscillating one of the parametric sidebands inside the fiber cavity, we numerically show that the fiber parametric oscillator can be operated in a single pulse regime. By varying the amount of the intracavity dispersion, we further verify that the origin of this single pulse mode-locking regime is due to the optical pulse stretching and compression.

  3. Cutting and drilling of carbon fiber reinforced plastics (CFRP) by 70W short pulse nanosecond laser

    Science.gov (United States)

    Jaeschke, Peter; Stolberg, Klaus; Bastick, Stefan; Ziolkowski, Ewa; Roehner, Markus; Suttmann, Oliver; Overmeyer, Ludger

    2014-02-01

    Continuous carbon fibre reinforced plastics (CFRP) are recognized as having a significant lightweight construction potential for a wide variety of industrial applications. However, a today`s barrier for a comprehensive dissemination of CFRP structures is the lack of economic, quick and reliable manufacture processes, e.g. the cutting and drilling steps. In this paper, the capability of using pulsed disk lasers in CFRP machining is discussed. In CFRP processing with NIR lasers, carbon fibers show excellent optical absorption and heat dissipation, contrary to the plastics matrix. Therefore heat dissipation away from the laser focus into the material is driven by heat conduction of the fibres. The matrix is heated indirectly by heat transfer from the fibres. To cut CFRP, it is required to reach the melting temperature for thermoplastic matrix materials or the disintegration temperature for thermoset systems as well as the sublimation temperature of the reinforcing fibers simultaneously. One solution for this problem is to use short pulse nanosecond lasers. We have investigated CFRP cutting and drilling with such a laser (max. 7 mJ @ 10 kHz, 30 ns). This laser offers the opportunity of wide range parameter tuning for systematic process optimization. By applying drilling and cutting operations based on galvanometer scanning techniques in multi-cycle mode, excellent surface and edge characteristics in terms of delamination-free and intact fiber-matrix interface were achieved. The results indicate that nanosecond disk laser machining could consequently be a suitable tool for the automotive and aircraft industry for cutting and drilling steps.

  4. Self-compression of intense short laser pulses in relativistic magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Olumi, M.; Maraghechi, B., E-mail: behrouz@aut.ac.ir [Department of Physics, Amirkabir University of Technology, Post code 15916-34311 Tehran (Iran, Islamic Republic of)

    2014-11-15

    The compression of a relativistic Gaussian laser pulse in a magnetized plasma is investigated. By considering relativistic nonlinearity and using non-linear Schrödinger equation with paraxial approximation, a second-order differential equation is obtained for the pulse width parameter (in time) to demonstrate the longitudinal pulse compression. The compression of laser pulse in a magnetized plasma can be observed by the numerical solution of the equation for the pulse width parameter. The effects of magnetic field and chirping are investigated. It is shown that in the presence of magnetic field and negative initial chirp, compression of pulse is significantly enhanced.

  5. Timing Solution and Single-pulse Properties for Eight Rotating Radio Transients

    Energy Technology Data Exchange (ETDEWEB)

    Cui, B.-Y.; McLaughlin, M. A. [Department of Physics and Astronomy West Virginia University Morgantown, WV 26506 (United States); Boyles, J. [Department of Physics and Astronomy West Kentucky University Bowling Green, KY 42101 (United States); Palliyaguru, N. [Physics and Astronomy Department Texas Tech University Lubbock, TX 79409-1051 (United States)

    2017-05-01

    Rotating radio transients (RRATs), loosely defined as objects that are discovered through only their single pulses, are sporadic pulsars that have a wide range of emission properties. For many of them, we must measure their periods and determine timing solutions relying on the timing of their individual pulses, while some of the less sporadic RRATs can be timed by using folding techniques as we do for other pulsars. Here, based on Parkes and Green Bank Telescope (GBT) observations, we introduce our results on eight RRATs including their timing-derived rotation parameters, positions, and dispersion measures (DMs), along with a comparison of the spin-down properties of RRATs and normal pulsars. Using data for 24 RRATs, we find that their period derivatives are generally larger than those of normal pulsars, independent of any intrinsic correlation with period, indicating that RRATs’ highly sporadic emission may be associated with intrinsically larger magnetic fields. We carry out Lomb–Scargle tests to search for periodicities in RRATs’ pulse detection times with long timescales. Periodicities are detected for all targets, with significant candidates of roughly 3.4 hr for PSR J1623−0841 and 0.7 hr for PSR J1839−0141. We also analyze their single-pulse amplitude distributions, finding that log-normal distributions provide the best fits, as is the case for most pulsars. However, several RRATs exhibit power-law tails, as seen for pulsars emitting giant pulses. This, along with consideration of the selection effects against the detection of weak pulses, imply that RRAT pulses generally represent the tail of a normal intensity distribution.

  6. Timing Solution and Single-pulse Properties for Eight Rotating Radio Transients

    Science.gov (United States)

    Cui, B.-Y.; Boyles, J.; McLaughlin, M. A.; Palliyaguru, N.

    2017-05-01

    Rotating radio transients (RRATs), loosely defined as objects that are discovered through only their single pulses, are sporadic pulsars that have a wide range of emission properties. For many of them, we must measure their periods and determine timing solutions relying on the timing of their individual pulses, while some of the less sporadic RRATs can be timed by using folding techniques as we do for other pulsars. Here, based on Parkes and Green Bank Telescope (GBT) observations, we introduce our results on eight RRATs including their timing-derived rotation parameters, positions, and dispersion measures (DMs), along with a comparison of the spin-down properties of RRATs and normal pulsars. Using data for 24 RRATs, we find that their period derivatives are generally larger than those of normal pulsars, independent of any intrinsic correlation with period, indicating that RRATs’ highly sporadic emission may be associated with intrinsically larger magnetic fields. We carry out Lomb-Scargle tests to search for periodicities in RRATs’ pulse detection times with long timescales. Periodicities are detected for all targets, with significant candidates of roughly 3.4 hr for PSR J1623-0841 and 0.7 hr for PSR J1839-0141. We also analyze their single-pulse amplitude distributions, finding that log-normal distributions provide the best fits, as is the case for most pulsars. However, several RRATs exhibit power-law tails, as seen for pulsars emitting giant pulses. This, along with consideration of the selection effects against the detection of weak pulses, imply that RRAT pulses generally represent the tail of a normal intensity distribution.

  7. Production of very short electron, X or γ-ray pulses by means of laser and magnetic compression techniques

    International Nuclear Information System (INIS)

    Joly, S.

    1995-01-01

    The ELSA electron accelerator, initially developed for a free-electron laser, is under modification to deliver very short X and γ-ray pulses (10 to 20 ps). This paper describes the main characteristics of the accelerator as well as the physical processes used to generate these radiation bursts. (author). 5 refs., 3 figs

  8. Clinical observation of one time short-pulse pattern scan laser pan-retinal photocoagulation for proliferative diabetic retinopathy

    Directory of Open Access Journals (Sweden)

    Xin Liu

    2016-04-01

    Full Text Available AIM: To investigate the clinical efficacy and benefit of short-pulse pattern scan laser(PASCALphotocoagulation for proliferative diabetic retinopathy(PDR.METHODS:Twenty-eight PDR patients(42 eyesunderwent short-pulse PASCAL pan-retinal photocoagulation(PRPwere analyzed.The best corrected visual acuity was ≥0.1 in 36 eyes, RESULTS: All the cases had no pain during the short-pulse PASCAL treatment.One year after treatments,the final visual acuity was improved in 6 eyes,kept stable in 28 eyes and decreased in 8 eyes; neovascularization were regressed in 18 eyes(43%, stable in 12 eyes(29%, uncontrolled in 12 eyes(29%. Five eyes(12%received vitrectomy due to vitreous hemorrhage.Compared with before operation, retina thickness in central fovea of macula and visual field had no obvious change after one-time PASCAL PRP(P>0.05. CONCLUSION:The one-time short-pulse PASCAL PRP could stabilize the progress of PDR safely, effectively and simply.

  9. 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:

  10. Modification of MEA modulator-klystron units enabling short pulse injection into a pulse-stretcher ring

    International Nuclear Information System (INIS)

    Kroes, F.B.; Heine, E.

    1989-01-01

    In order to modify the present 500 MeV, 1% duty factor electron accelerator MEA into a 900 MeV, 0.1% d.f. injector for a newly to be build pulse- stretching ring, the present modulator-klystron units have to be adapted from 4 MW, 2% d.f. mode of operation into the 10 MW, 0.2% d.f. mode. Suitable klystrons are commercially available, the matching modulators, however, will be obtained by modifying the present ones, which policy is dictated by economical considerations. The design principles of these modulators -a proto-type is presently under construction- will be discussed. Special attention is given to the video-pulse shape requirements, dictated by the future performance of the pulse-stretcher. This device has to deliver low emittance, high duty factor (n90%) beams for nuclear physics experiments. Some proto-type tests of the video-pulse forming modifications will be presented. (author). 5 refs.; 11 figs.; 2 tabs

  11. Status and trends of short pulse generation using mode-locked lasers based on advanced quantum-dot active media

    International Nuclear Information System (INIS)

    Shi, L W; Chen, Y H; Xu, B; Wang, Z C; Jiao, Y H; Wang, Z G

    2007-01-01

    In this review, the potential of mode-locked lasers based on advanced quantum-dot (QD) active media to generate short optical pulses is analysed. A comprehensive review of experimental and theoretical work on related aspects is provided, including monolithic-cavity mode-locked QD lasers and external-cavity mode-locked QD lasers, as well as mode-locked solid-state and fibre lasers based on QD semiconductor saturable absorber mirrors. Performance comparisons are made for state-of-the-art experiments. Various methods for improving important characteristics of mode-locked pulses such as pulse duration, repetition rate, pulse power, and timing jitter through optimization of device design parameters or mode-locking methods are addressed. In addition, gain switching and self-pulsation of QD lasers are also briefly reviewed, concluding with the summary and prospects. (topical review)

  12. Quantum computers based on electron spins controlled by ultrafast off-resonant single optical pulses.

    Science.gov (United States)

    Clark, Susan M; Fu, Kai-Mei C; Ladd, Thaddeus D; Yamamoto, Yoshihisa

    2007-07-27

    We describe a fast quantum computer based on optically controlled electron spins in charged quantum dots that are coupled to microcavities. This scheme uses broadband optical pulses to rotate electron spins and provide the clock signal to the system. Nonlocal two-qubit gates are performed by phase shifts induced by electron spins on laser pulses propagating along a shared waveguide. Numerical simulations of this scheme demonstrate high-fidelity single-qubit and two-qubit gates with operation times comparable to the inverse Zeeman frequency.

  13. Polymer optical fiber Bragg grating inscription with a single UV laser pulse

    DEFF Research Database (Denmark)

    Pospori, Andreas; Marques, A.T.; Bang, Ole

    2017-01-01

    We experimentally demonstrate the first polymer optical fiber Bragg grating inscribed with only one krypton fluoride laser pulse. The device has been recorded in a single-mode poly(methyl methacrylate) optical fiber, with a core doped with benzyl dimethyl ketal for photosensitivity enhancement. One...... laser pulse with a duration of 15 ns, which provide energy density of 974 mJ/cm2, is adequate to introduce a refractive index change of 0.74×10-4 in the fiber core. After the exposure, the reflectivity of the grating increases for a few minutes following a second order exponential saturation...

  14. Pulsed single-photon spectrometer by frequency-to-time mapping using chirped fiber Bragg gratings.

    Science.gov (United States)

    Davis, Alex O C; Saulnier, Paul M; Karpiński, Michał; Smith, Brian J

    2017-05-29

    A fiber-integrated spectrometer for single-photon pulses outside the telecommunications wavelength range based upon frequency-to-time mapping, implemented by chromatic group delay dispersion (GDD), and precise temporally-resolved single-photon counting, is presented. A chirped fiber Bragg grating provides low-loss GDD, mapping the frequency distribution of an input pulse onto the temporal envelope of the output pulse. Time-resolved detection with fast single-photon-counting modules enables monitoring of a wavelength range from 825 nm to 835 nm with nearly uniform efficiency at 55 pm resolution (24 GHz at 830 nm). To demonstrate the versatility of this technique, spectral interference of heralded single photons and the joint spectral intensity distribution of a photon-pair source are measured. This approach to single-photon-level spectral measurements provides a route to realize applications of time-frequency quantum optics at visible and near-infrared wavelengths, where multiple spectral channels must be simultaneously monitored.

  15. Single-electron pulse-height spectra in thin-gap parallel-plate chambers

    CERN Document Server

    Fonte, Paulo J R; Peskov, Vladimir; Policarpo, Armando

    1999-01-01

    Single-electron pulse-height spectra were measured in 0.6 and 1.2 mm parallel-plate chambers developed for the TOF system of the ALICE /LHC-HI experiment. Mixtures of Ar with ethane, isobutane, and SF/sub 6/ were studied. The observed spectrum shows a clear peak for all gases, suggesting efficient single-electron detection in thin parallel-plate structures. The pulse-height spectrum can be described by the weighted sum of an exponential and a Polya distribution, the Polya contribution becoming more important at higher gains. Additionally, it was found that the maximum gain, above 10/sup 6/, is limited by the appearance of streamers and depends weakly on the gas composition. The suitability of each mixture for single-electron detection is also quantitatively assessed. (8 refs).

  16. High intensity pulse self-compression in short hollow core capillaries

    OpenAIRE

    Butcher, Thomas J.; Anderson, Patrick N.; Horak, Peter; Frey, Jeremy G.; Brocklesby, William S.

    2011-01-01

    The drive for shorter pulses for use in techniques such as high harmonic generation and laser wakefield acceleration requires continual improvement in post-laser pulse compression techniques. The two most commonly used methods of pulse compression for high intensity pulses are hollow capillary compression via self-phase modulation (SPM) [1] and the more recently developed filamentation [2]. Both of these methods can require propagation distances of 1-3 m to achieve spectral broadening and com...

  17. Evaluation of short repetition time, partial flip angle, gradient recalled echo pulse sequences in cervical spine imaging

    International Nuclear Information System (INIS)

    Enzmann, D.; Rubin, J.B.

    1987-01-01

    A short repetition time (TR), partial flip angle, gradient recalled echo pulse sequence (GRASS) was prospectively studied to optimize it for the diagnosis of cervical disk and cord disease in 98 patients. Changes in signal-to-noise ratio (SNR) and contrast were measured as the following parameters were varied: flip angle (3 0 to 18 0 ), TR (22-60 msec), and echo time (TE) (12.5-25 msec). Flip angle was the single most important parameter. For disk disease, cerebrospinal fluid (CSF) SNR peaked at an 8 0 flip angle in the axial view but at a 4 0 flip angle in the sagittal view. In the sagittal view, disk-CSF contrast decreased progressively from a flip angle of 3 0 , while in the axial view it peaked at 10 0 . For cord lesions the findings were similar except that lesion-cord contrast could be increased by lengthening both TR and TE. No one combination of parameters proved greatly superior for either disk disease or cord disease. The selection of parameters required balancing of several factors that often had opposing effects

  18. Ultra-short pulse delivery at high average power with low-loss hollow core fibers coupled to TRUMPF's TruMicro laser platforms for industrial applications

    Science.gov (United States)

    Baumbach, S.; Pricking, S.; Overbuschmann, J.; Nutsch, S.; Kleinbauer, J.; Gebs, R.; Tan, C.; Scelle, R.; Kahmann, M.; Budnicki, A.; Sutter, D. H.; Killi, A.

    2017-02-01

    Multi-megawatt ultrafast laser systems at micrometer wavelength are commonly used for material processing applications, including ablation, cutting and drilling of various materials or cleaving of display glass with excellent quality. There is a need for flexible and efficient beam guidance, avoiding free space propagation of light between the laser head and the processing unit. Solid core step index fibers are only feasible for delivering laser pulses with peak powers in the kW-regime due to the optical damage threshold in bulk silica. In contrast, hollow core fibers are capable of guiding ultra-short laser pulses with orders of magnitude higher peak powers. This is possible since a micro-structured cladding confines the light within the hollow core and therefore minimizes the spatial overlap between silica and the electro-magnetic field. We report on recent results of single-mode ultra-short pulse delivery over several meters in a lowloss hollow core fiber packaged with industrial connectors. TRUMPF's ultrafast TruMicro laser platforms equipped with advanced temperature control and precisely engineered opto-mechanical components provide excellent position and pointing stability. They are thus perfectly suited for passive coupling of ultra-short laser pulses into hollow core fibers. Neither active beam launching components nor beam trackers are necessary for a reliable beam delivery in a space and cost saving packaging. Long term tests with weeks of stable operation, excellent beam quality and an overall transmission efficiency of above 85 percent even at high average power confirm the reliability for industrial applications.

  19. Short-term plasticity and long-term potentiation mimicked in single inorganic synapses

    Science.gov (United States)

    Ohno, Takeo; Hasegawa, Tsuyoshi; Tsuruoka, Tohru; Terabe, Kazuya; Gimzewski, James K.; Aono, Masakazu

    2011-08-01

    Memory is believed to occur in the human brain as a result of two types of synaptic plasticity: short-term plasticity (STP) and long-term potentiation (LTP; refs , , , ). In neuromorphic engineering, emulation of known neural behaviour has proven to be difficult to implement in software because of the highly complex interconnected nature of thought processes. Here we report the discovery of a Ag2S inorganic synapse, which emulates the synaptic functions of both STP and LTP characteristics through the use of input pulse repetition time. The structure known as an atomic switch, operating at critical voltages, stores information as STP with a spontaneous decay of conductance level in response to intermittent input stimuli, whereas frequent stimulation results in a transition to LTP. The Ag2S inorganic synapse has interesting characteristics with analogies to an individual biological synapse, and achieves dynamic memorization in a single device without the need of external preprogramming. A psychological model related to the process of memorizing and forgetting is also demonstrated using the inorganic synapses. Our Ag2S element indicates a breakthrough in mimicking synaptic behaviour essential for the further creation of artificial neural systems that emulate characteristics of human memory.

  20. Dynamics of ultra-short electromagnetic pulses in the system of chiral carbon nanotube waveguides in the presence of external alternating electric field

    Energy Technology Data Exchange (ETDEWEB)

    Konobeeva, N.N., E-mail: yana_nn@inbox.ru [Volgograd State University, University Avenue 100, Volgograd 400062 (Russian Federation); Belonenko, M.B. [Volgograd Institute of Business, Uzhno-ukrainskaya str., Volgograd 400048 (Russian Federation)

    2014-04-01

    The paper addresses the propagation of ultra-short optical pulses in chiral carbon nanotubes in the presence of external alternating electric field. Following the assumption that the considered optical pulses are represented in the form of discrete solitons, we analyze the wave equation for the electromagnetic field and consider the dynamics of pulses in external field, their initial amplitudes and frequencies.

  1. Chemical and physical analysis on hard tissues after irradiation with short pulse Nd:YAG laser

    International Nuclear Information System (INIS)

    Pereira, Andrea Antunes

    2003-01-01

    This work reports on a study that was designed to investigate chemical, physical and morphological alterations in the dental enamel surface. The influence of application of laser in enamel surface by microscopic technical, X-ray fluorescence for chemical analysis, physical property as well as hardness and thermal analysis with Nd:YAG laser is also pointed out. A prototype of Nd:YAG (Q-switched) laser developed at the Center of Lasers and Applications - Institute of Energetic and Nuclear Research, aiming applications in the Medical Sciences that typical wavelength of 1.064 nm was used. The modifications in human dental enamel chemical composition for major and trace elements are here outlined. The accuracy of procedures was performed by analysis of natural hydroxyapatite as standard reference material. The identification and quantification of the chemical elements presented in the dental tissue samples were performed trough EDS, XRF and INAA. We determined the rate Calcium/Phosphorus (Ca/P) for different techniques. We performed an analysis in different regions of the surface and for different areas allowing a description of the chemical change in the total area of the specimen and the assessment of the compositional homogeneity of the each specimen. A comparison between XRF and INAA is presented. Based on morphological analysis of the irradiated surfaces with short pulse Nd:YAG laser we determined the area surrounded by the irradiation for the parameters for this thesis, and this technique allowed us to visualize the regions of fusion and re-solidification. The energy densities ranged from 10 J/cm 2 to 40 J/cm 2 , with pulse width of 6, 10 e 200 ns, and repetition rates of 5 and 7 Hz. In this thesis, FTIR-spectroscopy is used to analyze powder of mineralized tissue as well as enamel, dentine, root and cementum for human and bovine teeth after irradiation with short-pulse Nd:YAG laser. Characteristic spectra were obtained for the proteins components and mineral

  2. Thermal interaction of short-pulsed laser focused beams with skin tissues

    International Nuclear Information System (INIS)

    Jiao Jian; Guo Zhixiong

    2009-01-01

    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.

  3. 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...

  4. 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. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. 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.

