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Sample records for adiabatic-rectangular pulse train

  1. Academic Training - Pulsed SC Magnets

    CERN Multimedia

    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. Efficient High-Energy Pulse-Train Generation Using a 2 n-Pulse Michelson Interferometer.

    Science.gov (United States)

    Siders, C W; Siders, J L; Taylor, A J; Park, S G; Weiner, A M

    1998-08-01

    We demonstrate a novel, Michelson-based, ultrafast multiplexer with a throughput approaching 100% for a polarization-multiplexed train and 50% for a linearly polarized train, which is compatible with a high-energy pulse train and shaped-pulse generation. The interpulse spacings in the resultant 2(n)-pulse train can be adjusted continuously from multinanoseconds through zero. Using this interferometer, we also demonstrate generation of a 16-pulse train of terahertz pulses.

  3. Coherence control of pulse trains by spectral phase modulation

    Science.gov (United States)

    Ding, Chaoliang; Koivurova, Matias; Turunen, Jari; Setälä, Tero; Friberg, Ari T.

    2017-09-01

    We propose a technique to control the spectral and temporal coherence properties of pulsed beams of light via time-dependent manipulation of the spectral phase. Modulation schemes for the generation of partially coherent pulse trains from a train of fully coherent pulses are presented. The feasibility of experimental realization of the method is confirmed by numerical estimates.

  4. A Method for Distinguishing Attosecond Single Pulse from Attosecond Pulse Train

    Institute of Scientific and Technical Information of China (English)

    HUO Yi-Ping; ZENG Zhi-Nan; LI Ru-Xin; XU Zhi-Zhan

    2004-01-01

    @@ The driving laser field assisted attosecond soft-extreme-ultraviolet (XUV) photo-ionization was used successfully to measure the duration of the attosecond pulse based on the cross-correlation method. However, this method in principle cannot distinguish a single attosecond pulse from the attosecond pulse train. We propose a technique for directly distinguishing attosecond single pulse from attosecond pulse train based on the photo-ionization of atoms by attosecond XUV pulse in the presence of a two-colour strong laser pulse.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Shalloo, R.J., E-mail: robert.shalloo@physics.ox.ac.uk; 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.

  7. Laser induced breakdown spectroscopy with picosecond pulse train

    Science.gov (United States)

    Lednev, Vasily N.; Pershin, Sergey M.; Sdvizhenskii, Pavel A.; Grishin, Mikhail Ya; Davydov, Mikhail A.; Stavertiy, Anton Ya; Tretyakov, Roman S.

    2017-02-01

    Picosecond pulse train and nanosecond pulse were compared for laser ablation and laser induced breakdown spectroscopy (LIBS) measurements. A detailed study revealed that the picosecond pulse train ablation improved the quality of laser craters (symmetric crater walls and the absence of large redeposited droplets), which was explained by a smaller heat affected zone and suppression of melt splash. Greater plasma dimensions and brighter plasma emission were observed by gated imaging for picosecond pulse train compared to nanosecond pulse ablation. Increased intensity of atomic and ionic lines in gated and time integrated spectra provided better signal-to-noise ratio for picosecond pulse train sampling. Higher temperature and electron density were detected during first microsecond for the plasma induced by the picosecond pulse train. Improved shot-to-shot reproducibility for atomic/ionic line intensity in the case of picosecond pulse train LIBS was explained by more effective atomization of target material in plasma and better quality of laser craters. Improved precision and limits of detections were determined for picosecond pulse train LIBS due to better reproducibility of laser sampling and increased signal-to-noise ratio.

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

    CERN Document Server

    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.

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

    DEFF Research Database (Denmark)

    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 → I + Br, changes as a function of time delay when the two excited wave packets interfere. The underlying mechanisms are analyzed and the change in the branching ratio as a function of time delay is only a reflection of a changing frequency distribution of the pulse train; the branching ratio does...

  10. Temporal coherence characterization of supercontinuum pulse trains using Michelson's interferometer.

    Science.gov (United States)

    Dutta, Rahul; Turunen, Jari; Genty, Goëry; Friberg, Ari T

    2016-04-20

    Temporal coherence properties of supercontinuum pulse trains generated in nonlinear fibers are analyzed within the framework of the second-order coherence theory of nonstationary light. Time-resolved Michelson's interference patterns are simulated, from which the full two-time mutual coherence function can (at least in principle) be determined experimentally. Standard time-integrated Michelson's interferograms are also simulated and shown to provide a rough estimate for the coherence time of the quasi-stationary contribution. A simple but illustrative analytical model representing supercontinuum pulse trains is presented, and numerically simulated realizations of such pulse trains are considered.

  11. Effect of aligning pulse train on the orientation and alignment of a molecule in presence of orienting pulse

    Science.gov (United States)

    Tyagi, Ashish; Maan, Anjali; Ahlawat, Dharamvir Singh; Prasad, Vinod

    2017-02-01

    Field-free molecular alignment is studied theoretically in presence of orienting laser pulse and a delayed Infrared laser (IRL) pulse train. The pulse shapes taken are sine square (sin2) and square. The degree of alignment can be significantly enhanced by the combination of orienting pulse and IRL pulse train compared with only IRL pulse train. Special emphasis is laid on time delay between orienting and aligning pulse, the width and shape of the pulse train. By adjusting the time delay, width and intensity of coupling laser one can suppress a population of particular state while simultaneously enhancing the population of desired states.

  12. Frequency Stepped Pulse Train Modulated Wind Sensing Lidar

    DEFF Research Database (Denmark)

    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 generation of the FSPT. The source generates a pulse train where each pulse has an optical carrier frequency...... of frequency shifts corresponding to a specific distance. The spatial resolution depends on the repetition rate of the pulses in the pulse train. Directional wind measurements are shown and compared to a CW lidar measurement. The carrier to noise ratio of the FSPT lidar compared to a CW lidar is discussed...

  13. Monopolar intracochlear pulse trains selectively activate the inferior colliculus.

    Science.gov (United States)

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

    2012-10-01

    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 configurations. To test whether monopolar intracochlear stimulation can produce selective activation of the inferior colliculus, we measured activation widths along the tonotopic axis of the inferior colliculus for acoustic tones and 1,000-pulse/s electrical pulse trains in guinea pigs and cats. Electrical pulse trains were presented using an array of 6-12 stimulating electrodes distributed longitudinally on a space-filling silicone carrier positioned in the scala tympani of the cochlea. We found that for monopolar, bipolar, and acoustic stimuli, activation widths were significantly narrower for sustained responses than for the transient response to the stimulus onset. Furthermore, monopolar and bipolar stimuli elicited similar activation widths when compared at stimulus levels that produced similar peak spike rates. Surprisingly, we found that in guinea pigs, monopolar and bipolar stimuli produced narrower sustained activation than 60 dB sound pressure level acoustic tones when compared at stimulus levels that produced similar peak spike rates. Therefore, we conclude that intracochlear electrical stimulation using monopolar pulse trains can produce activation patterns that are at least as selective as bipolar or acoustic stimulation.

  14. Efficient high-energy pulse-train generation using a 2{sup n}-pulse Michelson interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Siders, C.W.; Siders, J.L.; Taylor, A.J. [Materials Science and Technology Division, Los Alamos National Laboratory, MS D429, Los Alamos, New Mexico 87545 (United States); Park, S.; Weiner, A.M. [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    1998-08-01

    We demonstrate a novel, Michelson-based, ultrafast multiplexer with a throughput approaching 100{percent} for a polarization-multiplexed train and 50{percent} for a linearly polarized train, which is compatible with a high-energy pulse train and shaped-pulse generation. The interpulse spacings in the resultant 2{sup n}-pulse train can be adjusted continuously from multinanoseconds through zero. Using this interferometer, we also demonstrate generation of a 16-pulse train of terahertz pulses. {copyright} 1998 Optical Society of America

  15. Half Cycle Pulse Train Induced State Redistribution of Rydberg Atoms

    CERN Document Server

    Mandal, P K

    2009-01-01

    Population transfer between low lying Rydberg states independent of the initial state is realized using a train of half-cycle pulses with pulse durations much less than the classical orbit period. We demonstrate experimentally the transfer of population from initial states around n=50 down to n<40 as well as up to the continuum. The measured population transfer matches well to a model of the process for 1D atoms.

  16. Femtosecond laser pulse train interaction with dielectric materials

    CERN Document Server

    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.

  17. Effect of aligning pulse train on the orientation and alignment of a molecule in presence of orienting pulse.

    Science.gov (United States)

    Tyagi, Ashish; Maan, Anjali; Ahlawat, Dharamvir Singh; Prasad, Vinod

    2017-02-15

    Field-free molecular alignment is studied theoretically in presence of orienting laser pulse and a delayed Infrared laser (IRL) pulse train. The pulse shapes taken are sine square (sin(2)) and square. The degree of alignment can be significantly enhanced by the combination of orienting pulse and IRL pulse train compared with only IRL pulse train. Special emphasis is laid on time delay between orienting and aligning pulse, the width and shape of the pulse train. By adjusting the time delay, width and intensity of coupling laser one can suppress a population of particular state while simultaneously enhancing the population of desired states. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Pulse-train solutions and excitability in an optoelectronic oscillator

    Science.gov (United States)

    Rosin, D. P.; Callan, K. E.; Gauthier, D. J.; Schöll, E.

    2011-11-01

    We study an optoelectronic time-delay oscillator with bandpass filtering for different values of the filter bandwidth. Our experiments show novel pulse-train solutions with pulse widths that can be controlled over a three-order-of-magnitude range, with a minimum pulse width of ~150 ps. The equations governing the dynamics of our optoelectronic oscillator are similar to the FitzHugh-Nagumo model from neurodynamics with delayed feedback in the excitable and oscillatory regimes. Using a nullclines analysis, we derive an analytical proportionality between pulse width and the low-frequency cutoff of the bandpass filter, which is in agreement with experiments and numerical simulations. Furthermore, the nullclines help to describe the shape of the waveforms.

  19. Delaying Trains of Short Light Pulses in WGM Resonators

    Science.gov (United States)

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

    2008-01-01

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

  20. Changes across time in the temporal responses of auditory nerve fibers stimulated by electric pulse trains.

    Science.gov (United States)

    Miller, Charles A; Hu, Ning; Zhang, Fawen; Robinson, Barbara K; Abbas, Paul J

    2008-03-01

    Most auditory prostheses use modulated electric pulse trains to excite the auditory nerve. There are, however, scant data regarding the effects of pulse trains on auditory nerve fiber (ANF) responses across the duration of such stimuli. We examined how temporal ANF properties changed with level and pulse rate across 300-ms pulse trains. Four measures were examined: (1) first-spike latency, (2) interspike interval (ISI), (3) vector strength (VS), and (4) Fano factor (FF, an index of the temporal variability of responsiveness). Data were obtained using 250-, 1,000-, and 5,000-pulse/s stimuli. First-spike latency decreased with increasing spike rate, with relatively small decrements observed for 5,000-pulse/s trains, presumably reflecting integration. ISIs to low-rate (250 pulse/s) trains were strongly locked to the stimuli, whereas ISIs evoked with 5,000-pulse/s trains were dominated by refractory and adaptation effects. Across time, VS decreased for low-rate trains but not for 5,000-pulse/s stimuli. At relatively high spike rates (>200 spike/s), VS values for 5,000-pulse/s trains were lower than those obtained with 250-pulse/s stimuli (even after accounting for the smaller periods of the 5,000-pulse/s stimuli), indicating a desynchronizing effect of high-rate stimuli. FF measures also indicated a desynchronizing effect of high-rate trains. Across a wide range of response rates, FF underwent relatively fast increases (i.e., within 100 ms) for 5,000-pulse/s stimuli. With a few exceptions, ISI, VS, and FF measures approached asymptotic values within the 300-ms duration of the low- and high-rate trains. These findings may have implications for designs of cochlear implant stimulus protocols, understanding electrically evoked compound action potentials, and interpretation of neural measures obtained at central nuclei, which depend on understanding the output of the auditory nerve.

  1. Pulse train induced rotational excitation and orientation of a polar molecule.

    Science.gov (United States)

    Tyagi, Ashish; Arya, Urvashi; Vidhani, Bhavna; Prasad, Vinod

    2014-08-14

    We investigate theoretically the rotational excitation and field free molecular orientation of polar HBr molecule, interacting with train of ultrashort laser pulses. By adjusting the number of pulses, pulse period and the intensity of the pulse, one can suppress a population while simultaneously enhancing the desired population in particular rotational state. We have used train of laser pulses of different shaped pulse envelopes. The dynamics and orientation of molecules in the presence of pulse train of different shapes is studied and explained. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Triggering and guiding electric discharge by a train of UV picosecond pulses combined with a long UV pulse

    CERN Document Server

    Ionin, A A; Levchenko, A O; Seleznev, L V; Shutov, A V; Sinitsyn, D V; Smetanin, I V; Ustinovsky, N N; Zvorykin, V D

    2012-01-01

    Non-self-sustained electric discharge and electric breakdown were triggered and guided by a train of picosecond UV pulses overlapped with a long free-running UV pulse of a hybrid Ti:Sapphire-KrF laser facility. Photocurrent sustained by this train is two orders of magnitude higher, and electric breakdown distance is twice longer than those for the discharge triggered by the long UV pulse only.

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

    Science.gov (United States)

    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.

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

    Institute of Scientific and Technical Information of China (English)

    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.

  5. Quasi-phase-matched high-order harmonic generation using tunable pulse trains.

    Science.gov (United States)

    O'Keeffe, Kevin; Lloyd, David T; Hooker, Simon M

    2014-04-07

    A simple technique for generating trains of ultrafast pulses is demonstrated in which the linear separation between pulses can be varied continuously over a wide range. These pulse trains are used to achieve tunable quasi-phase-matching of high harmonic generation over a range of harmonic orders up to the harmonic cut-off, resulting in enhancements of the harmonic intensity in excess of an order of magnitude. The peak enhancement of the harmonics is clearly shown to depend on the separation between pulses, as well as the number of pulses in the train, representing an easily tunable source of quasi-phase-matched high harmonic generation.

  6. Unanesthetized auditory cortex exhibits multiple codes for gaps in cochlear implant pulse trains.

    Science.gov (United States)

    Kirby, Alana E; Middlebrooks, John C

    2012-02-01

    Cochlear implant listeners receive auditory stimulation through amplitude-modulated electric pulse trains. Auditory nerve studies in animals demonstrate qualitatively different patterns of firing elicited by low versus high pulse rates, suggesting that stimulus pulse rate might influence the transmission of temporal information through the auditory pathway. We tested in awake guinea pigs the temporal acuity of auditory cortical neurons for gaps in cochlear implant pulse trains. Consistent with results using anesthetized conditions, temporal acuity improved with increasing pulse rates. Unlike the anesthetized condition, however, cortical neurons responded in the awake state to multiple distinct features of the gap-containing pulse trains, with the dominant features varying with stimulus pulse rate. Responses to the onset of the trailing pulse train (Trail-ON) provided the most sensitive gap detection at 1,017 and 4,069 pulse-per-second (pps) rates, particularly for short (25 ms) leading pulse trains. In contrast, under conditions of 254 pps rate and long (200 ms) leading pulse trains, a sizeable fraction of units demonstrated greater temporal acuity in the form of robust responses to the offsets of the leading pulse train (Lead-OFF). Finally, TONIC responses exhibited decrements in firing rate during gaps, but were rarely the most sensitive feature. Unlike results from anesthetized conditions, temporal acuity of the most sensitive units was nearly as sharp for brief as for long leading bursts. The differences in stimulus coding across pulse rates likely originate from pulse rate-dependent variations in adaptation in the auditory nerve. Two marked differences from responses to acoustic stimulation were: first, Trail-ON responses to 4,069 pps trains encoded substantially shorter gaps than have been observed with acoustic stimuli; and second, the Lead-OFF gap coding seen for <15 ms gaps in 254 pps stimuli is not seen in responses to sounds. The current results may help

  7. Suppressing Autocorrelation Sidelobes of LFM Pulse Trains with Genetic Algorithm

    Institute of Scientific and Technical Information of China (English)

    WANG Peng; MENG Huadong; WANG Xiqin

    2008-01-01

    Modulations and diversities, including the Costas-ordered stepped-frequency and nonlinear stepped-frequency waveforms are widely used in linear frequency modulation (LFM) pulse trains to reduce the relatively high autocorrelation function (ACF) sidelobes. An efficient method was developed to optimize the interpulse frequency modulation to remove most of the ACF sidelobes about the mainlobe peak, with only a small increase in the mainlobe width. The genetic algorithm is used to solve the nonlinear optimization problem to find the interpulse frequency modulation sequence. The effects on the ACF sidelobes suppres-sion and mainlobe widening are studied. The results show that the new design is supedor to the corre-sponding stepped-frequency LFM signal and weighted stepped-frequency LFM signal in the terms of the ACF sidelobes reduction and mainlobe spread.

  8. Reaction time to changes in the tempo of acoustic pulse trains.

    Science.gov (United States)

    Smith, R. P.; Warm, J. S.; Westendorf, D. H.

    1973-01-01

    Investigation of the ability of human observers to detect accelerations and decelerations in the rate of presentation of pulsed stimuli, i.e., changes in the tempo of acoustic pulse trains. Response times to accelerations in tempo were faster than to decelerations. Overall speed of response was inversely related to the pulse repetition rate.

  9. Pulse train amplification and regeneration based on semiconductor quantum dots waveguide

    DEFF Research Database (Denmark)

    Chen, Yaohui; Öhman, Filip; Mørk, Jesper

    2008-01-01

    We numerical analyze pulse train amplification up to 200 Gbit/s in quantum dot amplifiers and present regeneration properties with saturable absorber based on semiconductor quantum dot waveguides.......We numerical analyze pulse train amplification up to 200 Gbit/s in quantum dot amplifiers and present regeneration properties with saturable absorber based on semiconductor quantum dot waveguides....

  10. Tunable CO2 laser system with subnanosecond-pulse-train output

    Science.gov (United States)

    Kimura, W. D.

    2017-02-01

    A CO2 laser system has been demonstrated that generates a train of subnanosecond pulses tunable over the P and R branches of the CO2 laser spectrum at 9-11 μm. It utilizes optical free induction decay to generate a single 100-ps laser pulse from a tunable transverse-excited-atmospheric CO2 laser. This laser pulse is injection-seeded into a high-pressure CO2 oscillator whose output consists of a train of amplified 100-ps pulses with maximum pulse energy of 30 mJ, corresponding to a peak power of 300 MW. The 100-ps, tunable, infrared laser pulses are needed for a new technique to remotely detect atmospheric gaseous molecules, which relies on the train of CO2 laser pulses selectively exciting the target molecules whose presence is then revealed using a separate terahertz probe beam.

  11. High-speed pulse train amplification in semiconductor optical amplifiers with optimized bias current.

    Science.gov (United States)

    Xia, Mingjun; Ghafouri-Shiraz, H; Hou, Lianping; Kelly, Anthony E

    2017-02-01

    In this paper, we have experimentally investigated the optimized bias current of semiconductor optical amplifiers (SOAs) to achieve high-speed input pulse train amplification with high gain and low distortion. Variations of the amplified output pulse duration with the amplifier bias currents have been analyzed and, compared to the input pulse duration, the amplified output pulse duration is broadened. As the SOA bias current decreases from the high level (larger than the saturated bias current) to the low level, the broadened pulse duration of the amplified output pulse initially decreases slowly and then rapidly. Based on the analysis, an optimized bias current of SOA for high-speed pulse train amplification is introduced. The relation between the SOA optimized bias current and the parameters of the input pulse train (pulse duration, power, and repetition rate) are experimentally studied. It is found that the larger the input pulse duration, the lower the input pulse power or a higher repetition rate can lead to a larger SOA optimized bias current, which corresponds to a larger optimized SOA gain. The effects of assist light injection and different amplifier temperatures on the SOA optimized bias current are studied and it is found that assist light injection can effectively increase the SOA optimized bias current while SOA has a lower optimized bias current at the temperature 20°C than that at other temperatures.

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

    DEFF Research Database (Denmark)

    Misaridis, T.; Jensen, Jørgen Arendt

    2002-01-01

    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...

  13. Adjustable high-repetition-rate pulse trains in a passively-mode-locked fiber laser

    Science.gov (United States)

    Si Fodil, Rachid; Amrani, Foued; Yang, Changxi; Kellou, Abdelhamid; Grelu, Ph.

    2016-07-01

    We experimentally investigate multipulse regimes obtained within a passively-mode-locked fiber laser that includes a Mach-Zehnder (MZ) interferometer. By adjusting the time delay imbalance of the MZ, ultrashort pulse trains at multi-GHz repetition rates are generated. We compare the observed dynamics with high-harmonic mode locking, and show that the multi-GHz pulse trains display an inherent instability, which has been overlooked. By using a recirculation loop containing the MZ, we demonstrate a significant improvement of the pulse train stability.

  14. Secondary wavelength stabilization of unbalanced Michelson interferometers for the generation of low-jitter pulse trains.

    Science.gov (United States)

    Shalloo, R J; Corner, L

    2016-09-01

    We present a double unbalanced Michelson interferometer producing up to four output pulses from a single input pulse. The interferometer is stabilized with the Hänsch-Couillaud method using an auxiliary low power continuous wave laser injected into the interferometer, allowing the stabilization of the temporal jitter of the output pulses to 0.02 fs. Such stabilized pulse trains would be suitable for driving multi-pulse laser wakefield accelerators, and the technique could be extended to include amplification in the arms of the interferometer.

  15. Plasma Membrane Permeabilization by Trains of Ultrashort Electric Pulses

    Science.gov (United States)

    2009-01-01

    REFERENCES 1. Beebe, S.J., et al., Nanosecond Pulsed Electric Field (nsPEF) Effects on Cells and Tissues: Apoptosis Induction and Tumor Growth Inhibition...nanosecond pulsed electric field Bioelectromagnetics, 2007. 28: p. 655-663. 13. Gowrishankar, T.R. and J.C. Weaver, Electrical behavior and pore... electric field (nsPEF). Bioelectromagnetics, 2007. 28: p. 655- 663. 19. Nuccitelli, R., et al., A new pulsed electric field therapy for melanoma disrupts

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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 (D1(K)) or with N interleaved equally spaced pulses τp in each rotor period, globally also extending over K rotor periods (D(N)(K)). The excitation profile of D(N)(K) scheme is a comb of rf-spikelets with Nν(R)=N/T(R) spacing from the carrier frequency, and a width of each spikelet inversely proportional to the length, KT(R), of D(N)(K) scheme. Since the individual pulse lengths, τp, are typically of a few hundreds of ns, D(N)(K) 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/(KT(R)), D(N)(K) 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 D1(K) train have a linearly cumulative effect, so that the total nutation angle is θ(tot)=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 D(N)(K) with N>1, only spinning sidebands separated by intervals of Nν(R) with respect to the carrier frequency are observed as if the effective spinning speed was Nν(R). 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

  18. Generation of low-timing-jitter femtosecond pulse trains with 2 GHz repetition rate via external repetition rate multiplication.

    Science.gov (United States)

    Chen, Jian; Sickler, Jason W; Fendel, Peter; Ippen, Erich P; Kärtner, Franz X; Wilken, Tobias; Holzwarth, Ronald; Hänsch, Theodor W

    2008-05-01

    Generation of low-timing-jitter 150 fs pulse trains at 1560 nm with 2 GHz repetition rate is demonstrated by locking a 200 MHz fundamental polarization additive-pulse mode-locked erbium fiber laser to high-finesse external Fabry-Perot cavities. The timing jitter and relative intensity noise of the repetition-rate multiplied pulse train are investigated.

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

    Institute of Scientific and Technical Information of China (English)

    Zhong Xian-Qiong; Xiang An-Ping

    2009-01-01

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

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    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...

  3. Correction of group refraction index based on pulse trains interference

    Science.gov (United States)

    Wei, Dong; Aketagawa, Masato

    2015-02-01

    We propose a new concept for an unconventional type of two-color method for interferometry-based length measurements based on the adjacent pulse repetition interval length (APRIL), which is the physical length associated with the pulse repetition period. We demonstrate by numerical simulations that if the wavelength-based two-color method can eliminate the inhomogeneous disturbance of effects caused by the phase refractive index, then the APRIL-based two-color method can eliminate the air turbulence of errors induced by the group refractive index. We show that our analysis will benefit the pulse-laser-based two-color method, which secures traceability to the definition of the meter.

  4. Forward Masking in Cochlear Implant Users: Electrophysiological and Psychophysical Data Using Pulse Train Maskers.

    Science.gov (United States)

    Adel, Youssef; Hilkhuysen, Gaston; Noreña, Arnaud; Cazals, Yves; Roman, Stéphane; Macherey, Olivier

    2017-06-01

    Electrical stimulation of auditory nerve fibers using cochlear implants (CI) shows psychophysical forward masking (pFM) up to several hundreds of milliseconds. By contrast, recovery of electrically evoked compound action potentials (eCAPs) from forward masking (eFM) was shown to be more rapid, with time constants no greater than a few milliseconds. These discrepancies suggested two main contributors to pFM: a rapid-recovery process due to refractory properties of the auditory nerve and a slow-recovery process arising from more central structures. In the present study, we investigate whether the use of different maskers between eCAP and psychophysical measures, specifically single-pulse versus pulse train maskers, may have been a source of confound.In experiment 1, we measured eFM using the following: a single-pulse masker, a 300-ms low-rate pulse train masker (LTM, 250 pps), and a 300-ms high-rate pulse train masker (HTM, 5000 pps). The maskers were presented either at same physical current (Φ) or at same perceptual (Ψ) level corresponding to comfortable loudness. Responses to a single-pulse probe were measured for masker-probe intervals ranging from 1 to 512 ms. Recovery from masking was much slower for pulse trains than for the single-pulse masker. When presented at Φ level, HTM produced more and longer-lasting masking than LTM. However, results were inconsistent when LTM and HTM were compared at Ψ level. In experiment 2, masked detection thresholds of single-pulse probes were measured using the same pulse train masker conditions. In line with our eFM findings, masked thresholds for HTM were higher than those for LTM at Φ level. However, the opposite result was found when the pulse trains were presented at Ψ level.Our results confirm the presence of slow-recovery phenomena at the level of the auditory nerve in CI users, as previously shown in animal studies. Inconsistencies between eFM and pFM results, despite using the same masking conditions, further

  5. Multi-rate soliton pulse train generator based on novel fiber optic components

    Science.gov (United States)

    Sova, Raymond Michael

    As data rates for communication, signal processing, and optical sensing systems increase beyond 50 Gb/sec, ultra-fast optical pulse train generators will play a key role in their development. In this research, an all-fiber optical soliton pulse train generator is developed that operates at discrete rates from 50 to 400 Gb/sec with stable subpicosecond pulses. It is based on the following three novel fiber optic components: (1) all-fiber birefringence filter, (2) dual-wavelength fiber ring laser and (3) fiber-based soliton pulse train generation and compression stage. A multi-segment birefringence comb filter is developed to provide discrete tuning of the free spectral range from 0.8 to 3.2 nm and continuous tuning of the absolute position of the transmission peaks over the entire free spectral range. Two, three and four segment filters are constructed and implemented in Lyot and Lyot-Sagnac filter configurations to demonstrate the tuning properties and provide compound filters for use in the dual-wavelength fiber ring laser. Theoretical transmission functions are derived for two-segment filters. The experimental results are in excellent agreement with theoretical models based on the Jones matrix technique. The dual-wavelength laser consists of a PM amplifier, the tunable birefringence filter and a high-Q filter based on saturable absorber properties of un-pumped Erbium-doped fiber. Tunable compound birefringence filters are designed to operate the dual-wavelength laser over the entire erbium amplifier gain region (1530 to 1565 nm) with discrete tuning of the channel separation from 0.8 to 3.2 nm. Stable tunable dual-wavelength single-longitudinal mode operation is demonstrated and initial laser properties such as dual-relaxation oscillations, laser linewidth, polarization, and multi-wavelength stability are characterized. Induced modulation instability in optical fiber is used to generate pulse trains from the fiber ring laser output signal. Through modeling, the

  6. Compact KGd(WO4)2 picosecond pulse-train synchronously pumped broadband Raman laser.

    Science.gov (United States)

    Gao, Xiao Qiang; Long, Ming Liang; Meng, Chen

    2016-08-20

    We demonstrate an efficient approach to realizing an extra-cavity, synchronously pumped, stimulated Raman cascaded process under low repetition frequency (1 kHz) pump conditions. We also construct a compact KGd(WO4)2 (KGW) crystal picosecond Raman laser that has been configured as the developed method. A pulse-train green laser pumped the corresponding 70 mm long KGW crystal Raman cavity. The pulse train contains six pulses, about 800 ps separated, for every millisecond; thus, it can realize synchronous pumping between pump pulse and the pumped Raman cavity. The investigated system produced a collinear Raman laser output that includes six laser lines covering the 532 to 800 nm spectra. This is the first report on an all-solid-state, high-average-power picosecond collinear multi-wavelength (more than three laser components) laser to our knowledge. This method has never been reported on before in the synchronously pumped stimulated Raman scattering (SRS) realm.

  7. The neuronal response to electrical constant-amplitude pulse train stimulation: additive Gaussian noise.

    Science.gov (United States)

    Matsuoka, A J; Abbas, P J; Rubinstein, J T; Miller, C A

    2000-11-01

    Experimental results from humans and animals show that electrically evoked compound action potential (EAP) responses to constant-amplitude pulse train stimulation can demonstrate an alternating pattern, due to the combined effects of highly synchronized responses to electrical stimulation and refractory effects (Wilson et al., 1994). One way to improve signal representation is to reduce the level of across-fiber synchrony and hence, the level of the amplitude alternation. To accomplish this goal, we have examined EAP responses in the presence of Gaussian noise added to the pulse train stimulus. Addition of Gaussian noise at a level approximately -30 dB relative to EAP threshold to the pulse trains decreased the amount of alternation, indicating that stochastic resonance may be induced in the auditory nerve. The use of some type of conditioning stimulus such as Gaussian noise may provide a more 'normal' neural response pattern.

  8. Dual temporal pitch percepts from acoustic and electric amplitude-modulated pulse trains.

    Science.gov (United States)

    McKay, C M; Carlyon, R P

    1999-01-01

    Two experiments examined the perception of unmodulated and amplitude-modulated pulse trains by normally hearing listeners and cochlear implantees. Four normally hearing subjects listened to acoustic pulse trains, which were band-pass filtered between 3.9 and 5.3 kHz. Four cochlear implantees, all postlinguistically deaf users of the Mini System 22 implant, listened to current pulse trains produced at a single electrode position. In the first experiment, a set of nine loudness-balanced unmodulated stimuli with rates between 60 and 300 Hz were presented in a multidimensional scaling task. The resultant stimulus spaces for both subject groups showed a single dimension associated with the rate of the stimuli. In the second experiment, a set of ten loudness-balanced modulated stimuli was constructed, with carrier rates between 140 and 300 Hz, and modulation rates between 60 and 150 Hz. The modulation rates were integer submultiples of the carrier rates, and each modulation period consisted of one higher-intensity pulse and one or more identical lower-intensity pulses. The modulation depth of each stimulus was adjusted so that its pitch was judged to be higher or lower 50% of the time than that of an unmodulated pulse train having a rate equal to the geometric mean of the carrier and modulation rates. A multidimensional scaling task with these ten stimuli resulted in two-dimensional stimulus spaces, with dimensions corresponding to carrier and modulation rates. A further investigation with one normally hearing subject showed that the perceptual weighting of the two dimensions varied systematically with modulation depth. It was concluded that, when filtered appropriately, acoustic pulse trains can be used to produce percepts in normal listeners that share common features with those experienced by subjects listening through one channel of a cochlear implant, and that the central auditory system can extract two temporal patterns arising from the same cochlear location.

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

    Institute of Scientific and Technical Information of China (English)

    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.

  10. Observation of propagating femtosecond light pulse train generated by an integrated array illuminator as a spatially and temporally continuous motion picture.

    Science.gov (United States)

    Yamagiwa, Masatomo; Komatsu, Aya; Awatsuji, Yasuhiro; Kubota, Toshihiro

    2005-05-02

    We observed a propagating femtosecond light pulse train generated by an integrated array illuminator as a spatially and temporally continuous motion picture. To observe the light pulse train propagating in air, light-in-flight holography is applied. The integrated array illuminator is an optical device for generating an ultrashort light pulse train from a single ultrashort pulse. The experimentally obtained pulse width and pulse interval were 130 fs and 19.7 ps, respectively. A back-propagating femtosecond light pulse train, which is the -2 order diffracted light pulse from the array illuminator and which is difficult to observe using conventional methods, was observed.

  11. Laser pulse trains for controlling excited state dynamics of adenine in water.

    Science.gov (United States)

    Petersen, Jens; Wohlgemuth, Matthias; Sellner, Bernhard; Bonačić-Koutecký, Vlasta; Lischka, Hans; Mitrić, Roland

    2012-04-14

    We investigate theoretically the control of the ultrafast excited state dynamics of adenine in water by laser pulse trains, with the aim to extend the excited state lifetime and to suppress nonradiative relaxation processes. For this purpose, we introduce the combination of our field-induced surface hopping method (FISH) with the quantum mechanical-molecular mechanical (QM/MM) technique for simulating the laser-driven dynamics in the condensed phase under explicit inclusion of the solvent environment. Moreover, we employ parametric pulse shaping in the frequency domain in order to design simplified laser pulse trains allowing to establish a direct link between the pulse parameters and the controlled dynamics. We construct pulse trains which achieve a high excitation efficiency and at the same time keep a high excited state population for a significantly extended time period compared to the uncontrolled dynamics. The control mechanism involves a sequential cycling of the population between the lowest and higher excited states, thereby utilizing the properties of the corresponding potential energy surfaces to avoid conical intersections and thus to suppress the nonradiative decay to the ground state. Our findings provide a means to increase the fluorescence yield of molecules with an intrinsically very short excited state lifetime, which can lead to novel applications of shaped laser fields in the context of biosensing.

  12. Effects of acoustic noise on the auditory nerve compound action potentials evoked by electric pulse trains.

    Science.gov (United States)

    Nourski, Kirill V; Abbas, Paul J; Miller, Charles A; Robinson, Barbara K; Jeng, Fuh-Cherng

    2005-04-01

    This study investigated the effects of acoustic noise on the auditory nerve compound action potentials in response to electric pulse trains. Subjects were adult guinea pigs, implanted with a minimally invasive electrode to preserve acoustic sensitivity. Electrically evoked compound action potentials (ECAP) were recorded from the auditory nerve trunk in response to electric pulse trains both during and after the presentation of acoustic white noise. Simultaneously presented acoustic noise produced a decrease in ECAP amplitude. The effect of the acoustic masker on the electric probe was greatest at the onset of the acoustic stimulus and it was followed by a partial recovery of the ECAP amplitude. Following cessation of the acoustic noise, ECAP amplitude recovered over a period of approximately 100-200 ms. The effects of the acoustic noise were more prominent at lower electric pulse rates (interpulse intervals of 3 ms and higher). At higher pulse rates, the ECAP adaptation to the electric pulse train alone was larger and the acoustic noise, when presented, produced little additional effect. The observed effects of noise on ECAP were the greatest at high electric stimulus levels and, for a particular electric stimulus level, at high acoustic noise levels.

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

    OpenAIRE

    Kan WU; 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.

  14. Generation, compression, and propagation of pulse trains in the nonlinear Schrödinger equation with distributed coefficients.

    Science.gov (United States)

    Wang, Luyun; Li, Lu; Li, Zhonghao; Zhou, Guosheng; Mihalache, Dumitru

    2005-09-01

    The generalized nonlinear Schrödinger model with distributed dispersion, nonlinearity, and gain or loss is considered and the explicit, analytical solutions describing the dynamics of bright solitons on a continuous-wave background are obtained in quadratures. Then, the generation, compression, and propagation of pulse trains are discussed in detail. The numerical results show that solitons can be compressed by choosing the appropriate control fiber system, and pulse trains generated by modulation instability can propagate undistorsted along fibers with distributed parameters by controlling appropriately the energy of each pulse in the pulse train.

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

    Institute of Scientific and Technical Information of China (English)

    YE Cun-Yun

    2004-01-01

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

  16. Oscillatory pulses and wave trains in a bistable reaction-diffusion system with cross diffusion.

    Science.gov (United States)

    Zemskov, Evgeny P; Tsyganov, Mikhail A; Horsthemke, Werner

    2017-01-01

    We study waves with exponentially decaying oscillatory tails in a reaction-diffusion system with linear cross diffusion. To be specific, we consider a piecewise linear approximation of the FitzHugh-Nagumo model, also known as the Bonhoeffer-van der Pol model. We focus on two types of traveling waves, namely solitary pulses that correspond to a homoclinic solution, and sequences of pulses or wave trains, i.e., a periodic solution. The effect of cross diffusion on wave profiles and speed of propagation is analyzed. We find the intriguing result that both pulses and wave trains occur in the bistable cross-diffusive FitzHugh-Nagumo system, whereas only fronts exist in the standard bistable system without cross diffusion.

  17. Selective triggering of phase change in dielectrics by femtosecond pulse trains based on electron dynamics control

    Institute of Scientific and Technical Information of China (English)

    Xu Chuan-Cai; Jiang Lan; Leng Ni; Liu Peng-Jun

    2013-01-01

    In this study we experimentally reveal that the phase change mechanism can be selectively triggered by shaping femtosecond pulse trains based on electron dynamics control (EDC),including manipulation of excitations,ionizations,densities,and temperatures of electrons.By designing the pulse energy distribution to adjust the absorptions,excitations,ionizations,and recombinations of electrons,the dominant phase change mechanism experiences transition from nonthermal to thermal process.This phenomenon is observed in quadruple,triple,and double pulses per train ablation of fused silica separately.This opens up possibilities for controlling phase change mechanisms by EDC,which is of great significance in laser processing of dielectrics and fabrication of integrated nano-and micro-optical devices.

  18. Train of high-power femtosecond pulses: Probe wave in a gas of prepared atoms

    Science.gov (United States)

    Muradyan, Gevorg; Muradyan, Atom Zh.

    2009-09-01

    We present a method for generating a regular train of ultrashort optical pulses in a prepared two-level medium. The train develops from incident monochromatic probe radiation traveling in a medium of atoms, which are in a quantum mechanical superposition of dressed internal states. In the frame of linear theory for the probe radiation, the energy of individual pulses is an exponentially growing function of atom density and of interaction cross section. Pulse repetition rate is determined by the pump field’s generalized Rabi frequency and can be around 1 THz and greater. We also show that the terms, extra to the dipole approximation, endow the gas by a new property: nonsaturating dependence of refractive index on dressing monochromatic field intensity. Contribution of these nonsaturating terms can be compatible with the main dipole approximation term contribution in the wavelength region of about ten micrometers (the range of CO2 laser) or larger.

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

    CERN Document Server

    Quinlan, Franklyn; 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 orders-of-magnitude imbalance between the shot noise-limited amplitude and phase noise of photonically generated microwave carriers. It is also shown that only by accounting for spectral correlations can shot noise be equated with the fundamental quantum limit in the detection of optical pulse-to-pulse timing jitter.

