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Sample records for adiabatic-rectangular pulse train

  1. Academic Training - Pulsed SC Magnets

    Françoise Benz

    2006-01-01

    2005-2006 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 2, 3, June 29, 30, 31 May, 1, 2 June 11:00-12:00 - Auditorium, bldg 500 Pulsed SC Magnets by M. Wilson Lecture 1. Introduction to Superconducting Materials Type 1,2 and high temperature superconductors; their critical temperature, field & current density. Persistent screening currents and the critical state model. Lecture 2. Magnetization and AC Loss How screening currents cause irreversible magnetization and hysteresis loops. Field errors caused by screening currents. Flux jumping. The general formulation of ac loss in terms of magnetization. AC losses caused by screening currents. Lecture 3. Twisted Wires and Cables Filamentary composite wires and the losses caused by coupling currents between filaments, the need for twisting. Why we need cables and how the coupling currents in cables contribute more ac loss. Field errors caused by coupling currents. Lecture 4. AC Losses in Magnets, Cooling and Measurement Summary of all loss mech...

  2. Powerful nanosecond pulse train generator

    A generator permitting to shape on the load pulsed with the repetition frequency of 103-106 Hz and more is described. The amplitude of shaped voltage pulses is up to 150 kV at pulse duration equal to 50 ns. The generator comprises connected in-series with the load two shaping and two transmission lines realized on the base of the KVI-300 low-ohmic cable. The shaping lines are supplied from two independently connected pulse voltage generators for obtaining time interval between pulses > 10-6 s; they may be also supplied from one generator for obtaining time interval -6 s. At the expense of reducing losses in the discharge circuit the amplitude of the second pulse grows with increase of time interval between pulses up to 300 ns, further on the curve flat-topping exists. The described generator is used in high-current accelerators, in which the primary negative pulse results in generation of explosive-emission plasma, and the second positive pulse provides ion beam shaping including ions of heavy metal used for production of a potential electrode. The generator multipulse mode is used for successive ion acceleration in the transport system

  3. Random Pulse Train Spectrum Calculation Unleashed

    Stepanov, Sander; Venetsanopoulos, Anastasios

    2015-01-01

    For the first time the problem of the full solution for the calculation of the power spectrum density of the random pulse train is solved. This well known problem led to a mistaken publication in the past and even its partial solution was considered worthy of publication in a textbook. The little known solution for only the continues random pulse train spectrum is explained by examples and is extended to cover each signal having a discrete spectrum, too. A developed approach is used to derive...

  4. Spectral signature of short attosecond pulse trains

    Mansten, E; Mauritsson, J; Ruchon, T; LHuillier, A; Tate, J; Gaarde, M B; Eckle, P; Guandalini, A; Holler, M; Schapper, F; Gallmann, L; Keller, U

    2008-01-01

    We report experimental measurements of high-order harmonic spectra generated in Ar using a carrier-envelope-offset (CEO) stabilized 12 fs, 800nm laser field and a fraction (less than 10%) of its second harmonic. Additional spectral peaks are observed between the harmonic peaks, which are due to interferences between multiple pulses in the train. The position of these peaks varies with the CEO and their number is directly related to the number of pulses in the train. An analytical model, as well as numerical simulations, support our interpretation.

  5. Complete temporal reconstruction of attosecond high-harmonic pulse trains

    Kim, Kyung Taec; Ko, Dong Hyuk; Park, Juyun; Tosa, Valer; Nam, Chang Hee, E-mail: chnam@kaist.ac.k [Department of Physics and Coherent X-ray Research Center, KAIST, Daejeon 305-701 (Korea, Republic of)

    2010-08-15

    The method of complete reconstruction of attosecond bursts has been demonstrated for attosecond high-harmonic pulse trains. The retrieved harmonic field provided detailed information about the envelope and the individual attosecond pulses contained in the attosecond pulse train. The time-frequency analysis revealed complicated spectral chirp structures and the contribution of different quantum paths to attosecond pulse formation.

  6. Power Spectra of Multipath Faded Pulse Trains

    Ridolfi, Andrea; Win, Moe

    2005-01-01

    We address the problem of modeling received pulse trains in a multipath fading channel and of computing their exact spectrum. We propose a model based on point processes. Such model is very general, simple and tractable and it allows to account for various phenomena that affect the transmission. We then give the exact spectrum of the output of such a model. Spectral formula of specific configurations are then derived from a singular general formula, where the various features of the channe...

  7. Chaos-induced pulse trains in the ionization of hydrogen

    We predict that a hydrogen atom in parallel electric and magnetic fields, excited by a short laser pulse to an energy above the classical saddle, ionizes via a train of electron pulses. These pulses are a consequence of classical chaos induced by the magnetic field. We connect the structure of this pulse train (e.g., pulse size and spacing) to fractal structure in the classical dynamics. This structure displays a weak self-similarity, which we call 'epistrophic self-similarity'. We demonstrate how this self-similarity is reflected in the pulse train

  8. High-power pulse trains excited by modulated continuous waves

    Wang, Yan; Song, Lijun; Li, Lu; Malomed, Boris A.

    2015-01-01

    Pulse trains growing from modulated continuous waves (CWs) are considered, using solutions of the Hirota equation for solitons on a finite background. The results demonstrate that pulses extracted from the maximally compressed trains can propagate preserving their shape and forming robust arrays. The dynamics of double high-power pulse trains produced by modulated CWs in a model of optical fibers, including the Raman effect and other higher-order terms, is considered in detail too. It is demo...

  9. Pulse-train control of photofragmentation at constant field energy

    Tiwari, Ashwani Kumar; Henriksen, Niels Engholm

    2014-01-01

    We consider a phaselocked two-pulse sequence applied to photofragmentation in the weak-field limit. The two pulses are not overlapping in time, i.e., the energy of the pulse-train is constant for all time delays. It is shown that the relative yield of excited Br* in the nonadiabatic process: I + Br*←IBr...

  10. High-power pulse trains excited by modulated continuous waves

    Wang, Yan; Li, Lu; Malomed, Boris A

    2015-01-01

    Pulse trains growing from modulated continuous waves (CWs) are considered, using solutions of the Hirota equation for solitons on a finite background. The results demonstrate that pulses extracted from the maximally compressed trains can propagate preserving their shape and forming robust arrays. The dynamics of double high-power pulse trains produced by modulated CWs in a model of optical fibers, including the Raman effect and other higher-order terms, is considered in detail too. It is demonstrated that the double trains propagate in a robust form, with frequencies shifted by the Raman effect.

  11. Generation of laser pulse trains for tests of multi-pulse laser wakefield acceleration

    Shalloo, R. J.; Corner, L.; Arran, C.; Cowley, J.; Cheung, G.; Thornton, C.; Walczak, R.; Hooker, S. M.

    2016-09-01

    In multi-pulse laser wakefield acceleration (MP-LWFA) a plasma wave is driven by a train of low-energy laser pulses separated by the plasma period, an approach which offers a route to driving plasma accelerators with high efficiency and at high pulse repetition rates using emerging technologies such as fibre and thin-disk lasers. Whilst these laser technologies are in development, proof-of-principle tests of MP-LWFA require a pulse train to be generated from a single, high-energy ultrafast pulse. Here we demonstrate the generation of trains of up to 7 pulses with pulse separations in the range 150-170 fs from single 40 fs pulses produced by a Ti:sapphire laser.

  12. Method for integrating a train of fast, nanosecond wide pulses

    This paper describes a method used to integrate a train of fast, nanosecond wide pulses. The pulses come from current transformers in a RF LINAC beamline. Because they are ac signals and have no dc component, true mathematical integration would yield zero over the pulse train period or an equally erroneous value because of a dc baseline shift. The circuit used to integrate the pulse train first stretches the pulses to 35 ns FWHM. The signals are then fed into a high-speed, precision rectifier which restores a true dc baseline for the following stage - a fast, gated integrator. The rectifier is linear over 55dB in excess of 25 MHz, and the gated integrator is linear over a 60 dB range with input pulse widths as short as 16 ns. The assembled system is linear over 30 dB with a 6 MHz input signal

  13. Krytron switch for single pulse selection from a mode-locked pulse train

    We present detailed technical data on a Krytron switch circuit which is used for the single pulse selection from a pulse train of a mode-locked laser. Design considerations for the triggering circuit of the Krytron are described and the optimum selections of avalanche transistors are shown. Data on the delay time and life characteristics of Krytron tubes are shown. A very reliable pulse selection from a mode-locked pulse train has been realized. The amplitude variation of the selected pulse was less than +-2.5%. (author)

  14. On-line controlled pulse-train generator for pulsed EPR spectrometer-relaxometer

    A pulse-train generator including 11 output channels program operated with the ''Elektronika D3-28'' computer is described. High flexibility in shaping different pulse combinations permits to automize the control of EPR relaxometer in all the regimes of investigations. The maximum number of intervals generated by each channel is 16. The range of pulse train variation is 1 μs-4x103 s

  15. Short pulse laser train for laser plasma interaction experiments

    A multiframe, high-time resolution pump-probe diagnostic consisting of a consecutive train of ultrashort laser pulses (∼ps) has been developed for use with a chirped pulse amplification (CPA) system. A system of high quality windows is used to create a series of 1054 nm picosecond-laser pulses which are injected into the CPA system before the pulse stretcher and amplifiers. By adding or removing windows in the pulse train forming optics, the number of pulses can be varied. By varying the distance and thickness of the respective optical elements, the time in between the pulses, i.e., the time in between frames, can be set. In our example application, the CPA pulse train is converted to 527 nm using a KDP crystal and focused into a preformed plasma and the reflected laser light due to stimulated Raman scattering is measured. Each pulse samples different plasma conditions as the plasma evolves in time, producing more data on each laser shot than with a single short pulse probe. This novel technique could potentially be implemented to obtain multiple high-time resolution measurements of the dynamics of physical processes over hundreds of picoseconds or even nanoseconds with picosecond resolution on a single shot

  16. The Simplest Method for Generation of an Attosecond Pulse Train

    Katsuragawa Masayuki

    2013-03-01

    Full Text Available We report an extremely simple approach to generate an attosecond pulse train from more than octave-spanning discrete spectrum by only positioning transparent materials into the optical path without spatially dispersing the frequency components.

  17. Time-Grating for the Generation of STUD Pulse Trains

    Zheng, Jun; Wang, Shi-Wei; Xu, Jian-Qiu

    2013-04-01

    Spike train of uneven duration or delay (STUD) pulses hold potential for laser-plasma interaction (LPI) control in laser fusion. The technique based on time grating is applied to generate an STUD pulse train. Time grating, a temporal analogy of the diffraction grating, can control the pulse width, shape, and repetition rate easily through the use of electro-optical devices. The pulse width and repetition rate are given by the modulation frequency and depth of the phase modulation function in theory and numerical calculation. The zero-chirped phase modulation is good for the compression effect of the time grating. A principle experiment of two pulses interfering is shown to verify the time grating function.

  18. Monopolar Intracochlear Pulse Trains Selectively Activate the Inferior Colliculus

    Schoenecker, Matthew C.; Bonham, Ben H.; Stakhovskaya, Olga A.; Snyder, Russell L.; Leake, Patricia A.

    2012-01-01

    Previous cochlear implant studies using isolated electrical stimulus pulses in animal models have reported that intracochlear monopolar stimulus configurations elicit broad extents of neuronal activation within the central auditory system—much broader than the activation patterns produced by bipolar electrode pairs or acoustic tones. However, psychophysical and speech reception studies that use sustained pulse trains do not show clear performance differences for monopolar versus bipolar confi...

  19. Femtosecond laser pulse train interaction with dielectric materials

    Caulier, O Dematteo; Chimier, B; Skupin, S; Bourgeade, A; Léger, C Javaux; Kling, R; Hönninger, C; Lopez, J; Tikhonchuk, V; Duchateau, G

    2015-01-01

    We investigate the interaction of trains of femtosecond microjoule laser pulses with dielectric materials by means of a multi-scale model. Our theoretical predictions are directly confronted with experimental observations in soda-lime glass. We show that due to the low heat conductivity, a significant fraction of the laser energy can be accumulated in the absorption region. Depending on the pulse repetition rate, the material can be heated to high temperatures even though the single pulse energy is too low to induce a significant material modification. Regions heated above the glass transition temperature in our simulations correspond very well to zones of permanent material modifications observed in the experiments.

  20. Femtosecond laser pulse train interaction with dielectric materials

    Dematteo Caulier, O.; Mishchik, K.; Chimier, B.; Skupin, S.; Bourgeade, A.; Javaux Léger, C.; Kling, R.; Hönninger, C.; Lopez, J.; Tikhonchuk, V.; Duchateau, G.

    2015-11-01

    The interaction of trains of femtosecond microjoule laser pulses with dielectric materials by means of a multi-scale model is investigated. Theoretical predictions are directly confronted with experimental observations in soda-lime glass. It is shown that due to the low heat conductivity, a significant fraction of the laser energy can be accumulated in the absorption region. Depending on the pulse repetition rate, the material can be heated to high temperatures even though the single pulse energy is too low to induce a significant material modification. Regions heated above the glass transition temperature in the simulations correspond very well to zones of permanent material modifications observed in the experiments. It turns out that pulse-to-pulse variations of the laser absorption are negligible and of minor influence to permanent material modifications.

  1. Gating attosecond pulse train generation using multicolor laser fields

    The process of high-order harmonic generation leads to the production of a train of attosecond-duration extreme ultraviolet (XUV) pulses, with one pulse emitted per optical half-cycle. For attosecond pump-probe experiments, a single, isolated attosecond pulse is preferable, requiring an almost continuous spectrum. We show experimentally and numerically that the addition of a second laser field, and later a third, at a noncommensurate frequency relative to the driving field can modify the subcycle shape of the electric field, leading to the appearance of additional spectral components between the usual odd harmonics and in some cases a quasicontinuum. We perform a parametric study of the frequency ratio between the two first laser fields, the result of which is in good agreement with theoretical selection rules. We also show numerically that using three laser frequencies from an optical parametric amplifier can achieve a single attosecond pulse from a 24-fs laser pulse.

  2. Frequency Stepped Pulse Train Modulated Wind Sensing Lidar

    Olesen, Anders Sig; Pedersen, Anders Tegtmeier; Rottwitt, Karsten

    2011-01-01

    In this paper a wind sensing lidar utilizing a Frequency Stepped Pulse Train (FSPT) is demonstrated. One of the advantages in the FSTP lidar is that it enables direct measurement of wind speed as a function of distance from the lidar. Theoretically the FSPT lidar continuously produces measurements...

  3. Hand-held pulse-train-analysis instrument

    A portable hand-held pulse-train-analysis instrument uses a number-oriented microprocessor sequenced by a single component microprocessor. The incorporation of new CMOS integrated circuits makes possible complex analysis in a small, easily operated, battery-powered unit. The instrument solves an immediate problem with threshold setting of plastic scintillators and promises numerous other applications

  4. Attosecond pulse trains as multi-color coherent control

    Hernández, J V

    2009-01-01

    We present a general description of the interaction between multi-color laser pulses and atoms and molecules, focusing on the experimentally relevant example of infrared (IR) pulses overlapped with attosecond pulse trains (APTs). This formulation reveals explicitly and analytically the role of the delay between the IR pulse and APT as a coherent control parameter. Our formulation also shows the nearly equivalent roles of the delay and the carrier-envelope phase in controlling the interference between different multiphoton pathways. We illustrate these points by investigating the single ionization of He and introduce dressed adiabatic hyperspherical potentials to aid the discussion. We confirm the predictions with a full-dimensional, two-electron solution of the time-dependent Schr\\"odinger equation.

  5. Development of a compact soft X-ray laser using a pulse-train laser. 4

    Time behaviour of gain coefficients was studied for the two different pulse train-lasers; one is a normal pulse-train, and the other modified one. The duration time of gain is larger for the modified pulse-train laser compared with the normal one. (author)

  6. Femtosecond-pulse-train ionization of Rydberg wave packets

    Simonsen, Sigrid Ina; Sørngård, Stian Astad; Førre, Morten; Hansen, Jan Petter

    2012-01-01

    We calculate, based on first-order perturbation theory, the total and differential ionization probabilities from a dynamic periodic Rydberg wave packet of a given n-shell exposed to a train of femtosecond laser pulses. The total probability is shown to depend crucially on the laser repetition rate: For certain frequencies the ionization probability vanishes, while for others it becomes very large. The origin of this effect is the strong dependence of the ionization probability on ...

  7. First-principles electron dynamics control simulation of diamond under femtosecond laser pulse train irradiation

    A real-time and real-space time-dependent density functional is applied to simulate the nonlinear electron-photon interactions during shaped femtosecond laser pulse train ablation of diamond. Effects of the key pulse train parameters such as the pulse separation, spatial/temporal pulse energy distribution and pulse number per train on the electron excitation and energy absorption are discussed. The calculations show that photon-electron interactions and transient localized electron dynamics can be controlled including photon absorption, electron excitation, electron density, and free electron distribution by the ultrafast laser pulse train. (paper)

  8. Spectral Effects for an Ultrashort Pulse Train Propagating in a Two-Level Atom Medium

    LIU Bing-Xin; GONG Shang-Qing; SONG Xiao-Hong; LI Ru-Xin; XU Zhi-Zhan

    2005-01-01

    @@ We investigate the spectra of a femtosecond pulse train propagating in a resonant two-level atom (TLA) medium.It is found that higher spectral components can be produced even for a 2π femtosecond pulse train. Furthermore,the spectral effects depend crucially on both the relative shift φ and the delay time τ between the successive pulses of the femtosecond pulse train.

  9. Trains of electron pulses generation using multi-stage cavities

    Kamada, Masaki; Mori, Michiya; Sugawara, Kazuyoshi; Yamada, Yoko; Kurihara, Kazuteru; Shirasaka, Haruki; Nishiguchi, Takashi; Ando, Ritoku; Kamada, Keiichi [Kanazawa Univ., Faculty of Science, Dept. of Physics, Kanazawa, Ishikawa (Japan)

    2002-06-01

    Automodulation of an intense relativistic electron beam was reexamined experimentally to obtain trains of subnanosecond electron bunches. Sufficient beam modulation with frequency larger than 1 GHz was expected for the trains of subnanosecond bunches. It was obtained when a short pulse electron beam with energy of 550 keV, current of 4 kA, pulse duration of 12 ns and current rise time of 2ns was injected to a series of four coaxial cavities with the length of 75 mm. However, only a poor modulation was observed when a long pulse electron beam of 700 keV, 4 kA, 175 ns with current rise time of 20 ns was injected to the same cavities. Transmission line theory as well PIC code simulation suggested that the round trip time for the electromagnetic wave in the cavity must be longer than the rise time of the beam current to obtain the high level current modulation. Therefore, we studied experimentally how the ratio between the beam current rise time and the length of the cavity affects on the level of current modulation. Single cavity experiments were carried out with the short pulse beam. Single cavity with the length of 75, 150 or 300 mm was utilized. The round trip times for 75 and 150 mm cavities are shorter than the current rise time of 2 ns. The experiments with a 75 or 150 mm cavity resulted in suppression of the modulation amplitude. In the case of a 300 mm cavity, the high level modulation was obtained. The simulation results showed good agreements with the experimental results. We employed a series of cavities with decreasing lengths to improve the current rise time. For the short pulse beam, the high level current 1 GHz modulation was obtained when two 75 mm cavities were set at the downstream side of cavities with lengths of 300 mm and 150 mm. (author)

  10. Trains of electron pulses generation using multi-stage cavities

    Automodulation of an intense relativistic electron beam was reexamined experimentally to obtain trains of subnanosecond electron bunches. Sufficient beam modulation with frequency larger than 1 GHz was expected for the trains of subnanosecond bunches. It was obtained when a short pulse electron beam with energy of 550 keV, current of 4 kA, pulse duration of 12 ns and current rise time of 2ns was injected to a series of four coaxial cavities with the length of 75 mm. However, only a poor modulation was observed when a long pulse electron beam of 700 keV, 4 kA, 175 ns with current rise time of 20 ns was injected to the same cavities. Transmission line theory as well PIC code simulation suggested that the round trip time for the electromagnetic wave in the cavity must be longer than the rise time of the beam current to obtain the high level current modulation. Therefore, we studied experimentally how the ratio between the beam current rise time and the length of the cavity affects on the level of current modulation. Single cavity experiments were carried out with the short pulse beam. Single cavity with the length of 75, 150 or 300 mm was utilized. The round trip times for 75 and 150 mm cavities are shorter than the current rise time of 2 ns. The experiments with a 75 or 150 mm cavity resulted in suppression of the modulation amplitude. In the case of a 300 mm cavity, the high level modulation was obtained. The simulation results showed good agreements with the experimental results. We employed a series of cavities with decreasing lengths to improve the current rise time. For the short pulse beam, the high level current 1 GHz modulation was obtained when two 75 mm cavities were set at the downstream side of cavities with lengths of 300 mm and 150 mm. (author)

  11. A neuron model of stochastic resonance using rectangular pulse trains.

    Danziger, Zachary; Grill, Warren M

    2015-02-01

    Stochastic resonance (SR) is the enhanced representation of a weak input signal by the addition of an optimal level of broadband noise to a nonlinear (threshold) system. Since its discovery in the 1980s the domain of input signals shown to be applicable to SR has greatly expanded, from strictly periodic inputs to now nearly any aperiodic forcing function. The perturbations (noise) used to generate SR have also expanded, from white noise to now colored noise or vibrational forcing. This study demonstrates that a new class of perturbations can achieve SR, namely, series of stochastically generated biphasic pulse trains. Using these pulse trains as 'noise' we show that a Hodgkin Huxley model neuron exhibits SR behavior when detecting weak input signals. This result is of particular interest to neuroscience because nearly all artificial neural stimulation is implemented with square current or voltage pulses rather than broadband noise, and this new method may facilitate the translation of the performance gains achievable through SR to neural prosthetics. PMID:25186655

  12. Modulated pumping in Cs with picosecond pulse trains

    Two different experimental arrangements were used for periodic excitation detection of coherence. Cs vapor in a gas cell was resonantly excited on the D2 line by a train of ultrashort light pulses of circular polarization. To reduce transit-time broadening, additional buffer gas was contained in the cell and the light beam from a laser was expanded to a cross section of about 1.5 cm2. The resulting atomic coherence amplitude which was due to the periodic excitation of atoms could then be measured by different means. The experimental set-up is shown which takes advantage of the fact that atomic coherence gives rise to an oscillating optical anisotropy in the sample. The atomic splitting is measured by the 9th harmonic of the injection laser pulse rate with a width of less than 50 Hz. The experiments demonstrate the ultrahigh frequency resolution is possible with optical pulse train interference spectroscopy which allows one to sensitively detect small pressure shifts in the hyperfine frequency caused by buffer gases in the gas cell

  13. Photoemission electron microscopy using extreme ultraviolet attosecond pulse trains

    We report the first experiments carried out on a new imaging setup, which combines the high spatial resolution of a photoemission electron microscope (PEEM) with the temporal resolution of extreme ultraviolet (XUV) attosecond pulse trains. The very short pulses were provided by high-harmonic generation and used to illuminate lithographic structures and Au nanoparticles, which, in turn, were imaged with a PEEM resolving features below 300 nm. We argue that the spatial resolution is limited by the lack of electron energy filtering in this particular demonstration experiment. Problems with extensive space charge effects, which can occur due to the low probe pulse repetition rate and extremely short duration, are solved by reducing peak intensity while maintaining a sufficient average intensity to allow imaging. Finally, a powerful femtosecond infrared (IR) beam was combined with the XUV beam in a pump-probe setup where delays could be varied from subfemtoseconds to picoseconds. The IR pump beam could induce multiphoton electron emission in resonant features on the surface. The interaction between the electrons emitted by the pump and probe pulses could be observed.

  14. Photoemission electron microscopy using extreme ultraviolet attosecond pulse trains

    Mikkelsen, A.; Schwenke, J.; Fordell, T.; Luo, G.; Kluender, K.; Hilner, E.; Anttu, N.; Lundgren, E.; Mauritsson, J.; Andersen, J. N.; Xu, H. Q.; L' Huillier, A. [Department of Physics, Lund University, Box 118, 22100 Lund (Sweden); Zakharov, A. A. [MAX-lab, Lund University, Box 118, 22100 Lund (Sweden)

    2009-12-15

    We report the first experiments carried out on a new imaging setup, which combines the high spatial resolution of a photoemission electron microscope (PEEM) with the temporal resolution of extreme ultraviolet (XUV) attosecond pulse trains. The very short pulses were provided by high-harmonic generation and used to illuminate lithographic structures and Au nanoparticles, which, in turn, were imaged with a PEEM resolving features below 300 nm. We argue that the spatial resolution is limited by the lack of electron energy filtering in this particular demonstration experiment. Problems with extensive space charge effects, which can occur due to the low probe pulse repetition rate and extremely short duration, are solved by reducing peak intensity while maintaining a sufficient average intensity to allow imaging. Finally, a powerful femtosecond infrared (IR) beam was combined with the XUV beam in a pump-probe setup where delays could be varied from subfemtoseconds to picoseconds. The IR pump beam could induce multiphoton electron emission in resonant features on the surface. The interaction between the electrons emitted by the pump and probe pulses could be observed.

  15. Spectrum analysis of all parameter noises in repetition-rate laser pulse train

    Junhua Tang; Yuncai Wang

    2006-01-01

    @@ The theoretical investigation of all parameter noises in repetition-rate laser pulse train was presented. The expression of power spectrum of laser pulse trains with all parameter noises was derived, and the power spectra of pulse trains with different noise parameters were numerically simulated. By comparing the power spectra with and without pulse-width jitter, we noted that pulse-width jitter could not be neglected compared with amplitude noise and timing jitter and contributed a great amount of noise into the power spectrum under the condition that the product of pulse width and angular frequency was larger than 1.