  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. Self-organization of single filaments and diffusive plasmas during a single pulse in dielectric-barrier discharges

    International Nuclear Information System (INIS)

    Babaeva, Natalia Yu; Kushner, Mark J

    2014-01-01

    Self-organization of filaments in dielectric-barrier discharges (DBDs) probably has many origins. However, the dominant cause is proposed to be the accumulation of charge on the surfaces of the bounding dielectrics that reinforces successive discharge pulses to occur at the same locations. A secondary cause is the electrostatic repulsion of individual plasma filaments. Self-organization typically develops over many discharge pulses. In this paper, we discuss the results of a computational investigation of plasma filaments in overvoltage DBDs that, under select conditions, display self-organized patterns (SOPs) of plasma density during a single discharge pulse. (Overvoltage refers to the rapid application of a voltage in excess of the quasi-dc breakdown voltage.) The origin of the SOPs is a synergistic relationship between the speed of the surface-ionization waves that propagate along each dielectric and the rate at which avalanche occurs across the gap. For our test conditions, SOPs were not observed at lower voltages and gradually formed at higher voltages. The same conditions that result in SOPs, i.e. the application of an overvoltage, also produce more diffuse discharges. A transition from a single narrow filament to a more diffuse structure was observed as overvoltage was approached. The sensitivity of SOPs to the orientation and permittivity of the bounding dielectrics is discussed. (paper)

  8. 40-Tesla pulsed-field cryomagnet for single crystal neutron diffraction

    Science.gov (United States)

    Duc, F.; Tonon, X.; Billette, J.; Rollet, B.; Knafo, W.; Bourdarot, F.; Béard, J.; Mantegazza, F.; Longuet, B.; Lorenzo, J. E.; Lelièvre-Berna, E.; Frings, P.; Regnault, L.-P.

    2018-05-01

    We present the first long-duration and high duty cycle 40-T pulsed-field cryomagnet addressed to single crystal neutron diffraction experiments at temperatures down to 2 K. The magnet produces a horizontal field in a bi-conical geometry, ±15° and ±30° upstream and downstream of the sample, respectively. Using a 1.15 MJ mobile generator, magnetic field pulses of 100 ms length are generated in the magnet, with a rise time of 23 ms and a repetition rate of 6-7 pulses per hour at 40 T. The setup was validated for neutron diffraction on the CEA-CRG three-axis spectrometer IN22 at the Institut Laue Langevin.

  9. Discrete dislocation plasticity modeling of short cracks in single crystals

    NARCIS (Netherlands)

    Deshpande, VS; Needleman, A; Van der Giessen, E

    2003-01-01

    The mode-I crack growth behavior of geometrically similar edge-cracked single crystal specimens of varying size subject to both monotonic and cyclic axial loading is analyzed using discrete dislocation dynamics. Plastic deformation is modeled through the motion of edge dislocations in an elastic

  10. Two-pulse driving of D+D nuclear fusion within a single Coulomb exploding nanodroplet

    International Nuclear Information System (INIS)

    Last, Isidore; Jortner, Joshua; Peano, Fabio; Silva, Luis O.

    2010-01-01

    This paper presents a computational study of D+D fusion driven by Coulomb explosion (CE) within a single, homonuclear deuterium nanodroplet, subjected to double-pulse ultraintense laser irradiation. This irradiation scheme results in the attainment (by the first weaker pulse) of a transient inhomogeneous density profile, which serves as a target for the driving (by the second superintense pulse) of nonuniform CE that triggers overrun effects and induces intrananodroplet (INTRA) D+D fusion. Scaled electron and ion dynamics simulations were utilized to explore the INTRA D+D fusion yields for double-pulse, near-infrared laser irradiation of deuterium nanodroplets. The dependence of the INTRA yield on the nanodroplet size and on the parameters of the two laser pulses was determined, establishing the conditions for the prevalence of efficient INTRA fusion. The INTRA fusion yields are amenable to experimental observation within an assembly of nanodroplets. The INTRA D+D fusion can be distinguished from the concurrent internanodroplet D+D fusion reaction occurring in the macroscopic plasma filament and outside it in terms of the different energies of the neutrons produced in these two channels.

  11. Status of the Short-Pulse X-ray Project (SPX) at the Advanced Photon Source (APS)

    International Nuclear Information System (INIS)

    Nassiri, R.; Arnold, N.D.; Berenc, G.; Borland, M.; Bromberek, D.J.; Chae, Y.-C.; Decker, G.; Emery, L.; Fuerst, J.D.; Grelick, A.E.; Horan, D.; Lenkszus, F.; Lill, R.M.; Sajaev, V.; Smith, T.L.; Waldschmidt, G.J.; Wu, G.; Yang, B.X.; Zholents, A.; Byrd, J.M.; Doolittle, L.R.; Huang, G.; Cheng, G.; Ciovati, G.; Henry, J.; Kneisel, P.; Mammosser, J.D.; Rimmer, R.A.; Turlington, L.; Wang, H.

    2011-01-01

    The Advanced Photon Source Upgrade project (APS-U) at Argonne includes implementation of Zholents deflecting cavity scheme for production of short x-ray pulses. This is a joint project between Argonne National Laboratory, Thomas Jefferson National Laboratory, and Lawrence Berkeley National Laboratory. This paper describes performance characteristics of the proposed source and technical issues related to its realization. Ensuring stable APS storage ring operation requires reducing quality factors of these modes by many orders of magnitude. These challenges reduce to those of the design of a single-cell SC cavity that can achieve the desired operating deflecting fields while providing needed damping of all these modes. The project team is currently prototyping and testing several promising designs for single-cell cavities with the goal of deciding on a winning design in the near future. Here we describe the approach undertaken and report the preliminary results. The concept of using transverse superconducting rf deflecting cavities to produce high-repetition-rate picoseconds x-rays with the APS has been previously described. Briefly, two cavities are required: the first cavity to impose a chirp on the electron beam and a second cavity to cancel the effects on the electron beam of the first cavity. The cavities must have a deflecting mode frequency that is a harmonic h of the APS storage ring rf frequency, 352 MHz A workable choice of h=8 corresponds to a deflecting cavity frequency of 2815 MHz. R and D activities include design and prototyping of superconducting deflecting cavities and components, cryomodule, low-level rf, particle/optical beam diagnostics, and timing/synchronization.

  12. 15N incorporation into organ proteins of newborn rats following single pulse-labelling with different tracers

    International Nuclear Information System (INIS)

    Wutzke, K.D.; Plath, C.; Richter, I.; Heine, W.; Zhukova, T.P.; Sorokina, E.G.; Friedrich, M.

    1987-01-01

    A short-chain 15 N-peptide mixture characterized by an average chain length of 2.3 was obtained when 15 N-labelled yeast protein was hydrolyzed enzymatically by thermitase from Thermoactinomyces vulgaris. Fifteen newborn Wistar rats were given a single pulse of [ 15 N]glycine. [ 15 N]H 4 Cl and [ 15 N]yeast protein thermitasehydrolysate (YPTH) in a dosage of 50 mg 15 N excess kg -1 by gastric tube. In comparison with [ 15 N]glycine the 15 N incorporation rates of brain, muscle and liver were approximately 150% higher after [ 15 N]YPTH application. Uniform labelling, high 15 N enrichment, almost complete absorption, avoidance of imbalances and the low price make this tracer substance superior to other tracers conventionally used for organ labelling. (author)

  13. The tensile effect on crack formation in single crystal silicon irradiated by intense pulsed ion beam

    Science.gov (United States)

    Liang, Guoying; Shen, Jie; Zhang, Jie; Zhong, Haowen; Cui, Xiaojun; Yan, Sha; Zhang, Xiaofu; Yu, Xiao; Le, Xiaoyun

    2017-10-01

    Improving antifatigue performance of silicon substrate is very important for the development of semiconductor industry. The cracking behavior of silicon under intense pulsed ion beam irradiation was studied by numerical simulation in order to understand the mechanism of induced surface peeling observed by experimental means. Using molecular dynamics simulation based on Stillinger Weber potential, tensile effect on crack growth and propagation in single crystal silicon was investigated. Simulation results reveal that stress-strain curves of single crystal silicon at a constant strain rate can be divided into three stages, which are not similar to metal stress-strain curves; different tensile load velocities induce difference of single silicon crack formation speed; the layered stress results in crack formation in single crystal silicon. It is concluded that the crack growth and propagation is more sensitive to strain rate, tensile load velocity, stress distribution in single crystal silicon.

  14. The interaction of super-intense ultra-short laser pulse and micro-clusters with large atomic clusters

    International Nuclear Information System (INIS)

    Miao Jingwei; Yang Chaowen; An Zhu; Yuan Xuedong; Sun Weiguo; Luo Xiaobing; Wang Hu; Bai Lixing; Shi Miangong; Miao Lei; Zhen Zhijian; Gu Yuqin; Liu Hongjie; Zhu Zhouseng; Sun Liwei; Liao Xuehua

    2007-01-01

    The fusion mechanism of large deuterium clusters (100-1000 Atoms/per cluster) in super-intense ultra-short laser pulse field, Coulomb explosions of micro-cluster in solids, gases and Large-size clusters have been studied using the interaction of a high-intensity femtosecond laser pulses with large deuterium clusters, collision of high-quality beam of micro-cluster from 2.5 MV van de Graaff accelerator with solids, gases and large clusters. The experimental advance of the project is reported. (authors)

  15. 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.

  16. Simultaneous, single-pulse, synchrotron x-ray imaging and diffraction under gas gun loading

    Energy Technology Data Exchange (ETDEWEB)

    Fan, D.; Luo, S. N., E-mail: sluo@pims.ac.cn [The Peac Institute of Multiscale Sciences, Chengdu, Sichuan 610031 (China); Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Huang, J. W.; Zeng, X. L.; Li, Y.; E, J. C.; Huang, J. Y. [The Peac Institute of Multiscale Sciences, Chengdu, Sichuan 610031 (China); Sun, T.; Fezzaa, K. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Wang, Z. [Physics Division P-25, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2016-05-15

    We develop a mini gas gun system for simultaneous, single-pulse, x-ray diffraction and imaging under high strain-rate loading at the beamline 32-ID of the Advanced Photon Source. In order to increase the reciprocal space covered by a small-area detector, a conventional target chamber is split into two chambers: a narrowed measurement chamber and a relief chamber. The gas gun impact is synchronized with synchrotron x-ray pulses and high-speed cameras. Depending on a camera’s capability, multiframe imaging and diffraction can be achieved. The proof-of-principle experiments are performed on single-crystal sapphire. The diffraction spots and images during impact are analyzed to quantify lattice deformation and fracture; fracture is dominated by splitting cracks followed by wing cracks, and diffraction peaks are broadened likely due to mosaic spread. Our results demonstrate the potential of such multiscale measurements for studying high strain-rate phenomena at dynamic extremes.

  17. Pulsed neural networks consisting of single-flux-quantum spiking neurons

    International Nuclear Information System (INIS)

    Hirose, T.; Asai, T.; Amemiya, Y.

    2007-01-01

    An inhibitory pulsed neural network was developed for brain-like information processing, by using single-flux-quantum (SFQ) circuits. It consists of spiking neuron devices that are coupled to each other through all-to-all inhibitory connections. The network selects neural activity. The operation of the neural network was confirmed by computer simulation. SFQ neuron devices can imitate the operation of the inhibition phenomenon of neural networks

  18. Rise time of voltage pulses in NbN superconducting single photon detectors

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, K. V. [Moscow State Pedagogical University, 1 Malaya Pirogovskaya St., 119435 Moscow (Russian Federation); CJSC “Superconducting Nanotechnology” (Scontel), 5/22-1 Rossolimo St., 119021 Moscow (Russian Federation); National Research University Higher School of Economics, Moscow Institute of Electronics and Mathematics, 34 Tallinskaya St., 109028 Moscow (Russian Federation); Divochiy, A. V.; Karpova, U. V.; Morozov, P. V. [CJSC “Superconducting Nanotechnology” (Scontel), 5/22-1 Rossolimo St., 119021 Moscow (Russian Federation); Vakhtomin, Yu. B.; Seleznev, V. A. [Moscow State Pedagogical University, 1 Malaya Pirogovskaya St., 119435 Moscow (Russian Federation); CJSC “Superconducting Nanotechnology” (Scontel), 5/22-1 Rossolimo St., 119021 Moscow (Russian Federation); Sidorova, M. V. [Moscow State Pedagogical University, 1 Malaya Pirogovskaya St., 119435 Moscow (Russian Federation); Zotova, A. N.; Vodolazov, D. Yu. [Institute for Physics of Microstructure, Russian Academy of Sciences, GSP-105, 603950 Nizhny Novgorod (Russian Federation); Lobachevsky State University of Nizhny Novgorod, 23 Gagarin Avenue, 603950 Nizhny Novgorod (Russian Federation)

    2016-08-01

    We have found experimentally that the rise time of voltage pulse in NbN superconducting single photon detectors increases nonlinearly with increasing the length of the detector L. The effect is connected with dependence of resistance of the detector R{sub n}, which appears after photon absorption, on its kinetic inductance L{sub k} and, hence, on the length of the detector. This conclusion is confirmed by our calculations in the framework of two temperature model.

  19. Microdrilling of metals with an inexpensive and compact ultra-short-pulse fiber amplified microchip laser

    Energy Technology Data Exchange (ETDEWEB)

    Ancona, A. [Friedrich-Schiller-Universitaet Jena, Institut fuer Angewandte Physik, Jena (Germany); CNR-INFM Regional Laboratory ' LIT3' , Dipartimento Interuniversitario di Fisica, Bari (Italy); Nodop, D.; Limpert, J.; Nolte, S. [Friedrich-Schiller-Universitaet Jena, Institut fuer Angewandte Physik, Jena (Germany); Tuennermann, A. [Friedrich-Schiller-Universitaet Jena, Institut fuer Angewandte Physik, Jena (Germany); Fraunhofer Institute for Applied Optics and Precision Engineering (IOF), Jena (Germany)

    2009-01-15

    We have investigated the ultra-fast microdrilling of metals using a compact and cheap fiber amplified passively Q-switched microchip laser. This laser system delivers 100-ps pulses with repetition rates higher than 100 kHz and pulse energies up to 80 {mu}J. The ablation process has been studied on metals with quite different thermal properties (copper, carbon steel and stainless steel). The dependence of the ablation depth per pulse on the pulse energy follows the same logarithmic scaling laws governing laser ablation with sub-picosecond pulses. Structures ablated with 100-ps laser pulses are accompanied only by a thin layer of melted material. Despite this, results with a high level of precision are obtained when using the laser trepanning technique. This simple and affordable laser system could be a valid alternative to nanosecond laser sources for micromachining applications. (orig.)

  20. Preliminary design of a 100 Hz, 350 kV short pulse generator

    International Nuclear Information System (INIS)

    Rohwein, G.J.; Buttram, M.T.

    1977-06-01

    This report describes a 350 kV pulser designed to generate 100 ns square pulses with 300 joules total energy at a pulse repetition frequency of 100 per second. This design incorporates a transformer charged helical coaxial pulse forming line. The considerations leading to this design are presented together with results from prototype experiments. The pulser which is presently in the construction and testing phase is described in detail. The pulser will be used for electron beam acceleration

  1. Single-pulse x-ray diffraction using polycapillary optics for in situ dynamic diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Maddox, B. R., E-mail: maddox3@llnl.gov; Akin, M. C., E-mail: akin1@llnl.gov; Teruya, A.; Hunt, D.; Hahn, D.; Cradick, J. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Morgan, D. V. [National Security Technologies LLC, Los Alamos, New Mexico 87544 (United States)

    2016-08-15

    Diagnostic use of single-pulse x-ray diffraction (XRD) at pulsed power facilities can be challenging due to factors such as the high flux and brightness requirements for diffraction and the geometric constraints of experimental platforms. By necessity, the x-ray source is usually positioned very close, within a few inches of the sample. On dynamic compression platforms, this puts the x-ray source in the debris field. We coupled x-ray polycapillary optics to a single-shot needle-and-washer x-ray diode source using a laser-based alignment scheme to obtain high-quality x-ray diffraction using a single 16 ns x-ray pulse with the source >1 m from the sample. The system was tested on a Mo sample in reflection geometry using 17 keV x-rays from a Mo anode. We also identified an anode conditioning effect that increased the x-ray intensity by 180%. Quantitative measurements of the x-ray focal spot produced by the polycapillary yielded a total x-ray flux on the sample of 3.3 ± 0.5 × 10{sup 7} molybdenum Kα photons.

  2. A Single-Chip CMOS Pulse Oximeter with On-Chip Lock-In Detection

    Directory of Open Access Journals (Sweden)

    Diwei He

    2015-07-01

    Full Text Available Pulse oximetry is a noninvasive and continuous method for monitoring the blood oxygen saturation level. This paper presents the design and testing of a single-chip pulse oximeter fabricated in a 0.35 µm CMOS process. The chip includes photodiode, transimpedance amplifier, analogue band-pass filters, analogue-to-digital converters, digital signal processor and LED timing control. The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1% with the circuit simulations. With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise. In a breath hold and release experiment the single chip sensor demonstrates consistent and comparable performance to commercial pulse oximetry devices with a mean of 1.2% difference. The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

  3. A Single-Chip CMOS Pulse Oximeter with On-Chip Lock-In Detection.

    Science.gov (United States)

    He, Diwei; Morgan, Stephen P; Trachanis, Dimitrios; van Hese, Jan; Drogoudis, Dimitris; Fummi, Franco; Stefanni, Francesco; Guarnieri, Valerio; Hayes-Gill, Barrie R

    2015-07-14

    Pulse oximetry is a noninvasive and continuous method for monitoring the blood oxygen saturation level. This paper presents the design and testing of a single-chip pulse oximeter fabricated in a 0.35 µm CMOS process. The chip includes photodiode, transimpedance amplifier, analogue band-pass filters, analogue-to-digital converters, digital signal processor and LED timing control. The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations. With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise. In a breath hold and release experiment the single chip sensor demonstrates consistent and comparable performance to commercial pulse oximetry devices with a mean of 1.2% difference. The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

  4. Anisotropy effect of crater formation on single crystal silicon surface under intense pulsed ion beam irradiation

    Science.gov (United States)

    Shen, Jie; Yu, Xiao; Zhang, Jie; Zhong, Haowen; Cui, Xiaojun; Liang, Guoying; Yu, Xiang; Huang, Wanying; Shahid, Ijaz; Zhang, Xiaofu; Yan, Sha; Le, Xiaoyun

    2018-04-01

    Due to the induced extremely fast thermal and dynamic process, Intense Pulsed Ion Beam (IPIB) is widely applied in material processing, which can bring enhanced material performance and surface craters as well. To investigate the craters' formation mechanism, a specific model was built with Finite Element Methods (FEM) to simulate the thermal field on irradiated single crystal silicon. The direct evidence for the existence of the simulated 6-fold rotational symmetric thermal distribution was provided by electron microscope images obtained on single crystal silicon. The correlation of the experiment and simulation is of great importance to understand the interaction between IPIB and materials.

  5. Single-shot femtosecond-pulsed phase-shifting digital holography.

    Science.gov (United States)

    Kakue, Takashi; Itoh, Seiya; Xia, Peng; Tahara, Tatsuki; Awatsuji, Yasuhiro; Nishio, Kenzo; Ura, Shogo; Kubota, Toshihiro; Matoba, Osamu

    2012-08-27

    Parallel phase-shifting digital holography is capable of three-dimensional measurement of a dynamically moving object with a single-shot recording. In this letter, we demonstrated a parallel phase-shifting digital holography using a single femtosecond light pulse whose central wavelength and temporal duration were 800 nm and 96 fs, respectively. As an object, we set spark discharge in atmospheric pressure air induced by applying a high voltage to between two electrodes. The instantaneous change in phase caused by the spark discharge was clearly reconstructed. The reconstructed phase image shows the change of refractive index of air was -3.7 × 10(-4).

  6. Expansion-limited aggregation of nanoclusters in a single-pulse laser-produced plume

    International Nuclear Information System (INIS)

    Gamaly, E. G.; Madsen, N. R.; Rode, A. V.; Golberg, D.

    2009-01-01

    Formation of carbon nanoclusters in a single-laser-pulse created ablation plume was studied both in vacuum and in a noble gas environment at various pressures. The developed theory provides cluster radius dependence on combination of laser parameters, properties of ablated material, and type and pressure of an ambient gas in agreement with experiments. The experiments were performed on carbon nanoclusters formed by laser ablation of graphite targets with 12 picosecond 532 nm laser pulses at MHz-range repetition rate in a broad range of ambient He, Ar, Kr, and Xe gas pressures from 2x10 -2 to 1500 Torr. The experimental results confirmed our theoretical prediction that the average size of the nanoparticles depends weakly on the type of the ambient gas used, and is determined exclusively by the single laser pulse parameters even at the repetition rate as high as 28 MHz with the time gap 36 ns between the pulses. The most important finding relates to the fact that in vacuum the cluster size is mainly determined by hydrodynamic expansion of the plume while in the ambient gas it is controlled by atomic diffusion in the gas. We demonstrate that the ultrashort pulses can be used for production of clusters with the size less than the critical value, which separates the particles with properties drastically different from those of a material in a bulk. The presented results of experiments on formation of carbon nanoclusters are in close agreement with the theoretical scaling. The developed theory is applicable for cluster formation from any monatomic material, such as silicon for example.

  7. New developments in short-pulse eye safe lasers pay the way for future LADARs and 3D mapping performances

    Science.gov (United States)

    Pasmanik, Guerman; Latone, Kevin; Shilov, Alex; Shklovsky, Eugeni; Spiro, Alex; Tiour, Larissa

    2005-06-01

    We have demonstrated that direct excitation of 3rd Stokes Raman emission in crystal can produce short (few nanosecond) eye-safe pulses. Produced beam has very high quality and the pulse energy can be as high as tens of millijoules. For pulsed diode pumped solid state lasers the demonstrated repetition rate was 250 Hz but higher repetition rates are certainly achievable. It is important that tested schemes do not have strict requirements on laser pump parameters, namely beam divergence and frequency bandwidth. The obtained results are very relevant to the development of eye-safe lasers, such as the new generation of rangefinders, target designators, and laser tracking and pin-pointing devices, as well as remote 2D and 3D imaging systems.