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

    Directory of Open Access Journals (Sweden)

    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.

  1. Pulse

    Science.gov (United States)

    ... resting for at least 10 minutes. Take the exercise heart rate while you are exercising. ... pulse rate can help determine if the person's heart is pumping. Pulse ... rate gives information about your fitness level and health.

  2. Optimized Saturation Pulse Train for Human First-Pass Myocardial Perfusion Imaging at 7T

    Science.gov (United States)

    Tao, Yuehui; Hess, Aaron T; Keith, Graeme A; Rodgers, Christopher T; Liu, Alexander; Francis, Jane M; Neubauer, Stefan; Robson, Matthew D

    2015-01-01

    Purpose To investigate whether saturation using existing methods developed for 3T imaging is feasible for clinical perfusion imaging at 7T, and to propose a new design of saturation pulse train for first-pass myocardial perfusion imaging at 7T. Methods The new design of saturation pulse train consists of four hyperbolic-secant (HS8) radiofrequency pulses, whose peak amplitudes are optimized for a target range of static and transmit field variations and radiofrequency power deposition restrictions measured in the myocardium at 7T. The proposed method and existing methods were compared in simulation, phantom, and in vivo experiments. Results In healthy volunteer experiments without contrast agent, average saturation efficiency with the proposed method was 97.8%. This is superior to results from the three previously published methods at 86/95/90.8%. The first series of human first-pass myocardial perfusion images at 7T have been successfully acquired with the proposed method. Conclusion Existing saturation methods developed for 3T imaging are not optimal for perfusion imaging at 7T. The proposed new design of saturation pulse train can saturate effectively, and with this method first-pass myocardial perfusion imaging is feasible in humans at 7T. Magn Reson Med 73:1450–1456, 2015. © 2014 The Authors. Magnetic Resonance in Medicine Published by Wiley Periodicals, Inc. on behalf of International Society of Medicine in Resonance. PMID:24753130

  3. Simultaneous ultrafast optical pulse train bursts generation and shaping based on Fourier series developments using superimposed fiber Bragg gratings.

    Science.gov (United States)

    García-Muñoz, Víctor; Preciado, Miguel A; Muriel, Miguel A

    2007-08-20

    We propose an all-fiber method for the generation of ultrafast shaped pulse train bursts from a single pulse based on Fourier Series Developments (FDSs). The implementation of the FSD based filter only requires the use of a very simple non apodized Superimposed Fiber Bragg Grating (S-FBG) for the generation of the Shaped Output Pulse Train Burst (SOPTB). In this approach, the shape, the period and the temporal length of the generated SOPTB have no dependency on the input pulse rate.

  4. Quasi-phase-matching high harmonic generation using trains of pulses produced using an array of birefringent plates.

    Science.gov (United States)

    O'Keeffe, Kevin; Robinson, Tom; Hooker, Simon M

    2012-03-12

    Quasi-phase-matched high harmonic generation using trains of up to 8 counter-propagating pulses is explored. For trains of up to 4 pulses the measured enhancement of the harmonic signal scales with the number of pulses N as (N + 1)², as expected. However, for trains with N > 4, no further enhancement of the harmonic signal is observed. This effect is ascribed to changes of the coherence length Lc within the generating medium. Techniques for overcoming the variation of Lc are discussed. The pressure dependence of quasi-phase-matching is investigated and the switch from true-phase-matching to quasi-phase-matching is observed.

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

    Science.gov (United States)

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

    2017-04-01

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

  6. Method to generate a pulse train of few-cycle coherent radiation

    Science.gov (United States)

    Garcia, Bryant; Hemsing, Erik; Raubenheimer, Tor; Campbell, Lawrence T.; McNeil, Brian W. J.

    2016-09-01

    We develop a method to generate a long pulse train of few-cycle coherent radiation by modulating an electron beam with a high power laser. The large energy modulation disperses the beam in a radiating undulator and leads to the production of phase-locked few-cycle coherent radiation pulses. These pulses are produced at a high harmonic of the modulating laser, and are longitudinally separated by the modulating laser wavelength. We discuss an analytical model for this scheme and investigate the temporal and spectral properties of this radiation. This model is compared with numerical simulation results using the unaveraged code Puffin. We examine various harmful effects and how they might be avoided, as well as a possible experimental realization of this scheme.

  7. Method to generate a pulse train of few-cycle coherent radiation

    Directory of Open Access Journals (Sweden)

    Bryant Garcia

    2016-09-01

    Full Text Available We develop a method to generate a long pulse train of few-cycle coherent radiation by modulating an electron beam with a high power laser. The large energy modulation disperses the beam in a radiating undulator and leads to the production of phase-locked few-cycle coherent radiation pulses. These pulses are produced at a high harmonic of the modulating laser, and are longitudinally separated by the modulating laser wavelength. We discuss an analytical model for this scheme and investigate the temporal and spectral properties of this radiation. This model is compared with numerical simulation results using the unaveraged code Puffin. We examine various harmful effects and how they might be avoided, as well as a possible experimental realization of this scheme.

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

    Institute of Scientific and Technical Information of China (English)

    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.

  9. Subwavelength ripples adjustment based on electron dynamics control by using shaped ultrafast laser pulse trains.

    Science.gov (United States)

    Jiang, Lan; Shi, Xuesong; Li, Xin; Yuan, Yanping; Wang, Cong; Lu, Yongfeng

    2012-09-10

    This study reveals that the periods, ablation areas and orientations of periodic surface structures (ripples) in fused silica can be adjusted by using designed femtosecond (fs) laser pulse trains to control transient localized electron dynamics and corresponding material properties. By increasing the pulse delays from 0 to 100 fs, the ripple periods are changed from ~550 nm to ~255 nm and the orientation is rotated by 90°. The nearwavelength/subwavelength ripple periods are close to the fundamental/second-harmonic wavelengths in fused silica respectively. The subsequent subpulse of the train significantly impacts free electron distributions generated by the previous subpulse(s), which might influence the formation mechanism of ripples and the surface morphology.

  10. Quantum control of electron wave packets in bound molecules by trains of half-cycle pulses

    Energy Technology Data Exchange (ETDEWEB)

    Persson, Emil; Pichler, Markus; Wachter, Georg; Hisch, Thomas; Burgdoerfer, Joachim; Graefe, Stefanie [Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstr. 8-10, A-1040 Vienna (Austria); Jakubetz, Werner [Institute for Theoretical Chemistry, University of Vienna, Waehringerstr. 38, A-1090 Vienna (Austria)

    2011-10-15

    We investigate protocols for transient localization of electrons in homodiatomic molecules, as well as permanent localization via population inversion in polar molecules. By examining three different model systems with one electronic and one nuclear degree of freedom, we identify mechanisms leading to control over the localization of the electronic wave packets. We show that electronic states dressed by the quasi-dc component of the train of half-cycle pulses steer the combined electronic and nuclear motion toward the targeted state.

  11. Cramer-Rao Bounds and Coherence Performance Analysis for Next Generation Radar with Pulse Trains

    Directory of Open Access Journals (Sweden)

    Ning Zhang

    2013-04-01

    Full Text Available We study the Cramer-Rao bounds of parameter estimation and coherence performance for the next generation radar (NGR. In order to enhance the performance of NGR, the signal model of NGR with master-slave architecture based on a single pulse is extended to the case of pulse trains, in which multiple pulses are emitted from all sensors and then integrated spatially and temporally in a unique master sensor. For the MIMO mode of NGR where orthogonal waveforms are emitted, we derive the closed-form Cramer-Rao bound (CRB for the estimates of generalized coherence parameters (GCPs, including the time delay differences, total phase differences and Doppler frequencies with respect to different sensors. For the coherent mode of NGR where the coherent waveforms are emitted after pre-compensation using the estimates of GCPs, we develop a performance bound of signal-to-noise ratio (SNR gain for NGR based on the aforementioned CRBs, taking all the estimation errors into consideration. It is shown that greatly improved estimation accuracy and coherence performance can be obtained with pulse trains employed in NGR. Numerical examples demonstrate the validity of the theoretical results.

  12. Pulse-train Stimulation of Primary Somatosensory Cortex Blocks Pain Perception in Tail Clip Test.

    Science.gov (United States)

    Lee, Soohyun; Hwang, Eunjin; Lee, Dongmyeong; Choi, Jee Hyun

    2017-04-01

    Human studies of brain stimulation have demonstrated modulatory effects on the perception of pain. However, whether the primary somatosensory cortical activity is associated with antinociceptive responses remains unknown. Therefore, we examined the antinociceptive effects of neuronal activity evoked by optogenetic stimulation of primary somatosensory cortex. Optogenetic transgenic mice were subjected to continuous or pulse-train optogenetic stimulation of the primary somatosensory cortex at frequencies of 15, 30, and 40 Hz, during a tail clip test. Reaction time was measured using a digital high-speed video camera. Pulse-train optogenetic stimulation of primary somatosensory cortex showed a delayed pain response with respect to a tail clip, whereas no significant change in reaction time was observed with continuous stimulation. In response to the pulse-train stimulation, video monitoring and local field potential recording revealed associated paw movement and sensorimotor rhythms, respectively. Our results show that optogenetic stimulation of primary somatosensory cortex at beta and gamma frequencies blocks transmission of pain signals in tail clip test.

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

    Science.gov (United States)

    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.

  14. Polarization-independent etching of fused silica based on electrons dynamics control by shaped femtosecond pulse trains for microchannel fabrication.

    Science.gov (United States)

    Yan, X; Jiang, L; Li, X; Zhang, K; Xia, B; Liu, P; Qu, L; Lu, Y

    2014-09-01

    We propose an approach to realize polarization-independent etching of fused silica by using temporally shaped femtosecond pulse trains to control the localized transient electrons dynamics. Instead of nanograting formation using traditional unshaped pulses, for the pulse delay of pulse trains larger than 1 ps, coherent field-vector-related coupling is not possible and field orientation is lost. The exponential growth of the periodic structures is interrupted. In this case, disordered and interconnected nanostructures are formed, which is probably the main reason of etching independence on the laser polarization. As an application example, square-wave-shaped and arc-shaped microchannels are fabricated by using pulse trains to demonstrate the advantage of the proposed method in fabricating high-aspect-ratio and three-dimensional microchannels.

  15. Generating quasi-single-cycle THz pulse from frequency-chirped electron bunch train and a tapered undulator

    Institute of Scientific and Technical Information of China (English)

    Zhuoran Ma; Zhe Wang; Feichao Fu; Rui Wang; Dao Xiang

    2016-01-01

    We propose a proof-of-principle experiment to test a new scheme to produce a single-cycle radiation pulse in free-electron lasers(FELs). Here, a few α-BBO crystals will be first used to produce an equally spaced laser pulse train.Then, the laser pulse train illuminates the cathode to produce a frequency-chirped electron bunch train in a photocathode rf gun. Finally, the frequency-chirped electron bunch train passes through a tapered undulator to produce a quasi-single-cycle THz pulse. This experiment should allow comparison and confirmation of predictive models and scaling laws, and the preliminary experimental results will also be discussed.

  16. Predicting the threshold of pulse-train electrical stimuli using a stochastic auditory nerve model: the effects of stimulus noise.

    Science.gov (United States)

    Xu, Yifang; Collins, Leslie M

    2004-04-01

    The incorporation of low levels of noise into an electrical stimulus has been shown to improve auditory thresholds in some human subjects (Zeng et al., 2000). In this paper, thresholds for noise-modulated pulse-train stimuli are predicted utilizing a stochastic neural-behavioral model of ensemble fiber responses to bi-phasic stimuli. The neural refractory effect is described using a Markov model for a noise-free pulse-train stimulus and a closed-form solution for the steady-state neural response is provided. For noise-modulated pulse-train stimuli, a recursive method using the conditional probability is utilized to track the neural responses to each successive pulse. A neural spike count rule has been presented for both threshold and intensity discrimination under the assumption that auditory perception occurs via integration over a relatively long time period (Bruce et al., 1999). An alternative approach originates from the hypothesis of the multilook model (Viemeister and Wakefield, 1991), which argues that auditory perception is based on several shorter time integrations and may suggest an NofM model for prediction of pulse-train threshold. This motivates analyzing the neural response to each individual pulse within a pulse train, which is considered to be the brief look. A logarithmic rule is hypothesized for pulse-train threshold. Predictions from the multilook model are shown to match trends in psychophysical data for noise-free stimuli that are not always matched by the long-time integration rule. Theoretical predictions indicate that threshold decreases as noise variance increases. Theoretical models of the neural response to pulse-train stimuli not only reduce calculational overhead but also facilitate utilization of signal detection theory and are easily extended to multichannel psychophysical tasks.

  17. Simulation of the electrically stimulated cochlear neuron: modeling adaptation to trains of electric pulses.

    Science.gov (United States)

    Woo, Jihwan; Miller, Charles A; Abbas, Paul J

    2009-05-01

    The Hodgkin-Huxley (HH) model does not simulate the significant changes in auditory nerve fiber (ANF) responses to sustained stimulation that are associated with neural adaptation. Given that the electric stimuli used by cochlear prostheses can result in adapted responses, a computational model incorporating an adaptation process is warranted if such models are to remain relevant and contribute to related research efforts. In this paper, we describe the development of a modified HH single-node model that includes potassium ion ( K(+)) concentration changes in response to each action potential. This activity-related change results in an altered resting potential, and hence, excitability. Our implementation of K(+)-related changes uses a phenomenological approach based upon K(+) accumulation and dissipation time constants. Modeled spike times were computed using repeated presentations of modeled pulse-train stimuli. Spike-rate adaptation was characterized by rate decrements and time constants and compared against ANF data from animal experiments. Responses to relatively low (250 pulse/s) and high rate (5000 pulse/s) trains were evaluated and the novel adaptation model results were compared against model results obtained without the adaptation mechanism. In addition to spike-rate changes, jitter and spike intervals were evaluated and found to change with the addition of modeled adaptation. These results provide one means of incorporating a heretofore neglected (although important) aspect of ANF responses to electric stimuli. Future studies could include evaluation of alternative versions of the adaptation model elements and broadening the model to simulate a complete axon, and eventually, a spatially realistic model of the electrically stimulated nerve within extracochlear tissues.

  18. Transient absorption lineshapes in a dense, laser-dressed Helium target probed by attosecond pulse trains

    Science.gov (United States)

    Liao, Chen-Ting; Timmers, Henry; Sandhu, Arvinder

    2014-05-01

    Attosecond transient absorption is an emerging time-resolved spectroscopic technique to explore electron dynamics in atoms and molecules. In this experimental study, we used extreme ultraviolet (XUV) attosecond pulse trains (APTs) in energy range of 20-25 eV to probe the transient excited-state absorption of an optically thick Helium gas sample under the influence of moderately strong (1-3 TW/cm2) , infrared (IR), femtosecond pump pulse. We found that the resonant absorption lineshapes for Helium 1s2p, 1snp, and continuum states show rich dynamics, evolving between Lorenzian and Fano profiles with phases imposed by IR laser pulse and multi-channel quantum-path interference. Both AC Stark shifts and light-induced states were studied as a function of pump-probe delay and IR intensity. By changing the Helium gas density, we observed the lineshape modification due to the macroscopic propagation effects, which is usually not included in the single-atom response model. We found that the 13th and 15th high harmonics of XUV produce two coupled polarizations, and the relative coherence between these two polarizations changes the absorption even when the IR pulse arrives after a long time (about 500 fs) after the XUV. This work is supported by NSF Grant No. PHY-0955274.

  19. Increasing sensitivity of pulse EPR experiments using echo train detection schemes

    Science.gov (United States)

    Mentink-Vigier, F.; Collauto, A.; Feintuch, A.; Kaminker, I.; Tarle, V.; Goldfarb, D.

    2013-11-01

    Modern pulse EPR experiments are routinely used to study the structural features of paramagnetic centers. They are usually performed at low temperatures, where relaxation times are long and polarization is high, to achieve a sufficient Signal/Noise Ratio (SNR). However, when working with samples whose amount and/or concentration are limited, sensitivity becomes an issue and therefore measurements may require a significant accumulation time, up to 12 h or more. As the detection scheme of practically all pulse EPR sequences is based on the integration of a spin echo - either primary, stimulated or refocused - a considerable increase in SNR can be obtained by replacing the single echo detection scheme by a train of echoes. All these echoes, generated by Carr-Purcell type sequences, are integrated and summed together to improve the SNR. This scheme is commonly used in NMR and here we demonstrate its applicability to a number of frequently used pulse EPR experiments: Echo-Detected EPR, Davies and Mims ENDOR (Electron-Nuclear Double Resonance), DEER (Electron-Electron Double Resonance|) and EDNMR (Electron-Electron Double Resonance (ELDOR)-Detected NMR), which were combined with a Carr-Purcell-Meiboom-Gill (CPMG) type detection scheme at W-band. By collecting the transient signal and integrating a number of refocused echoes, this detection scheme yielded a 1.6-5 folds SNR improvement, depending on the paramagnetic center and the pulse sequence applied. This improvement is achieved while keeping the experimental time constant and it does not introduce signal distortion.

  20. Energy iteration model research of DCM Buck converter with multilevel pulse train technique

    Science.gov (United States)

    Qin, Ming; Li, Xiang

    2017-08-01

    According as the essence of switching converter is the nature of energy, the energy iteration model of the Multilevel Pulse Train (MPT) technique is studied in this paper. The energy iteration model of DCM Buck converter with MPT technique can reflect the control law and excellent transient performance of the MPT technique. The iteration relation of energy transfer in switching converter is discussed. The structure and operation principle of DCM Buck converter with MPT technique is introduced and the energy iteration model of this converter is set up. The energy tracks of MPT-control Buck converter and PT converter is researched and compared to show that the ratio of steady-state control pulse satisfies the expectation for the MPT technique and the MPT-controlled switching converter has much lower output voltage ripple than the PT converter.

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

    CERN Document Server

    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.

  2. Effects of stimulus level and rate on psychophysical thresholds for interleaved pulse trains in cochlear implants.

    Science.gov (United States)

    Hughes, Michelle L; Goehring, Jenny L; Baudhuin, Jacquelyn L; Schmid, Kendra K

    2016-10-01

    This study examined channel interactions using interleaved pulse trains to assess masking and potential facilitative effects in cochlear-implant recipients using clinically relevant stimuli. Psychophysical thresholds were measured for two adjacent mid-array electrodes; one served as the masker and the other as the probe. Two rates representative of those found in present-day strategies were tested: 1700 and 3400 pulses per second per channel. Four masker levels ranging from sub-threshold to loud-but-comfortable were tested. It was hypothesized that low-level maskers would produce facilitative effects, shifting to masking effects at high levels, and that faster rates would yield smaller masking effects due to greater stochastic neural firing patterns. Twenty-nine ears with Cochlear or Advanced Bionics devices were tested. High-level maskers produced more masking than low-level maskers, as expected. Facilitation was not observed for sub-threshold or threshold-level maskers in most cases. High masker levels yielded reduced probe thresholds for two Advanced Bionics subjects. This was partly eliminated with a longer temporal offset between each masker-probe pulse pair, as was used with Cochlear subjects. These findings support the use of temporal gaps between stimulation of subsequent electrodes to reduce channel interactions.

  3. Development of ultrasonic pulse-train Doppler method for velocity profile and flowrate measurement

    Science.gov (United States)

    Wada, Sanehiro; Furuichi, Noriyuki; Shimada, Takashi

    2016-11-01

    We present a novel technique for measuring the velocity profile and flowrate in a pipe. This method, named the ultrasonic pulse-train Doppler method (UPTD), has the advantages of expanding the velocity range and setting the smaller measurement volume with low calculation and instrument costs in comparison with the conventional ultrasonic pulse Doppler method. The conventional method has limited measurement of the velocity range due to the Nyquist sampling theorem. In addition, previous reports indicate that a smaller measurement volume increases the accuracy of the measurement. In consideration of the application of the conventional method to actual flow fields, such as industrial facilities and power plants, the issues of velocity range and measurement volume are important. The UPTD algorithm, which exploits two pulses of ultrasound with a short interval and envelope detection, is proposed. Velocity profiles calculated by this algorithm were examined through simulations and excellent agreement was found in all cases. The influence of the signal-to-noise ratio (SNR) on the algorithm was also estimated. The result indicates that UPTD can measure velocity profiles with high accuracy, even under a small SNR. Experimental measurements were conducted and the results were evaluated at the national standard calibration facility of water flowrate in Japan. Every detected signal forms a set of two pulses and the enveloped line can be observed clearly. The results show that UPTD can measure the velocity profiles over the pipe diameter, even if the velocities exceed the measurable velocity range. The measured flowrates were under 0.6% and the standard deviations for all flowrate conditions were within  ±0.38%, which is the uncertainty of the flowrate measurement estimated in the previous report. In conclusion, UPTD provides superior accuracy and expansion of the velocity range.

  4. GABAergic inhibition modulates intensity sensitivity of temporally patterned pulse trains in the inferior collicular neurons in big brown bats.

    Science.gov (United States)

    Luan, Rui-Hong; Wu, Fei-Jian; Jen, Philip H-S; Sun, Xin-De

    2007-12-25

    The echolocating big brown bats (Eptesicus fuscus) emit trains of frequency-modulated (FM) biosonar signals with duration, amplitude, repetition rate, and sweep structure changing systematically during interception of their prey. In the present study, the sound stimuli of temporally patterned pulse trains at three different pulse repetition rates (PRRs) were used to mimic the sounds received during search, approach, and terminal stages of echolocation. Electrophysiological method was adopted in recordings from the inferior colliculus (IC) of midbrain. By means of iontophoretic application of bicuculline, the effect of GABAergic inhibition on the intensity sensitivity of IC neurons responding to three different PRRs of 10, 30 and 90 pulses per second (pps) was examined. The rate-intensity functions (RIFs) were acquired. The dynamic range (DR) of RIFs was considered as a criterion of intensity sensitivity. Comparing the average DR of RIFs at different PRRs, we found that the intensity sensitivity of some neurons improved, but that of other neurons decayed when repetition rate of stimulus trains increased from 10 to 30 and 90 pps. During application of bicuculline, the number of impulses responding to the different pulse trains increased under all stimulating conditions, while the DR differences of RIFs at different PRRs were abolished. The results indicate that GABAergic inhibition was involved in modulating the intensity sensitivity of IC neurons responding to pulse trains at different PRRs. Before and during bicuculline application, the percentage of changes in responses was maximal in lower stimulus intensity near to the minimum threshold (MT), and decreased gradually with the increment of stimulus intensity. This observation suggests that GABAergic inhibition contributes more effectively to the intensity sensitivity of the IC neurons responding to pulse trains at lower sound level.

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

    Directory of Open Access Journals (Sweden)

    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.

  6. Transformation of the frequency-modulated continuous-wave field into a train of short pulses by resonant filters

    CERN Document Server

    Shakhmuratov, R N

    2016-01-01

    The resonant filtering method transforming frequency modulated radiation field into a train of short pulses is proposed to apply in optical domain. Effective frequency modulation can be achieved by electro-optic modulator or by resonant frequency modulation of the filter with a narrow absorption line. Due to frequency modulation narrow-spectrum CW radiation field is seen by the resonant filter as a comb of equidistant spectral components separated by the modulation frequency. Tuning narrow-bandwidth filter in resonance with $n$-th spectral component of the comb transforms the radiation field into bunches of pulses with $n$ pulses in each bunch. The transformation is explained by the interference of the coherently scattered resonant component of the field with the whole comb. Constructive interference results in formation of pulses, while destructive interference is seen as dark windows between pulses. It is found that the optimal thickness of the resonant filter is several orders of magnitude smaller than the...

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

    CERN Document Server

    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 ...

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

    Science.gov (United States)

    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. Field-Free Molecular Orientation Generated from Cyclic Rotational States by Using Two Trains of Half-Cycle Pulses

    Institute of Scientific and Technical Information of China (English)

    HUANG Yu-Xin; YANG Yu-Jun; ZHU Hong-Yu; WANG Li; WANG Hui; ZHU Qi-Ren

    2007-01-01

    We show that two trains of half-cycle pulses (HCPs) with different amplitudes irradiating alternately on polar molecules can achieve a remarkable enhancement of field-free orientation compared with the case of an equal amplitude HCPs train for the same pulse separation. This kind of orientation enhancements is mainly due to an optimal adjustment of the population distribution on every Geld-free angular momentum eigenstate, in which the populations on the undesired states of high angular momenta are effectively suppressed, and the populations on the desired states of low angular momenta are correspondingly promoted.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. High harmonic generation with fully tunable polarization by train of linearly polarized pulses

    Science.gov (United States)

    Neufeld, Ofer; Bordo, Eliyahu; Fleischer, Avner; Cohen, Oren

    2017-02-01

    We propose and demonstrate, analytically and numerically, a scheme for generation of high-order harmonics with fully tunable polarization, from circular through elliptic to linear, while barely changing the other properties of the high harmonic radiation and where the ellipticity values of all the harmonic orders essentially coincide. The high harmonics are driven by a train of quasi-monochromatic linearly polarized pulses that are identical except for their polarization angles, which is the tuning knob. This system gives rise to full control over the polarization of the harmonics while largely preserving the single-cycle, single-atom and macroscopic physics of ‘ordinary’ high harmonic generation, where both the driver and high harmonics are linearly polarized.

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

    Institute of Scientific and Technical Information of China (English)

    韩玉晶; 廖国前; 陈黎明; 李玉同; 王伟民; 张杰

    2015-01-01

    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.

  13. Characterization of the thermal refraction in ionic liquids induced by a train of femtosecond laser pulses

    Science.gov (United States)

    López Lago, E.; Nóvoa, J. A.; Nóvoa, D.; Michinel, H.; Cabeza, O.; Rodríguez, J. R.; Varela, L. M.

    2013-11-01

    We investigate the nonlinear refraction induced by a train of ultrashort laser pulses (repetition rate 80.75MHz) in a set of ionic liquids: [EMIM][BF4], [BMIM] [BF4], [HMIM] [BF4], [OMIM] [BF4] and [DMIM] [BF4]. Due to the high repetition rate, linear absorption processes are developed which cause a non local increase of temperature that generates an inhomogeneous and non local spatial variation of the refractive index. This effect is known as thermal refraction. The goal of this work is to characterize by z-scan the induced changes in the refractive index at λ=810nm and to determine the thermooptic coefficient of this liquids at this wavelength

  14. A novel NOLM structure with nonreciprocal phase shift bias for power fluctuation reduction of pulse trains

    Institute of Scientific and Technical Information of China (English)

    Liwei Guo; Xue Feng; Yue Liu; Xiaoming Liu

    2006-01-01

    @@ A novel nonlinear optical loop mirror (NOLM) with a nonreciprocal phase shift bias (NPSB), called power equalization NOLM (PE-NOLM), is proposed for reducing the power fluctuation of pulse trains. NPSB provides part of the nonreciprocal phase difference so that the required input power is reduced, and nonsymmetrical coupling ratio of coupler can adjust the transmission curve to improve the equalization range. It has been shown theoretically that compared with earlier PE-NOLM, about 1.6 dB of equalization power reduction and about 2.2 dB of equalization range enhancement could be achieved. Experiments have demonstrated that the output power fluctuation is reduced to less than 0.4 dB, while the required input peak power range is 4.5 dBm (15.6-20.1 dBm).

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

    CERN Document Server

    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...

  16. A novel scheme to generate 40-GHz CSRZ pulse trains using a 10-GHz dual-parallel Mach-Zehnder modulator

    Institute of Scientific and Technical Information of China (English)

    Yanfei Xing; Caiyun Lou

    2011-01-01

    A new technique to generate 40-GHz carrier-suppressed return-to-zero (CSRZ) optical pulse trains using only a 10-GHz dual-parallel Mach-Zehnder modulator (MZM) is presented and experimentally demonstrated. The spectrum of the generated CSRZ pulses is calculated by simulation and compared with conventional MZM-based RZ and CSRZ pulse trains. The experimental results demonstrate that CSRZ pulse trains are obtained, and that the carrier and the unwanted 20-GHz low-frequency component are suppressed by 25 dB. The technique can also be extended to 160-GHz CSRZ pulse generation when 40-GHz devices are employed.%@@ A new technique to generate 40-GHz carrier-suppressed return-to-zero (CSRZ) optical pulse trains using only a 10-GHz dual-parallel Mach-Zehnder modulator (MZM) is presented and experimentally demonstrated. The spectrum of the generated CSRZ pulses is calculated by simulation and compared with conventional MZM-based RZ and CSRZ pulse trains. The experimental results demonstrate that CSRZ pulse trains are obtained, and that the carrier and the unwanted 20-GHz low-frequency component are suppressed by 25 dB. The technique can also be extended to 160-GHz CSRZ pulse generation when 40-GHz devices are employed.

  17. Generation of bright attosecond x-ray pulse trains via Thomson scattering from laser-plasma accelerators.

    Science.gov (United States)

    Luo, W; Yu, T P; Chen, M; Song, Y M; Zhu, Z C; Ma, Y Y; Zhuo, H B

    2014-12-29

    Generation of attosecond x-ray pulse attracts more and more attention within the advanced light source user community due to its potentially wide applications. Here we propose an all-optical scheme to generate bright, attosecond hard x-ray pulse trains by Thomson backscattering of similarly structured electron beams produced in a vacuum channel by a tightly focused laser pulse. Design parameters for a proof-of-concept experiment are presented and demonstrated by using a particle-in-cell code and a four-dimensional laser-Compton scattering simulation code to model both the laser-based electron acceleration and Thomson scattering processes. Trains of 200 attosecond duration hard x-ray pulses holding stable longitudinal spacing with photon energies approaching 50 keV and maximum achievable peak brightness up to 1020 photons/s/mm2/mrad2/0.1%BW for each micro-bunch are observed. The suggested physical scheme for attosecond x-ray pulse trains generation may directly access the fastest time scales relevant to electron dynamics in atoms, molecules and materials.

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

    CERN Document Server

    Buica, Gabriela

    2014-01-01

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

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

    DEFF Research Database (Denmark)

    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...

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

    Directory of Open Access Journals (Sweden)

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

    CERN Document Server

    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 ...

  2. Axisymmetric pulse train solutions in narrow-gap spherical Couette flow

    CERN Document Server

    Child, Adam; Kersalé, Evy

    2016-01-01

    We numerically compute the flow induced in a spherical shell by fixing the outer sphere and rotating the inner one. The aspect ratio $\\epsilon=(r_o-r_i)/r_i$ is set at 0.04 and 0.02, and in each case the Reynolds number measuring the inner sphere's rotation rate is increased to $\\sim10\\%$ beyond the first bifurcation from the basic state flow. For $\\epsilon =0.04$ the initial bifurcations are the same as in previous numerical work at $\\epsilon=0.154$, and result in steady one- and two-vortex states. Further bifurcations yield travelling wave solutions similar to previous analytic results valid in the $\\epsilon\\to0$ limit. For $\\epsilon=0.02$ the steady one-vortex state no longer exists, and the first bifurcation is directly to these travelling wave solutions, consisting of pulse trains of Taylor vortices travelling toward the equator from both hemispheres, and annihilating there in distinct phase-slip events. We explore these time-dependent solutions in detail, and find that they can be both equatorially symm...

  3. Self-organization of waves and pulse trains by molecular motors in cellular protrusions.

    Science.gov (United States)

    Yochelis, A; Ebrahim, S; Millis, B; Cui, R; Kachar, B; Naoz, M; Gov, N S

    2015-09-03

    Actin-based cellular protrusions are an ubiquitous feature of cells, performing a variety of critical functions ranging from cell-cell communication to cell motility. The formation and maintenance of these protrusions relies on the transport of proteins via myosin motors, to the protrusion tip. While tip-directed motion leads to accumulation of motors (and their molecular cargo) at the protrusion tip, it is observed that motors also form rearward moving, periodic and isolated aggregates. The origins and mechanisms of these aggregates, and whether they are important for the recycling of motors, remain open puzzles. Motivated by novel myosin-XV experiments, a mass conserving reaction-diffusion-advection model is proposed. The model incorporates a non-linear cooperative interaction between motors, which converts them between an active and an inactive state. Specifically, the type of aggregate formed (traveling waves or pulse-trains) is linked to the kinetics of motors at the protrusion tip which is introduced by a boundary condition. These pattern selection mechanisms are found not only to qualitatively agree with empirical observations but open new vistas to the transport phenomena by molecular motors in general.

  4. The Study on the Variation of the Cavity Length's Influence on the Output Pulse Train of the Actively Mode-Locked Fiber Laser

    Institute of Scientific and Technical Information of China (English)

    LUO Hong-e; TIAN Xiao-jian; GAO Bo

    2005-01-01

    The influence of actively mode-locked Erbium-Doped Fiber Laser(EDFL) cavity length variation on the noises of an optical pulse train is investigated, in theory and in MATLAB simulation. Using a simple model, the noise characteristics of the output pulse train are studied. The results show that the noises of the output pulse train increase with the increasing of the variation of the cavity length. The theory analysis and the simulation results agree well. This result is very significant for us to improve the reliability and the stability of the actively mode-locked fiber laser.

  5. In Vitro Photothermal Destruction of Cancer Cells Using Gold Nanorods and Pulsed-Train Near-Infrared Laser

    Directory of Open Access Journals (Sweden)

    Jui-Teng Lin

    2012-01-01

    Full Text Available We present a novel pulsed-train near-IR diode laser system with real-time temperature monitoring of the laser-heated cancer cell mixed in gold nanorod solution. Near-IR diode laser at 808 nm matching the gold nanorod absorption peak (with an aspect ratio about 4.0 was used in this study. Both surface and volume temperatures were measured and kept above 43°C, the temperature for cancer cells destruction. The irradiation time needed in our pulsed-train system with higher laser fluence for killing the cancel cells is about 1–3 minutes, much shorter than conventional methods (5–10 minutes. Cell viabilities in gold nanorod mixed and controlled solutions are studied by green fluorescence.

  6. Noise tolerance in wavelength-selective switching of optical differential quadrature-phase-shift-keying pulse train by collinear acousto-optic devices.

    Science.gov (United States)

    Goto, Nobuo; Miyazaki, Yasumitsu

    2014-06-01

    Optical switching of high-bit-rate quadrature-phase-shift-keying (QPSK) pulse trains using collinear acousto-optic (AO) devices is theoretically discussed. Since the collinear AO devices have wavelength selectivity, the switched optical pulse trains suffer from distortion when the bandwidth of the pulse train is comparable to the pass bandwidth of the AO device. As the AO device, a sidelobe-suppressed device with a tapered surface-acoustic-wave (SAW) waveguide and a Butterworth-type filter device with a lossy SAW directional coupler are considered. Phase distortion of optical pulse trains at 40 to 100  Gsymbols/s in QPSK format is numerically analyzed. Bit-error-rate performance with additive Gaussian noise is also evaluated by the Monte Carlo method.

  7. Gigahertz repetition rate, sub-femtosecond timing jitter optical pulse train directly generated from a mode-locked Yb:KYW laser

    CERN Document Server

    Yang, Heewon; Shin, Junho; Kim, Chur; Choi, Sun Young; Kim, Guang-Hoon; Rotermund, Fabian; Kim, Jungwon

    2014-01-01

    We show that a 1.13-GHz repetition rate optical pulse train with 0.70 fs high-frequency timing jitter (integration bandwidth of 17.5 kHz - 10 MHz, where the measurement instrument-limited noise floor contributes 0.41 fs in 10 MHz bandwidth) can be directly generated from a free-running, single-mode diode-pumped Yb:KYW laser mode-locked by single-walled carbon nanotube (SWCNT)-coated mirrors. To our knowledge, this is the lowest timing jitter optical pulse train with the GHz repetition rate ever measured. If this pulse train is used for direct sampling of 565-MHz signals (Nyquist frequency of the pulse train), the demonstrated jitter level corresponds to the projected effective-number-of-bit (ENOB) of 17.8, which is much higher than the thermal noise limit of 50-ohm load resistance (~14 bits).

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

    DEFF Research Database (Denmark)

    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....

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

    Directory of Open Access Journals (Sweden)

    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.

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

    CERN Document Server

    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 %.

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

    DEFF Research Database (Denmark)

    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 th...

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

    DEFF Research Database (Denmark)

    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 clearly show the dependence of the maximum bit rate on material and device parameters. A comparative analysis of QD, quantum well (QW), and bulk SOAs shows that QD SOAs may have superior properties; calculations predict patterning-free amplification up to bit rates of 150–200 Gb/s with pulse output...

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

    Directory of Open Access Journals (Sweden)

    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.

  14. Investigating the intersystem crossing rate and triplet quantum yield of Protoporphyrin IX by means of pulse train fluorescence technique

    Science.gov (United States)

    Gotardo, Fernando; Cocca, Leandro H. Z.; Acunha, Thiago V.; Longoni, Ana; Toldo, Josene; Gonçalves, Paulo F. B.; Iglesias, Bernardo A.; De Boni, Leonardo

    2017-04-01

    Photophysical investigations of PPIX were described in order to determine the triplet conversion efficiency. Time resolved fluorescence and pulse train fluorescence were employed to characterize the main mechanism responsible for deactivation of the first singlet excited state (excited singlet and triplet states). Single pulse and Z-Scan analysis were employed to measure the singlet excited state absorption cross-sections. Theoretical calculations were performed in order to get some properties of PPIX in ground state, first singlet and triplet excited state. A TD-DFT result shows a great possibility of ISC associated to out-of-plane distortions in porphyrinic ring. Furthermore, the B and Q bands in the calculated spectrum are assigned to the four frontier molecular orbitals as proposed by Gouterman for free-based porphyrins.

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

    OpenAIRE

    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...

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  17. Observation of cold Rb{sub 2} molecules trapped in an optical dipole trap using a laser-pulse-train technique

    Energy Technology Data Exchange (ETDEWEB)

    Menegatti, Carlos R.; Marangoni, Bruno S.; Marcassa, Luis G. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Caixa Postal 369, 13560-970, Sao Carlos, SP (Brazil)

    2011-11-15

    In this work, we have developed and characterized a laser-pulse-train technique to observe cold Rb{sub 2} molecules trapped in an optical dipole trap. The molecules are produced in a magneto-optical trap, and then loaded into a crossed optical dipole trap. The time evolution of the molecular population is obtained by applying a laser pulse train, which photoionizes the ground-state molecules through intermediate molecular bands. Our results show that this technique allows us to obtain a faster data acquisition rate of the time evolution of the molecule population than other techniques.