  16. Frequency Stepped Pulse Train Modulated Wind Sensing Lidar

    Olesen, Anders Sig; Pedersen, Anders Tegtmeier; Rottwitt, Karsten

    2011-01-01

    In this paper a wind sensing lidar utilizing a Frequency Stepped Pulse Train (FSPT) is demonstrated. One of the advantages in the FSTP lidar is that it enables direct measurement of wind speed as a function of distance from the lidar. Theoretically the FSPT lidar continuously produces measurements as is the case with a CW lidar, but at the same time with a spatial resolution, and without the range ambiguity originating from e.g. clouds. The FSPT lidar utilizes a frequency sweeping source for ...

  17. Transporting Rydberg Electron Wave Packets with Chirped Trains of Pulses

    A protocol for steering Rydberg electrons towards targeted final states is realized with the aid of a chirped train of half-cycle pulses (HCPs). Its novel capabilities are demonstrated experimentally by transporting potassium atoms excited to the lowest-lying quasi-one-dimensional states in the ni=350 Stark manifold to a narrow range of much higher-n states. We demonstrate that this coherent state transfer is, to a high degree, reversible. The protocol allows for remarkable selectivity and is highly efficient, with typically over 80% of the parent atoms surviving the HCP sequence

  18. Single attosecond pulse generation in He+ by controlling the instant ionization rate using attosecond pulse trains combined with an intense laser pulse

    High-order harmonics and single attosecond pulse generation by using an infrared laser pulse combined with attosecond pulse trains (APT) interacting with He+ have been investigated. We show that the ionization for different instant time intervals can be controlled by altering the time delay between the APT and the infrared pulse. Consequently, APT can be used as a tool to control the efficiency of high-order harmonics emitted at different times. By choosing appropriate APT and time delay, the driving pulse width for single attosecond pulse generation can be extended up to six optical cycles

  19. Single attosecond pulse generation in He+ by controlling the instant ionization rate using attosecond pulse trains combined with an intense laser pulse

    He, Xinkui; Jia, T. Q.; Zhang, Jun; Suzuki, M.; Baba, M.; Ozaki, T.; Li, Ruxin; Xu, Zhizhan; Kuroda, Hiroto

    2007-08-01

    High-order harmonics and single attosecond pulse generation by using an infrared laser pulse combined with attosecond pulse trains (APT) interacting with He+ have been investigated. We show that the ionization for different instant time intervals can be controlled by altering the time delay between the APT and the infrared pulse. Consequently, APT can be used as a tool to control the efficiency of high-order harmonics emitted at different times. By choosing appropriate APT and time delay, the driving pulse width for single attosecond pulse generation can be extended up to six optical cycles.

  20. An experimental comparison of triggered and random pulse train uncertainties

    response) have used only one of the two analysis methods for the nuclear material assay. The aim of this study is to provide a systematic comparison of the precision of the measured S, D, T rates and 240Pu effective mass obtained using the above mentioned pulse train sampling techniques. In order to perform this task, a LANL developed list mode based data acquisition system is used, where the entire pulse train is recorded and subsequently analyzed. The list mode acquisition brings an essential advantage for this type of comparison, since the very same pulse train can be analyzed using signal-triggered as well as randomly triggered counting gates. The aim of this study is not only to compare the precision of signal-triggered versus random triggered sampling techniques, but also to investigate the influence of fast accidental sampling on the precision of signal-triggered results. In addition the different random sampling techniques used in safeguards are investigated. For this purpose we implement two types of random sampling - non-overlapping gates (Feynrnan approach) and periodic overlapping gates (fast accidentals). In the following sections the equations utilized in the pulse train analysis are described, experimental setup and measurement techniques are discussed and finally the results are summarized and discussed.

  1. Theory of attosecond pulse train control of strong field processes

    Full text: We present both single atom and macroscopic propagation calculations which demonstrate that attosec and pulse trains (APTs) are natural tools for controlling strong field processes driven by an infrared (IR) laser. This control originates in the short duration of the APTs and their periodicity, which is half the IR laser period. This allows us to fix the ionization to a particular point in each IR half cycle and to select which quantum paths are available for the ionized electron to follow. In this talk we will discuss the use of APTs to control and probe strong field processes such as above threshold ionization and harmonic generation. Solutions of the time-dependent Schroedinger equation (TDSE) for a helium atom subject to a combined APT/IR field show that both the yield and the coherence properties of the harmonics are improved when the APT is timed to launch the electron along the shortest quantum path, which exhibits a slow phase dependence and therefore gives rise to well behaved harmonics. Recently, we have carried out non-adiabatic phase matching calculations of helium atoms exposed to the combination of a strong IR laser pulse and an APT. We find that there are phase matching conditions where the single atom quantum path selection has a very large impact on the generated harmonics. Additionally, we find that for optimal delays between the APT and IR driving pulses the harmonic yield can be enhanced by two to four orders of magnitude over most of the harmonic spectrum. This is a much larger enhancement than that of the single atom response and is due both to a change in the IR intensity dependence of the harmonic strength and phase due to the presence of the APT, and to improved phase matching. Refs. 2 (author)

  2. Design and characterization of an RF pulse train generator for large-signal analysis

    In this paper an RF pulse train signal is introduced that can serve as a reference signal for the phase calibration of the large-signal network analyser (LSNA) under modulated excitations. Hence, the pulse train generator is specifically designed to fulfil the requirements of such a calibration signal. The design and characterization of the RF signal generator are discussed in this work

  3. Design and Characteristic Analysis of Multicarrier Chaotic Phase Coded Radar Pulse Train Signal

    Qiongdan Huang

    2014-01-01

    Full Text Available By introducing phase code into multicarrier orthogonal frequency division multiplex signal, the multicarrier phase coded (MCPC radar signal possesses a good spectrum utilization rate and can achieve a good combination of narrowband and wideband processing. Radar pulse train signal not only reserves the high range resolution of monopulse signal, but also has the same velocity resolution performance as continuous wave signal does. In this study, we use the chaotic biphase code generated by Chebyshev mapping to conduct a phase modulation on MCPC pulse train so as to design two different types of multicarrier chaotic phase coded pulse train signal. The ambiguity functions of the two pulse train signals are compared with that of P4 code MCPC pulse train. In addition, we analyze the influences of subcarrier number, phase-modulated bit number, and period number on the pulse train’s autocorrelation performance. The low probability of intercept (LPI performance of the two signals is also discussed. Simulation results show that the designed pulse train signals have a thumbtack ambiguity function, a periodic autocorrelation side lobe lower than P4 code MCPC pulse train, and excellent LPI performance, as well as the feature of waveform diversity.

  4. Control of high order harmonic emission using attosecond pulse trains

    Full text: We show that attosecond pulse trains (APTs) are a natural tool for controlling strong field processes such as high order harmonic generation. When used in combination with an intense infrared laser field, the timing of the APT with respect to the infrared (IR) laser field can be used to microscopically select a single quantum path contribution to a process that would otherwise consist of many interfering components. It is through this timing that we predict control over the release of the electron into the continuum, its excursion inside the continuum and consequently influence the yield and coherence properties of the harmonics. Since our initial calculation was based on the time-dependent Schroedinger equation, only single atom effects could be predicted. We have carried out an initial experiment in which we generate the APT from harmonic generation in a xenon fiber target, and focus the APT together with the remaining IR field with an Ag mirror into an He gas jet. The photon spectrum for a fixed time delay between APT and IR field is shown: a clear enhancement of the harmonic spectrum at the cutoff region is seen only when both the APT and the IR field are present. We have predicted control over quantum paths of electron wavepackets using a combination of APT and an IR field, manifesting in the harmonic photon spectrum as order-of-magnitude enhancement of the harmonic yield and spectral cleanup. First experimental results, for a fixed time delay, clearly confirm the enhancement and spectral control, whereas in a future experiment we plan to vary the time delay. Refs. 3 (author)

  5. Temporal Characterization of individual Harmonics of an attosecond pulse train by THz Streaking

    Ardana-Lamas, F; Stepanov, A; Gorgisyan, I; Juranic, P; Abela, R; Hauri, C P

    2015-01-01

    We report on the global temporal pulse characteristics of individual harmonics in an attosecond pulse train by means of photo-electron streaking in a strong low-frequency transient. The scheme allows direct retrieval of pulse durations and first order chirp of individual harmonics without the need of temporal scanning. The measurements were performed using an intense THz field generated by tilted phase front technique in LiNbO_3 . Pulse properties for harmonics of order 23, 25 and 27 show that the individual pulse durations and linear chirp are decreasing by the harmonic order.

  6. Interaction Of CO2 Laser Nanosecond Pulse Train With The Metallic Targets In Optical Breakdown Regime

    Apollonov, V. V.; Firsov, K. N.; Konov, V. I.; Nikitin, P. I.; Prokhorov, A. M.; Silenok, A. S.; Sorochenko, V. R.

    1986-11-01

    In the present paper the electric field and currents in the air-breakdown plasma, produced by the train of nanosecond pulses of TEA-002 - regenerative amplifier near the un-charged targets are studied. The breakdown thresholds and the efficiency of plasma-target heat transmission are also measured. The results of numerical calculations made for increasing of the pulse train contrast with respect to the background in a regenerative amplifier are advanced.

  7. Bioacoustical Periodic Pulse Train Signal Detection and Classification using Spectrogram Intensity Binarization and Energy Projection

    Marian POPESCU; Dugan, Peter J.; Pourhomayoun, Mohammad; Risch, Denise; Harold W. Lewis III; Clark, Christopher W.

    2013-01-01

    The following work outlines an approach for automatic detection and recognition of periodic pulse train signals using a multi-stage process based on spectrogram edge detection, energy projection and classification. The method has been implemented to automatically detect and recognize pulse train songs of minke whales. While the long term goal of this work is to properly identify and detect minke songs from large multi-year datasets, this effort was developed using sounds off the coast of Mass...

  8. High harmonic attosecond pulse train amplification in a free electron laser

    McNeil, B.W.; Sheehy, B.; Thompson, N.R.; Dunning, D.J.

    2011-03-04

    It is shown using three-dimensional simulations that the temporal structure of an attosecond pulse train, such as that generated via high harmonic generation in noble gases, may be retained in a free electron laser amplifier through to saturation using a mode-locked optical klystron configuration. At wavelengths of {approx}12 nm, a train of attosecond pulses of widths {approx}300 as with peak powers in excess of 1 GW are predicted.

  9. High harmonic attosecond pulse train amplification in a free electron laser

    It is shown using three-dimensional simulations that the temporal structure of an attosecond pulse train, such as that generated via high harmonic generation in noble gases, may be retained in a free electron laser amplifier through to saturation using a mode-locked optical klystron configuration. At wavelengths of ∼12 nm, a train of attosecond pulses of widths ∼300 as with peak powers in excess of 1 GW are predicted.

  10. Plasma production by a train of nanosecond CO2 laser pulses

    The first experimental study of the electric fields and currents which accompany the breakdown of air by a train of nanosecond CO2-laser pulses near the surface of an uncharged (copper) target is reported. Bombardment with a train of nanosecond laser pulses leads to a lowering of the threshold for plasma production, to an increase in the efficiency at which energy is transferred to the target, and to the excitation of high-frequency (1 GHz) electric fields and currents. 8 references

  11. A new coding concept for fast ultrasound imaging using pulse trains

    Misaridis, T.; Jensen, Jørgen Arendt

    paper, an alternative combined time-space coding approach is undertaken. In the new method all transducer elements are excited with short pulses and the high time-bandwidth (TB) product waveforms are generated acoustically. Each element transmits a short pulse spherical wave with a constant transmit...... delay from element to element, long enough to assure no pulse overlapping for all depths in the image. Frequency shift keying is used for "per element" coding. The received signals from a point scatterer are staggered pulse trains which are beamformed for all beam directions and further processed with a...... bank of matched filters (one for each beam direction). Filtering compresses the pulse train to a single pulse at the scatterer position with a number of spike axial sidelobes. Cancellation of the ambiguity spikes is done by applying additional phase modulation from one emission to the next and summing...

  12. Pulse-train nonuniformity in an all-fiber ring laser passively mode-locked by nonlinear polarization rotation

    Luo Zhi-Chao; Xu Wen-Cheng; Song Chuang-Xing; Luo Ai-Ping; Chen Wei-Cheng

    2009-01-01

    This paper reports the periodic power variation of the pulse-train in a passively mode-locked soliton fiber ring laser. It can obtain either the uniform or nonuniform pulse-train output by simply rotating the polarization controllers.The experimental results show that the pulse-train nonuniformity is caused by the interaction between the nonuniform polarization states of the soliton pulses and the passive polarizer in the cavity.

  13. Time-resolved reconstruction of dynamical pulse trains using multiheterodyne detection

    Butler, T.; Tykalewicz, B.; Goulding, D.; Kelleher, B.; Huyet, Guillaume; Hegarty, S. P.

    2014-05-01

    A technique has been developed for the measurement of pulse trains demonstrating a dynamical behaviour (i.e. not ideally periodic). Existing techniques in this area (e.g. FROG, SPIDER or other heterodyne methods) require very stable pulse trains, or large averaging times, and so are limited when applied to even slowly varying pulse trains. The technique presented involves mixing the comb under test (CUT) with a reference optical frequency comb (OFC) which has a known spectral intensity profile. Mixing these signals on a photodiode results in a series of radio frequency (RF) beat tones. The phase properties of these beat tones can be used to measure the spectral phase between adjacent modes in the CUT, allowing the full complex spectrum of the CUT to be measured simultaneously with one single real time oscilloscope acquisition. With the spectral properties of the comb known, the pulse train can be reconstructed in the temporal domain. By applying this technique to very small sections of the beating signal ( tens of nanoseconds), a time resolved picture of the pulse train behaviour can be obtained. Dynamic signals generated in a LiNbO3 modulator driven by a modulated RF signal have been measured. This technique is well suited to studying the combs produced by mode-locked semiconductor lasers. Quantum dot mode-locked laser combs can be characterised, and pulse train instabilities measured.

  14. Analog-to-digital conversion with a SQUID: Conditions for a countable pulse train

    A superconducting loop containing a Josephson junction develops voltage pulses when it admits and expels magnetic flux quanta, and thus may be used as an A/D converter. We here develop and discuss several conditions which must be satisfied for the generation by the SQUID of an unambiguously countable pulse train, from which the analog signal can be faithfully reconstructed. These conditions can be satisfied over a broad range of realizable values of inductance and resistance. The capacitance, however, must be carefully controlled. The results of simulations are also presented, illustrating the various ways in which the pulse trains are affected

  15. Fast simulation and optimization of pulse-train chemical exchange saturation transfer (CEST) imaging

    Chemical exchange saturation transfer (CEST) MRI has been increasingly applied to detect dilute solutes and physicochemical properties, with promising in vivo applications. Whereas CEST imaging has been implemented with continuous wave (CW) radio-frequency irradiation on preclinical scanners, pulse-train irradiation is often chosen on clinical systems. Therefore, it is necessary to optimize pulse-train CEST imaging, particularly important for translational studies. Because conventional Bloch–McConnell formulas are not in the form of homogeneous differential equations, the routine simulation approach simulates the evolving magnetization step by step, which is time consuming. Herein we developed a computationally efficient numerical solution using matrix iterative analysis of homogeneous Bloch–McConnell equations. The proposed algorithm requires simulation of pulse-train CEST MRI magnetization within one irradiation repeat, with 99% computation time reduction from that of conventional approach under typical experimental conditions. The proposed solution enables determination of labile proton ratio and exchange rate from pulse-train CEST MRI experiment, within 5% from those determined from quantitative CW-CEST MRI. In addition, the structural similarity index analysis shows that the dependence of CEST contrast on saturation pulse flip angle and duration between simulation and experiment was 0.98  ±  0.01, indicating that the proposed simulation algorithm permits fast optimization and quantification of pulse-train CEST MRI. (paper)

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

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

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

    Zhong Xian-Qiong; Xiang An-Ping

    2009-01-01

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

  18. Extraction of pulse repetition intervals from sperm whale click trains for ocean acoustic data mining.

    Zaugg, Serge; van der Schaar, Mike; Houégnigan, Ludwig; André, Michel

    2013-02-01

    The analysis of acoustic data from the ocean is a valuable tool to study free ranging cetaceans and anthropogenic noise. Due to the typically large volume of acquired data, there is a demand for automated analysis techniques. Many cetaceans produce acoustic pulses (echolocation clicks) with a pulse repetition interval (PRI) remaining nearly constant over several pulses. Analyzing these pulse trains is challenging because they are often interleaved. This article presents an algorithm that estimates a pulse's PRI with respect to neighboring pulses. It includes a deinterleaving step that operates via a spectral dissimilarity metric. The sperm whale (SW) produces trains with PRIs between 0.5 and 2 s. As a validation, the algorithm was used for the PRI-based identification of SW click trains with data from the NEMO-ONDE observatory that contained other pulsed sounds, mainly from ship propellers. Separation of files containing SW clicks with a medium and high signal to noise ratio from files containing other pulsed sounds gave an area under the receiver operating characteristic curve value of 0.96. This study demonstrates that PRI can be used for the automated identification of SW clicks and that deinterleaving via spectral dissimilarity contributes to algorithm performance. PMID:23363108

  19. Generation of High-Repetition-Rate Pulse Trains through the Continuous-Wave Perturbed by a Weak Gaussian Pulse in an Optical Fiber

    A new means of generating all-optically high-repetition-rate pulse trains is proposed and numerically demonstrated in an optical fiber. Our numerical simulations show that, due to the modulation instability effect, the initial continuous-wave with a weak optical pulse instead of conventional weak sinusoidal modulation imposed on it can gradually evolve into high-repetition-rate pulse trains. However, the generated pulse trains take on different features from the conventional case in terms of their widths, intensities, intervals, numbers, and pedestals. (fundamental areas of phenomenology(including applications))

  20. Performance investigation of the pulse and Campbelling modes of a fission chamber using a Poisson pulse train simulation code

    The detectors of the neutron flux monitoring system of the foreseen French GEN-IV sodium-cooled fast reactor (SFR) will be high temperature fission chambers placed in the reactor vessel in the vicinity of the core. The operation of a fission chamber over a wide-range neutron flux will be feasible provided that the overlap of the applicability of its pulse and Campbelling operational modes is ensured. This paper addresses the question of the linearity of these two modes and it also presents our recent efforts to develop a specific code for the simulation of fission chamber pulse trains. Our developed simulation code is described and its overall verification is shown. An extensive quantitative investigation was performed to explore the applicability limits of these two standard modes. It was found that for short pulses the overlap between the pulse and Campbelling modes can be guaranteed if the standard deviation of the background noise is not higher than 5% of the pulse amplitude. It was also shown that the Campbelling mode is sensitive to parasitic noise, while the performance of the pulse mode is affected by the stochastic amplitude distributions

  1. Performance investigation of the pulse and Campbelling modes of a fission chamber using a Poisson pulse train simulation code

    Elter, Zs. [CEA, DEN, DER, Instrumentation, Sensors and Dosimetry Laboratory, Cadarache, F-13108 Saint-Paul-lez-Durance (France); Chalmers University of Technology, Department of Applied Physics, Division of Nuclear Engineering, SE-412 96 Göteborg (Sweden); Jammes, C., E-mail: christian.jammes@cea.fr [CEA, DEN, DER, Instrumentation, Sensors and Dosimetry Laboratory, Cadarache, F-13108 Saint-Paul-lez-Durance (France); Pázsit, I. [Chalmers University of Technology, Department of Applied Physics, Division of Nuclear Engineering, SE-412 96 Göteborg (Sweden); Pál, L. [Centre for Energy Research, Hungarian Academy of Sciences, H-1525 Budapest 114, POB 49 (Hungary); Filliatre, P. [CEA, DEN, DER, Instrumentation, Sensors and Dosimetry Laboratory, Cadarache, F-13108 Saint-Paul-lez-Durance (France)

    2015-02-21

    The detectors of the neutron flux monitoring system of the foreseen French GEN-IV sodium-cooled fast reactor (SFR) will be high temperature fission chambers placed in the reactor vessel in the vicinity of the core. The operation of a fission chamber over a wide-range neutron flux will be feasible provided that the overlap of the applicability of its pulse and Campbelling operational modes is ensured. This paper addresses the question of the linearity of these two modes and it also presents our recent efforts to develop a specific code for the simulation of fission chamber pulse trains. Our developed simulation code is described and its overall verification is shown. An extensive quantitative investigation was performed to explore the applicability limits of these two standard modes. It was found that for short pulses the overlap between the pulse and Campbelling modes can be guaranteed if the standard deviation of the background noise is not higher than 5% of the pulse amplitude. It was also shown that the Campbelling mode is sensitive to parasitic noise, while the performance of the pulse mode is affected by the stochastic amplitude distributions.

  2. Performance investigation of the pulse and Campbelling modes of a fission chamber using a Poisson pulse train simulation code

    Elter, Zs.; Jammes, C.; Pázsit, I.; Pál, L.; Filliatre, P.

    2015-02-01

    The detectors of the neutron flux monitoring system of the foreseen French GEN-IV sodium-cooled fast reactor (SFR) will be high temperature fission chambers placed in the reactor vessel in the vicinity of the core. The operation of a fission chamber over a wide-range neutron flux will be feasible provided that the overlap of the applicability of its pulse and Campbelling operational modes is ensured. This paper addresses the question of the linearity of these two modes and it also presents our recent efforts to develop a specific code for the simulation of fission chamber pulse trains. Our developed simulation code is described and its overall verification is shown. An extensive quantitative investigation was performed to explore the applicability limits of these two standard modes. It was found that for short pulses the overlap between the pulse and Campbelling modes can be guaranteed if the standard deviation of the background noise is not higher than 5% of the pulse amplitude. It was also shown that the Campbelling mode is sensitive to parasitic noise, while the performance of the pulse mode is affected by the stochastic amplitude distributions.

  3. Burst train generator of high energy femtosecond laser pulses for driving heat accumulation effect during micromachining.

    Rezaei, Saeid; Li, Jianzhao; Herman, Peter R

    2015-05-01

    A new method for generating high-repetition-rate (12.7-38.2 MHz) burst trains of femtosecond laser pulses has been demonstrated for the purpose of tailoring ultrashort laser interactions in material processing that can harness the heat accumulation effect among pulses separated by a short interval (i.e., 26 ns). Computer-controlled time delays were applied to synchronously trigger the high frequency switching of a high voltage Pockels cell to specify distinctive values of polarization rotation for each round-trip of a laser pulse cycling within a passive resonator. Polarization dependent output coupling facilitated the flexible shaping of the burst envelope profile to provide burst trains of up to ∼1  mJ of burst energy divided over a selectable number (1 to 25) of pulses. Individual pulses of variable energy up to 150 μJ and with pulse duration tunable over 70 fs to 2 ps, were applied in burst trains to generate deep and high aspect ratio holes that could not form with low-repetition-rate laser pulses. PMID:25927785

  4. A new technique of measuring low-power picosecond optical pulse trains

    Shcherbakov, Alexandre S.; Munoz Zurita, A. L.; Campos Acosta, Joaquin

    2007-06-01

    We present a theoretic approach to the characterization of low-power bright ultrashort optical pulses with an internal frequency modulation simultaneously in both time and frequency domains. This approach exploits the Wigner time-frequency distribution, which can be determined and developed for these bright optical pulses by using a novel interferometric technique under our proposal. At first, the analysis and computer simulations are applied to studying the capability of Wigner distribution to characterize solitary pulses in practically important case of the sech-pulses. Then, the simplest two-beam scanning Michelson interferometer is selected for shaping the field-strength auto-correlation function of low-power picosecond pulse trains. We are proposing the key features of a new interferometric experimental technique for accurate and reliable measurements of the train-average width as well as the value and sign of the frequency chirp of pulses in high-repetition-rate trains. This technique is founded on an ingenious algorithm for the advanced metrology, assumes using a specially designed supplementary semiconductor cell, and suggests carrying out a pair of additional measures with exploiting this semiconductor cell. The procedure makes it possible to construct the Wigner distribution and to describe the time-frequency parameters of low-power bright picosecond optical pulses.

  5. Simulations of drastically reduced SBS with laser pulses composed of a Spike Train of Uneven Duration and Delay (STUD pulses)

    Hüller, Stefan

    2012-01-01

    By comparing the impact of established laser smoothing techniques like Random Phase Plates (RPP) and Smoothing by Spectral Dispersion (SSD) to the concept of "Spike Trains of Uneven Duration and Delay" (STUD pulses) on the amplification of parametric instabilities in laser-produced plasmas, we show with the help of numerical simulations, that STUD pulses can drastically reduce instability growth by orders of magnitude. The simulation results, obtained with the code {\\sc Harmony} in a nonuniformly flowing mm-size plasma for the Stimulated Brillouin Scattering (SBS) instability, show that the efficiency of the STUD pulse technique is due to the fact that successive re-amplification in space and time of parametrically excited plasma waves inside laser hot spots is minimized. An overall mean fluctuation level of ion acoustic waves at low amplitude is established because of the frequent change of the speckle pattern in successive spikes. This level stays orders of magnitude below the levels of ion acoustic waves e...

  6. Frequency modulated few-cycle optical pulse trains induced controllable ultrafast coherent population oscillations in three-level atomic systems

    Kumar, Parvendra; Sarma, Amarendra K.

    2012-01-01

    We report a study on the ultrafast coherent population oscillations (UCPO) in two level atoms induced by the frequency modulated few-cycle optical pulse train. The phenomenon of UCPO is investigated by numerically solving the optical Bloch equations beyond the rotating wave approximation. We demonstrate that the quantum state of the atoms and the frequency of UCPO may be controlled by controlling the number of pulses in the pulse trains and the pulse repetition time respectively. Moreover, th...