  8. Diagnosis of a short-pulse dielectric barrier discharge at atmospheric pressure in helium with hydrogen-methane admixtures

    Science.gov (United States)

    Nastuta, A. V.; Pohoata, V.; Mihaila, I.; Topala, I.

    2018-04-01

    In this study, we present results from electrical, optical, and spectroscopic diagnosis of a short-pulse (250 ns) high-power impulse (up to 11 kW) dielectric barrier discharge at atmospheric pressure running in a helium/helium-hydrogen/helium-hydrogen-methane gas mixture. This plasma source is able to generate up to 20 cm3 of plasma volume, pulsed in kilohertz range. The plasma spatio-temporal dynamics are found to be developed in three distinct phases. All the experimental observations reveal a similar dynamic to medium power microsecond barrier discharges, although the power per pulse and current density are up to two orders of magnitude higher than the case of microsecond barrier discharges. This might open the possibility for new applications in the field of gas or surface processing, and even life science. These devices can be used in laboratory experiments relevant for molecular astrophysics.

  9. Thin film beam splitter multiple short pulse generation for enhanced Ni-like Ag x-ray laser emission.

    Science.gov (United States)

    Cojocaru, Gabriel V; Ungureanu, Razvan G; Banici, Romeo A; Ursescu, Daniel; Delmas, Olivier; Pittman, Moana; Guilbaud, Olivier; Kazamias, Sophie; Cassou, Kevin; Demailly, Julien; Neveu, Olivier; Baynard, Elsa; Ros, David

    2014-04-15

    An alternative, novel multiple pulse generation scheme was implemented directly after the optical compressor output of an x-ray pump laser. The new method uses a polarization sensitive thin film beam splitter and a half-wavelength wave plate for tuning the energy ratio in the multiple short pulses. Based on this method, an extensive study was made of the running parameters for a grazing incidence pumped silver x-ray laser (XRL) pumped with a long pulse of 145 mJ in 6 ns at 532 nm and up to 1.45 J in few picoseconds at 810 nm. Fivefold enhancement in the emission of the silver XRL was demonstrated using the new pump method.

  10. Short-term heat load forecasting for single family houses

    DEFF Research Database (Denmark)

    Bacher, Peder; Madsen, Henrik; Nielsen, Henrik Aalborg

    2013-01-01

    This paper presents a method for forecasting the load for space heating in a single-family house. The forecasting model is built using data from sixteen houses located in Sønderborg, Denmark, combined with local climate measurements and weather forecasts. Every hour the hourly heat load for each...... house the following two days is forecasted. The forecast models are adaptive linear time-series models and the climate inputs used are: ambient temperature, global radiation and wind speed. A computationally efficient recursive least squares scheme is used. The models are optimized to fit the individual...... noise and that practically all correlation to the climate variables are removed. Furthermore, the results show that the forecasting errors mainly are related to: unpredictable high frequency variations in the heat load signal (predominant only for some houses), shifts in resident behavior patterns...

  11. Short term memory for single surface features and bindings in ageing: A replication study.

    Science.gov (United States)

    Isella, Valeria; Molteni, Federica; Mapelli, Cristina; Ferrarese, Carlo

    2015-06-01

    In the present study we replicated a previous experiment investigating visuo-spatial short term memory binding in young and older healthy individuals, in the attempt to verify the pattern of impairment that can be observed in normal elderly for short term memory for single items vs short term memory for bindings. Assessing a larger sample size (25 young and 25 older subjects), using a more appropriate measure of accuracy for a change detection task (A'), and adding the evaluation of speed of performance, we confirmed that old normals show a decline in short term memory for bindings of shape and colour that is of comparable extent, and not major, to the decline in memory for single shapes and single colours. The absence of a specific deficit of short term memory for conjunctions of surface features seems to distinguish cognitive ageing from Alzheimer's Disease. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Steady-state pulses and superradiance in short-wavelength, swept-gain amplifiers

    International Nuclear Information System (INIS)

    Bonifacio, R.; Hopf, F.A.; Meystre, P.; Scully, M.O.

    1975-01-01

    The steady-state behavior of amplifiers in which the excitation is swept at the speed of light is discussed in the semiclassical approximation. In the present work the case where the decay time of the population is comparable to that of the polarization is examined. Pulse propagation is shown to obey a generalized sine-Gordon equation which contains the effects of atomic relaxations. The analytical expression of the steady-state pulses (SSP) gives two threshold conditions. In the region of limited gain the SSP is a broad pulse with small area which can be obtained by small signal theory. In the second region of high gain the SSP is the superradiant π pulse. Its pulse power is not limited as in usual superradiant theory because, as is shown, for a swept excitation the cooperation-length limit does not exist

  13. Testing of Commercial Milk Production Technology Using A Combination of High Temperature Short Time and Pulsed Electric Field

    OpenAIRE

    Hadi A; Widjanarko SB; Kusnadi J

    2016-01-01

    The development of milk processing technology has grown excessively, and it contains advantage and disadvantage. This study used mixed between PEF (Pulsed Electric Field) and High Temperature Short Time (HTST) to produce milk processed product which is effective and efficient in killing milk microorganism without changing its color, scent, and nutrient content of processed product, therefore producing commercial sterile milk product in accord with milk Indonesian National Standard (SNI). The ...

  14. A single-probe heat pulse method for estimating sap velocity in trees.

    Science.gov (United States)

    López-Bernal, Álvaro; Testi, Luca; Villalobos, Francisco J

    2017-10-01

    Available sap flow methods are still far from being simple, cheap and reliable enough to be used beyond very specific research purposes. This study presents and tests a new single-probe heat pulse (SPHP) method for monitoring sap velocity in trees using a single-probe sensor, rather than the multi-probe arrangements used up to now. Based on the fundamental conduction-convection principles of heat transport in sapwood, convective velocity (V h ) is estimated from the temperature increase in the heater after the application of a heat pulse (ΔT). The method was validated against measurements performed with the compensation heat pulse (CHP) technique in field trees of six different species. To do so, a dedicated three-probe sensor capable of simultaneously applying both methods was produced and used. Experimental measurements in the six species showed an excellent agreement between SPHP and CHP outputs for moderate to high flow rates, confirming the applicability of the method. In relation to other sap flow methods, SPHP presents several significant advantages: it requires low power inputs, it uses technically simpler and potentially cheaper instrumentation, the physical damage to the tree is minimal and artefacts caused by incorrect probe spacing and alignment are removed. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  15. Q-switched all-fiber laser with short pulse duration based on tungsten diselenide

    Science.gov (United States)

    Li, Wenyi; OuYang, Yuyi; Ma, Guoli; Liu, Mengli; Liu, Wenjun

    2018-05-01

    Fiber lasers are widely used in industrial processing, sensing, medical and communications applications due to their simple structure, good stability and low cost. With the rapid development of fiber lasers and the sustained improvement of industrial laser quality requirements, researchers in ultrafast optics focus on how to get laser pulses with high output power and narrow pulse duration. Q-switched technology is one of the most effective techniques to generate ultrashort pulses. In this paper, a tungsten diselenide saturable absorber with 16.82% modulation depth is prepared by chemical vapor deposition. Experimental results show that when the pump power changes from 115.7 mW to 630 mW, the all-fiber laser can achieve a stable Q-switched pulse output. The repetition rate of the output pulse varies from 80.32 kHz to 204.2 kHz, the pulse duration is 581 ns, the maximum output power is 17.1 mW and the maximum pulse energy is 83.7 nJ. Results in this paper show that tungsten diselenide can be applied to ultrafast optics, which is a kind of saturable absorption material with excellent properties.

  16. Self-phase modulation of a single-cycle terahertz pulse by nonlinear free-carrier response in a semiconductor

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias C.

    2012-01-01

    We investigate the self-phase modulation (SPM) of a single-cycle terahertz pulse in a semiconductor, using bulk n-GaAs as a model system. The SPM arises from the heating of free electrons in the electric field of the terahertz pulse, leading to an ultrafast reduction of the plasma frequency...

  17. 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.

  18. Pulse Propagation in Presence of Polarization Mode Dispersion and Chromatic Dispersion in Single Mode Fibers

    Directory of Open Access Journals (Sweden)

    Hassan Abid Yasser

    2013-01-01

    Full Text Available The presence of (first and second orders polarization mode dispersion (PMD, chromatic dispersion, and initial chirp makes effects on the propagated pulses in single mode fiber. Nowadays, there is not an accurate mathematical formula that describes the pulse shape in the presence of these effects. In this work, a theoretical study is introduced to derive a generalized formula. This formula is exactly approached to mathematical relations used in their special cases. The presence of second-order PMD (SOPMD will not affect the orthogonality property between the principal states of polarization. The simulation results explain that the interaction of the SOPMD components with the conventional effects (chromatic dispersion and chirp will cause a broadening/narrowing and shape distortion. This changes depend on the specified values of SOPMD components as well as the present conventional parameters.

  19. Direct observation of short-circuit diffusion during the formation of a single cupric oxide nanowire

    International Nuclear Information System (INIS)

    Cheng, C-L; Ma, Y-R; Chou, M H; Huang, C Y; Yeh, V; Wu, S Y

    2007-01-01

    Short-circuit diffusion was observed in a single CuO nanowire synthesized using a thermal oxidation method. The confocal Raman spectra of a single CuO nanowire permit direct observation of the nature of an individual CuO nanowire. The parameter order obtained from the inverse Raman B g 2 peak linewidth results in the length dependence of the linewidth and a short-circuit diffusion length of 3.3 μm. The observed structural information is also consistent with the energy dispersive x-ray spectroscopic mapping. The results confirm that the growth of CuO nanowires occurs through the short-circuit diffusion mechanism

  20. Surprise in simplicity: an unusual spectral evolution of a single pulse GRB 151006A

    Science.gov (United States)

    Basak, R.; Iyyani, S.; Chand, V.; Chattopadhyay, T.; Bhattacharya, D.; Rao, A. R.; Vadawale, S. V.

    2017-11-01

    We present a detailed analysis of GRB 151006A, the first gamma-ray burst (GRB) detected by AstroSat Cadmium-Zinc-Telluride Imager (CZTI). We study the long-term spectral evolution by exploiting the capabilities of Fermi and Swift satellites at different phases, which is complemented by the polarization measurement with the CZTI. While the light curve of the GRB in different energy bands shows a simple pulse profile, the spectrum shows an unusual evolution. The first phase exhibits a hard-to-soft evolution until ∼16-20 s, followed by a sudden increase in the spectral peak reaching a few MeV. Such a dramatic change in the spectral evolution in the case of a single pulse burst is reported for the first time. This is captured by all models we used namely, Band function, blackbody+Band and two blackbodies+power law. Interestingly, the Fermi Large Area Telescope also detects its first photon (>100 MeV) during this time. This new injection of energy may be associated with either the beginning of afterglow phase, or a second hard pulse of the prompt emission itself that, however, is not seen in the otherwise smooth pulse profile. By constructing Bayesian blocks and studying the hardness evolution we find a good evidence for a second hard pulse. The Swift data at late epochs (>T90 of the GRB) also show a significant spectral evolution consistent with the early second phase. The CZTI data (100-350 keV), though having low significance (1σ), show high values of polarization in the two epochs (77-94 per cent), in agreement with our interpretation.

  1. H{sup +}{sub 2} ionization by ultra-short electromagnetic pulses investigated through a non-perturbative Coulomb-Volkov approach

    Energy Technology Data Exchange (ETDEWEB)

    RodrIguez, V D [Departamento de Fisica, FCEyN, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina); Macri, P [Departamento de Fisica, FCEyN, Universidad de Buenos Aires, 1428 Buenos Aires (Argentina); Instituto de Astronomia y Fisica del Espacio, Consejo Nacional de Investigaciones CientIficas y Tecnicas, 1428 Buenos Aires (Argentina); Gayet, R [CELIA, Centre Lasers Intenses et Applications, UMR 5107, Unite Mixte de Recherche CNRS-CEA-Universite Bordeaux 1, Universite Bordeaux 1, 351 Cours de la Liberation, 33405 Talence Cedex (France)

    2005-08-14

    The sudden Coulomb-Volkov theoretical approximation has been shown to well describe atomic ionization by intense and ultra-short electromagnetic pulses, such as pulses generated by very fast highly-charged ions. This approach is extended here to investigate single ionization of homonuclear diatomic molecules by such pulses in the framework of one-active electron. Under particular conditions, a Young-like interference formula can approximately be factored out. Present calculations show interference effects originating from the molecular two-centre structure. Fivefold differential angular distributions of the ejected electron are studied as a function of the molecular orientation and internuclear distance. Both non-perturbative and perturbative regimes are examined. In the non-perturbative case, an interference pattern is visible but a main lobe, opposite to the electric field polarization direction, dominates the angular distribution. In contrast, in perturbation conditions the structure of interferences shows analogies to the Young-like interference pattern obtained in ionization of molecules by fast electron impacts. Finally, the strong dependence of these Young-like angular distributions on the internuclear distance is addressed.

  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. Selection of heat transfer model for describing short-pulse laser heating silica-based sensor

    International Nuclear Information System (INIS)

    Hao Xiangnan; Nie Jinsong; Li Hua; Bian Jintian

    2012-01-01

    The fundamental equations of Fourier heat transfer model and non-Fourier heat transfer model were numerically solved, with the finite difference method. The relative changes between temperature curves of the two heat transfer models were analyzed under laser irradiation with different pulse widths of 10 ns, 1 ns, 100 ps, 10 ps. The impact of different thermal relaxation time on non-Fourier model results was discussed. For pulses of pulse width less than or equal to 100 ps irradiating silicon material, the surface temperature increases slowly and carrier effect happens, which the non-Fourier model can reflect properly. As for general material, when the pulse width is less than or equal to the thermal relaxation time of material, carrier effect occurs. In this case, the non-Fourier model should be used. (authors)

  4. Neutronic studies on decoupled hydrogen moderator for a short-pulse spallation source

    International Nuclear Information System (INIS)

    Harada, Masahide; Watanabe, Noboru; Teshigawara, Makoto; Kai, Tetsuya; Ikeda, Yujiro

    2005-01-01

    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. Observation of the charge neutrality of the ions from target short-pulse laser interaction experiments

    International Nuclear Information System (INIS)

    Yasuike, Kazuhito

    2003-01-01

    Intended to simulate the early stage of the plasma (preformed plasma) formation in the higher (10 20 W cm -2 ) intensity experiments (in which the plasma density profile rules laser absorption thus conversion efficiency from laser into hot electrons, ions and x-rays) experiments using solid target were done under a peak intensity (main laser pulse) of up to ∼10 15 W cm -2 and pre-pulse and pedestal intensity of ∼10 3 times lower than main pulse. With pedestal, significant enhancement of laser absorption was observed with pedestal condition. Charge neutralization of the ions from the plasma was measured by biased charge collectors. Earlier part of the ion were almost un-neutralized in with or without pedestal condition, and the later part of the ions (≤ few keV) were partially neutralized (≥40%). These not-perfect charge neutralization results is different from the longer nano-seconds pulse experimental results. (author)

  6. Short Pulsed Laser Methods for Velocimetry and Thermometry in High Enthalpy Facilities, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — A suite of pulsed laser diagnostics is proposed for studying aspects of planetary entry and Earth atmospheric reentry in arc jets. For example, dissociation of...

  7. Response of YBa2Cu3O7-δ grain-boundary junctions to short light pulses

    International Nuclear Information System (INIS)

    Kaplan, S.B.; Chi, C.C.; Chaudhari, P.; Dimos, D.; Gross, R.; Gupta, A.; Koren, G.

    1991-01-01

    The electrical response of a single YBa 2 Cu 3 O 7-δ grain-boundary junction to visible light pulses was measured. Using an autocorrelation technique with picosecond laser pulses, no fast voltage transients were observed with the junction biased just above its critical current. Apparently, there are no relaxation times in the range of 7 ps to 14 ns. Using direct time-domain measurement with nanosecond pulses, three types of junction response were recorded: a nonexponential decay of 11 μs (90 to 10 % time) at temperatures near T c ; an inverse-time dependence of the order of 0.3 μs (100 to 50 % time) in the temperature range of 4.2 to 15 K; and an exponential decay time of 0.15 μs with the sample immersed in superfluid helium

  8. Pulse laser induced change in thermal radiation from a single spherical particle on thermally bad conducting surface : an analytical solution

    International Nuclear Information System (INIS)

    Moksin, M.M.; Grozescu, V.I.; Yunus, W.M.M.; Azmi, B.Z.; Talib, Z.A.; Wahab, Z.A.

    1996-01-01

    A relatively simple analytical expression was derived that provided a description of the radius and thermal properties of a single particle from the change in grey body radiation emission subsequent to pulse laser heating of the particle

  9. Controlled light localisation and nonlinear-optical interactions of short laser pulses in holey fibres

    International Nuclear Information System (INIS)

    Fedotov, Andrei B; Zheltikov, Aleksei M; Golovan', Leonid A; Kashkarov, Pavel K; Tarasevitch, A P; Podshivalov, Alexey A; Alfimov, Mikhail V; Ivanov, Anatoliy A; Beloglazov, V I; Haus, J W; Linde, D von der

    2001-01-01

    The influence of the structure of holey-fibre cladding on the effective waveguide mode area and the spectral broadening of femtosecond pulses of titanium-sapphire and forsterite lasers is experimentally studied. These experiments demonstrate that the increase in the air-filling fraction of the holey-fibre cladding may substantially enhance the spectral broadening of laser pulses due to the increase in the degree of light localisation in the fibre core. (femtosecond technologies)

  10. 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...

  11. Multifunctional gold nanorods for selective plasmonic photothermal therapy in pancreatic cancer cells using ultra-short pulse near-infrared laser irradiation.

    Science.gov (United States)

    Patino, Tania; Mahajan, Ujjwal; Palankar, Raghavendra; Medvedev, Nikolay; Walowski, Jakob; Münzenberg, Markus; Mayerle, Julia; Delcea, Mihaela

    2015-03-12

    Gold nanorods (AuNRs) have attracted considerable attention in plasmonic photothermal therapy for cancer treatment by exploiting their selective and localized heating effect due to their unique photophysical properties. Here we describe a strategy to design a novel multifunctional platform based on AuNRs to: (i) specifically target the adenocarcinoma MUC-1 marker through the use of the EPPT-1 peptide, (ii) enhance cellular uptake through a myristoylated polyarginine peptide (MPAP) and (iii) selectively induce cell death by ultra-short near infrared laser pulses. We used a biotin-avidin based approach to conjugate EPPT-1 and MPAP to AuNRs. Dual-peptide (EPPT-1+MPAP) labelled AuNRs showed a significantly higher uptake by pancreatic ductal adenocarcinoma cells when compared to their single peptide or avidin conjugated counterparts. In addition, we selectively induced cell death by ultra-short near infrared laser pulses in small target volumes (∼1 μm3), through the creation of plasmonic nanobubbles that lead to the destruction of a local cell environment. Our approach opens new avenues for conjugation of multiple ligands on AuNRs targeting cancer cells and tumors and it is relevant for plasmonic photothermal therapy.

  12. A randomised comparative study of the short term clinical and biological effects of intravenous pulse methylprednisolone and infliximab in patients with active rheumatoid arthritis despite methotrexate treatment.

    Science.gov (United States)

    Durez, P; Nzeusseu Toukap, A; Lauwerys, B R; Manicourt, D H; Verschueren, P; Westhovens, R; Devogelaer, J-P; Houssiau, F A

    2004-09-01

    To compare the short term clinical and biological effects of intravenous (i.v.) pulse methylprednisolone (MP) and infliximab (IFX) in patients with severe active rheumatoid arthritis (RA) despite methotrexate (MTX) treatment. Patients with active RA despite MTX treatment were randomly allocated to receive a single i.v. infusion of MP (1 g) or three i.v. infusions of IFX (3 mg/kg) on weeks 0, 2, and 6. Patients were "blindly" evaluated for disease activity measures. Quality of life (QoL) was evaluated through the SF-36 health survey. Serum matrix metalloproteinase-3 (MMP-3) titres were measured at baseline, weeks 2 and 6. Compared with baseline, significant improvement was noted in all activity measures, including serum C reactive protein (CRP) titres, in the IFX group only. At week 14, 6/9 (67%) and 4/9 (44%) IFX patients met the ACR20 and 50 response criteria, while this was the case in only 1/12 (8%) and 0/12 (0%) MP patients, respectively (ptreatment, whereas some did so in the IFX group. Serum MMP-3 titres significantly decreased (41% drop) at week 6 in the IFX group, while no changes were seen in patients given MP. This short term randomised comparative study demonstrates that TNF blockade is better than MP pulse therapy in a subset of patients with severe refractory RA, with improvement in not only clinical parameters of disease activity but also biological inflammatory indices, such as serum CRP and MMP-3 titres.