  18. Taking the Pulse of Training Transfer: Instructor Quality and EMT Certification Examination Results

    Science.gov (United States)

    Russ-Eft, Darlene F.; Dickison, Phil; Levine, Roger

    2010-01-01

    The Longitudinal Emergency Medical Technician Attributes and Demographics Study (LEADS) provides a representative sampling of EMTs throughout the United States. The present study adds to the transfer of training literature by examining the relationship between instructor quality and National Registry of Emergency Medical Technicians certification…

  19. Taking the Pulse of Training Transfer: Instructor Quality and EMT Certification Examination Results

    Science.gov (United States)

    Russ-Eft, Darlene F.; Dickison, Phil; Levine, Roger

    2010-01-01

    The Longitudinal Emergency Medical Technician Attributes and Demographics Study (LEADS) provides a representative sampling of EMTs throughout the United States. The present study adds to the transfer of training literature by examining the relationship between instructor quality and National Registry of Emergency Medical Technicians certification…

  20. Dual-scale nanoripple/nanoparticle-covered microspikes on silicon by femtosecond double pulse train irradiation in water

    Science.gov (United States)

    Meng, Ge; Jiang, Lan; Li, Xin; Xu, Yongda; Shi, Xuesong; Yan, Ruyu; Lu, Yongfeng

    2017-07-01

    Novel dual-scale structures were obtained by femtosecond double pulse train (subpulse delay Δt > 0 ps) one-step irradiating silicon in water. The dual-scale structures consist of microspikes of ∼2 μm width and ∼0.5 μm height, and nanoripples with a mean period of 146 nm or nanoparticles with a mean diameter of 90 nm which entirely cover on the microspikes, for linearly polarized or circularly polarized femtosecond laser respectively. The formation of dual-scale structures involves the following processes: (1) Continuously laser energy deposited at femtosecond to picosecond timescales within silicon surfaces and central regions, will result in enhanced capillary waves and thinner melted silicon layers. Hence, the microspikes can be induced at laser fluences below ablation threshold; (2) Later (>500-800 pulses), a mass of debris and bubbles produced will lead to the remarkably and uniformly scattering or shielding of subsequent incident laser energy. Hence, the nanostructures can be induced. The novel structures exhibit high-sensitive surface enhanced Raman scattering with an enhancement factor of 108 for Rhodamine 6G detecting. Besides, the novel structures have application potentials in improving the silicon hydrophobicity, antireflection, etc.

  1. Aerobic or Resistance Training and Pulse Wave Velocity in Kidney Transplant Recipients: A 12-Week Pilot Randomized Controlled Trial (the Exercise in Renal Transplant [ExeRT] Trial).

    Science.gov (United States)

    Greenwood, Sharlene A; Koufaki, Pelagia; Mercer, Thomas H; Rush, Robert; O'Connor, Ellen; Tuffnell, Rachel; Lindup, Herolin; Haggis, Lynda; Dew, Tracy; Abdulnassir, Lyndsey; Nugent, Eilish; Goldsmith, David; Macdougall, Iain C

    2015-10-01

    Cardiovascular disease remains the leading cause of death in kidney transplant recipients. This pilot study examined the potential effect of aerobic training or resistance training on vascular health and indexes of cardiovascular risk in kidney transplant recipients. Single-blind, randomized, controlled, parallel trial. 60 participants (mean age, 54 years; 34 men) were randomly assigned to aerobic training (n=20), resistance training (n=20), or usual care (n=20). Participants were included if they had a kidney transplant within 12 months prior to baseline assessment. Patients were excluded if they had unstable medical conditions or had recently started regular exercise. Aerobic training and resistance training were delivered 3 days per week for a 12-week period. The usual-care group received standard care. Pulse wave velocity, peak oxygen uptake (Vo2peak), sit-to-stand 60, isometric quadriceps force, and inflammatory biomarkers were assessed at 0 and 12 weeks. The anticipated 60 participants were recruited within 12 months. 46 participants completed the study (aerobic training, n=13; resistance training, n=13; and usual care, n=20), resulting in a 23% attrition rate. Analyses of covariance, adjusted for baseline values, age, and dialysis vintage pretransplantation, revealed significant mean differences between aerobic training and usual care in pulse wave velocity of -2.2±0.4 (95% CI, -3.1 to -1.3) m/s (PPilot study, small sample size, no measure of endothelial function. Both aerobic training and resistance training interventions appear to be feasible and clinically beneficial in this patient population. Copyright © 2015 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

  2. Impact of a web based interactive simulation game (PULSE) on nursing students' experience and performance in life support training--a pilot study.

    Science.gov (United States)

    Cook, Neal F; McAloon, Toni; O'Neill, Philip; Beggs, Richard

    2012-08-01

    The delivery of effective life support measures is highly associated with the quality, design and implementation of the education that underpins it. Effectively responding to a critical event is a requirement for all nurses illustrating the need for effective educational approaches from pre-registration training through to enhancing and maintaining life support skills after qualification. This paper reports the findings of utilising a web-based multimedia simulation game PULSE (Platform for Undergraduate Life Support Education). The platform was developed to enhance the student experience of life support education, to motivate on-going learning and engagement and to improve psychomotor skills associated with the provision of Intermediate Life Support (ILS) training. Pre training participants played PULSE and during life support training data was collected from an intervention and a control group of final year undergraduate nursing students (N=34). Quantitative analysis of performance took place and qualitative data was generated from a questionnaire assessing the learning experience. A statistically significant difference was found between the competence the groups displayed in the three skills sets of checking equipment, airway assessment and the safe/effective use of defibrillator at ILS level, and PULSE was positively evaluated as an educational tool when used alongside traditional life support training.

  3. An in vivo investigation of inferior colliculus single neuron responses to cochlear nucleus pulse train stimulation.

    Science.gov (United States)

    Mauger, Stefan J; Shivdasani, Mohit N; Rathbone, Graeme D; Paolini, Antonio G

    2012-12-01

    The auditory brain stem implant (ABI) is being used clinically to restore hearing to patients unable to benefit from a cochlear implant (CI). Speech perception outcomes for ABI users are typically poor compared with most CI users. The ABI is implanted either on the surface of or penetrating through the cochlear nucleus in the auditory brain stem and uses stimulation strategies developed for auditory nerve stimulation with a CI. Although the stimulus rate may affect speech perception outcomes with current stimulation strategies, no studies have systematically investigated the effect of stimulus rate electrophysiologically or clinically. We therefore investigated rate response properties and temporal response properties of single inferior colliculus (IC) neurons from penetrating ABI stimulation using stimulus rates ranging from 100 to 1,600 pulses/s in the rat. We found that the stimulus rate affected the proportion of response types, thresholds, and dynamic ranges of IC activation. The stimulus rate was also found to affect the temporal properties of IC responses, with higher rates providing more temporally similar responses to acoustic stimulation. Suppression of neural firing and inhibition in IC neurons was also found, with response properties varying with the stimulus rate. This study demonstrated that changes in the ABI stimulus rate results in significant differences in IC neuron response properties. Due to electrophysiological differences, the stimulus rate may also change perceptual properties. We suggest that clinical evaluation of the ABI stimulus rate should be performed.

  4. Coherent manipulation of four-level double lambda-like atomic system by a train of ultra-short few-cycle-optical pulses

    CERN Document Server

    Kumar, Pawan

    2014-01-01

    We have demonstrated that near complete coherence can be achieved in a four level double lambda-like systems using a train of ultra-short optical pulses. The effect of the Doppler broadening has been analyzed and a scheme has been proposed for establishing high and uniform coherence across different velocity groups in the atomic ensemble. We have also presented a novel scheme of excitation using chirped pulses and shown that in addition to generating coherence in the system it is possible to alter the translational states of the atoms.

  5. Simultaneously Excitatory and Inhibitory Effects of Transcranial Alternating Current Stimulation Revealed Using Selective Pulse-Train Stimulation in the Rat Motor Cortex.

    Science.gov (United States)

    Khatoun, Ahmad; Asamoah, Boateng; Mc Laughlin, Myles

    2017-09-27

    Transcranial alternating current stimulation (tACS) uses sinusoidal, subthreshold, electric fields to modulate cortical processing. Cortical processing depends on a fine balance between excitation and inhibition and tACS acts on both excitatory and inhibitory cortical neurons. Given this, it is not clear whether tACS should increase or decrease cortical excitability. We investigated this using transcranial current stimulation of the rat (all males) motor cortex consisting of a continuous subthreshold sine wave with short bursts of suprathreshold pulse-trains inserted at different phases to probe cortical excitability. We found that when a low-rate, long-duration, suprathreshold pulse-train was used, subthreshold cathodal tACS decreased cortical excitability and anodal tACS increased excitability. However, when a high-rate, short-duration, suprathreshold pulse-train was used this pattern was inverted. An integrate-and-fire model incorporating biophysical differences between cortical excitatory and inhibitory neurons could predict the experimental data and helped interpret these results. The model indicated that low-rate suprathreshold pulse-trains preferentially stimulate excitatory cortical neurons, whereas high-rate suprathreshold pulse-trains stimulate both excitatory and inhibitory neurons. If correct, this indicates that suprathreshold pulse-train stimulation may be able to selectively control the excitation-inhibition balance within a cortical network. The excitation-inhibition balance then likely plays an important role in determining whether subthreshold tACS will increase or decrease cortical excitability.SIGNIFICANCE STATEMENT Transcranial alternating current stimulation (tACS) is a noninvasive neuromodulation method that uses weak sinusoidal electric fields to modulate cortical activity. In healthy volunteers tACS can modulate perception, cognition, and motor function but the underlying neural mechanism is poorly understood. In this study, using rat motor

  6. Evolutions of Continuous-Wave Perturbed by Pulse and Generation of Ultra-Short Pulse Trains%脉冲扰动下连续波的演化及超短脉冲串产生

    Institute of Scientific and Technical Information of China (English)

    钟先琼; 向安平; 程科; 蔡青

    2011-01-01

    Based on the nonlinear Schr(o)dinger equation and the stepped Fourier method, the shape and spectrum evolutions of continuous-wave perturbed by an optical pulse with Gaussian-typed continuum spectrum in an optical fiber are numerically simulated. The results show that, due to modulation instability in the anomalous dispersion region of the optical fiber, this pulse perturbed continuous-wave can also evolve into high-repetition-rate pulse trains, which is similar to the case of sine perturbed one. Being different from the latter case, however, the generated pulses are not equal to each other in terms of widths, intensities, and intervals. When soliton parameters are too small or the optical wave is in the normal dispersion region, only attenuation oscillation structures instead of pulse trains can be generated. And the characteristics of pulse trains or oscillation structures will vary with the soliton parameters. These evolution characteristics are obviously different from those of conventional sine perturbed continuous-waves and Gaussian optical pulses.%从光纤中非线性薛定谔方程出发,采用分步傅里叶算法数值模拟了具有高斯型连续谱的光脉冲扰动下连续波在光纤中的波形和频谱演化.结果表明,在光纤负色散区,由于调制不稳定性,该脉冲扰动下的连续波也可能像正弦波扰动下的那样演化成高重复率超短脉冲串,但构成脉冲串的各脉冲并不像正弦波扰动时那样等宽、等高、等间距.当孤子参数太小或在正色散区时,则不能形成脉冲串,只能形成衰减的振荡结构.随着孤子参数的不同,超短脉冲串及振荡结构的特点也会不同.这些演化规律与传统正弦光扰动连续波及高斯光脉冲的情形明显不同.

  7. High-precision Distribution of Highly-stable Optical Pulse Trains with Sub-10-fs Timing Jitter

    CERN Document Server

    Ning, B; Hou, D; Wu, J T; Li, Z B; Zhao, J Y

    2014-01-01

    High-precision optical pulse trains distribution via fibre links has made huge impacts in many fields. In most published works, the accuracies are still fundamentally limited by some unavoidable noises, such as thermal and shot noise from conventional photodiodes, thermal noise from mixers. Here, we demonstrate a new high-precision timing distribution system by using highly-precision phase detector to overcome the limitations. Instead of using photodiodes and microwave mixers, we use several fibre Sagnac-loop-based optical-microwave phase detectors to realize optical-electrical conversion and phase measurements, for suppressing the noises and achieving ultra-high accuracy. A 10-km fibre link distribution experiment shows our system provides a residual instability at the level of 4.6*10-15@1-s and 6.1*10-18@10000-s, with an integrated timing jitter as low as 3.8 fs in a bandwidth of 1 Hz to 100 KHz. This low instability and timing jitter makes it possible that our system can be used in the optical clock distri...

  8. Generation of trains of ultrashort microwave pulses by two coupled helical gyro-TWTs operating in regimes of amplification and nonlinear absorption

    Science.gov (United States)

    Ginzburg, N. S.; Denisov, G. G.; Vilkov, M. N.; Sergeev, A. S.; Zotova, I. V.; Samsonov, S. V.; Mishakin, S. V.

    2017-02-01

    Based on a time-domain model, we demonstrate that a periodic train of powerful ultrashort microwave pulses can be generated in an electron oscillator consisting of two coupled helically corrugated gyrotron travelling wave tubes (gyro-TWTs) operating in regimes of amplification and saturable absorption, respectively. The mechanism of pulse formation in such an oscillator is based on the effect of passive mode-locking widely used in laser physics. Saturable absorption can be implemented in a gyro-TWT in the Kompfner dip regime by a proper matching of the guiding magnetic field. According to simulations with the parameters of an experimentally realized Ka-band gyro-TWT, the peak power of generated pulses with a duration of 200 ps can achieve 400 kW.

  9. Cyclic State Orientation of Polar Molecules Produced by a Train of Half-Cycle Pulse Clusters of a Long Repetition Period

    Institute of Scientific and Technical Information of China (English)

    HUANG Yu-Xin; YANG Yu-Jun; WU Bin; GUO Fu-Ming; ZHU Qi-Ren

    2008-01-01

    @@ Using a variational method, we derive the optimal population distribution of angular momentum eigenstates for any given population range in a rotational wavepacket within the field-free cyclic state orientation framework.Correspondingly, we devise a train of half-cycle pulse clusters to purposively make the structure of the computed wavepacket approach the optimal population distribution, so that we can now utilize much more powerful means to realize an ideal orientation goal.

  10. Predicting dynamic range and intensity discrimination for electrical pulse-train stimuli using a stochastic auditory nerve model: the effects of stimulus noise.

    Science.gov (United States)

    Xu, Yifang; Collins, Leslie M

    2005-06-01

    This work investigates dynamic range and intensity discrimination for electrical pulse-train stimuli that are modulated by noise using a stochastic auditory nerve model. Based on a hypothesized monotonic relationship between loudness and the number of spikes elicited by a stimulus, theoretical prediction of the uncomfortable level has previously been determined by comparing spike counts to a fixed threshold, Nucl. However, no specific rule for determining Nucl has been suggested. Our work determines the uncomfortable level based on the excitation pattern of the neural response in a normal ear. The number of fibers corresponding to the portion of the basilar membrane driven by a stimulus at an uncomfortable level in a normal ear is related to Nucl at an uncomfortable level of the electrical stimulus. Intensity discrimination limens are predicted using signal detection theory via the probability mass function of the neural response and via experimental simulations. The results show that the uncomfortable level for pulse-train stimuli increases slightly as noise level increases. Combining this with our previous threshold predictions, we hypothesize that the dynamic range for noise-modulated pulse-train stimuli should increase with additive noise. However, since our predictions indicate that intensity discrimination under noise degrades, overall intensity coding performance may not improve significantly.

  11. Study on ablation of Ni film by ultrashort laser pulse-train%超短激光脉冲序列烧蚀镍薄膜的研究

    Institute of Scientific and Technical Information of China (English)

    韩飞; 闫寒; 周海波; 王琼娥

    2013-01-01

      超短(飞秒)激光脉冲序列技术能有效地提高激光加工金属的加工精度,它在微/纳制造中具有重要的理论意义和生产价值。为了研究脉冲间隔对激光烧蚀金属加工精度的影响,以过渡金属镍为研究对象,采用双温模型和分子动力学模拟相结合的方法,对飞秒激光脉冲序列(脉冲间隔不同)烧蚀金属镍的过程、现象进行了研究,取得了脉冲序列烧蚀镍薄膜的动态表层电子温度和晶格温度随时间演化的数据和烧蚀区域在不同时刻的快照。结果表明,一定范围内,随着脉冲间隔的增加,脉冲序列烧蚀镍薄膜所产生的纳米粒子更加均匀,烧蚀平面更加平整,初始熔化速度、烧蚀率呈降低趋势,有利于提高加工的精度。%Micromaching by ultrashort laser pulse-train can effectively improve femtosecond laser ablation of metal , which are important both theoretically and practically in micro /nano-laser fabrication applications.In order to study the effect of separation of pulse on the accuracy of laser ablation , the phenomena and process of laser ablation with different separation of pulse train were studied in detail by combining the molecular dynamic simulation and two -temperature model, the electron and lattice temperatures of the layers next to dynamic film surfaces and the snapshots of nickel thin films irradiated by the femtosecond laser pulse trains were obtained .The result is that ,within a certain range, as the increase of the separation of pulse, femtosecond pulse train laser ablation of Ni films can apparently cause more flat ablation plane , slower initial melting speed, smaller and more uniform nanoparticles , smaller ablation ratio,which can effectively improve femtosecond laser ablation of metal .

  12. Evolution of Hyperbolic-Secant Pulses Towards Cross-Phase Modulation Induced Optical Wave Breaking and Soliton or Soliton Trains Generation in Quintic Nonlinear Fibers

    Science.gov (United States)

    Zhong, Xian-Qiong; Zhang, Xiao-Xia; Du, Xian-Tong; Liu, Yong; Cheng, Ke

    2015-10-01

    The approximate analytical frequency chirps and the critical distances for cross-phase modulation induced optical wave breaking (OWB) of the initial hyperbolic-secant optical pulses propagating in optical fibers with quintic nonlinearity (QN) are presented. The pulse evolutions in terms of the frequency chirps, shapes and spectra are numerically calculated in the normal dispersion regime. The results reveal that, depending on different QN parameters, the traditional OWB or soliton or soliton pulse trains may occur. The approximate analytical critical distances are found to be in good agreement with the numerical ones only for the traditional OWB whereas the approximate analytical frequency chirps accords well with the numerical ones at the initial evolution stages of the pulses. Supported by the Postdoctoral Fund of China under Grant No. 2011M501402, the Key Project of Chinese Ministry of Education under Grant No. 210186, the Major Project of Natural Science Supported by the Educational Department of Sichuan Province under Grant No. 13ZA0081, the Key Project of National Natural Science Foundation of China under Grant No 61435010, and the National Natural Science Foundation of China under Grant No. 61275039

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

    Science.gov (United States)

    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.

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

    OpenAIRE

    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...

  15. Thermal and damage data from multiple microsecond pulse trains at 532nm in an in vitro retinal model

    Science.gov (United States)

    Denton, Michael L.; Tijerina, Amanda J.; Hoffman, Aaron; Clark, Clifton D.; Noojin, Gary D.; Rickman, John M.; Castellanos, Cherry C.; Shingledecker, Aurora D.; Boukhris, Sarah J.; Thomas, Robert J.; Rockwell, Benjamin A.

    2014-03-01

    An artificially pigmented retinal pigment epithelial (RPE) cell model was used to study the damage rates for exposure to 1, 10, 100, and 1,000 230-μs laser pulses at 532 nm, at two different concentrations of melanosome particles (MPs) per cell. Multiple pulses were delivered at pulse repetition rates of 50 and 99 pulses per second. Standard fluorescence viability indicator dyes and the method of microthermography were used to assess damage and thermal responses, respectively. Although frame rate during microthermography was more than five times slower than the duration of laser pulses, thermal information was useful in refining the BTEC computational model for simulating high-resolution thermal responses by the pigmented cells. When we temporally sampled the thermal model output at a rate similar to our microthermography, the resulting thermal profiles for multiple pulses resembled the thermal experimental profiles. Complementary to the thermal simulations, our computer-generated thresholds were in good agreement with the in vitro data. Findings are examined within the context of common exposure limit definitions in the national and international laser safety standards.

  16. Pulse plating

    CERN Document Server

    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...

  17. Bandwidth and repetition rate programmable Nyquist sinc-shaped pulse train source based on intensity modulators and four-wave mixing.

    Science.gov (United States)

    Cordette, S; Vedadi, A; Shoaie, M A; Brès, C-S

    2014-12-01

    We propose and experimentally demonstrate an all-optical Nyquist sinc-shaped pulse train source based on intensity modulation and four-wave mixing. The proposed scheme allows for the tunability of the bandwidth and the full flexibility of the repetition rate in the limit of the electronic bandwidth of the modulators used through the flexible synthesis of rectangular frequency combs. Bandwidth up to 360 GHz at 40 GHz rate and up to 45 frequency lines at 5 GHz rate are demonstrated with 40 GHz modulators.

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

    Science.gov (United States)

    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.

  19. Pulse on Pulse

    DEFF Research Database (Denmark)

    Schmidt, Ulrik; Carlson, Merete

    2012-01-01

    Pulse on Pulse” investigates the relation between signifying processes and non-signifying material dynamism in the installation Pulse Room (2006-) by Mexican Canadian artist Rafael Lozano-Hemmer. In Pulse Room the sense of pulse is ambiguous. Biorhythms are transmitted from the pulsing energy...... 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...... a multilayered sense of time and space that is central to the sensory experience of Pulse Room as a whole. Pulse Room is, at the very same time, an anthropomorfized archive of a past intimacy and an all-encompassing immersive environment modulating continuously in real space-time....

  20. Generation of spin waves by a train of fs-laser pulses: a novel approach for tuning magnon wavelength.

    Science.gov (United States)

    Savochkin, I V; Jäckl, M; Belotelov, V I; Akimov, I A; Kozhaev, M A; Sylgacheva, D A; Chernov, A I; Shaposhnikov, A N; Prokopov, A R; Berzhansky, V N; Yakovlev, D R; Zvezdin, A K; Bayer, M

    2017-07-18

    Currently spin waves are considered for computation and data processing as an alternative to charge currents. Generation of spin waves by ultrashort laser pulses provides several important advances with respect to conventional approaches using microwaves. In particular, focused laser spot works as a point source for spin waves and allows for directional control of spin waves and switching between their different types. For further progress in this direction it is important to manipulate with the spectrum of the optically generated spin waves. Here we tackle this problem by launching spin waves by a sequence of femtosecond laser pulses with pulse interval much shorter than the relaxation time of the magnetization oscillations. This leads to the cumulative phenomenon and allows us to generate magnons in a specific narrow range of wavenumbers. The wavelength of spin waves can be tuned from 15 μm to hundreds of microns by sweeping the external magnetic field by only 10 Oe or by slight variation of the pulse repetition rate. Our findings expand the capabilities of the optical spin pump-probe technique and provide a new method for the spin wave generation and control.

  1. Exact solution of the CPMG pulse sequence with phase variation down the echo train: application to R₂ measurements.

    Science.gov (United States)

    Bain, Alex D; Kumar Anand, Christopher; Nie, Zhenghua

    2011-04-01

    An implicit exact algebraic solution of CPMG experiments is presented and applied to fit experiments. Approximate solutions are also employed to explore oscillations and effective decay rates of CPMG experiments. The simplest algebraic approximate solution has illustrated that measured intensities will oscillate in the conventional CPMG experiments and that using even echoes can suppress errors of measurements of R₂ due to the imperfection of high-power pulses. To deal with low-power pulses with finite width, we adapt the effective field to calculate oscillations. An optimization model with the effective field approximation and dimensionless variables is proposed to quantify oscillations of measured intensities of CPMG experiments of different phases of the π pulses. We show, as was known using other methods, that repeating one group of four pulses with different phases in CPMG experiments, which we call phase variation, but others call phase alternation or phase cycling, can significantly smooth the dependence of measured intensities on frequency offset in the range of ±½γB₁. In this paper, a second-order expression with respect to the ratio of frequency offset to π-pulse amplitude is developed to describe the effective R₂ of CPMG experiments when using a group phase variation scheme. Experiments demonstrate that (1) the exact calculation of CPMG experiments can remarkably eliminate systematic errors in measured R₂s due to the effects of frequency offset, even in the absence of phase variation; (2) CPMG experiments with group phase variation can substantially remove oscillations and effects of the field inhomogeneity; (3) the second-order expression of the effective decay rate with phase variation is able to provide reliable estimates of R₂ when offsets are roughly within ±½γB₁; and, most significantly, (4) the more sophisticated optimization model using an exact solution of the discretized CPMG experiment extends, to ±γB₁, the range of

  2. Long-term pulse wave velocity outcomes with aerobic and resistance training in kidney transplant recipients - A pilot randomised controlled trial.

    Science.gov (United States)

    O'Connor, Ellen M; Koufaki, Pelagia; Mercer, Thomas H; Lindup, Herolin; Nugent, Eilish; Goldsmith, David; Macdougall, Iain C; Greenwood, Sharlene A

    2017-01-01

    This pilot study examined long-term pulse wave velocity (PWV) and peak oxygen uptake (VO2peak) outcomes following a 12-week moderate-intensity aerobic or resistance training programme in kidney transplant recipients. Single-blind, bi-centre randomised controlled parallel trial. 42 out of 60 participants completed a 9-month follow-up assessment (Aerobic training = 12, Resistance training = 10 and usual care = 20). Participants completed 12 weeks of twice-weekly supervised aerobic or resistance training. Following the 12-week exercise intervention, participants were transitioned to self-managed community exercise activity using motivational interviewing techniques. Usual care participants received usual encouragement for physical activity during routine clinical appointments in the transplant clinic. PWV, VO2peak, blood pressure and body weight were assessed at 12 weeks and 12 months, and compared to baseline. ANCOVA analysis, covarying for baseline values, age, and length of time on dialysis pre-transplantation, revealed a significant mean between-group difference in PWV of -1.30 m/sec (95%CI -2.44 to -0.17, p = 0.03) between resistance training and usual care groups. When comparing the aerobic training and usual care groups at 9-month follow-up, there was a mean difference of -1.05 m/sec (95%CI -2.11 to 0.017, p = 0.05). A significant mean between-group difference in relative VO2peak values of 2.2 ml/kg/min (95% CI 0.37 to 4.03, p = 0.02) when comparing aerobic training with usual care was revealed. There was no significant between group differences in body weight or blood pressure. There were no significant adverse effects associated with the interventions. Significant between-group differences in 9-month follow-up PWV existed when comparing resistance exercise intervention with usual care. A long-term between-group difference in VO2peak was only evident when comparing aerobic intervention with usual care. This pilot study, with a small sample size, did not aim to

  3. Pulse on Pulse

    DEFF Research Database (Denmark)

    Schmidt, Ulrik; Carlson, Merete

    2012-01-01

    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......“Pulse on Pulse” investigates the relation between signifying processes and non-signifying material dynamism in the installation Pulse Room (2006-) by Mexican Canadian artist Rafael Lozano-Hemmer. In Pulse Room the sense of pulse is ambiguous. Biorhythms are transmitted from the pulsing energy...... 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...

  4. Identification and annotation of multiple periodic pulse trains using dominant frequency and graph search: Applications in atrial fibrillation rotor detection.

    Science.gov (United States)

    Dalvi, Rupin; Suszko, Adrian; Chauhan, Vijay S

    2016-08-01

    Biological signals, such as intracardiac electrograms during atrial fibrillation (AF), can contain multiple periodic components or peaks. We propose a method for identifying individual periodic peak trains in signals containing multiple such periodic sequences. We use dominant frequency-based periodicity detection along with a graph search algorithm to identify the most dominant periodic activation set or peaks of interest. We then remove these peaks and iterate until all periodic sequences are identified. The proposed method is tested on simulated AF intra-cardiac electrograms with periodic activation trains of three distinct frequencies corrupted by noise and complex aperiodic signal features. The method is shown to have high accuracy (up to 100% sensitivity and 100% specificity) in detecting the three individual periodic peak trains. The method has application in biomedical signal analysis, such as detecting the periodic activations of a rotor, amidst other periodic activations during AF.

  5. Electroporation adopting trains of biphasic pulses enhances in vitro and in vivo the cytotoxic effect of doxorubicin on multidrug resistant colon adenocarcinoma cells (LoVo).

    Science.gov (United States)

    Meschini, Stefania; Condello, Maria; Lista, Pasquale; Vincenzi, Bruno; Baldi, Alfonso; Citro, Gennaro; Arancia, Giuseppe; Spugnini, Enrico P

    2012-09-01

    Few articles in the literature have focused on electroporation as a strategy to reverse multidrug resistance (MDR) of tumour cells and they are mostly limited to the improved efficacy of bleomycin. We tested the application of trains of biphasic pulses to cell suspensions and to murine xenografts as a strategy to increase the uptake of doxorubicin (DOX) and to enhance its cytotoxicity against chemoresistant cells. The human colon adenocarcinoma cell line LoVo DX, expressing MDR phenotype with high levels of P-glycoprotein (P-gp), has been used. The in vitro and in vivo studies gave the following results: (i) the application of the electric pulses to the cell suspension, immediately before DOX administration, induced a significant increase of drug retention; (ii) confocal microscopy observations showed a remarkable increase of intranuclear accumulation of DOX induced by electroporation; (iii) cell survival assay revealed a decrease of cell viability in the cultures treated with the combination of electroporation and doxorubicin; (iv) scanning electron microscopy observations revealed consistent morphological changes after the combined exposure to electroporation and doxorubicin; (v) in implanted mice the combined treatment induced an evident slowdown on the tumour growth when compared to treatment with DOX alone; (vi) histopathological analysis evidenced tumour destruction and its replacement by scar tissue in the tumours treated with the combination of doxorubicin and electroporation.

  6. Chaotic carrier pulse position modulation communication system and method

    Science.gov (United States)

    Abarbanel, Henry D. I.; Larson, Lawrence E.; Rulkov, Nikolai F.; Sushchik, Mikhail M.; Tsimring, Lev S.; Volkovskii, Alexander R.

    2001-01-01

    A chaotic carrier pulse position modulation communication system and method is disclosed. The system includes a transmitter and receiver having matched chaotic pulse regenerators. The chaotic pulse regenerator in the receiver produces a synchronized replica of a chaotic pulse train generated by the regenerator in the transmitter. The pulse train from the transmitter can therefore act as a carrier signal. Data is encoded by the transmitter through selectively altering the interpulse timing between pulses in the chaotic pulse train. The altered pulse train is transmitted as a pulse signal. The receiver can detect whether a particular interpulse interval in the pulse signal has been altered by reference to the synchronized replica it generates, and can therefore detect the data transmitted by the receiver. Preferably, the receiver predicts the earliest moment in time it can expect a next pulse after observation of at least two consecutive pulses. It then decodes the pulse signal beginning at a short time before expected arrival of a pulse.

  7. Pulse measurement apparatus and method

    Science.gov (United States)

    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.

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

    CERN Document Server

    Dikande, Alain M

    2010-01-01

    It has been established for some time that 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 on probe spectrum induced by the cross-phase-modulation effect for an harmonic probe trapped by a multiplex of temporal pulses, a linear equation (for the probe) and a nonlinear Schr\\"odinger 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 wavector develops into $\\vert n,l\\textgreater$ {\\it quantum states} involving $2n+1$ soliton-shaped eigenfunctions which spectral prop...

  9. The coherent artifact in modern pulse measurements

    CERN Document Server

    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.

  10. Digital Communication Using Chaotic Pulse Generators

    CERN Document Server

    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 ...

  11. Dynamic parabolic pulse generation using temporal shaping of wavelength to time mapped pulses.

    Science.gov (United States)

    Nguyen, Dat; Piracha, Mohammad Umar; Mandridis, Dimitrios; Delfyett, Peter J

    2011-06-20

    Self-phase modulation in fiber amplifiers can significantly degrade the quality of compressed pulses in chirped pulse amplification systems. Parabolic pulses with linear frequency chirp are suitable for suppressing nonlinearities, and to achieve high peak power pulses after compression. In this paper, we present an active time domain technique to generate parabolic pulses for chirped pulse amplification applications. Pulses from a mode-locked laser are temporally stretched and launched into an amplitude modulator, where the drive voltage is designed using the spectral shape of the input pulse and the transfer function of the modulator, resulting in the generation of parabolic pulses. Experimental results of pulse shaping with a pulse train from a mode-locked laser are presented, with a residual error of less than 5%. Moreover, an extinction ratio of 27 dB is achieved, which is ideal for chirped pulse amplification applications.

  12. Optimal pseudorandom pulse position modulation ladar waveforms.

    Science.gov (United States)

    Fluckiger, David U; Boland, Brian F; Marcus, Eran

    2015-03-20

    An algorithm for generating optimal pseudorandom pulse position modulation (PRPPM) waveforms for ladar ranging is presented. Bistatic ladar systems using Geiger-mode avalanche photodiodes require detection of several pulses in order to generate sufficient target statistics to satisfy some detection decision rule. For targets with large initial range uncertainty, it becomes convenient to transmit a pulse train with large ambiguity range. One solution is to employ a PRPPM waveform. An optimal PRPPM waveform will have minimal sidelobes: equivalent to 1 or 0 counts after the pulse correlation filter (compression). This can be accomplished by generating PRPPM pulse trains with optimal or minimal sidelobe autocorrelation.

  13. Laser-Plasma Instability Control Using TPulse fixed vs Imax fixed Spike Trains of Uneven Duration and Delay: The Path to Green ICF Using STUD Pulses

    Science.gov (United States)

    Afeyan, Bedros; Hüller, Stefan; Meezan, Nathan; Hammer, Jim; Heebner, John

    2016-10-01

    We have studied the behavior of laser-plasma instabilities (LPI) as a function of seed noise (varied over seven orders of magnitude) and Rosenbluth gain exponent at the average intensity (varied over a decade) for structured laser beams with and without STUD pulse mitigation. We will show that for each section of the NIF ICF pulse, there are preferred configurations of STUD pulses, whether they be fixed duration of fixed peak intensity, so that maximum use is made of STUD pulse flexibility for LPI control. The duty cycle, hot spot scrambling rate, and cutting a hot spot into pieces (by switching the lasers on and off on the ps time scale), are the three main tools. We explore a variety of phase transitions in reflectivity behavior and in the amplification profile of plasma perturbations. We compare cases where amplification bursts are reinforced coherently or are healed, lead to brush fires or are tamed. The STUD pulse program is best suited for Green light implementation since Green offers higher bandwidth, more energy, and higher damage thresholds. We plan to test these ideas on the Jupiter Laser Facility at LLNL at the pair of 200J lasers level next. Work supported by a Grant from the DOE NNSA-FES Joint Program on HEDP and by LLNL.

  14. Generation of 10 GHz transform-limited pulse train from dual-pump mode-locking erbium-doped fiber laser

    Science.gov (United States)

    He, Li; Yang, Bojun; Zhang, Xiaoguang; Yu, Li

    2006-09-01

    A dual-pump 10 GHz mode-locking erbium-doped fiber laser was demonstrated. With 10-GHz signal modulation of the modulator, less than 12 ps mode-locked pulse at 10 GHz repetition rate with 1.097 mW average output power was obtained. The corresponding spectrum width is 0.277 nm, which is centered at 1561 nm. The corresponding product of time and bandwidth is Δv*Δt which equals 0.433. Gaussian pulse shape is assumed, the output pulse is almost transform limited. Compared with single-pump fiber ring laser, the dual-pump fiber ring laser is helpful for suppression of supermode noise, which make this kind of fiber ring laser more stable.

  15. High-speed pulse-shape generator, pulse multiplexer

    Science.gov (United States)

    Burkhart, Scott C.

    2002-01-01

    The invention combines arbitrary amplitude high-speed pulses for precision pulse shaping for the National Ignition Facility (NIF). The circuitry combines arbitrary height pulses which are generated by replicating scaled versions of a trigger pulse and summing them delayed in time on a pulse line. The combined electrical pulses are connected to an electro-optic modulator which modulates a laser beam. The circuit can also be adapted to combine multiple channels of high speed data into a single train of electrical pulses which generates the optical pulses for very high speed optical communication. The invention has application in laser pulse shaping for inertial confinement fusion, in optical data links for computers, telecommunications, and in laser pulse shaping for atomic excitation studies. The invention can be used to effect at least a 10.times. increase in all fiber communication lines. It allows a greatly increased data transfer rate between high-performance computers. The invention is inexpensive enough to bring high-speed video and data services to homes through a super modem.

  16. Time shift of pulses due to dispersion slope and nonlinearity

    Energy Technology Data Exchange (ETDEWEB)

    Marcuse, D.; Menyuk, C.R.; Holzloehner, R.

    1999-12-01

    The authors show that the time delay of optical pulses traveling in long fibers is influenced by the dispersion slope and the fiber nonlinearity. Consequently, one or more new pulses that are inserted by add-drop operations into a pulse train that has already traveled a long distance may shift relative to the old pulses. This time shift delays the initial pulses more than the newly inserted ones, so that the newly inserted pulses can leave their time frames, leading to errors.

  17. Detection and visualization to Doppler sensitive sonar pulses

    NARCIS (Netherlands)

    Bertrand, D.B.; IJsselmuide, S.P. van; Beerens, S.P.

    2006-01-01

    In anti-submarine warfare, the use of Doppler sensitive sonar pulses is common practice. In particular, the wideband Doppler sensitive PTFM pulse (Pulse Train Frequency Modulation) is a powerful tool for detection in reverberation limited conditions. Nevertheless, this pulse is not operationally

  18. Upconversion chirped pulse amplification of ultrashort pulses using a multimode Tm:ZBLAN fiber

    Energy Technology Data Exchange (ETDEWEB)

    Yang, L.M.; Sosnowski, T.; Stock, M.L.; Norris, T.B.; Squier, J.; Mourou, G. [Univ. of Michigan, Ann Arbor, MI (United States). Center for Ultrafast Optical Science; Dennis, M.L.; Duling, I.N. III [Naval Research Lab., Washington, DC (United States)

    1995-11-01

    Microjoule pulse energies are achieved from a single stage upconversion fiber amplifier for the first time in this demonstration of chirped pulse amplification using a multimode TM:ZBLAN fiber. A Ti:sapphire laser system provides the seed pulse for the upconversion fiber amplifier which produces subpicosecond pulse trains with energies as great as 16 {micro}J at repetition rate of 4.4 kHz. The compressed, pulse peak power is more than 1 MW, and the pulse is characterized both temporally and spatially.

  19. Pulse Voltammetry.

    Science.gov (United States)

    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)

  20. Noisy homoclinic pulse dynamics

    Science.gov (United States)

    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.

  1. Computationally intelligent pulsed photoacoustics

    Science.gov (United States)

    Lukić, Mladena; Ćojbašić, Žarko; Rabasović, Mihailo D.; Markushev, Dragan D.

    2014-12-01

    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.

  2. Generating long sequences of high-intensity femtosecond pulses

    CERN Document Server

    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.

  3. 五阶非线性光纤中连续谱相位扰动下的光传输与脉冲串产生%Propagation of Optical Wave with Phase Perturbed by Continuous Spectrum and Generation of Pulse Trains in Optical Fibers with Quintic Nonlinearity

    Institute of Scientific and Technical Information of China (English)

    钟先琼; 向安平; 程科

    2011-01-01

    According to the extended nonlinear Schr(o)dinger equation including quintic nonlinearity in optical fibers,modulation instability (MI) based generation of high-repetition-rate optical pulse trains is numerically demonstrated by using the optical wave with its phase perturbed by Gaussian-typed continuous spectrum instead of conventional monochromatic one. The results show that,the pulse trains can also be generated due to MI effect like the conventional case.However,being different from the conventional case,the generated pulse trains here consist of limited number of pulses which are generally not equal in width,intensity,and interval.And the pulse number increases with the propagation distance.Moreover,when the other parameters are the same,the positive quintic nonlinearity can make the pulse width and interval shorten,which means that the positive quintic nonlinearity is beneficial to generate higher repetition rate pulse trains.While the negative one takes the opposite.The numerically calculated chirps developed during the generation process of pulse trains indicate that,both the chirps and their variations with the distance are highly nonmonotonic,and the quintic nonlinearity will change both the chirp range and the chirp amount.%根据包含五阶非线性的扩展非线性薛定谔方程,数值研究了高斯型连续谱相位扰动而不是传统单色扰动下基于调制不稳定性的高重复率脉冲串产生.结果表明:脉冲串也能像传统情形那样形成,但却呈现出不同的特性.如脉冲数目有限,且各脉冲的高度、强度及间距不等.脉冲数目随传输距离增加而增加.而五阶非线性能使脉冲宽度和间距变小因而有利于高重复率脉冲串产生,负五阶非线性则相反.对脉冲串形成过程中演变啁啾的数值计算表明,啁啾及其随距离的变化都是高度非单调的,五阶非线性将改变啁啾的范围和量值.