  7. Temperature and thermal stress fields during the pulse train of long-pulse laser irradiating aluminium alloy plate

    Zhang, Wei; Jin, Guangyong; Gu, Xiu-ying

    2014-12-01

    Based on Von Mises yield criterion and elasto-plastic constitutive equations, an axisymmetric finite element model of a Gaussian laser beam irradiating a metal substrate was established. In the model of finite element, the finite difference hybrid algorithm is used to solve the problem of transient temperature field and stress field. Taking nonlinear thermal and mechanical properties into account, transient distributions of temperature field and stress fields generated by the pulse train of long-pulse laser in a piece of aluminium alloy plate were computed by the model. Moreover,distributions as well as histories of temperature and stress fields were obtained. Finite element analysis software COMSOL is used to simulate the Temperature and thermal stress fields during the pulse train of long-pulse laser irradiating 7A04 aluminium alloy plate. By the analysis of the results, it is found that Mises equivalent stress on the target surface distribute within the scope of the center of a certain radius. However, the stress is becoming smaller where far away from the center. Futhermore, the Mises equivalent stress almost does not effect on stress damage while the Mises equivalent stress is far less than the yield strength of aluminum alloy targets. Because of the good thermal conductivity of 7A04 aluminum alloy, thermal diffusion is extremely quick after laser irradiate. As a result, for the multi-pulsed laser, 7A04 aluminum alloy will not produce obvious temperature accumulation when the laser frequency is less than or equal to 10 Hz. The result of this paper provides theoretical foundation not only for research of theories of 7A04 aluminium alloy and its numerical simulation under laser radiation but also for long-pulse laser technology and widening its application scope.

  8. Broadband excitation in solid-state NMR using interleaved DANTE pulse trains with N pulses per rotor period

    Lu, Xingyu; Trébosc, Julien; Lafon, Olivier; Carnevale, Diego; Ulzega, Simone; Bodenhausen, Geoffrey; Amoureux, Jean-Paul

    2013-11-01

    We analyze the direct excitation of wide one-dimensional spectra of nuclei with spin I = 1/2 or 1 in rotating solids submitted to pulse trains in the manner of Delays Alternating with Nutations for Tailored Excitation (DANTE), either with one short rotor-synchronized pulse of duration τp in each of K rotor periods (D1K) or with N interleaved equally spaced pulses τp in each rotor period, globally also extending over K rotor periods (DNK). The excitation profile of DNK scheme is a comb of rf-spikelets with NνR = N/TR spacing from the carrier frequency, and a width of each spikelet inversely proportional to the length, KTR, of DNK scheme. Since the individual pulse lengths, τp, are typically of a few hundreds of ns, DNK scheme can readily excite spinning sidebands families covering several MHz, provided the rf carrier frequency is close enough to the resonance frequency of one the spinning sidebands. If the difference of isotropic chemical shifts between distinct chemical sites is less than about 1.35/(KTR), DNK scheme can excite the spinning sidebands families of several sites. For nuclei with I = 1/2, if the homogeneous and inhomogeneous decays of coherences during the DANTE sequence are neglected, the K pulses of a D1K train have a linearly cumulative effect, so that the total nutation angle is θtot = K2πν1τp, where ν1 is the rf-field amplitude. This allows obtaining nearly ideal 90° pulses for excitation or 180° rotations for inversion and refocusing across wide MAS spectra comprising many spinning sidebands. If one uses interleaved DANTE trains DNK with N > 1, only spinning sidebands separated by intervals of NνR with respect to the carrier frequency are observed as if the effective spinning speed was NνR. The other sidebands have vanishing intensities because of the cancellation of the N contributions with opposite signs. However, the intensities of the remaining sidebands obey the same rules as in spectra obtained with νR. With increasing N, the

  9. Noise characterization of a pulse train generated by actively mode-locked lasers

    Eliyahu, Danny; Salvatore, Randal A.; Yariv, Amnon

    1996-01-01

    We analyze the entire power spectrum of pulse trains generated by a continuously operating actively mode-locked laser in the presence of noise. We consider the effect of amplitude, pulse-shape, and timing-jitter fluctuations that are characterized by stationary processes. Effects of correlations between different parameters of these fluctuations are studied also. The nonstationary timing-jitter fluctuations of passively mode-locked lasers and their influence on the power spectrum is discussed...

  10. Analysis of shot noise in the detection of ultrashort optical pulse trains

    Quinlan, Franklyn; Fortier, Tara M.; Jiang, Haifeng; Diddams, Scott A.

    2013-01-01

    We present a frequency domain model of shot noise in the photodetection of ultrashort optical pulse trains using a time-varying analysis. Shot noise-limited photocurrent power spectral densities, signal-to-noise expressions, and shot noise spectral correlations are derived that explicitly include the finite response of the photodetector. It is shown that the strength of the spectral correlations in the shot noise depends on the optical pulse width, and that these correlations can create order...

  11. Cooperative emission of a pulse train in an optically thick scattering medium

    Kwong, C C; Delande, D; Pierrat, R; Wilkowski, D

    2015-01-01

    An optically thick cold atomic cloud emits a coherent flash of light in the forward direction when the phase of an incident probe field is abruptly changed. Due to cooperativity, the duration of this phenomena can be much shorter than the excited lifetime of a single atom and, surprisingly, it weakly depends on the temperature of the gas and on the probe frequency. Repeating periodically the abrupt change of the incident field phase, we generate a forward transmitted train of pulses with short repetition time. It is even possible to quench single atom fluorescence, transferring almost completely the incident power into the pulse train with a high intensity contrast.

  12. Educating the Educator: Use of Pulse Oximetry in Athletic Training

    Berry, David C.; Seitz, S. Robert

    2012-01-01

    The 5th edition of the "Athletic Training Education Competencies" expanded the scope of knowledge and skill set of entry-level athletic trainers related to the domain of "Acute Care of Injuries and Illnesses." One of these major changes includes the introduction of adjunct airway techniques, such as oropharyngeal and nasopharyngeal airways and…

  13. Observation and analysis of an interferometric autocorrelation trace of an attosecond pulse train

    We report the direct observation of phase locking between adjacent pulses in an attosecond pulse train (APT) via interferometric autocorrelation (IAC). In this measurement, the Coulomb explosion of N2 caused by two-photon absorption is utilized as correlated signals between two replicas of the APT that are the outcome of the spatial division of the APT in the interferometer. The analysis of IAC by the spatial division of the APT is consistent with the experimental trace of the IAC, and yields the duration of the pulse in the APT of 320 attoseconds, which corresponds to a 1.3 cycle period of the carrier frequency of the harmonic field

  14. Coherent hard x rays from attosecond pulse train-assisted harmonic generation.

    Klaiber, Michael; Hatsagortsyan, Karen Z; Müller, Carsten; Keitel, Christoph H

    2008-02-15

    High-order harmonic generation from atomic systems is considered in the crossed fields of a relativistically strong infrared laser and a weak attosecond pulse train of soft x rays. Due to one-photon ionization by the x-ray pulse, the ionized electron obtains a starting momentum that compensates the relativistic drift, which is induced by the laser magnetic field, and allows the electron to efficiently emit harmonic radiation upon recombination with the atomic core in the relativistic regime. This way, short pulses of coherent hard x rays of up to 40 keV energy can be generated. PMID:18278127

  15. Complex Spectra Structure of an Attosecond Pulse Train Driven by Sub-5-fs Laser Pulses

    YUN Chen-Xia; TENG Hao; ZHANG Wei; WANG Li-Feng; ZHAN Min-Jie; HE Xin-Kui; WANG Bing-Bing; WEI Zhi-Yi

    2011-01-01

    We present the observation of the additional spectral components between the odd order harmonics in the harmonic spectrum generated from argon gas driven by sub-5-fs laser pulses.The theoretical analysis shows that the asymmetric laser field in both spatial and temporal domains leads to this complicated spectrum structure of high order harmonics.

  16. Observation of Electromagnetically Induced Transparency by a Train of Short Pulses

    YE Cun-Yun

    2004-01-01

    @@ We report the experimental demonstration of electromagnetically induced transparency in hot rubidium (85 Rb)atomic vapour by using an actively mode-locked external cavity diode laser in Littman-Metcalf configuration.We can make opaque resonant transitions transparent to any two optical comb components in the pulse trains which excite atomic coherence in the ground states of 85Rb.

  17. Cognitive-Behavioral Therapy versus Temporal Pulse Amplitude Biofeedback Training for Recurrent Headache

    Martin, Paul R.; Forsyth, Michael R.; Reece, John

    2007-01-01

    Sixty-four headache sufferers were allocated randomly to cognitive-behavioral therapy (CBT), temporal pulse amplitude (TPA) biofeedback training, or waiting-list control. Fifty-one participants (14M/37F) completed the study, 30 with migraine and 21 with tension-type headache. Treatment consisted of 8, 1-hour sessions. CBT was highly effective,…

  18. Development of an X-ray microscope using a pulse train laser

    A pulse train laser with energy of 1 J was used to produce high intensity X-ray. We developed a soft X-ray microscope using a laser plasma X-ray source and an X-ray zooming tube. An X-ray image of Cu 2000 mesh was observed. (author)

  19. Precise manipulation on spike train of uneven duration or delay pulses with a time grating system.

    Li, Yue; Wang, Shiwei; Xu, Jianqiu; Tang, Yulong

    2015-11-16

    In this paper, we proposed a time grating system to achieve spike train of uneven duration or delay (STUD) pulses, and theoretically study their features under various modulation conditions. This time grating scheme, which is a temporal analogy of spatial grating, introduces great degree of freedom for controlling the output pulse characteristics (pulse width, repetition rate, pulse shape, etc.) through simply tuning the electronics elements and the programmable phase modulation function. The narrowest pulse width is highly determined by the modulation parameters and the branch number N, and the numerically obtained value is around tens of femtoseconds in the current case. When super-Gaussian pulses are modulated with an optimized and modified trapezoidal function, the pulse rising/falling edge can be greatly compressed to form a clean nearly-square wave (with edges less than 10 fs). STUD pulses generated with this time grating system have high-degree controllability and are very beneficial for suppressing parametric instabilities in laser driven inertial confinement fusion. PMID:26698432

  20. Controlled process for polymer micromachining using designed pulse trains of a UV solid state laser

    Ilie, Diana; Mullan, Claire; O'Connor, Gerard M.; Flaherty, Tony; Glynn, Thomas J.

    2007-12-01

    A flexible workstation equipped with a solid state laser operating at 266 nm wavelength was used to machine holes in polyethylene terephthalate, polyimide and polycarbonate. An optical pulse picker was employed to reduce the high repetition rates of the laser, while a breakthrough sensor was used to avoid over-drilling of through holes. For each material, different repetition rates and designed pulse trains were tested to improve feature quality and process efficiency. Although the three polymers had very different reactions at this wavelength they all showed an improvement in feature quality with decreasing repetition rate due to a reduction in thermal effects. Up to 10 kHz the average depth per pulse remained unchanged and afterwards a slight increase was observed but this was accompanied by large uncertainties. Bursts of pulses at 40 kHz inserted inside the low repetition rate pulse train reduced the drilling time and the amount of debris redeposited without affecting the feature quality. It was found that a number of cleaning pulses after perforation eliminates the heat affected zone around exits. Holes with entrance diameters below 20 μm and exit diameters as small as 2 μm were obtained with high repeatability.

  1. Phase Noise and Intensity Noise of the Pulse Train Generated from Mode-locked Lasers in the Demodulation Measurement

    Wu, Kan; Shum, Ping

    2010-01-01

    The phase noise and intensity noise of a pulse train are theoretically analyzed in the demodulation measurement. The effect of pulse asymmetry is discussed for the first time using Fourier series. Experimentally, photodetectors with different bandwidth and incident power levels are compared to achieve minimum pulse distortion.

  2. A new coding concept for fast ultrasound imaging using pulse trains

    Misaridis, T.; Jensen, Jørgen Arendt

    2002-01-01

    paper, an alternative combined time-space coding approach is undertaken. In the new method all transducer elements are excited with short pulses and the high time-bandwidth (TB) product waveforms are generated acoustically. Each element transmits a short pulse spherical wave with a constant transmit...... delay from element to element, long enough to assure no pulse overlapping for all depths in the image. Frequency shift keying is used for "per element" coding. The received signals from a point scatterer are staggered pulse trains which are beamformed for all beam directions and further processed with a......Frame rate in ultrasound imaging can he increased by simultaneous transmission of multiple beams using coded waveforms. However, the achievable degree of orthogonality among coded waveforms is limited in ultrasound, and the image quality degrades unacceptably due to interbeam interference. In this...

  3. Wave fronts, pulses and wave trains in photoexcited superlattices behaving as excitable or oscillatory media

    Undoped and strongly photoexcited semiconductor superlattices with field-dependent recombination behave as excitable or oscillatory media with spatially discrete nonlinear convection and diffusion. Infinitely long, dc-current-biased superlattices behaving as excitable media exhibit wave fronts with increasing or decreasing profiles, whose velocities can be calculated by means of asymptotic methods. These superlattices can also support pulses of the electric field. Pulses moving downstream with the flux of electrons can be constructed from their component wave fronts, whereas pulses advancing upstream do so slowly and experience saltatory motion: they change slowly in long intervals of time separated by fast transitions during which the pulses jump to the previous superlattice period. Photoexcited superlattices can also behave as oscillatory media and exhibit wave trains. (paper)

  4. Temporal characterization of individual harmonics of an attosecond pulse train by THz streaking

    Ardana-Lamas, F.; Erny, C.; Stepanov, A. G.; Gorgisyan, I.; Juranić, P.; Abela, R.; Hauri, C. P.

    2016-04-01

    We report on the temporal pulse characteristics of individual harmonics in an attosecond pulse train by means of photoelectron streaking in a strong low-frequency transient. The scheme allows one to retrieve the pulse durations and first-order chirp of individual harmonics without the need for temporal scanning. The measurements were performed using an intense THz field generated by a tilted phase front technique in LiNbO3. We compared the performance of Xe clusters and atomic He as a detection medium and retrieved the temporal properties for harmonics of order 19, 21, 23, 25, and 27. Our measurements confirm that the individual pulse durations and linear chirp decrease by harmonic order.

  5. Simulations of drastically reduced SBS with laser pulses composed of a Spike Train of Uneven Duration and Delay (STUD pulses)

    By comparing the impact of established laser smoothing techniques like Random Phase Plates (RPP) and Smoothing by Spectral Dispersion (SSD) to the concept of 'Spike Trains of Uneven Duration and Delay' (STUD pulses) on the amplification of parametric instabilities in laser-produced plasmas, we show with the help of numerical simulations, that STUD pulses can drastically reduce instability growth by orders of magnitude. The simulation results, obtained with the code Harmony in a nonuniformly flowing mm-size plasma for the Stimulated Brillouin Scattering (SBS) instability, show that the efficiency of the STUD pulse technique is due to the fact that successive re-amplification in space and time of parametrically excited plasma waves inside laser hot spots is minimized. An overall mean fluctuation level of ion acoustic waves at low amplitude is established because of the frequent change of the speckle pattern in successive spikes. This level stays orders of magnitude below the levels of ion acoustic waves excited in hot spots of RPP and SSD laser beams. (authors)

  6. Simulations of drastically reduced SBS with laser pulses composed of a Spike Train of Uneven Duration and Delay (STUD pulses

    Hüller Stefan

    2013-11-01

    Full Text Available By comparing the impact of established laser smoothing techniques like Random Phase Plates (RPP and Smoothing by Spectral Dispersion (SSD to the concept of “Spike Trains of Uneven Duration and Delay” (STUD pulses on the amplification of parametric instabilities in laser-produced plasmas, we show with the help of numerical simulations, that STUD pulses can drastically reduce instability growth by orders of magnitude. The simulation results, obtained with the code Harmony in a nonuniformly flowing mm-size plasma for the Stimulated Brillouin Scattering (SBS instability, show that the efficiency of the STUD pulse technique is due to the fact that successive re-amplification in space and time of parametrically excited plasma waves inside laser hot spots is minimized. An overall mean fluctuation level of ion acoustic waves at low amplitude is established because of the frequent change of the speckle pattern in successive spikes. This level stays orders of magnitude below the levels of ion acoustic waves excited in hot spots of RPP and SSD laser beams.

  7. Simulations of drastically reduced SBS with laser pulses composed of a Spike Train of Uneven Duration and Delay (STUD pulses)

    Hüller, Stefan; Afeyan, Bedros

    2013-11-01

    By comparing the impact of established laser smoothing techniques like Random Phase Plates (RPP) and Smoothing by Spectral Dispersion (SSD) to the concept of "Spike Trains of Uneven Duration and Delay" (STUD pulses) on the amplification of parametric instabilities in laser-produced plasmas, we show with the help of numerical simulations, that STUD pulses can drastically reduce instability growth by orders of magnitude. The simulation results, obtained with the code Harmony in a nonuniformly flowing mm-size plasma for the Stimulated Brillouin Scattering (SBS) instability, show that the efficiency of the STUD pulse technique is due to the fact that successive re-amplification in space and time of parametrically excited plasma waves inside laser hot spots is minimized. An overall mean fluctuation level of ion acoustic waves at low amplitude is established because of the frequent change of the speckle pattern in successive spikes. This level stays orders of magnitude below the levels of ion acoustic waves excited in hot spots of RPP and SSD laser beams.

  8. A Search for Dying Pulse Trains in Cyg X-1 using RXTE

    Dolan, Joseph F

    2011-01-01

    Dying pulse trains (DPTs) pulses of radiation with decreasing intensity and decreasing intervals between them are predicted by General Relativity to occur from material spiraling into an event horizon after detaching from the last stable orbit in an accretion disk around a black hole. Two events resembling DPTs were detected in 3 hours observation of Cyg X-1 in the far UV using the High Speed Photometer on the Hubble Space Telescope (Dolan 2001). We observed Cyg X-1, a leading candidate for a black hole, with the proportional counter array on RXTE to seek such events in the low-energy X-ray region. No dying pulse trains with a characteristic timescale between pulses of 1 - 40 ms were detected in 10 hours of observation during Cyg X-1s high luminosity state, low luminosity state, and transitions between states, although individual pulses are clearly detectable in data with 1 ms temporal resolution. The 2 sigma upper limit on the rate of DPTs in the X-ray region is less than half the rate reported by Dolan (200...

  9. Studies to assess the effect of pet training aids, specifically remote static pulse systems, on the welfare of domestic dogs: field study of dogs in training

    Cooper, Jonathan; Cracknell, Nina; Hardiman, Jessica; Mills, Daniel

    2013-01-01

    The project had a single aim, namely to assess the impact of use of remote static pulse electric training aids (e-collars) during the training of dogs in comparison to dogs referred for similar behavioural problems but without e-collar training. The specific objective was to use appropriate behavioural and physiological measures to make inferences about the welfare of subjects including their aversion and anxiety during and following training. A secondary objective was to evaluate the efficac...

  10. Coherent hard x-rays from attosecond pulse train-assisted harmonic generation

    Klaiber, Michael; Hatsagortsyan, Karen Z.; Müller, Carsten; Christoph H. Keitel

    2007-01-01

    High-order harmonic generation from atomic systems is considered in the crossed fields of a relativistically strong infrared laser and a weak attosecond-pulse train of soft x-rays. Due to one-photon ionization by the x-ray pulse, the ionized electron obtains a starting momentum that compensates the relativistic drift which is induced by the laser magnetic field, and allows the electron to efficiently emit harmonic radiation upon recombination with the atomic core in the relativistic regime. I...

  11. First observation of multi-pulse X-ray train via multi-collision laser Compton scattering

    A compact hard X-ray source via laser Compton scattering (LCS) has been developed for biological and medical applications at the National Institute of Advanced Industrial Science and Technology (AIST) in Japan. The multi-collision LCS has been investigated in order to enhance the X-ray yields. The first observation of multi-pulse X-ray train with 6 pulses via the multi-collision LCS has been successfully demonstrated between the multi-bunch electron train with 6 bunches and the multi-pulse Ti:Sa laser train with 6 pulses. The 32 MeV electron train was generated from a Cs2Te photocathode rf gun with a multi-pulse UV laser and the S-band linac. The Ti:Sa laser train was obtained with the chirp pulse amplification (CPA) including the modified regenerative amplifier. The X-ray train with 6 pulses with 12.6 ns spacing was observed with the micro-channel plate (MCP). The maximum energy of the X-ray is analytically estimated to be about 24 keV and the total number of generated photons was calculated to be about 1.8x106 photons/train.

  12. UV pulse trains by α-BBO crystal stacking for the production of THz-rap-rate electron bunches

    Yan, Li-Xin; Hua, Jian-Fei; Du, Ying-Chao; Huang, Yuan-Fang; You, Yan; Wang, Dan; Huang, Wen-Hui; Tang, Chuan-Xiang; Tang

    2012-08-01

    Ultrashort electron bunch trains can be used for plasma wake field acceleration (PWFA) to overcome the limit of transformer ratio of a single electron bunch, or high-power terahertz (Thz) radiation production by various radiation mechanisms. Basic facility for high-power THz radiation development based on ultrashort electron beam has been set up at accelerator lab of TUB. Using birefringent crystal serials, ultraviolet (UV) pulse shaping for photocathode radio frequency gun to produce THz-repetition-rate pulse train was realized. Driven by such pulses, ultrashort electron bunch train with picosecond (ps) spacing was obtained for THz production. Measurement of the stacked UV pulse trains was done by difference frequency generation (DFG), and the measured group velocity mismatch of α-BBO crystal at 266.7-nm wavelength was 0.8 ps/mm. This method may also be applied to form ramped electron bunch trains for PWFA.

  13. Effect of two-channel gastric electrical stimulation with trains of pulses on gastric motility

    Bin Yang; Xiao-Hua Hou; Geng-Qing Song; Jin-Song Liu; Jiande DZ Chen

    2009-01-01

    AIM: To investigate the effect of two-channel gastric electrical stimulation (GES) with trains of pulses on gastric emptying and slow waves. METHODS: Seven dogs implanted with four pairs of electrodes and equipped with a duodenal cannula were involved in this study. Two experiments were performed. The first experiment included a series of sessions in the fasting state with trains of short or long pulses, each lasted 10 min. A 5-min recording without pacing was made between two sessions. The second experiment was performed in three sessions (control, single-channel GES, and two-channel GES). The stimulus was applied via the 1st pair of electrodes for single-channel GES (GES via one pair of electrodes located at 14 cm above the pylorus), and simultaneously via the 1st and 3rd channels for two-channel GES (GES via two pairs of electrodes located at 6 and 14 cm above the pylorus). Gastric liquid emptying was collected every 15 min via the cannula for 90 min. RESULTS: GES with trains of pulses at a pulse width of 4 ms or higher was able to entrain gastric slow waves. Two-channel GES was about 50% more efficient than single-channel GES in entraining gastric slow waves. Two channel but not single-channel GES with trains of pulses was capable of accelerating gastric emptying in healthy dogs. Compared with the control session, two-channel GES significantly increased gastric emptying of liquids at 15 min (79.0% ± 6.4% vs 61.3% ± 6.1%, P < 0.01), 30 min (83.2% ± 6.3 % vs 68.2% ± 6.9%, P < 0.01),60 min (86.9% ± 5.5 % vs 74.1% ± 5.9%, P < 0.01),and 90 min (91.0% ± 3.4% vs 76.5% ± 5.9%, P < 0.01).CONCLUSION: Two-channel GES with trains of pulses accelerates gastric emptying in healthy dogs and may have a therapeutic potential for the treatment of gastric motility disorders.

  14. Effects of High-Rate Pulse Trains on Electrode Discrimination in Cochlear Implant Users

    Runge-Samuelson, Christina L.

    2009-01-01

    Overcoming issues related to abnormally high neural synchrony in response to electrical stimulation is one aspect in improving hearing with a cochlear implant. Desynchronization of electrical stimuli have shown benefits in neural encoding of electrical signals and improvements in psychophysical tasks. In the present study, 10 participants with either CII or HiRes 90k Advanced Bionics devices were tested for the effects of desynchronizing constant-amplitude high-rate (5,000 Hz) pulse trains on...

  15. Gate-controlled generation of optical pulse trains using individual carbon nanotubes

    Jiang, M; Kumamoto, Y.; Ishii, A; Yoshida, M.; Shimada, T; Kato, Y. K.

    2014-01-01

    In single-walled carbon nanotubes, electron–hole pairs form tightly bound excitons because of limited screening. These excitons display a variety of interactions and processes that could be exploited for applications in nanoscale photonics and optoelectronics. Here we report on optical pulse-train generation from individual air-suspended carbon nanotubes under an application of square-wave gate voltages. Electrostatically induced carrier accumulation quenches photoluminescence, while a voltag...

  16. Large enhancement of macroscopic yield in attosecond pulse train assisted harmonic generation

    Gaarde, Mette B.; Schafer, Kenneth J.; Heinrich, Arne; Biegert, Jens; Keller, Ursula

    2005-07-01

    Attosecond pulse trains (APT) are natural tools for controlling strong field processes, due to their periodicity and short duration. Here we present nonadiabatic calculations of the macroscopic harmonic signal created by a gas of helium atoms exposed to a strong infrared (IR) pulse in combination with an APT. We find that the harmonic yield can be enhanced by two to four orders of magnitude for the optimal delays between the IR and the APT pulses. The large enhancement is due to the change in the IR-intensity dependence of both the harmonic strength and phase caused by the presence and timing of the APT. This leads to enhancement of the harmonic yield and improved phase matching conditions over a large volume.