  13. Single-mode pulsed dye laser pumped by using a diode-pumped Nd:YAG laser with a long pulse width

    International Nuclear Information System (INIS)

    Yi, Jong Hoon; Kim, Jin Tae; Moon, Hee Jong; Rho, Si Pyo; Han, Jae Min; Rhee, Yong Joo; Lee, Jong Min

    1999-01-01

    The lasing characteristics of a single-mode dye laser pumped by using a diode-pumped solid-state laser (DPSSL) with a high repetition rate is described. A 45-mm-long Nd:YAG rod was pumped by three CW diode arrays and it was acousto-optically Q-switched. A KTP crystal was used for intracavity frequency doubling. The pulse width of the laser ranged from 90 ns to 200 ns, depending on the diode current and the Q-switching frequency. The single-mode dye laser had a grazing incidence configuration. The pulse width of the dye laser was reduced to about 1/8 of the pumping laser pulse width. The effects of the DPSSL Q-switching frequency, the driving current, and the cavity loss on the dye laser pulse width were investigated by using a simple plane-parallel cavity. From the measured pulse width of the dye laser as a function of the reflectivity of the dye laser output coupler, we found that the cavity loss due to the frequency selection elements and the output coupler should be less than 70 % in order to avoid a drastically reduced pulse width

  14. Label-free screening of single biomolecules through resistive pulse sensing technology for precision medicine applications

    Science.gov (United States)

    Harrer, S.; Kim, S. C.; Schieber, C.; Kannam, S.; Gunn, N.; Moore, S.; Scott, D.; Bathgate, R.; Skafidas, S.; Wagner, J. M.

    2015-05-01

    Employing integrated nano- and microfluidic circuits for detecting and characterizing biological compounds through resistive pulse sensing technology is a vibrant area of research at the interface of biotechnology and nanotechnology. Resistive pulse sensing platforms can be customized to study virtually any particle of choice which can be threaded through a fluidic channel and enable label-free single-particle interrogation with the primary read-out signal being an electric current fingerprint. The ability to perform label-free molecular screening with single-molecule and even single binding site resolution makes resistive pulse sensing technology a powerful tool for analyzing the smallest units of biological systems and how they interact with each other on a molecular level. This task is at the core of experimental systems biology and in particular ‘omics research which in combination with next-generation DNA-sequencing and next-generation drug discovery and design forms the foundation of a novel disruptive medical paradigm commonly referred to as personalized medicine or precision medicine. DNA-sequencing has approached the 1000-Dollar-Genome milestone allowing for decoding a complete human genome with unmatched speed and at low cost. Increased sequencing efficiency yields massive amounts of genomic data. Analyzing this data in combination with medical and biometric health data eventually enables understanding the pathways from individual genes to physiological functions. Access to this information triggers fundamental questions for doctors and patients alike: what are the chances of an outbreak for a specific disease? Can individual risks be managed and if so how? Which drugs are available and how should they be applied? Could a new drug be tailored to an individual’s genetic predisposition fast and in an affordable way? In order to provide answers and real-life value to patients, the rapid evolvement of novel computing approaches for analyzing big data in

  15. Label-free screening of single biomolecules through resistive pulse sensing technology for precision medicine applications.

    Science.gov (United States)

    Harrer, S; Kim, S C; Schieber, C; Kannam, S; Gunn, N; Moore, S; Scott, D; Bathgate, R; Skafidas, S; Wagner, J M

    2015-05-08

    Employing integrated nano- and microfluidic circuits for detecting and characterizing biological compounds through resistive pulse sensing technology is a vibrant area of research at the interface of biotechnology and nanotechnology. Resistive pulse sensing platforms can be customized to study virtually any particle of choice which can be threaded through a fluidic channel and enable label-free single-particle interrogation with the primary read-out signal being an electric current fingerprint. The ability to perform label-free molecular screening with single-molecule and even single binding site resolution makes resistive pulse sensing technology a powerful tool for analyzing the smallest units of biological systems and how they interact with each other on a molecular level. This task is at the core of experimental systems biology and in particular 'omics research which in combination with next-generation DNA-sequencing and next-generation drug discovery and design forms the foundation of a novel disruptive medical paradigm commonly referred to as personalized medicine or precision medicine. DNA-sequencing has approached the 1000-Dollar-Genome milestone allowing for decoding a complete human genome with unmatched speed and at low cost. Increased sequencing efficiency yields massive amounts of genomic data. Analyzing this data in combination with medical and biometric health data eventually enables understanding the pathways from individual genes to physiological functions. Access to this information triggers fundamental questions for doctors and patients alike: what are the chances of an outbreak for a specific disease? Can individual risks be managed and if so how? Which drugs are available and how should they be applied? Could a new drug be tailored to an individual's genetic predisposition fast and in an affordable way? In order to provide answers and real-life value to patients, the rapid evolvement of novel computing approaches for analyzing big data in

  16. Self-pulsing in a 2 km single-mode fiber with the seed source broadened via WNS phase modulation

    Science.gov (United States)

    Zha, Congwen; Sun, Yinhong; Wang, Yanshan; Li, Tenglong; Peng, Wanjing; Ma, Yi; Zhang, Kai

    2018-03-01

    The seed source with spectral linewidth broadening via phase modulation is potential to achieve the higher output power with effective SBS suppression. However, self-pulsing from the amplifier output is harmful. In this work, we study the self-pulsing characteristics in a long single-mode fiber with lower self-pulsing threshold instead of the high power amplifier. We provide a powerful experimental support for the self-pulsing mechanism in high-power narrow-linewidth fiber lasers, which is important for further output power scaling.

  17. Single-pulse CARS based multimodal nonlinear optical microscope for bioimaging.

    Science.gov (United States)

    Kumar, Sunil; Kamali, Tschackad; Levitte, Jonathan M; Katz, Ori; Hermann, Boris; Werkmeister, Rene; Považay, Boris; Drexler, Wolfgang; Unterhuber, Angelika; Silberberg, Yaron

    2015-05-18

    Noninvasive label-free imaging of biological systems raises demand not only for high-speed three-dimensional prescreening of morphology over a wide-field of view but also it seeks to extract the microscopic functional and molecular details within. Capitalizing on the unique advantages brought out by different nonlinear optical effects, a multimodal nonlinear optical microscope can be a powerful tool for bioimaging. Bringing together the intensity-dependent contrast mechanisms via second harmonic generation, third harmonic generation and four-wave mixing for structural-sensitive imaging, and single-beam/single-pulse coherent anti-Stokes Raman scattering technique for chemical sensitive imaging in the finger-print region, we have developed a simple and nearly alignment-free multimodal nonlinear optical microscope that is based on a single wide-band Ti:Sapphire femtosecond pulse laser source. Successful imaging tests have been realized on two exemplary biological samples, a canine femur bone and collagen fibrils harvested from a rat tail. Since the ultra-broad band-width femtosecond laser is a suitable source for performing high-resolution optical coherence tomography, a wide-field optical coherence tomography arm can be easily incorporated into the presented multimodal microscope making it a versatile optical imaging tool for noninvasive label-free bioimaging.

  18. Communication: The electronic structure of matter probed with a single femtosecond hard x-ray pulse

    Directory of Open Access Journals (Sweden)

    J. Szlachetko

    2014-03-01

    Full Text Available Physical, biological, and chemical transformations are initiated by changes in the electronic configuration of the species involved. These electronic changes occur on the timescales of attoseconds (10−18 s to femtoseconds (10−15 s and drive all subsequent electronic reorganization as the system moves to a new equilibrium or quasi-equilibrium state. The ability to detect the dynamics of these electronic changes is crucial for understanding the potential energy surfaces upon which chemical and biological reactions take place. Here, we report on the determination of the electronic structure of matter using a single self-seeded femtosecond x-ray pulse from the Linac Coherent Light Source hard x-ray free electron laser. By measuring the high energy resolution off-resonant spectrum (HEROS, we were able to obtain information about the electronic density of states with a single femtosecond x-ray pulse. We show that the unoccupied electronic states of the scattering atom may be determined on a shot-to-shot basis and that the measured spectral shape is independent of the large intensity fluctuations of the incoming x-ray beam. Moreover, we demonstrate the chemical sensitivity and single-shot capability and limitations of HEROS, which enables the technique to track the electronic structural dynamics in matter on femtosecond time scales, making it an ideal probe technique for time-resolved X-ray experiments.

  19. Probability of cavitation for single ultrasound pulses applied to tissues and tissue-mimicking materials.

    Science.gov (United States)

    Maxwell, Adam D; Cain, Charles A; Hall, Timothy L; Fowlkes, J Brian; Xu, Zhen

    2013-03-01

    In this study, the negative pressure values at which inertial cavitation consistently occurs in response to a single, two-cycle, focused ultrasound pulse were measured in several media relevant to cavitation-based ultrasound therapy. The pulse was focused into a chamber containing one of the media, which included liquids, tissue-mimicking materials, and ex vivo canine tissue. Focal waveforms were measured by two separate techniques using a fiber-optic hydrophone. Inertial cavitation was identified by high-speed photography in optically transparent media and an acoustic passive cavitation detector. The probability of cavitation (P(cav)) for a single pulse as a function of peak negative pressure (p(-)) followed a sigmoid curve, with the probability approaching one when the pressure amplitude was sufficient. The statistical threshold (defined as P(cav) = 0.5) was between p(-) = 26 and 30 MPa in all samples with high water content but varied between p(-) = 13.7 and >36 MPa in other media. A model for radial cavitation bubble dynamics was employed to evaluate the behavior of cavitation nuclei at these pressure levels. A single bubble nucleus with an inertial cavitation threshold of p(-) = 28.2 megapascals was estimated to have a 2.5 nm radius in distilled water. These data may be valuable for cavitation-based ultrasound therapy to predict the likelihood of cavitation at various pressure levels and dimensions of cavitation-induced lesions in tissue. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  20. Optical design and studies of a tiled single grating pulse compressor for enhanced parametric space and compensation of tiling errors

    Science.gov (United States)

    Daiya, D.; Patidar, R. K.; Sharma, J.; Joshi, A. S.; Naik, P. A.; Gupta, P. D.

    2017-04-01

    A new optical design of tiled single grating pulse compressor has been proposed, set-up and studied. The parametric space, i.e. the laser beam diameters that can be accommodated in the pulse compressor for the given range of compression lengths, has been calculated and shown to have up to two fold enhancement in comparison to our earlier proposed optical designs. The new optical design of the tiled single grating pulse compressor has an additional advantage of self compensation of various tiling errors like longitudinal and lateral piston, tip and groove density mismatch, compared to the earlier designs. Experiments have been carried out for temporal compression of 650 ps positively chirped laser pulses, at central wavelength 1054 nm, down to 235 fs in the tiled grating pulse compressor set up with the proposed design. Further, far field studies have been performed to show the desired compensation of the tiling errors takes place in the new compressor.

  1. Electron tunnelling through single azurin molecules can be on/off switched by voltage pulses

    Energy Technology Data Exchange (ETDEWEB)

    Baldacchini, Chiara [Biophysics and Nanoscience Centre, DEB-CNISM, Università della Tuscia, I-01100 Viterbo (Italy); Institute of Agro-Environmental and Forest Biology, CNR, I-05010 Porano (Italy); Kumar, Vivek; Bizzarri, Anna Rita; Cannistraro, Salvatore, E-mail: cannistr@unitus.it [Biophysics and Nanoscience Centre, DEB-CNISM, Università della Tuscia, I-01100 Viterbo (Italy)

    2015-05-04

    Redox metalloproteins are emerging as promising candidates for future bio-optoelectronic and nano-biomemory devices, and the control of their electron transfer properties through external signals is still a crucial task. Here, we show that a reversible on/off switching of the electron current tunnelling through a single protein can be achieved in azurin protein molecules adsorbed on gold surfaces, by applying appropriate voltage pulses through a scanning tunnelling microscope tip. The observed changes in the hybrid system tunnelling properties are discussed in terms of long-sustained charging of the protein milieu.

  2. A low-cost multichannel pulse-height analyzer PHA 256 using single-chip microcomputer

    International Nuclear Information System (INIS)

    Koehler, M.; Meiling, W.

    1985-01-01

    The PHA 256 multichannel analyzer on the base of the U8820 single-chip microcomputer applied for radiation measurements, for example in monitoring systems with scintillation detectors, is described. The analyzer contains a power supply unit and 7 boards, namely, the processor board; data and program memory; 8-bit analog-to-digital converter; driver to display device; keyboard with 23 function keys; pulse amplifier and high-voltage supply (up to 2 kV). Software used provides preprocessing of spectra supported by following functions: addition and subtraction of different spectra, spectrum monitoring by use of a 5-point-algorithm, calculation of peak areas with linearly interpolated background

  3. Generation efficiency of single-photon current pulses in the Geiger mode of silicon avalanche photodiodes

    International Nuclear Information System (INIS)

    Verkhovtseva, A. V.; Gergel, V. A.

    2009-01-01

    Statistical fluctuations of the avalanche's multiplication efficiency were studied as applied to the single-photon (Geiger) mode of avalanche photodiodes. The distribution function of partial multiplication factors with an anomalously wide (of the order of the average) dispersion was obtained. Expressions for partial feedback factors were derived in terms of the average gain and the corresponding dependences on the diode's overvoltage were calculated. Final expressions for the photon-electric pulse's conversion were derived by averaging corresponding formulas over the coordinate of initiating photoelectron generation using the functions of optical photon absorption in silicon.

  4. Self-pulsing and chaos in inhomogeneously broadened single mode lasers

    Energy Technology Data Exchange (ETDEWEB)

    Graham, R; Cho, Y

    1983-08-01

    A four-dimensional model and a six-dimensional model describing the self-pulsing instabilities and chaotic dynamics of inhomogeneously broadened single-mode lasers are derived as the first two steps of an infinite hierarchy of approximations increasing in accuracy and complexity. The results of a linear stability analysis of the time-independent states and some numerical solutions are given to show the various types of dynamic behavior which can occur in these models. The dynamic behavior is found to be much more complex than in the homogeneously broadened case and is obtained under physically more realistic conditions. 10 references.

  5. 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.

  6. Using a short-pulse diffraction-limited laser beam to probe filamentation of a random phase plate smoothed beam

    International Nuclear Information System (INIS)

    Kline, J. L.; Montgomery, D. S.; Flippo, K. A.; Johnson, R. P.; Rose, H. A.; Shimada, T.; Williams, E. A.

    2008-01-01

    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 deg. angle with respect to the RPP interaction beam. The density and temperature fluctuations are quasistatic on the time scale of the SPLP (∼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.

  7. 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.

  8. Stable polarization short pulse passively Q-switched monolithic microchip laser with [110] cut Cr4+:YAG

    International Nuclear Information System (INIS)

    Wang, Y; Gong, M; Yan, P; Huang, L; Li, D

    2009-01-01

    A monolithic Nd:YAG microchip laser with [110] cut Cr 4+ :YAG is presented. The output beam is linearly polarized with polarization ratio higher than 100:1. The polarization direction is stable, independent of pump power, crystal temperature, LD temperature. In single longitudinal mode operation, stable 259 ps pulses at 2.5 kHz with 82 kW peak power and diffraction limited beam mode are output. With a simple and compact one-pass Nd:YVO 4 amplifier, 144 kW peak power is achieved. Single longitudinal and fundamental transverse mode is kept after passing through the amplifier stage. The microchip laser can be operated in two longitudinal modes with two sets of output pulses by increasing the pump power

  9. Enhanced self-magnetic field by atomic polarization in partially stripped plasma produced by a short and intense laser pulse

    International Nuclear Information System (INIS)

    Hu Qianglin; Liu Shibing; Jiang, Y.J.; Zhang Jie

    2005-01-01

    The enhancement and redistribution of a self-generated quasistatic magnetic field, due to the presence of the polarization field induced by partially ionized atoms, are analytically revealed when a linearly polarized intense and short pulse laser propagates in a partially stripped plasma with higher density. In particular, the shorter wavelength of the laser pulse can evidently intensify the amplitude of the magnetic field. These enhancement and redistribution of the magnetic field are considered physically as a result of the competition of the electrostatic field (electron-ion separation) associated with the plasma wave, the atomic polarization field, and the pondoromotive potential associated with the laser field. This competition leads to the generation of a positive, large amplitude magnetic field in the zone of the pulse center, which forms a significant difference in partially and fully stripped plasmas. The numerical result shows further that the magnetic field is resonantly modulated by the plasma wave when the pulse length is the integer times the plasma wavelength. This apparently implies that the further enhancement and restructure of the large amplitude self-magnetic field can evidently impede the acceleration and stable transfer of the hot-electron beam

  10. Relativistic acceleration and retardation effects on photoemission of intense electron short pulses, in RF-FEL photoinjectors

    International Nuclear Information System (INIS)

    Dolique, J.M.; Coacolo, M.

    1991-01-01

    In high-power free electron lasers, self-field effects in the electron beam are often the most important phenomenon on which the beam quality depends. These effects are generally conceived as space-charge effects, and described by a Poisson equation in a beam frame. In RF-FEL photoinjectors, the electrons of the intense short pulse produced by laser irradiation are submitted, just after their photoemission, to such a strong acceleration that relativistic acceleration and retardation effects are discussed, from the rigorous calculation of the Lienard-Wiechert velocity- and acceleration electric and magnetic fields, as a function of RF-electric field and beam parameters. The beam pulse is assumed to be axisymmetric, with a constant photoemitted current density. Consequences for the maximum current density that can be extracted are considered (the 'self-field limit,' a name more appropriate than 'space-charge limit' for the present conditions where electro-dynamic phenomena play an important role)

  11. Single-photon Coulomb explosion of methanol using broad bandwidth ultrafast EUV pulses.

    Science.gov (United States)

    Luzon, Itamar; Jagtap, Krishna; Livshits, Ester; Lioubashevski, Oleg; Baer, Roi; Strasser, Daniel

    2017-05-31

    Single-photon Coulomb explosion of methanol is instigated using the broad bandwidth pulse achieved through high-order harmonics generation. Using 3D coincidence fragment imaging of one molecule at a time, the kinetic energy release (KER) and angular distributions of the products are measured in different Coulomb explosion (CE) channels. Two-body CE channels breaking either the C-O or the C-H bonds are described as well as a proton migration channel forming H 2 O + , which is shown to exhibit higher KER. The results are compared to intense-field Coulomb explosion measurements in the literature. The interpretation of broad bandwidth single-photon CE data is discussed and supported by ab initio calculations of the predominant C-O bond breaking CE channel. We discuss the importance of these findings for achieving time resolved imaging of ultrafast dynamics.

  12. Fabrication and optimization of the copper halide Laser's comparison of the double-discharge (Cu Cl) with the single-pulse operation (Cu Br)

    International Nuclear Information System (INIS)

    Sajad, B.; Behrozinia, S.; Nikzad, P.; Bassam, M. A.

    2009-01-01

    In this paper, the fabrication of a double-pulse copper chloride laser was investigated to study the effect of various parameters such as buffer gas pressure, temperature, and the delay time between two electrical discharge pulses, on laser output power. Moreover, a single-pulse copper bromide laser was fabricated to optimize the laser output power versus temperature, buffer gas pressure, and electrical input power and discharge frequency. The comparison of the results in single-pulse and double-pulse excitation indicates that the former is easier in operation and more power stability can be achieved using single pulse excitation.

  13. Time-resolved plasma spectroscopy of thin foils heated by a relativistic-intensity short-pulse laser

    International Nuclear Information System (INIS)

    Audebert, P.; Gauthier, J.-C.; Shepherd, R.; Fournier, K.B.; Price, D.; Lee, R.W.; Springer, P.; Peyrusse, O.; Klein, L.

    2002-01-01

    Time-resolved K-shell x-ray spectra are recorded from sub-100 nm aluminum foils irradiated by 150-fs laser pulses at relativistic intensities of Iλ 2 =2x10 18 W μm 2 /cm 2 . The thermal penetration depth is greater than the foil thickness in these targets so that uniform heating takes place at constant density before hydrodynamic motion occurs. The high-contrast, high-intensity laser pulse, broad spectral band, and short time resolution utilized in this experiment permit a simplified interpretation of the dynamical evolution of the radiating matter. The observed spectrum displays two distinct phases. At early time, ≤500 fs after detecting target emission, a broad quasicontinuous spectral feature with strong satellite emission from multiply excited levels is seen. At a later time, the He-like resonance line emission is dominant. The time-integrated data is in accord with previous studies with time resolution greater than 1 ps. The early time satellite emission is shown to be a signature of an initial large area, high density, low-temperature plasma created in the foil by fast electrons accelerated by the intense radiation field in the laser spot. We conclude that, because of this early time phenomenon and contrary to previous predictions, a short, high-intensity laser pulse incident on a thin foil does not create a uniform hot and dense plasma. The heating mechanism has been studied as a function of foil thickness, laser pulse length, and intensity. In addition, the spectra are found to be in broad agreement with a hydrodynamic expansion code postprocessed by a collisional-radiative model based on superconfiguration average rates and on the unresolved transition array formalism

  14. Can a single pulse transcranial magnetic stimulation targeted to the motor cortex interrupt pain processing?

    Science.gov (United States)

    Kisler, Lee-Bareket; Gurion, Ilan; Granovsky, Yelena; Sinai, Alon; Sprecher, Elliot; Shamay-Tsoory, Simone; Weissman-Fogel, Irit

    2018-01-01

    The modulatory role of the primary motor cortex (M1), reflected by an inhibitory effect of M1-stimulation on clinical pain, motivated us to deepen our understanding of M1's role in pain modulation. We used Transcranial Magnetic Stimulation (TMS)-induced virtual lesion (VL) to interrupt with M1 activity during noxious heat pain. We hypothesized that TMS-VL will effect experimental pain ratings. Three VL protocols were applied consisting of single-pulse TMS to transiently interfere with right M1 activity: (1) VLM1- TMS applied to 11 subjects, 20 msec before the individual's first pain-related M1 peak activation, as determined by source analysis (sLORETA), (2) VL-50 (N = 16; TMS applied 50 ms prior to noxious stimulus onset), and (3) VL+150 (N = 16; TMS applied 150 ms after noxious stimulus onset). Each protocol included 3 conditions ('pain-alone', ' TMS-VL', and 'SHAM-VL'), each consisted of 30 noxious heat stimuli. Pain ratings were compared, in each protocol, for TMS-VL vs. SHAM-VL and vs. pain-alone conditions. Repeated measures analysis of variance, corrected for multiple comparisons revealed no significant differences in the pain ratings between the different conditions within each protocol. Therefore, our results from this exploratory study suggest that a single pulse TMS-induced VL that is targeted to M1 failed to interrupt experimental pain processing in the specific three stimulation timing examined here.