  4. PRI Detection of Segment Pulse Trains Based on Transform Spectrum Coherent Accumulation%基于变换谱相干积累的片段信号PRI检测

    Institute of Scientific and Technical Information of China (English)

    张什永; 胡泽宾; 王俊文

    2012-01-01

    Due to the effects of search modes and targets' beam scheduling, the reconnaissance systems can only intercept segment pulse trains from emitters, which is a big challenge for signal sorting. For this problem, a new method based on PRI transform spectrum coherent accumulation is proposed. PRI transform algorithm is introduced. The relationship between PRI spectrum peak value and pulse number included is given and its coherent accumulation feature is then revealed. Simulation results show that the new method can efficiently enhance PRI spectrum and is favourable to improve the detection propability.%受自身搜索方式和目标辐射源波束调度的影响,侦察系统往往只能截获辐射源的部分信号,这为后续分选处理带来了很大挑战.针对该问题,提出了通过时PRI变换谱进行相干积累以提高真实PRI检测概率的方法.首先介绍了PRI变换法,对算法原理进行了说明;接着从理论上推导了PRI变换谱峰值与脉冲个数的关系,指出了PRI变换谱的相干积累特性,并分析了其对虚假脉冲的适应能力;最后通过仿真试验对理论分析进行了验证.仿真结果表明,文中提出的方法能够有效提高片段信号的PRI 谱峰,从而有利于提高检测概率.

  5. Laser pulse shaping for high gradient accelerators

    Science.gov (United States)

    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.

  6. Laser pulse shaping for high gradient accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Villa, F., E-mail: fabio.villa@lnf.infn.it [INFN-Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati (Italy); Anania, M.P.; Bellaveglia, M. [INFN-Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati (Italy); Bisesto, F. [INFN-Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati (Italy); Università La Sapienza di Roma, Via A. Scarpa 14, Rome (Italy); Chiadroni, E. [INFN-Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati (Italy); Cianchi, A. [INFN-Roma Tor Vergata and Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome (Italy); Curcio, A.; Galletti, M.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Gatti, G. [INFN-Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati (Italy); Moreno, M.; Petrarca, M. [Università La Sapienza di Roma, Via A. Scarpa 14, Rome (Italy); Pompili, R.; Vaccarezza, C. [INFN-Laboratori Nazionali di Frascati, via E. Fermi 40, 00044 Frascati (Italy)

    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.

  7. Robot-assisted gait training improves brachial–ankle pulse wave velocity and peak aerobic capacity in subacute stroke patients with totally dependent ambulation

    Science.gov (United States)

    Han, Eun Young; Im, Sang Hee; Kim, Bo Ryun; Seo, Min Ji; Kim, Myeong Ok

    2016-01-01

    Abstract Objective: Brachial–ankle pulse wave velocity (baPWV) evaluates arterial stiffness and also predicts early outcome in stroke patients. The objectives of this study were to investigate arterial stiffness of subacute nonfunctional ambulatory stroke patients and to compare the effects of robot-assisted gait therapy (RAGT) combined with rehabilitation therapy (RT) on arterial stiffness and functional recovery with those of RT alone. Method: The RAGT group (N = 30) received 30 minutes of robot-assisted gait therapy and 30 minutes of conventional RT, and the control group (N = 26) received 60 minutes of RT, 5 times a week for 4 weeks. baPWV was measured and calculated using an automated device. The patients also performed a symptom-limited graded exercise stress test using a bicycle ergometer, and parameters of cardiopulmonary fitness were recorded. Clinical outcome measures were categorized into 4 categories: activities of daily living, balance, ambulatory function, and paretic leg motor function and were evaluated before and after the 4-week intervention. Results: Both groups exhibited significant functional recovery in all clinical outcome measures after the 4-week intervention. However, peak aerobic capacity, peak heart rate, exercise tolerance test duration, and baPWV improved only in the RAGT group, and the improvements in baPWV and peak aerobic capacity were more noticeable in the RAGT group than in the control group. Conclusion: Robot-assisted gait therapy combined with conventional rehabilitation therapy represents an effective method for reversing arterial stiffness and improving peak aerobic capacity in subacute stroke patients with totally dependent ambulation. However, further large-scale studies with longer term follow-up periods are warranted to measure the effects of RAGT on secondary prevention after stroke. PMID:27741123

  8. Robot-assisted gait training improves brachial-ankle pulse wave velocity and peak aerobic capacity in subacute stroke patients with totally dependent ambulation: Randomized controlled trial.

    Science.gov (United States)

    Han, Eun Young; Im, Sang Hee; Kim, Bo Ryun; Seo, Min Ji; Kim, Myeong Ok

    2016-10-01

    Brachial-ankle pulse wave velocity (baPWV) evaluates arterial stiffness and also predicts early outcome in stroke patients. The objectives of this study were to investigate arterial stiffness of subacute nonfunctional ambulatory stroke patients and to compare the effects of robot-assisted gait therapy (RAGT) combined with rehabilitation therapy (RT) on arterial stiffness and functional recovery with those of RT alone. The RAGT group (N = 30) received 30 minutes of robot-assisted gait therapy and 30 minutes of conventional RT, and the control group (N = 26) received 60 minutes of RT, 5 times a week for 4 weeks. baPWV was measured and calculated using an automated device. The patients also performed a symptom-limited graded exercise stress test using a bicycle ergometer, and parameters of cardiopulmonary fitness were recorded. Clinical outcome measures were categorized into 4 categories: activities of daily living, balance, ambulatory function, and paretic leg motor function and were evaluated before and after the 4-week intervention. Both groups exhibited significant functional recovery in all clinical outcome measures after the 4-week intervention. However, peak aerobic capacity, peak heart rate, exercise tolerance test duration, and baPWV improved only in the RAGT group, and the improvements in baPWV and peak aerobic capacity were more noticeable in the RAGT group than in the control group. Robot-assisted gait therapy combined with conventional rehabilitation therapy represents an effective method for reversing arterial stiffness and improving peak aerobic capacity in subacute stroke patients with totally dependent ambulation. However, further large-scale studies with longer term follow-up periods are warranted to measure the effects of RAGT on secondary prevention after stroke.

  9. Pulsed thermoelectricity

    Science.gov (United States)

    Apostol, M.; Nedelcu, M.

    2010-07-01

    A special mechanism of thermoelectric transport is described, consisting of pulses of charge carriers which "fly" periodically through the external circuit from the hot end of the sample to the cold end, with a determined duration of the "on" and "off" times of the electric contacts, while maintaining continuously the thermal contacts. It is shown that such a "resonant" ideal thermogenerator may work cyclically, with the same efficiency quotient as the ideal efficiency quotient of the thermoelectric devices operated in the usual stationary transport regime but the electric flow and power are increased, as a consequence of the concentration of the charge carriers on pulses of small spatial extent. The process is reversible, in the sense that it can be operated either as a thermoelectric generator or as an electrothermal cooler.

  10. PULSE COLUMN

    Science.gov (United States)

    Grimmett, E.S.

    1964-01-01

    This patent covers a continuous countercurrent liquidsolids contactor column having a number of contactor states each comprising a perforated plate, a layer of balls, and a downcomer tube; a liquid-pulsing piston; and a solids discharger formed of a conical section at the bottom of the column, and a tubular extension on the lowest downcomer terminating in the conical section. Between the conical section and the downcomer extension is formed a small annular opening, through which solids fall coming through the perforated plate of the lowest contactor stage. This annular opening is small enough that the pressure drop thereacross is greater than the pressure drop upward through the lowest contactor stage. (AEC)

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

    Science.gov (United States)

    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.

  12. Zeptosecond $\\gamma$-ray pulses

    CERN Document Server

    Klaiber, Michael; Keitel, Christoph H

    2007-01-01

    High-order harmonic generation (HHG) in the relativistic regime is employed to obtain zeptosecond pulses of $\\gamma$-rays. The harmonics are generated from atomic systems in counterpropagating strong attosecond laser pulse trains of linear polarization. In this setup recollisions of the ionized electrons can be achieved in the highly relativistic regime via a reversal of the commonly deteriorating drift and without instability of the electron dynamics such as in a standing laser wave. As a result, coherent attosecond $\\gamma$-rays in the 10 MeV energy range as well as coherent zeptosecond $\\gamma$-ray pulses of MeV photon energy for time-resolved nuclear spectroscopy become feasible.

  13. Laser-induced retinal damage threshold for repetitive-pulse exposure to 100-microsecs pulses

    Science.gov (United States)

    2014-10-07

    and is inde pendent of the pulse repetition frequency (PRF). When the injury mechanism is thermal denaturation, the pulses do interact , with the peak...energy incident on the cornea that passes through the pupil of the eye. TIE is expressed in this paper as the energy per pulse in the pulse train. 3...given in the guidelines as the corneal irradiance (J∕cm2), was multi plied by the area of a 7 mm pupil to give the allowable TIE. CP is a multiplicative

  14. Excimer Laser Pulse Compress With Pulse Feedback

    Institute of Scientific and Technical Information of China (English)

    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

  15. Pulsed Optics

    Science.gov (United States)

    Hirlimann, C.

    Optics is the field of physics which comprises knowledge on the interaction between light and matter. When the superposition principle can be applied to electromagnetic waves or when the properties of matter do not depend on the intensity of light, one speaks of linear optics. This situation occurs with regular light sources such as light bulbs, low-intensity light-emitting diodes and the sun. With such low-intensity sources the reaction of matter to light can be characterized by a set of parameters such as the index of refraction, the absorption and reflection coefficients and the orientation of the medium with respect to the polarization of the light. These parameters depend only on the nature of the medium. The situation changed dramatically after the development of lasers in the early sixties, which allowed the generation of light intensities larger than a kilowatt per square centimeter. Actual large-scale short-pulse lasers can generate peak powers in the petawatt regime. In that large-intensity regime the optical parameters of a material become functions of the intensity of the impinging light. In 1818 Fresnel wrote a letter to the French Academy of Sciences in which he noted that the proportionality between the vibration of the light and the subsequent vibration of matter was only true because no high intensities were available. The intensity dependence of the material response is what usually defines nonlinear optics.

  16. Optimal laser pulse energy partitioning for air ionization

    CERN Document Server

    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.

  17. Detailed characteristics of intermittent current pulses due to positive corona

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yang, E-mail: liuyangwuh520@sina.com; Cui, Xiang; Lu, Tiebing; Wang, Zhenguo; Li, Xuebao; Xiang, Yu; Wang, Xiaobo [State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206 (China)

    2014-08-15

    In order to get detailed characteristics of intermittent current pulses due to positive corona such as the repetition rate of burst-pulse trains, the peak value ratio of the primary pulse to the secondary pulse, the number of pulses per burst, and the interval of the secondary pulses, a systematic study was carried out in a coaxial conductor-cylinder electrode system with the conductor electrode being set with a discharge point. Empirical formulae for the number of pulses per burst and the interval of the secondary pulses are first presented. A theoretical model based on the motion of the space-charge clouds is proposed. Analysis with the model gives explanations to the experimental results and reveals some new insights into the physical mechanism of positive intermittent corona.

  18. Programmable pulse generator

    CERN Document Server

    Xue Zhi Hua; Duan Xiao Hui

    2002-01-01

    The author introduces the design of programmable pulse generator that is based on a micro-controller and controlled by RS232 interface of personal computer. The whole system has good stability. The pulse generator can produce TTL pulse and analog pulse. The pulse frequency can be selected by EPLD. The voltage amplitude and pulse width of analog pulse can be adjusted by analog switches and digitally-controlled potentiometers. The software development tools of computer is National Instruments LabView5.1. The front panel of this virtual instrumentation is intuitive and easy-to-use. Parameters can be selected and changed conveniently by knob and slide

  19. High-resolution microwave-photonic applications via precise synchronization between RF and mode-locked laser pulses (Conference Presentation)

    Science.gov (United States)

    Shi, Kebin; Lu, Xing; Lv, Zhiqiang

    2016-10-01

    Precise synchronization between radio frequency and mode-locked laser pulses provides a high resolution capability for detecting either time jitter in laser pulse train or phase noise in radio frequency. In this talk, we will present our recent progresses on radio frequency dissemination and fiber optical sensing based on sub-femtosecond level synchronization between radio frequency and mode-locked pulse train.

  20. Investigation of Fe:ZnSe laser in pulsed and repetitively pulsed regimes

    Energy Technology Data Exchange (ETDEWEB)

    Velikanov, S D; Zaretskiy, N A; Zotov, E A; Maneshkin, A A; Chuvatkin, R S; Yutkin, I M [Russian Federal Nuclear Center ' All-Russian Research Institute of Experimental Physics' , Sarov, Nizhnii Novgorod region (Russian Federation); Kozlovsky, V I; Korostelin, Yu V; Krokhin, O N; Podmar' kov, Yu P; Savinova, S A; Skasyrsky, Ya K; Frolov, M P [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2015-01-31

    The characteristics of a Fe:ZnSe laser pumped by a single-pulse free-running Er : YAG laser and a repetitively pulsed HF laser are presented. An output energy of 4.9 J is achieved in the case of liquid-nitrogen cooling of the Fe{sup 2+}:ZnSe active laser element longitudinally pumped by an Er:YAG laser with a pulse duration of 1 ms and an energy up to 15 J. The laser efficiency with respect to the absorbed energy is 47%. The output pulse energy at room temperature is 53 mJ. The decrease in the output energy is explained by a strong temperature dependence of the upper laser level lifetime and by pulsed heating of the active element. The temperature dependence of the upper laser level lifetime is used to determine the pump parameters needed to achieve high pulse energies at room temperature. Stable repetitively-pulsed operation of the Fe{sup 2+}:ZnSe laser at room temperature with an average power of 2.4 W and a maximum pulse energy of 14 mJ is achieved upon pumping by a 1-s train of 100-ns HF laser pulses with a repetition rate of 200 Hz. (lasers)

  1. Investigation of Fe:ZnSe laser in pulsed and repetitively pulsed regimes

    Science.gov (United States)

    Velikanov, S. D.; Zaretskiy, N. A.; Zotov, E. A.; Kozlovsky, V. I.; Korostelin, Yu V.; Krokhin, O. N.; Maneshkin, A. A.; Podmar'kov, Yu P.; Savinova, S. A.; Skasyrsky, Ya K.; Frolov, M. P.; Chuvatkin, R. S.; Yutkin, I. M.

    2015-01-01

    The characteristics of a Fe:ZnSe laser pumped by a single-pulse free-running Er : YAG laser and a repetitively pulsed HF laser are presented. An output energy of 4.9 J is achieved in the case of liquid-nitrogen cooling of the Fe2+:ZnSe active laser element longitudinally pumped by an Er:YAG laser with a pulse duration of 1 ms and an energy up to 15 J. The laser efficiency with respect to the absorbed energy is 47%. The output pulse energy at room temperature is 53 mJ. The decrease in the output energy is explained by a strong temperature dependence of the upper laser level lifetime and by pulsed heating of the active element. The temperature dependence of the upper laser level lifetime is used to determine the pump parameters needed to achieve high pulse energies at room temperature. Stable repetitively-pulsed operation of the Fe2+:ZnSe laser at room temperature with an average power of 2.4 W and a maximum pulse energy of 14 mJ is achieved upon pumping by a 1-s train of 100-ns HF laser pulses with a repetition rate of 200 Hz.

  2. Radial pulse (image)

    Science.gov (United States)

    ... 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 ...

  3. Wrist pulse (image)

    Science.gov (United States)

    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.

  4. Pulse-Width Jitter Measurement for Laser Diode Pulses

    Institute of Scientific and Technical Information of China (English)

    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.

  5. Language Training: English Training

    CERN Multimedia

    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.

  6. Language Training: English Training

    CERN Multimedia

    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.

  7. Ablation of steel using picosecond laser pulses in burst mode

    Science.gov (United States)

    Lickschat, Peter; Demba, Alexander; Weissmantel, Steffen

    2017-02-01

    Results obtained in picosecond laser processing of steel applying the burst mode are presented. Using the burst mode, pulse trains, i.e., bursts, consisting of a number of picosecond pulses with an inter-pulse delay of 12.5 ns and 10 ps pulse duration are applied for material processing. Small cavities with sizes in the range of the laser beam diameter made by single-burst ablation are compared to quadratic cavities of 0.5 × 0.5 mm² produced by multiburst ablation and simultaneous scanning of the laser beam across the steel sample surface. The ablated volume per pulse within the burst was calculated either from the ablated volume per burst or from the ablation depth of the quadratic cavities. With the second to fourth pulses in the bursts, a reduction of the ablated volume per pulse in comparison with the first pulse in the bursts (i.e., to the use of single pulses) was found for both single- and multiburst ablation, which is assumed to be due to plasma shielding. By contrast, the ablated volume per pulse within the bursts increases for the fifth to eighth pulses. Heat accumulation effect and the influence of the heated plasma can be assumed to be the reason for these higher ablation rates. SEM micrographs also show that there is a higher melt ejection out of the laser processed area. This is indicated by the formation of bulges about the ablated area.

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

    Science.gov (United States)

    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.

  9. Method of estimating pulse response using an impedance spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, John L; Morrison, William H; Christophersen, Jon P; Motloch, Chester G

    2014-10-21

    Electrochemical Impedance Spectrum data are used to predict pulse performance of an energy storage device. The impedance spectrum may be obtained in-situ. A simulation waveform includes a pulse wave with a period greater than or equal to the lowest frequency used in the impedance measurement. Fourier series coefficients of the pulse train can be obtained. The number of harmonic constituents in the Fourier series are selected so as to appropriately resolve the response, but the maximum frequency should be less than or equal to the highest frequency used in the impedance measurement. Using a current pulse as an example, the Fourier coefficients of the pulse are multiplied by the impedance spectrum at corresponding frequencies to obtain Fourier coefficients of the voltage response to the desired pulse. The Fourier coefficients of the response are then summed and reassembled to obtain the overall time domain estimate of the voltage using the Fourier series analysis.

  10. Studies of solid propellant combustion with pulsed radiography

    Science.gov (United States)

    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.

  11. PulseSoar

    Energy Technology Data Exchange (ETDEWEB)

    Carter, P.; Peglow, S.

    1992-07-21

    This paper is an introduction to the PulseSoar concept. PulseSoar is a hypervelocity airplane that uses existing airport facilities and current technologies to fly at the very edge of space. It will be shown that PulseSoar can fly between any two points on the globe in less than two hours with fuel efficiency exceeding current state of the art commercial airliners. In addition, it will be shown that PulseSoar avoids environmental issues concerning the ozone layer and sonic booms because of its unique flight profile. All of this can be achieved with current technology. PulseSoar does not require the development of enabling technology. It is a concept which can be demonstrated today. The importance of this idea goes beyond the technical significance`s of PulseSoar in terms of feasibility and performance. PulseSoar could provide a crucial economic advantage to America`s largest export market: commercial aircraft. PulseSoar is a breakthrough concept for addressing the emerging markets of long range and high speed aircraft. Application of PulseSoar to commercial transport could provide the US Aerospace industry a substantial lead in offering high speed/long range aircraft to the world`s airlines. The rapid emergence of a US developed high speed aircraft could also be important to our competitiveness in the Pacific Rim and South American economies. A quick and inexpensive demonstration vehicle is proposed to bang the concept to reality within two years. This discussion will address all the major technical subjects encompassed by PulseSoar and identifies several near-term, and low risk, applications which may be further explored with the initial demonstration vehicle. What is PulseSoar? PulseSoar could enable high speed, high altitude and long range flight without many of the difficulties encountered by traditional hypersonic vehicles.

  12. Pulse Tube Refrigerator

    Science.gov (United States)

    Matsubara, Yoichi

    The pulse tube refrigerator is one of the regenerative cycle refrigerators such as Stirling cycle or Gifford-McMahon cycle which gives the cooling temperature below 150 K down to liquid helium temperature. In 1963, W. E. Gifford invented a simple refrigeration cycle which is composed of compressor, regenerator and simple tube named as pulse tube which gives a similar function of the expander in Stirling or Gifford-McMahon cycle. The thermodynamically performance of this pulse tube refrigerator is inferior to that of other regenerative cycles. In 1984, however, Mikulin and coworkers made a significant advance in pulse tube configuration called as orifice pulse tube. After this, several modifications of the pulse tube hot end configuration have been developed. With those modifications, the thermodynamic performance of the pulse tube refrigerator became the same order to that of Stirling and Gifford-McMahon refrigerator. This article reviews the brief history of the pulse tube refrigerator development in the view point of its thermodynamically efficiency. Simplified theories of the energy flow in the pulse tube have also been described.

  13. Ultrashort Laser Pulse Phenomena

    CERN Document Server

    Diels, Jean-Claude

    2006-01-01

    Ultrashort Laser Pulse Phenomena, 2e serves as an introduction to the phenomena of ultra short laser pulses and describes how this technology can be used to examine problems in areas such as electromagnetism, optics, and quantum mechanics. Ultrashort Laser Pulse Phenomena combines theoretical backgrounds and experimental techniques and will serve as a manual on designing and constructing femtosecond (""faster than electronics"") systems or experiments from scratch. Beyond the simple optical system, the various sources of ultrashort pulses are presented, again with emphasis on the basic

  14. The Effect of Intrapulse RF Variation on Bunch Train Energy Spread (LCC-0030)

    Energy Technology Data Exchange (ETDEWEB)

    Nantista, C.

    2004-03-23

    In this note, we present a brief analysis of the effect of small variations in amplitude and phase in the accelerating rf pulse in addition to the deliberate pulse shaping on the energy deviation along a bunch train and the effects of pulse-to-pulse fluctuations.

  15. Language Training: French Training

    CERN Multimedia

    Françoise Benz

    2004-01-01

    General and Professional French Courses The next session will take place from 11 October to 17 December 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. Fontbonne: Tel. 72844. Writing Professional Documents in French 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. Fontbonne: tel. 72844. FORMATION EN LANGUES LANGUAGE TRAINING Françoise Benz 73127 language.training@cern.ch

  16. Language Training: French Training

    CERN Document Server

    Françoise Benz

    2005-01-01

    General and Professional French Courses The next session will take place from 18 April to 30 June 2005. 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 18 April to 30 June 2005. 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

  17. Language Training: French Training

    CERN Multimedia

    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...

  18. Language Training: French Training

    CERN Document Server

    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...

  19. Damage threshold and focusability of mid-infrared free-electron laser pulses gated by a plasma mirror with nanosecond switching pulses

    CERN Document Server

    Wang, Xiaolong; Zen, Heishun; Kii, Toshiteru; Ohgaki, Hideaki

    2013-01-01

    The presence of a pulse train structure of an oscillator-type free-electron laser (FEL) results in the immediate damage of a solid target upon focusing. We demonstrate that the laser-induced damage threshold can be significantly improved by gating the mid-infrared (MIR) FEL pulses with a plasma mirror. Although the switching pulses we employ have a nanosecond duration which does not guarantee the clean wavefront of the gated FEL pulses, the high focusablity is experimentally confirmed through the observation of spectral broadening by a factor of 2.1 when we tightly focus the gated FEL pulses onto the Ge plate.

  20. Pulsed Plasma Electron Sources

    Science.gov (United States)

    Krasik, Yakov

    2008-11-01

    Pulsed (˜10-7 s) electron beams with high current density (>10^2 A/cm^2) are generated in diodes with electric field of E > 10^6 V/cm. The source of electrons in these diodes is explosive emission plasma, which limits pulse duration; in the case E Hadas and Ya. E. Krasik, Europhysics Lett. 82, 55001 (2008).

  1. PULSE AMPLITUDE DISTRIBUTION RECORDER

    Science.gov (United States)

    Cowper, G.

    1958-08-12

    A device is described for automatica1ly recording pulse annplitude distribution received from a counter. The novelty of the device consists of the over-all arrangement of conventional circuit elements to provide an easy to read permanent record of the pulse amplitude distribution during a certain time period. In the device a pulse analyzer separates the pulses according to annplitude into several channels. A scaler in each channel counts the pulses and operates a pen marker positioned over a drivable recorder sheet. Since the scalers in each channel have the sanne capacity, the control circuitry permits counting of the incoming pulses until one scaler reaches capacity, whereupon the input is removed and an internal oscillator supplies the necessary pulses to fill up the other scalers. Movement of the chart sheet is initiated wben the first scaler reaches capacity to thereby give a series of marks at spacings proportional to the time required to fill the remaining scalers, and accessory equipment marks calibration points on the recorder sheet to facilitate direct reading of the number of external pulses supplied to each scaler.

  2. Estimate of pulse-sequence data acquisition system for multi-dimensional measurement

    Energy Technology Data Exchange (ETDEWEB)

    Kitamura, Yasunori; Sakae, Takeji; Nohtomi, Akihiro; Matoba, Masaru [Kyushu Univ., Fukuoka (Japan). Faculty of Engineering; Matsumoto, Yuzuru

    1996-07-01

    A pulse-sequence data acquisition system has been newly designed and estimated for the measurement of one- or multi-dimensional pulse train coming from radiation detectors. In this system, in order to realize the pulse-sequence data acquisition, the arrival time of each pulse is recorded to a memory of a personal computer (PC). For the multi-dimensional data acquisition with several input channels, each arrival-time data is tagged with a `flag` which indicates the input channel of arriving pulse. Counting losses due to the existence of processing time of the PC are expected to be reduced by using a First-In-First-Out (FIFO) memory unit. In order to verify this system, a computer simulation was performed, Various sets of random pulse trains with different mean pulse rate (1-600 kcps) were generated by using Monte Carlo simulation technique. Those pulse trains were dealt with another code which simulates the newly-designed data acquisition system including a FIFO memory unit; the memory size was assumed to be 0-100 words. And the recorded pulse trains on the PC with the various FIFO memory sizes have been observed. From the result of the simulation, it appears that the system with 3 words FIFO memory unit works successfully up to the pulse rate of 10 kcps without any severe counting losses. (author)

  3. Pulsed electron beam precharger

    Energy Technology Data Exchange (ETDEWEB)

    Finney, W.C. (ed.); Shelton, W.N.

    1990-01-01

    Florida State University is investigating the concept of pulsed electron beams for fly ash precipitation. This report describes the results and data on three of the subtasks of this project and preliminary work only on the remaining five subtasks. Described are the modification of precharger for pulsed and DC energization of anode; installation of the Q/A measurement system; and modification and installation of pulsed power supply to provide both pulsed and DC energization of the anode. The other tasks include: measurement of the removal efficiency for monodisperse simulated fly ash particles; measurement of particle charge; optimization of pulse energization schedule for maximum removal efficiency; practical assessment of results; and measurement of the removal efficiency for polydisperse test particles. 15 figs., 1 tab. (CK)

  4. Pulse Distortion in Saturated Fiber Optical Parametric Chirped Pulse Amplification

    DEFF Research Database (Denmark)

    Lali-Dastjerdi, Zohreh; Da Ros, Francesco; Rottwitt, Karsten

    2012-01-01

    Fiber optical parametric chirped pulse amplification is experimentally compared for different chirped pulses in the picosecond regime. The amplified chirped pulses show distortion appearing as pedestals after recompression when the amplifier is operated in saturation.......Fiber optical parametric chirped pulse amplification is experimentally compared for different chirped pulses in the picosecond regime. The amplified chirped pulses show distortion appearing as pedestals after recompression when the amplifier is operated in saturation....

  5. Acousto-optic pulse picking scheme with carrier-frequency-to-pulse-repetition-rate synchronization.

    Science.gov (United States)

    de Vries, Oliver; Saule, Tobias; Plötner, Marco; Lücking, Fabian; Eidam, Tino; Hoffmann, Armin; Klenke, Arno; Hädrich, Steffen; Limpert, Jens; Holzberger, Simon; Schreiber, Thomas; Eberhardt, Ramona; Pupeza, Ioachim; Tünnermann, Andreas

    2015-07-27

    We introduce and experimentally validate a pulse picking technique based on a travelling-wave-type acousto-optic modulator (AOM) having the AOM carrier frequency synchronized to the repetition rate of the original pulse train. As a consequence, the phase noise characteristic of the original pulse train is largely preserved, rendering this technique suitable for applications requiring carrier-envelope phase stabilization. In a proof-of-principle experiment, the 1030-nm spectral part of an 74-MHz, carrier-envelope phase stable Ti:sapphire oscillator is amplified and reduced in pulse repetition frequency by a factor of two, maintaining an unprecedentedly low carrier-envelope phase noise spectral density of below 68 mrad. Furthermore, a comparative analysis reveals that the pulse-picking-induced additional amplitude noise is minimized, when the AOM is operated under synchronicity. The proposed scheme is particularly suitable when the down-picked repetition rate is still in the multi-MHz-range, where Pockels cells cannot be applied due to piezoelectric ringing.

  6. Training safely, Training safety

    Directory of Open Access Journals (Sweden)

    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.

  7. Nonlinear and Dispersive Optical Pulse Propagation

    Science.gov (United States)

    Dijaili, Sol Peter

    In this dissertation, there are basically four novel contributions to the field of picosecond pulse propagation and measurement. The first contribution is the temporal ABCD matrix which is an analog of the traditional ABCD ray matrices used in Gaussian beam propagation. The temporal ABCD matrix allows for the easy calculation of the effects of linear chirp or group velocity dispersion in the time domain. As with Gaussian beams in space, there also exists a complete Hermite-Gaussian basis in time whose propagation can be tracked with the temporal ABCD matrices. The second contribution is the timing synchronization between a colliding pulse mode-locked dye laser and a gain-switched Fabry-Perot type AlGaAs laser diode that has achieved less than 40 femtoseconds of relative timing jitter by using a pulsed optical phase lock loop (POPLL). The relative timing jitter was measured using the error voltage of the feedback loop. This method of measurement is accurate since the frequencies of all the timing fluctuations fall within the loop bandwidth. The novel element is a broad band optical cross-correlator that can resolve femtosecond time delay errors between two pulse trains. The third contribution is a novel dispersive technique of determining the nonlinear frequency sweep of a picosecond pulse with relatively good accuracy. All the measurements are made in the time domain and hence there is no time-bandwidth limitation to the accuracy. The fourth contribution is the first demonstration of cross -phase modulation in a semiconductor laser amplifier where a variable chirp was observed. A simple expression for the chirp imparted on a weak signal pulse by the action of a strong pump pulse is derived. A maximum frequency excursion of 16 GHz due to the cross-phase modulation was measured. A value of 5 was found for alpha _{xpm} which is a factor for characterizing the cross-phase modulation in a similar manner to the conventional linewidth enhancement factor, alpha.

  8. Thermal Processes Using Attosecond Laser Pulses When Time Matters

    CERN Document Server

    Kozłowski, Mirosław

    2006-01-01

    This book contains a study of the thermal processes initiated by attosecond laser pulses. Considering the existence of the experimental evidence for the trains of the attosecond laser pulses, we developed the theoretical framework for attophysics, i.e. physics of phenomena with time duration in the attosecond domain. This time domain is concerned with phenomena whose duration is much shorter than the relaxation time for atomic, molecular and nanoparticles scales.

  9. Line Width Narrowing with 14N Nuclear Quadrupole Resonance Lines at 296 K and 77 K Using a High Powered Pulsed Spectrometer

    Science.gov (United States)

    Trepanier, R. J.; Whitehead, M. A.

    1986-02-01

    The dependence of the NQR line width on the RF pulse intensity and period using a continuous steady state pulse train for polycrystalline 14N compounds shows a dependence on the asymmetry parameter η, the temperature, and the crystal structure.

  10. Control of the polarization of attosecond pulses using a two-color field

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz, Camilo; Hoffmann, David J; Torres, Ricardo; Chipperfield, Luke E; Marangos, Jonathan P [Blackett Laboratory, Imperial College London, London SW7 2BW (United Kingdom)], E-mail: camilo@usal.es

    2009-11-15

    Control over the polarization of an attosecond pulse train (APT) is demonstrated theoretically using orthogonally polarized two-color fields. The carrier envelope phase of the two pulses is used as a control parameter to generate both an APT with linear polarization in two nearly perpendicular planes or a train of elliptically polarized pulses of alternating helicity. By using few-cycle driving laser fields an isolated attosecond pulse with elliptical polarization is shown to be generated after selecting the cut-off region of the harmonic spectrum. The control mechanism is explained in terms of classical trajectories.

  11. Optimal Design and Experimental characterisation of short optical pulse compression using CDPF

    DEFF Research Database (Denmark)

    Yujun, Qian; Quist, S.

    1999-01-01

    We present optimal design and experimental characterisation ofoptical pulse compression using a comblike dispersion-profiled fibre(CDPF). A pulse train at 10GHz with puslewidth of 1ps and side-lobesuppression of 30dB can be obtained.......We present optimal design and experimental characterisation ofoptical pulse compression using a comblike dispersion-profiled fibre(CDPF). A pulse train at 10GHz with puslewidth of 1ps and side-lobesuppression of 30dB can be obtained....

  12. Evaluating Training

    Institute of Scientific and Technical Information of China (English)

    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.

  13. RF Pulsed Heating

    Energy Technology Data Exchange (ETDEWEB)

    Pritzkau, David P.

    2002-01-03

    RF pulsed heating is a process by which a metal is heated from magnetic fields on its surface due to high-power pulsed RF. When the thermal stresses induced are larger than the elastic limit, microcracks and surface roughening will occur due to cyclic fatigue. Pulsed heating limits the maximum magnetic field on the surface and through it the maximum achievable accelerating gradient in a normal conducting accelerator structure. An experiment using circularly cylindrical cavities operating in the TE{sub 011} mode at a resonant frequency of 11.424 GHz is designed to study pulsed heating on OFE copper, a material commonly used in normal conducting accelerator structures. The high-power pulsed RF is supplied by an X-band klystron capable of outputting 50 MW, 1.5 {micro}s pulses. The test pieces of the cavity are designed to be removable to allow testing of different materials with different surface preparations. A diagnostic tool is developed to measure the temperature rise in the cavity utilizing the dynamic Q change of the resonant mode due to heating. The diagnostic consists of simultaneously exciting a TE{sub 012} mode to steady-state in the cavity at 18 GHz and measuring the change in reflected power as the cavity is heated from high-power pulsed RF. Two experimental runs were completed. One run was executed at a calculated temperature rise of 120 K for 56 x 10{sup 6} pulses. The second run was executed at a calculated temperature rise of 82 K for 86 x 10{sup 6} pulses. Scanning electron microscope pictures show extensive damage occurring in the region of maximum temperature rise on the surface of the test pieces.

  14. Parabolic similariton Yb-fiber laser with triangular pulse evolution

    Science.gov (United States)

    Wang, Sijia; Wang, Lei

    2016-04-01

    We propose a novel mode-locked fiber laser design which features a passive nonlinear triangular pulse formation and self-similar parabolic pulse amplification intra cavity. Attribute to the nonlinear reshaping progress in the passive fiber, a triangular-profiled pulse with negative-chirp is generated and paved the way for rapid and efficient self-similar parabolic evolution in a following short-length high-gain fiber. In the meanwhile, the accompanied significantly compressed narrow spectrum from this passive nonlinear reshaping also gives the promise of pulse stabilization and gain-shaping robustness without strong filtering. The resulting short average intra-cavity pulse duration, low amplified spontaneous emission (ASE) and low intra-cavity power loss are essential for the low-noise operation. Simulations predict this modelocked fiber laser allows for high-energy ultra-short transform-limited pulse generation exceeding the gain bandwidth. The output pulse has a de-chirped duration (full-width at half maximum, FWHM) of 27 fs. In addition to the ultrafast laser applications, the proposed fiber laser scheme can support low-noise parabolic and triangular pulse trains at the same time, which are also attractive in optical pulse shaping, all-optical signal processing and high-speed communication applications.

  15. Repetitive transcranial magnetic stimulator with controllable pulse parameters

    Science.gov (United States)

    Peterchev, Angel V.; Murphy, David L.; Lisanby, Sarah H.

    2011-06-01

    The characteristics of transcranial magnetic stimulation (TMS) pulses influence the physiological effect of TMS. However, available TMS devices allow very limited adjustment of the pulse parameters. We describe a novel TMS device that uses a circuit topology incorporating two energy storage capacitors and two insulated-gate bipolar transistor (IGBT) modules to generate near-rectangular electric field pulses with adjustable number, polarity, duration, and amplitude of the pulse phases. This controllable pulse parameter TMS (cTMS) device can induce electric field pulses with phase widths of 10-310 µs and positive/negative phase amplitude ratio of 1-56. Compared to conventional monophasic and biphasic TMS, cTMS reduces energy dissipation up to 82% and 57% and decreases coil heating up to 33% and 41%, respectively. We demonstrate repetitive TMS trains of 3000 pulses at frequencies up to 50 Hz with electric field pulse amplitude and width variability less than the measurement resolution (1.7% and 1%, respectively). Offering flexible pulse parameter adjustment and reduced power consumption and coil heating, cTMS enhances existing TMS paradigms, enables novel research applications and could lead to clinical applications with potentially enhanced potency.

  16. Efficient Pulsed Quadrupole

    CERN Document Server

    Petzenhauser, I.; Spiller, P.; Tenholt, C.

    2016-01-01

    In order to raise the focusing gradient in case of bunched beam lines, a pulsed quadrupole was designed. The transfer channels between synchrotrons as well as the final focusing for the target line are possible applications. The quadrupole is running in a pulsed mode, which means an immense saving of energy by avoiding standby operation. Still the high gradients demand high currents. Hence a circuit had to be developed which is able to recover a significant amount of the pulsing energy for following shots. The basic design of the electrical circuit of the quadrupole is introduced. Furthermore more energy efficient circuits are presented and the limits of adaptability are considered.

  17. Pulse joining cartridges

    Energy Technology Data Exchange (ETDEWEB)

    Golovashchenko, Sergey Fedorovich; Bonnen, John Joseph Francis

    2016-08-23

    A pulsed joining tool includes a tool body that defines a cavity that receives an inner tubular member and an outer tubular member and a pulse joining cartridge. The tubular members are nested together with the cartridge being disposed around the outer tubular member. The cartridge includes a conductor, such as a wire or foil, that extends around the outer tubular member and is insulated to separate a supply segment from a return segment. A source of stored electrical energy is discharged through the conductor to join the tubular members with an electromagnetic force pulse.