  17. Large enhancement of macroscopic yield in attosecond pulse train-assisted harmonic generation

    Attosecond pulse trains (APT) are natural tools for controlling strong field processes, due to their periodicity and short duration. Here we present nonadiabatic calculations of the macroscopic harmonic signal created by a gas of helium atoms exposed to a strong infrared (IR) pulse in combination with an APT. We find that the harmonic yield can be enhanced by two to four orders of magnitude for the optimal delays between the IR and the APT pulses. The large enhancement is due to the change in the IR-intensity dependence of both the harmonic strength and phase caused by the presence and timing of the APT. This leads to enhancement of the harmonic yield and improved phase matching conditions over a large volume

  18. Wide-Range Temperature Sensors with High-Level Pulse Train Output

    Hammoud, Ahmad; Patterson, Richard L.

    2009-01-01

    Two types of temperature sensors have been developed for wide-range temperature applications. The two sensors measure temperature in the range of -190 to +200 C and utilize a thin-film platinum RTD (resistance temperature detector) as the temperature-sensing element. Other parts used in the fabrication of these sensors include NPO (negative-positive- zero) type ceramic capacitors for timing, thermally-stable film or wirewound resistors, and high-temperature circuit boards and solder. The first type of temperature sensor is a relaxation oscillator circuit using an SOI (silicon-on-insulator) operational amplifier as a comparator. The output is a pulse train with a period that is roughly proportional to the temperature being measured. The voltage level of the pulse train is high-level, for example 10 V. The high-level output makes the sensor less sensitive to noise or electromagnetic interference. The output can be read by a frequency or period meter and then converted into a temperature reading. The second type of temperature sensor is made up of various types of multivibrator circuits using an SOI type 555 timer and the passive components mentioned above. Three configurations have been developed that were based on the technique of charging and discharging a capacitor through a resistive element to create a train of pulses governed by the capacitor-resistor time constant. Both types of sensors, which operated successfully over the wide temperature range, have potential use in extreme temperature environments including jet engines and space exploration missions.

  19. Secondary electron imaging of nanostructures using Extreme Ultra-Violet attosecond pulse trains and Infra-Red femtosecond pulses

    Maarsell, Erik; Arnold, Cord L.; Lorek, Eleonora; Guenot, Diego; Fordell, Thomas; Miranda, Miguel; Mauritsson, Johan; Xu, Hongxing; L' Huillier, Anne; Mikkelsen, Anders [Department of Physics, Lund University, Box 118, 221 00 Lund (Sweden)

    2013-02-15

    Surface electron dynamics unfold at time and length scales down to attoseconds and nanometres, making direct imaging with extreme spatiotemporal resolution highly desirable. However, this has turned out to be a major challenge even with the advent of reliable attosecond light sources. In this paper, photoelectrons from Ag nanowires and nanoparticles excited by extreme ultraviolet (XUV) attosecond pulse trains and infrared femtosecond pulses using a PhotoEmission Electron Microscope (PEEM) are imaged. In addition, the samples were investigated using Scanning Electron Microscopy (SEM) and synchrotron based X-ray photoelectron spectroscopy (XPS). To achieve contrast between the nanostructures and the substrate in the XUV images, three different substrate materials were investigated: Cr, ITO and Au. While plasmonic field enhancement can be observed on all three substrates, only on Au substrates do the Ag nanowires appear significantly brighter than the substrate in XUV-PEEM imaging. 3-photon photoemission imaging of plasmonic hot-spots was performed where the autocorrelation trace is observed in the interference signal between two femtosecond Infra-Red (IR) beams with sub-cycle precision. Finally, using Monte Carlo simulations, it is shown how the secondary electrons imaged in the XUV PEEM can potentially reveal information on the attosecond time scale from the near surface region of the nanostructures. (copyright 2012 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Self-stabilizing optical clock pulse-train generator using SOA and saturable absorber for asynchronous optical packet processing.

    Nakahara, Tatsushi; Takahashi, Ryo

    2013-05-01

    We propose a novel, self-stabilizing optical clock pulse-train generator for processing preamble-free, asynchronous optical packets with variable lengths. The generator is based on an optical loop that includes a semiconductor optical amplifier (SOA) and a high-extinction spin-polarized saturable absorber (SA), with the loop being self-stabilized by balancing out the gain and absorption provided by the SOA and SA, respectively. The optical pulse train is generated by tapping out a small portion of a circulating seed pulse. The convergence of the generated pulse energy is enabled by the loop round-trip gain function that has a negative slope due to gain saturation in the SOA. The amplified spontaneous emission (ASE) of the SOA is effectively suppressed by the SA, and a backward optical pulse launched into the SOA enables overcoming the carrier-recovery speed mismatch between the SOA and SA. Without external control for the loop gain, a stable optical pulse train consisting of more than 50 pulses with low jitter is generated from a single 10-ps seed optical pulse even with a variation of 10 dB in the seed pulse intensity. PMID:23669927

  1. Flow measurements using an Turbo-FLASH sequence with a velocity-encoding pulse train

    Ordinary phase-contrast techniques in MRI for velocity quantification requires long data measurement times in order to acquire images. A snapshot FLASH sequence with velocity-encoding pulses was evaluated for velocity measurement utilizing a specifically designed phantom. A velocity-encoding (900degx-Gs-180degy-Gs-90degy) pulse train was added prior to a standard Turbo-FLASH sequence with centric phase reordering where Gs is a velocity-encoding gradient. Water flow through a tube (Φ=2.25 mm) was imaged with this sequence implemented on a 1.5 T MR unit. Flow signal intensities were acquired with several magnitudes of the velocity-encoding gradient. A mathematical model in which flow was considered to be laminar was fitted to these data and the flow velocity was obtained from a parameter of the model. The measurement time for a single image was about 2 seconds. In order to calculate velocity, several images had to be acquired. When the maximum flow velocity in the tube was less than 30 cm/sec, calculated velocities were in good agreement with mean flow velocities obtained from outflow rates and the cross-sectional area of the tube. Above that velocity, a ghost artifact appeared on the image. Turbo-FLASH sequence with a velocity-encoding pulse train is an efficient means for measuring the velocity of slow flow rates in a short time. (author)

  2. Fundamental modes of a trapped probe photon in optical fibers conveying periodic pulse trains

    Wave modes induced by cross-phase reshaping of a probe photon in the guiding structure of a periodic train of temporal pulses are investigated theoretically with emphasis on exact solutions to the wave equation for the probe. The study has direct connection with recent advances on the issue of light control by light, the focus being on the trapping of a low-power probe by a temporal sequence of periodically matched high-power pulses of a dispersion-managed optical fiber. The problem is formulated in terms of the nonlinear optical fiber equation with averaged dispersion, coupled to a linear equation for the probe including a cross-phase modulation term. Shape-preserving modes which are robust against the dispersion are shown to be induced in the probe, they form a family of mutually orthogonal solitons the characteristic features of which are determined by the competition between the self-phase and cross-phase effects. Considering a specific context of this competition, the theory predicts two degenerate modes representing a train of bright signals and one mode which describes a train of dark signals. When the walk-off between the pump and probe is taken into consideration, these modes have finite-momentum envelopes and none of them is totally transparent vis-a-vis the optical pump soliton.

  3. Coherent lidar modulated with frequency stepped pulse trains for unambiguous high duty cycle range and velocity sensing in the atmosphere

    Lindelöw, Per Jonas Petter; Mohr, Johan Jacob

    2007-01-01

    Range unambiguous high duty cycle coherent lidars can be constructed based on frequency stepped pulse train modulation, even continuously emitting systems could be envisioned. Such systems are suitable for velocity sensing of dispersed targets, like the atmosphere, at fast acquisition rates. The ...... lightwave synthesized frequency sweeper is a suitable generator yielding fast pulse repetition rates and stable equidistant frequency steps. Theoretical range resolution profiles of modulated lidars are presented.......Range unambiguous high duty cycle coherent lidars can be constructed based on frequency stepped pulse train modulation, even continuously emitting systems could be envisioned. Such systems are suitable for velocity sensing of dispersed targets, like the atmosphere, at fast acquisition rates. The...

  4. Generation of Intense Narrow-Band Tunable Terahertz Radiation from Highly Bunched Electron Pulse Train

    Li, Heting; Lu, Yalin; He, Zhigang; Jia, Qika; Wang, Lin

    2016-07-01

    We present the analysis and start-to-end simulation of an intense narrow-band terahertz (THz) source with a broad tuning range of radiation frequency, using a single-pass free electron laser (FEL) driven by a THz-pulse-train photoinjector. The fundamental radiation frequency, corresponding to the spacing between the electron microbunches, can be easily tuned by varying the spacing time between the laser micropulses. Since the prebunched electron beam is highly bunched at the first several harmonics, with the harmonic generation technique, the radiation frequency range can be further enlarged by several times. The start-to-end simulation results show that this FEL is capable of generating a few tens megawatts power, several tens micro-joules pulse energy, and a few percent bandwidth at the frequencies of 0.5-5 THz. In addition, several practical issues are considered.

  5. Effective Study Of S.a.q Training And Tempo Training On Agility And Resting Pulse Rate Among Junior Cricket Players

    S. Mohanasundaram

    2013-08-01

    Full Text Available The purpose of this study is to determine the effect of S.A.Q training and tempo training on agility and resting pulse rate among junior cricket players. Forty five subjects were selected from the Stansford International Higher Secondary School, Puducherry and their age ranged from 14 to 17 years. The subjects were equally divided into three groups with fifteen subjects in each group. The group I was treated with S.A.Q training group, Group II was treated with tempo training group and Group III was treated with control group. Training was given for a period of 12 weeks. The results of pre-test and post-test were statistically analyzed by using analysis of co-variance. The result when compared between the two experimental groups revealed that resting pulse rate had no significant improvement due to S.A.Q training and tempo training when compared to the control group. But agility had significant improvement due to S.A.Q training and tempo training when compared to the control group. The result revealed that it was found that S.A.Q training group had significant effect on agility.

  6. Frequency modulated few-cycle optical pulse trains induced controllable ultrafast coherent population oscillations in three-level atomic systems

    Kumar, Parvendra

    2012-01-01

    We report a study on the ultrafast coherent population oscillations (UCPO) in sodium atoms induced by the frequency modulated few-cycle optical pulse trains. The phenomenon of UCPO is investigated by numerically solving the appropriate density matrix equations beyond the rotating wave approximation. We demonstrate that the quantum state of the atoms and the frequency of UCPO may be controlled by controlling the number of pulses in the pulse trains and the pulse repetition time respectively. Moreover, the robustness of population transfer against the variation of laser pulse parameters is also investigated. The proposed scheme may be useful for the creation of atomic beam in selected quantum state for desired time duration and may have potential applications in ultrafast optical switching.

  7. Pulse-train modulation in a picosecond self-mode-locked laser

    Pulse-train modulation was observed in a picosecond self-mode-locked Ti:sapphire laser with pump-power dependence when it was operated around the degenerate cavity configuration. By increasing the optical pumping power, the envelope of the periodic amplitude modulation splits into two or three clusters with enhanced modulation depth, and the amplitude modulation eventually becomes disordered at higher pump power. The amplitude modulation may be supported by exciting two sets of non-degenerate longitudinally mode-locked supermodes due to spatially inhomogeneous gain modulation in the Ti:sapphire crystal.

  8. Properties of unipolar magnetic field pulse trains generated by lightning discharges

    Kolmašová, Ivana; Santolík, Ondřej

    2013-01-01

    Roč. 40, č. 8 (2013), 1637–1641. ISSN 0094-8276 R&D Projects: GA ČR GA205/09/1253 Grant ostatní: Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100421206 Institutional support: RVO:68378289 Keywords : train of pulses * dart-stepped leader * K change Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.456, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/grl.50366/abstract

  9. Analog simulation on enhanced ac Josephson effect for junction driven by pulse train current

    The enhanced ac Josephson effect is studied based on an analog simulation when the junction is driven by an rf-signal source. On the basis of the resistively shunted Josephson junction model driven by a pulse train current, larger rf-induced current step-heights in the current-voltage characteristics were obtained in comparison with those obtained by a monochromatic sinusoidal drive. This result is considered to be originated by the harmonics of the rf-signal. In addition, the maximum value of the step-height is independent on the step number. (orig.)

  10. Polarization fatigue in poly(vinylidene fluoride (78%)-trifluoroethylene (22%)) ferroelectric thin films: a pulse train study

    This paper investigates the influences of polarization fatigue on remanent polarization and switching time by pulse train measurements in ferroelectric poly(vinylidene fluoride (78%) and trifluoroethylene (22%)) thin films. Fatigue was carried out by a series of bipolar switching pulses with constant pulse width (on-time) and various interval times between pulses (off-time). The experimental observations indicated that the off-time period showed no obvious influence on fatigue rate and the switching time increased with the increase of fatigue cycles. The origination of these phenomena was discussed according to the charge injection model. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  11. Effective Study Of S.a.q Training And Tempo Training On Agility And Resting Pulse Rate Among Junior Cricket Players

    S. Mohanasundaram; G. VASANTHI

    2013-01-01

    The purpose of this study is to determine the effect of S.A.Q training and tempo training on agility and resting pulse rate among junior cricket players. Forty five subjects were selected from the Stansford International Higher Secondary School, Puducherry and their age ranged from 14 to 17 years. The subjects were equally divided into three groups with fifteen subjects in each group. The group I was treated with S.A.Q training group, Group II was treated with tempo training group and Group I...

  12. Nonlinear increase in the interaction efficiency of a second pulse with a target upon excitation of a plasma by a train of pulses from a Nd:YAG laser

    The efficiency of hole drilling in an aluminium plate was studied experimentally upon excitation of a plasma on its surface in air by a train of pulses from a Nd:YAG laser, the interval between pulses being 15-20 μs. It was found that the crater depth increases nonmonotonically with each successive pulse of the train. A nonlinear, more than by a factor of six, increase in the depth was detected upon interaction of the second pulse with the target. The mechanism explaining this increase in the interaction efficiency of the second pulse in the train with the target is proposed. (interaction of laser radiation with matter)

  13. Effects of pulse current on endurance exercise and its anti-fatigue properties in the hepatic tissue of trained rats.

    Chang, Qi; Miao, Xinfang; Ju, Xiaowei; Zhu, Lvgang; Huang, Changlin; Huang, Tao; Zuo, Xincheng; Gao, Chunfang

    2013-01-01

    Fatigue is synonymous with a wide spectrum of familiar physiological conditions, from pathology and general health, to sport and physical exercise. Strenuous, prolonged exercise training causes fatigue. Although several studies have investigated the effects of electrical stimulation frequency on muscle fatigue, the effects of percutaneous pulse current stimulation on fatigue in the hepatic tissue of trained rats is still unclear. In order to find an effective strategy to prevent fatigue or enhance recovery, the effects of pulse current on endurance exercise and its anti-fatigue properties in exercised rats were studied. Rats were subjected to one, three or five weeks of swimming exercise training. After exercise training, rats in the treated group received daily applications of pulse current. All rats were sacrificed after one, three or five weeks of swimming exercise, and the major biochemical indexes were measured in serum and liver. The results demonstrate that pulse current could prolong the exhaustion swimming time, as well as decrease serum ALT, AST and LD levels and liver MDA content. It also elevated serum LDH activity, liver SOD activity and glycogen content. Furthermore, pulse current increased the expression of Bcl-2 and decreased the expression of Bax. Taken together, these results show that pulse current can elevate endurance capacity and facilitate recovery from fatigue. PMID:24116026

  14. Effects of pulse current on endurance exercise and its anti-fatigue properties in the hepatic tissue of trained rats.

    Qi Chang

    Full Text Available Fatigue is synonymous with a wide spectrum of familiar physiological conditions, from pathology and general health, to sport and physical exercise. Strenuous, prolonged exercise training causes fatigue. Although several studies have investigated the effects of electrical stimulation frequency on muscle fatigue, the effects of percutaneous pulse current stimulation on fatigue in the hepatic tissue of trained rats is still unclear. In order to find an effective strategy to prevent fatigue or enhance recovery, the effects of pulse current on endurance exercise and its anti-fatigue properties in exercised rats were studied. Rats were subjected to one, three or five weeks of swimming exercise training. After exercise training, rats in the treated group received daily applications of pulse current. All rats were sacrificed after one, three or five weeks of swimming exercise, and the major biochemical indexes were measured in serum and liver. The results demonstrate that pulse current could prolong the exhaustion swimming time, as well as decrease serum ALT, AST and LD levels and liver MDA content. It also elevated serum LDH activity, liver SOD activity and glycogen content. Furthermore, pulse current increased the expression of Bcl-2 and decreased the expression of Bax. Taken together, these results show that pulse current can elevate endurance capacity and facilitate recovery from fatigue.

  15. Photoionization dynamics in the presence of attosecond pulse trains and strong fields

    Highlights: ► We study two-color ionization atoms with attosecond pulse trains and strong fields. ► Floquet formalism is used to explain interferences in ionization. ► We discuss the control of photoionization with use of strong fields. - Abstract: We present experimental results and a theoretical framework for understanding the ionization dynamics in atoms exposed to XUV attosecond pulse trains and strong multi-cycle infrared (IR) fields. We invoke the Floquet formalism to model dressed atomic states as a manifold of Fourier components spaced by the laser frequency. In XUV-IR pump–probe measurements, we observe that the ionization yield oscillates due to quantum interference between photo-excitation paths to a Floquet state. We show that the intensity-dependent shifts of atomic structure modify the ionization channels and the associated interference phase. We extract this phase variation and compare it with simulations. These results provide a comprehensive description of the two-color ionization process and enable new schemes for control of attosecond ionization and fragmentation dynamics

  16. Accessing properties of electron wave packets generated by attosecond pulse trains through time-dependent calculations

    We present a time-dependent method for calculating the energy-dependent atomic dipole phase that an electron acquires when it is ionized by the absorption of a single ultraviolet photon. Our approach exactly mirrors the method used to experimentally characterize a train of attosecond pulses. In both methods the total electron phase is measured (calculated) via a two-photon interference involving the absorption or emission of an additional infrared photon in the continuum. In our calculation we use a perfect (zero spectral phase) light field and so extract the atomic dipole phase directly from the electron wave packet. We calculate the atomic phase for argon, neon, and helium at low infrared intensities and compare them to previous perturbative calculations. At moderate infrared probe intensities, we find that that the dipole phase can still be reliably determined using two-photon interference, even when higher-order processes are non-negligible. We also show that a continuum structure, in this case a Cooper minimum in argon, significantly affects the probability for infrared absorption and emission over a range of energies around the minimum, even at low infrared intensities. We conclude that well-characterized attosecond pulse trains can be used to examine continuum structures in atoms and molecules

  17. Photoionization dynamics in the presence of attosecond pulse trains and strong fields

    Shivaram, Niranjan; Timmers, Henry [Department of Physics and College of Optical Sciences, University of Arizona, Tucson, AZ 85721 (United States); Tong, Xiao-Min [Center for Computational Sciences, University of Tsukuba, Ibaraki 305-8573 (Japan); Sandhu, Arvinder, E-mail: sandhu@physics.arizona.edu [Department of Physics and College of Optical Sciences, University of Arizona, Tucson, AZ 85721 (United States)

    2013-03-12

    Highlights: ► We study two-color ionization atoms with attosecond pulse trains and strong fields. ► Floquet formalism is used to explain interferences in ionization. ► We discuss the control of photoionization with use of strong fields. - Abstract: We present experimental results and a theoretical framework for understanding the ionization dynamics in atoms exposed to XUV attosecond pulse trains and strong multi-cycle infrared (IR) fields. We invoke the Floquet formalism to model dressed atomic states as a manifold of Fourier components spaced by the laser frequency. In XUV-IR pump–probe measurements, we observe that the ionization yield oscillates due to quantum interference between photo-excitation paths to a Floquet state. We show that the intensity-dependent shifts of atomic structure modify the ionization channels and the associated interference phase. We extract this phase variation and compare it with simulations. These results provide a comprehensive description of the two-color ionization process and enable new schemes for control of attosecond ionization and fragmentation dynamics.

  18. Nonlinear Fourier transformation spectroscopy of small molecules with intense attosecond pulse train

    We have developed an attosecond nonlinear molecular spectroscopic method called nonlinear Fourier transformation spectroscopy (NFTS) that uses an intense attosecond pulse train (APT) to induce multiphoton ionization processes. In the NFTS method, in addition to characterization of the temporal profile of attosecond pulses, the nonlinear molecular responses are encoded in the interferometric autocorrelation traces depending on the molecular species, their fragment ions and their kinetic energy distributions. The principle and applicability of the NFTS method are described in this paper along with the numerical simulations. The method is applied to diatomic molecules (N2 , D2 and O2) and polyatomic molecules (CO2, CH4 and SF6). Our results highlight the fact that nonlinear spectroscopic information of molecules in the short wavelength region can be obtained through the irradiation of intense APT by taking advantage of the broad spectral bandwidth of attosecond pulses. The development of the nonlinear spectroscopic method in attoseconds is expected to pave the way to investigate the ultrafast intramolecular electron motion such as ultrafast charge migration and electron correlation. (review article)

  19. Nonlinear Fourier transformation spectroscopy of small molecules with intense attosecond pulse train

    Okino, T.; Furukawa, Y.; Shimizu, T.; Nabekawa, Y.; Yamanouchi, K.; Midorikawa, K.

    2014-06-01

    We have developed an attosecond nonlinear molecular spectroscopic method called nonlinear Fourier transformation spectroscopy (NFTS) that uses an intense attosecond pulse train (APT) to induce multiphoton ionization processes. In the NFTS method, in addition to characterization of the temporal profile of attosecond pulses, the nonlinear molecular responses are encoded in the interferometric autocorrelation traces depending on the molecular species, their fragment ions and their kinetic energy distributions. The principle and applicability of the NFTS method are described in this paper along with the numerical simulations. The method is applied to diatomic molecules (N2 , D2 and O2) and polyatomic molecules (CO2, CH4 and SF6). Our results highlight the fact that nonlinear spectroscopic information of molecules in the short wavelength region can be obtained through the irradiation of intense APT by taking advantage of the broad spectral bandwidth of attosecond pulses. The development of the nonlinear spectroscopic method in attoseconds is expected to pave the way to investigate the ultrafast intramolecular electron motion such as ultrafast charge migration and electron correlation.

  20. Effect of treadmill training on peak expiratory flow rate and resting pulse rate among young adult

    SUKANYA BARDHAN

    2013-01-01

    Full Text Available The present was designed to find out the effect of treadmill training on peak expiratory flow rate and resting pulse rate among young adult boys. The random group design was adopted for this study. Participants were randomly assigned to experimental and control groups. For this purpose, Ten (N = 10 male students of B.A., B.C.A and B.Com from Post Graduate Government College, Sector-11, Chandigarh aged 19-25 years participate in the study. The subjects were being randomly divided into two groups: A (N = 05; Experimental and B (N = 05; Control. Paired "t" test was employed to identify significant differences between the pretest and post-test mean of the two groups through Medical Calculation Version 12.5. To test the hypotheses, the level of significance was set at 0.05. It is concluded that insignificant difference has been found between pre-test and post test (Experimental Group scores of Peak Expiratory Flow Rate (PEFR among young adult boys. No significant difference has been found between the pre-test and post-test(Control Group scores of Peak Expiratory Flow Rate (PEFR among young adult boys. No significant difference has been found between the pre-test and post-test (Experimental Group scores of Resting Pulse Rate among young adult boys. No significant difference has been found between the pre-test and post-test (Control Group scores of Resting Pulse Rate among young adult boys.

  1. Electric pulse stimulation of cultured murine muscle cells reproduces gene expression changes of trained mouse muscle.

    Nathalie Burch

    Full Text Available Adequate levels of physical activity are at the center of a healthy lifestyle. However, the molecular mechanisms that mediate the beneficial effects of exercise remain enigmatic. This gap in knowledge is caused by the lack of an amenable experimental model system. Therefore, we optimized electric pulse stimulation of muscle cells to closely recapitulate the plastic changes in gene expression observed in a trained skeletal muscle. The exact experimental conditions were established using the peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha as a marker for an endurance-trained muscle fiber. We subsequently compared the changes in the relative expression of metabolic and myofibrillar genes in the muscle cell system with those observed in mouse muscle in vivo following either an acute or repeated bouts of treadmill exercise. Importantly, in electrically stimulated C2C12 mouse muscle cells, the qualitative transcriptional adaptations were almost identical to those in trained muscle, but differ from the acute effects of exercise on muscle gene expression. In addition, significant alterations in the expression of myofibrillar proteins indicate that this stimulation could be used to modulate the fiber-type of muscle cells in culture. Our data thus describe an experimental cell culture model for the study of at least some of the transcriptional aspects of skeletal muscle adaptation to physical activity. This system will be useful for the study of the molecular mechanisms that regulate exercise adaptation in muscle.

  2. Unified parameter for localization in isotope-selective rotational excitation of diatomic molecules using a train of optical pulses

    Matsuoka, Leo

    2015-01-01

    We obtained a simple theoretical unified parameter for the characterization of rotational population propagation of diatomic molecules in a periodic train of resonant optical pulses. The parameter comprises the peak intensity and interval between the pulses, and the level energies of the initial and final rotational states of the molecule. Using the unified parameter, we can predict the upper and lower boundaries of probability localization on the rotational level network, including the effec...

  3. Signatures of nuclear motion in molecular high-order harmonics and in the generation of attosecond pulse trains by ultrashort intense laser pulses

    Bandrauk, André D.; Chelkowski, Szczepan; Lu, Huizhong

    2009-04-01

    Non-Born-Oppenheimer time-dependent Shrödinger equation numerical simulations of the nonlinear nonperturbative response of 1D H2, H+2 molecules (and their isotopes) in few cycle intense 800 nm laser pulses are presented to study the effect of nuclear motion on molecular high-order harmonic generation. A time-frequency analysis is used to identify electron recollision and recombination times responsible for the generation of attosecond pulse trains during the nuclear motion. A very strong signature of nuclear motion is seen in the time profiles of high-order harmonics. In the case of high laser intensity (I sime 1015 W cm-2) the nuclear motion shortens the part of the attosecond pulse train originating from the first electron contribution and may enhance the onset of the second electron contribution for longer pulses. Molecular motion thus can act as an important 'time-gating' for controlling the length of generated attosecond pulses. The shape of time profiles of harmonics can thus be used for monitoring the nuclear motion. In the case of lower laser intensity, I sime 4 × 1014 W cm-2, we also find in time profiles a clear signature of electron excitation due to recollision of the returning electron.