  15. Single-mode pulsed dye laser pumped by using a diode-pumped Nd:YAG laser with a long pulse width

    CERN Document Server

    Yi, J H; Moon, H J; Rho, S P; Han, J M; Rhee, Y J; Lee, J M

    1999-01-01

    The lasing characteristics of a single-mode dye laser pumped by using a diode-pumped solid-state laser (DPSSL) with a high repetition rate is described. A 45-mm-long Nd:YAG rod was pumped by three CW diode arrays and it was acousto-optically Q-switched. A KTP crystal was used for intracavity frequency doubling. The pulse width of the laser ranged from 90 ns to 200 ns, depending on the diode current and the Q-switching frequency. The single-mode dye laser had a grazing incidence configuration. The pulse width of the dye laser was reduced to about 1/8 of the pumping laser pulse width. The effects of the DPSSL Q-switching frequency, the driving current, and the cavity loss on the dye laser pulse width were investigated by using a simple plane-parallel cavity. From the measured pulse width of the dye laser as a function of the reflectivity of the dye laser output coupler, we found that the cavity loss due to the frequency selection elements and the output coupler should be less than 70 % in order to avoid a drast...

  16. Damage threshold of lithium niobate crystal under single and multiple femtosecond laser pulses: theoretical and experimental study

    International Nuclear Information System (INIS)

    Meng, Qinglong; Zhang, Bin; Zhong, Sencheng; Zhu, Liguo

    2016-01-01

    The damage threshold of lithium niobate crystal under single and multiple femtosecond laser pulses has been studied theoretically and experimentally. Firstly, the model for the damage threshold prediction of crystal materials based on the improved rate equation has been proposed. Then, the experimental measure method of the damage threshold of crystal materials has been given in detail. On the basis, the variation of the damage threshold of lithium niobate crystal with the pulse duration has also been analyzed quantitatively. Finally, the damage threshold of lithium niobate crystal under multiple laser pulses has been measured and compared to the theoretical results. The results show that the transmittance of lithium niobate crystal is almost a constant when the laser pulse fluence is relative low, whereas it decreases linearly with the increase in the laser pulse fluence below the damage threshold. The damage threshold of lithium niobate crystal increases with the increase in the duration of the femtosecond laser pulse. And the damage threshold of lithium niobate crystal under multiple laser pulses is obviously lower than that irradiated by a single laser pulse. The theoretical data fall in good agreement with the experimental results. (orig.)

  17. Long-distance propagation of intense short laser pulse in air

    International Nuclear Information System (INIS)

    Yu Wei; Yu, M.Y.; Zhang, J.; Qian, L.J.; Yuan, X.; Lu, P.X.; Li, R.X.; Sheng, Z.M.; Liu, J.R.; Xu, Z.Z.

    2004-01-01

    Long-distance propagation of intense laser pulse in air is reconsidered analytically by generalizing the analogy between the laser spotsize and the orbit of a classical particle. It is shown that multiphoton ionization introduces unique features to the laser-air interaction, thereby enabling the long-distance behavior. Several interesting characteristics of the latter are pointed out

  18. Efficient coupling of high intensity short laser pulses into snow clusters

    Science.gov (United States)

    Palchan, T.; Pecker, S.; Henis, Z.; Eisenmann, S.; Zigler, A.

    2007-01-01

    Measurements of energy absorption of high intensity laser pulses in snow clusters are reported. Targets consisting of sapphire coated with snow nanoparticles were found to absorb more than 95% of the incident light compared to 50% absorption in flat sapphire targets.

  19. 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...

  20. Short Peptides Enhance Single Cell Adhesion and Viability onMicroarrays

    Energy Technology Data Exchange (ETDEWEB)

    Veiseh, Mandana; Veiseh, Omid; Martin, Michael C.; Asphahani,Fareid; Zhang, Miqin

    2007-01-19

    Single cell patterning holds important implications forbiology, biochemistry, biotechnology, medicine, and bioinformatics. Thechallenge for single cell patterning is to produce small islands hostingonly single cells and retaining their viability for a prolonged period oftime. This study demonstrated a surface engineering approach that uses acovalently bound short peptide as a mediator to pattern cells withimproved single cell adhesion and prolonged cellular viabilityon goldpatterned SiO2 substrates. The underlying hypothesis is that celladhesion is regulated bythe type, availability, and stability ofeffective cell adhesion peptides, and thus covalently bound shortpeptides would promote cell spreading and, thus, single cell adhesion andviability. The effectiveness of this approach and the underlyingmechanism for the increased probability of single cell adhesion andprolonged cell viability by short peptides were studied by comparingcellular behavior of human umbilical cord vein endothelial cells on threemodelsurfaces whose gold electrodes were immobilized with fibronectin,physically adsorbed Arg-Glu-Asp-Val-Tyr, and covalently boundLys-Arg-Glu-Asp-Val-Tyr, respectively. The surface chemistry and bindingproperties were characterized by reflectance Fourier transform infraredspectroscopy. Both short peptides were superior to fibronectin inproducing adhesion of only single cells, whereas the covalently boundpeptide also reduced apoptosis and necrosisof adhered cells. Controllingcell spreading by peptide binding domains to regulate apoptosis andviability represents a fundamental mechanism in cell-materialsinteraction and provides an effective strategy in engineering arrays ofsingle cells.

  1. Analytical model for electromagnetic radiation from a wakefield excited by intense short laser pulses in an unmagnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Chen Ziyu; Chen Shi; Dan Jiakun; Li Jianfeng; Peng Qixian, E-mail: ziyuch@gmail.com [Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900 (China)

    2011-10-15

    A simple one-dimensional analytical model for electromagnetic emission from an unmagnetized wakefield excited by an intense short-pulse laser in the nonlinear regime has been developed in this paper. The expressions for the spectral and angular distributions of the radiation have been derived. The model suggests that the origin of the radiation can be attributed to the violent sudden acceleration of plasma electrons experiencing the accelerating potential of the laser wakefield. The radiation process could help to provide a qualitative interpretation of existing experimental results, and offers useful information for future laser wakefield experiments.

  2. Analytical model for electromagnetic radiation from a wakefield excited by intense short laser pulses in an unmagnetized plasma

    International Nuclear Information System (INIS)

    Chen Ziyu; Chen Shi; Dan Jiakun; Li Jianfeng; Peng Qixian

    2011-01-01

    A simple one-dimensional analytical model for electromagnetic emission from an unmagnetized wakefield excited by an intense short-pulse laser in the nonlinear regime has been developed in this paper. The expressions for the spectral and angular distributions of the radiation have been derived. The model suggests that the origin of the radiation can be attributed to the violent sudden acceleration of plasma electrons experiencing the accelerating potential of the laser wakefield. The radiation process could help to provide a qualitative interpretation of existing experimental results, and offers useful information for future laser wakefield experiments.

  3. Electrostatic deposition of a micro solder particle using a single probe by applying a single rectangular pulse

    International Nuclear Information System (INIS)

    Nakabayashi, Daizo; Sawai, Kenji; Saito, Shigeki; Takahashi, Kunio

    2012-01-01

    Recently, micromanipulation techniques have been in high demand. A technique to deposit a metal microparticle onto a metal substrate by using a single metal probe has been proposed as one of the techniques. A solder particle with a diameter of 20–30 µm, initially adhering to the probe tip, is detached and deposited onto a substrate. The success rate of the particle deposition was 44% in the previous research, and is insufficient for industrial applications. In this paper, a technique of particle deposition by applying a single rectangular pulse is proposed, and the mechanism of the deposition is described. In the mechanism, an electric discharge between the probe and the particle when the particle reaches the substrate plays an important role in the particle deposition. Moreover, the mechanism of the proposed technique is verified by experiments of particle deposition, which are observed using a high-speed camera, a scanning electron microscope (SEM) and an oscilloscope. The success rate of the particle deposition has increased to 93% by the proposed technique. Furthermore, the damage to the particle by the electric discharge is evaluated using an RC circuit model, and the applicability of the proposed technique is discussed. (paper)

  4. Resonant multiphoton ionization of caesium atoms by ultra-short laser pulses at 1.06 μm

    International Nuclear Information System (INIS)

    Lompre, L.A.; Mainfray, G.; Manus, C.; Thebault, J.

    1978-01-01

    This paper reports the four-photon ionization of caesium atoms when the laser frequency is tuned through the resonant three-photon transition 6S → 6F. This experiment was performed by using a tunable-wavelength bandwidth-limited subnanosecond laser pulse at 1.06 μm, in the 10 8 -10 9 W.cm -2 laser intensity range. Pulse widths of 1.5 ns, 50 ps, and 15 ps were used. The resonant character of the multiphoton ionization process was observed, even with the shortest pulse of 15 ps. Nevertheless the influence of a temporal effect is demonstrated according to theoretical predictions. The resonance shift ΔE of the 6S → 6F transition energy was found to be linear with the laser intensity I within the range 10 8 -10 9 W.cm -2 . ΔE = αI, with α = 2 cm -1 /GW.cm -2 . This results confirms previous measurements performed with single-mode 35 ns laser pulses and is in very good agreement with calculated resonance shifts

  5. A z-gradient array for simultaneous multi-slice excitation with a single-band RF pulse.

    Science.gov (United States)

    Ertan, Koray; Taraghinia, Soheil; Sadeghi, Alireza; Atalar, Ergin

    2018-07-01

    Multi-slice radiofrequency (RF) pulses have higher specific absorption rates, more peak RF power, and longer pulse durations than single-slice RF pulses. Gradient field design techniques using a z-gradient array are investigated for exciting multiple slices with a single-band RF pulse. Two different field design methods are formulated to solve for the required current values of the gradient array elements for the given slice locations. The method requirements are specified, optimization problems are formulated for the minimum current norm and an analytical solution is provided. A 9-channel z-gradient coil array driven by independent, custom-designed gradient amplifiers is used to validate the theory. Performance measures such as normalized slice thickness error, gradient strength per unit norm current, power dissipation, and maximum amplitude of the magnetic field are provided for various slice locations and numbers of slices. Two and 3 slices are excited by a single-band RF pulse in simulations and phantom experiments. The possibility of multi-slice excitation with a single-band RF pulse using a z-gradient array is validated in simulations and phantom experiments. Magn Reson Med 80:400-412, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  6. Single-shot spectro-temporal characterization of XUV pulses from a seeded free-electron laser

    Science.gov (United States)

    de Ninno, Giovanni; Gauthier, David; Mahieu, Benoît; Ribič, Primož Rebernik; Allaria, Enrico; Cinquegrana, Paolo; Danailov, Miltcho Bojanov; Demidovich, Alexander; Ferrari, Eugenio; Giannessi, Luca; Penco, Giuseppe; Sigalotti, Paolo; Stupar, Matija

    2015-08-01

    Intense ultrashort X-ray pulses produced by modern free-electron lasers (FELs) allow one to probe biological systems, inorganic materials and molecular reaction dynamics with nanoscale spatial and femtoscale temporal resolution. These experiments require the knowledge, and possibly the control, of the spectro-temporal content of individual pulses. FELs relying on seeding have the potential to produce spatially and temporally fully coherent pulses. Here we propose and implement an interferometric method, which allows us to carry out the first complete single-shot spectro-temporal characterization of the pulses, generated by an FEL in the extreme ultraviolet spectral range. Moreover, we provide the first direct evidence of the temporal coherence of a seeded FEL working in the extreme ultraviolet spectral range and show the way to control the light generation process to produce Fourier-limited pulses. Experiments are carried out at the FERMI FEL in Trieste.

  7. Development of high damage threshold optics for petawatt-class short-pulse lasers

    International Nuclear Information System (INIS)

    Stuart, B.C.; Perry, M.D.; Boyd, R.D.

    1995-01-01

    The authors report laser-induced damage threshold measurements on pure and multilayer dielectrics and gold-coated optics at 1053 and 526 nm for pulse durations, τ, ranging from 140 fs to 1 ns. Damage thresholds of gold coatings are limited to 500 mJ/cm 2 in the subpicosecond range for 1053-nm pulses. In dielectrics, qualitative differences in the morphology of damage and a departure from the diffusion-dominated τ1/2 scaling indicate that damage results from plasma formation and ablation for τ≤10 ps and from conventional melting and boiling for τ>50 ps. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in quantitative agreement with both the pulsewidth and wavelength scaling of experimental results

  8. Ultra-intense, short pulse laser-plasma interactions with applications to the fast ignitor

    Energy Technology Data Exchange (ETDEWEB)

    Wilks, S.C.; Kruer, W.L.; Young, P.E.; Hammer, J.; Tabak, M.

    1995-04-01

    Due to the advent of chirped pulse amplification (CPA) as an efficient means of creating ultra-high intensity laser light (I > 5{times}10{sup 17} W/cm{sup 2}) in pulses less than a few picoseconds, new ideas for achieving ignition and gain in DT targets with less than 1 megajoule of input energy are currently being pursued. Two types of powerful lasers are employed in this scheme: (1) channeling beams and (2) ignition beams. The current state of laser-plasma interactions relating to this fusion scheme will be discussed. In particular, plasma physics issues in the ultra-intense regime are crucial to the success of this scheme. We compare simulation and experimental results in this highly nonlinear regime.

  9. Ultra-intense, short pulse laser-plasma interactions with applications to the fast ignitor

    International Nuclear Information System (INIS)

    Wilks, S.C.; Kruer, W.L.; Young, P.E.; Hammer, J.; Tabak, M.

    1995-04-01

    Due to the advent of chirped pulse amplification (CPA) as an efficient means of creating ultra-high intensity laser light (I > 5x10 17 W/cm 2 ) in pulses less than a few picoseconds, new ideas for achieving ignition and gain in DT targets with less than 1 megajoule of input energy are currently being pursued. Two types of powerful lasers are employed in this scheme: (1) channeling beams and (2) ignition beams. The current state of laser-plasma interactions relating to this fusion scheme will be discussed. In particular, plasma physics issues in the ultra-intense regime are crucial to the success of this scheme. We compare simulation and experimental results in this highly nonlinear regime

  10. 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.

  11. Tungsten diselenide for mode-locked erbium-doped fiber lasers with short pulse duration

    Science.gov (United States)

    Liu, Wenjun; Liu, Mengli; OuYang, Yuyi; Hou, Huanran; Ma, Guoli; Lei, Ming; Wei, Zhiyi

    2018-04-01

    In this paper, a WSe2 film prepared by chemical vapor deposition (CVD) is transferred onto a tapered fiber, and a WSe2 saturable absorber (SA) is fabricated. In order to measure the third-order optical nonlinearity of the WSe2, the Z-scan technique is applied. The modulation depth of the WSe2 SA is measured as being 21.89%. Taking advantage of the remarkable nonlinear absorption characteristic of the WSe2 SA, a mode-locked erbium-doped fiber laser is demonstrated at 1557.4 nm with a bandwidth of 25.8 nm and signal to noise ratio of 96 dB. To the best of our knowledge, the pulse duration of 163.5 fs is confirmed to be the shortest compared with previous mode-locked fiber lasers based on transition-metal dichalcogenides SAs. These results indicate that WSe2 is a powerful competitor in the application of ultrashort pulse lasers.

  12. Study and development of 22 kW peak power fiber coupled short pulse Nd:YAG laser for cleaning applications

    Science.gov (United States)

    Choubey, Ambar; Vishwakarma, S. C.; Vachhani, D. M.; Singh, Ravindra; Misra, Pushkar; Jain, R. K.; Arya, R.; Upadhyaya, B. N.; Oak, S. M.

    2014-11-01

    Free running short pulse Nd:YAG laser of microsecond pulse duration and high peak power has a unique capability to ablate material from the surface without heat propagation into the bulk. Applications of short pulse Nd:YAG lasers include cleaning and restoration of marble, stones, and a variety of metals for conservation. A study on the development of high peak power short pulses from Nd:YAG laser along with its cleaning and conservation applications has been performed. A pulse energy of 1.25 J with 55 μs pulse duration and a maximum peak power of 22 kW has been achieved. Laser beam has an M2 value of ~28 and a pulse-to-pulse stability of ±2.5%. A lower value of M2 means a better beam quality of the laser in multimode operation. A top hat spatial profile of the laser beam was achieved at the exit end of 200 μm core diameter optical fiber, which is desirable for uniform cleaning. This laser system has been evaluated for efficient cleaning of surface contaminations on marble, zircaloy, and inconel materials for conservation with cleaning efficiency as high as 98%. Laser's cleaning quality and efficiency have been analysed by using a microscope, a scanning electron microscope (SEM), and X-ray photon spectroscopy (XPS) measurements.

  13. Generation of ultra-intense and ultra-short laser pulses with high temporal contrast

    International Nuclear Information System (INIS)

    Julien, A.

    2006-03-01

    The topic of this thesis work concerns the design and the characterization of an efficient device devoted to the temporal contrast improvement for ultra-intense femtosecond laser pulses. The contrast is defined as the intensity ratio between the main femtosecond pulse and its nanosecond pedestal. This pedestal is the amplified spontaneous emission (ASE), inherent with laser amplification mechanism. The ASE background has dramatic effects for laser-matter interactions on a solid target. The presented work consists in the theoretical and experimental study of a temporal filter based on a third order nonlinear effect acting on the pulse polarization. We have studied several kinds of nonlinear filters. The selected device is based on the process of cross-polarized wave generation (XPW) in crystals with an anisotropic third-order nonlinear susceptibility. This nonlinear filter has been experimented on various femtosecond systems. It allows a contrast improvement of several orders of magnitude, as demonstrated by temporal profiles measurements on a large intensity dynamic. A device to improve the nonlinear process conversion efficiency, it means the filter transmission, has also been achieved. This method is based on constructive interferences between XPW signals generated in different crystals. This setup has made it possible to reach experimentally the maximum theoretical efficiency ( >20%) and in the same time ensures the system stability. At least, we have demonstrated that the filter preserves, or even improves, spectral and spatial qualities of the laser pulse. These results are thus particularly promising and allow contemplating the implementation of the filter in current femtosecond systems. (author)

  14. Guiding of short, intense laser pulses through solid guides and preformed plasma channels

    International Nuclear Information System (INIS)

    Borghesi, M.; Mackinnon, A.J.; Gaillard, R.; Malka, G.; Vickers, C.; Willi, O.; Blanchot, N.; Miquel, J.L.; Canaud, B.; Davies, J.R.; Malka, G.; Offenberger, A.A.

    2000-01-01

    In a series of experiments carried out at the Rutherford Appleton Laboratory, Chilton (UK) and at the Commissariat a l'Energie Atomique, Limeil (France), various techniques of guiding ultra-intense laser pulses over distances exceeding the natural diffraction length were investigated. Efficient guiding was demonstrated both through density channels formed in an underdense plasma by an intense prepulse and through solid guides (hollow capillary tubes). Indication of collimated fast electron propagation though solid targets has also been obtained. (authors)

  15. Removing roughness on metal surface by irradiation of intense short-pulsed ion beams

    International Nuclear Information System (INIS)

    Hashimoto, Y.

    1995-01-01

    Surface modification of metals with an intense pulsed ion beam (IPIB) was studied experimentally. When the temperature rise of metal surfaces by IPIB irradiation exceeds their boiling point, it is found that machining roughness on surfaces is removed. The experiments were performed with the pulsed power generator HARIMA-II at Himeji Institute of Technology. The main components of the ion beam were carbon and fluorine ions. The IPIB was irradiated to metal plates (Al, Cu and Ti) which were placed at the focal point. Machining roughness on Ti surface was removed after IPIB irradiation, while roughness on Al and Cu plates was not removed. Using the present experimental parameters (beam power density: 32 W/cm 2 , pulse width: 25 ns), the temperature rise of the Ti surface was estimated to be 8,100 K which exceed its boiling point (3,000 K). However, the estimated temperatures of Al and Cu surfaces was 2,500 and 1,500 K, respectively, that are less than their boiling points. These studies above suggests that temperature rise over the boiling point of metals is necessary for removing machining roughness on metal surfaces

  16. Femtosecond laser ablation of silver foil with single and double pulses

    CSIR Research Space (South Africa)

    Roberts, DE

    2009-01-01

    Full Text Available The average ablation depth per pulse of silver foil by 130 fs laser pulses has been measured in vacuum over a range of three orders of magnitude of pulse fluence up to 900 J cm-2. In addition, double pulses with separations up to 3.4 ns have been...

  17. Full 3D modelling of pulse propagation enables efficient nonlinear frequency conversion with low energy laser pulses in a single-element tripler

    Science.gov (United States)

    Kardaś, Tomasz M.; Nejbauer, Michał; Wnuk, Paweł; Resan, Bojan; Radzewicz, Czesław; Wasylczyk, Piotr

    2017-02-01

    Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is necessary for a robust wave mixing and the efficiency of broadband nonlinear conversion is limited by diffraction as well as spatial and temporal walk-off. Here we demonstrate a miniature third harmonic generator (tripler) with conversion efficiency exceeding 30%, producing 246 fs UV pulses via cascaded second order processes within a single laser beam focus. Designing this highly efficient and ultra compact frequency converter was made possible by full 3-dimentional modelling of propagation of tightly focused, broadband light fields in nonlinear and birefringent media.