  18. DogPulse

    DEFF Research Database (Denmark)

    Skovgaard, Christoffer; Thomsen, Josephine Raun; Verdezoto, Nervo;

    2015-01-01

    This paper presents DogPulse, an ambient awareness system to support the coordination of dog walking among family members at home. DogPulse augments a dog collar and leash set to activate an ambient shape-changing lamp and visualize the last time the dog was taken for a walk. The lamp gradually...... changes its form and pulsates its lights in order to keep the family members aware of the dog walking activity. We report the iterative prototyping of DogPulse, its implementation and its preliminary evaluation. Based on our initial findings, we present the limitations and lessons learned as well...

  19. A Tesla-pulse forming line-plasma opening switch pulsed power generator

    Science.gov (United States)

    Novac, B. M.; Kumar, R.; Smith, I. R.

    2010-10-01

    A pulsed power generator based on a high-voltage Tesla transformer which charges a 3.85 Ω/55 ns water-filled pulse forming line to 300 kV has been developed at Loughborough University as a training tool for pulsed power students. The generator uses all forms of insulation specific to pulsed power technology, liquid (oil and water), gas (SF6), and magnetic insulation in vacuum, and a number of fast voltage and current sensors are implemented for diagnostic purposes. A miniature (centimeter-size) plasma opening switch has recently been coupled to the output of the pulse forming line, with the overall system comprising the first phase of a program aimed at the development of a novel repetitive, table-top generator capable of producing 15 GW pulses for high power microwave loads. Technical details of all the generator components and the main experimental results obtained during the program and demonstrations of their performance are presented in the paper, together with a description of the various diagnostic tools involved. In particular, it is shown that the miniature plasma opening switch is capable of reducing the rise time of the input current while significantly increasing the load power. Future plans are outlined in the conclusions.

  20. Optimal control of single flux quantum (SFQ) pulse sequences

    Science.gov (United States)

    Liebermann, Per; Wilhelm, Frank

    Single flux quantum (SFQ) pulses are a natural candidate for on-chip control of superconducting qubits. High accuracy quantum gates are accessible with quantum optimal control methods. We apply trains of SFQ pulses to operate single qubit gates, under the constraint of fixed amplitude and duration of each pulse. Timing of the control pulses is optimized using genetic algorithms and simulated annealing, decreasing the average fidelity errorby several orders of magnitude. Furthermore we are able to reduce the gate time to the quantum speed limit. Leakage out of the qubit subspace as well as timing errors of the pulses are considered, exploring the robustness of our optimized sequence.This takes usone step further to a scalable quantum processor

  1. Optimal Qubit Control Using Single-Flux Quantum Pulses

    Science.gov (United States)

    Liebermann, Per J.; Wilhelm, Frank K.

    2016-08-01

    Single-flux quantum pulses are a natural candidate for on-chip control of superconducting qubits. We show that they can drive high-fidelity single-qubit rotations—even in leaky transmon qubits—if the pulse sequence is suitably optimized. We achieve this objective by showing that, for these restricted all-digital pulses, genetic algorithms can be made to converge to arbitrarily low error, verified up to a reduction in gate error by 2 orders of magnitude compared to an evenly spaced pulse train. Timing jitter of the pulses is taken into account, exploring the robustness of our optimized sequence. This approach takes us one step further towards on-chip qubit controls.

  2. Ramsey-comb spectroscopy with intense ultrashort laser pulses

    CERN Document Server

    Morgenweg, Jonas; Eikema, Kjeld S E

    2014-01-01

    Optical frequency combs based on mode-locked lasers have revolutionised the field of metrology and precision spectroscopy by providing precisely calibrated optical frequencies and coherent pulse trains. Amplification of the pulsed output from these lasers is very desirable, as nonlinear processes can then be employed to cover a much wider range of transitions and wavelengths for ultra-high precision, direct frequency comb spectroscopy. Therefore full repetition rate laser amplifiers and enhancement resonators have been employed to produce up to microjoule-level pulse energies. Here we show that the full frequency comb accuracy and resolution can be obtained by using only two frequency comb pulses amplified to the millijoule pulse energy level, orders of magnitude more energetic than what has previously been possible. The novel properties of this approach, such as cancellation of optical light-shift effects, is demonstrated on weak two-photon transitions in atomic rubidium and caesium, thereby improving the fr...

  3. Photonic integrated circuit as a picosecond pulse timing discriminator.

    Science.gov (United States)

    Lowery, Arthur James; Zhuang, Leimeng

    2016-04-18

    We report the first experimental demonstration of a compact on-chip optical pulse timing discriminator that is able to provide an output voltage proportional to the relative timing of two 60-ps input pulses on separate paths. The output voltage is intrinsically low-pass-filtered, so the discriminator forms an interface between high-speed optics and low-speed electronics. Potential applications include timing synchronization of multiple pulse trains as a precursor for optical time-division multiplexing, and compact rangefinders with millimeter dimensions.

  4. Language Training: English Training

    CERN Multimedia

    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...

  5. Pulse subtraction Doppler

    Science.gov (United States)

    Mahue, Veronique; Mari, Jean Martial; Eckersley, Robert J.; Caro, Colin G.; Tang, Meng-Xing

    2010-01-01

    Recent advances have demonstrated the feasibility of molecular imaging using targeted microbubbles and ultrasound. One technical challenge is to selectively detect attached bubbles from those freely flowing bubbles and surrounding tissue. Pulse Inversion Doppler is an imaging technique enabling the selective detection of both static and moving ultrasound contrast agents: linear scatterers generate a single band Doppler spectrum, while non-linear scatterers generate a double band spectrum, one being uniquely correlated with the presence of contrast agents and non-linear tissue signals. We demonstrate that similar spectrums, and thus the same discrimination, can be obtained through a Doppler implementation of Pulse Subtraction. This is achieved by reconstructing a virtual echo using the echo generated from a short pulse transmission. Moreover by subtracting from this virtual echo the one generated from a longer pulse transmission, it is possible to fully suppress the echo from linear scatterers, while for non-linear scatterers, a signal will remain, allowing classical agent detection. Simulations of a single moving microbubble and a moving linear scatterer subject to these pulses show that when the virtual echo and the long pulse echo are used to perform pulsed Doppler, the power Doppler spectrum allows separation of linear and non-linear moving scattering. Similar results are obtained on experimental data acquired on a flow containing either microbubble contrast agents or linear blood mimicking fluid. This new Doppler method constitutes an alternative to Pulse Inversion Doppler and preliminary results suggest that similar dual band spectrums could be obtained by the combination of any non-linear detection technique with Doppler demodulation.

  6. Pulsed spallation Neutron Sources

    Energy Technology Data Exchange (ETDEWEB)

    Carpenter, J.M. [Argonne National Lab., IL (United States)

    1994-12-31

    This paper reviews the early history of pulsed spallation neutron source development at Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provides a few examples of applications in fundamental condensed matter physics, materials science and technology.

  7. Four pulse recoupling

    Science.gov (United States)

    Khaneja, Navin; Kumar, Ashutosh

    2016-11-01

    The paper describes a family of novel recoupling pulse sequences in magic angle spinning (MAS) solid state NMR, called four pulse recoupling. These pulse sequences can be employed for both homonuclear and heteronuclear recoupling experiments and are robust to dispersion in chemical shifts and rf-inhomogeneity. The homonuclear pulse sequence consists of a building block (π/2) 0 °(3π/2) ϕ°(π/2) 180 ° + ϕ°(3π/2) 180 ° where ϕ = π/n (ϕ° = 180°/n) , and n is number of blocks in a two rotor period. The heteronuclear recoupling pulse sequence consists of a building block (π/2) 0 °(3π/2) ϕ1 °(π/2) 180 ° +ϕ1 °(3π/2) 180 ° and (π/2) 0 °(3π/2) ϕ2 °(π/2) 180 ° +ϕ2 °(3π/2) 180 ° on channel I and S, where ϕ1 = 3π/2n, ϕ2 = π2/n and n is number of blocks in a two rotor period. The recoupling pulse sequences mix the y magnetization. We show that four pulse recoupling is more broadband compared to three pulse recoupling [1]. Experimental quantification of this method is shown for 13Cα-13CO, homonuclear recoupling in a sample of Glycine and 15N-13Cα, heteronuclear recoupling in Alanine. Application of this method is demonstrated on a sample of tripeptide N-formyl-[U-13C,15N]-Met-Leu-Phe-OH (MLF).

  8. Normal dispersion erbium-doped fiber laser with pulse energies above 10 nJ.

    Science.gov (United States)

    Ruehl, Axel; Kuhn, Vincent; Wandt, Dieter; Kracht, Dietmar

    2008-03-03

    We report on an erbium-doped fiber oscillator mode-locked by nonlinear polarization evolution operating in the large normal dispersion regime. The setup produced highly chirped 10 nJ pulses at 37 MHz which can be compressed externally to below 75 fs. Hence, this simple and practical setup is capable of providing ultrashort pulses with a peak power of 140 kW. The pulse formation is indeed subject to intrapulse Raman-scattering but a clean and stable pulse train can be observed. The similarities as well as the differences of the output characteristics to the parabolic pulse and wave breaking-free regime are explicated.

  9. Interferometer design and controls for pulse stacking in high power fiber lasers

    Science.gov (United States)

    Wilcox, Russell; Yang, Yawei; Dahlen, Dar; Xu, Yilun; Huang, Gang; Qiang, Du; Doolittle, Lawrence; Byrd, John; Leemans, Wim; Ruppe, John; Zhou, Tong; Sheikhsofla, Morteza; Nees, John; Galvanauskas, Almantas; Dawson, Jay; Chen, Diana; Pax, Paul

    2017-03-01

    In order to develop a design for a laser-plasma accelerator (LPA) driver, we demonstrate key technologies that enable fiber lasers to produce high energy, ultrafast pulses. These technologies must be scalable, and operate in the presence of thermal drift, acoustic noise, and other perturbations typical of an operating system. We show that coherent pulse stacking (CPS), which requires optical interferometers, can be made robust by image-relaying, multipass optical cavities, and by optical phase control schemes that sense pulse train amplitudes from each cavity. A four-stage pulse stacking system using image-relaying cavities is controlled for 14 hours using a pulse-pattern sensing algorithm. For coherent addition of simultaneous ultrafast pulses, we introduce a new scheme using diffractive optics, and show experimentally that four pulses can be added while a preserving pulse width of 128 fs.

  10. High voltage pulse generator

    Science.gov (United States)

    Fasching, George E.

    1977-03-08

    An improved high-voltage pulse generator has been provided which is especially useful in ultrasonic testing of rock core samples. An N number of capacitors are charged in parallel to V volts and at the proper instance are coupled in series to produce a high-voltage pulse of N times V volts. Rapid switching of the capacitors from the paralleled charging configuration to the series discharging configuration is accomplished by using silicon-controlled rectifiers which are chain self-triggered following the initial triggering of a first one of the rectifiers connected between the first and second of the plurality of charging capacitors. A timing and triggering circuit is provided to properly synchronize triggering pulses to the first SCR at a time when the charging voltage is not being applied to the parallel-connected charging capacitors. Alternate circuits are provided for controlling the application of the charging voltage from a charging circuit to be applied to the parallel capacitors which provides a selection of at least two different intervals in which the charging voltage is turned "off" to allow the SCR's connecting the capacitors in series to turn "off" before recharging begins. The high-voltage pulse-generating circuit including the N capacitors and corresponding SCR's which connect the capacitors in series when triggered "on" further includes diodes and series-connected inductors between the parallel-connected charging capacitors which allow sufficiently fast charging of the capacitors for a high pulse repetition rate and yet allow considerable control of the decay time of the high-voltage pulses from the pulse-generating circuit.

  11. A low-cost programmable pulse generator for physiology and behavior

    Directory of Open Access Journals (Sweden)

    Joshua I Sanders

    2014-12-01

    Full Text Available Precisely timed experimental manipulations of the brain and its sensory environment are often employed to reveal principles of brain function. While complex and reliable pulse trains for temporal stimulus control can be generated with commercial instruments, contemporary options remain expensive and proprietary. We have developed Pulse Pal, an open source device that allows users to create and trigger software-defined trains of voltage pulses with high temporal precision. Here we describe Pulse Pal’s circuitry and firmware, and characterize its precision and reliability. In addition, we supply online documentation with instructions for assembling, testing and installing Pulse Pal. While the device can be operated as a stand-alone instrument, we also provide application programming interfaces in several programming languages. As an inexpensive, flexible and open solution for temporal control, we anticipate that Pulse Pal will be used to address a wide range of instrumentation timing challenges in neuroscience research.

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

    Institute of Scientific and Technical Information of China (English)

    Xin Fu; Hongming Zhang; Meng Yan; Minyu Yao

    2009-01-01

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

  13. Synchronization of Fourier-Synthesized Optical Pulses to a Mode-Locked Optical Clock

    Institute of Scientific and Technical Information of China (English)

    Masaharu; Hyodo; Kazi; Sarwal; Abedin; Noriaki; Onodera; Masayoshi; Watanabe

    2003-01-01

    A Fourier-synthesized 40-GHz optical pulse train was successfully synchronized to an 8-GHz optical clock generated from a mode-locked fiber ring laser. The measured timing jitter of the synchronization was 0.43 ps.

  14. Discharge pulse phenomenology

    Science.gov (United States)

    Frederickson, A. R.

    1985-01-01

    A model was developed which places radiation induced discharge pulse results into a unified conceptual framework. Only two phenomena are required to interpret all space and laboratory results: (1) radiation produces large electrostatic fields inside insulators via the trapping of a net space charge density; and (2) the electrostatic fields initiate discharge streamer plasmas similar to those investigated in high voltage electrical insulation materials; these streamer plasmas generate the pulsing phenomena. The apparent variability and diversity of results seen is an inherent feature of the plasma streamer mechanism acting in the electric fields which is created by irradiation of the dielectrics. The implications of the model are extensive and lead to constraints over what can be done about spacecraft pulsing.

  15. Pulsed ELDOR detected NMR

    Science.gov (United States)

    Schosseler, P.; Wacker, Th.; Schweiger, A.

    1994-07-01

    A pulsed EPR method for the determination of small hyperfine interactions in disordered systems is described. A selective preparation pulse of frequency ω mw(1) excites allowed and forbidden transitions, thereby burning spectral holes into the EPR line. The positions of the holes caused by the excitation of forbidden transitions correspond to the nuclear transition frequencies of the spin system. A selective detection pulse of frequency ω mw(2) creates an FID with integrated intensity proportional to the magnetization at frequency ω mw(2). The entire hole pattern is obtained by recording the integrated intensity of the FID while varying the frequency difference Δω mw=ω mw(1)-ω mw(2) step by step.

  16. Herophilus on pulse

    Directory of Open Access Journals (Sweden)

    Afonasin, Eugene

    2015-01-01

    Full Text Available The first detailed study of the pulse (sphygmology is associated in antiquity with Herophilus (the end of the 4th century BCE, an Alexandrian physician, renowned for his anatomical discoveries. The scholars also attribute to him a discovery of a portable and adjustable water-clock, used for measuring ‘natural’ and ‘unnatural’ pulse and, accordingly, temperature of the patient. In the article we translate the principal ancient evidences and comment upon them. We study both the practical aspects of ancient sphygmology and the theoretical speculations associated with it. Ancient theory of proportion and musical harmony allowed to build a classification of the pulses, but the medical experience did not fit well in the Procrustean bed of this rather simple theory.

  17. Generation of Quality Pulses for Control of Qubit/Quantum Memory Spin States: Experimental and Simulation

    Science.gov (United States)

    2016-09-01

    10 16. Gain plot of DARPA SURF tunable band-pass filter tuned to 950-MHz .............................. 10 v 17. VSG at -50 dBm: Experimental... strength and the pulse duration with enough accuracy to control the spin states reliably. A rotation angle error arises from the inaccuracy of the pulse...gain. Figure 8 plots the simulation in red and a direct output from the VSG in blue. The VSG alone provides a high-quality pulse train with a 15-MHz

  18. Pulsed Artificial Electrojet Generation

    Science.gov (United States)

    Papadopoulos, K.

    2008-12-01

    Traditional techniques for generating low frequency signals in the ULF/ELF range (.1-100 Hz) and rely on ground based Horizontal Electric Dipole (HED) antennas. It is, furthermore, well known that a Vertical Electric Dipole (VED) is by more than 50 dB more efficient than a HED with the same dipole current moment. However, the prohibitively long length of VED antennas in the ELF/ULF range coupled with voltage limitations due to corona discharge in the atmosphere make them totally impracticable. In this paper we discuss a novel concept, inspired by the physics of the equatorial electrojet, that allows for the conversion of a ground based HED to a VED in the E-region of the equatorial ionosphere with current moment comparable to the driving HED. The paper focuses in locations near the dip-equator, where the earth's magnetic is in predominantly in the horizontal direction. The horizontal electric field associated with a pulsed HED drives a large Hall current in the ionospheric E-region, resulting in a vertical current. It is shown that the pulsed vertical current in the altitude range 80-130 km, driven by a horizontal electric field of, approximately, .1 mV/m at 100 km altitude, is of the order of kA. This results in a pulsed VED larger than 106 A-m. Such a pulsed VED will drive ELF/ULF pulses with amplitude in excess of .1 nT at a lateral range larger than few hundred kilometers. This is by three orders of magnitude larger than the one expected by a HED with comparable current moment. The paper will conclude with the description of a sneak-through technique that allows for creating pulsed electric fields in the ionosphere much larger than expected from steady state oscillatory HED antennas.

  19. Two pulse recoupling

    Science.gov (United States)

    Khaneja, Navin; Kumar, Ashutosh

    2017-08-01

    The paper describes a family of novel recoupling pulse sequences in magic angle spinning (MAS) solid state NMR, called two pulse recoupling. These pulse sequences can be employed for both homonuclear and heteronuclear recoupling experiments and are robust to dispersion in chemical shifts and rf-inhomogeneity. The homonuclear pulse sequence consists of a building block (π)ϕ(π) - ϕ where ϕ =π/4n, and n is number of blocks in a rotor period. The recoupling block is made robust to rf-inhomogeneity by extending it to (π)ϕ(π) - ϕ(π) π + ϕ(π) π - ϕ . The heteronuclear recoupling pulse sequence consists of a building block (π)ϕ1(π)-ϕ1 and (π)ϕ2(π)-ϕ2 on channel I and S, where ϕ1 = 3π/8n, ϕ2 = π/8n and n is number of blocks in a rotor period. The recoupling block is made robust to rf-inhomogeneity by extending it to (π)ϕ1(π)-ϕ1(π) π +ϕ1(π) π -ϕ1 and (π)ϕ2(π)-ϕ2(π) π +ϕ2(π) π -ϕ2 on two channels respectively. The recoupling pulse sequences mix the z magnetization. Experimental quantification of this method is shown for 13Cα-13CO homonuclear recoupling in a sample of Glycine and 15N-13Cα heteronuclear recoupling in Alanine. Application of this method is demonstrated on a sample of tripeptide N-formyl-[U-13C,15N]-Met-Leu-Phe-OH (MLF). Compared to R-sequences (Levitt, 2002), these sequences are more robust to rf-inhomogeneity and give better sensitivity, as shown in Fig. 3.

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

    DEFF Research Database (Denmark)

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

    1999-01-01

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

  1. Pulse Extinction Ratio Improvement Using SPM in an SOA for OTDM Systems Applications

    DEFF Research Database (Denmark)

    Nielsen, Mads Lønstrup; Olsson, B.-E.; Blumenthal, D. J.

    2002-01-01

    Improvement of pulse extinction ratio from 15-20 dB to approximately 40 dB of a 10-GHz pulse train is demonstrated using the self-phase modulation-induced spectral shift caused by a semiconductor optical amplifier (SOA). The improvement permits penalty-free optical time-division multiplexing to 40...

  2. Spectral development of pico second pulses of mode-locked Nd-glass lasers

    Energy Technology Data Exchange (ETDEWEB)

    Penzkofer, A.; Weinhardt, N.

    1983-04-01

    The spectra of single picosecond pulses of mode-locked Nd-glass lasers are investigated along the pulse train. In addition to self-phase modulation, the spectra are modified due to spectral hole burning in the inhomogeneous gain profile of the active medium.

  3. An investigation of the spectral content of a mode-locked pulsed CO2 laser

    NARCIS (Netherlands)

    Bormans, B.J.M.; Olbertz, A.H.M.

    1980-01-01

    The frequency width of a pulse train in a pulsed mode-locked CO2 laser has been accurately measured by means of a Fabry-Perot interferometer. We succeeded in resolving the longitudinal mode structure. The results are in excellent agreement with the results of previous measurements of the line width

  4. Pulse Doppler radar

    CERN Document Server

    Alabaster, Clive

    2012-01-01

    This book is a practitioner's guide to all aspects of pulse Doppler radar. It concentrates on airborne military radar systems since they are the most used, most complex, and most interesting of the pulse Doppler radars; however, ground-based and non-military systems are also included. It covers the fundamental science, signal processing, hardware issues, systems design and case studies of typical systems. It will be a useful resource for engineers of all types (hardware, software and systems), academics, post-graduate students, scientists in radar and radar electronic warfare sectors and milit

  5. Pulsed Electron Holography

    CERN Document Server

    Germann, Matthias; Escher, Conrad; Fink, Hans-Werner

    2013-01-01

    A technique of pulsed low-energy electron holography is introduced that allows for recording highly resolved holograms within reduced exposure times. Therefore, stacks of holograms are accumulated in a pulsed mode with individual acquisition times as short as 50 {\\mu}s. Subsequently, these holograms are aligned and finally superimposed. The resulting holographic record reveals previously latent high-order interference fringes and thereby pushing interference resolution into the sub-nanometer regime. In view of the non-damaging character of low-energy electrons, the method is of particular interest for structural analysis of fragile biomolecules.

  6. Language Training - French Training

    CERN Multimedia

    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...

  7. Language Training: English Training

    CERN Multimedia

    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 ...

  8. Language Training: English Training

    CERN Multimedia

    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...

  9. Language Training: English Training

    CERN Multimedia

    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...

  10. Language Training: English Training

    CERN Multimedia

    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...

  11. Laser induced periodic surface structuring on Si by temporal shaped femtosecond pulses.

    Science.gov (United States)

    Almeida, G F B; Martins, R J; Otuka, A J G; Siqueira, J P; Mendonca, C R

    2015-10-19

    We investigated the effect of temporal shaped femtosecond pulses on silicon laser micromachining. By using sinusoidal spectral phases, pulse trains composed of sub-pulses with distinct temporal separations were generated and applied to the silicon surface to produce Laser Induced Periodic Surface Structures (LIPSS). The LIPSS obtained with different sub-pulse separation were analyzed by comparing the intensity of the two-dimensional fast Fourier Transform (2D-FFT) of the AFM images of the ripples (LIPSS). It was observed that LIPSS amplitude is more emphasized for the pulse train with sub-pulses separation of 128 fs, even when compared with the Fourier transform limited pulse. By estimating the carrier density achieved at the end of each pulse train, we have been able to interpret our results with the Sipe-Drude model, that predicts that LIPSS efficacy is higher for a specific induced carrier density. Hence, our results indicate that temporal shaping of the excitation pulse, performed by spectral phase modulation, can be explored in fs-laser microstructuring.

  12. SNMR pulse sequence phase cycling

    Science.gov (United States)

    Walsh, David O; Grunewald, Elliot D

    2013-11-12

    Technologies applicable to SNMR pulse sequence phase cycling are disclosed, including SNMR acquisition apparatus and methods, SNMR processing apparatus and methods, and combinations thereof. SNMR acquisition may include transmitting two or more SNMR pulse sequences and applying a phase shift to a pulse in at least one of the pulse sequences, according to any of a variety cycling techniques. SNMR processing may include combining SNMR from a plurality of pulse sequences comprising pulses of different phases, so that desired signals are preserved and indesired signals are canceled.

  13. Anisotropy modulations of femtosecond laser pulse induced periodic surface structures on silicon by adjusting double pulse delay.

    Science.gov (United States)

    Han, Weina; Jiang, Lan; Li, Xiaowei; Wang, Qingsong; Li, Hao; Lu, YongFeng

    2014-06-30

    We demonstrate that the polarization-dependent anisotropy of the laser-induced periodic surface structure (LIPSS) on silicon can be adjusted by designing a femtosecond laser pulse train (800 nm, 50 fs, 1 kHz). By varying the pulse delay from 100 to 1600 fs within a double pulse train to reduce the deposited pulse energy, which weakens the directional surface plasmon polarition (SPP)-laser energy coupling based on the initial formed ripple structure, the polarization-dependent geometrical morphology of the LIPSS evolves from a nearly isotropic circular shape to a somewhat elongated elliptical shape. Meanwhile, the controllable anisotropy of the two-dimensional scanned-line widths with different directions is achieved based on a certain pulse delay combined with the scanning speed. This can effectively realize better control over large-area uniform LIPSS formation. As an example, we further show that the large-area LIPSS can be formed with different scanning times under different pulse delays.

  14. Strength Training

    Science.gov (United States)

    ... strengthens your heart and lungs. When you strength train with weights, you're using your muscles to ... see there are lots of different ways to train with weights. Try a few good basic routines ...

  15. Pulse distortion in single-mode fibers. 3: Chirped pulses.

    Science.gov (United States)

    Marcuse, D

    1981-10-15

    The theory of pulse distortion in single-mode fibers is extended to include laser sources that suffer a linear wavelength sweep (chirp) during the duration of the pulse. The transmitted pulse is expressed as a Fourier integral whose spectral function is given by an analytical expression in closed form. The rms width of the transmitted pulse is also expressed in closed form. Numerical examples illustrate the influence of the chirp on the shape and rms width of the pulse. A somewhat paradoxical situation exists. A given input pulse can be made arbitrarily short by a sufficiently large amount of chirping, and, after a given fiber length, this chirped pulse returns to its original width. But at this particular distance an unchirped pulse would be only [equiation] times longer. Thus chirping can improve the rate of data transmission by only 40%.

  16. Solid-state pulse forming module with adjustable pulse duration

    Science.gov (United States)

    Wang, Langning; Liu, Jinliang; Qiu, Yongfeng; Chu, Xu; Zhang, Qingmeng

    2017-03-01

    A new solid-state pulse forming module is described in this paper. The pulse forming module is fabricated on a glass ceramic substrate, with the dimension of 250 mm × 95 mm × 4 mm. By changing the copper strips used in the pulse forming modules, the pulse duration of the obtained pulsed can range from 80 ns to 140 ns. Both the simulation and tests show that the pulse forming module has a good pulse forming ability. Under a high voltage in microsecond's time, the new pulse forming modules can hold off a voltage up to 25 kV higher than that of the previous study. In addition, future optimization for the field enhancement near the thin electrode edge has been proposed and simulated.

  17. Novel Method of Unambiguous Moving Target Detection in Pulse-Doppler Radar with Random Pulse Repetition Interval

    Directory of Open Access Journals (Sweden)

    Liu Zhen

    2012-03-01

    Full Text Available Blind zones and ambiguities in range and velocity measurement are two important issues in traditional pulse-Doppler radar. By generating random deviations with respect to a mean Pulse Repetition Interval (PRI, this paper proposes a novel algorithm of Moving Target Detection (MTD based on the Compressed Sensing (CS theory, in which the random deviations of the PRIare converted to the Restricted Isometry Property (RIP of the observing matrix. The ambiguities of range and velocity are eliminated by designing the signal parameters. The simulation results demonstrate that this scheme has high performance of detection, and there is no ambiguity and blind zones as well. It can also shorten the coherent processing interval compared to traditional staggered PRI mode because only one pulse train is needed instead of several trains.

  18. Ultrafast optomechanical pulse picking

    Science.gov (United States)

    Lilienfein, Nikolai; Holzberger, Simon; Pupeza, Ioachim

    2017-01-01

    State-of-the-art optical switches for coupling pulses into and/or out of resonators are based on either the electro-optic or the acousto-optic effect in transmissive elements. In high-power applications, the damage threshold and other nonlinear and thermal effects in these elements impede further improvements in pulse energy, duration, and average power. We propose a new optomechanical switching concept which is based solely on reflective elements and is suitable for switching times down to the ten-nanosecond range. To this end, an isolated section of a beam path is moved in a system comprising mirrors rotating at a high angular velocity and stationary imaging mirrors, without affecting the propagation of the beam thereafter. We discuss three variants of the concept and exemplify practical parameters for its application in regenerative amplifiers and stack-and-dump enhancement cavities. We find that optomechanical pulse picking has the potential to achieve switching rates of up to a few tens of kilohertz while supporting pulse energies of up to several joules.

  19. Pulsed electric fields

    Science.gov (United States)

    The concept of pulsed electric fields (PEF) was first proposed in 1967 to change the behavior or microorganisms. The electric field phenomenon was identified as membrane rupture theory in the 1980s. Increasing the membrane permeability led to the application of PEF assisted extraction of cellular co...

  20. Pulsed inductive HF laser

    Energy Technology Data Exchange (ETDEWEB)

    Razhev, A M; Kargapol' tsev, E S [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation); Churkin, D S; Demchuk, S V [Novosibirsk State University, Novosibirsk (Russian Federation)

    2016-03-31

    We report the results of experimentally investigated dependences of temporal, spectral and spatial characteristics of an inductive HF-laser generation on the pump conditions. Gas mixtures H{sub 2} – F{sub 2}(NF{sub 3} or SF6{sub 6}) and He(Ne) – H{sub 2} – F{sub 2}(NF{sub 3} or SF{sub 6}) were used as active media. The FWHM pulse duration reached 0.42 μs. This value corresponded to a pulsed power of 45 kW. For the first time, the emission spectrum of an inductive HF laser was investigated, which consisted of seven groups of bands with centres around the wavelengths of 2732, 2736, 2739, 2835, 2837, 2893 and 2913 nm. The cross section profile of the laser beam was a ring with a diameter of about 20 mm and width of about 5 mm. Parameters of laser operation in the repetitively pulsed regime were sufficiently stable. The amplitude instability of light pulses was no greater than 5% – 6%. (lasers)

  1. Downhole pulse tube refrigerators

    Energy Technology Data Exchange (ETDEWEB)

    Swift, G.; Gardner, D. [Los Alamos National Lab., NM (United States). Condensed Matter and Thermal Physics Group

    1997-12-01

    This report summarizes a preliminary design study to explore the plausibility of using pulse tube refrigeration to cool instruments in a hot down-hole environment. The original motivation was to maintain Dave Reagor`s high-temperature superconducting electronics at 75 K, but the study has evolved to include three target design criteria: cooling at 30 C in a 300 C environment, cooling at 75 K in a 50 C environment, cooling at both 75 K and 30 C in a 250 C environment. These specific temperatures were chosen arbitrarily, as representative of what is possible. The primary goals are low cost, reliability, and small package diameter. Pulse-tube refrigeration is a rapidly growing sub-field of cryogenic refrigeration. The pulse tube refrigerator has recently become the simplest, cheapest, most rugged and reliable low-power cryocooler. The authors expect this technology will be applicable downhole because of the ratio of hot to cold temperatures (in absolute units, such as Kelvin) of interest in deep drilling is comparable to the ratios routinely achieved with cryogenic pulse-tube refrigerators.

  2. Bandpass calibration of a wideband spectrometer using pulse injection

    CERN Document Server

    Patra, Nipanjana; Ekers, Ron; Roberts, Paul

    2015-01-01

    We present a novel time domain concept for determining the bandpass response of a system by injecting a nanosecond pulse and capturing the system voltage output. A pulse of sub-nanosecond duration contains all frequency components with constant amplitude up to 1~GHz. Hence, this method can accurately determine the system bandpass response to a broadband signal. A train of pulses are coherently accumulated providing very high signal-to-noise calibration. The basic concept is demonstrated using a pulse generator-accumulator setup realised in a Bedlam board which is a high speed digital signal processing unit. The same system was used at the Parkes Radio Telescope between 2--13 October 2013 and we demonstrate its powerful diagnostic capability. We also present some initial test data from this experiment.

  3. Relativistic Doppler effect: universal spectra and zeptosecond pulses.

    Science.gov (United States)

    Gordienko, S; Pukhov, A; Shorokhov, O; Baeva, T

    2004-09-10

    We report on a numerical observation of the train of zeptosecond pulses produced by the reflection of a relativistically intense femtosecond laser pulse from the oscillating boundary of an overdense plasma because of the Doppler effect. These pulses promise to become unique experimental and technological tools since their length is of the order of the Bohr radius and the intensity is extremely high proportional, variant 10(19) W/cm(2). We present the physical mechanism, analytical theory, and direct particle-in-cell simulations. We show that the harmonic spectrum is universal: the intensity of nth harmonic scales as 1/n(p) for n<4gamma(2), where gamma is the largest gamma factor of the electron fluid boundary, and p=3 and p=5/2 for the broadband and quasimonochromatic laser pulses, respectively.

  4. Bandpass calibration of a wideband spectrometer using coherent pulse injection

    Science.gov (United States)

    Patra, Nipanjana; Bray, Justin D.; Roberts, Paul; Ekers, Ron D.

    2017-03-01

    We present a relatively simple time domain method for determining the bandpass response of a system by injecting a nanosecond pulse and capturing the system voltage output. A pulse of sub-nanosecond duration contains all frequency components with nearly constant amplitude up to 1 GHz. Hence, this method can accurately determine the system bandpass response to a broadband signal. In a novel variation on this impulse response method, a train of pulses is coherently accumulated providing precision calibration with a simple system. The basic concept is demonstrated using a pulse generator-accumulator setup realised in a Bedlam board which is a high speed digital signal processing unit. The same system was used at the Parkes radio telescope between 2-13 October 2013 and we demonstrate its powerful diagnostic capability. We also present some initial test data from this experiment.

  5. Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers

    CERN Document Server

    Yao, B C; Wang, Z N; Wu, Y; Zhou, J H; Wu, H; Fan, M Q; Cao, X L; Zhang, W L; Chen, Y F; Li, Y R; Churkin, D; Turitsyn, S; Wong, C W

    2015-01-01

    Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse for...

  6. Coupled Optoelectronic Oscillators:. Application to Low-Jitter Pulse Generation

    Science.gov (United States)

    Yu, N.; Tu, M.; Maleki, L.

    2002-04-01

    Actively mode-locked Erbium-doped fiber lasers (EDFL) have been studied for generating stable ultra-fast pulses ( 5 GHz) [1,2]. These devices can be compact and environmentally stable, quite suitable for fiber-based high-data-rate communications and optical ultra-fast analog-to-digital conversions (ADC) [3]. The pulse-to-pulse jitter of an EDFL-based pulse generator will be ultimately limited by the phase noise of the mode-locking microwave source (typically electronic frequency synthesizers). On the other hand, opto-electronic oscillators (OEO) using fibers have been demonstrated to generate ultra-low phase noise microwaves at 10 GHz and higher [4]. The overall phase noise of an OEO can be much lower than commercially available synthesizers at the offset-frequency range above 100 Hz. Clearly, ultra-low jitter pulses can be generated by taking advantage of the low phase noise of OEOs. In this paper, we report the progress in developing a new low-jitter pulse generator by combing the two technologies. In our approach, the optical oscillator (mode-locked EDFL) and the microwave oscillator (OEO) are coupled through a common Mach-Zehnder (MZ) modulator, thus named coupled opto-electronic oscillator (COEO) [5]. Based on the results of previous OEO study, we can expect a 10 GHz pulse train with jitters less than 10 fs.

  7. Sequentially pulsed traveling wave accelerator

    Science.gov (United States)

    Caporaso, George J.; Nelson, Scott D.; Poole, Brian R.

    2009-08-18

    A sequentially pulsed traveling wave compact accelerator having two or more pulse forming lines each with a switch for producing a short acceleration pulse along a short length of a beam tube, and a trigger mechanism for sequentially triggering the switches so that a traveling axial electric field is produced along the beam tube in synchronism with an axially traversing pulsed beam of charged particles to serially impart energy to the particle beam.

  8. Bacterial inactivation using pulsed light

    OpenAIRE

    Elmnasser, Noura; Ritz, Magali; Leroi, Francoise; Orange, Nicole; Bakhrouf, Amina; Federighi, Michel

    2007-01-01

    Pulsed light is a new method intended for the decontamination of food surfaces using short, high frequency pulses of an intense broad spectrum. The effects of broad spectrum pulsed light on the survival of Listeria monocytogenes Scott A, Listeria monocytogenes CNL, Pseudomonas fluorescens MF37 and Photobacterium phosphoreum SF680 populations on agar and in a liquid medium were investigated during this study. The sterilisation system generated 1.5 J cm(-2) per pulse with eight lamps for 300 mu...

  9. A THERMAL PULSE SHAPER MECHANISM.

    Science.gov (United States)

    A shaped pulse of intense thermal radiation, corresponding to the pulses from nuclear weapons, is obtained by the output of a QM carbon arc. A flywheel driven by a DC motor actuated a venetian blind shutter placed between a mirror and the target to control the flux. The combination produced reasonably good simulation and reproduction of the generalized field pulse.

  10. Language Training - English Training

    CERN Multimedia

    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...

  11. Language Training - English Training

    CERN Multimedia

    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 ...

  12. Micro pulse laser radar

    Science.gov (United States)

    Spinhirne, James D. (Inventor)

    1993-01-01

    An eye safe, compact, solid state lidar for profiling atmospheric cloud and aerosol scattering is disclosed. The transmitter of the micro pulse lidar is a diode pumped micro-J pulse energy, high repetition rate Nd:YLF laser. Eye safety is obtained through beam expansion. The receiver employs a photon counting solid state Geiger mode avalanche photodiode detector. Data acquisition is by a single card multichannel scaler. Daytime background induced quantum noise is controlled by a narrow receiver field-of-view and a narrow bandwidth temperature controlled interference filter. Dynamic range of the signal is limited to optical geometric signal compression. Signal simulations and initial atmospheric measurements indicate that micropulse lider systems are capable of detecting and profiling all significant cloud and aerosol scattering through the troposphere and into the stratosphere. The intended applications are scientific studies and environmental monitoring which require full time, unattended measurements of the cloud and aerosol height structure.

  13. Magnetic Pulse Welding Technology

    Directory of Open Access Journals (Sweden)

    Ahmad K. Jassim

    2011-12-01

    Full Text Available In this paper, the benefits of using Magnetic Pulse machine which is belong to Non-conventional machine instead of conventional machine. Magnetic Pulse Technology is used for joining dissimilar metals, and for forming and cutting metals. It is a non contact technique. Magnetic field is used to generate impact magnetic pressure for welding and forming the work piece by converted the electrical energy to mechanical energy. It is enable us to design previously not possible by welding dissimilar materials and allowing to welds light and stronger materials together. It can be used to weld metallic with non metallic materials to created mechanical lock on ceramics, polymers, rubbers and composites. It is green process; there is no heat, no radiation, no gas, no smoke and sparks, therefore the emissions are negligible.

  14. Measurement of pulse lengthening with pulse energy increase in picosecond Nd:YAG laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Cutolo, A.; Zeni, L.; Berardi, V.; Bruzzese, R.; Solimeno, S.; Spinelli, N.