  4. Signatures of nuclear motion in molecular high-order harmonics and in the generation of attosecond pulse trains by ultrashort intense laser pulses

    Non-Born-Oppenheimer time-dependent Schroedinger equation numerical simulations of the nonlinear nonperturbative response of 1D H2, H+2 molecules (and their isotopes) in few cycle intense 800 nm laser pulses are presented to study the effect of nuclear motion on molecular high-order harmonic generation. A time-frequency analysis is used to identify electron recollision and recombination times responsible for the generation of attosecond pulse trains during the nuclear motion. A very strong signature of nuclear motion is seen in the time profiles of high-order harmonics. In the case of high laser intensity (I ≅ 1015 W cm-2) the nuclear motion shortens the part of the attosecond pulse train originating from the first electron contribution and may enhance the onset of the second electron contribution for longer pulses. Molecular motion thus can act as an important 'time-gating' for controlling the length of generated attosecond pulses. The shape of time profiles of harmonics can thus be used for monitoring the nuclear motion. In the case of lower laser intensity, I ≅ 4 x 1014 W cm-2, we also find in time profiles a clear signature of electron excitation due to recollision of the returning electron.

  5. Ti:sapphire/KrF hybrid laser system generating trains of subterawatt subpicosecond UV pulses

    The GARPUN-MTW Ti:sapphire/KrF hybrid laser system is used to investigate different multipass schemes for amplifying trains of ultrashort pulses (USPs) of subpicosecond duration. It is shown that, for an USP repetition period of 3 – 5 ns, which exceeds the gain-medium recovery time (∼2 ns), trains are amplified in the same way as single USPs. Due to this, a train can efficiently extract pump energy from the amplifier and sum energies of individual USPs. The energy of a four-USP train, extracted during four passes through the preamplifier and two passes through the final KrF amplifier (4 + 2 scheme), is saturated at a level of 1.6 J and corresponds to maximum USP peak powers of about 0.6 TW. The energy of amplified spontaneous emission (ASE), on the contrary, rapidly increases at a large total gain length Leff ≈ 6 m and is approximately equal to the USP energy. In the (4 + 1) and (2 + 2) schemes the USP energy decreases only slightly, to Eout = 1.3 and 1.2 J, and the ASE fraction is reduced to about 10% and 3%, respectively. USP self-focusing leads to multiple laser beam filamentation and a 200-fold local increase in the radiation intensity in filaments, to ∼2 × 1011 W cm-2, a level at which the nonlinear loss in the output CaF2 windows of the KrF amplifier, caused by three-photon absorption, nonlinear scattering, and broadening of the radiation spectrum to a value exceeding the gain band of the KrF laser transition, becomes the main factor determining the saturation of the USP output energy. (lasers)

  6. Complete population transfer in a three-state quantum system by a train of pairs of coincident pulses

    Rangelov, Andon A.; Vitanov, Nikolay V.

    2012-01-01

    A technique for complete population transfer between the two end states $\\ket{1}$ and $\\ket{3}$ of a three-state quantum system with a train of $N$ pairs of resonant and coincident pump and Stokes pulses is introduced. A simple analytic formula is derived for the ratios of the pulse amplitudes in each pair for which the maximum transient population $P_2(t)$ of the middle state $\\ket{2}$ is minimized, $P_2^{\\max}=\\sin^2(\\pi/4N)$. It is remarkable that, even though the pulses are on exact reson...

  7. Complete population transfer in a three-state quantum system by a train of pairs of coincident pulses

    Rangelov, Andon A

    2012-01-01

    A technique for complete population transfer between the two end states $\\ket{1}$ and $\\ket{3}$ of a three-state quantum system with a train of $N$ pairs of resonant and coincident pump and Stokes pulses is introduced. A simple analytic formula is derived for the ratios of the pulse amplitudes in each pair for which the maximum transient population $P_2(t)$ of the middle state $\\ket{2}$ is minimized, $P_2^{\\max}=\\sin^2(\\pi/4N)$. It is remarkable that, even though the pulses are on exact resonance, $P_2(t)$ is damped to negligibly small values even for a small number of pulse pairs. The population dynamics resembles generalized $\\pi$-pulses for small $N$ and stimulated Raman adiabatic passage for large $N$ and therefore this technique can be viewed as a bridge between these well-known techniques.

  8. Optimal control of laser plasma instabilities using Spike Trains of Uneven Duration and Delay (STUD pulses) for ICF and IFE

    Afeyan, Bedros; Hüller, Stefan

    2013-11-01

    An adaptive method of controlling parametric instabilities in laser produced plasmas is proposed. It involves fast temporal modulation of a laser pulse on the fastest instability's amplification time scale, adapting to changing and unknown plasma conditions. These pulses are comprised of on and off sequences having at least one or two orders of magnitude contrast between them. Such laser illumination profiles are called STUD pulses for Spike Trains of Uneven Duration and Delay. The STUD pulse program includes scrambling the speckle patterns spatially in between the laser spikes. The off times allow damping of driven waves. The scrambling of the hot spots allows tens of damping times to elapse before hot spot locations experience recurring high intensity spikes. Damping in the meantime will have healed the scars of past growth. Another unique feature of STUD pulses on crossing beams is that their temporal profiles can be interlaced or staggered, and their interactions thus controlled with an on-off switch and a dimmer.

  9. Optimal control of laser plasma instabilities using Spike Trains of Uneven Duration and Delay (STUD pulses) for ICF and IFE

    Afeyan, Bedros

    2012-01-01

    An adaptive method of controlling parametric instabilities in laser produced plasmas is proposed. It involves fast temporal modulation of a laser pulse on the fastest instability's amplification time scale, adapting to changing and unknown plasma conditions. These pulses are comprised of on and off sequences having at least one or two orders of magnitude contrast between them. Such laser illumination profiles are called STUD pulses for Spike Trains of Uneven Duration and Delay. The STUD pulse program includes scrambling the speckle patterns spatially in between the laser spikes. The off times allow damping of driven waves. The scrambling of the hot spots allows tens of damping times to elapse before hot spot locations experience recurring high intensity spikes. Damping in the meantime will have healed the scars of past growth. Another unique feature of STUD pulses on crossing beams is that their temporal profiles can be interlaced or staggered, and their interactions thus controlled with an on-off switch and ...

  10. Effects of Pulse Current on Endurance Exercise and Its Anti-Fatigue Properties in the Hepatic Tissue of Trained Rats

    Qi Chang; Xinfang Miao; Xiaowei Ju; Lvgang Zhu; Changlin Huang; Tao Huang; Xincheng Zuo; Chunfang Gao

    2013-01-01

    Fatigue is synonymous with a wide spectrum of familiar physiological conditions, from pathology and general health, to sport and physical exercise. Strenuous, prolonged exercise training causes fatigue. Although several studies have investigated the effects of electrical stimulation frequency on muscle fatigue, the effects of percutaneous pulse current stimulation on fatigue in the hepatic tissue of trained rats is still unclear. In order to find an effective strategy to prevent fatigue or en...

  11. Studies to assess the effect of pet training aids specifically remote static pulse systems on the welfare of domestic dogs

    Cooper, Jonathan; Wright, Hannah; Mills, Daniel; Casey, Rachel; Blackwell, Emily; Van Driel, Katja; Lines, Jeff

    2013-01-01

    This project assessed the welfare of dogs trained with pet training aids, specifically remote static pulse collar systems (e-collars). Previous work has focused on a very limited number of devices in a very limited range of contexts and the evidence of the impact of such devices on dog's overall quality of life is inconclusive. Project AW1402 aimed to assess the physical characteristics of the e-collars and the physiological, behavioural and psychological consequences of their use in dog trai...

  12. The pulsed linear induction motor concept for high-speed trains

    Turman, B.N.; Marder, B.M.; Rohwein, G.J.; Aeschliman, D.P.; Kelley, J.B.; Cowan, M.; Zimmerman, R.M.

    1995-06-01

    The SERAPBIM (SEgmented RAil PHased Induction Motor) concept is a linear induction motor concept which uses rapidly-pulsed magnetic fields and a segmented reaction rail, as opposed to low-frequency fields and continuous reaction rails found in conventional linear induction motors. These improvements give a high-traction, compact, and efficient linear motor that has potential for advanced high speed rail propulsion. In the SERAPBIM concept, coils on the vehicle push against a segmented aluminum rail, which is mounted on the road bed. Current is pulsed as the coils cross an edge of the segmented rail, inducing surface currents which repel the coil. The coils must be pulsed in synchronization with the movement by reaction rail segments. This is provided by a sense-and-fire circuit that controls the pulsing of the power modulators. Experiments were conducted to demonstrate the feasibility of the pulsed induction motor and to collect data that could be used for scaling calculations. A 14.4 kg aluminum plate was accelerated down a 4 m track to speeds of over 15 m/sec with peak thrust up to 18 kN per coilset. For a trainset capable of 200 mph speed, the SERAPHIM concept design is based on coils which are each capable of producing up to 3.5 kN thrust, and 30 coil pairs are mounted on each power car. Two power cars, one at each end of the train, provide 6 MW from two gas turbine prime power units. The thrust is about 210.000 N and is essentially constant up to 200 km/hr since wheel slippage does not limit thrust as with conventional wheeled propulsion. A key component of the SERAPHIM concept is the use of passive wheel-on-rah support for the high speed vehicle. Standard steel wheels are capable of handling over 200 mph. The SERAPHIM cost is comparable to that for steel-wheel high-speed rail, and about 10% to 25% of the projected costs for a comparable Maglev system.

  13. Studies of dark resonances in Rb atoms in the field of light pulse train

    Dark resonances in 87Rb vapor in the field of a femtosecond laser pulse train have been studied theoretically and experimentally. Three- and four-level schemes of interaction between an 87Rb atom and the field, which are formed by the field-coupled magnetic sublevels of states 2S1=2 and 3P3=2 of the rubidium atom have been analyzed. The position and the shape of the experimentally recorded dark resonance correspond to the results of our calculations. It has been shown that the interaction between rubidium vapor and a polychromatic field allows the signal to be enhanced substantially in comparison with that in the case of bichromatic field.

  14. Observation of pulsed x-ray trains produced by laser-electron Compton scatterings

    X-ray generation based on laser-electron Compton scattering is one attractive method to achieve a compact laboratory-sized high-brightness x-ray source. We have designed, built, and tested such a source; it combines a 50 MeV multibunch electron linac with a mode-locked 1064 nm laser stored and amplified in a Fabry-Perot optical cavity. We directly observed trains of pulsed x rays using a microchannel plate detector; the resultant yield was found to be 1.2x105 Hz in good agreement with prediction. We believe that the result has demonstrated good feasibility of linac-based compact x-ray sources via laser-electron Compton scatterings.

  15. Quantum path control using attosecond pulse trains via UV-assisted resonance enhance ionization

    李芳; 魏来; 何志聪

    2015-01-01

    We theoretically investigate the quantum path selection in an ultraviolet (UV)-assisted near-infrared field with an UV energy below the ionization threshold. By calculating the ionization probability with different assistant UV frequencies, we find that a resonance-enhanced ionization peak emerges in the region Euvpulse train (APT) centered in the resonance region, we show that the short quantum path can be well selected in the continuum case. By performing the electron trajectory analysis, we have further explained the physical mechanism of the quantum path selection. Moreover, we also demonstrate that in the resonance region, the harmonic emission from the selected paths is more efficient than that with the APT energy above the ionization threshold.

  16. Two-photon double ionization of neon using an intense attosecond pulse train

    Manschwetus, B; Campi, F; Maclot, S; Coudert-Alteirac, H; Lahl, J; Wikmark, H; Rudawski, P; Heyl, C M; Farkas, B; Mohamed, T; L'Huillier, A; Johnsson, P

    2016-01-01

    We present the first demonstration of two-photon double ionization of neon using an intense extreme ultraviolet (XUV) attosecond pulse train (APT) in a photon energy regime where both direct and sequential mechanisms are allowed. For an APT generated through high-order harmonic generation (HHG) in argon we achieve a total pulse energy close to 1 $\\mu$J, a central energy of 35 eV and a total bandwidth of $\\sim30$ eV. The APT is focused by broadband optics in a neon gas target to an intensity of $3\\cdot10^{12} $W$\\cdot$cm$^{-2}$. By tuning the photon energy across the threshold for the sequential process the double ionization signal can be turned on and off, indicating that the two-photon double ionization predominantly occurs through a sequential process. The demonstrated performance opens up possibilities for future XUV-XUV pump-probe experiments with attosecond temporal resolution in a photon energy range where it is possible to unravel the dynamics behind direct vs. sequential double ionization and the asso...

  17. Interferometric autocorrelation of an attosecond pulse train calculated using feasible formulae

    The autocorrelation trace of an attosecond pulse train (APT) directly revealed the pulse envelope in our recent experiment on measuring the two-photon Coulomb explosion of a nitrogen molecule as a correlation signal. Although the spatial overlap of the two replicas of the APT in the correlation measurement was only achieved near the focal region owing to the spatial split of the measured APT field, which is a situation quite different from that of the correlation measurement using a Michelson interferometer, the interference fringes clearly appeared on the correlation envelope and provedthe odd symmetry of the electric field to the time translation with a half-period of the driving laser field. In this paper, we show a simple and practical analysis for the propagation and the nonlinear interaction of an APT to simulate the experimental result of the interferometric autocorrelation of the spatially split APT. The spatial convolution of the focused electric field is essential for obtaining the fringes. We also discuss how the autocorrelation should be described in the context of the second-order perturbation theory within a dipole approximation

  18. EXponentially Converging Eradication Pulse Train (EXCEPT) for solvent-signal suppression in investigations with variable T1 times.

    Satterfield, Emmalou T; Pfaff, Annalise R; Zhang, Wenjia; Chi, Lingyu; Gerald, Rex E; Woelk, Klaus

    2016-07-01

    Selective presaturation is a common technique for suppressing excessive solvent signals during proton NMR analysis of dilute samples in protic solvents. When the solvent T1 relaxation time constant varies within a series of samples, parameters for the presaturation sequence must often be re-adjusted for each sample. The EXCEPT (EXponentially Converging Eradication Pulse Train) presaturation pulse sequence was developed to eliminate time consuming pulse-parameter re-optimization as long as the variation in the solvent's T1 remains within an order of magnitude. EXCEPT consists of frequency-selective inversion pulses with progressively decreasing interpulse delays. The interpulse delays were optimized to encompass T1 relaxation times ranging from 1 to 10s, but they can be easily adjusted by a single factor for other ranges that fall within an order of magnitude with respect to T1. Sequences with different numbers of inversion pulses were tested to maximize suppression while minimizing the number of pulses and thus the total time needed for suppression. The EXCEPT-16 experiment, where 16 denotes the number of inversion pulses, was found satisfactory for many standard applications. Experimental results demonstrate that EXCEPT provides effective T1-insensitive solvent suppression as predicted by the theory. The robustness of EXCEPT with respect to changes in solvent T1 allows NMR investigations to be carried out for a series of samples without the need for pulse-parameter re-optimization for each sample. PMID:27179454

  19. EXponentially Converging Eradication Pulse Train (EXCEPT) for solvent-signal suppression in investigations with variable T1 times

    Satterfield, Emmalou T.; Pfaff, Annalise R.; Zhang, Wenjia; Chi, Lingyu; Gerald, Rex E.; Woelk, Klaus

    2016-07-01

    Selective presaturation is a common technique for suppressing excessive solvent signals during proton NMR analysis of dilute samples in protic solvents. When the solvent T1 relaxation time constant varies within a series of samples, parameters for the presaturation sequence must often be re-adjusted for each sample. The EXCEPT (EXponentially Converging Eradication Pulse Train) presaturation pulse sequence was developed to eliminate time consuming pulse-parameter re-optimization as long as the variation in the solvent's T1 remains within an order of magnitude. EXCEPT consists of frequency-selective inversion pulses with progressively decreasing interpulse delays. The interpulse delays were optimized to encompass T1 relaxation times ranging from 1 to 10 s, but they can be easily adjusted by a single factor for other ranges that fall within an order of magnitude with respect to T1. Sequences with different numbers of inversion pulses were tested to maximize suppression while minimizing the number of pulses and thus the total time needed for suppression. The EXCEPT-16 experiment, where 16 denotes the number of inversion pulses, was found satisfactory for many standard applications. Experimental results demonstrate that EXCEPT provides effective T1-insensitive solvent suppression as predicted by the theory. The robustness of EXCEPT with respect to changes in solvent T1 allows NMR investigations to be carried out for a series of samples without the need for pulse-parameter re-optimization for each sample.

  20. Influence of aerobic exercise training on post-exercise responses of aortic pulse pressure and augmentation pressure in postmenopausal women

    Nobuhiko eAkazawa

    2015-10-01

    Full Text Available Central arterial blood pressure (BP is more predictive of future cardiovascular events than is brachial BP because it reflects the BP load imposed on the left ventricle with greater accuracy. However, little is known about the effects of exercise training on central hemodynamic response to acute exercise. The purpose of the present study was to determine the influence of an aerobic exercise regimen on the response of aortic BP after a single aerobic exercise in postmenopausal women. Nine healthy postmenopausal women (age: 61 ± 2 years participated in a 12-week aerobic exercise training regimen. Before and after the training, each subjects performed a single bout of cycling at ventilatory thresholds for 30 min. We evaluated the post-exercise aortic BP response, which was estimated via the general transfer function from applanation tonometry. After the initial pre-training aerobic exercise session, aortic BP did not change significantly: however, aortic pulse pressure and augmentation pressure were significantly attenuated after the single aerobic exercise session following the 12-week training regimen. The present study demonstrated that a regular aerobic exercise training regimen induced the post-exercise reduction of aortic pulse pressure and augmentation pressure. Regular aerobic exercise training may enhance post-exercise reduction in aortic BP.

  1. Propagation of two short laser pulse trains in a $\\Lambda$-type three-level medium under conditions of electromagnetically induced transparency

    Buica, Gabriela

    2014-01-01

    We investigate the dynamics of a pair of short laser pulse trains propagating in a medium consisting of three-level $\\Lambda$-type atoms by numerically solving the Maxwell-Schr\\"odinger equations for atoms and fields. By performing propagation calculations with different parameters, under conditions of electromagnetically induced transparency, we compare the propagation dynamics by a single pair of probe and coupling laser pulses and by probe and coupling laser pulse trains. We discuss the influence of the coupling pulse area, number of pulses, and detunings on the probe laser propagation and realization of electromagnetically induced transparency conditions, as well on the formation of a dark state.

  2. Generation of tailored pulse trains for efficient material processing by a high power MOPA system with birefringence compensation

    A flash lamp pumped, acousto-optical Q-switched Nd:YAG master oscillator power amplifier (MOPA) system with an average output power of almost 150 W and a beam quality of M2 < 2.5 is developed. The system operates with a 100 Hz repetition rate for the flash lamps. In each pumping pulse a pulse train of 5 to 40 Q-switched laser pulses is generated. The pulse length is from 25 to 150 ns. A high beam quality of the amplified beam is realized by an elaborate amplifier design and a careful alignment of the beam diameter to the amplifier rods. Additionally, the thermally induced birefringence of the amplifiers is compensated by a 90° rotator and an optical image-relay system between two identical amplifier rods, so that a linear polarized laser beam could be achieved with depolarization losses below 2%

  3. Probing with randomly interleaved pulse train bridges the gap between ultrafast pump-probe and nanosecond flash photolysis.

    Nakagawa, Tatsuo; Okamoto, Kido; Hanada, Hiroaki; Katoh, Ryuzi

    2016-04-01

    Despite the long-standing importance of transient absorption (TA) spectroscopy, many researchers remain frustrated by the difficulty of measuring the nanosecond range in a wide spectral range. To address this shortcoming, we propose a TA spectrophotometer in which there is no synchronization between a pump pulse and a train of multiple probe pulses from a picosecond supercontinuum light source, termed the randomly-interleaved-pulse-train (RIPT) method. For each pump pulse, many monochromatized probe pulses impinge upon the sample, and the associated pump-probe time delays are determined passively shot by shot with subnanosecond accuracy. By repeatedly pumping with automatically varying time delays, a TA temporal profile that covers a wide dynamic range from subnanosecond to milliseconds is simultaneously obtained. By scanning wavelength, this single, simple apparatus acquires not only wide time range TA profiles, but also broadband TA spectra from the visible through the near-infrared regions. Furthermore, we present a typical result to demonstrate how the RIPT method may be used to correct for fluorescence, which often pollutes TA curves. PMID:27192271

  4. Production of intense attosecond vector beam pulse trains based on harmonics

    Han, Yu-Jing; Liao, Guo-Qian; Chen, Li-Ming; Li, Yu-Tong; Wang, Wei-Min; Zhang, Jie

    2015-11-01

    We provide the first report on the harmonics generated by an intense femtosecond vector beam that is normally incident on a solid target. By using 2D particle-in-cell (PIC) codes, we observe the third and the fifth harmonic signals with the same vector structure as the driving beam, and obtain an attosecond vector beam pulse train. We also show that the conversion efficiencies of the third and the fifth harmonics reach their maxima for a plasma density of four times the critical density due to the plasma resonating with the driving force. This method provides a new means of generating intense extreme ultraviolet (XUV) vector beams via ultra-intense laser-driven harmonics. Project supported by the National Basic Research Program of China (Grant Nos. 2013CBA01501 and 2013CBA01504), the National Key Scientific Instrument and Equipment Development Project of China (Grant No. 2012YQ120047), Chinese Academy of Science Key Program, the National Natural Science of China (Grant Nos. 11135012 and 11375262), and the Project of Shandong Province Higher Educational Science and Technology Program, China (Grant No. J11LA52).

  5. Crater geometry characterization of Al targets irradiated by single pulse and pulse trains of Nd:YAG laser in ambient air and water

    High intensities laser pulses are capable to generate a crater when irradiating metal targets. In such condition, after each irradiation significant ablation occurs on the target surface and as a result a crater is formed. The crater characterization is very important specifically for some applications such as micromachining. In this paper, the crater formation in metal targets was studied experimentally. The planar aluminum 5052 targets were irradiated by frequency doubled (532 nm), Q-switched Nd:YAG (∼6 ns) laser beam in ambient air and distilled water. A crater was produced after each irradiation and it was characterized by an optical microscope. Different laser intensities as well as pulse trains were applied for crater formation. The effects of laser characteristics in crater geometry were examined. The depth of the craters was measured by optical microscope and the diameter (width) was characterized by processing of the crater image. The results were explained in terms of ablation threshold and plasma shielding. The results show that the crater geometry extremely depends on the laser pulse intensity, the number of laser pulses, and ambient.

  6. Optimal Control of Laser-Plasma Instabilities Using Spike Trains of Uneven Duration and Delay: STUD Pulses

    Afeyan, Bedros

    2013-01-01

    Adaptive methods of laser irradiation of plasmas are proposed consisting of deterministic, `on-off' amplitude modulations in time, and intermittently changing speckle-patterns. These laser pulses consist of a series of picosecond time-scale spikes in a spike train of uneven duration and delay (STUD pulses), in contrast to hydrodynamic-time-scale modulated, multi-nanosecond pulses for laser fusion. Properly designed STUD pulses minimize backscatter and tame any absorptive parametric instability for a given set of plasma conditions, by adjusting the modulation periods, duty cycles and spatial hot-spot-distribution scrambling-rates of the spikes. Traditional methods of beam conditioning are subsumed or surpassed by STUD pulses. In addition, STUD pulses allow an advance in the control of instabilities driven by spatially overlapped laser beams by allowing the spikes of crossing beams to be temporally staggered. When the intensity peaks of one fall within the nulls of its crossing beam, it allows an on-off switch ...

  7. Optical limiting and dynamical two-photon absorption of porphyrin with ruthenium outlying complexes for a picosecond pulse train

    Zhang, Yu-Jin; Sun, Yu-Ping; Wang, Chuan-Kui

    2016-01-01

    Propagation and nonlinear optical absorption of a picosecond pulse train in strong reverse saturable absorption (RSA) materials (free-based tetrapyridyl porphyrin H2TPyP with ruthenium (Ru) outlying complexes) are investigated by solving coupled rate equations and field intensity equation. Influence of outlying Ru groups on optical limiting (OL) properties is studied. Propagation of the front subpulses is mainly affected by linear transition between the ground state and the first excited singlet state, while intensity of the latter subpulses is attenuated by the excited state absorption (ESA). These two different absorption mechanisms result in asymmetric distribution of the transmitted pulse. It is shown that effective population transfer time from the ground state to the lowest triplet state and RSA play important roles in the OL performance and pulse shaping. Moreover, our results indicate that the porphyrins studied are ideal optical limiters because of their large ESA cross section and long lifetime of the lowest triplet state. Compounds with the presence of Ru group possess preferable power limiting ability. Ligand group attached to Ru also influences the nonlinear optical absorption of compounds. Special attention has been paid on dynamical two-photon absorption (TPA) cross section which depends crucially on the duration of the subpulse as well as time interval between subpulses. The present study provides a way to modulate nonlinear optical absorption properties of the medium by changing parameters of the pulse train.