  18. 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)

  19. 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.

  20. Short repetition time multiband echo-planar imaging with simultaneous pulse recording allows dynamic imaging of the cardiac pulsation signal.

    Science.gov (United States)

    Tong, Yunjie; Hocke, Lia M; Frederick, Blaise deB

    2014-11-01

    Recently developed simultaneous multislice echo-planar imaging (EPI) sequences permit imaging of the whole brain at short repetition time (TR), allowing the cardiac fluctuations to be fully sampled in blood-oxygen-level dependent functional MRI (BOLD fMRI). A novel low computational analytical method was developed to dynamically map the passage of the pulsation signal through the brain and visualize the whole cerebral vasculature affected by the pulse signal. This algorithm is based on a simple combination of fast BOLD fMRI and the scanner's own built-in pulse oximeter. Multiple, temporally shifted copies of the pulse oximeter data (with 0.08 s shifting step and coverage of a 1-s span) were downsampled and used as cardiac pulsation regressors in a general linear model based analyses (FSL) of the fMRI data. The resulting concatenated z-statistics maps show the voxels that are affected as the cardiac signal travels through the brain. Many voxels were highly correlated with the pulsation regressor or its temporally shifted version. The dynamic and static cardiac pulsation maps obtained from both the task and resting state scans, resembled cerebral vasculature. The results demonstrated: (i) cardiac pulsation significantly affects most voxels in the brain; (ii) combining fast fMRI and this analytical method can reveal additional clinical information to functional studies. Copyright © 2013 Wiley Periodicals, Inc.

  1. Water-selective excitation of short T2 species with binomial pulses.

    Science.gov (United States)

    Deligianni, Xeni; Bär, Peter; Scheffler, Klaus; Trattnig, Siegfried; Bieri, Oliver

    2014-09-01

    For imaging of fibrous musculoskeletal components, ultra-short echo time methods are often combined with fat suppression. Due to the increased chemical shift, spectral excitation of water might become a favorable option at ultra-high fields. Thus, this study aims to compare and explore short binomial excitation schemes for spectrally selective imaging of fibrous tissue components with short transverse relaxation time (T2 ). Water selective 1-1-binomial excitation is compared with nonselective imaging using a sub-millisecond spoiled gradient echo technique for in vivo imaging of fibrous tissue at 3T and 7T. Simulations indicate a maximum signal loss from binomial excitation of approximately 30% in the limit of very short T2 (0.1 ms), as compared to nonselective imaging; decreasing rapidly with increasing field strength and increasing T2 , e.g., to 19% at 3T and 10% at 7T for T2 of 1 ms. In agreement with simulations, a binomial phase close to 90° yielded minimum signal loss: approximately 6% at 3T and close to 0% at 7T for menisci, and for ligaments 9% and 13%, respectively. Overall, for imaging of short-lived T2 components, short 1-1 binomial excitation schemes prove to offer marginal signal loss especially at ultra-high fields with overall improved scanning efficiency. Copyright © 2013 Wiley Periodicals, Inc.

  2. Single- and dual-wavelength laser pulses induced modification in 10×(Al/Ti)/Si multilayer system

    Energy Technology Data Exchange (ETDEWEB)

    Salatić, B. [University of Belgrade, Institute of Physics Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Petrović, S., E-mail: spetro@vinca.rs [University of Belgrade, Institute of Nuclear Science-Vinča, POB 522, 11001 Belgrade (Serbia); Peruško, D. [University of Belgrade, Institute of Nuclear Science-Vinča, POB 522, 11001 Belgrade (Serbia); Čekada, M.; Panjan, P. [Jožef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Pantelić, D.; Jelenković, B. [University of Belgrade, Institute of Physics Belgrade, Pregrevica 118, 11080 Belgrade (Serbia)

    2016-01-01

    Graphical abstract: - Highlights: • Experimental and numerical study of laser-induced ablation and micro-sized crater formation. • Dual-wavelength pulses induce creation of wider and deeper craters due to synergies of two processes. • Sunflower-like structure formed by dual-wavelength pulses at low irradiance. • Numerical model of nanosecond pulsed laser ablation for complex (Al/Ti)/Si system has been developed. - Abstract: The surface morphology of the ablation craters created in the multilayer 10×(Al/Ti)/Si system by nanosecond laser pulses at single- and dual wavelength has been studied experimentally and numerically. A complex multilayer thin film including ten (Al/Ti) bilayers deposited by ion sputtering on Si(1 0 0) substrate to a total thickness of 260 nm were illuminated at different laser irradiance in the range 0.25–3.5 × 10{sup 9} W cm{sup −2}. Single pulse laser irradiation was done at normal incidence in air, with the single wavelength, either at 532 nm or 1064 nm or with both laser light simultaneously in the ratio of 1:10 for energy per pulse between second harmonic and 1064 nm. Most of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the sample surface. The results show an increase in surface roughness, formation of specific nanostructures, appearance of hydrodynamic features and ablation of surface material with crater formation. Applying a small fraction (10%) of the second harmonic in dual-wavelength pulses, a modification of the 10×(Al/Ti)/Si system by a single laser pulse was reflected in the formation of wider and/or deeper craters. Numerical calculations show that the main physical mechanism in ablation process is normal evaporation without phase explosion. The calculated and experimental results agree relatively well for the whole irradiance range, what makes the model applicable to complex Al/Ti multilayer systems.

  3. Diode-pumped, single frequency Nd:YLF laser for 60-beam OMEGA laser pulse-shaping system

    International Nuclear Information System (INIS)

    Okishev, A.V.; Seka, W.

    1997-01-01

    The operational conditions of the OMEGA pulse-shaping system require an extremely reliable and low-maintenance master oscillator. The authors have developed a diode-pumped, single-frequency, pulsed Nd:YLF laser for this application. The laser generates Q-switched pulses of ∼160-ns duration and ∼10-microJ energy content at the 1,053-nm wavelength with low amplitude fluctuations (<0.6% rms) and low temporal jitter (<7 ns rms). Amplitude and frequency feedback stabilization systems have been used for high long-term amplitude and frequency stability

  4. Laser short-pulse heating of an aluminum thin film: Energy transfer in electron and lattice sub-systems

    Energy Technology Data Exchange (ETDEWEB)

    Bin Mansoor, Saad; Sami Yilbas, Bekir, E-mail: bsyilbas@kfupm.edu.sa

    2015-08-15

    Laser short-pulse heating of an aluminum thin film is considered and energy transfer in the film is formulated using the Boltzmann equation. Since the heating duration is short and the film thickness is considerably small, thermal separation of electron and lattice sub-systems is incorporated in the analysis. The electron–phonon coupling is used to formulate thermal communication of both sub-systems during the heating period. Equivalent equilibrium temperature is introduced to account for the average energy of all phonons around a local point when they redistribute adiabatically to an equilibrium state. Temperature predictions of the Boltzmann equation are compared with those obtained from the two-equation model. It is found that temperature predictions from the Boltzmann equation differ slightly from the two-equation model results. Temporal variation of equivalent equilibrium temperature does not follow the laser pulse intensity in the electron sub-system. The time occurrence of the peak equivalent equilibrium temperature differs for electron and lattice sub-systems, which is attributed to phonon scattering in the irradiated field in the lattice sub-system. In this case, time shift is observed for occurrence of the peak temperature in the lattice sub-system.

  5. Laser short-pulse heating of an aluminum thin film: Energy transfer in electron and lattice sub-systems

    International Nuclear Information System (INIS)

    Bin Mansoor, Saad; Sami Yilbas, Bekir

    2015-01-01

    Laser short-pulse heating of an aluminum thin film is considered and energy transfer in the film is formulated using the Boltzmann equation. Since the heating duration is short and the film thickness is considerably small, thermal separation of electron and lattice sub-systems is incorporated in the analysis. The electron–phonon coupling is used to formulate thermal communication of both sub-systems during the heating period. Equivalent equilibrium temperature is introduced to account for the average energy of all phonons around a local point when they redistribute adiabatically to an equilibrium state. Temperature predictions of the Boltzmann equation are compared with those obtained from the two-equation model. It is found that temperature predictions from the Boltzmann equation differ slightly from the two-equation model results. Temporal variation of equivalent equilibrium temperature does not follow the laser pulse intensity in the electron sub-system. The time occurrence of the peak equivalent equilibrium temperature differs for electron and lattice sub-systems, which is attributed to phonon scattering in the irradiated field in the lattice sub-system. In this case, time shift is observed for occurrence of the peak temperature in the lattice sub-system

  6. Study of surface layer assessment of solids by ultra-slow and short-pulsed positron beams

    International Nuclear Information System (INIS)

    Suzuki, Ryouichi; Ohdaira, Toshiyuki; Mikado, Tomohisa; Yamada, Kawakatsu

    2004-01-01

    Thin films of insulators with low dielectric constant, as a candidate for next generation LSI (large scale integration), were assessed by two dimensional positron life time and wave height measurements using variable incident energy and also short pulsed positron beams. Linkages and openness of nano-scale voids in the films were evaluated by the measurements. Amorphous SiO 2 films were compared with SiCOH films synthesized by plasma CVD (Chemical Vapor Deposition) by measurements of the correlation between positron lifetime and momentum using short-pulsed positron beams. From the measurements, many hydrocarbons were found on void surface of SiCOH films. Positron lifetime measurement gives information about void sizes, and Doppler broadening due to annihilation γ-rays offers electron momentum distribution, which is a counterpart of positron annihilation. Two γ-rays are emitted on the positron annihilation. Coincident measurements of these two γ-rays provide the correlation spectra between positron lifetime and momentum. An instrument for positron annihilation excitation Auger electron spectroscopy (PAES) was improved, and a time-of-flight (TOF) PAES instrument was developed. Double counting rate and high resolution, compared with a conventional Auger electron spectrometer, were attained in elementary analysis using above TOF-PAES instrument. (Y. Kazumata)

  7. 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.

  8. Effects of ageing on single muscle fibre contractile function following short-term immobilisation

    DEFF Research Database (Denmark)

    Hvid, Lars G; Ørtenblad, Niels; Aagaard, Per

    2011-01-01

    Very little attention has been given to the combined effect of healthy ageing and short-term disuse on the contractile function of human single muscle fibres. Therefore, the present study investigated the effects of 2 weeks of lower limb cast immobilisation (i.e. disuse) on selected contractile...

  9. Modified Dual Three-Pulse Modulation technique for single-phase inverter topology

    Science.gov (United States)

    Sree Harsha, N. R.; Anitha, G. S.; Sreedevi, A.

    2016-01-01

    In a recent paper, a new modulation technique called Dual Three Pulse Modulation (DTPM) was proposed to improve the efficiency of the power converters of the Electric/Hybrid/Fuel-cell vehicles. It was simulated in PSIM 9.0.4 and uses analog multiplexers to generate the modulating signals for the DC/DC converter and inverter. The circuit used is complex and many other simulation softwares do not support the analog multiplexers as well. Also, the DTPM technique produces modulating signals for the converter, which are essentially needed to produce the modulating signals for the inverter. Hence, it cannot be used efficiently to switch the valves of a stand-alone inverter. We propose a new method to generate the modulating signals to switch MOSFETs of a single phase Dual-Three pulse Modulation based stand-alone inverter. The circuits proposed are simulated in Multisim 12.0. We also show an alternate way to switch a DC/DC converter in a way depicted by DTPM technique both in simulation (MATLAB/Simulink) and hardware. The circuitry is relatively simple and can be used for the further investigations of DTPM technique.

  10. ZnO thin films on single carbon fibres fabricated by Pulsed Laser Deposition (PLD)

    Energy Technology Data Exchange (ETDEWEB)

    Krämer, André; Engel, Sebastian [Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena (Germany); Sangiorgi, Nicola [Institute of Science and Technology for Ceramics – National Research Council of Italy (CNR-ISTEC), via Granarolo 64, 48018 Faenza, RA (Italy); Department of Chemical Science and Technologies, University of Rome Tor Vergata, via della Ricerca Scientifica, 00133 Rome (Italy); Sanson, Alessandra [Institute of Science and Technology for Ceramics – National Research Council of Italy (CNR-ISTEC), via Granarolo 64, 48018 Faenza, RA (Italy); Bartolomé, Jose F. [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC), C/Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain); Gräf, Stephan, E-mail: stephan.graef@uni-jena.de [Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena (Germany); Müller, Frank A. [Otto Schott Institute of Materials Research (OSIM), Friedrich Schiller University Jena, Löbdergraben 32, 07743 Jena (Germany); Center for Energy and Environmental Chemistry Jena (CEEC Jena), Friedrich Schiller University Jena, Philosophenweg 7a, 07743 Jena (Germany)

    2017-03-31

    Highlights: • Carbon fibres were entirely coated with thin films consisting of aligned ZnO crystals. • A Q-switched CO2 laser was utilised as radiation source. • Suitability of ZnO thin films on carbon fibres as photo anodes for DSSC was studied. - Abstract: Single carbon fibres were 360° coated with zinc oxide (ZnO) thin films by pulsed laser deposition using a Q-switched CO{sub 2} laser with a pulse duration τ ≈ 300 ns, a wavelength λ = 10.59 μm, a repetition frequency f{sub rep} = 800 Hz and a peak power P{sub peak} = 15 kW in combination with a 3-step-deposition technique. In a first set of experiments, the deposition process was optimised by investigating the crystallinity of ZnO films on silicon and polished stainless steel substrates. Here, the influence of the substrate temperature and of the oxygen partial pressure of the background gas were characterised by scanning electron microscopy and X-ray diffraction analyses. ZnO coated carbon fibres and conductive glass sheets were used to prepare photo anodes for dye-sensitised solar cells in order to investigate their suitability for energy conversion devices. To obtain a deeper insight of the electronic behaviour at the interface between ZnO and substrate I–V measurements were performed.

  11. Interaction of single-pulse laser energy with bow shock in hypersonic flow

    Directory of Open Access Journals (Sweden)

    Hong Yanji

    2014-04-01

    Full Text Available Pressure sensing and schlieren imaging with high resolution and sensitivity are applied to the study of the interaction of single-pulse laser energy with bow shock at Mach 5. An Nd:YAG laser operated at 1.06 μm, 100 mJ pulse energy is used to break down the hypersonic flow in a shock tunnel. Three-dimensional Navier–Stokes equations are solved with an upwind scheme to simulate the interaction. The pressure at the stagnation point on the blunt body is measured and calculated to examine the pressure variation during the interaction. Schlieren imaging is used in conjunction with the calculated density gradients to examine the process of the interaction. The results show that the experimental pressure at the stagnation point on the blunt body and schlieren imaging fit well with the simulation. The pressure at the stagnation point on the blunt body will increase when the transmission shock approaches the blunt body and decrease with the formation of the rarefied wave. Bow shock is deformed during the interaction. Quasi-stationary waves are formed by high rate laser energy deposition to control the bow shock. The pressure and temperature at the stagnation point on the blunt body and the wave drag are reduced to 50%, 75% and 81% respectively according to the simulation. Schlieren imaging has provided important information for the investigation of the mechanism of the interaction.

  12. Analysis of short and long crack behavior and single overload effect by crack opening stress

    International Nuclear Information System (INIS)

    Song, Sam Hong; Lee, Kyeong Ro

    1999-01-01

    The study analyzed the behaviors of short and long crack as well as the effect of single tensile overload on the crack behaviors by using fatigue crack opening behavior. Crack opening stress is measured by an elastic compliance method which may precisely and continuously provide many data using strain gages during experiment. The unusual growth behaviors of short crack and crack after the single tensile overload applied, was explained by the variations of crack opening stress. In addition, fatigue crack growth rate was expressed as a linear form for short crack as for long crack by using effective stress intensity factor range as fracture mechanical parameter, which is based on crack closure concept. And investigation is performed with respect to the relation between plastic zone size formed at the crack tip and crack retardation, crack length and the number of cycles promoted or retarded, and the overload effect on the fatigue life

  13. Secondary plasma formation after single pulse laser ablation underwater and its advantages for laser induced breakdown spectroscopy (LIBS).

    Science.gov (United States)

    Gavrilović, M R; Cvejić, M; Lazic, V; Jovićević, S

    2016-06-07

    In this work we present studies of spatial and temporal plasma evolution after single pulse ablation of an aluminium target in water. The laser ablation was performed using 20 ns long pulses emitted at 1064 nm. The plasma characterization was performed by fast photography, the Schlieren technique, shadowgraphy and optical emission spectroscopy. The experimental results indicate the existence of two distinct plasma stages: the first stage has a duration of approximately 500 ns from the laser pulse, and is followed by a new plasma growth starting from the crater center. The secondary plasma slowly evolves inside the growing vapor bubble, and its optical emission lasts over several tens of microseconds. Later, the hot glowing particles, trapped inside the vapor cavity, were detected during the whole cycle of the bubble, where the first collapse occurs after 475 μs from the laser pulse. Differences in the plasma properties during the two evolution phases are discussed, with an accent on the optical emission since its detection is of primary importance for LIBS. Here we demonstrate that the LIBS signal quality in single pulse excitation underwater can be greatly enhanced by detecting only the secondary plasma emission, and also by applying long acquisition gates (in the order of 10-100 μs). The presented results are of great importance for LIBS measurements inside a liquid environment, since they prove that a good analytical signal can be obtained by using nanosecond pulses from a single commercial laser source and by employing cost effective, not gated detectors.

  14. Single shot diffraction of picosecond 8.7-keV x-ray pulses

    Directory of Open Access Journals (Sweden)

    F. H. O’Shea

    2012-02-01

    Full Text Available We demonstrate multiphoton, single shot diffraction images of x rays produced by inverse Compton scattering a high-power CO_{2} laser from a relativistic electron beam, creating a pulse of 8.7 keV x rays. The tightly focused, relatively high peak brightness electron beam and high photon density from the 2 J CO_{2} laser yielded 6×10^{7} x-ray photons over the full opening angle in a single shot. Single shot x-ray diffraction is performed by passing the x rays though a vertical slit and on to a flat silicon (111 crystal. 10^{2} diffracted photons were detected. The spectrum of the detected x rays is compared to simulation. The diffraction and detection of 10^{2} x rays is a key step to a more efficient time resolved diagnostic in which the number of observed x rays might reach 10^{4}; enabling a unique, flexible x-ray source as a sub-ps resolution diagnostic for studying the evolution of chemical reactions, lattice deformation and melting, and magnetism.

  15. Transverse emittance measurement of high-current single pulse beams using pepper-pot method

    International Nuclear Information System (INIS)

    Ke Jianlin; Zhou Changgeng; Qiu Rui

    2013-01-01

    A pepper pot-imaging plate system has been developed and used to measure the 4-D transverse emittance of a vacuum arc ion source. Single beam pulses of tens to hundreds milliamperes were extracted from the plasma with 64 kV high voltage. An imaging plate was laid after the pepper pot to visualize the ion beamlets passing though the holes on the pepper pot. An application program was developed to show the phase-space distribution and calculate the ellipse and RMS emittances. The normalized RMS emittances are about 6.41 π·mm·mrad in x-direction and 4.61 π·mm·mrad in y-direction. It is shown that the emittance of the vacuum arc ion source is much larger than that of other types of ion sources, which is mainly attributed to the high current and the convex meniscus of this source. (authors)

  16. Development of dynamic simulation code for fuel cycle of fusion reactor. 1. Single pulse operation simulation

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, Isao; Seki, Yasushi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment; Sasaki, Makoto; Shintani, Kiyonori; Kim, Yeong-Chan

    1997-11-01

    A dynamic simulation code for the fuel cycle of a fusion experimental reactor has been developed. The code follows the fuel inventory change with time in the plasma chamber and the fuel cycle system during a single pulse operation. The time dependence of the fuel inventory distribution is evaluated considering the fuel burn and exhaust in the plasma chamber, purification and supply functions. For each subsystem of the plasma chamber and the fuel cycle system, the fuel inventory equation is written based on the equation of state considering the function of fuel burn, exhaust, purification, and supply. The processing constants of subsystem for the steady states were taken from the values in the ITER Conceptual Design Activity (CDA) report. Using the code, the time dependence of the fuel supply and inventory depending on the burn state and subsystem processing functions are shown. (author)

  17. Single-Cycle Terahertz Pulse Generation from OH1 Crystal via Cherenkov Phase Matching

    Science.gov (United States)

    Uchida, Hirohisa; Oota, Kengo; Okimura, Koutarou; Kawase, Kodo; Takeya, Kei

    2018-06-01

    OH1 crystal is an organic nonlinear optical crystal with a large nonlinear optical constant. However, it has dispersion of refractive indices in the terahertz (THz) frequency. This limits the frequencies that satisfy the phase matching conditions for THz wave generation. In this study, we addressed the phase matching conditions for THz wave generation by combining an OH1 crystal with prism-coupled Cherenkov phase matching. We observed the generation of single-cycle THz pulses with a spectrum covering a frequency range of 3 THz. These results prove that combining prism-coupled Cherenkov phase matching with nonlinear optical crystals yields a THz wave generation method that is insusceptible to crystal dispersion.

  18. High efficiency 40 K single-stage Stirling-type pulse tube cryocooler

    Science.gov (United States)

    Wu, X. L.; Chen, L. B.; Pan, C. Z.; Cui, C.; Wang, J. J.; Zhou, Y.