    1989-03-15

    Taking advantage of a new technique, we have monitored the relative variations of time duration and mode size as a function of the pulse energy for 30-ps-long Nd:YAG laser pulses. In particular, by carrying out a statistical analysis, we have observed that the pulse time duration is an increasing function of the pulse energy, according to the theoretical modeling of passively mode-locked lasers. The measurements can be easily extended to the femtosecond regime.

  15. Twitter's visual pulse

    OpenAIRE

    Hare, Jonathon; Samangooei, Sina; Dupplaw, David; Lewis, Paul H.

    2013-01-01

    Millions of images are tweeted every day, yet very little research has looked at the non-textual aspect of social media communication. In this work we have developed a system to analyse streams of image data. In particular we explore trends in similar, related, evolving or even duplicated visual artefacts in the mass of tweeted image data — in short, we explore the visual pulse of Twitter.

  16. Pulse Portraiture: Pulsar timing

    Science.gov (United States)

    Pennucci, Timothy T.; Demorest, Paul B.; Ransom, Scott M.

    2016-06-01

    Pulse Portraiture is a wideband pulsar timing code written in python. It uses an extension of the FFTFIT algorithm (Taylor 1992) to simultaneously measure a phase (TOA) and dispersion measure (DM). The code includes a Gaussian-component-based portrait modeling routine. The code uses the python interface to the pulsar data analysis package PSRCHIVE (ascl:1105.014) and also requires the non-linear least-squares minimization package lmfit (ascl:1606.014).

  17. STUCTURE OF PULSED BED

    Directory of Open Access Journals (Sweden)

    I. A. Bokun

    2014-01-01

    Full Text Available The structure of pulsed layer is proposed which can be suggested as a state of particulates that is blown by intermittent gas flow with speed which has the force to start material moving. Layer during one cycle is in a suspension, falling down and immobile state resulting in changes of particles arrangement as well as ways of gas flowing through layer. Moreover, it allows carrying out effective interphase heat exchange even adamant real granulation.The process of formation of impact flows is considered aw well as their influence on formation of air bubbles in pulsed layer. At startup of air blast the balance between the force of hydro-dynamic resistance is broken, on one side, and forces of gravity, particles inertia and their links with walls on the other side. The layer is transferred in the state of pulsed pseudo-fluidization, and presents gas-disperse mixture, inside of which impulse of pressure increasing is spreading to all sides as pressure waves (compression. These waves are the sources of impact flows’ formation, the force of which is two times more than during the stationary flow.The waves of pressure are divided into weak and strong ones depending on movement velocity within gas-disperse system. Weak waves are moving with a sound speed and strong ones in active phase of pulsed layer are moving over the speed of sound limit within gas-disperse system. The peculiarity of strong wave is that parameters of system (pressure, density and others are changing in discrete steps.The article describes the regime of layer’s falling down in the passive stage of cycle, which begins after finishing of gas impulse action. And suspension layer of moving up granular material is transferred in the state of falling resulting in change of the layer structure.

  18. Downhole pulse radar

    Science.gov (United States)

    Chang, Hsi-Tien

    1987-09-28

    A borehole logging tool generates a fast rise-time, short duration, high peak-power radar pulse having broad energy distribution between 30 MHz and 300 MHz through a directional transmitting and receiving antennas having barium titanate in the electromagnetically active region to reduce the wavelength to within an order of magnitude of the diameter of the antenna. Radar returns from geological discontinuities are sampled for transmission uphole. 7 figs.

  19. Ptychographic ultrafast pulse reconstruction

    CERN Document Server

    Spangenberg, D; Brügmann, M H; Feurer, T

    2014-01-01

    We demonstrate a new ultrafast pulse reconstruction modality which is somewhat reminiscent of frequency resolved optical gating but uses a modified setup and a conceptually different reconstruction algorithm that is derived from ptychography. Even though it is a second order correlation scheme it shows no time ambiguity. Moreover, the number of spectra to record is considerably smaller than in most other related schemes which, together with a robust algorithm, leads to extremely fast convergence of the reconstruction.

  20. PULSE Pilot Certification Results

    Directory of Open Access Journals (Sweden)

    Pamela Pape-Lindstrom

    2015-08-01

    Full Text Available The pilot certification process is an ambitious, nationwide endeavor designed to motivate important changes in life sciences education that are in line with the recommendations of the 2011 Vision and Change Report: A Call to Action (American Association for the Advancement of Science [AAAS], 2011.  It is the goal of the certification process to acknowledge departments that have progressed towards full implementation of the tenets of Vision and Change and to motivate departments that have not begun to adopt the recommendations to consider doing so.  More than 70 life science departments applied to be part of the pilot certification process, funded by a National Science Foundation grant, and eight were selected based on initial evidence of transformed and innovative educational practices.  The programs chosen represent a wide variety of schools, including two-year colleges, liberal-arts institutions, regional comprehensive colleges, research universities and minority serving institutions.  Outcomes from this pilot were released June 1, 2015 (www.pulsecommunity.org, with all eight programs being recognized as having progressed along a continuum of change.  Five levels of achievement were defined as PULSE Pilot Progression Levels.  Of the eight departments in the pilot, one achieved “PULSE Progression Level III: Accomplished”.  Six departments achieved “PULSE Progression Level II: Developing” and one pilot department achieved “PULSE Progression Level I: Beginning”.  All of the schools have made significant movement towards the recommendations of Vision and Change relative to a traditional life sciences curriculum.  Overall, the response from the eight pilot schools has been positive. 

  1. Intense ultrashort pulse generation using the JAERI far-infrared free electron laser

    CERN Document Server

    Nagai, R; Nishimori, N; Kikuzawa, N; Sawamura, M; Minehara, E J

    2002-01-01

    An intense ultrashort optical pulse has been quasi-continuously generated using a superconducting RF linac-based free-electron laser at a wavelength of 22.5 mu m. The pulse shape and width are measured by second-order optical autocorrelation with a birefringent Te crystal. At synchronism of the optical resonator, the pulse shape is a smooth single pulse with an FWHM width of 255 fs and energy of 74 mu J. A train of subpulses is developed by increasing the desynchronism of the optical resonator. The measured results are in good agreement with numerical simulation.

  2. Information Fusing Recognition of Traditional Chinese Medicine (TCM) Pulse State Based on Stochastic Fuzzy Neural Network

    Institute of Scientific and Technical Information of China (English)

    QIN Jian; LIU Hong-jian; DENG Wei; WU Guo-zhen; CHEN Shu-qing; JING Ming-hua

    2005-01-01

    Based on the fuzzy characteristic of the pulse state and syndromes differentiation thinking mode of TCM, an information fusing recognition method of pulse states based on SFNN (Stochastic Fuzzy Neural Network) is presented in this paper. With the learning ability in parameters and structure, SFNN fuses the measurement information of three pulse-state sensors distributed in Cun, Guan,and Chi location of body for the pulse state recognition. The experimental results show that the percentage of correct recognition with new method is higher than that by single-data recognition one, with fewer off-line train numbers.

  3. Proof-of-principle pilot study of oropharyngeal air-pulse application in individuals with dysphagia after hemispheric stroke.

    Science.gov (United States)

    Theurer, Julie A; Johnston, Jennifer L; Fisher, James; Darling, Sherry; Stevens, Rebecca C; Taves, Donald; Teasell, Robert; Hachinski, Vladimir; Martin, Ruth E

    2013-06-01

    To test the hypothesis that oropharyngeal air-pulse application is associated with increased swallowing rates in individuals with dysphagia secondary to stroke. Case control. Stroke rehabilitation hospital or home setting. Convenience sample of individuals (N=8) with new-onset dysphagia after stroke. Air-pulse trains were applied to the oropharynx of 8 subjects who presented with dysphagia after hemispheric stroke. Resting swallowing rates were determined for 5 experimental conditions: baseline without air-pulse mouthpiece, baseline with mouthpiece in situ, unilateral right oropharyngeal air-pulse, unilateral left oropharyngeal air-pulse, and bilateral oropharyngeal air-pulse application. Individual swallowing responses were analyzed using a 2-SD band method. Swallowing rate (swallows/min). Swallowing rates associated with bilateral air-pulse application were greater than baseline in 4 of the 8 subjects. The 4 subjects who demonstrated this response to air-pulse application had greater baseline swallowing rates than did subjects whose swallowing rates were not altered in association with air-pulse application. Oropharyngeal air-pulse trains can be applied in individuals with swallowing impairment. Air-pulse application is associated with increased resting swallowing rates in some individuals with dysphagia secondary to hemispheric stroke. Further research should extend this proof-of-principle study by examining the efficacy of oropharyngeal air-pulse application in terms of improved swallowing and related outcomes in dysphagic stroke through a large randomized trial. Copyright © 2013 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-22

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

  5. Petawatt pulsed-power accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Stygar, William A. (Albuquerque, NM); Cuneo, Michael E. (Albuquerque, NM); Headley, Daniel I. (Albuquerque, NM); Ives, Harry C. (Albuquerque, NM); Ives, legal representative; Berry Cottrell (Albuquerque, NM); Leeper, Ramon J. (Albuquerque, NM); Mazarakis, Michael G. (Albuquerque, NM); Olson, Craig L. (Albuquerque, NM); Porter, John L. (Sandia Park, NM); Wagoner; Tim C. (Albuquerque, NM)

    2010-03-16

    A petawatt pulsed-power accelerator can be driven by various types of electrical-pulse generators, including conventional Marx generators and linear-transformer drivers. The pulsed-power accelerator can be configured to drive an electrical load from one- or two-sides. Various types of loads can be driven; for example, the accelerator can be used to drive a high-current z-pinch load. When driven by slow-pulse generators (e.g., conventional Marx generators), the accelerator comprises an oil section comprising at least one pulse-generator level having a plurality of pulse generators; a water section comprising a pulse-forming circuit for each pulse generator and a level of monolithic triplate radial-transmission-line impedance transformers, that have variable impedance profiles, for each pulse-generator level; and a vacuum section comprising triplate magnetically insulated transmission lines that feed an electrical load. When driven by LTD generators or other fast-pulse generators, the need for the pulse-forming circuits in the water section can be eliminated.

  6. Pulse Distributing Manifold; Pulse Distributing Manifold

    Energy Technology Data Exchange (ETDEWEB)

    Schutting, Eberhard [Technische Univ. Graz (Austria); Sams, Theodor [AVL List GmbH, Graz (Austria); Glensvig, Michael [Forschungsgesellschaft mbH, Graz (AT). Kompetenzzentrum ' ' Das virtuelle Fahrzeug' ' (VIF)

    2011-07-01

    The Pulse Distributing Manifold is a new charge exchange method for turbocharged diesel engines with exhaust gas recirculation (EGR). The method is characterized in that the EGR mass flow is not diverted from the exhaust gas mass flow continuously, but over time broken into sub-streams. The temporal interruption is achieved by two phase-shifted outlet valves which are connected via separate manifolds only with the turbocharger or only with the EGR path. The time points of valve opening are chosen such that the turbocharger and the aftertreatment process of exhaust gas is perfused by high-energy exhaust gas of the blowdown phase while cooler and less energy-rich exhaust gas of the exhaust period is used for the exhaust gas recirculation. This increases the enthalpy for the turbocharger and the temperature for the exhaust gas treatment, while the cooling efficiency at the EGR cooler is reduced. The elimination of the continuous EGR valve has a positive effect on pumping losses. The principle functioning and the potential of this system could be demonstrated by means of a concept study using one-dimensional simulations. Without disadvantages in fuel consumption for the considered commercial vehicle engine, a reduction the EGR cooler performance by 15 % and an increase in exhaust temperature of 35 K could be achieved. The presented charge exchange method was developed, evaluated and patented within the scope of the research program 'K2-mobility' of the project partners AVL (Mainz, Federal Republic of Germany) and University of Technology Graz (Austria). The research project 'K2-Mobility' is supported by the competence center 'The virtual vehicle' Forschungsgesellschaft mbH (Graz, Austria).

  7. Electric control of exchange bias training.

    Science.gov (United States)

    Echtenkamp, W; Binek, Ch

    2013-11-01

    Voltage-controlled exchange bias training and tunability are introduced. Isothermal voltage pulses are used to reverse the antiferromagnetic order parameter of magnetoelectric Cr(2)O(3), and thus continuously tune the exchange bias of an adjacent CoPd film. Voltage-controlled exchange bias training is initialized by tuning the antiferromagnetic interface into a nonequilibrium state incommensurate with the underlying bulk. Interpretation of these hitherto unreported effects contributes to new understanding in electrically controlled magnetism.

  8. Electric Control of Exchange Bias Training

    Science.gov (United States)

    Echtenkamp, W.; Binek, Ch.

    2013-11-01

    Voltage-controlled exchange bias training and tunability are introduced. Isothermal voltage pulses are used to reverse the antiferromagnetic order parameter of magnetoelectric Cr2O3, and thus continuously tune the exchange bias of an adjacent CoPd film. Voltage-controlled exchange bias training is initialized by tuning the antiferromagnetic interface into a nonequilibrium state incommensurate with the underlying bulk. Interpretation of these hitherto unreported effects contributes to new understanding in electrically controlled magnetism.

  9. Evanescent field interaction of tapered fiber with graphene oxide in generation of wide-bandwidth mode-locked pulses

    Science.gov (United States)

    Ahmad, H.; Faruki, M. J.; Razak, M. Z. A.; Tiu, Z. C.; Ismail, M. F.

    2017-02-01

    Pulses with picosecond pulse widths are highly desired for high precision laser applications. A mode-locked pulse laser utilizing evanescent field interaction of a tapered fiber with graphene oxide (GO) is demonstrated. A homemade fabrication stage was used to fabricate the tapered fiber using systematic flame brushing and a GO solution was used to coat the microfiber using optical deposition technique. Pulse trains with a pulse width of 3.46 ps, a 3 dB optical bandwidth of 11.82 nm and a repetition rate of 920 kHz were obtained. The system has substantial potential for many crucial medical, communication, bio processing, military, and industrial applications.

  10. Decoding of retinal ganglion cell spike trains evoked by temporally patterned electrical stimulation.

    Science.gov (United States)

    Ryu, Sang Baek; Ye, Jang Hee; Goo, Yong Sook; Kim, Chi Hyun; Kim, Kyung Hwan

    2010-08-12

    For successful restoration of vision by retinal prostheses, the neural activity of retinal ganglion cells (RGCs) evoked by electrical stimulation should represent the information of spatiotemporal patterns of visual input. We propose a method to evaluate the effectiveness of stimulation pulse trains so that the crucial temporal information of a visual input is accurately represented in the RGC responses as the amplitudes of pulse trains are modulated according to the light intensity. This was enabled by spike train decoding. The effectiveness of the stimulation was evaluated by the accuracy of decoding pulse amplitude from the RGC spike train, i.e., by the similarity between the original and the decoded pulse amplitude time series. When the parameters of stimulation were suitably determined, the RGC responses were reliably modulated by varying the amplitude of electrical pulses. Accordingly, the temporal pattern of pulse amplitudes could be successfully decoded from multiunit RGC spike trains. The range of pulse amplitude and the pulse rate were critical for accurate representation of input information in RGC responses. These results suggest that pulse amplitude modulation is a feasible means to encode temporal visual information by RGC spike trains and thus to implement stimulus encoding strategies for retinal prostheses.

  11. Coiled transmission line pulse generators

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, Kenneth Fox (Columbia, MO)

    2010-11-09

    Methods and apparatus are provided for fabricating and constructing solid dielectric "Coiled Transmission Line" pulse generators in radial or axial coiled geometries. The pour and cure fabrication process enables a wide variety of geometries and form factors. The volume between the conductors is filled with liquid blends of monomers, polymers, oligomers, and/or cross-linkers and dielectric powders; and then cured to form high field strength and high dielectric constant solid dielectric transmission lines that intrinsically produce ideal rectangular high voltage pulses when charged and switched into matched impedance loads. Voltage levels may be increased by Marx and/or Blumlein principles incorporating spark gap or, preferentially, solid state switches (such as optically triggered thyristors) which produce reliable, high repetition rate operation. Moreover, these Marxed pulse generators can be DC charged and do not require additional pulse forming circuitry, pulse forming lines, transformers, or an a high voltage spark gap output switch. The apparatus accommodates a wide range of voltages, impedances, pulse durations, pulse repetition rates, and duty cycles. The resulting mobile or flight platform friendly cylindrical geometric configuration is much more compact, light-weight, and robust than conventional linear geometries, or pulse generators constructed from conventional components. Installing additional circuitry may accommodate optional pulse shape improvements. The Coiled Transmission Lines can also be connected in parallel to decrease the impedance, or in series to increase the pulse length.

  12. Green Light Pulse Oximeter

    Energy Technology Data Exchange (ETDEWEB)

    Scharf, John Edward (Oldsmar, FL)

    1998-11-03

    A reflectance pulse oximeter that determines oxygen saturation of hemoglobin using two sources of electromagnetic radiation in the green optical region, which provides the maximum reflectance pulsation spectrum. The use of green light allows placement of an oximetry probe at central body sites (e.g., wrist, thigh, abdomen, forehead, scalp, and back). Preferably, the two green light sources alternately emit light at 560 nm and 577 nm, respectively, which gives the biggest difference in hemoglobin extinction coefficients between deoxyhemoglobin, RHb, and oxyhemoglobin, HbO.sub.2.

  13. Pulsed differential pumping system

    Energy Technology Data Exchange (ETDEWEB)

    Antipov, G.N.; Bagautdinov, F.A.; Rybalov, S.V.

    1985-06-01

    A pulsed differential pumping system is described for extracting an electron beam from a shaping region at a pressure of 10/sup -5/ torr into a volume with a pressure of 10-100 torr. A fast valve is used with appropriate geometrical parameters to reduce the length of the outlet channel considerable while increasing its diameter. Test results are given. The pumping system has two sections which communicate one with the other and with the volume at the elevated pressure which is produced by gasdynamic nozzles.

  14. Pulse Field Gel Electrophoresis.

    Science.gov (United States)

    Sharma-Kuinkel, Batu K; Rude, Thomas H; Fowler, Vance G

    2016-01-01

    Pulse Field Gel Electrophoresis (PFGE) is a powerful genotyping technique used for the separation of large DNA molecules (entire genomic DNA) after digesting it with unique restriction enzymes and applying to a gel matrix under the electric field that periodically changes direction. PFGE is a variation of agarose gel electrophoresis that permits analysis of bacterial DNA fragments over an order of magnitude larger than that with conventional restriction enzyme analysis. It provides a good representation of the entire bacterial chromosome in a single gel with a highly reproducible restriction profile, providing clearly distinct and well-resolved DNA fragments.

  15. A Pulsed Sphere Tutorial

    Energy Technology Data Exchange (ETDEWEB)

    Cullen, Dermott E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-01-30

    Here I attempt to explain what physically happens when we pulse an object with neutrons, specifically what we expect the time dependent behavior of the neutron population to look like. Emphasis is on the time dependent emission of both prompt and delayed neutrons. I also describe how the TART Monte Carlo transport code models this situation; see the appendix for a complete description of the model used by TART. I will also show that, as we expect, MCNP and MERCURY, produce similar results using the same delayed neutron model (again, see the appendix).

  16. ENGLISH TRAINING

    CERN Multimedia

    2003-01-01

    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 PLACES AVAILABLE Writing Professional Documents in English This course is designed for people with a good level of spoken English who need to improve their professional writing (administrative, scientific, technical). Duration: 20 hours (2 hours a week) Price: 440 CHF (for 8 students) Date and timetable will be fixed when there are sufficient participants enrolled. Oral Expression This course is intended for people with a good knowledge of English who want to practise and maintain their sp...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-08-15

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

  18. Generation of parallel transmission sub-pulses of spatial distribution based on polarizing splitting prism

    Science.gov (United States)

    Yang, Haifeng; Yang, Xiaoping; Sun, Xuna; Liu, Jun; Yang, Yong

    2016-09-01

    Parallel processing is the forefront of femtosecond laser micro-nano processing. The key to parallel processing is obtaining multichannel parallel femtosecond laser beams. A method of spatial parallel pulse splitting based on birefringence properties of polarizing splitting prism is proposed for obtaining multichannel parallel ultra-short pulse trains. The generated sub-pulses have the characteristics of equal energy and high similarity. More than that, the compact structure of the polarizing splitting prism makes it easier to be implemented. The accurate relationship between the space interval of pulse sequences and the structural angle, dimension and the distance between the two prisms is mathematically derived. The realizable array form of sub-pulse sequences is theoretically analyzed. The feasibility of the proposed method of femtosecond laser parallel processing is analyzed by software simulation and numerical calculation. The results will provide a new research direction for application of ultrashort pulse in parallel processing.

  19. Coherent amplification of attosecond light pulses in the water-window spectral region.

    Science.gov (United States)

    Serrat, C; Roca, D; Seres, J

    2015-02-23

    We present a theoretical study on coherent extreme ultraviolet (XUV) attosecond pulse amplification mediated by nonlinear parametric enhanced forward scattering occurring in the interaction of a strong femtosecond infrared (IR) laser pulse combined with a weak attosecond XUV pulse train with an atom. We predict large amplification of XUV radiation when the IR strong pulse and the XUV weak pulse are optimally phased. We study high-order harmonic processes (HHG) in He, He(+) and Ne(++), and show how although the HHG yield is largely affected by the particular atom used as target, nonlinear parametric XUV amplification is only weakly affected. We conclude that XUV nonlinear parametric attosecond pulse amplification can be most efficiently observed by using atoms with a high ionization potential and that the nonlinear amplification is robust at high photon energies where HHG is not efficient, such as in the water-window spectral region.

  20. Structure of picosecond pulses of a Q-switched and mode-locked diode-pumped Nd:YAG laser

    Energy Technology Data Exchange (ETDEWEB)

    Donin, V I; Yakovin, D V; Gribanov, A V [Institute of Automation and Electrometry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2015-12-31

    The pulse duration of a diode-pumped Nd:YAG laser, in which Q-switching with mode-locking (QML regime) is achieved using a spherical mirror and a travelling-wave acousto-optic modulator, is directly measured with a streak camera. It is found that the picosecond pulses can have a non-single-pulse structure, which is explained by excitation of several competing transverse modes in the Q-switching regime with a pulse repetition rate of 1 kHz. In the case of cw mode-locking (without Q-switching), a new (auto-QML) regime is observed, in which the pulse train repetition rate is determined by the frequency of the relaxation oscillations of the laser field while the train contains single picosecond pulses. (control of laser radiation parameters)

  1. COMPUTER BASED HEART PULSES MEASUREMENT

    Directory of Open Access Journals (Sweden)

    Ali N. Hamoodi

    2013-05-01

    Full Text Available In this work the measurement and displays of blood oxygen saturation and pulse rate are investigated practically using computer.The analysis involves the variation in blood oxygen saturation ratio and pulse rate. The results obtained are compared with kontron pulse oximeter 7840 device. The value obtained for the same person pulse rate is approximately equal to that obtained by the konton pulse oximeter 7840 device. The sensor used in this work is the finger clip.The advantages of using computer over kontron pulse oximeter 7840 device is that the data of the patient can be saved in the computer for many years and also it can be display at any time so that the doctor get file contains all data for each patient. 

  2. Angular momentum of sound pulses.

    Science.gov (United States)

    Lekner, John

    2006-07-05

    Three-dimensionally localized acoustic pulses in an isotropic fluid medium necessarily have transverse components of momentum density. Those with an azimuthal component of momentum density can carry angular momentum. The component of total pulse angular momentum along the direction of the total momentum is an invariant (constant in time and independent of choice of origin). The pulse energy, momentum and angular momentum are evaluated analytically for a family of localized solutions of the wave equation. In the limit where the pulses have many oscillations within their spatial extent ([Formula: see text], where k is the wavenumber and a determines the size of a pulse), the energy, momentum and angular momentum are consistent with a multiphonon representation of the pulse, each phonon having energy [Formula: see text], momentum [Formula: see text] and angular momentum [Formula: see text] (with integer m).

  3. Generation of finite wave trains in excitable media

    Science.gov (United States)

    Yochelis, A.; Knobloch, E.; Xie, Y.; Qu, Z.; Garfinkel, A.

    2011-01-01

    Spatiotemporal control of excitable media is of paramount importance in the development of new applications, ranging from biology to physics. To this end, we identify and describe a qualitative property of excitable media that enables us to generate a sequence of traveling pulses of any desired length, using a one-time initial stimulus. The wave trains are produced by a transient pacemaker generated by a one-time suitably tailored spatially localized finite amplitude stimulus, and belong to a family of fast pulse trains. A second family, of slow pulse trains, is also present. The latter are created through a clumping instability of a traveling wave state (in an excitable regime) and are inaccessible to single localized stimuli of the type we use. The results indicate that the presence of a large multiplicity of stable, accessible, multi-pulse states is a general property of simple models of excitable media. PMID:21572974

  4. Bipolar pulse forming line

    Science.gov (United States)

    Rhodes, Mark A.

    2008-10-21

    A bipolar pulse forming transmission line module for linear induction accelerators having first, second, third, fourth, and fifth planar conductors which form an interleaved stack with dielectric layers between the conductors. Each conductor has a first end, and a second end adjacent an acceleration axis. The first and second planar conductors are connected to each other at the second ends, the fourth and fifth planar conductors are connected to each other at the second ends, and the first and fifth planar conductors are connected to each other at the first ends via a shorting plate adjacent the first ends. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short a high voltage from the first end of the third planar conductor to the first end of the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.

  5. Heat driven pulse pump

    Science.gov (United States)

    Benner, Steve M (Inventor); Martins, Mario S. (Inventor)

    2000-01-01

    A heat driven pulse pump includes a chamber having an inlet port, an outlet port, two check valves, a wick, and a heater. The chamber may include a plurality of grooves inside wall of the chamber. When heated within the chamber, a liquid to be pumped vaporizes and creates pressure head that expels the liquid through the outlet port. As liquid separating means, the wick, disposed within the chamber, is to allow, when saturated with the liquid, the passage of only liquid being forced by the pressure head in the chamber, preventing the vapor from exiting from the chamber through the outlet port. A plurality of grooves along the inside surface wall of the chamber can sustain the liquid, which is amount enough to produce vapor for the pressure head in the chamber. With only two simple moving parts, two check valves, the heat driven pulse pump can effectively function over the long lifetimes without maintenance or replacement. For continuous flow of the liquid to be pumped a plurality of pumps may be connected in parallel.

  6. Assembly delay line pulse generators

    CERN Document Server

    1971-01-01

    Assembly of six of the ten delay line pulse generators that will power the ten kicker magnet modules. One modulator part contains two pulse generators. Capacitors, inductances, and voltage dividers are in the oil tank on the left. Triggered high-pressure spark gap switches are on the platforms on the right. High voltage pulse cables to the kicker magnet emerge under the spark gaps. In the centre background are the assembled master gaps.

  7. Multi pulse control of entanglement

    CERN Document Server

    Uchiyama, C; Uchiyama, Chikako; Aihara, Masaki

    2004-01-01

    We study the effectiveness of multi pulse control to suppress the degradation of entanglement. Based on a linearly interacting spin-boson model, we show that the multi pulse application recovers the decay of concurrence when an entangled pair of spins interacts with a reservoir that has the non-Markovian nature. We present the effectiveness of multi pulse control for both the common bath case and the individual bath case.

  8. LANGUAGE TRAINING

    CERN Multimedia

    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 FRENCH TRAINING General and Professional French Courses The next session will take place from 26 January to 02 April 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 January to 02 April 2004. This course is designed for people wi...

  9. LANGUAGE TRAINING

    CERN Multimedia

    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 FRENCH TRAINING General and Professional French Courses The next session will take place from 26 January to 02 April 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 January to 02 April 2004. This course is designed for peop...

  10. Training Attestations

    CERN Multimedia

    HR Department

    2004-01-01

    In the past, paper Training Attestations were printed during the first quarter of a New Year for Staff Members having followed courses and seminars the previous year in the context of CERN's official Training Programmes.  The attestations were sent to Divisional Training Officers (DTO's) for distribution to all Staff Members concerned within their Division. In practise many Staff Members did not find this paper useful, however some expressed a wish to be able to have access to a self-service facility in case of need. This change was discussed by the Joint Training Board (JTB) and with the DTO's during 2003 and was supported. As a consequence, following a collaboration between HR-PMD and IT-AIS, from 2004 onwards paper Training Attestations will no longer be printed and distributed as before. Those requiring a list of training followed in the past can now obtain their attestation directly from the Human Resources Toolkit (HRT) application for all training followed since 1997. https://hrt.cern...

  11. Analysis of Pulse Modulated Control Systems (Ⅲ) Stability of Systems with Pulse Frequency Modulation and Systems with Combined Pulse Frequency and Pulse Width Modulation

    OpenAIRE

    OI,Shigemitsu

    1993-01-01

    Sufficient conditions for finite pulse stability of interconnected systems with combined pulse frequency and pulse width modulation are developed in this paper using a direct method. The stability criteria established provide upper bounds on the number of pulses emitted by each modulator. The results are also applicable to those systems which contain a finite number of pulse frequency modulators and a finite number of combined pulse frequency and pulse width modulators

  12. Population inversion by chirped pulses

    Energy Technology Data Exchange (ETDEWEB)

    Lu Tianshi [Department of Mathematics and Statistics, Wichita State University, Wichita, Kansas 67260-0033 (United States)

    2011-09-15

    In this paper, we analyze the condition for complete population inversion by a chirped pulse over a finite duration. The nonadiabatic transition probability is mapped in the two-dimensional parameter space of coupling strength and detuning amplitude. Asymptotic forms of the probability are derived by the interference of nonadiabatic transitions for sinusoidal and triangular pulses. The qualitative difference between the maps for the two types of pulses is accounted for. The map is used for the design of stable inversion pulses under specific accuracy thresholds.

  13. Double pulse laser wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Changbum [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)], E-mail: chbkim@postech.ac.kr; Kim, Jin-Cheol B. [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Kim, Kukhee [National Fusion Reserch Center, Daejeon 305-333 (Korea, Republic of); Ko, In Soo [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Suk, Hyyong [Center for Advanced Accelerators, Korea Electrotechnology Research Institute, Changwon 641-120 (Korea, Republic of)

    2007-10-22

    Two-dimensional simulation studies are performed for modified laser wakefield acceleration. After one laser pulse, another identical laser pulse is sent to the plasma to amplify the wake wave resonantly. The simulation results show that the number of injected electrons is bigger than that of the single pulse case and the beam energy is higher as well. In addition, increase of the transverse amplitude is noticed in the wake wave after the second laser pulse. This shows that the transverse motion of the wake wave enhances the wave breaking for strong injection and acceleration of electron beams.

  14. Pulse oximetry in severe anaemia

    DEFF Research Database (Denmark)

    Ramsing, T; Rosenberg, J

    1992-01-01

    Measurement of arterial oxygen saturation by pulse oximetry was performed in two patients with acute and chronic anaemia (haemoglobin concentrations: 2.9 mmol/l (4.7 g/dl) and 1.9 mmol/l (3.0 g/dl), respectively) using a Radiometer OXI and a Nellcor N-200 pulse oximeter. The two oximeters read...... alternating different values in the two patients. In conclusion, pulse oximeters are able to give a value for oxygen saturation even at extreme anaemia, and when a high value is given, it possibly reflects arterial oxygen saturation. The value of pulse oximetry in severe anaemia is discussed....

  15. Distinctions of effects of pulsed laser radiation and /sup 60/Co gamma radiation on some microorganisms. [Escherichia coli; Saccharomyces cerevisiae

    Energy Technology Data Exchange (ETDEWEB)

    Petin, V.G.; Rusina, L.K.; Sebrant, Yu.V.; Baranov, V.Yu.; Malyuta, D.D.; Niz' ev, V.G.

    1979-03-01

    Studies were made of the sensitivity of yeast cells varying in ploidy and bacterial cells varying in genotype to the effects of pulsed laser radiation and the combined effect of laser and ionizing radiation. It was demonstrated that there is no additivity of irradiation with a train of pulses, as compared to a single pulse. The impairment of cellular reproductive capacity under the influence of lasers was irreversible.

  16. Effect of interval training programme on pulse pressure in the ...

    African Journals Online (AJOL)

    The exercise (work: rest ratio of 1:1) groups involved in an 8-weeks interval ... at intensities of 60-79% of HR max (maximum heart rate), while the control group ... Changes in VO2max also negatively correlated with changes in PP (r= -.285) at ...

  17. Theoretical Studies of the Output Pulse with Variation of the Pumping Pulse for RF Excited CO2 Pulsed Waveguide Laser

    Institute of Scientific and Technical Information of China (English)

    A Rauf; ZHOU Wei; XIN Jian-guo

    2006-01-01

    The behavior of a RF-excited waveguide CO2 laser in the pulse regime is studied theoretically. The output pulse evolution is studied by applying three types of pulses namely the square, sine and the triangular ones as the excitation pulses. The frequency dependence behavior of the output pulse is also presented.

  18. Ultrahigh speed photography of picosecond light pulses and echoes.

    Science.gov (United States)

    Duguay, M A; Mattick, A T

    1971-09-01

    Three new results have been obtained with a recently developed camera of 10-psec framing time: (1) The effect of the finite speed of light in photographing relativistic objects is experimentally demonstrated, by photographing a dumbbell-like entity formed by two packets of light. In contrast to material objects, which, theory predicts, should appear rotated, the light dumbbell appears sheared. (2) Photographs of the mode-locked Nd: glass laser radiation show numerous subsidiary pulses accompanying the main ultrashort pulses in the train. The latter have durations ranging from 7 psec to 15 psec. (3) The technique of gated picture ranging, previously used with nanosecond pulses, is extended to the picosecond range where a resolution of 1 cm is demonstrated. Some potentially useful applications are proposed.

  19. Doppler Ambiguity Resolution Based on Random Sparse Probing Pulses

    Directory of Open Access Journals (Sweden)

    Yunjian Zhang

    2015-01-01

    Full Text Available A novel method for solving Doppler ambiguous problem based on compressed sensing (CS theory is proposed in this paper. A pulse train with the random and sparse transmitting time is transmitted. The received signals after matched filtering can be viewed as randomly sparse sampling from the traditional fixed-pulse repetition frequency (PRF echo signals. The whole target echo could be reconstructed via CS recovery algorithms. Through refining the sensing matrix, which is equivalent to increase the sampling frequency of target characteristic, the Doppler unambiguous range is enlarged. In particular, Complex Approximate Message Passing (CAMP algorithm is developed to estimate the unambiguity Doppler frequency. Cramer-Rao lower bound expressions are derived for the frequency. Numerical simulations validate the effectiveness of the proposed method. Finally, compared with traditional methods, the proposed method only requires transmitting a few sparse probing pulses to achieve a larger Doppler frequency unambiguous range and can also reduce the consumption of the radar time resources.

  20. Complex pulsing schemes for high frame rate imaging

    DEFF Research Database (Denmark)

    Misaridis, Thanassis; Fink, Mathias; Jensen, Jørgen Arendt

    2002-01-01

    High frame rate ultrasound imaging can be achieved by simultaneous transmission of multiple focused beams along different directions. However, image quality degrades by the interference among beams. An alternative approach is to transmit spherical waves of a basic short pulse with frequency coding...... with linear frequency modulation along the transducer elements, that cover the 70% fractional bandwidth of the 7 MHz transducer. The resulted images (after beamforming and matched filtering) show an axial resolution at the same order as in conventional pulse excitation and axial sidelobes down to -45 d......B. With the proposed imaging strategy of pulse train excitation, a whole image can be formed with only two emissions, making it possible to obtain high quality images at a frame rate of 20 to 25 times higher than that of conventional phased array imaging...

  1. Ultrafast temporal pulse shaping via phase-sensitive three-wave mixing.

    Science.gov (United States)

    Yin, Y C; French, D; Jovanovic, I

    2010-08-16

    It is well-known that the process of optical parametric amplification (OPA) can be sensitive to the phases of the incident waves. In OPA realized by three-wave mixing, injection of all three waves into the same mode with appropriate phase relationship results in amplification of the signal phase, with an associated deamplification of the signal energy. Prospects for the use of this technique in the temporal domain for shaping ultrashort laser pulses are analyzed using a numerical model. Several representative pulse shaping capabilities of this technique are identified, which can significantly augment the performance of common passive pulse shaping methods operating in the Fourier domain. It is found that the use of phase-sensitive OPA shows a potential for significant compression of approximately 100 fs pulses, steepening of the rise time of ultrashort pulses, and production of pulse doublets and pulse trains. It is also shown that the group velocity mismatch can assist the shaping process. Such pulse shaping capabilities are found to be within reach of this technique in common nonlinear optical crystals pumped by pulses available from compact femtosecond chirped-pulse amplification laser systems.

  2. Development of a neural network screening aid for diagnosing lower limb peripheral vascular disease from photoelectric plethysmography pulse waveforms.

    Science.gov (United States)

    Allen, J; Murray, A

    1993-02-01

    An artificial neural network (ANN) was trained to classify photoelectric plethysmographic (PPG) pulse waveforms for the diagnosis of lower limb peripheral vascular disease (PVD). PPG pulses from the lower limbs, and pre- and post-exercise Doppler ultrasound ankle to brachial systolic blood pressure ratio measurements were obtained from patients referred to a vascular investigation laboratory. A single PPG pulse from the big toe of each leg was processed and normalized, and used as input data to the ANN. The ANN outputs represented the diagnostic classifications (normal, significant PVD and major PVD) and the ANN was trained with the ankle to brachial pressure indices (ABPI). The ANN structure consisted of an input layer (50 neuron units from the PPG pulse input), a single hidden layer (15 neurons) and an output layer (3 neurons for the PVD diagnoses). The back-propagation learning algorithm was used to train the ANN for 500 epochs with a PPG training set of pulses from 100 legs. Test data for network assessment comprised pulses from a further 50 legs (20 normal and 30 PVD, of which 15 were categorized as having major disease). A network sensitivity of 93% and specificity of 85% was achieved with respect to the Doppler ABPI standard, giving a diagnostic accuracy of 90%. The results of this study indicate that a neural network can be trained to distinguish between PPG pulses from normal and diseased lower limb arteries. The simplicity of PPG measurement and neural network classification holds promise for the screening of lower limb arterial PVD.

  3. Carrier-envelope Phase Drift Detection of Picosecond Pulses

    Directory of Open Access Journals (Sweden)

    Cormier E.

    2013-03-01

    Full Text Available A bandwidth-independent, linear and scalable method for carrier-envelope phase drift measurement demonstrated. Our experiments reveal that carrier-envelope phase drift of a picosecond pulse train can be directly obtained from the spectrally resolved interference pattern of a length-stabilized multiple-beam interferometer. The retrieved phase from the pattern correlates well with the strongly CEP-sensitive coupling signal between the frequency combs of the picosecond oscillator and an ultra-high finesse Fabry-Perot interferometer. Our results can lead to the generation of a robust CEP-stabilized seed pulse train for high resolution comb spectroscopy as well as to compact Compton X-ray and gamma-ray sources

  4. Low-intensity resistance training after high-intensity resistance training can prevent the increase of central arterial stiffness.