  8. Optimal control of laser plasma instabilities using Spike Trains of Uneven Duration and Delay (STUD pulses) for ICF and IFE

    An adaptive method of controlling parametric instabilities in laser produced plasmas is proposed. It involves fast temporal modulation of a laser pulse on the fastest instability's amplification time scale, adapting to changing and unknown plasma conditions. These pulses are comprised of on and off sequences having at least one or two orders of magnitude contrast between them. Such laser illumination profiles are called STUD pulses for Spike Trains of Uneven Duration and Delay. The STUD pulse program includes scrambling the speckle patterns spatially in between the laser spikes. The off times allow damping of driven waves. The scrambling of the hot spots allows tens of damping times to elapse before hot spot locations experience recurring high intensity spikes. Damping in the meantime will have healed the scars of past growth. Another unique feature of STUD pulses on crossing beams is that their temporal profiles can be interlaced or staggered, and their interactions thus controlled with an on-off switch and a dimmer. (authors)

  9. Measurement of cardiac output during exercise in healthy, trained humans using lithium dilution and pulse contour analysis

    The aim of this study was to evaluate the use of pulse contour analysis calibrated with lithium dilution in a single device (LiDCO™) for measurement of cardiac output (.Q) during exercise in healthy volunteers. We sought to; (a) compare pulse contour analysis (PulseCO) and lithium indicator dilution (LiDCO) for the measurement of .Q during exercise, and (b) assess the requirement for recalibration of PulseCO with LiDCO during exercise. Ten trained males performed multi-stage cycling exercise at intensities below and above ventilatory threshold before constant load maximal exercise to exhaustion. Uncalibrated PulseCO .Q (.Qraw) was compared to that calibrated with lithium dilution at baseline (.Qbaseline), during submaximal exercise below (.Qlow) and above (.Qhigh) ventilatory threshold, and at each exercise stage individually (.Qexercise). There was a significant difference between .Qbaseline and all other calibration methods during exercise, but not at rest. No significant differences were observed between other methods. Closest agreement with .Qexercise was observed for .Qhigh (bias ± limits of agreement: 4.8 ± 30.0%). The difference between .Qexercise and both .Qlow and .Qraw was characterized by low bias (4–7%) and wide limits of agreement (>±40%). Calibration of pulse contour analysis with lithium dilution prior to exercise leads to a systematic overestimation of exercising cardiac output. A single calibration performed during exercise above the ventilatory threshold provided acceptable limits of agreement with an approach incorporating multiple calibrations throughout exercise. Pulse contour analysis may be used for .Q measurement during exercise providing the system is calibrated during exercise. (paper)

  10. All-optical, transform-limited and high mark-space-ratio soliton pulse train generation using both CDPF ad NOLM

    Yujun, Qian; Povlsen, Jørn Hedegård; Varming, Poul

    1999-01-01

    Soliton pulse generation from optical beat signal by both CDPF andNOLM is proposed. A transform-limited soliton train with mark-space-ratio(MSR) higher than 1:40 can be obtained at multiples of 10GHz.......Soliton pulse generation from optical beat signal by both CDPF andNOLM is proposed. A transform-limited soliton train with mark-space-ratio(MSR) higher than 1:40 can be obtained at multiples of 10GHz....

  11. A NEW TECHNIQUE OF MEASURING LOW‐POWER PICOSECOND OPTICAL PULSE TRAINS

    Muñoz Zurita, Ana Luz; Shcherbakov, Alexandre S.; Campos Acosta, Joaquín; Gómez Jiménez, Ramón

    2009-01-01

    We present a theoretic approach to the characterization of low‐power bright ultrashort optical pulses with an internal frequency modulation simultaneously in both time and frequency domains. The analysis and computer simulations are applied to studying the capability of Wigner distribution to characterize solitary pulses in practically important case of the sech‐pulses. Then, the simplest two‐beam scanning Michelson interferometer is selected for shaping the field‐strength auto‐correlation fu...

  12. Theory of Pulse Train Amplification Without Patterning Effects in Quantum Dot Semiconductor Optical Amplifiers

    Uskov, Alexander V.; Berg, Tommy Winther; Mørk, Jesper

    2004-01-01

    A theory for pulse amplification and saturation in quantum dot (QD) semiconductor optical amplifiers (SOAs) is developed. In particular, the maximum bit rate at which a data stream of pulses can be amplified without significant patterning effects is investigated. Simple expressions are derived that...

  13. Comparison of RABITT and FROG measurements in the temporal characterization of attosecond pulse trains

    Kim, Kyung Taec; Park, Mi Na; Imran, Tayyab; Umesh, G; Nam, Chang Hee

    2007-01-01

    The attosecond high harmonic pulses obtained from a long Ar-filled gas cell were characterized by two techniques - the reconstruction of attosecond beating by interference of two-photon transition (RABITT) and frequency-resolved optical gating (FROG) methods. The pulse durations obtained by RABITT and FROG methods agreed within 10 %.

  14. Temporal Shaping of High Peak Power Pulse Trains from a Burst-Mode Laser System

    Jörg Körner

    2015-12-01

    Full Text Available It has been shown in the past that pulsed laser systems operating in the so-called “burst mode” are a beneficial approach to generate high peak power laser pulses at high repetition rates suitable for various applications. So far, most high-energy burst-mode laser systems put great effort into generating a homogeneous energy distribution across the burst duration, e.g., by shaping the pump pulse. In this work, we present a new shaping technique, which is able to produce arbitrary energy distributions within the burst by pre-shaping the seed pulse burst with a Pockels cell. Furthermore, this technique allows for the precompensation of any static modulations across the burst, which may be introduced during the subsequent amplification process. Therefore, a pulse burst with a uniform energy distribution can also be generated. The method is tested with an ultra-short pulse burst mode laser amplifier system producing bursts of a 1 ms duration with a pulse repetition rate of 1 MHz and a maximum output power of 800 W during the burst. Furthermore, a method to predict the influence of the amplifier on a non-uniformly shaped burst is presented and successfully tested to produce a pre-defined pulse shape after amplification.

  15. A bright attosecond x-ray pulse train generation in a double-laser-driven cone target

    Hu, Li-Xiang; Yu, Tong-Pu; Shao, Fu-Qiu; Luo, Wen; Yin, Yan

    2016-06-01

    By using full three-dimensional particle-in-cell and Monte Carlo simulations, we investigate the generation of a high-brightness attosecond x-ray pulse train in a double-laser-driven cone target. The scheme makes use of two lasers: the first high-intensity laser with a laser peak intensity 1.37 × 1020 W/cm2 irradiates the cone and produces overdense attosecond electron bunches; the second counterpropagating weakly relativistic laser with a laser peak intensity 4.932 × 1017 W/cm2 interacts with the produced electron bunches and a bright x-ray pulse train is generated by Thomson backscattering of the second laser off the attosecond electron bunches. It is shown that the photon flux rises by 5 times using the cone target as compared with a normal channel. Meanwhile, the x-ray peak brightness increases significantly from 1.4 × 1021/(s mm2 mrad2 0.1 keV) to 6.0 × 1021/(s mm2 mrad2 0.1 keV), which is much higher than that of the Thomson x-ray source generated from traditional accelerators. We also discuss the influence of the laser and target parameters on the x-ray pulse properties. This compact bright x-ray source may have diverse applications, e.g., the study of electric dynamics and harmonics emission in the atomic scale.

  16. HyperCEST detection of cucurbit[6]uril in whole blood using an ultrashort saturation Pre-pulse train.

    Hane, Francis T; Smylie, Peter S; Li, Tao; Ruberto, Julia; Dowhos, Krista; Ball, Iain; Tomanek, Boguslaw; DeBoef, Brenton; Albert, Mitchell S

    2016-07-01

    Xenon based biosensors have the potential to detect and localize biomarkers associated with a wide variety of diseases. The development and nuclear magnetic resonance (NMR) characterization of cage molecules which encapsulate hyperpolarized xenon is imperative for the development of these xenon biosensors. We acquired (129) Xe NMR spectra, and magnetic resonance images and a HyperCEST saturation map of cucurbit[6]uril (CB6) in whole bovine blood. We observed a mean HyperCEST depletion of 84% (n = 5) at a concentration of 5 mM and 74% at 2.5 mM. Additionally, we collected these data using a pulsed HyperCEST saturation pre-pulse train with a SAR of 0.025 W/kg which will minimize any potential RF heating in animal or human tissue. Copyright © 2016 John Wiley & Sons, Ltd. PMID:27071809

  17. Laser breakdown with millijoule trains of picosecond pulses transmitted through a hollow-core photonic-crystal fibre

    Sequences of picosecond pulses with a total energy in the pulse train of about 1 mJ are transmitted through a hollow-core photonic-crystal fibre with a core diameter of approximately 14 μm. The fluence of laser radiation coupled into the core of the fibre under these conditions exceeds the breakdown threshold of fused silica by nearly an order of magnitude. The laser beam coming out of the fibre is then focused to produce a breakdown on a solid surface. Parameters of laser radiation were chosen in such a way as to avoid effects related to the excitation of higher order waveguide modes and ionization of the gas filling the fibre in order to provide the possibility to focus the output beam into a spot with a minimum diameter, thus ensuring the maximum spatial resolution and the maximum power density in the focal spot

  18. Temporal Shaping of High Peak Power Pulse Trains from a Burst-Mode Laser System

    Jörg Körner; Jürgen Reiter; Joachim Hein; Kaluza, Malte C.

    2015-01-01

    It has been shown in the past that pulsed laser systems operating in the so-called “burst mode” are a beneficial approach to generate high peak power laser pulses at high repetition rates suitable for various applications. So far, most high-energy burst-mode laser systems put great effort into generating a homogeneous energy distribution across the burst duration, e.g., by shaping the pump pulse. In this work, we present a new shaping technique, which is able to produce arbitrary energy distr...

  19. The density broadening in a sodium F=2 condensate detected by a pulse train

    Jianing Han

    2011-09-01

    Full Text Available The dipole-blockaded sodium clock transition has been detected by high resolution microwave spectroscopy, the multiple-pulse spectroscopy. This spectroscopic technique has been first used to detect the density broadening and shifting in a Sodium Bose Einstein Condensate (BEC by probing the sodium clock-transition. Moreover, by narrowing the pulse-width of the pulses, some of the broadening mechanisms can be partially reduced. The results reported here are essential steps toward the ground-state quantum computing, few-body spectroscopy, spin squeezing and quantum metrology.

  20. Attosecond timing jitter pulse trains from semiconductor saturable absorber mode-locked Cr:LiSAF lasers

    Sennaroğlu, Alphan; Li, Duo; Demirbaş, Ümit; Benedick, Andrew; Fujimoto, James G.; Kaertner, Franz X.

    2012-01-01

    The timing jitter of optical pulse trains from diode-pumped, semiconductor saturable absorber mode-locked femtosecond Cr:LiSAF lasers is characterized by a single-crystal balanced optical cross-correlator with an equivalent sensitivity in phase noise of -235 dBc/Hz. The RMS timing jitter is 30 attoseconds integrated from 10 kHz to 50 MHz, the Nyquist frequency of the 100 MHz repetition rate oscillator. The AM-to-PM conversion induced excess phase noise is calculated and compared with experime...

  1. Wave fronts, pulses and wave trains in photoexcited superlattices behaving as excitable or oscillatory media

    Arana, J. I.; Bonilla, L. L.; Grahn, H. T.

    2011-01-01

    Undoped and strongly photoexcited semiconductor superlattices with field-dependent recombination behave as excitable or oscillatory media with spatially discrete nonlinear convection and diffusion. Infinitely long, dc-current-biased superlattices behaving as excitable media exhibit wave fronts with increasing or decreasing profiles, whose velocities can be calculated by means of asymptotic methods. These superlattices can also support pulses of the electric field. Pulses moving downstream wit...

  2. The soft-photon approximation in infrared-laser-assisted atomic ionization by extreme-ultraviolet attosecond-pulse trains

    We use the soft-photon approximation, formulated for finite pulses, to investigate the effects of the dressing pulse duration and intensity on simulated attosecond pump–probe experiments employing trains of attosecond extreme-ultraviolet pulses in conjunction with an IR probe pulse. We illustrate the validity of the approximation by comparing the modelled photoelectron distributions for the helium atom, in the photon energy region close to the N = 2 threshold, to the results from the direct solution of the time-dependent Schrödinger equation for two active electrons. Even in the presence of autoionizing states, the model accurately reproduces most of the background features of the ab initio photoelectron spectrum in the 1s channel. A splitting of the photoelectron harmonic signal along the polarization axis, in particular, is attributed to the finite duration of the probe pulse. Furthermore, we study the dependence of the sideband integrated signal on the pump–probe time delay for increasing IR field strengths. Starting at IR intensities of the order of  ∼ 1 TW cm−2, overtones in the sideband oscillations due to the exchange of three or more IR photons start to appear. We derive an analytical expression in the frequency-comb limit of the soft-photon model for the amplitude of all the sideband frequency components and show that these amplitudes oscillate as a function of the intensity of the IR field. In particular, we predict that the amplitude of the fundamental component with frequency 2ωIR, on which the rabitt optical reconstruction technique is based, changes sign periodically. (paper)

  3. Effects of picosecond terawatt UV laser beam filamentation and a repetitive pulse train on creation of prolonged plasma channels in atmospheric air

    Amplitude-modulated UV laser pulse of up to 30 J energy was produced at hybrid Ti:Sapphire/KrF GARPUN-MTW laser facility when a preliminary amplified train of short pulses was injected into unstable resonator cavity of the main e-beam-pumped KrF amplifier. The combined radiation consisted of regeneratively amplified picosecond pulses with subTW peak power overlapped with 100-ns pulse of a free-running lasing. The advantages of combined radiation for production of long-lived prolonged plasma channels in air and HV discharge triggering were demonstrated: photocurrent sustained by modulated pulse is two orders of magnitude higher and HV breakdown distance is twice longer than for a smooth UV pulse. It was found that in contrast to IR radiation multiple filamentation of high-power UV laser beam does not produce extended nonlinear focusing of UV radiation

  4. Shaping SHF train of optical picosecond pulses for generating a photoemission in SHF guns

    The paper analyses a technique of generating optical picosecond pulses (OPP) through laser beam deflection. The OPP generator consists of a laser, deflection system, optical system and amplifier-converter. The technique of OPP generation through laser beam deflection can be successfully used for triggering photoemission in SHF beams. 8 refs., 2 figs

  5. Generation of 10 GHz, 1.9 ps optical pulse train using semiconductor optical amplifier and silica-based highly nonlinear fiber

    We propose a simple approach to generate a high quality 10 GHz 1.9 ps optical pulse train using a semiconductor optical amplifier and silica-based highly nonlinear fiber. An optical pulse generator based on our proposed scheme is easy to set up with commercially available optical components. A 10 GHz, 1.9 ps optical pulse train is obtained with timing jitter as low as 60 fs over the frequency range 10 Hz–1 MHz. With a wavelength tunable CW laser, a wide wavelength tunable span can be achieved over the entire C band. The proposed optical pulse generator also can operate at different repetition rates from 3 to 10 GHz

  6. Generation of pulse trains in nonlinear optical fibers through the generalized complex Ginzburg-Landau equation.

    Latchio Tiofack, Camus G; Mohamadou, Alidou; Kofané, Timoléon C; Moubissi, Alain B

    2009-12-01

    We consider a higher-order complex Ginzburg-Landau equation, with the fourth-order dispersion and cubic-quintic nonlinear terms, which can describe the propagation of an ultrashort subpicosecond or femtosecond optical pulse in an optical fiber system. We investigate the modulational instability (MI) of continuous wave solution of this equation. Several types of modulational instability gains are shown to exist in both the anomalous and normal dispersion regimes. We find that depending on the sign of the fourth-order dispersion coefficient, the MI appears for normal and anomalous dispersion regime. Simulations of the full system demonstrate that the development of the MI leads to establishment of a regular or chaotic array of pulses, a chain of well-separated peaks with continuously growing or decaying amplitudes depending on the sign of the loss/gain coefficient and higher-order dispersions terms. Comparison of the calculations with reported numerical results shows a satisfactory agreement. PMID:20365291

  7. Laser-induced periodic surface structures on 6H-SiC single crystals using temporally delayed femtosecond laser double-pulse trains

    Song, Juan; Tao, Wenjun; Song, Hui; Gong, Min; Ma, Guohong; Dai, Ye; Zhao, Quanzhong; Qiu, Jianrong

    2016-04-01

    In this paper, a time-delay-adjustable double-pulse train with 800-nm wavelength, 200-fs pulse duration and a repetition rate of 1 kHz, produced by a collinear two-beam optical system like a Mach-Zehnder interferometer, was employed for irradiation of 6H-SiC crystal. The dependence of the induced structures on time delay of double-pulse train for parallel-polarization configuration was studied. The results show that as the time delay of collinear parallel-polarization dual-pulse train increased, the induced near-subwavelength ripples (NSWRs) turn from irregular rippled pattern to regularly periodic pattern and have their grooves much deepened. The characteristics timescale for this transition is about 6.24 ps. Besides, the areas of NSWR were found to decay exponentially for time delay from 0 to 1.24 ps and then slowly increase for time delay from 1.24 to 14.24 ps. Analysis shows that multiphoton ionization effect, grating-assisted surface plasmon coupling effect, and timely intervene of second pulse in a certain physical stage experienced by 6H-SiC excited upon first pulse irradiation may contribute to the transition of morphology details.

  8. Cavity-enhanced single frequency synthesis via DFG of mode-locked pulse trains

    Ferrari, Gabriele; Carusotto, Iacopo

    2005-01-01

    We show how to synthesize a CW, single-frequency optical field from the frequency-dispersed, pulsed field of a mode-locked laser. This process, which relies on difference frequency generation in an optical cavity, is efficient and can be considered as an optical rectification. Quantitative estimates for the output power and amplitude noise properties of a realistic system are given. Possible applications to optical frequency synthesis and optical metrology are envisaged.

  9. Theoretical model of unipolar and bipolar trains of magnetic field pulses preceding lightning discharges

    Kašpar, Petr; Santolík, Ondřej; Kolmašová, Ivana

    Prague: International Union of Geodesy and Geophysics, 2015. A11p-142. [Earth and Environmental Sciences for Future Generations. General Assembly of International Union of Geodesy and Geophysics /26./. 22.06.2015-02.07.2015, Prague] Institutional support: RVO:68378289 Keywords : magnetic field pulses Subject RIV: DG - Athmosphere Sciences, Meteorology http://www.iugg2015prague.com/abstractcd/data/HtmlApp/main.html#

  10. Safety training and safe operating procedures written for PBFA [Particle Beam Fusion Accelerator] II and applicable to other pulsed power facilities

    To ensure that work in advancing pulsed power technology is performed with an acceptably low risk, pulsed power research facilities at Sandia National Laboratories must satisfy general safety guidelines established by the Department of Energy, policies and formats of the Environment, Safety, and Health (ES and H) Department, and detailed procedures formulated by the Pulsed Power Sciences Directorate. The approach to safety training and to writing safe operating procedures, and the procedures presented here are specific to the Particle Beam Fusion Accelerator II (PBFA II) Facility but are applicable as guidelines to other research and development facilities which have similar hazards

  11. Safety training and safe operating procedures written for PBFA (Particle Beam Fusion Accelerator) II and applicable to other pulsed power facilities

    Donovan, G.L.; Goldstein, S.A.

    1986-12-01

    To ensure that work in advancing pulsed power technology is performed with an acceptably low risk, pulsed power research facilities at Sandia National Laboratories must satisfy general safety guidelines established by the Department of Energy, policies and formats of the Environment, Safety, and Health (ES and H) Department, and detailed procedures formulated by the Pulsed Power Sciences Directorate. The approach to safety training and to writing safe operating procedures, and the procedures presented here are specific to the Particle Beam Fusion Accelerator II (PBFA II) Facility but are applicable as guidelines to other research and development facilities which have similar hazards.

  12. IMPACT OF SHORT TERM TRAINING OF ANULOM VILOM PRANAYAM ON BLOOD PRESSURE AND PULSE RATE IN HEALTHY VOLUNTEERS

    Dandekar Pradnya Deepak

    2013-04-01

    Full Text Available In present scenario, Yoga is becoming most popular science due to its positive effect on health. To achieve preventive, curative and rehabilitative aspects of health, Yoga draws the attention of large group of people. Prana (energy and Ayam (to expand or control form the word Pranayam. Pranayam is a technique to control or expand the energy in body. Practice of Pranayam has been known to modulate cardiac autonomic status with an improvement in cardio-respiratory functions. Keeping this in view, the present study designed to determine whether Anulom- Vilom Pranayam followed by Shawasan has immediate effect on pulse rate, systolic and diastolic blood pressure. Thirty normal healthy subjects aged between 17-20 years, volunteered for this study. All the selected physiological parameters were measured before and after performing ‘Anulom – Vilom Pranayama’ followed by Shawasan for four weeks. Experimental group showed a significant decline in Systolic Blood Pressure (p<0.021. On other hand there was no significant change in Diastolic Blood Pressure and pulse rate, though it showed slight decrease. Our study indicates that, short-term training of ‘Anulom- Vilom Pranayam ‘shows significant decrease in Systolic Blood Pressure. Control of breathing process to make it deep and prolong by doing alternate nostril breathing with slow and rhythmic manner brings about balance in autonomous nervous system. In addition, practice of Anulom- Vilom pranayama for short-term duration could get better parasympathetic control over the heart.

  13. Induced soliton ejection from a continuous-wave source waveguided by an optical pulse soliton train

    It has been established for some time that a high-power pump can trap a probe beam of lower intensity that is simultaneously propagating in a Kerr-type optical medium, inducing a focusing of the probe with the emergence of modes displaying solitonic properties. To understand the mechanism by which such self-sustained modes are generated, and mainly the changes in probe spectrum induced by the cross-phase-modulation effect for a harmonic probe trapped by a multiplex of temporal pulses, a linear equation (for the probe) and a nonlinear Schrödinger equation (for the pump) both coupled by a cross-phase-modulation term, are considered simultaneously. In general the set of coupled probe–pump equations is not exactly tractable at any arbitrary value of the ratio of the cross-phase to the self-phase-modulation strengths. However, for certain values of this ratio, the probe modulation wavevector develops into |n, l) quantum states involving 2n + 1 soliton-shaped eigenfunctions for which the spectral properties can be characterized unambiguously. Solutions of the probe equation give evidence that the competition between the self-phase and cross-phase-modulations leads to a broadband spectrum, with the possibility of a quasi-continuum of soliton modes when the cross-phase-modulation coupling is strong enough

  14. Exploring intense attosecond pulses

    Charalambidis, D.; Tzallas, P.; Benis, E. P.; Skantzakis, E.; Maravelias, G.; Nikolopoulos, L. A. A.; Peralta Conde, A.; Tsakiris, G. D.

    2008-02-01

    After introducing the importance of non-linear processes in the extreme-ultra-violet (XUV) spectral regime to the attosecond (asec) pulse metrology and time domain applications, we present two successfully implemented techniques with excellent prospects in generating intense asec pulse trains and isolated asec pulses, respectively. For the generation of pulse trains two-color harmonic generation is exploited. The interferometric polarization gating technique appropriate for the generation of intense isolated asec pulses is discussed and compared to other relevant approaches.

  15. Control of Stimulated Raman Scattering in the Strongly Nonlinear and Kinetic Regime Using Spike Trains of Uneven Duration and Delay: STUD Pulses

    Albright, B J; Afeyan, B

    2013-01-01

    Stimulated Raman scattering (SRS) in its strongly nonlinear, kinetic regime is controlled by a technique of deterministic, strong temporal modulation and spatial scrambling of laser speckle patterns, called Spike Trains of Uneven Duration and Delay (STUD pulses) [B. Afeyan and S. H\\"uller, Phys. Rev. Lett. (submitted)]. Kinetic simulations show that use of STUD pulses may decrease SRS reflectivity by more than an order of magnitude over random-phase-plate (RPP) or induced-spatial-incoherence (ISI) beams of the same average intensity and comparable bandwidth.

  16. Building Of Training Program Of Non-Destructive Testing For Concrete Structures (Part 1: Radiographic testing; Ultrasonic pulse velocity measurement; Nuclear moisture-density gauge)

    Non-destructive testing methods (NDT) have been identified as a strong candidate for remote sensing of concrete structures over recent years. This has accelerated the powerful development of the NDT techniques in Vietnam. Hence, there is an urgent need to promote the awareness of NDT methods which could give an improved estimate of the condition concrete. Building of training program of non-destructive testing for concrete structures is a necessary duty, in aiming to build a unified training program, possibly satisfying the requirements on training as well as researching. Under the framework of the basic VAEC project (CS/07/02-03), a training program for the first 03 NDT methods: 1. Radiographic testing; 2. Ultrasonic pulse velocity measurement; 3. Nuclear moisture- density gauge was prepared. The main products of this project include: 1. Set out 03 training notes for 03 methods; 2. Set out the practical exercises to train for 03 methods; 3. Editing a set of examination questions in aiming to familiarize with various questions in 03 trained methods; 4. Fabricating practical test specimens to demonstrate for 03 techniques. (author)

  17. THE EFFECT OF REGULAR EXERCISE TRAINING DURING PREGNANCY ON POSTPARTUM BRACHIAL-ANKLE PULSE WAVE VELOCITY, A MEASURE OF ARTERIAL STIFFNESS

    Ikuno Kawabata; Akihito Nakai; Atsuko Sekiguchi; Yuko Inoue; Toshiyuki Takeshita

    2012-01-01

    The aim of our study was to use brachial-ankle pulse wave velocity (baPWV) measurements to noninvasively assess the effect of exercise training on arterial stiffness in normal pregnant women. Arterial stiffness was assessed at the beginning of the early second trimester of pregnancy and 1 month after delivery in 17 women with normal singleton pregnancies who exercised regularly throughout pregnancy: 81 matched controls were used for comparison. No significant differences were observed in baPW...