    2017-12-01

    A high efficiency single-stage Stirling-type coaxial pulse tube cryocooler (SPTC) operating at around 40 K has been designed, built and tested. The double-inlet and the inertance tubes together with the gas reservoir were adopted as the phase shifters. Under the conditions of 2.5 MPa charging pressure and 30 Hz operating frequency, the prototype has achieved a no-load temperature of 23.8 K with 330 W of electric input power at a rejection temperature of 279 K. When the input power increases to 400 W, it can achieve a cooling capacity of 4.7 W/40 K while rejecting heat at 279 K yielding an efficiency of 7.02% relative to Carnot. It achieves a cooling capacity of 5 W/40 K with an input power of 450 W. It takes 10 minutes for the SPTC to cool to its no-load temperature of 40 K from 295 K.

  19. Laser-fired contact formation on metallized and passivated silicon wafers under short pulse durations

    Science.gov (United States)

    Raghavan, Ashwin S.

    The objective of this work is to develop a comprehensive understanding of the physical processes governing laser-fired contact (LFC) formation under microsecond pulse durations. Primary emphasis is placed on understanding how processing parameters influence contact morphology, passivation layer quality, alloying of Al and Si, and contact resistance. In addition, the research seeks to develop a quantitative method to accurately predict the contact geometry, thermal cycles, heat and mass transfer phenomena, and the influence of contact pitch distance on substrate temperatures in order to improve the physical understanding of the underlying processes. Finally, the work seeks to predict how geometry for LFCs produced with microsecond pulses will influence fabrication and performance factors, such as the rear side contacting scheme, rear surface series resistance and effective rear surface recombination rates. The characterization of LFC cross-sections reveals that the use of microsecond pulse durations results in the formation of three-dimensional hemispherical or half-ellipsoidal contact geometries. The LFC is heavily alloyed with Al and Si and is composed of a two-phase Al-Si microstructure that grows from the Si wafer during resolidification. As a result of forming a large three-dimensional contact geometry, the total contact resistance is governed by the interfacial contact area between the LFC and the wafer rather than the planar contact area at the original Al-Si interface within an opening in the passivation layer. By forming three-dimensional LFCs, the total contact resistance is significantly reduced in comparison to that predicted for planar contacts. In addition, despite the high energy densities associated with microsecond pulse durations, the passivation layer is well preserved outside of the immediate contact region. Therefore, the use of microsecond pulse durations can be used to improve device performance by leading to lower total contact resistances

  20. Kinematic MRI using short TR single shot fast spin echo (SSFSE) in evaluating swallowing

    Energy Technology Data Exchange (ETDEWEB)

    Isogai, Satoshi; Takehara, Yasuo; Isoda, Haruo; Kodaira, Nami; Masunaga, Hatsuko; Ozawa, Fukujirou; Kaneko, Masao [Hamamatsu Univ. School of Medicine, Shizuoka (Japan); Nozaki, Atsushi; Kabasawa, Hiroyuki

    1999-03-01

    The utility of short TR single shot fast spin echo (SSFSE) MR imaging for evaluating swallowing was determined. Five healthy volunteers underwent kinematic MR imaging of swallowing with a 1.5 T MR scanner using the short TR (300 ms) SSFSE sequence. Twenty phases of sagittal sections were acquired within 6 sec, where the temporal resolution was 300 ms. For oral contrast medium, we used prune yogurt juice with Fe added. The image contrast of short TR SSFSE was found to be somewhere like that of T1-weighted images. In all cases, both the buccal and pharyngeal stages of swallowing were successfully depicted. The Fe-added prune yogurt juice performed as a positive contrast medium and helped determine anatomical structures in the buccal stage. Short TR (300 ms) SSFSE was useful in evaluating swallowing. The combined use of Fe-added prune yogurt juice was helpful in enhancing the surface of the oropharynx. (author)

  1. Kinematic MRI using short TR single shot fast spin echo (SSFSE) in evaluating swallowing

    International Nuclear Information System (INIS)

    Isogai, Satoshi; Takehara, Yasuo; Isoda, Haruo; Kodaira, Nami; Masunaga, Hatsuko; Ozawa, Fukujirou; Kaneko, Masao; Nozaki, Atsushi; Kabasawa, Hiroyuki

    1999-01-01

    The utility of short TR single shot fast spin echo (SSFSE) MR imaging for evaluating swallowing was determined. Five healthy volunteers underwent kinematic MR imaging of swallowing with a 1.5 T MR scanner using the short TR (300 ms) SSFSE sequence. Twenty phases of sagittal sections were acquired within 6 sec, where the temporal resolution was 300 ms. For oral contrast medium, we used prune yogurt juice with Fe added. The image contrast of short TR SSFSE was found to be somewhere like that of T1-weighted images. In all cases, both the buccal and pharyngeal stages of swallowing were successfully depicted. The Fe-added prune yogurt juice performed as a positive contrast medium and helped determine anatomical structures in the buccal stage. Short TR (300 ms) SSFSE was useful in evaluating swallowing. The combined use of Fe-added prune yogurt juice was helpful in enhancing the surface of the oropharynx. (author)

  2. Supersonic Ionization Wave Driven by Radiation Transport in a Short-Pulse Laser-Produced Plasma

    International Nuclear Information System (INIS)

    Ditmire, T.; Gumbrell, E.T.; Smith, R.A.; Mountford, L.; Hutchinson, M.H.

    1996-01-01

    Through the use of an ultrashort (2ps) optical probe, we have time resolved the propagation of an ionization wave into solid fused silica. This ionization wave results when a plasma is created by the intense irradiation of a solid target with a 2ps laser pulse. We find that the velocity of the ionization wave is consistent with radiation driven thermal transport, exceeding the velocity expected from simple electron thermal conduction by nearly an order of magnitude. copyright 1996 The American Physical Society

  3. 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.

  4. Impacts of ambient and ablation plasmas on short- and ultrashort-pulse laser processing of surfaces

    Czech Academy of Sciences Publication Activity Database

    Bulgakova, Nadezhda M.; Panchenko, A.N.; Zhukov, V.P.; Kudryashov, S.I.; Pereira, A.; Marine, W.; Mocek, Tomáš; Bulgakov, A.V.

    2014-01-01

    Roč. 5, č. 4 (2014), s. 1344-1372 ISSN 2072-666X R&D Projects: GA MŠk ED2.1.00/01.0027; GA MŠk EE2.3.20.0143 Grant - others:HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 6(XE) CZ.1.07/2.3.00/20.0143 Institutional support: RVO:68378271 Keywords : pulsed laser ablation * laser material processing * laser plasma * ambient gas breakdown * material redeposition * plasma pipe formation * microstructures Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.269, year: 2014

  5. Extremely short optical pulse in a system of nanotubes with adsorbed hydrogen

    International Nuclear Information System (INIS)

    Belonenko, Mikhail B.; Popov, Alexander S.; Lebedev, Nikolay G.; Pak, Anastasia V.; Zhukov, Alexander V.

    2011-01-01

    In this Letter we address the system of carbon nanotubes with adsorbed hydrogen, which is a problem of particular practical importance. Based on the periodic Anderson model we describe the electronic subsystem in such a system, so that employing the method of Green functions allowed us to obtain the dispersion law for electrons. In the low-temperature limit we investigated a joint dynamics of electrons and electromagnetic field. The effective equation, which describes the propagation of ultrashort optical pulses, has been derived. We analyze the solutions of this equation and their dependence on the parameters of the problem for a two-dimensional CNT system.

  6. Ultra-fast Movies Resolve Ultra-short Pulse Laser Ablation and Bump Formation on Thin Molybdenum Films

    Science.gov (United States)

    Domke, Matthias; Rapp, Stephan; Huber, Heinz

    For the monolithic serial interconnection of CIS thin film solar cells, 470 nm molybdenum films on glass substrates must be separated galvanically. The single pulse ablation with a 660 fs laser at a wavelength of 1053 nm is investigated in a fluence regime from 0.5 to 5.0 J/cm2. At fluences above 2.0 J/cm2 bump and jet formation can be observed that could be used for creating microstructures. For the investigation of the underlying mechanisms of the laser ablation process itself as well as of the bump or jet formation, pump probe microscopy is utilized to resolve the transient ablation behavior.

  7. 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.

  8. Simulation and measurement of short infrared pulses on silicon position sensitive device

    International Nuclear Information System (INIS)

    Krapohl, D; Esebamen, O X; Nilsson, H E; Thungstroem, G

    2011-01-01

    Lateral position sensitive devices (PSD) are important for triangulation, alignment and surface measurements as well as for angle measurements. Large PSDs show a delay on rising and falling edges when irradiated with near infra-red light. This delay is also dependent on the spot position relative to the electrodes. It is however desirable in most applications to have a fast response. We investigated the responsiveness of a Sitek PSD in a mixed mode simulation of a two dimensional full sized detector. For simulation and measurement purposes focused light pulses with a wavelength of 850 nm, duration of 1μs and spot size of 280μm were used. The cause for the slopes of rise and fall time is due to time constants of the device capacitance as well as the photo-generation mechanism itself. To support the simulated results, we conducted measurements of rise and fall times on a physical device. Additionally, we quantified the homogeneity of the device by repositioning a spot of light from a pulsed ir-laser diode on the surface area.

  9. Effects of single pulse energy on the properties of ceramic coating prepared by micro-arc oxidation on Ti alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun-Hua [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Faculty of Mechanical and Electrical Engineering, Kunming University of Science and Technology, Kunming 650500 (China); Wang, Jin [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Beijing Key Lab of Precision/Ultra-precision Manufacturing Equipments and Control, Beijing 100084 (China); Lu, Yan [School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Du, Mao-Hua [Faculty of Mechanical and Electrical Engineering, Kunming University of Science and Technology, Kunming 650500 (China); Han, Fu-Zhu, E-mail: hanfuzhu@mail.tsinghua.edu.cn [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Beijing Key Lab of Precision/Ultra-precision Manufacturing Equipments and Control, Beijing 100084 (China)

    2015-01-01

    Highlights: • Single pulse energy remarkably influences the properties of ceramic coating prepared by MAO on Ti alloy. • The accumulative time of impulse width is an important parameter in the scientific and rational measurement of the film forming law of ceramic coating. • The ceramic coating thickness approximately linearly increases with the cumulative time of impulse width. • Larger impulse width resulted in higher single pulse energy, film forming rates and thicker ceramic coating thickness. • The effects of single pulse energy on the micro-hardness and phase composition of ceramic coating are not as evident as those of frequency and duty cycle. - Abstract: The effects of single pulse energy on the properties of ceramic coating fabricated on a Ti–6Al–4V alloy via micro-arc oxidation (MAO) in aqueous solutions containing aluminate, phosphate, and some additives are investigated. The thickness, micro-hardness, surface and cross-sectional morphology, surface roughness, and compositions of the ceramic coating are studied using eddy current thickness meter, micro-hardness tester, JB-4C Precision Surface roughness meter, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Single pulse energy remarkably influences the ceramic coating properties. The accumulative time of impulse width is an important parameter in the scientific and rational measurement of the film forming law of ceramic coating. The ceramic coating thickness approximately linearly increases with the cumulative time of impulse width. Larger impulse width resulted in higher single pulse energy, film forming rates and thicker ceramic coating thickness. The sizes of oxide particles, micro-pores and micro-cracks slightly increase with impulse width and single pulse energy. The main surface conversion products generated during MAO process in aqueous solutions containing aluminate are rutile TiO{sub 2}, anatase TiO{sub 2}, and a large amount of Al{sub 2}TiO{sub 5}. The effects of

  10. Light field driven streak-camera for single-shot measurements of the temporal profile of XUV-pulses from a free-electron laser; Lichtfeld getriebene Streak-Kamera zur Einzelschuss Zeitstrukturmessung der XUV-Pulse eines Freie-Elektronen Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Fruehling, Ulrike

    2009-10-15

    The Free Electron Laser in Hamburg (FLASH) is a source for highly intense ultra short extreme ultraviolet (XUV) light pulses with pulse durations of a few femtoseconds. Due to the stochastic nature of the light generation scheme based on self amplified spontaneous emission (SASE), the duration and temporal profile of the XUV pulses fluctuate from shot to shot. In this thesis, a THz-field driven streak-camera capable of single pulse measurements of the XUV pulse-profile has been realized. In a first XUV-THz pump-probe experiment at FLASH, the XUV-pulses are overlapped in a gas target with synchronized THz-pulses generated by a new THz-undulator. The electromagnetic field of the THz light accelerates photoelectrons produced by the XUV-pulses with the resulting change of the photoelectron momenta depending on the phase of the THz field at the time of ionisation. This technique is intensively used in attosecond metrology where near infrared streaking fields are employed for the temporal characterisation of attosecond XUV-Pulses. Here, it is adapted for the analysis of pulse durations in the few femtosecond range by choosing a hundred times longer far infrared streaking wavelengths. Thus, the gap between conventional streak cameras with typical resolutions of hundreds of femtoseconds and techniques with attosecond resolution is filled. Using the THz-streak camera, the time dependent electric field of the THz-pulses was sampled in great detail while on the other hand the duration and even details of the time structure of the XUV-pulses were characterized. (orig.)

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

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  12. A 10 TW pulsed energy complex PIRIT-2000 for investigation of short-wave radiation

    Energy Technology Data Exchange (ETDEWEB)

    Popkov, N F; Ryaslov, E A; Kargin, V I; Pikar` , A S; Vorontsov, V I; Kotel` nikov, D V; Melkozerov, A V [All-Russian Scientific Research Inst. of Experimental Physics, Sarov (Russian Federation)

    1997-12-31

    The results of investigation of a pulsed plasma x-ray source at the PIRIT-2000 fast operating capacitor bank are reported. The maximum energy stored in a primary 54-module capacitive storage at the output voltage of 500 kV reaches 2 MJ. The capacitor bank energizes a vacuum inductive storage, which is commutated by a plasma opening switch. The plasma diode consists of a tube cathode of diameter 15 cm and of a larger tube anode with six plasma injecting guns. The current amplitude and the current rise time at the plasma load amounts to 4 MA and 150 ns, respectively. The x-ray doses were measured by means of thermoluminescent dosemeters and the integral radiation output by means of a thermocouple calorimeter. The radiation output as high as 100 kJ was achieved at the stored energy of 1 MJ. (J.U.). 4 figs., 4 refs.

  13. Oxygen-assisted multipass cutting of carbon fiber reinforced plastics with ultra-short laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Kononenko, T. V.; Komlenok, M. S.; Konov, V. I. [Natural Sciences Center, General Physics Institute, Vavilov str. 38, 119991 Moscow (Russian Federation); National Research Nuclear University, “MEPhI,” Kashirskoye shosse 31, 115409 Moscow (Russian Federation); Freitag, C. [Universität Stuttgart, Institut für Strahlwerkzeuge (IFSW), Pfaffenwaldring 43, 70569 Stuttgart (Germany); GSaME Graduate School of Excellence Advanced Manufacturing Engineering, Nobelstrasse 12, 70569 Stuttgart (Germany); Onuseit, V.; Weber, R.; Graf, T. [Universität Stuttgart, Institut für Strahlwerkzeuge (IFSW), Pfaffenwaldring 43, 70569 Stuttgart (Germany)

    2014-03-14

    Deep multipass cutting of bidirectional and unidirectional carbon fiber reinforced plastics (CFRP) with picosecond laser pulses was investigated in different static atmospheres as well as with the assistance of an oxygen or nitrogen gas flow. The ablation rate was determined as a function of the kerf depth and the resulting heat affected zone was measured. An assisting oxygen gas flow is found to significantly increase the cutting productivity, but only in deep kerfs where the diminished evaporative ablation due to the reduced laser fluence reaching the bottom of the kerf does not dominate the contribution of reactive etching anymore. Oxygen-supported cutting was shown to also solve the problem that occurs when cutting the CFRP parallel to the fiber orientation where a strong deformation and widening of the kerf, which temporarily slows down the process speed, is revealed to be typical for processing in standard air atmospheres.

  14. Oxygen-assisted multipass cutting of carbon fiber reinforced plastics with ultra-short laser pulses

    International Nuclear Information System (INIS)

    Kononenko, T. V.; Komlenok, M. S.; Konov, V. I.; Freitag, C.; Onuseit, V.; Weber, R.; Graf, T.

    2014-01-01

    Deep multipass cutting of bidirectional and unidirectional carbon fiber reinforced plastics (CFRP) with picosecond laser pulses was investigated in different static atmospheres as well as with the assistance of an oxygen or nitrogen gas flow. The ablation rate was determined as a function of the kerf depth and the resulting heat affected zone was measured. An assisting oxygen gas flow is found to significantly increase the cutting productivity, but only in deep kerfs where the diminished evaporative ablation due to the reduced laser fluence reaching the bottom of the kerf does not dominate the contribution of reactive etching anymore. Oxygen-supported cutting was shown to also solve the problem that occurs when cutting the CFRP parallel to the fiber orientation where a strong deformation and widening of the kerf, which temporarily slows down the process speed, is revealed to be typical for processing in standard air atmospheres

  15. Analysis and mitigation of systematic errors in spectral shearing interferometry of pulses approaching the single-cycle limit [Invited

    International Nuclear Information System (INIS)

    Birge, Jonathan R.; Kaertner, Franz X.

    2008-01-01

    We derive an analytical approximation for the measured pulse width error in spectral shearing methods, such as spectral phase interferometry for direct electric-field reconstruction (SPIDER), caused by an anomalous delay between the two sheared pulse components. This analysis suggests that, as pulses approach the single-cycle limit, the resulting requirements on the calibration and stability of this delay become significant, requiring precision orders of magnitude higher than the scale of a wavelength. This is demonstrated by numerical simulations of SPIDER pulse reconstruction using actual data from a sub-two-cycle laser. We briefly propose methods to minimize the effects of this sensitivity in SPIDER and review variants of spectral shearing that attempt to avoid this difficulty

  16. 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.

  17. Meterwavelength Single-pulse Polarimetric Emission Survey. IV. The Period Dependence of Component Widths of Pulsars

    Science.gov (United States)

    Skrzypczak, Anna; Basu, Rahul; Mitra, Dipanjan; Melikidze, George I.; Maciesiak, Krzysztof; Koralewska, Olga; Filothodoros, Alexandros

    2018-02-01

    The core component width in normal pulsars, with periods (P) > 0.1 s, measured at the half-power point at 1 GHz, has a lower boundary line (LBL) that closely follows the P ‑0.5 scaling relation. This result is of fundamental importance for understanding the emission process and requires extended studies over a wider frequency range. In this paper we have carried out a detailed study of the profile component widths of 123 normal pulsars observed in the Meterwavelength Single-pulse Polarimetric Emission Survey at 333 and 618 MHz. The components in the pulse profile were separated into core and conal classes. We found that at both frequencies, the core, as well as the conal component widths versus period, had a LBL that followed the P ‑0.5 relation with a similar lower boundary. The radio emission in normal pulsars has been observationally shown to arise from a narrow range of heights around a few hundred kilometers above the stellar surface. In the past the P ‑0.5 relation has been considered as evidence for emission arising from last open dipolar magnetic field lines. We show that the P ‑0.5 dependence only holds if the trailing and leading half-power points of the component are associated with the last open field line. In such a scenario we do not find any physical motivation that can explain the P ‑0.5 dependence for both core and conal components as evidence for dipolar geometry in normal pulsars. We believe the period dependence is a result of a currently unexplained physical phenomenon.

  18. 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.

  19. A short review on the pulsed laser deposition of Er3+ ion doped oxide glass thin films for integrated optics

    International Nuclear Information System (INIS)

    Irannejad, M.; Zhao, Z.; Jose, G.; Steenson, D.P.; Jha, A.

    2010-01-01

    Short pulsed (ns) excimer laser was employed as a technique for the deposition of more than 2 μm thick glassy films from phosphorous pentoxide and tungsten lanthanum modified tellurite bulk glasses. High quality glass thin films with measured propagation loss less than 0.15, 0.71 and 2.3 dB.cm -1 were obtained after optimization of deposition parameters for silica, siloxane and semiconductor substrates. The optical, spectroscopic and microstructural properties of deposited thin films were compared with bulk glass materials for demonstrating the differences in the properties, which must be optimized for device engineering. Channel waveguides were fabricated after using reactive ion etching technique, up to 2 μm thickness by using CHF 3 and Ar gas mixture

  20. 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.

  1. A dense plasma focus-based neutron source for a single-shot detection of illicit materials and explosives by a nanosecond neutron pulse

    International Nuclear Information System (INIS)

    Gribkov, V A; Latyshev, S V; Miklaszewski, R A; Chernyshova, M; Drozdowicz, K; Wiacek, U; Tomaszewski, K; Lemeshko, B D

    2010-01-01

    Recent progress in a single-pulse Nanosecond Impulse Neutron Investigation System (NINIS) intended for interrogation of hidden objects by means of measuring elastically scattered neutrons is presented in this paper. The method uses very bright neutron pulses having duration of the order of 10 ns only, which are generated by dense plasma focus (DPF) devices filled with pure deuterium or DT mixture as a working gas. The small size occupied by the neutron bunch in space, number of neutrons per pulse and mono-chromaticity (ΔE/E∼1%) of the neutron spectrum provides the opportunity to use a time-of-flight (TOF) technique with flying bases of about a few metres. In our researches we used DPF devices having bank energy in the range 2-7 kJ. The devices generate a neutron yield of the level of 10 8 -10 9 2.45 MeV and 10 10 -10 11 14 MeV neutrons per pulse with pulse duration ∼10-20 ns. TOF base in the tests was 2.2-18.5 m. We have demonstrated the possibility of registering of neutrons scattered by the substances under investigation-1 litre bottles with methanol (CH 3 OH), phosphoric (H 2 PO 4 ) and nitric (HNO 3 ) acids as well as a long object-a 1 m gas tank filled with deuterium at high pressure. It is shown that the above mentioned short TOF bases and relatively low neutron yields are enough to distinguish different elements' nuclei composing the substance under interrogation and to characterize the geometry of lengthy objects in some cases. The wavelet technique was employed to 'clean' the experimental data registered. The advantages and restrictions of the proposed and tested NINIS technique in comparison with other methods are discussed.