    Science.gov (United States)

    Okamoto, T; Masuhara, M; Ikuta, K

    2013-05-01

    Although high-intensity resistance training increases arterial stiffness, low-intensity resistance training reduces arterial stiffness. The present study investigates the effect of low-intensity resistance training before and after high-intensity resistance training on arterial stiffness. 30 young healthy subjects were randomly assigned to a group that performed low-intensity resistance training before high-intensity resistance training (BLRT, n=10), a group that performed low-intensity resistance training after high-intensity resistance training (ALRT, n=10) and a sedentary control group (n=10). The BLRT and ALRT groups performed resistance training at 80% and 50% of one repetition maximum twice each week for 10 wk. Arterial stiffness was measured using carotid-femoral and femoral-ankle pulse wave velocity (PWV). One-repetition maximum strength in the both ALRT and BLRT significantly increased after the intervention (Ptraining in the ALRT group did not change from before training. In contrast, carotid-femoral PWV after combined training in the BLRT group increased from before training (P training in the both BLRT and ALRT groups did not change from before training. These results suggest that although arterial stiffness is increased by low-intensity resistance training before high-intensity resistance training, performing low-intensity resistance training thereafter can prevent the increase of arterial stiffness. © Georg Thieme Verlag KG Stuttgart · New York.

  5. Supervisor training

    DEFF Research Database (Denmark)

    Pedersen, Inge Nygaard

    2015-01-01

    This article fills a gap in knowledge about supervisor training programmes in the field of music therapy in Europe. Sparse research exists which demonstrates evidence of effective professional supervision upon the outcome of music therapy clinical practice. The article has its focus on the experi......This article fills a gap in knowledge about supervisor training programmes in the field of music therapy in Europe. Sparse research exists which demonstrates evidence of effective professional supervision upon the outcome of music therapy clinical practice. The article has its focus...... on the experience of an integrated supervisor training programme offered in Aalborg, Denmark in 2009/2010. In this programme general issues of professional supervision and the application of artistic media as a core element in the supervisory process were Integrated. It is the hope of the author that this article...... will inspire other music therapists to develop supervisor training programmes for professional music therapists and also to undertake further research into professional supervision....

  6. Officer Training

    Data.gov (United States)

    Allegheny County / City of Pittsburgh / Western PA Regional Data Center — This dataset shows the time spent by currently active Pittsburgh Police Officers in professional development training. Officers who are no longer employed in the...

  7. Strength Training

    Science.gov (United States)

    ... en español Entrenamiento de la fuerza muscular Strength training is a vital part of a balanced exercise routine that includes aerobic activity and flexibility exercises. Regular aerobic exercise, such as running or ...

  8. 1030-nm diode-laser-based light source delivering pulses with nanojoule energies and picosecond duration adjustable by mode locking or pulse gating operation

    Science.gov (United States)

    Klehr, A.; Liero, A.; Wenzel, H.; Bugge, F.; Brox, O.; Fricke, J.; Ressel, P.; Knigge, A.; Heinrich, W.; Tränkle, G.

    2017-02-01

    A new compact 1030 nm picosecond light source which can be switched between pulse gating and mode locking operation is presented. It consists of a multi-section distributed Bragg reflector (DBR) laser, an ultrafast multisection optical gate and a flared power amplifier (PA), mounted together with high frequency electronics and optical elements on a 5×4 cm micro bench. The master oscillator (MO) is a 10 mm long ridge wave-guide (RW) laser consisting of 200 μm long saturable absorber, 1500 μm long gain, 8000 μm long cavity, 200 μm long DBR and 100 μm long monitor sections. The 2 mm long optical gate consisting of several RW sections is monolithically integrated with the 4 mm long gain-guided tapered amplifier on a single chip. The light source can be switched between pulse gating and passive mode locking operation. For pulse gating all sections of the MO (except of the DBR and monitor sections) are forward biased and driven by a constant current. By injecting electrical pulses into one section of the optical gate the CW beam emitted by the MO is converted into a train of optical pulses with adjustable widths between 250 ps and 1000 ps. Peak powers of 20 W and spectral linewidths in the MHz range are achieved. Shorter pulses with widths between 4 ps and 15 ps and peak powers up to 50 W but larger spectral widths of about 300 pm are generated by mode locking where the saturable absorber section of the MO is reversed biased. The repetition rate of 4.2 GHz of the pulse train emitted by the MO can be reduced to values between 1 kHz and 100 MHz by utilizing the optical gate as pulse picker. The pulse-to-pulse distance can be controlled by an external trigger source.

  9. Determination of pulse profile characteristics of multi spot retinal photocoagulation lasers.

    Science.gov (United States)

    Clarkson, Douglas McG; Makhzoum, Osama; Blackburn, John

    2015-10-01

    A system is described for determination of discrete pulse train characteristics of multi spot laser delivery systems for retinal photocoagulation. While photodiodes provide an ideal detection mechanism, measurement artifacts can potentially be introduced by the spatial pattern of the delivered beam relative to a discrete photodiode element. This problem was overcome by use of an integrating sphere to produce a uniform light field at the site of the photodiode detector. A basic current driven photodiode detection circuit incorporating an operational amplifier was used to generate a signal captured by a commercially available USB interface device at a rate of 10 kHz. Studies were undertaken of a Topcon Pascal Streamline laser system with output at a wavelength of 577 nm (yellow). This laser features the proprietary feature of 'Endpoint Management' ™ where pulses can be delivered as 100% of set energy levels with visible reaction on the retina and also at a reduced energy level to create potentially non visible but clinically effective lesions. Using the pulse train measurement device it was identified that the 'Endpoint Management' ™ delivery mode of pulses of lower energy was achieved by reducing the pulse duration of pulses for non-visible effect pulses while maintaining consistent beam power levels within the delivered pulse profile. The effect of eye geometry in determining safety and effectiveness of multi spot laser delivery for retinal photocoagulation is discussed. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

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

    Energy Technology Data Exchange (ETDEWEB)

    Schimpf, Damian Nikolaus

    2010-02-09

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

  11. Pulsed plasma arc cladding

    Institute of Scientific and Technical Information of China (English)

    龙; 白钢; 李振民; 张赋升; 杨思乾

    2004-01-01

    A prototype of Pulsed Plasma Arc Cladding system was developed, in which single power source supplies both transferred plasma arc (TPA) and non-transferred plasma arc (N-TPA). Both plasmas work in turn in a high frequency controlled by an IGBT connecting nozzle and workpiece. The working frequency of IGBT ranges from 50 ~ 7000Hz, in which the plasmas can work in turn smoothly. Higher than 500 Hz of working frequency is suggested for promotion of cladding quality and protection of IGBT. Drag phenomenon of TPA intensifies as the frequency goes up, which tends to increase the current proportion of TPA and suppress N-TPA. The occupation ratio of IGBT can be regulated from 5% ~ 95%, which balances the power supplies of both plasmas. An occupation ratio higher than 50% gives adequate proportion of arc current for N-TPA to preheat powder.

  12. Nanofabrication with Pulsed Lasers

    Directory of Open Access Journals (Sweden)

    Kabashin AV

    2010-01-01

    Full Text Available Abstract An overview of pulsed laser-assisted methods for nanofabrication, which are currently developed in our Institute (LP3, is presented. The methods compass a variety of possibilities for material nanostructuring offered by laser–matter interactions and imply either the nanostructuring of the laser-illuminated surface itself, as in cases of direct laser ablation or laser plasma-assisted treatment of semiconductors to form light-absorbing and light-emitting nano-architectures, as well as periodic nanoarrays, or laser-assisted production of nanoclusters and their controlled growth in gaseous or liquid medium to form nanostructured films or colloidal nanoparticles. Nanomaterials synthesized by laser-assisted methods have a variety of unique properties, not reproducible by any other route, and are of importance for photovoltaics, optoelectronics, biological sensing, imaging and therapeutics.

  13. Nanosecond Pulse Technique

    Science.gov (United States)

    1989-03-17

    tunnel diodes, to ferrites, etc.) and to the need for the review of the methods of formation and converting the pulses, to a considerable degree...4n3l) 0 1 + 4n 21)2 + (4n2l) (.84) _ 4 nf tl 5 (I - 4n12/) 2 - (4nil)’ (1.85) " ( - 2o) l - 4’n2% 2 I3 (I + 4n =2/)2 + ( 41a2 )’ -arg + 4ni,21. + j4na,tJ...recirculator is borrowed from the article of Yu. I. Neymark, Yu. K. Maklakov and L. P. Yelkins [105]. ENDFOOTNOTE. DOC = 88076720 PAGE d a) t l I t S6) t�t

  14. Nanofabrication with pulsed lasers.

    Science.gov (United States)

    Kabashin, Av; Delaporte, Ph; Pereira, A; Grojo, D; Torres, R; Sarnet, Th; Sentis, M

    2010-02-24

    An overview of pulsed laser-assisted methods for nanofabrication, which are currently developed in our Institute (LP3), is presented. The methods compass a variety of possibilities for material nanostructuring offered by laser-matter interactions and imply either the nanostructuring of the laser-illuminated surface itself, as in cases of direct laser ablation or laser plasma-assisted treatment of semiconductors to form light-absorbing and light-emitting nano-architectures, as well as periodic nanoarrays, or laser-assisted production of nanoclusters and their controlled growth in gaseous or liquid medium to form nanostructured films or colloidal nanoparticles. Nanomaterials synthesized by laser-assisted methods have a variety of unique properties, not reproducible by any other route, and are of importance for photovoltaics, optoelectronics, biological sensing, imaging and therapeutics.

  15. Pulsed plasma electron sourcesa)

    Science.gov (United States)

    Krasik, Ya. E.; Yarmolich, D.; Gleizer, J. Z.; Vekselman, V.; Hadas, Y.; Gurovich, V. Tz.; Felsteiner, J.

    2009-05-01

    There is a continuous interest in research of electron sources which can be used for generation of uniform electron beams produced at E ≤105 V/cm and duration ≤10-5 s. In this review, several types of plasma electron sources will be considered, namely, passive (metal ceramic, velvet and carbon fiber with and without CsI coating, and multicapillary and multislot cathodes) and active (ferroelectric and hollow anodes) plasma sources. The operation of passive sources is governed by the formation of flashover plasma whose parameters depend on the amplitude and rise time of the accelerating electric field. In the case of ferroelectric and hollow-anode plasma sources the plasma parameters are controlled by the driving pulse and discharge current, respectively. Using different time- and space-resolved electrical, optical, spectroscopical, Thomson scattering and x-ray diagnostics, the parameters of the plasma and generated electron beam were characterized.

  16. Micro pulse lidar

    Science.gov (United States)

    Spinhirne, James D.

    1993-01-01

    An eye safe, compact, solid state lidar for profiling atmospheric cloud and aerosol scattering has been demonstrated. The transmitter of the micropulse lidar is a diode pumped micro-J pulse energy, high repetition rate Nd:YLF laser. Eye safety is obtained through beam expansion. The receiver employs a photon counting solid state Geiger mode avalanche photodiode detector. Data acquisition is by a single card multichannel scaler. Daytime background induced quantum noise is controlled by a narrow receiver field-of-view and a narrow bandwidth temperature controlled interference filter. Dynamic range of the signal is limited by optical geometric signal compression. Signal simulations and initial atmospheric measurements indicate that systems built on the micropulse lidar concept are capable of detecting and profiling all significant cloud and aerosol scattering through the troposphere and into the stratosphere. The intended applications are scientific studies and environmental monitoring which require full time, unattended measurements of the cloud and aerosol height structure.

  17. Capacitor discharge pulse analysis.

    Energy Technology Data Exchange (ETDEWEB)

    Baker, Michael Sean; Griffiths, Stewart K.; Tanner, Danelle Mary

    2013-08-01

    Capacitors used in firing sets and other high discharge current applications are discharge tested to verify performance of the capacitor against the application requirements. Parameters such as capacitance, inductance, rise time, pulse width, peak current and current reversal must be verified to ensure that the capacitor will meet the application needs. This report summarizes an analysis performed on the discharge current data to extract these parameters by fitting a second-order system model to the discharge data and using this fit to determine the resulting performance metrics. Details of the theory and implementation are presented. Using the best-fit second-order system model to extract these metrics results in less sensitivity to noise in the measured data and allows for direct extraction of the total series resistance, inductance, and capacitance.

  18. Template Reproduction of GRB Pulse Light Curves

    Science.gov (United States)

    Hakkila, Jon E.; Preece, R. D.; Loredo, T. J.; Wolpert, R. L.; Broadbent, M. E.

    2014-01-01

    A study of well-isolated pulses in gamma ray burst light curves indicates that simple models having smooth and monotonic pulse rises and decays are inadequate. Departures from the Norris et al. (2005) pulse shape are in the form of a wave-like pre-peak residual that is mirrored and stretched following the peak. Pulse shape departures are present in GRB pulses of all durations, but placement of the departures relative to pulse peaks correlates with asymmetry. This establishes an additional link between temporal structure and spectral evolution, as pulse asymmetry is related to initial hardness while pulse duration indicates the rate of hard-to-soft pulse evolution.

  19. Research agenda shrimp pulse fishery

    NARCIS (Netherlands)

    Marlen, van B.; Rasenberg, M.M.M.; Verschueren, B.; Polet, H.

    2015-01-01

    In the recent decennia, many developments have taken place to improve the selectivity of the shrimp fishing gears. Recently, the development of a pulse gear for catching shrimps has taken up again as an opportunity to decrease discards, inspired by developments in the flatfish pulse fishery.

  20. Pulse oximetry for perioperative monitoring

    DEFF Research Database (Denmark)

    Pedersen, Tom; Møller, Ann Merete; Hovhannisyan, Karen

    2009-01-01

    Pulse oximetry is extensively used in the perioperative period and might improve patient outcomes by enabling an early diagnosis and, consequently, correction of perioperative events that might cause postoperative complications or even death. Only a few randomized clinical trials of pulse oximetry...

  1. A Single-Pulse Integrator

    DEFF Research Database (Denmark)

    Miller, Arne

    1974-01-01

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

  2. NMR in pulsed magnetic field

    KAUST Repository

    Abou-Hamad, Edy

    2011-09-01

    Nuclear magnetic resonance (NMR) experiments in pulsed magnetic fields up to 30.4 T focused on 1H and 93Nb nuclei are reported. Here we discuss the advantage and limitation of pulsed field NMR and why this technique is able to become a promising research tool. © 2011 Elsevier Inc. All Rights Reserved.

  3. Dexamethasone pulse therapy in pemphigus

    NARCIS (Netherlands)

    Toth, GG; van de Meer, JB; Jonkman, MF

    2002-01-01

    Pulse therapy with high-dose glucocorticoids was introduced 20 years ago as a treatment modality for autoimmune disease and transplant rejection. The most popular dermatological indication for pulse therapy is severe pemphigus. We reviewed the sequelae of 14 patients with pemphigus who were treated

  4. On the applicability of arbitrarily shaped nanosecond laser pulses for high-quality, high-efficiency micromachining

    Science.gov (United States)

    Eiselen, Sasia; Riedel, Sebastian; Schmidt, Michael

    2014-05-01

    Progressive developments in temporal shaping of short laser pulses offer entirely new approaches at influence and investigate laser-matter-interactions. Commonly used parameters for describing the behavior of short or ultrashort pulses or pulse trains are fluence and intensity. However, fluence does not imply any information about the temporal behavior of energy input during specific pulse duration τ while using the pulse intensity as describing parameter is more meaningful. Nevertheless it still is an averaging over pulse duration and no change in intensity can be determined if the temporal pulse shape changes within a certain combination of pulse duration and pulse energy. Using a flexible programmable MOPA fiber laser experimental studies on the impact of temporal energy distribution within one single laser pulse in micro machining applications were therefore carried out. With this laser source a direct modulation of the temporal pulse shape in the nanosecond regime can easily be controlled. Experiments were carried out with moved as well as with un-moved beam resulting in areas and dimples respectively drilling holes. The presented results clearly show that any averaging over pulse duration results in missing information about time-dependent interactions but can at the same time lead to significant differences in ablation results. Thus, resulting surface roughness Sa can be decreased up to 25 % when changing the pulse shape at constant parameters of fluence and pulse peak power at a pulse duration of 30 ns. It can be observed that the combination of an intensity peak and a lower edge within one pulse can lead to increasing ablation efficiency as well as higher ablation quality compared to the commonly used Gaussian-like temporal pulse shape.

  5. Pulse oximetry for perioperative monitoring

    DEFF Research Database (Denmark)

    Pedersen, Tom; Nicholson, Amanda; Hovhannisyan, Karen

    2014-01-01

    . Results indicated that hypoxaemia was reduced in the pulse oximetry group, both in the operating theatre and in the recovery room. During observation in the recovery room, the incidence of hypoxaemia in the pulse oximetry group was 1.5 to three times less. Postoperative cognitive function was independent...... postoperative complications or even death. Only a few randomized clinical trials of pulse oximetry during anaesthesia and in the recovery room have been performed that describe perioperative hypoxaemic events, postoperative cardiopulmonary complications and cognitive dysfunction. OBJECTIVES: To study the use...... checked the reference lists of trials and review articles. The original search was performed in January 2005, and a previous update was performed in May 2009. SELECTION CRITERIA: We included all controlled trials that randomly assigned participants to pulse oximetry or no pulse oximetry during...

  6. Neurostimulation using subnanosecond electric pulses

    Science.gov (United States)

    Xiao, Shu; Pakhomov, Andrei; Guo, Fei; Polisetty, Swetha; Schoenbach, Karl H.

    2013-02-01

    We have for the first time recorded action potentials in rat hippocampus neurons when they were stimulated by subnanosecond electric pulses. The preliminary results show that applying a series of pulses allowed the accumulation of depolarization before activating the voltage gated channels. The depolarization only occurred when the electric pulses were applied. It is unclear whether the depolarization is caused by the charge accumulation across the membrane or the cation influx due to the membrane permeabilization. We have also conducted an electromagnetic simulation of delivering subnanosecond pulses to tissues using an impulse radiating antenna. The results show that the pulses can be confined in the deep region in the brain but the amplitude is reduced significantly due to the attenuation of the tissues. A partially lossy dielectric lens may be used to reverse the decreasing trend of the electric field.

  7. Pre-earthquake Magnetic Pulses

    CERN Document Server

    Scoville, John; Freund, Friedemann

    2014-01-01

    A semiconductor model of rocks is shown to describe unipolar magnetic pulses, a phenomenon that has been observed prior to earthquakes. These pulses are observable because their extremely long wavelength allows them to pass through the Earth's crust. Interestingly, the source of these pulses may be triangulated to pinpoint locations where stress is building deep within the crust. We couple a semiconductor drift-diffusion model to a magnetic field in order to describe the electromagnetic effects associated with electrical currents flowing within rocks. The resulting system of equations is solved numerically and it is seen that a volume of rock may act as a diode that produces transient currents when it switches bias. These unidirectional currents are expected to produce transient unipolar magnetic pulses similar in form, amplitude, and duration to those observed before earthquakes, and this suggests that the pulses could be the result of geophysical semiconductor processes.

  8. Broadband noise limit in the photodetection of ultralow jitter optical pulses.

    Science.gov (United States)

    Sun, Wenlu; Quinlan, Franklyn; Fortier, Tara M; Deschenes, Jean-Daniel; Fu, Yang; Diddams, Scott A; Campbell, Joe C

    2014-11-14

    Applications with optical atomic clocks and precision timing often require the transfer of optical frequency references to the electrical domain with extremely high fidelity. Here we examine the impact of photocarrier scattering and distributed absorption on the photocurrent noise of high-speed photodiodes when detecting ultralow jitter optical pulses. Despite its small contribution to the total photocurrent, this excess noise can determine the phase noise and timing jitter of microwave signals generated by detecting ultrashort optical pulses. A Monte Carlo simulation of the photodetection process is used to quantitatively estimate the excess noise. Simulated phase noise on the 10 GHz harmonic of a photodetected pulse train shows good agreement with previous experimental data, leading to the conclusion that the lowest phase noise photonically generated microwave signals are limited by photocarrier scattering well above the quantum limit of the optical pulse train.

  9. Pulsed Power for a Dynamic Transmission Electron Microscope

    Energy Technology Data Exchange (ETDEWEB)

    dehope, w j; browning, n; campbell, g; cook, e; king, w; lagrange, t; reed, b; stuart, b; Shuttlesworth, R; Pyke, B

    2009-06-25

    Lawrence Livermore National Laboratory (LLNL) has converted a commercial 200kV transmission electron microscope (TEM) into an ultrafast, nanoscale diagnostic tool for material science studies. The resulting Dynamic Transmission Electron Microscope (DTEM) has provided a unique tool for the study of material phase transitions, reaction front analyses, and other studies in the fields of chemistry, materials science, and biology. The TEM's thermionic electron emission source was replaced with a fast photocathode and a laser beam path was provided for ultraviolet surface illumination. The resulting photoelectron beam gives downstream images of 2 and 20 ns exposure times at 100 and 10 nm spatial resolution. A separate laser, used as a pump pulse, is used to heat, ignite, or shock samples while the photocathode electron pulses, carefully time-synchronized with the pump, function as probe in fast transient studies. The device functions in both imaging and diffraction modes. A laser upgrade is underway to make arbitrary cathode pulse trains of variable pulse width of 10-1000 ns. Along with a fast e-beam deflection scheme, a 'movie mode' capability will be added to this unique diagnostic tool. This talk will review conventional electron microscopy and its limitations, discuss the development and capabilities of DTEM, in particularly addressing the prime and pulsed power considerations in the design and fabrication of the DTEM, and conclude with the presentation of a deflector and solid-state pulser design for Movie-Mode DTEM.

  10. Pulse shaping using a spatial light modulator

    CSIR Research Space (South Africa)

    Botha, N

    2009-07-01

    Full Text Available Femtosecond pulse shaping can be done by different kinds of pulse shapers, such as liquid crystal spatial light modulators (LC SLM), acousto optic modulators (AOM) and deformable and movable mirrors. A few applications where pulse shaping...

  11. Pulse source requirements for OTDM systems

    DEFF Research Database (Denmark)

    Clausen, Anders; Poulsen, Henrik Nørskov; Oxenløwe, Leif Katsuo

    2003-01-01

    A simulation model for investigating the impact of incoherent crosstalk due to pulse tail overlapping is proposed. Requirements to pulse width and pulse tail extinction ratio introducing a maximum of 1 dB penalty is extracted....

  12. Development of reliable 70 T pulsed magnets

    Science.gov (United States)

    Lagutin, A.; Rosseel, K.; Herlach, F.; Vanacken, J.; Bruynseraede, Y.

    2003-12-01

    A capacitor-driven pulsed magnet coil has been designed to generate fields in the 70-75 T range, with a life expectancy of at least 100 pulses, thus qualifying as a '75 T class user magnet'. The bore is 10 mm and the rise time used in our experiments is 4 ms. The coil consists of two coaxial sections: the inner section, where stresses are highest, is made with CuNb microcomposite wire and optimized Zylon reinforcement; the outer section is made with soft copper and glass fibre composite. In the inner section, the stress in each layer is self-contained, while the stresses induced in the outer section are transmitted to a thick shell made from steel and carbon fibre composite. The cross section of the copper wires is adjusted to redistribute the heating evenly between the inner and the outer section. Another innovative design feature is a system for axial compression that can be easily retightened during coil training. Two nearly identical coils were manufactured and tested to 72 T this is a limit imposed due to overheating when using our 10 kV, 0.5 MJ capacitor bank (at an energy of 380 kJ). At 75 T, the calculated von Mises stress in the Zylon composite is 2.6 GPa, well below the UTS of more than 3 GPa, and the CuNb wire is still in an elastic state.

  13. All-fiber high-average power nanosecond-pulsed master-oscillator power amplifier at 2  μm with mJ-level pulse energy.

    Science.gov (United States)

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

    2016-03-10

    We present a high-power nanosecond-pulsed Tm-doped fiber amplifier at 1.971 μm based on a master-oscillator power amplifier (MOPA) configuration. When the repetition rate is 500 kHz and the pulse width is 63.3 ns, the average power reaches 238 W, the peak power reaches 7.06 kW, and the pulse energy is 0.477 mJ. When the pulse train's repetition rate is 300 kHz with a pulse width of 63.7 ns, the average power reaches 197 W, the peak power reaches 9.73 kW, and the pulse energy is 0.66 mJ. When the pulse train's repetition rate is 200 kHz with a pulse width of 58.2 ns, the average power reaches 150 W, the peak power reaches 12.1 kW, and the pulse energy is 0.749 mJ. The spectral linewidths of the pulse trains are 0.15, 0.14, and 0.10 nm for 500 kHz repetition rate, 300 kHz repetition rate, and 200 kHz repetition rate, respectively. To the best of our knowledge, this is the first demonstration of high-power nanosecond-pulsed MOPA at 2 μm with the maximum average power reaching 238 W, the maximum peak power reaching 12.1 kW, and the maximum pulse energy reaching 0.749 mJ.

  14. Comparison of three arterial pulse waveform classification techniques.

    Science.gov (United States)

    Allen, J; Murray, A

    1996-01-01

    Peripheral pulse waveforms can become stretched and damped with increasing severity of peripheral vascular disease (PVD) and hence could provide valuable diagnostic information. This study compares the diagnostic performance of 3 established classification techniques (a linear discriminant classifier, a k-nearest neighbour classifier, and an artificial neural network) for the detection of lower limb arterial disease from pulse waveforms obtained using photoelectric plethysmography (PPG). Pulse waveforms and pre- and post-exercise Doppler ultrasound ankle to brachial pressure indices (ABPI) were obtained from patients attending a vascular measurement laboratory. A single PPG pulse from each big toe was recorded direct to computer, pre-processed, and then used as classifier input data. The correct classifier outputs were the corresponding ABPI diagnostic classification. Pulse and ABPI measurements from 100 legs were used as training data for each classifier, and the computed classifications for pulses from a further 266 legs were then compared with their ABPI diagnoses. The diagnostic accuracy of the artificial neural network (80%; was higher than for the optimized k-nearest neighbour classifier (k = 27, accuracy 76% and the linear discriminant classifier (71%). The Kappa measure of agreement which excludes chance was highest for the artificial neural network (57%) and significantly higher than that of the linear discriminant classifier (Kappa 40%, p < 0.05). The value of Kappa for the optimized k-nearest neighbour classifier (k = 27) was intermediate at 47%. This study has shown that classifiers can be taught to discriminate between small, and perhaps subtle, differences in features. We have demonstrated that artificial neural networks can be used to classify arterial pulse waveforms, and can perform better overall than k-nearest neighbour or linear discriminant classifiers for this application.

  15. Artificial neural network based pulse shape analysis in cryogenic detectors for rare event searches

    Energy Technology Data Exchange (ETDEWEB)

    Zoeller, Andreas [Physik Department E15, Technische Universitaet Muenchen, 85748 Garching (Germany); Collaboration: CRESST-Collaboration

    2015-07-01

    We present a method based on an Artificial Neural Network for a pulse shape analysis in cryogenic detectors. To train the neural network a huge amount of pulses with known properties are necessary. Therefore, a data-driven simulation used to generate these sets is explained. Furthermore, these simulations allow detailed studies, especially of the cut efficiency and the signal purity of the developed cut. First results are presented and compared with the performance of alternative algorithms.

  16. Bomb pulse biology

    Energy Technology Data Exchange (ETDEWEB)

    Falso, Miranda J. Sarachine [Center for Accelerator Mass Spectrometry, Mail Stop L-397, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551 (United States); Buchholz, Bruce A., E-mail: buchholz2@llnl.gov [Center for Accelerator Mass Spectrometry, Mail Stop L-397, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551 (United States)

    2013-01-15

    The past decade has seen an explosion in use of the {sup 14}C bomb pulse to do fundamental cell biology. Studies in the 1960s used decay counting to measure tissue turnover when the atmospheric {sup 14}C/C concentration was changing rapidly. Today bulk tissue measurements are of marginal interest since most of the carbon in the tissue resides in proteins, lipids and carbohydrates that turn over rapidly. Specific cell types with specialized functions are the focus of cell turnover investigations. Tissue samples need to be fresh or frozen. Fixed or preserved samples contain petroleum-derived carbon that has not been successfully removed. Cell or nuclear surface markers are used to sort specific cell types, typically by fluorescence-activated cell sorting (FACS). Specific biomolecules need to be isolated with high purity and accelerator mass spectrometry (AMS) measurements must accommodate samples that generally contain less than 40 {mu}g of carbon. Furthermore, all separations must not add carbon to the sample. Independent means such as UV absorbance must be used to confirm molecule purity. Approaches for separating specific proteins and DNA and combating contamination of undesired molecules are described.

  17. Pulsed electron beam precharger

    Energy Technology Data Exchange (ETDEWEB)

    Finney, W.C. (ed.); Shelton, W.N.

    1990-01-01

    Electrostatic collection of a high resistivity aerosol using the Electron Beam Precipitator (EBP) collecting section was demonstrated during this reporting period (Quarter Five). Collection efficiency experiments were designed to confirm and extend some of the work performed under the previous contract. The reason for doing this was to attempt to improve upon the collection efficiency of the precipitator alone when testing with a very high resistivity, moderate-to-high concentration dust load. From the collector shakedown runs, a set of suitable operational parameters were determined for the downstream electrostatic collecting sections of the Electron Beam Precipitator wind tunnel. These parameters, along with those for the MINACC electron beam, will generally be held constant while the numerous precharging parameters are varied to produce an optimum particle charge. The electrostatic collector experiments were part of a larger, comprehensive investigation on electron beam precharging of high resistivity aerosol particles performed during the period covered by Quarters Five, Six, and Seven. This body of work used the same experimental apparatus and procedures and the experimental run period lasted nearly continuously for six months. A summary of the Quarter Five work is presented in the following paragraphs. Section II-A of TPR 5 contains a report on the continuing effort which was expended on the modification and upgrade of the pulsed power supply and the monitoring systems prior to the initiation of the electron beam precharging experimental work.

  18. Magnetic Alignment of Pulsed Solenoids Using the Pulsed Wire Method

    Energy Technology Data Exchange (ETDEWEB)

    Arbelaez, D.; Madur, A.; Lipton, T.M.; Waldron, W.L.; Kwan, J.W.

    2011-04-01

    A unique application of the pulsed-wire measurement method has been implemented for alignment of 2.5 T pulsed solenoid magnets. The magnetic axis measurement has been shown to have a resolution of better than 25 {micro}m. The accuracy of the technique allows for the identification of inherent field errors due to, for example, the winding layer transitions and the current leads. The alignment system is developed for the induction accelerator NDCX-II under construction at LBNL, an upgraded Neutralized Drift Compression experiment for research on warm dense matter and heavy ion fusion. Precise alignment is essential for NDCX-II, since the ion beam has a large energy spread associated with the rapid pulse compression such that misalignments lead to corkscrew deformation of the beam and reduced intensity at focus. The ability to align the magnetic axis of the pulsed solenoids to within 100 pm of the induction cell axis has been demonstrated.

  19. Causality effects on accelerating light pulses

    National Research Council Canada - National Science Library

    Kaminer, Ido; Lumer, Yaakov; Segev, Mordechai; Christodoulides, Demetrios N

    2011-01-01

    .... We explore the effects of causality, and find that, whereas decelerating pulses can asymptotically reach zero group velocity, pulses that accelerate towards infinite group velocity inevitably break...

  20. French Training

    CERN Multimedia

    Françoise Benz

    2003-01-01

    General and Professional French Courses The next session will take place: from 13 October to 19 December 2003. 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 or contact Mrs. Fontbonne: Tel. 72844. Writing Professional Documents in French 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 or contact Mrs. Fontbonne: Tel. 72844. Language Training Françoise Benz Tel.73127 language.training@cern.ch

  1. Tunable high-harmonic generation by chromatic focusing of few-cycle laser pulses

    Science.gov (United States)

    Holgado, W.; Hernández-García, C.; Alonso, B.; Miranda, M.; Silva, F.; Varela, O.; Hernández-Toro, J.; Plaja, L.; Crespo, H.; Sola, I. J.

    2017-06-01

    In this work we study the impact of chromatic focusing of few-cycle laser pulses on high-order-harmonic generation (HHG) through analysis of the emitted extreme ultraviolet (XUV) radiation. Chromatic focusing is usually avoided in the few-cycle regime, as the pulse spatiotemporal structure may be highly distorted by the spatiotemporal aberrations. Here, however, we demonstrate it as an additional control parameter to modify the generated XUV radiation. We present experiments where few-cycle pulses are focused by a singlet lens in a Kr gas jet. The chromatic distribution of focal lengths allows us to tune HHG spectra by changing the relative singlet-target distance. Interestingly, we also show that the degree of chromatic aberration needed for this control does not degrade substantially the harmonic conversion efficiency, still allowing for the generation of supercontinua with the chirped-pulse scheme, demonstrated previously for achromatic focusing. We back up our experiments with theoretical simulations reproducing the experimental HHG results depending on diverse parameters (input pulse spectral phase, pulse duration, and focus position) and proving that, under the considered parameters, the attosecond pulse train remains very similar to the achromatic case, even showing cases of isolated attosecond pulse generation for near-single-cycle driving pulses.

  2. Athletic training. Personal performance development and training.

    OpenAIRE

    Broda, Michal

    2011-01-01

    Athletic training. Personal performance development and training. Objectives: The aim of this study was to analyze performance development and training of Michal Broda during his existing athletic career with focus on training after year 2004. We investigated the use of heart rate monitoring for training optimization. We also discussed training adequacy in terms of annual training cycle. Methods: In our work we used empirical methods of pedagogical research. We obtained different qualitative ...

  3. Pulsed ultrasonic stir welding method

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    A method of performing ultrasonic stir welding uses a welding head assembly to include a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. In the method, the rod is rotated about its longitudinal axis during a welding operation. During the welding operation, a series of on-off ultrasonic pulses are applied to the rod such that they propagate parallel to the rod's longitudinal axis. At least a pulse rate associated with the on-off ultrasonic pulses is controlled.

  4. Hyper dispersion pulse compressor for chirped pulse amplification systems

    Science.gov (United States)

    Barty, Christopher P. J.

    2011-11-29

    A grating pulse compressor configuration is introduced for increasing the optical dispersion for a given footprint and to make practical the application for chirped pulse amplification (CPA) to quasi-narrow bandwidth materials, such as Nd:YAG. The grating configurations often use cascaded pairs of gratings to increase angular dispersion an order of magnitude or more. Increased angular dispersion allows for decreased grating separation and a smaller compressor footprint.

  5. Flattop pulse generation based on the combined action of active mode locking and nonlinear polarization rotation.

    Science.gov (United States)

    Fang, Xiaohui; Wai, P K A; Lu, Chao; Chen, Jinhua

    2014-02-10

    A pulse-width-tunable 10 GHz flattop pulse (FTP) train is generated based on the combined action of active mode locking and nonlinear polarization rotation pulse shaping. Although the setup was previously used for other applications, the mechanism of FTP generation based on it is first analyzed and confirmed in the experiment. An FTP with pulse width tunable from 12 to 20 ps by changing polarization controllers is generated within the wavelength tuning range of 20 nm. The generated pulse reveals good stability, with the side mode suppression ratio of 65 dB, timing jitter of 92 fs, and amplitude fluctuation of 0.36%.

  6. Pulse-to-pulse Diagnostics at High Reprate

    Science.gov (United States)

    Green, Bertram; Kovalev, Sergey; Golz, Torsten; Stojanovich, Nikola; Fisher, Alan; Kampfrath, Tobias; Gensch, Michael

    2016-03-01

    Femtosecond level diagnostic and control of sub-picosecond electron bunches is an important topic in modern accelerator research. At the same time new linear electron accelerators based on quasi-CW SRF technology will be the drivers of many future 4th Generation lightsources such as X-ray free electron lasers. A high duty cycle, high stability and online pulse to pulse diagnostic at these new accelerators are crucial ingredients to the success of these large scale facilities. A novel THz based online monitor concept is presented that has the potential to give access to pulse to pulse information on bunch form, arrival time and energy at high repetition rate and down to sub pC charges. We furthermore show experimentally that pulse to pulse arrival time measurements can be used to perform pump-probe experiments with a temporal resolution in the few-fs regime and an exceptional dynamic range. Our scheme has been tested at the superradiant test facility TELBE, but can be readily transferred to other SRF accelerator driven photon sources, such as X-FELs.

  7. Pulsed light and pulsed electric field for foods and eggs.

    Science.gov (United States)

    Dunn, J

    1996-09-01

    Two new technologies for use in the food industry are described. The first method discussed uses intense pulse of light. This pulsed light (PureBright) process uses short duration flashes of broad spectrum "white" light to kill all exposed microorganisms, including vegetative bacteria, microbial and fungal spores, viruses, and protozoan oocysts. Each pulse, or flash, of light lasts only a few hundred millionths of a second (i.e., a few hundred microseconds). The intensity of each flash of light is about 20,000 times the intensity of sunlight at the earth's surface. The flashes are typically applied at a rate of about one to tens of flashes per second. For most applications, a few flashes applied in a fraction of a second provide an effective treatment. High microbial kill can be achieved, for example, on the surfaces of packaging materials, on packaging and processing equipment, foods, and medical devices as well as on many other surfaces. In addition, some bulk materials such as water and air that allow penetration of the light can be sterilized. The results of tests to measure the effects of pulsed light on Salmonella enteritiditis on eggs are presented. The second method discussed uses multiple, short duration, high intensity electric field pulses to kill vegetative microorganisms in pumpable products. This pulsed electric field (or CoolPure) process can be applied at modest temperatures at which no appreciable thermal damage occurs and the original taste, color, texture, and functionality of products can be retained.

  8. Fractional high-harmonic combs by attosecond-precision split-spectrum pulse control

    Directory of Open Access Journals (Sweden)

    Laux Martin

    2013-03-01

    Full Text Available Few-cycle laser fields enable pulse-shaping control of high-order harmonic generation by time delaying variable broadband spectral sections. We report the experimental generation of fractional (noninteger high-harmonic combs by the controlled interference of two attosecond pulse trains. Additionally the energy of the high harmonics is strongly tuned with the relative time delay. We quantify the tuning to directly result from the controlled variation of the instantaneous laser frequency at the shaped driver pulse intensity maximum.

  9. Generation of nanosecond pulses in a barrier-discharge XeBr excimer lamp

    Science.gov (United States)

    Avdeev, S. M.; Kostyrya, I. D.; Sosnin, É. A.; Tarasenko, V. F.

    2006-07-01

    The subject of investigation is the coaxial two-barrier short-pulse excimer lamp based on XeBr* molecules (λ = 282 nm). When the working mixture (Xe: Br2 = 70: 1) is excited by a high-voltage pulsed nanosecond discharge at a pressure of 1 atm, the peak power of the generated radiation is on the order of 100 kW at an FWHM of 4.5 ns. If the gap between the barriers is small, a train of pulses with an FWHM of 20 ns and a repetition rate of 200 kHz may be obtained.