  18. Attosecond control of orbital parity mix interferences and the relative phase of even and odd harmonics in an attosecond pulse train.

    Laurent, G; Cao, W; Li, H; Wang, Z; Ben-Itzhak, I; Cocke, C L

    2012-08-24

    We experimentally demonstrate that atomic orbital parity mix interferences can be temporally controlled on an attosecond time scale. Electron wave packets are formed by ionizing argon gas with a comb of odd and even high-order harmonics, in the presence of a weak infrared field. Consequently, a mix of energy-degenerate even and odd parity states is fed in the continuum by one- and two-photon transitions. These interfere, leading to an asymmetric electron emission along the polarization vector. The direction of the emission can be controlled by varying the time delay between the comb and infrared field pulses. We show that such asymmetric emission provides information on the relative phase of consecutive odd and even order harmonics in the attosecond pulse train. PMID:23002742

  19. An atmospheric pressure plasma source driven by a train of monopolar high voltage pulses superimposed to a dc voltage

    Stoican, O.S.

    2011-01-01

    Abstract An atmospheric pressure plasma source supplied by an electrical circuit consisting of two voltage sources in parallel connection is reported. One of them is a low-power self-oscillating flyback converter which produces negative voltage pulses with an amplitude of several kilovolts. The high voltage pulses are necessary to ignite an electrical discharge between the electrodes at atmospheric pressure. An additional dc source delivering several hundreds of volts at a few hund...

  20. Towards attosecond XUV pulses

    We are constructing a system for attosecond pulse generation via high-order harmonics generation in noble gases. To obtain a single attosecond pulse rather than a pulse train, we employ the regime of a few-cycle-pulse-driven harmonics generation. To achieve it, we are developing an external pulse compressor down to 7 - 10 fs using a gas-filled hollow fiber followed by chirped mirrors. We also proposed the method of high-energy attosecond pulse generation using high-order harmonics generated during the interaction of a relativistic-irradiance laser pulse with a thin foil. (author)

  1. Methods of Optimal Control of Laser-Plasma Instabilities Using Spike Trains of Uneven Duration and Delay (STUD Pulses)

    Afeyan, Bedros

    2013-10-01

    We have recently introduced and extensively studied a new adaptive method of LPI control. It promises to extend the effectiveness of laser as inertial fusion drivers by allowing active control of stimulated Raman and Brillouin scattering and crossed beam energy transfer. It breaks multi-nanosecond pulses into a series of picosecond (ps) time scale spikes with comparable gaps in between. The height and width of each spike as well as their separations are optimization parameters. In addition, the spatial speckle patterns are changed after a number of successive spikes as needed (from every spike to never). The combination of these parameters allows the taming of parametric instabilities to conform to any desired reduced reflectivity profile, within the bounds of the performance limitations of the lasers. Instead of pulse shaping on hydrodynamical time scales, far faster (from 1 ps to 10 ps) modulations of the laser profile will be needed to implement the STUD pulse program for full LPI control. We will show theoretical and computational evidence for the effectiveness of the STUD pulse program to control LPI. The physics of why STUD pulses work and how optimization can be implemented efficiently using statistical nonlinear optical models and techniques will be explained. We will also discuss a novel diagnostic system employing STUD pulses that will allow the boosted measurement of velocity distribution function slopes on a ps time scale in the small crossing volume of a pump and a probe beam. Various regimes from weak to strong coupling and weak to strong damping will be treated. Novel pulse modulation schemes and diagnostic tools based on time-lenses used in both microscope and telescope modes will be suggested for the execution of the STUD pule program. Work Supported by the DOE NNSA-OFES Joint Program on HEDLP and DOE OFES SBIR Phase I Grants.

  2. Pulse!!: a model for research and development of virtual-reality learning in military medical education and training.

    Dunne, James R; McDonald, Claudia L

    2010-07-01

    Pulse!! The Virtual Clinical Learning Lab at Texas A&M University-Corpus Christi, in collaboration with the United States Navy, has developed a model for research and technological development that they believe is an essential element in the future of military and civilian medical education. The Pulse!! project models a strategy for providing cross-disciplinary expertise and resources to educational, governmental, and business entities challenged with meeting looming health care crises. It includes a three-dimensional virtual learning platform that provides unlimited, repeatable, immersive clinical experiences without risk to patients, and is available anywhere there is a computer. Pulse!! utilizes expertise in the fields of medicine, medical education, computer science, software engineering, physics, computer animation, art, and architecture. Lab scientists collaborate with the commercial virtual-reality simulation industry to produce research-based learning platforms based on cutting-edge computer technology. PMID:23634475

  3. Pulse plating

    Hansal, Wolfgang E G; Green, Todd; Leisner, Peter; Reichenbach, Andreas

    2012-01-01

    The electrodeposition of metals using pulsed current has achieved practical importance in recent years. Although it has long been known that changes in potential, with or without polarity reversal, can significantly affect the deposition process, the practical application of this has been slow to be adopted. This can largely be explained in terms of the complex relationship between the current regime and its effect on the electrodeposition process. In order to harness these effects, an understanding of the anodic and cathodic electrochemical processes is necessary, together with the effects of polarity reversal and the rate of such reversals. In this new monograph, the basics of metal electrodeposition from solution are laid out in great detail in seven distinct chapters. With this knowledge, the reader is able to predict how a given pulse train profile can be adopted to achieve a desired outcome. Equally important is the choice of a suitable rectifier and the ancillary control circuits to enable pulse platin...

  4. Pulse measurement apparatus and method

    Marciante, John R.; Donaldson, William R.; Roides, Richard G.

    2011-10-25

    An embodiment of the invention is directed to a pulse measuring system that measures a characteristic of an input pulse under test, particularly the pulse shape of a single-shot, nano-second duration, high shape-contrast optical or electrical pulse. An exemplary system includes a multi-stage, passive pulse replicator, wherein each successive stage introduces a fixed time delay to the input pulse under test, a repetitively-gated electronic sampling apparatus that acquires the pulse train including an entire waveform of each replica pulse, a processor that temporally aligns the replicated pulses, and an averager that temporally averages the replicated pulses to generate the pulse shape of the pulse under test. An embodiment of the invention is directed to a method for measuring an optical or an electrical pulse shape. The method includes the steps of passively replicating the pulse under test with a known time delay, temporally stacking the pulses, and temporally averaging the stacked pulses. An embodiment of the invention is directed to a method for increasing the dynamic range of a pulse measurement by a repetitively-gated electronic sampling device having a rated dynamic range capability, beyond the rated dynamic range of the sampling device; e.g., enhancing the dynamic range of an oscilloscope. The embodied technique can improve the SNR from about 300:1 to 1000:1. A dynamic range enhancement of four to seven bits may be achieved.

  5. The coherent artifact in modern pulse measurements

    Ratner, Justin; Wong, Tsz Chun; Bartels, Randy; Trebino, Rick

    2012-01-01

    We simulate multi-shot intensity-and-phase measurements of unstable ultrashort-pulse trains using frequency-resolved-optical-gating (FROG) and spectral phase interferometry for direct electric-field reconstruction (SPIDER). Both techniques fail to reveal the pulse structure. FROG yields the average pulse duration and suggests the instability by exhibiting disagreement between measured and retrieved traces. SPIDER under-estimates the average pulse duration but retrieves the correct average pulse spectral phase. An analytical calculation confirms this behavior.

  6. Digital Communication Using Chaotic Pulse Generators

    Rulkov, N F; Tsimring, L S; Volkovskii, A R; Abarbanel, Henry D I; Larson, L; Yao, K

    1999-01-01

    Utilization of chaotic signals for covert communications remains a very promising practical application. Multiple studies indicated that the major shortcoming of recently proposed chaos-based communication schemes is their susceptibility to noise and distortions in communication channels. In this talk we discuss a new approach to communication with chaotic signals, which demonstrates good performance in the presence of channel distortions. This communication scheme is based upon chaotic signals in the form of pulse trains where intervals between the pulses are determined by chaotic dynamics of a pulse generator. The pulse train with chaotic interpulse intervals is used as a carrier. Binary information is modulated onto this carrier by the pulse position modulation method, such that each pulse is either left unchanged or delayed by a certain time, depending on whether ``0'' or ``1'' is transmitted. By synchronizing the receiver to the chaotic pulse train we can anticipate the timing of pulses corresponding to ...

  7. Pulse on Pulse

    Schmidt, Ulrik; Carlson, Merete

    2012-01-01

    of the visitor’s beating heart to the blink of a fragile light bulb, thereby transforming each light bulb into a register of individual life. But at the same time the blinking light bulbs together produce a chaotically flickering light environment composed by various layers of repetitive rhythms, a vibrant...... and pulsating ‘room’. Hence, the visitors in Pulse Room are invited into a complex scenario that continuously oscillates between various aspects of signification (the light bulbs representing individual lives; the pulse itself as the symbolic ‘rhythm of life’) and instants of pure material processuality...... (flickering light bulbs; polyrhythmic layers). Taking our point of departure in a discussion of Gilles Deleuze’s concepts of modulation and signaletic material in relation to electronic media, we examine how the complex orchestration of pulsation between signification and material modulation produces...

  8. The coherent artifact in modern pulse measurements

    Ratner, Justin; Steinmeyer, Günter; Wong, Tsz Chun; Bartels, Randy; Trebino, Rick

    2012-01-01

    We simulate multi-shot intensity-and-phase measurements of unstable ultrashort-pulse trains using frequency-resolved-optical-gating (FROG) and spectral phase interferometry for direct electric-field reconstruction (SPIDER). Both techniques fail to reveal the pulse structure. FROG yields the average pulse duration and suggests the instability by exhibiting disagreement between measured and retrieved traces. SPIDER under-estimates the average pulse duration but retrieves the correct average pul...

  9. Nonlinear polarization rotation-induced pulse shaping in a stretched-pulse ytterbium-doped fiber laser

    Bai, Dong-Bi; Li, Wen-Xue; Yang, Kang-Wen; Shen, Xu-Ling; Chen, Xiu-Liang; Zeng, He-Ping

    2014-10-01

    We report on controllable pulse shaping in a Yb-doped stretched-pulse fiber laser followed by a high-power chirped pulse amplifier. We demonstrate that the pulses after an extra-cavity grating pair change their intensity profile from Lorentz to Gaussian and then to sech2 shapes by adjusting the intra-cavity polarization through a quarter-wave plate inside the fiber laser cavity. The laser pulses with different pulse shapes exhibit pulse-to-pulse amplitude fluctuation of ~ 1.02%, while the sech2-shaped pulse train is provided with a more stable free-running repetition rate as a result of the stronger self-phase modulation in the fiber laser cavity than Lorentz- and Gaussian-shaped pulse trains.

  10. Pulse Voltammetry.

    Osteryoung, Janet

    1983-01-01

    Discusses the nature of pulse voltammetry, indicating that its widespread use arises from good sensitivity and detection limits and from ease of application and low cost. Provides analytical and mechanistic applications of the procedure. (JN)

  11. Training safely, Training safety

    Jianjun Wu; An, M.; Jin, Y.; H. Geng

    2014-01-01

    It is the basic requirement of maritime safety education to guarantee the safety of teaching operation while training the crew's occupation safety capability. Marine Training Center of Shanghai Maritime University has undertaken the practical teaching of "marine survival" for many years and come up with the whole safety procedures of training. Based on the requirements of SOLAS convention and regulations of STCW over crew training, this paper introduces the safety allocation, utilization and ...

  12. Noisy homoclinic pulse dynamics

    Eaves, T. S.; Balmforth, Neil J.

    2016-04-01

    The effect of stochastic perturbations on nearly homoclinic pulse trains is considered for three model systems: a Duffing oscillator, the Lorenz-like Shimizu-Morioka model, and a co-dimension-three normal form. Using the Duffing model as an example, it is demonstrated that the main effect of noise does not originate from the neighbourhood of the fixed point, as is commonly assumed, but due to the perturbation of the trajectory outside that region. Singular perturbation theory is used to quantify this noise effect and is applied to construct maps of pulse spacing for the Shimizu-Morioka and normal form models. The dynamics of these stochastic maps is then explored to examine how noise influences the sequence of bifurcations that take place adjacent to homoclinic connections in Lorenz-like and Shilnikov-type flows.

  13. Computationally intelligent pulsed photoacoustics

    In this paper, the application of computational intelligence in pulsed photoacoustics is discussed. Feedforward multilayer perception networks are applied for real-time simultaneous determination of the laser beam spatial profile and vibrational-to-translational relaxation time of the polyatomic molecules in gases. Networks are trained and tested with theoretical data adjusted for a given experimental set-up. Genetic optimization has been used for calculation of the same parameters, fitting the photoacoustic signals with a different number of generations. Observed benefits from the application of computational intelligence in pulsed photoacoustics and advantages over previously developed methods are discussed, such as real-time operation, high precision and the possibility of finding solutions in a wide range of parameters, similar to in experimental conditions. In addition, the applicability for practical uses, such as the real-time in situ measurements of atmospheric pollutants, along with possible further developments of obtained results, is argued. (paper)

  14. Generating long sequences of high-intensity femtosecond pulses

    Bitter, Martin

    2015-01-01

    We present an approach to create pulse sequences extending beyond 150~picoseconds in duration, comprised of $100~\\mu$J femtosecond pulses. A quarter of the pulse train is produced by a high-resolution pulse shaper, which allows full controllability over the timing of each pulse. Two nested Michelson interferometers follow to quadruple the pulse number and the sequence duration. To boost the pulse energy, the long train is sent through a multi-pass Ti:Sapphire amplifier, followed by an external compressor. A periodic sequence of 84~pulses of 120~fs width and an average pulse energy of 107~$\\mu$J, separated by 2~ps, is demonstrated as a proof of principle.

  15. Generating long sequences of high-intensity femtosecond pulses.

    Bitter, M; Milner, V

    2016-02-01

    We present an approach to creating pulse sequences extending beyond 150 ps in duration, comprised of 100 μJ femtosecond pulses. A quarter of the pulse train is produced by a high-resolution pulse shaper, which allows full controllability over the timing of each pulse. Two nested Michelson interferometers follow to quadruple the pulse number and the sequence duration. To boost the pulse energy, the long train is sent through a multipass Ti:sapphire amplifier, followed by an external compressor. A periodic sequence of 84 pulses of 120 fs width and an average pulse energy of 107 μJ, separated by 2 ps, is demonstrated as a proof of principle. PMID:26836087

  16. Laser pulse shaping for high gradient accelerators

    Villa, F.; Anania, M. P.; Bellaveglia, M.; Bisesto, F.; Chiadroni, E.; Cianchi, A.; Curcio, A.; Galletti, M.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Gatti, G.; Moreno, M.; Petrarca, M.; Pompili, R.; Vaccarezza, C.

    2016-09-01

    In many high gradient accelerator schemes, i.e. with plasma or dielectric wakefield induced by particles, many electron pulses are required to drive the acceleration of one of them. Those electron bunches, that generally should have very short duration and low emittance, can be generated in photoinjectors driven by a train of laser pulses coming inside the same RF bucket. We present the system used to shape and characterize the laser pulses used in multibunch operations at Sparc_lab. Our system gives us control over the main parameter useful to produce a train of up to five high brightness bunches with tailored intensity and time distribution.

  17. Xi'an pulsed reactor

    Xi'an Pulsed Reactor (XAPR) Designed and constructed all by China is first research pulsed reactor with versatile applications. It is characterized with inherent safety, versatile application, structure simplicity and convenience for operation. It can be operated not only at stead-state but also at pulse mode as well as square wave mode. The rated power to the reactor under steady-state operation is 2 MW and the reactor is operated under pulsing state, its maximum peak power is about 4200 MW. XAPR is also equipped with many kinds of the experimental and irradiation facilities. The applications are radio-isotopes production, neutron activity analysis, neutron radiograph, monocrystalline silicon irradiation, material irradiation test, nuclear physics, neutron physics and nuclear chemistry studies, teaching and training. The XAPR has went into test operation and application for nearly two years that has shown its advantage and extensiveness

  18. Attosecond pulse shaping using partial phase matching

    We propose a method for programmable shaping of the amplitude and phase of the extreme ultraviolet and x-ray attosecond pulses produced by high-order harmonic generation. It overcomes the bandwidth limitations of existing spectral filters and enables removal of the intrinsic attosecond chirp as well as the synthesis of pulse sequences. It is based on partial phase matching using a longitudinally addressable modulation. Although the method is in principle applicable to any form of partial phase matching, we focus on quasi-phase matching using a counterpropagating pulse train. We present simulations of the production of isolated attosecond pulses at 250 eV, including a 31 as transform-limited pulse, tunably chirped pulses and double pulses. (paper)

  19. Isotope-selective ionization using four-pulse alignment

    We have proposed a laser isotope separation method utilizing molecular alignment and non-resonant multiphoton ionization, and demonstrated isotope-selective ionization of 14N2 and 15N2 isotopomers, using one-pulse alignment. In the present work, we used a train of four identical pulses, instead of one pulse, to obtain the higher selectivity. (author)

  20. Single X-Ray Attosecond Pulse Generation by Using Combined Pulses Irradiating on a United Two-Atom System

    CHEN Ji-Gen; LI Chen; CHI Fang-Ping; YANG Yu-Jun

    2007-01-01

    @@ A scheme of a single x-ray attosecond pulse generation from a two-atom system exposed to the combined laser pulses is proposed. Our numerical results show that a single x-ray attosecond pulse rather than a train one can be produced by modulation of ionization.

  1. Language Training: English Training

    2004-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. Language Training Françoise Benz tel. 73127 language.training@cern.ch General and Professional English Courses The next session will take place: from 1st March to 25 June 2004 (2 weeks break at Easter). These courses are open to all persons working on the Cern site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mr. Liptow: tel. 72957.

  2. Language Training: English Training

    2004-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. LANGUAGE TRAINING Françoise Benz tel. 73127 language.training@cern.ch General and Professional English Courses The next session will take place: from 1st March to 25 June 2004 (2 weeks break at Easter). These courses are open to all persons working on the Cern site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mr. Liptow: tel. 72957.

  3. Changes of blood pressure,pulse rate and respiratory rate in submariners following simulated air-breathing 3-50 m fast buoyancy ascent escape training%模拟3~50 m快速上浮脱险训练潜艇艇员血压、脉率和呼吸频率的变化

    姚健; 顾秀良; 方以群; 张和翔; 陈锐勇; 孟淼; 袁恒荣; 王世锋; 马骏; 王海涛

    2010-01-01

    目的 观察模拟快速上浮脱险训练时潜艇艇员生命指征的变化.方法 分别进行了3、10、30、50 m 4个深度69人次的快速上浮脱险训练,于训练前、训练后即刻及出舱后10 min分别测定艇员的血压、脉率和呼吸频率.结果 训练后即刻艇员的收缩压、舒张压、脉率及呼吸频率与进舱前比较,绝大部分指标有所增加,差异有统计学意义(P<0.01).在出舱后10 min各指标基本恢复正常.结论 模拟快速上浮脱险训练可增加艇员血压、脉率和呼吸频率,但均为一过性.本次脱险训练方案是安全可靠的.%Objective To observe effects of simulated air-breathing fast buoyancy ascent escape training on the vital signs of submariners.Methods A series of escape training,totaling 69 man-times were carried out at different depths of 3,10,30 and 50 m.Blood pressure,pulse rate and respiratory rate of the submariners were measured before training.the moment after termination of training and 10 min after surfacing from the escape chamber.Results When compared with those of pre-training,most of the indices concerning systolic pressure,diastolic pressure,pulse rate and respiratory rate of the submariners increased quite significantly,with statistical differences (P<0.01) the moment after termination of training.Nevertheless,the values almost returned to normal,10 minutes after training.Conclusions Simulated air-breathing fast buoyancy ascent could elevate blood pressure,pulse rate and respiratory rate of submariners.However,these changes were all transient.The profile of our submarine escape training proves to be safe and reliable.

  4. Diffraction leveraged modulation of X-ray pulses using MEMS-based X-ray optics

    Lopez, Daniel; Shenoy, Gopal; Wang, Jin; Walko, Donald A.; Jung, Il-Woong; Mukhopadhyay, Deepkishore

    2016-08-09

    A method and apparatus are provided for implementing Bragg-diffraction leveraged modulation of X-ray pulses using MicroElectroMechanical systems (MEMS) based diffractive optics. An oscillating crystalline MEMS device generates a controllable time-window for diffraction of the incident X-ray radiation. The Bragg-diffraction leveraged modulation of X-ray pulses includes isolating a particular pulse, spatially separating individual pulses, and spreading a single pulse from an X-ray pulse-train.

  5. Method for pulse to pulse dose reproducibility applied to electron linear accelerators

    An original method for obtaining programmed beam single shots and pulse trains with programmed pulse number, pulse repetition frequency, pulse duration and pulse dose is presented. It is particularly useful for automatic control of absorbed dose rate level, irradiation process control as well as in pulse radiolysis studies, single pulse dose measurement or for research experiments where pulse-to-pulse dose reproducibility is required. This method is applied to the electron linear accelerators, ALIN-10 of 6.23 MeV and 82 W and ALID-7, of 5.5 MeV and 670 W, built in NILPRP. In order to implement this method, the accelerator triggering system (ATS) consists of two branches: the gun branch and the magnetron branch. ATS, which synchronizes all the system units, delivers trigger pulses at a programmed repetition rate (up to 250 pulses/s) to the gun (80 kV, 10 A and 4 ms) and magnetron (45 kV, 100 A, and 4 ms).The accelerated electron beam existence is determined by the electron gun and magnetron pulses overlapping. The method consists in controlling the overlapping of pulses in order to deliver the beam in the desired sequence. This control is implemented by a discrete pulse position modulation of gun and/or magnetron pulses. The instabilities of the gun and magnetron transient regimes are avoided by operating the accelerator with no accelerated beam for a certain time. At the operator 'beam start' command, the ATS controls electron gun and magnetron pulses overlapping and the linac beam is generated. The pulse-to-pulse absorbed dose variation is thus considerably reduced. Programmed absorbed dose, irradiation time, beam pulse number or other external events may interrupt the coincidence between the gun and magnetron pulses. Slow absorbed dose variation is compensated by the control of the pulse duration and repetition frequency. Two methods are reported in the electron linear accelerators' development for obtaining the pulse to pulse dose reproducibility: the method

  6. Language training: French training

    Françoise Benz

    2005-01-01

    General and Professional French Courses The next session will take place from 30 January to 07 April 2006. These courses are open to all persons working on the CERN site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mrs. Benz : Tel. 73127. Writing Professional Documents in French The next session will take place from 30 January to 07 April 2006. This course is designed for people with a good level of spoken French. Duration: 30 hours Price: 660 CHF (for 8 students) For further information and registration, please consult our Web pages: http://cern.ch/Training or contact Mrs. Benz : Tel. 73127. FORMATION EN LANGUES LANGUAGE TRAINING Françoise Benz 73127 language.training@cern.ch

  7. Language Training: French Training

    2004-01-01

    LANGUAGE TRAINING Françoise Benz tel. 73127 language.training@cern.ch General and Professional French Courses The next session will take place from 26 April to 02 July 2004. These courses are open to all persons working on the Cern site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mrs. Benz: Tel. 73127. Writing Professional Documents in French The next session will take place from 26 April to 02 July 2004. This course is designed for people with a good level of spoken French. Duration: 30 hours Price: 660 CHF (for 8 students) For further information and registration, please consult our Web pages: http://cern.ch/Training or contact Mrs. Benz: Tel. 73127.

  8. Language Training: French Training

    2004-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. LANGUAGE TRAINING Françoise Benz tel. 73127 language.training@cern.ch General and Professional French Courses The next session will take place from 26 April to 02 July 2004. These courses are open to all persons working on the Cern site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mrs. Benz: Tel. 73127. Writing Professional Documents in French The next session will take place from 26 April to 02 July 2004. This course is designed for people with a good level...

  9. Language Training: French Training

    2004-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an "application for training" form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. LANGUAGE TRAINING Françoise Benz tel. 73127 language.training@cern.ch General and Professional French Courses The next session will take place from 26 April to 02 July 2004. These courses are open to all persons working on the Cern site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mrs. Benz: Tel. 73127. Writing Professional Documents in French The next session will take place from 26 April to 02 July 2004. This course is designed for people with a good level of s...

  10. Pulse radiolysis

    This supplement to two bibliographies published in 1970 and 1972 lists 734 references to the literature of pulse radiolysis, arranged under eight broad subject headings. The references were compiled by searching Biological Abstracts, Chemical Abstracts, Nuclear Science Abstracts and the Weekly List of Papers in Radiation Chemistry issued by the Radiation Chemistry Data Center of Notre Dame University. Full bibliographic data is given for papers published in the period 1971 to 1974. A personal author index listing more than 600 authors and a similar number of co-authors is included

  11. Beam pulse length determination by spectral analysis

    The report discusses the feasibility of identifying the beam pulse length for heavy ion beams down to 10 enA by observing the amplitude of the Fourier components of the beam pulse train on commercially available UHF spectrum analyzers. Two cases are investigated: 1) where the beam is intercepted by a coaxial Faraday Cup. The resulting electrical signal represents the beam current in the time domain Max signal-to-noise ratio results from entire collection of the beam and 2) where the beam induces a signal in a loosely-coupled capacitive pick-up. The induced pulse train waveform is correspondingly altered and signal-to-noise ratio deteriates. Both cases are shown to be beyond the limits of practical spectrum analyzers for 10 enA beams when 60 pulse widths are considered

  12. Pulse pile-up. I: Short pulses

    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.)