  2. Production of neutrons up to 18 MeV in high-intensity, short-pulse laser matter interactions

    Energy Technology Data Exchange (ETDEWEB)

    Higginson, D. P. [Mechanical and Aerospace Engineering, University of California-San Diego, La Jolla, California 92093 (United States); Lawrence Livermore National Laboratory, Livermore, California 94440 (United States); McNaney, J. M.; Swift, D. C.; Mackinnon, A. J.; Patel, P. K. [Lawrence Livermore National Laboratory, Livermore, California 94440 (United States); Petrov, G. M.; Davis, J. [Naval Research Laboratory, Plasma Physics Division, Washington, DC 20375 (United States); Frenje, J. A. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Jarrott, L. C.; Tynan, G.; Beg, F. N. [Mechanical and Aerospace Engineering, University of California-San Diego, La Jolla, California 92093 (United States); Kodama, R.; Nakamura, H. [Institute of Laser Engineering, Osaka University, 2-5 Yamada-oka, Suita, Osaka 454-0871 (Japan); Lancaster, K. L. [STFC Rutherford Appleton Laboratory, Chilton, Oxon OX11OQX (United Kingdom)

    2011-10-15

    The generation of high-energy neutrons using laser-accelerated ions is demonstrated experimentally using the Titan laser with 360 J of laser energy in a 9 ps pulse. In this technique, a short-pulse, high-energy laser accelerates deuterons from a CD{sub 2} foil. These are incident on a LiF foil and subsequently create high energy neutrons through the {sup 7}Li(d,xn) nuclear reaction (Q = 15 MeV). Radiochromic film and a Thomson parabola ion-spectrometer were used to diagnose the laser accelerated deuterons and protons. Conversion efficiency into protons was 0.5%, an order of magnitude greater than into deuterons. Maximum neutron energy was shown to be angularly dependent with up to 18 MeV neutrons observed in the forward direction using neutron time-of-flight spectrometry. Absolutely calibrated CR-39 detected spectrally integrated neutron fluence of up to 8 x 10{sup 8} n sr{sup -1} in the forward direction.

  3. The effect of seasonal harvesting on a single-species discrete population model with stage structure and birth pulses

    International Nuclear Information System (INIS)

    Gao Shujing; Chen Lansun

    2005-01-01

    In this paper, we propose an exploited single-species discrete model with stage structure for the dynamics in a fish population for which births occur in a single pulse once per time period. Using the stroboscopic map, we obtain an exact cycle of the system, and obtain the threshold conditions for its stability. Bifurcation diagrams are constructed with the birth rate as the bifurcation parameter, and these are observed to display complex dynamic behaviors, including chaotic bands with period windows, pitch-fork and tangent bifurcation. This suggests that birth pulse provides a natural period or cyclicity that makes the dynamical behavior more complex. Moreover, we show that the timing of harvesting has a strong impact on the persistence of the fish population, on the volume of mature fish stock and on the maximum annual-sustainable yield. An interesting result is obtained that, after the birth pulse, the earlier culling the mature fish, the larger harvest can tolerate

  4. Space Vector Pulse Width Modulation Strategy for Single-Phase Three-Level CIC T-source Inverter

    DEFF Research Database (Denmark)

    Shults, Tatiana E.; Husev, Oleksandr O.; Blaabjerg, Frede

    2016-01-01

    This paper presents a novel space vector pulse-width modulation strategy for a single-phase three-level buck-boost inverter based on an impedance-source network. The case study system is based on T-source inverter with continuous input current. To demonstrate the improved performance of the inver......This paper presents a novel space vector pulse-width modulation strategy for a single-phase three-level buck-boost inverter based on an impedance-source network. The case study system is based on T-source inverter with continuous input current. To demonstrate the improved performance...... of the inverter, the strategy was compared the traditional pulse-width modulation. It is shown that the approach proposed has fewer switching states and does not suffer from neutral point misbalance....

  5. Megajoule-class single-pulse KrF laser test facility as a logical step toward inertial fusion commercialization

    International Nuclear Information System (INIS)

    Harris, D.B.; Pendergrass, J.H.

    1985-01-01

    The cost and efficiency of megajoule-class KrF laser single pulse test facilities have been examined. A baseline design is described which illuminates targets with 5 MJ with shaped 10-ns pulses. The system uses 24 main amplifiers and operates with an optics operating fluence of 4.0 J/cm 2 . This system has 9.0% efficiency and costs $200/joule. Tradeoff studies indicate that large amplifier modules and high fluences lead to the lowest laser system costs, but that only a 20% cost savings can be realized by going to amplifier modules larger than 200 kJ and/or fluences greater than 4 J/cm 2 . The role of the megajoule-class single-pulse test facility towards inertial fusion commercialization will also be discussed

  6. A 10-TW Pulsed Facility "PIRIT" for Investigation of Short-Wave Radiation Generation.

    Science.gov (United States)

    Popkov, N F; Ryaslov, E A; Kargin, V I; Pikar', A S; Kotel'nikov, D V; Melkozerov, A V

    1995-01-01

    The results of experiments with a plasma x-ray source in the PIRIT-2000 facility are presented in this paper. The facility is designed with module capacitive energy storage energizing vacuum inductive storage. The formation of a rapidly growing current pulse as well as its commutation on a load was carried out by a plasma opening switch. A vacuum diode as well as various types of plasma loads can be used for the generation of a high-power x-ray flux. The storage energy of a 54-module capacitive storage is up to 2 MJ, its inductance is 15 nH, and its output voltage is 500 kV. The peak current in the plasma load constituted 4 MA with a 150-ns rise time. The maximum integral energy output of x radiation measured by an open thermocouple calorimeter was as high as 100 kJ, while the primary storage energy was 1 MJ. The plasma load usage at a current of 4 MA ensured a 100-kJ generation in x-ray radiation and the density of the radiation flux at a distance of 1 m from the source was as much as 0.8 J/cm2, while near the source it was 10 J/cm2.

  7. 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

  8. Microstructural evolution and mechanical performance of resistance spot welded DP1000 steel with single and double pulse welding

    NARCIS (Netherlands)

    Chabok, Ali; van der Aa, Ellen; De Hosson, Jeff; Pei, Yutao T.

    2017-01-01

    Two welding schemes of single and double pulse were used for the resistance spot welding of DP1000 dual phase steel. The changes in the mechanical performance and variant pairing of martensite under two different welding conditions were scrutinized. It is demonstrated that, although both welds fail

  9. Linear and non-linear carrier-envelope phase difference effects in interactions of ultra-short laser pulses with a metal nano-layer

    International Nuclear Information System (INIS)

    Varro, S.

    2006-01-01

    Complete test of publication follows. On the basis of classical electrodynamics the reflection and transmission of an ultra-short laser pulse impinging on a metal nano-layer have been analysed. The thickness of the layer was assumed to be of the order of 2-10 nm, and the metallic electrons were represented by a surface current density at the plane boundary of a dielectric substrate. It has been shown that in the scattered fields a non-oscillatory wake-field appears following the main pulse with an exponential decay and with a definite sign of the electric and magnetic fields. The characteristic time of these wake-fields is inversely proportional to the square of the plasma frequency and to the thickness of the metal nano-layer, and can be of order or larger then the original pulse duration. The magnitude of these wake-fields is proportional with the incoming field strength - so this is a linear effect - and the definite sign of them is governed by the cosine of the carrier-envelope phase difference of the incoming ultrashort laser pulse. As a consequence, when we let such a wake-field excite the electrons of a secondary target - say a plasma, a metal surface or a gas - we obtain 100 percent modulation depth in the electron signal in a given direction. This scheme can perhaps serve as a basis for the construction of a robust linear carrier-envelope phase difference mater. At relativistic laser intensities the target becomes a plasma layer generated, e.g. by the rising part of the incoming laser pulse. An approximate analytic solution has been given for the system of the coupled Maxwell-Lorentz equations describing the dynamics of the surface current (representing the plasma electrons) and the composite radiation field. With the help of these solutions the Fourier components of the reflected and transmitted radiation have been calculated. The nonlinearities stemming from the relativistic kinematics lead to the appearance of higher-order harmonics in the scattered

  10. Pulsed IR Heating Studies of Single-Molecule DNA Duplex Dissociation Kinetics and Thermodynamics

    Science.gov (United States)

    Holmstrom, Erik D.; Dupuis, Nicholas F.; Nesbitt, David J.

    2014-01-01

    Single-molecule fluorescence spectroscopy is a powerful technique that makes it possible to observe the conformational dynamics associated with biomolecular processes. The addition of precise temperature control to these experiments can yield valuable thermodynamic information about equilibrium and kinetic rate constants. To accomplish this, we have developed a microscopy technique based on infrared laser overtone/combination band absorption to heat small (≈10−11 liter) volumes of water. Detailed experimental characterization of this technique reveals three major advantages over conventional stage heating methods: 1), a larger range of steady-state temperatures (20–100°C); 2), substantially superior spatial (≤20 μm) control; and 3), substantially superior temporal (≈1 ms) control. The flexibility and breadth of this spatial and temporally resolved laser-heating approach is demonstrated in single-molecule fluorescence assays designed to probe the dissociation of a 21 bp DNA duplex. These studies are used to support a kinetic model based on nucleic acid end fraying that describes dissociation for both short (10 bp) DNA duplexes. These measurements have been extended to explore temperature-dependent kinetics for the 21 bp construct, which permit determination of single-molecule activation enthalpies and entropies for DNA duplex dissociation. PMID:24411254

  11. Continuous single pulse resolved measurement of beam diameters at 200 kHz using optical transmission filters

    Science.gov (United States)

    Fruechtenicht, Johannes; Letsch, Andreas; Voss, Andreas; Abdou Ahmed, Marwan; Graf, Thomas

    2012-02-01

    We present a novel laser beam measurement setup which allows the determination of the beam diameter for each single pulse of a pulsed laser beam at repetition rates of up to 200 kHz. This is useful for online process-parameter control e.g. in micromachining or for laser source characterization. Basically, the developed instrument combines spatial transmission filters specially designed for instantaneous optical determination of the second order moments of the lateral intensity distribution of the light beam and photodiodes coupled to customized electronics. The acquisition is computer-based, enabling real-time operation for online monitoring or control. It also allows data storage for a later analysis and visualization of the measurement results. The single-pulse resolved beam diameter can be measured and recorded without any interruption for an unlimited number of pulses. It is only limited by the capacity of the data storage means. In our setup a standard PC and hard-disk provided 2 hours uninterrupted operation and recording of varying beam diameters at 200 kHz. This is about three orders of magnitude faster than other systems. To calibrate our device we performed experiments in cw and pulsed regimes and the obtained results were compared to those obtained with a commercial camera based system. Only minor deviations of the beam diameter values between the two instruments were observed, proving the reliability of our approach.

  12. An injection seeded single frequency Nd:YAG Q-switched laser with precisely controllable laser pulse firing time

    Science.gov (United States)

    Wu, Frank F.; Khizhnyak, Anatoliy; Markov, Vladimir

    2010-02-01

    We have realized a single frequency Q-switched Nd:YAG laser with precisely controllable lasing time and thus enabled synchronization of multi-laser systems. The use of injection seeding to the slave ring oscillator results in unidirectional Q-switched laser oscillation with suppression of bidirectional Q-switched oscillation that otherwise would be initiated from spontaneous emission if the seeding laser is not present. Under normal condition, the cavity is high in loss during the pumping period; then a Pockels cell opens the cavity to form the pulse build up, with a second Pockels cell to perform cavity dumping, generating the Q-switched pulse output with optimized characteristics. The two Pockels cells can be replaced by a single unit if an adjustable gated electrical pulse is applied to the Pockels cell in which the pulse front is used to open the cavity and the falling edge to dump the laser pulse. Proper selection of the pump parameters and Pockels-cell gating enables operation of the system in a mode in which the Q-switched pulse can be formed only under the seeding condition. The advantage of the realized regime is in stable laser operation with no need in adjustment of the seeded light wavelength and the mode of the cavity. It is found that the frequency of the Q-switched laser radiation matches well to the injected seeded laser mode. By using two-stage amplifiers, an output energy better than 300 mJ has been achieved in MOPA configuration without active control of the cavity length and with pulse width adjustability from several nanoseconds to 20 ns. The Q-switched oscillator operates not only at precisely controlled firing time but also can be tuned over wide range. This will enable multi-laser systems synchronization and frequency locking down each other if necessary.

  13. Investigating emotional top down modulation of ambiguous faces by single pulse TMS on early visual cortices

    Directory of Open Access Journals (Sweden)

    Zachary Adam Yaple

    2016-06-01

    Full Text Available Top-down processing is a mechanism in which memory, context and expectation are used to perceive stimuli. For this study we investigated how emotion content, induced by music mood, influences perception of happy and sad emoticons. Using single pulse TMS we stimulated right occipital face area (rOFA, primary visual cortex (V1 and vertex while subjects performed a face-detection task and listened to happy and sad music. At baseline, incongruent audio-visual pairings decreased performance, demonstrating dependence of emotion while perceiving ambiguous faces. However, performance of face identification decreased during rOFA stimulation regardless of emotional content. No effects were found between Cz and V1 stimulation. These results suggest that while rOFA is important for processing faces regardless of emotion, V1 stimulation had no effect. Our findings suggest that early visual cortex activity may not integrate emotional auditory information with visual information during emotion top-down modulation of faces.

  14. Analysis of Dietz's single, rectangular pulse theory for the generation of radiation via photoelectrons

    International Nuclear Information System (INIS)

    Dipp, T.M.

    1993-12-01

    The generation of radiation via photoelectrons induced off of a conducting surface has been analytically modeled and computationally simulated by several researchers. This paper analyzes and compares Dietz's theory predictions with my research to form a unified foundation of consistent, inter-supporting results that should provide confidence in the independently performed basic research and resulting scaling laws and predictions. In doing so, this paper concentrated on Dietz's small-spot, single, rectangular, ''weak'' pulse theory and equations, which involve nonrelativistic, monoenergetic photoelectrons emitted normal to a conducting surface in vacuum. In this paper I: (1) analytically compare Dietz's theory equations with my theory equations, (2) compare Dietz's theoretical scaling laws with my Particle-In-Cell (PIC) code simulation results, and (3) make Dietz's equations easier to use in predicting and optimizing photoelectron-generated radiation. As a result, it is shown that Dietz's equations match my theory's equations in their predicted scaling laws, differing only slightly in their coefficients and unique model parameters. Also, Dietz's equations generally agree with the PIC code results. Finally, optimization analysis showed that theoretical conversion efficiencies for typical real metals can meet and exceed values of 10 -5 if optimal photon energies of 15 to 20 eV are used. Even better efficiencies should be possible if the small-spot constraint is violated as well

  15. Resonant ablation of single-wall carbon nanotubes by femtosecond laser pulses

    International Nuclear Information System (INIS)

    Arutyunyan, N R; Komlenok, M S; Kononenko, V V; Pashinin, V P; Pozharov, A S; Konov, V I; Obraztsova, E D

    2015-01-01

    The thin 50 nm film of bundled arc-discharge single-wall carbon nanotubes was irradiated by femtosecond laser pulses with wavelengths 675, 1350 and 1745 nm corresponding to the absorption band of metallic nanotubes E 11 M , to the background absorption and to the absorption band of semiconducting nanotubes E 11 S , respectively. The aim was to induce a selective removal of nanotubes of specific type from the bundled material. Similar to conducted thermal heating experiments, the effect of laser irradiation results in suppression of all radial breathing modes in the Raman spectra, with preferential destruction of the metallic nanotubes with diameters less than 1.26 nm and of the semiconducting nanotubes with diameters 1.36 nm. However, the etching rate of different nanotubes depends on the wavelength of the laser irradiation. It is demonstrated that the relative content of nanotubes of different chiralities can be tuned by a resonant laser ablation of undesired nanotube fraction. The preferential etching of the resonant nanotubes has been shown for laser wavelengths 675 nm (E 11 M ) and 1745 nm (E 11 S ). (paper)

  16. Pulsed x-ray induced attenuation measurements of single mode optical fibers and coupler materials

    International Nuclear Information System (INIS)

    Johan, A.; Charre, P.

    1994-01-01

    Pulsed X-ray induced transient radiation attenuation measurements of single mode optical fibers have been performed versus total dose, light wavelength, optical power and fiber coil diameter in order to determine the behavior of parameters sensitive to ionizing radiation. The results did not show any photobleaching phenomenon and the attenuation was found independent of the spool diameter. As expected, transient attenuation was lower for higher wave-lengths. The recovery took place in the millisecond range and was independent of total dose, light wavelength and optical power. In optical modules and devices a large range of behaviors was observed according to coupler material i.e., Corning coupler showed a small peak attenuation that remained more than one day later; on the other hand LiTaO 3 material experienced an order of magnitude higher peak attenuation and a recovery in the millisecond range. For applications with optical fibers and integrated optics devices the authors showed that in many cases the optical fiber (length above 100 m) is the most sensitive device in a transient ionizing radiation field

  17. Design of a high-pressure single pulse shock tube for chemical kinetic investigations

    International Nuclear Information System (INIS)

    Tranter, R. S.; Brezinsky, K.; Fulle, D.

    2001-01-01

    A single pulse shock tube has been designed and constructed in order to achieve extremely high pressures and temperatures to facilitate gas-phase chemical kinetic experiments. Postshock pressures of greater than 1000 atmospheres have been obtained. Temperatures greater than 1400 K have been achieved and, in principle, temperatures greater than 2000 K are easily attainable. These high temperatures and pressures permit the investigation of hydrocarbon species pyrolysis and oxidation reactions. Since these reactions occur on the time scale of 0.5--2 ms the shock tube has been constructed with an adjustable length driven section that permits variation of reaction viewing times. For any given reaction viewing time, samples can be withdrawn through a specially constructed automated sampling apparatus for subsequent species analysis with gas chromatography and mass spectrometry. The details of the design and construction that have permitted the successful generation of very high-pressure shocks in this unique apparatus are described. Additional information is provided concerning the diaphragms used in the high-pressure shock tube

  18. Technique and Short-Term Outcomes of Single-Port Surgery for Rectal Cancer

    DEFF Research Database (Denmark)

    Bulut, O; Aslak, K K; Rosenstock, S

    2013-01-01

    Although conventional laparoscopic surgery is less traumatic than open surgery, it does cause tissue trauma and multiple scar formation. The size and number of ports determine the extent of the trauma. Single-port laparoscopic surgery is assumed to minimize and perhaps eliminate the potential adv...... adverse effects of conventional laparoscopy. The aim of this study was to examine short-term outcomes of single-port laparoscopic surgery for rectal cancer.......Although conventional laparoscopic surgery is less traumatic than open surgery, it does cause tissue trauma and multiple scar formation. The size and number of ports determine the extent of the trauma. Single-port laparoscopic surgery is assumed to minimize and perhaps eliminate the potential...

  19. Spatially and Temporally Resolved Atomic Oxygen Measurements in Short Pulse Discharges by Two Photon Laser Induced Fluorescence

    Science.gov (United States)

    Lempert, Walter; Uddi, Mruthunjaya; Mintusov, Eugene; Jiang, Naibo; Adamovich, Igor

    2007-10-01

    Two Photon Laser Induced Fluorescence (TALIF) is used to measure time-dependent absolute oxygen atom concentrations in O2/He, O2/N2, and CH4/air plasmas produced with a 20 nanosecond duration, 20 kV pulsed discharge at 10 Hz repetition rate. Xenon calibrated spectra show that a single discharge pulse creates initial oxygen dissociation fraction of ˜0.0005 for air like mixtures at 40-60 torr total pressure. Peak O atom concentration is a factor of approximately two lower in fuel lean (φ=0.5) methane/air mixtures. In helium buffer, the initially formed atomic oxygen decays monotonically, with decay time consistent with formation of ozone. In all nitrogen containing mixtures, atomic oxygen concentrations are found to initially increase, for time scales on the order of 10-100 microseconds, due presumably to additional O2 dissociation caused by collisions with electronically excited nitrogen. Further evidence of the role of metastable N2 is demonstrated from time-dependent N2 2^nd Positive and NO Gamma band emission spectroscopy. Comparisons with modeling predictions show qualitative, but not quantitative, agreement with the experimental data.

  20. Wavelength dependence of the single pulse femtosecond laser ablation threshold of indium phosphide in the 400-2050 nm range

    International Nuclear Information System (INIS)

    Borowiec, A.; Tiedje, H.F.; Haugen, H.K.

    2005-01-01

    We present single pulse femtosecond laser ablation threshold measurements of InP obtained by optical, scanning electron, and atomic force microscopy. The experiments were conducted with laser pulses 65-175 fs in duration, in the wavelength range from 400 to 2050 nm, covering the photon energy region above and below the bandgap of InP. The ablation thresholds determined from depth and volume measurements varied from 87 mJ/cm 2 at 400 nm to 250 mJ/cm 2 at 2050 nm. In addition, crater depths and volumes were measured over a range of laser fluences extending well above the ablation threshold