  13. Buck Switching Mode Power Supply Based on Pulse-Train Control Technique Applied to a DC-DC Step-down Power Supply%基于脉冲序列控制技术的降压型开关电源

    侯鑫尧; 倪强

    2011-01-01

    Base on analyzing the principle and working process of pulse-train(PT) control technique,a simple and practical PT controller is designed.PSpice Simulation results of PT controlled buck converter in discontinuous conduction mode(DCM) are performed in this%在分析开关电源脉冲序列(Pulse Train,PT)控制方法的原理和工作过程的基础上,设计了一种简单实用的脉冲序列控制电路。利用PSpice对PT控制DCM Buck变换器进行了仿真研究,并通过实验验证了脉冲序列控制器的可行性和正确性,为PT控制开关电源提供了一种有效的实施方案。

  14. Short (~ ns) single pulse FIR (70-500 µm) multi-kW Raman conversion, of a short pulse (~ 25ns) broadband CO2 Laser

    Marchetti, S; Bartalini, S.; Simili, R.; Martinelli, M

    1994-01-01

    In this work a summary of many pulse compressed (< 10ns), FIR, high power, Raman emissions produced by a short pulse (25 ns) broadband (2GHz) CO2 laser is shown. Generally it has been always possible to obtain a single pulse (≈ ns) conversion from a pulse train of a self -mode locked CO2, also if it is not really reproducible. These emissions are interesting in pulsed high field EPR experiments.

  15. Training safely, Training safety

    Jianjun Wu

    2014-09-01

    Full Text Available It is the basic requirement of maritime safety education to guarantee the safety of teaching operation while training the crew's occupation safety capability. Marine Training Center of Shanghai Maritime University has undertaken the practical teaching of "marine survival" for many years and come up with the whole safety procedures of training. Based on the requirements of SOLAS convention and regulations of STCW over crew training, this paper introduces the safety allocation, utilization and maintenance of teaching equipments. Through the investigation of the safety situation of students' practical operation, the safety teaching method named "four in one" has been put forward, which includes the pre-teaching safety precaution, the whole monitor during the teaching process, the post-teaching summary evaluation, and the reset and standby of teaching facilities. Finally, during the learning and training of "marine survival", crews and students are called on to place priority on personal safety rather than acquisition of knowledge and skills. Only in this way can they be capable of self-protection and protection of others in the career of seafaring.

  16. Directly driven source of multi-gigahertz, sub-picosecond optical pulses

    Messerly, Michael J.; Dawson, Jay W.; Barty, Christopher P.J.; Gibson, David J.; Prantil, Matthew A.; Cormier, Eric

    2015-10-20

    A robust, compact optical pulse train source is described, with the capability of generating sub-picosecond micro-pulse sequences, which can be periodic as well as non-periodic, and at repetition rates tunable over decades of baseline frequencies, from MHz to multi-GHz regimes. The micro-pulses can be precisely controlled and formatted to be in the range of many ps in duration to as short as several fs in duration. The system output can be comprised of a continuous wave train of optical micro-pulses or can be programmed to provide gated bursts of macro-pulses, with each macro-pulse consisting of a specific number of micro-pulses or a single pulse picked from the higher frequency train at a repetition rate lower than the baseline frequency. These pulses could then be amplified in energy anywhere from the nJ to MJ range.

  17. Effect of Nuclear Motion on Molecular High-Order Harmonics and on Generation of Attosecond Pulses in Intense Laser Pulses

    Bandrauk, André D.; Chelkowski, Szczepan; Kawai, Shinnosuke; Lu, Huizhong

    2008-10-01

    We calculate harmonic spectra and shapes of attosecond-pulse trains using numerical solutions of Non-Born-Oppenheimer time-dependent Shrödinger equation for 1D H2 molecules in an intense laser pulse. A very strong signature of nuclear motion is seen in the time profiles of high-order harmonics. In general the nuclear motion shortens the part of the attosecond-pulse train originating from the first electron contribution, but it may enhance the second electron contribution for longer pulses. The shape of time profiles of harmonics can thus be used for monitoring the nuclear motion.

  18. Evaluating Training

    Zhang Huanhai; Zhang Lei's

    2008-01-01

    @@ Clause 6.2.2: Competence, Awareness and Training in ISO9001:2000 standard sets the training requirements for organizations. Problems with evaluating the outcomes of training arise during examination and verification.

  19. Generation of short and intense attosecond pulses

    Khan, Sabih Ud Din

    Extremely broad bandwidth attosecond pulses (which can support 16as pulses) have been demonstrated in our lab based on spectral measurements, however, compensation of intrinsic chirp and their characterization has been a major bottleneck. In this work, we developed an attosecond streak camera using a multi-layer Mo/Si mirror (bandwidth can support ˜100as pulses) and position sensitive time-of-flight detector, and the shortest measured pulse was 107.5as using DOG, which is close to the mirror bandwidth. We also developed a PCGPA based FROG-CRAB algorithm to characterize such short pulses, however, it uses the central momentum approximation and cannot be used for ultra-broad bandwidth pulses. To facilitate the characterization of such pulses, we developed PROOF using Fourier filtering and an evolutionary algorithm. We have demonstrated the characterization of pulses with a bandwidth corresponding to ˜20as using synthetic data. We also for the first time demonstrated single attosecond pulses (SAP) generated using GDOG with a narrow gate width from a multi-cycle driving laser without CE-phase lock, which opens the possibility of scaling attosecond photon flux by extending the technique to peta-watt class lasers. Further, we generated intense attosecond pulse trains (APT) from laser ablated carbon plasmas and demonstrated ˜9.5 times more intense pulses as compared to those from argon gas and for the first time demonstrated a broad continuum from a carbon plasma using DOG. Additionally, we demonstrated ˜100 times enhancement in APT from gases by switching to 400 nm (blue) driving pulses instead of 800 nm (red) pulses. We measured the ellipticity dependence of high harmonics from blue pulses in argon, neon and helium, and developed a simple theoretical model to numerically calculate the ellipticity dependence with good agreement with experiments. Based on the ellipticity dependence, we proposed a new scheme of blue GDOG which we predict can be employed to extract

  20. Language Training: English Training

    Françoise Benz

    2004-01-01

    If you wish to participate in one of the following courses, please discuss with your supervisor and apply electronically directly from the course description pages that can be found on the Web at: http://www.cern.ch/Training/ or fill in an 'application for training' form available from your Divisional Secretariat or from your DTO (Divisional Training Officer). Applications will be accepted in the order of their receipt. General and Professional English Courses The next session will take place from 04 October 2004 to 11 February 2005 (3 weeks break at Christmas). These courses are open to all persons working on the CERN site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mr. Liptow, tel. 72957. Oral Expression This course is intended for people with a good knowledge of English who want to practise and maintain their speaking skills while extending their vocabulary. There will be approximately 8 participants in...

  1. LIU 0.5/3000 pulse-periodical linear induction accelerator

    LIU 0.5/3000 accelerator designed for production of accelerator nanosecond high-current electron beam is described. Its main characteriatics are as follows: electron beam energy in pulse is 50j; electron peak energy - 500 keV; beam pulse power - 15 GW; current amplitude in pulse - 3 kA; beam current duration - 80 ns (at 0.1 level); beam aperture - 8-30cm2; accelerator operates in three modes: single-pulse mode, continuous mode with 50 pulses/s. Succession frequency, mode of pulse train formationfrom 5-10 pulses with equivalent pulse duration in the train up to 200 pulses/s; operating lifetime is ≥ 107 pulses. Accelerator dimensions are 2000x2100x900 mm, its mass - 800 kg

  2. Ultrashort pulse propagation in multiple-grating fiber structures.

    Chen, L R; Benjamin, S D; Smith, P W; Sipe, J E; Juma, S

    1997-03-15

    We propose a multiple-grating fiber structure that decomposes an ultrashort broadband optical pulse simultaneously in both wavelength and time. As an initial demonstration, we used a transform-limited 1-ps Gaussian pulse centered at 1.55 mu;m as the ultrashort broadband input into a three-grating fiber structure and generated three output pulses separated in wavelength and time with good correlation between experimental results and simulations. This device structure can be used to generate a multiwavelength train of pulses for use in wavelength-division-multiplexed systems or to implement frequency-domain encoding of coherent pulses for optical code-division multiple access. PMID:18183215

  3. Optimal laser pulse energy partitioning for air ionization

    Schubert, Elise; Matthews, Mary; Courjaud, Antoine; Kasparian, Jérôme; Wolf, Jean-Pierre

    2016-01-01

    We investigate the pulse partitioning of a 6.3 mJ, 450 fs pulse at 1030 nm to produce plasma channels. At such moderate energies, splitting the energy into several sub-pulses reduces the ionization efficiency and thus does not extend the plasma lifetime. We numerically show that when sufficient energy to produce multifilamentation is available, splitting the pulse temporally in a pulse train increases the gas temperature compared to a filament bundle of the same energy. This could improve the mean free path of the free electrons, therefore enhancing the efficiency of discharge triggering.

  4. Excimer Laser Pulse Compress With Pulse Feedback

    2008-01-01

    <正>To attain a shorter laser pulse, a compressing technique called pulse feedback was developed from the saturation gain switch applied to the amplification in a discharge pumping excimer laser cavity. It can

  5. Training organisation

    Slovenske elektrarne considers a specific training and education of experienced experts to be a key issue. The company gradually undergoes quite demanding change in the field of education and training of the nuclear power plants staff. We have an ambitious vision - to create one of the best training organisations in Europe by the means of systematic approach to the training. (author)

  6. Periodic dark pulse emission induced by delayed feedback in a quantum well semiconductor laser

    L. Li

    2012-12-01

    Full Text Available We report the experimental observation of periodic dark pulse emission in a quantum-well semiconductor laser with delayed optical feedback. We found that under appropriate operation conditions the laser can also emit a stable train of dark pulses. The repetition frequency of the dark pulse is determined by the external cavity length. Splitting of the dark pulse was also observed. We speculate that the observed dark pulse is a kind of temporal cavity soliton formed in the laser.

  7. Language Training - French Training

    HR Department

    2008-01-01

    General and Professional French Courses The next session will take place from 26 January to 3rd April 2009. These courses are open to all persons working on the CERN site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mrs. Nathalie Dumeaux : Tel. 78144. Writing Professional Documents in French The next session will take place from 26 January to 3rd April 2009. This course is designed for people with a good level of spoken French. Duration: 30 hours Price: 660 CHF For further information and registration, please consult our Web pages: http://cern.ch/Training or contact Mrs. Nathalie Dumeaux : Tel. 78144. Nathalie Dumeaux Tel. 78144 mailto:nathalie.dumeaux@cern.ch

  8. Language Training - French Training

    HR Department

    2009-01-01

    General and Professional French Courses The next session will take place from 26 January to 3rd April 2009. These courses are open to all persons working on the CERN site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mrs. Nathalie Dumeaux : Tel. 78144. Writing Professional Documents in French The next session will take place from 26 January to 3rd April 2009. This course is designed for people with a good level of spoken French. Duration: 30 hours Price: 660 CHF For further information and registration, please consult our Web pages: http://cern.ch/Training or contact Mrs. Nathalie Dumeaux : Tel. 78144. Nathalie Dumeaux Tel. 78144 mailto:nathalie.dumeaux@cern.ch

  9. Language training: French training

    2008-01-01

    General and professional french coursesThe next session will take place from 14 April to 27 June 2008. These courses are open to all persons working on the CERN site and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mrs Nathalie Dumeaux: Tel. 78144. Writing Professional Documents in French The next session will take place from 14 April to 27 June 2008. This course is designed for people with a good level of spoken French. Duration: 30 hours Price: 660 CHF For further information and registration, please consult our Web pages: http://cern.ch/Training or contact Mrs Nathalie Dumeaux: Tel. 78144.

  10. Nonlinear 6-fold enhancement of laser drilling efficiency by double pulse mode: prospective in medicine application

    Pershina, N. S.; Pershin, S. M.; Cech, M.; Prochazka, I.

    2009-05-01

    The efficiency of laser ablation drilling of metal and dielectric (ceramic, glasses, etc.) samples with single and multiple laser pulses per one laser shot was experimentally studied. The laser is operated on the fundamental (1064 nm) wavelength of Nd:YAG laser with 30 ns pulse length or its second (532 nm) and third (351 nm) harmonics, respectively. The laser shot repletion rate was 1 Hz. The pulses in train were separated by 25-45 μs interval. The crater depth and drilling speed dependence increasing on pulse number in multipulse train was studied. The laser ablation normalized per pulse energy in train dependence is not linear function. The strong ablation enhancement was observed. The optimal (in sense the total pulse energy using) drilling can be obtained with double pulse mode compared with 3 - 5 pulses. Nonlinear more than 6 fold increasing of crater depth produced by the second pulse in train was detected. The mechanism of selective increasing of the second pulse interaction efficiency with the hard target is discussed. Experimental results explained in terms of double pulse mode laser ablation model. Spectroscopy study of laser plasma was observed to confirm discussed model of high efficiency for two laser pulse laser ablation. Efficiency of double pulse mode compared with multipulse mode is discussed to be more perspective for various applications of laser ablation. The medicine (surgery, dentist, ophthalmology and so on) application is the most prospective, for instance, the teeth drilling or glaucoma perforation, can be done with smaller energy value.

  11. Language Training: English Training

    Françoise Benz

    2004-01-01

    La prochaine session se déroulera du 04 octobre 2004 au 11 février 2005 (interruption de 3 semaines à Noël). Ces cours s'adressent à toute personne travaillant au CERN ainsi qu'à leur conjoint. Pour vous inscrire et voir tout le détail des cours proposés, consultez nos pages Web : http://cern.ch/Training Vous pouvez aussi contacter M. Liptow, tél. 72957. General and Professional English Courses The next session will take place from 04 October 2004 to 11 February 2005 (3 weeks break at Christmas). These courses are open to all persons working on the CERN site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mr. Liptow, tel. 72957. Oral Expression This course is intended for people with a good knowledge of English who want to practise and maintain their speaking skills while extending their vocabulary. There will be approximately 8 participants ...

  12. Language Training: English Training

    Françoise Benz

    2004-01-01

    General and Professional English Courses The next session will take place from 04 October 2004 to 11 February 2005 (3 weeks break at Christmas). These courses are open to all persons working on the CERN site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mr. Liptow, tel. 72957. Oral Expression This course is intended for people with a good knowledge of English who want to practise and maintain their speaking skills while extending their vocabulary. There will be approximately 8 participants in a class. Speaking activities will include discussions, meeting simulations, role-plays etc. depending on the needs of the students. Duration: 20 hours (2 hours a week) Price: 440 CHF (for 8 students) For further information, please contact Mr. Liptow, tel. 72957. Date and timetable will be fixed when there are sufficient participants enrolled. FORMATION EN LANGUES LANGUAGE TRAINING Françoise Benz 73127 langua...

  13. Language Training: English Training

    Françoise Benz

    2004-01-01

    General and Professional English Courses The next session will take place from 04 October 2004 to 11 February 2005 (3 weeks break at Christmas). These courses are open to all persons working on the CERN site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mr. Liptow, tel. 72957. Oral Expression This course is intended for people with a good knowledge of English who want to practise and maintain their speaking skills while extending their vocabulary. There will be approximately 8 participants in a class. Speaking activities will include discussions, meeting simulations, role-plays etc. depending on the needs of the students. Duration: 20 hours (2 hours a week) Price: 440 CHF (for 8 students) For further information, please contact Mr. Liptow, tel. 72957. Date and timetable will be fixed when there are sufficient participants enrolled. FORMATION EN LANGUES LANGUAGE TRAINING Françoise Benz 73127 languag...

  14. Language Training - French Training

    2007-01-01

    General and Professional French Courses The next session will take place from 29 January to 30 March 2007. These courses are open to all persons working on the CERN site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Mrs. Benz : Tel. 73127. Writing Professional Documents in French The next session will take place from 29 January to 30 March 2007. This course is designed for people with a good level of spoken French. Duration: 30 hours Price: 660 CHF (for 8 students) For further information and registration, please consult our Web pages:   http://cern.ch/Training or contact Mrs. Benz : Tel. 73127. Writing Professional Documents in English The next session will take place from January to June 2007 (break at Easter). This course is designed for people with a good level of spoken English. Duration: 30 hours Price: 660 CHF (for 8 students) Timetable will be fixed after discussion with the students. For registratio...

  15. Inductive Pulse Generation

    Lindblom, Adam

    2006-01-01

    Pulsed power generators are a key component in compact systems for generation of high-power microwaves (HPM). HPM generation by virtual cathode devices such as Vircators put high demands on the source. The rise time and the pulse length of the source voltage are two key issues in the generation of HPM radiation. This thesis describes the construction and tests of several inductive high power pulse generators. The pulse generators were designed with the intent to deliver a pulse with fast rise...

  16. Stability of multicomponent-soliton trains

    Stable configurations of periodic multicomponent-soliton trains are determined with relevance to the idea of data storing, transmitting and processing using the pulse-polarization vector as an information register. The interactions of the solitons of the train are expected to stabilize this polarization vector, preventing it from changes induced by the transmission-line imperfections as well as by the inherent increase of the pulse-parameter uncertainty with time. We investigate the use of the bright (self-focusing), dark (self-defocusing) and mixed bright-dark multicomponent solitons whose dynamics is governed by the nonlinear Schrodinger equation. The relevance of the (previously used) Toda-chain model to the dynamical description of the parameters of the bright-soliton train is verified. Unlike the bright solitons, trains of the mixed bright-dark solitons are found to be stable with relevance to externally driven change of the polarization of a single pulse.

  17. Enhancement of laser induced Au nanoparticle formation by femtosecond pulse shaping

    Ferreira, P. H. D.; Silva, D. L.; Siqueira, J. P.; Balogh, D. T.; Canuto, S.; Misoguti, L.; Mendonca, C. R.

    2013-07-01

    We report the control of Au nanoparticle (NP) formation by using shaped 30 fs pulses, in a solution containing HAuCl4 and chitosan. By using a sinusoidal spectral phase, a periodic train of pulses is generated. When the period of the pulse train matches certain Raman resonances of chitosan, the reducing agent of the process, an enhancement of the Au NP formation is observed. Theoretical quantum chemical calculations indicate that the outer groups of the chitosan are mostly influenced by low Raman frequencies, which is in reasonably agreement with the experimental data and indicates an enhancement in the Au NP formation as the pulse train period increases (low frequency).

  18. XUV attosecond pulses: generation and measurement

    An overview is given of the state-of-the-art in optical attosecond pulse generation and measurements. The emission of ultrashort bursts of XUV radiation from a laser driven plasma is described and analysed in the framework of a semiclassical model that explains essential features of the emitted spectrum. While under most conditions, trains of XUV bursts, separated by the half-cycle time of the driving laser field are emitted, few-cycle laser pulses of a well-defined carrier-envelope phase can yield isolated XUV pulses of sub-femtosecond duration. A time resolving correlation technique that relies on the interaction of electrons with a strong laser light field allows the measurement of attosecond electron dynamics from systems excited by these ultrashort XUV pulses. (topical review)

  19. Training Visions

    Training, 2011

    2011-01-01

    In this article, "Training" asks the 2011 winners to give their predictions for what training--either in general or specifically at their companies--will look like in the next five to 10 years. Perhaps their "training visions" will spark some ideas in one's organization--or at least help prepare for what might be coming in the next decade or so.

  20. Few-cycle isolated attosecond pulses

    indicates the presence of a predominant second order dispersion (positive chirp), which is intrinsic to the XUV generation process. As recently demonstrated in the case of trains of attosecond pulses, the positive chirp of the radiation produced by high-order harmonic generation can be compensated for by the negative group delay dispersion of thin aluminum foils. Upon increasing the thickness of an aluminum plate we have obtained XUV pulses with duration shorter than 300 as (at 37 eV), thus corresponding to few cycles of the electric field.

  1. Towards efficient generation of attosecond pulses from overdense plasma targets

    Theoretical studies and computer simulations predict efficient generation of attosecond electromagnetic pulses from overdense plasma targets, driven by relativistically strong laser pulses. These predictions need to be validated in time resolved experiments in order to provide a route for applications. The first available femtosecond sources for these experiments are likely to be 10 fs pulses of a few millijoules, which could provide focal intensities at about the relativistic threshold. With particle-in-cell simulations, we demonstrate that the radiation resulting from interaction of such pulses with solid targets is expected to be attosecond trains with very high conversion efficiency as relativistic effects start to act

  2. Language Training - English Training

    HR Department

    2009-01-01

    General and Professional English Courses The next session will take place: from 2nd March to end of June 2009 (1/2 weeks break at Easter). These courses are open to all persons working on the CERN site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Nathalie Dumeaux, tel. 78144. Oral Expression The next session will take place from 2nd March to end of June 2009 (1/2 weeks break at Easter). This course is intended for people with a good knowledge of English who want to enhance their speaking skills. There will be on average of 8 participants in a class. Speaking activities will include discussions, meeting simulations, role-plays etc. depending on the needs of the students. Duration: 30 hours Price: 660 CHF (for a minimum of 8 students) Writing Professional Documents in English The next session will take place from 2nd March to end of June 2009 (1/2 weeks break at Easter). This course is designed for people w...

  3. Language Training - English Training

    HR Department

    2009-01-01

    General and Professional English Courses The next session will take place: from 2nd March to end of June 2009 (1/2 weeks break at Easter). These courses are open to all persons working on the CERN site, and to their spouses. For registration and further information on the courses, please consult our Web pages: http://cern.ch/Training or contact Nathalie Dumeaux, tel. 78144. Oral Expression The next session will take place from 2nd March to end of June 2009 (1/2 weeks break at Easter). This course is intended for people with a good knowledge of English who want to enhance their speaking skills. There will be an average of 8 participants per class. Speaking activities will include discussions, meeting simulations, role-plays, etc., depending on the needs of the students. Duration: 30 hours Price: 660 CHF (for a minimum of 8 students) Writing Professional Documents in English The next session will take place from 2nd March to end of June 2009 (1/2 weeks break at Easter). This course is designed for people ...

  4. Radial pulse (image)

    ... heart. The arteries are the vessels with the "pulse", a rhythmic pushing of the blood in the ... a refilling of the heart chamber. To determine heart rate, one feels the beats at a pulse point ...

  5. Wrist pulse (image)

    To measure the pulse at the wrist, place the index and middle finger over the underside of the opposite wrist, below the base ... firmly with flat fingers until you feel the pulse in the radial artery.

  6. Divided-Pulse Lasers

    Lamb, Erin S.; Wright, Logan G.; Wise, Frank W.

    2014-01-01

    We demonstrate the use of coherent division and recombination of the pulse within an ultrafast laser cavity to manage the nonlinear phase accumulation and scale the output pulse energy. We implement the divided-pulse technique in an ytterbium-doped fiber laser and achieve 16-times scaling of the pulse energy, to generate 6 nJ and 1.4 ps solitons in single mode fiber. Potential extensions of this concept are discussed.

  7. Fright train!

    London firemen are concerned about the safety of trains transporting nuclear waste in flasks through London. In 1979 the London Fire Brigade's Union called for more information as to when the trains run, basic training in dealing with radioactive fires, better equipment to tackle fires and for the stopping of nuclear trains. The 1988 position is reviewed. It is concluded that there has been little change. No training exercises have been arranged and the instructions given to firefighters are to wait for experts from the United Kingdom Atomic Energy Authority should a fire occur. The Fire Brigades are still not informed of the movement of the trains, and improvements in equipment are in dosimetry, not in personnel protection. (U.K.)

  8. Pulse-Width Jitter Measurement for Laser Diode Pulses

    TANG Jun-Hua; WANG Yun-Cai

    2006-01-01

    @@ Theoretical analysis and experimental measurement of pulse-width jitter of diode laser pulses are presented. The expression of pulse power spectra with all amplitude jitter, timing jitter and pulse-width jitter is deduced.

  9. Pulse bundles and passive harmonic mode-locked pulses in Tm-doped fiber laser based on nonlinear polarization rotation.

    Wang, Xiong; Zhou, Pu; Wang, Xiaolin; Xiao, Hu; Liu, Zejin

    2014-03-10

    We demonstrate the nanosecond-level pulses in Tm-doped fiber laser generated by passively harmonic mode-locking. Nonlinear polarization rotation performed by two polarization controllers (PCs) is employed to induce the self-starting harmonic mode-locking. The fundamental repetition rate of the laser is 448.8 kHz, decided by the length of the cavity. Bundles of pulses with up to 17 uniform subpulses are generated due to the split of pulse when the pump power increases and the PCs are adjusted. Continuous harmonic mode-locked pulse trains are obtained with 1st to 6th and even more than 15th order when the positions of the PCs are properly fixed and the pump power is scaled up. The widths of all the uniform individual pulses are mostly 3-5 ns, and pulse with width of 304 ns at fundamental repetition rate can also be generated by adjusting the PCs. Hysteresis phenomenon of the passively harmonic mode-locked pulses' repetition frequency versus pump power is observed. The rather wide 3dB spectral bandwidth of the pulse train (25 nm) indicates that they may resemble noise-like pulses. PMID:24663948

  10. Studies of solid propellant combustion with pulsed radiography

    Godai, T.; Tanemura, T.; Fujiwara, T.; Shimizu, M.

    1987-01-01

    Pulsed radiography was applied to observe solid propellant surface regression during rocket motor operation. Using a 150 KV flash X-ray system manufactured by the Field Emission Corporation and two kinds of film suppliers, images of the propellant surface of a 5 cm diameter end burning rocket motor were recorded on film. The repetition frame rate of 8 pulses per second and the pulse train length of 10 pulses are limited by the capability of the power supply and the heat build up within the X-ray tube, respectively. The experiment demonstrated the effectiveness of pulsed radiography for observing solid propellant surface regression. Measuring the position of burning surface images on film with a microdensitometer, quasi-instantaneous burning rate as a function of pressure and the variation of characteristic velocity with pressure and gas stay time were obtained. Other research items to which pulsed radiography can be applied are also suggested.