  10. Temporal Behaviour of Harmonics from One-Dimensional H2+ in an UltrashortLaser Pulse

    Institute of Scientific and Technical Information of China (English)

    屈卫星; 李儒新; 徐至展; 夏宇兴; 甘明龙

    2001-01-01

    With the method of wavelet transform, we consider the temporal behaviour of high-order harmonic generationfrom one-dimensional H2+ exposed to an ultrashort laser pulse with a duration of tens of femtoseconds. The results, which are calculated by numerically solving the corresponding time-dependent Schrodinger equation with the split-operator method in the non-Born-Oppenheimer approach, show that: (1) the high-order harmonics in the cut-off range emitted as a train of pulses have better coherence than those in the plateau; (2) the harmonics are emitted early in time when the intensity of the laser pulse increases.

  11. Temporal transformation of periodic incoherent ultrashort light pulses by chirped fiber gratings.

    Science.gov (United States)

    Zalvidea, Dobryna; Duchowicz, Ricardo; Sicre, Enrique E

    2004-05-20

    The analogy between free-space propagation of optical beams and light-pulse reflection from linearly chirped fiber gratings is used to analyze the Lau effect in the temporal domain. The coherence conditions that are satisfied in the spatial domain for obtaining, at certain fixed locations, periodic fringes patterns are reformulated for guided light propagation. In this analogy, spatial periodic irradiance distributions are transformed in periodic sequences of light pulses. An optical setup is proposed to produce sharp pulse trains, with minimal distortion effects, that have repetition frequencies that are different from those associated with the input periodic optical signal. Some numerical results are given to illustrate this approach.

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

    Directory of Open Access Journals (Sweden)

    Shota Kajikawa

    2017-06-01

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

  13. Experimental investigation of a novel microchip laser producing synchronized dual-frequency laser pulse with an 85 GHz interval

    Science.gov (United States)

    Hu, M.; An, R. D.; Zhang, H.; Huang, Q. F.; Ge, J. H.

    2013-01-01

    A novel self-Q-switched microchip laser is introduced, which can produce synchronized dual-frequency laser pulse trains. By adopting a prepump mechanism, as well as shifting the gain curve and resonance wavelengths, the relative gains of π and σ polarization modes are adjusted, which offers an effective way to finely synchronize the laser pulses. By employing a 0.9 mm length monolithic cavity, a pair of synchronized pulse trains with a frequency separation of 85 GHz (0.32 nm) is achieved, which nearly approaches the gain bandwidth of the laser medium. Another separated cavity with a length of 2.8 mm operates in the same way for further investigation of microwave generation. A radiofrequency signal with frequency of 26.565 GHz is achieved by beat-noting of the synchronized laser pulse trains with 0.1 nm wavelength separation.

  14. Treatment of Persistent Facial Postinflammatory Hyperpigmentation With Novel Pulse-in-Pulse Mode Intense Pulsed Light.

    Science.gov (United States)

    Park, Ji-Hye; Kim, Jung-In; Kim, Won-Serk

    2016-02-01

    Postinflammatory hyperpigmentation (PIH) is an acquired hypermelanosis induced by various causes including inflammatory dermatoses, injury, or cosmetic procedures, such as lasers or chemical peels, and it tends to affect dark-skinned people with greater frequency and severity. There are a variety of treatment options for PIH, including topical agents, chemical peels, laser, and light therapy. However, the results are not up to expectation. The purpose of this study was to examine the clinical efficacy and safety of novel pulse-in-pulse mode intense pulsed light (IPL) for the treatment of persistent facial PIH in Korean patients. Twenty-five Korean female patients (Fitzpatrick skin types III-V) with persistent facial PIH were enrolled in the study. The patients were treated with novel pulse-in-pulse mode IPL for 4 sessions at 1-week interval and 4 sessions at 2-week intervals. Treatment efficacy and patient satisfaction were evaluated using photographs and questionnaires. After 2 months of all treatments, 23 patients (92%) had more than 50% improvement and 22 patients (88%) were satisfied with the treatments. No adverse effects or aggravations were reported. The pulse-in-pulse mode IPL treatment is effective and safe for persistent facial PIH in dark-skinned patients.

  15. ACADEMIC TRAINING

    CERN Multimedia

    Françoise Benz

    2002-01-01

    12, 13, 14, March LECTURE SERIES from 11.00 to 12.00 hrs - Auditorium, bldg. 500 POSTPONED! - Modern Project Management Methods - POSTPONED! By G. Vallet / Ed. Highware, Paris, F. Academic Training Françoise Benz Secretariat Tel. 73127 francoise.benz@cern.ch

  16. Language training

    CERN Multimedia

    2006-01-01

    If you wish to participate in one of the following courses, please tell to your supervisor and apply electronically 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 Departmental Secretariat or from your DTO (Departmental Training Officer). Applications will be accepted in the order in which they are received. General and Professional English Courses The next session will take place from beginning of October 2006 to beginning of February 2007 (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 Tessa Osborne, tel.16 23 40. Oral Expression The next session will take place from beginning of October 2006 to beginning of February 2007 (3 weeks break at Christmas).This course is intended for people with a good knowl...

  17. Language Training

    CERN Multimedia

    Françoise Benz

    2005-01-01

    If you wish to participate in one of the following courses, please tell to your supervisor and apply electronically 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 Departmental Secretariat or from your DTO (Departmental Training Officer). Applications will be accepted in the order in which they are received. General and Professional English Courses The next session will take place: from end of September 2005 to middle of February 2006 (2/ 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 The next session will take place from end of September to December 2005. This course is intended for people with a good knowledge of English who want to practise and maintain the...

  18. Language training

    CERN Multimedia

    Françoise Benz

    2006-01-01

    If you wish to participate in one of the following courses, please tell to your supervisor and apply electronically 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 Departmental Secretariat or from your DTO (Departmental Training Officer). Applications will be accepted in the order in which they are received. General and Professional English Courses The next session will take place from beginning of October 2006 to beginning of February 2007 (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 Tessa Osborne, tel.16 23 40. Oral Expression The next session will take place from beginning of October 2006 to beginning of February 2007 (3 weeks break at Christmas).This course is intended for people with a goo...

  19. Technical Training: Technical Training Seminar

    CERN Multimedia

    2004-01-01

    TECHNICAL TRAINING Monique Duval tel. 74924 technical.training@cern.ch Monday 9 February 2004 From 10:00 to 12:00 - IT Auditorium - bldg. 31, 3rd floor ANSOFT High-Frequency Seminar David Prestaux, Application Engineer, ANSOFT F-78535 BUC, France This Technical Training seminar will present two Ansoft application products: Ansoft HFSS and Ansoft Designer. Ansoft HFSS makes use of the Finite Element Method (FEM) to calculate field solutions from first principles. It can accurately predict all high-frequency behaviours such as dispersion, mode conversion, and losses due to materials and radiation. Ansoft Designer is a suite of design tools to fully integrate high-frequency, physics-based electromagnetic simulations into a seamless system-level simulation environment. Ansoft Designer uses a simple interface to give complete control over every design task, by a method allowing multiple solvers, Solver on Demand. • Introduction • Overview of the Ansoft Total solution • Ansoft HFSS 9...

  20. Intense pulsed neutron source

    Science.gov (United States)

    The IPNS Progress Report 10th Anniversary Edition is being published in recognition of the first ten years of successful IPNS operation. To emphasize the significance of this milestone, we wanted this report to stand apart from the previous IPNS Progress Reports, and the best way to do this, we thought, was to make the design and organization of the report significantly different. In their articles, authors were asked to emphasize not only advances made since IPNS began operating but also the groundwork that was laid at its predecessor facilities - Argonne's ZING-P and ZING-P' prototype pulsed neutron sources and CP-5 reactor. Each article stands as a separate chapter in the report, since each represents a particular instrument or class of instruments, system, technique, or area of research. In some cases, contributions were similar to review articles in scientific journals, complete with extensive lists of references. Ten-year cumulative lists of members of IPNS committees and of scientists who have visited or done experiments at IPNS were assembled. A list of published and 'in press' articles in journals, books, and conference proceedings, resulting from work done at IPNS during the past ten years, was compiled. And archival photographs of people and activities during the ten-year history of IPNS were located and were used liberally throughout the report. The titles of the chapters in this report are: accelerator; computer; radiation effects; powder; stress; single crystal; superconductivity; amorphous; small angle; reflection; quasielastic; inelastic; inelastic magnetic; deep inelastic; user program; the future; and publications.

  1. Next generation Chirped Pulse Amplification

    Energy Technology Data Exchange (ETDEWEB)

    Nees, J.; Biswal, S.; Mourou, G. [Univ. Michigan, Center for Ultrafast Optical Science, Ann Arbor, MI (United States); Nishimura, Akihiko; Takuma, Hiroshi

    1998-03-01

    The limiting factors of Chirped Pulse Amplification (CPA) are discussed and experimental results of CPA in Yb:glass regenerative amplifier are given. Scaling of Yb:glass to the petawatt level is briefly discussed. (author)

  2. Rapidly pulsed helium droplet source

    Energy Technology Data Exchange (ETDEWEB)

    Pentlehner, Dominik; Riechers, Ricarda; Dick, Bernhard; Slenczka, Alkwin [Institute for Physical and Theoretical Chemistry, University of Regensburg, 93053 Regensburg (Germany); Even, Uzi; Lavie, Nachum; Brown, Raviv; Luria, Kfir [Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Ramat Aviv, 69978 Tel Aviv (Israel)

    2009-04-15

    A pulsed valve connected to a closed-cycle cryostat was optimized for producing helium droplets. The pulsed droplet beam appeared with a bimodal size distribution. The leading part of the pulse consists of droplets suitable for doping with molecules. The average size of this part can be varied between 10{sup 4} and 10{sup 6} helium atoms, and the width of the distribution is smaller as compared to a continuous-flow droplet source. The system has been tested in a single pulse mode and at repetition rates of up to 500 Hz with almost constant intensity. The droplet density was found to be increased by more than an order of magnitude as compared to a continuous-flow droplet source.

  3. Low-noise pulse conditioner

    Science.gov (United States)

    Bird, D.A.

    1981-06-16

    A low-noise pulse conditioner is provided for driving electronic digital processing circuitry directly from differentially induced input pulses. The circuit uses a unique differential-to-peak detector circuit to generate a dynamic reference signal proportional to the input peak voltage. The input pulses are compared with the reference signal in an input network which operates in full differential mode with only a passive input filter. This reduces the introduction of circuit-induced noise, or jitter, generated in ground referenced input elements normally used in pulse conditioning circuits, especially speed transducer processing circuits. This circuit may be used for conditioning the sensor signal from the Fidler coil in a gas centrifuge for separation of isotopic gaseous mixtures.

  4. Pulse tube refrigerator; Parusukan reitoki

    Energy Technology Data Exchange (ETDEWEB)

    Hozumi, Yoshikazu [University of Tsukuba, Tsukuba (Japan); Shiraishi, Masao [Hiroshima University, Hiroshima (Japan)

    1999-06-05

    In the cryogenic field, high temperature superconductivity and research and development of the peripheral technology are popular. Refrigerating machine development of the very low temperature is also one of the results. Research and development are mainly advanced as a refrigerating machine of the center for the aerospace plane installation. There is special and small very low temperature refrigerating machine called 'the pulse tube refrigerating machine' of which the practical application is also recently being attempted for the semiconductor cooling using high temperature superconductivity. At present, the basic research of elucidation of refrigeration phenomenon of pulse tube refrigerating machine and development of high-performance pulse tube refrigerating machine is carried out by experiment in the Ministry of International Trade and Industry Mechanical Engineering Lab., Agency of Industrial Sci. and Technology and numerical simulation in Chiyoda Corp. In this report, the pulse tube refrigerating machine is introduced, and the application in the chemical engineering field is considered. (NEDO)

  5. Pulsed ultrasonic stir welding system

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    An ultrasonic stir welding system includes a welding head assembly having a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. During a welding operation, ultrasonic pulses are applied to the rod as it rotates about its longitudinal axis. The ultrasonic pulses are applied in such a way that they propagate parallel to the longitudinal axis of the rod.

  6. Optical pulses, lasers, measuring techniques

    CERN Document Server

    Früngel, Frank B A

    1965-01-01

    High Speed Pulse Technology: Volume II: Optical Pulses - Lasers - Measuring Techniques focuses on the theoretical and engineering problems that result from the capacitor discharge technique.This book is organized into three main topics: light flash production from a capacitive energy storage; signal transmission and ranging systems by capacitor discharges and lasers; and impulse measuring technique. This text specifically discusses the air spark under atmospheric conditions, industrial equipment for laser flashing, and claims for light transmitting system. The application of light impulse sign

  7. Pulsed feedback defers cellular differentiation.

    Directory of Open Access Journals (Sweden)

    Joe H Levine

    2012-01-01

    Full Text Available Environmental signals induce diverse cellular differentiation programs. In certain systems, cells defer differentiation for extended time periods after the signal appears, proliferating through multiple rounds of cell division before committing to a new fate. How can cells set a deferral time much longer than the cell cycle? Here we study Bacillus subtilis cells that respond to sudden nutrient limitation with multiple rounds of growth and division before differentiating into spores. A well-characterized genetic circuit controls the concentration and phosphorylation of the master regulator Spo0A, which rises to a critical concentration to initiate sporulation. However, it remains unclear how this circuit enables cells to defer sporulation for multiple cell cycles. Using quantitative time-lapse fluorescence microscopy of Spo0A dynamics in individual cells, we observed pulses of Spo0A phosphorylation at a characteristic cell cycle phase. Pulse amplitudes grew systematically and cell-autonomously over multiple cell cycles leading up to sporulation. This pulse growth required a key positive feedback loop involving the sporulation kinases, without which the deferral of sporulation became ultrasensitive to kinase expression. Thus, deferral is controlled by a pulsed positive feedback loop in which kinase expression is activated by pulses of Spo0A phosphorylation. This pulsed positive feedback architecture provides a more robust mechanism for setting deferral times than constitutive kinase expression. Finally, using mathematical modeling, we show how pulsing and time delays together enable "polyphasic" positive feedback, in which different parts of a feedback loop are active at different times. Polyphasic feedback can enable more accurate tuning of long deferral times. Together, these results suggest that Bacillus subtilis uses a pulsed positive feedback loop to implement a "timer" that operates over timescales much longer than a cell cycle.

  8. Artistic Representation with Pulsed Holography

    Science.gov (United States)

    Ishii, S.

    2013-02-01

    This thesis describes artistic representation through pulsed holography. One of the prevalent practical problems in making holograms is object movement. Any movement of the object or film, including movement caused by acoustic vibration, has the same fatal results. One way of reducing the chance of movement is by ensuring that the exposure is very quick; using a pulsed laser can fulfill this objective. The attractiveness of using pulsed laser is based on the variety of materials or objects that can be recorded (e.g., liquid material or instantaneous scene of a moving object). One of the most interesting points about pulsed holograms is that some reconstructed images present us with completely different views of the real world. For example, the holographic image of liquid material does not appear fluid; it looks like a piece of hard glass that would produce a sharp sound upon tapping. In everyday life, we are unfamiliar with such an instantaneous scene. On the other hand, soft-textured materials such as a feather or wool differ from liquids when observed through holography. Using a pulsed hologram, we can sense the soft touch of the object or material with the help of realistic three-dimensional (3-D) images. The images allow us to realize the sense of touch in a way that resembles touching real objects. I had the opportunity to use a pulsed ruby laser soon after I started to work in the field of holography in 1979. Since then, I have made pulsed holograms of activities, including pouring water, breaking eggs, blowing soap bubbles, and scattering feathers and popcorn. I have also created holographic art with materials and objects, such as silk fiber, fabric, balloons, glass, flowers, and even the human body. Whenever I create art, I like to present the spectator with a new experience in perception. Therefore, I would like to introduce my experimental artwork through those pulsed holograms.

  9. High Voltage Pulse Testing Survey.

    Science.gov (United States)

    1985-10-01

    Cryogenic 23 E. Liquids 26 F. Solids 28 1. Polyethylene 28 2. Cross-Linked Polyethylene ( XLPE ) 29 3. Polyimide and Polyvenylchloride (PVC) 31 VI Benefits 35 A...Strength of XLPE Cables 29 vii * 4" I PROGRAM OBJECTIVES The Pulse Test Survey summarizes government, industry, and technical reports on high voltage pulse...system of silicone oil on a XLPE (cross-linked polyethylene) spacer tends to lower the impulse breakdown by approximately 10 percent. The negative impulse

  10. 3.7 GHz repetition rate operated narrow-bandwidth picosecond pulsed Yb fiber amplifier with an all-fiber multiplier

    Science.gov (United States)

    Wei, K. H.; Wen, R. H.; Guo, Y.

    2016-04-01

    A high power picosecond pulsed Yb fiber amplifier with a pulse repetition rate of 3.7 GHz is experimentally demonstrated. The seed is a gain switched distributed Bragg reflection (DBR) structured laser diode (LD) with a pulse duration of 130 ps and a repetition rate of 460 MHz. The pulse repetition rate is increased to 3.7 GHz by introducing an all-fiber multiplier, which is composed of four 2  ×  2 structured fiber couplers. The multiplied pulse train is amplified to 81 W through two stage Yb fiber amplifiers.

  11. Millijoule pulse energy picosecond fiber chirped-pulse amplification system

    Institute of Scientific and Technical Information of China (English)

    Zhi Yang; Xiaohong Hu; Yishan Wang; Wei Zhang; Wei Zhao

    2011-01-01

    @@ The efficient generation of a 1.17-mJ laser pul8e with 360 ps duration using an ytterbium (Yb)-doped fiber amplifier chain seeded by a homemade mode-locked fiber laser is demonstrated experimentally.A specially designed figure-of-eight fiber laser acts as the seed source of a chirped-pulse amplification (CPA) system and generates mode-locked pulse8 with hundreds of picosecond widths.Two kinds of large-mode-area (LMA) double-clad Yb-doped fibers are employed to construct the pre-amplifier and main amplifier, All of the adopted instruments help avoid severe nonlinearity in fibers to raise sub-nanosecond pulse energy with acceptable signal-to-noise ratio (SNR).The output spectrum of this fiber-based CPA system shows that amplified spontaneous emission (ASE) is suppressed to better than 30 dB, and the onset of stimulated Raman scattering is excluded.%The efficient generation of a 1.17-mJ laser pulse with 360 ps duration using an ytterbium (Yb)-doped fiber amplifier chain seeded by a homemade mode-locked fiber laser is demonstrated experimentally. A specially designed figure-of-eight fiber laser acts as the seed source of a chirped-pulse amplification (CPA) system and generates mode-locked pulses with hundreds of picosecond widths. Two kinds of large-mode-area (LMA) double-clad Yb-doped fibers are employed to construct the pre-amplifier and main amplifier. All of the adopted instruments help avoid severe nonlinearity in fibers to raise sub-nanosecond pulse energy with acceptable signal-to-noise ratio (SNR). The output spectrum of this fiber-based CPA system shows that amplified spontaneous emission (ASE) is suppressed to better than 30 dB, and the onset of stimulated Raman scattering is excluded.

  12. Can YAG screen accept LEReC bunch train?

    Energy Technology Data Exchange (ETDEWEB)

    Seletskiy S.; Thieberger, P.; Miller, T.

    2016-05-18

    LEReC RF diagnostic beamline is supposed to accept 250 us long pulse trains of 1.6 MeV – 2.6 MeV (kinetic energy) electrons. This beamline is equipped with YAG profile monitor. Since we are interested in observing only the last macro bunch in the train, one of the possibilities is to install a fast kicker and a dedicated dump upstream of the YAG screen (and related diagnostics equipment). This approach is expensive and challenging from engineering point of view. Another possibility is to send the whole pulse train to the YAG screen and to use a fast gated camera (such as Imperex B0610 with trigger jitter under 60ns) to observe the image from the last pulse only. In this paper we study the feasibility of the last approach.

  13. Square pulse linear transformer driver

    Directory of Open Access Journals (Sweden)

    A. A. Kim

    2012-04-01

    Full Text Available The linear transformer driver (LTD technological approach can result in relatively compact devices that can deliver fast, high current, and high-voltage pulses straight out of the LTD cavity without any complicated pulse forming and pulse compression network. Through multistage inductively insulated voltage adders, the output pulse, increased in voltage amplitude, can be applied directly to the load. The usual LTD architecture [A. A. Kim, M. G. Mazarakis, V. A. Sinebryukhov, B. M. Kovalchuk, V. A. Vizir, S. N Volkov, F. Bayol, A. N. Bastrikov, V. G. Durakov, S. V. Frolov, V. M. Alexeenko, D. H. McDaniel, W. E. Fowler, K. LeCheen, C. Olson, W. A. Stygar, K. W. Struve, J. Porter, and R. M. Gilgenbach, Phys. Rev. ST Accel. Beams 12, 050402 (2009PRABFM1098-440210.1103/PhysRevSTAB.12.050402; M. G. Mazarakis, W. E. Fowler, A. A. Kim, V. A. Sinebryukhov, S. T. Rogowski, R. A. Sharpe, D. H. McDaniel, C. L. Olson, J. L. Porter, K. W. Struve, W. A. Stygar, and J. R. Woodworth, Phys. Rev. ST Accel. Beams 12, 050401 (2009PRABFM1098-440210.1103/PhysRevSTAB.12.050401] provides sine shaped output pulses that may not be well suited for some applications like z-pinch drivers, flash radiography, high power microwaves, etc. A more suitable power pulse would have a flat or trapezoidal (rising or falling top. In this paper, we present the design and first test results of an LTD cavity that generates such a type of output pulse by including within its circular array a number of third harmonic bricks in addition to the main bricks. A voltage adder made out of a square pulse cavity linear array will produce the same shape output pulses provided that the timing of each cavity is synchronized with the propagation of the electromagnetic pulse.

  14. High-Altitude Electromagnetic Pulse (HEMP) Testing

    Science.gov (United States)

    2015-07-09

    Electromagnetic Pulse Horizontal Electromagnetic Pulse Advanced Fast Electromagnetic Pulse Nuclear Weapons Effect Testing and Environments 16. SECURITY...TOP 01-2-620A 9 July 2015 G-1 APPENDIX G. ABBREVIATIONS. AFEMP Advanced Fast Electromagnetic ... Electromagnetic Pulse A burst of electromagnetic radiation from a nuclear explosion or a suddenly fluctuating magnetic field. The resulting electric and

  15. Sports Training

    Science.gov (United States)

    1988-01-01

    Practitioners of martial arts have long seen a need for a precise method of measuring the power of a karate kick or a boxer's punch in training and competition. Impax sensor is a piezoelectric film less than one thousandth of an inch thick, yet extremely durable. They give out a voltage impulse when struck, the greater the force of impact, the higher the voltage. The impulse is transmitted to a compact electronics package where voltage is translated into a force-pounds reading shown on a digital display. Impax, manufactured by Impulse Technology, Inc. is used by martial arts instructors, practitioners, U.S. Olympic Committee Training Center, football blocking sleds, and boxers as well as police defensive tactics, providing a means of evaluating the performance of recruits.

  16. Intense ultrashort terahertz pulses: generation and applications

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Matthias C [Max Planck Research Department for Structural Dynamics, University of Hamburg, CFEL, 22607 Hamburg (Germany); Fueloep, Jozsef Andras, E-mail: matthias.c.hoffmann@mpsd.cfel.de, E-mail: fulop@fizika.ttk.pte.hu [Department of Experimental Physics, University of Pecs, Ifjusag u. 6, 7624 Pecs (Hungary)

    2011-03-02

    Ultrashort terahertz pulses derived from femtosecond table-top sources have become a valuable tool for time-resolved spectroscopy during the last two decades. Until recently, the pulse energies and field strengths of these pulses have been generally too low to allow for the use as pump pulses or the study of nonlinear effects in the terahertz range. In this review article we will describe methods of generation of intense single cycle terahertz pulses with emphasis on optical rectification using the tilted-pulse-front pumping technique. We will also discuss some applications of these intense pulses in the emerging field of nonlinear terahertz spectroscopy. (topical review)

  17. Pulse compression and prepulse suppression apparatus

    Science.gov (United States)

    Dane, C.B.; Hackel, L.A.; George, E.V.; Miller, J.L.; Krupke, W.F.

    1993-11-09

    A pulse compression and prepulse suppression apparatus (10) for time compressing the output of a laser (14). A pump pulse (46) is separated from a seed pulse (48) by a first polarized beam splitter (20) according to the orientation of a half wave plate (18). The seed pulse (48) is directed into an SBS oscillator (44) by two plane mirrors (22, 26) and a corner mirror (24), the corner mirror (24) being movable to adjust timing. The pump pulse (46) is directed into an SBS amplifier 34 wherein SBS occurs. The seed pulse (48), having been propagated from the SBS oscillator (44), is then directed through the SBS amplifier (34) wherein it sweeps the energy of the pump pulse (46) out of the SBS amplifier (34) and is simultaneously compressed, and the time compressed pump pulse (46) is emitted as a pulse output (52). A second polarized beam splitter (38) directs any undepleted pump pulse 58 away from the SBS oscillator (44).

  18. Consecutive Bright Pulses in the Vela Pulsar

    CERN Document Server

    Palfreyman, Jim L; Dickey, John M; Young, Timothy G; Hotan, Claire E; 10.1088/2041-8205/735/1/L17

    2011-01-01

    We report on the discovery of consecutive bright radio pulses from the Vela pulsar, a new phenomenon that may lead to a greater understanding of the pulsar emission mechanism. This results from a total of 345 hr worth of observations of the Vela pulsar using the University of Tasmania's 26 m radio telescope to study the frequency and statistics of abnormally bright pulses and sub-pulses. The bright pulses show a tendency to appear consecutively. The observations found two groups of six consecutive bright pulses and many groups of two to five bright pulses in a row. The strong radio emission process that produces the six bright pulses lasts between 0.4 and 0.6 s. The numbers of bright pulses in sequence far exceed what would be expected if individual bright pulses were independent random events. Consecutive bright pulses must be generated by an emission process that is long lived relative to the rotation period of the neutron star.

  19. Language Training

    CERN Multimedia

    HR Department

    Permanence A "permanence" for language Training has been set up. If anyone has a question or requires information on any aspect of English or French training please come to our office 5 4-016 at the following times. Lucette Fournier - French courses Monday 13.30 - 15.30 Tuesday\t10.30 - 12.30 Tessa Osborne - English courses Wednesday\t12.00 - 14.00 Thursday\t11.00 - 13.00   New courses Specific English and French courses - Exam preparation/ We are now offering specific courses in English and French leading to a recognised external examination (e.g. Cambridge, DELF, DALF). If you are interested in following one of these courses and have at least an upper intermediate level of English or French, please enrol through the following link:  English courses French courses Or contact: Tessa Osborne 72957 (English courses) Lucette Fournier 73483 (French courses) Language Training Nathalie Dumeaux Tel. 78144 nathalie.dumeaux@cern.ch

  20. Language Training

    CERN Multimedia

    HR Department

    2009-01-01

    PermanenceA "permanence" for language Training has been set up. If anyone has a question or requires information on any aspect of English or French training please come to our office 5 4-016 at the following times. Lucette Fournier French courses Monday 13.30 - 15.30 Tuesday\t10.30 - 12.30 Tessa Osborne English courses Wednesday\t12.00 - 14.00 Thursday\t11.00 - 13.00 New courses Specific English and French courses - Exam preparation/ We are now offering specific courses in English and French leading to a recognised external examination (e.g. Cambridge, DELF and BULATS). If you are interested in following one of these courses and have at least an upper intermediate level of English or French, please enrol through the following link: http://English courses http://French courses Or contact: Tessa Osborne 72957 (English courses) Lucette Fournier 73483 (French courses) Language Training Nathalie Dumeaux Tel. 78144 mailto:nathalie.dumeaux@cern.ch

  1. Toxic Effects of Lead and Electromagnetic Pulse Energy on Memory Mechanisms

    Science.gov (United States)

    2012-08-01

    postsynaptic potentials ( EPSPs ). All data signals were digitized via a Digidata 1322A and recorded directly to computer hard disk using pCLAMP 9.0 software...varied to determine threshold values for EPSPs . Slices were stimulated with single test pulses every 30 s for at least 30 min to establish baseline... EPSPs . To induce LTP, theta-burst stimulation (TBS) was used that consisted of 3 trains applied at 30 s intervals, each train consisting of 3

  2. Unidirectional, dual-comb lasing under multiple pulse formation mechanisms in a passively mode-locked fiber ring laser

    CERN Document Server

    Liu, Ya; Hu, Guoqing; Li, Cui; Zhao, Bofeng; Zheng, Zheng

    2016-01-01

    Dual-comb lasers from which asynchronous ultrashort pulses can be simultaneously generated have recently become an interesting research subject. They could be an intriguing alternative to the current dual-laser optical-frequency-comb source with highly sophisticated electronic control systems. If generated through a common light path traveled by all pulses, the common-mode noises between the spectral lines of different pulse trains could be significantly reduced. Therefore, coherent dual-comb generation from a completely common-path, unidirectional lasing cavity would be an interesting territory to explore. In this paper, we demonstrate such a dual-comb lasing scheme based on a nanomaterial saturable absorber with additional pulse narrowing and broadening mechanisms concurrently introduced into a mode-locked fiber laser. The interactions between multiple soliton formation mechanisms result in unusual bifurcation into two-pulse states with quite different characteristics. Simultaneous oscillation of pulses wit...

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

    Energy Technology Data Exchange (ETDEWEB)

    Seddon, N.; Thornton, E.

    1988-11-01

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

  4. 脉冲序列控制电流断续模式Buck变换器的动力学建模与边界碰撞分岔%Dynamical modeling and border collision bifurcation in pulse train controlled discontinuous conduction mode buck converter

    Institute of Scientific and Technical Information of China (English)

    沙金; 包伯成; 许建平; 高玉

    2012-01-01

    According to the charge variation of output capacitor in a switching cycle, the output voltage variation in a switching cycle can be obtained, from which an approximate discrete-time model of pulse train (PT) controlled buck converter operating in discontinuous conduction mode (DCM) is established. Based on the model, the border-collision bifurcations of the PT controlled DCM buck converter with the variations of the load resistance and the input voltage are studied. By constructing the corresponding iterative map curves, the stabilities of the fixed points, formed by the orbits of period-l, period-2, period-3 and so on, are analyzed, and the mechanisms of border-collision bifurcations of the converter under different operation states are revealed. The analysis results indicate that with the variation of parameters, the PT controlled DCM buck converter always operates in different periodic states, in which the change of the operation mode with periodic state is caused by the border-collision bifurcation and the lyapunov exponent is always less than zero. By using PSIM circuit simulation software, the time domain waveforms and phase portraits under different load resistances are obtained. Experimental results are provided to verify the correctnesses of theoretical analyses and circuit simulations and the feasibility of dynamical modelling.%通过建立一个开关周期内输出电容电荷变化量对应的输出电压变化量,建立了工作于电感电流断续模式(discontinuousconductionmode,DCM)的脉冲序列(pulsetrain,VT)控制Buck变换器的近似离散时间模型,研究了负载电阻及输入电压变化时PT控制DCMBuck变换器的边界碰撞分岔行为.通过构造相应的迭代映射曲线,分别分析了不同负载电阻时阿控制DCMBuck变换器的周期1、周期2和周期3运行轨迹的不动点稳定性,揭示了PT控制DCMBuck变换器在不同周期态时的边界碰撞分岔的形成机理.研究结

  5. Wide Range SET Pulse Measurement

    Science.gov (United States)

    Shuler, Robert L.; Chen, Li

    2012-01-01

    A method for measuring a wide range of SET pulses is demonstrated. Use of dynamic logic, faster than ordinary CMOS, allows capture of short pulses. A weighted binning of SET lengths allows measurement of a wide range of pulse lengths with compact circuitry. A pulse-length-conservative pulse combiner tree routes SETs from combinational logic to the measurement circuit, allowing SET measurements in circuits that cannot easily be arranged in long chains. The method is applied to add-multiplex combinational logic, and to an array of NFET routing switches, at .35 micron. Pulses are captured in a chain of Domino Logic AND gates. Propagation through the chain is frozen on the trailing edge by dropping low the second "enable" input to the AND gates. Capacitive loading is increased in the latter stages to create an approximately logarithmic weighted binning, so that a broad range of pulse lengths can be captured with a 10 stage capture chain. Simulations show pulses can be captured which are 1/5th the length of those typically captured with leading edge triggered latch methods, and less than the length of those captured with a trailing edge latch method. After capture, the pulse pattern is transferred to an SEU protected shift register for readout. 64 instances of each of two types of logic are used as targets. One is a full adder with a 4 to 1 mux on its inputs. The other is a 4 x 4 NFET routing matrix. The outputs are passed through buffered XNOR comparators to identify pulses, which are merged in a buffered not-nand (OR) tree designed to avoid pulse absorption as much as possible. The output from each of the two test circuits are input into separate pulse measurement circuits. Test inputs were provided so that the circuit could be bench tested and calibrated. A third SET measurement circuit with no inputs was used to judge the contribution from direct hits on the measurement circuit. Heavy ions were used with an LET range from 12 to 176. At LET of 21 and below, the very

  6. The pulsing CPSD method for subcritical assemblies with pulsed sources

    CERN Document Server

    Ballester, D; Ballester, Daniel; Munoz-Cobo, Jose L.

    2005-01-01

    Stochastic neutron transport theory is applied to the derivation of the two-neutron-detectors cross power spectral density for subcritical assemblies when external pulsed sources are used. A general relationship between the two-detector probability generating functions of the kernel and the source is obtained considering the contribution to detectors statistics of both the pulsed source and the intrinsic neutron source. An expansion in alpha-eigenvalues is derived for the final solution, which permits to take into account the effect of higher harmonics in subcritical systems. Further, expressions corresponding to the fundamental mode approximation are compared with recent results from experiments performed under the MUSE-4 European research project.

  7. High field rf superconductivity: to pulse or not to pulse

    Energy Technology Data Exchange (ETDEWEB)

    Campisi, I.E.

    1984-10-01

    Experimental data on the behavior of superconductors under the application of rf fields of amplitude comparable to their critical fields are sporadic and not always consistent. In many cases the field level at which breakdown in superconducting rf cavities should be expected has not been clearly established. Tests conducted with very short (approx. 1 ..mu..s) rf pulses indicate that in this mode of operation fields close to the critical values can be consistently reached in superconducting cavities without breakdown. The advantages and disadvantages of the pulsed method are discussed compared to those of the more standard continuous wave (cw) systems. 60 references.

  8. Development of pulsed positron beam line with compact pulsing system

    Energy Technology Data Exchange (ETDEWEB)

    Maekawa, Masaki, E-mail: maekawa.masaki@jaea.go.jp [Advanced Science Research Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Kawasuso, Atsuo [Advanced Science Research Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan)

    2012-01-01

    We have developed a pulsed slow positron beam with a pulse width of less than 200 ps and a period of 25 ns. The beam apparatus is composed of a Munich-type pre-buncher, a chopper and a buncher. Instead of the conventional RF cavity, a simple double-cylinder electrode is used for the buncher. The beam will be used for positron lifetime measurements. The time resolution of the whole system including lifetime measurement circuits is 250 ps, which is adequate for studying semiconductors and metals.

  9. Variations in physician interpretation of overnight pulse oximetry monitoring.

    Science.gov (United States)

    Ramsey, Rory; Mehra, Reena; Strohl, Kingman P

    2007-09-01

    Overnight pulse oximetry is commonly used for hypoxemia evaluation in patients with COPD and sleep-disordered breathing. There is little information regarding its impact on physician decision making, and therefore an important measure of its clinical utility is untested and unknown. The aim of this study was to describe physician interpretation, use, and opinions regarding overnight pulse oximetry. Forty-one pulmonary physicians and fellows participated in structured interviews consisting of three oximetry record interpretations, oral responses to a standard question set, and a questionnaire. Qualitative data were analyzed using an open coding process. Quantitative data were assessed for distributions. Four measures were consistently used by the majority of physicians in record interpretation: background information, arterial oxygen saturation measured by pulse oximetry (Spo(2)) waveform and pattern, and time spent with Spo(2) 60% consensus. There was a wide range of opinions on important matters related to this test, including test utility, indications, variables considered most important for interpretation, and criteria for nocturnal oxygen prescription. Forty-one physicians provided 35 different opinions on when nocturnal supplemental oxygen should be initiated. The variation in physician interpretation, use, and opinions regarding overnight pulse oximetry calls into question its clinical utility and underscores a need for standardization of presentation, training, and interpretation.

  10. Pre-earthquake magnetic pulses

    Directory of Open Access Journals (Sweden)

    J. Scoville

    2014-12-01

    Full Text Available A semiconductor model of rocks is shown to describe unipolar magnetic pulses, a phenomenon that has been observed prior to earthquakes. These pulses are generated deep in the Earth's crust, in and around the Hypocentral volume, days or even weeks before Earthquakes. They are observable at the surface because their extremely long wavelength allows them to pass through kilometers of rock. Interestingly, the source of these pulses may be triangulated to pinpoint locations where stresses are building deep within the crust. We couple a semiconductor drift-diffusion model to a magnetic field in order to describe the electromagnetic effects associated with electrical currents flowing within rocks. The resulting system of equations is solved numerically and it is seen that a volume of rock may act as a diode that produces transient currents when it switches bias. These unidirectional currents are expected to produce transient unipolar magnetic pulses similar in form, amplitude, and duration to those observed before earthquakes, and this suggests that the pulses could be the result of geophysical semiconductor processes.

  11. Technical Training: Technical Training Seminar

    CERN Multimedia

    2004-01-01

    TECHNICAL TRAINING Monique Duval tel. 74924 technical.training@cern.ch Tuesday 3 February 2004 From 09:00 to 13:30 - Training Centre Auditorium - bldg. 593, room 11 USB (Universal Serial Bus) CYPRESS Seminar Claudia Colombini, Field Application Engineer CYPRESS ActiveComp Electronic GmbH D-85077 MANCHING, Germany As a pioneer in USB, CYPRESS sets the standard for cost-effective solutions without sacrificing functionality, performance or reliability. Having shipped over 200 million USB devices, Cypress is the undisputed market leader and demonstrates unmatched USB expertise. With the industry's broadest selection of USB solutions, Cypress has the right silicon, software and support for every USB application, from Low-speed to High-Speed and USB On-The-Go (OTG). 9:00 - 10:30 Overview of USB systems. USB CYPRESS product overview. Peripherals: Low Speed, Full Speed, High Speed (1.1 and 2.0). Hub Solutions, Embedded Host Solutions, On-The-Go (OTG) and wireless USB. USB Development Tools (first part) 10:30 -...

  12. Pulsed discharge production Ar* metastables

    Science.gov (United States)

    Han, Jiande; Heaven, Michael C.; Emmons, Daniel; Perram, Glen P.; Weeks, David E.; Bailey, William F.

    2016-03-01

    The production of relatively high densities of Ar* metastables (>1012 cm-3) in Ar/He mixtures, at total pressures close to 1 atm, is essential for the efficient operation of an optically pumped Ar* laser. We have used emission spectroscopy and diode laser absorption spectroscopy measurements to observe the production and decay of Ar* in a parallel plate pulsed discharge. With discharge pulses of 1 μs duration we find that metastable production is dominated by processes occurring within the first 100 ns of the gas break-down. Application of multiple, closely spaced discharge pulses yields insights concerning conditions that favor metastable production. This information has been combined with time-resolved measurements of voltage and current. The experimental results and preliminary modeling of the discharge kinetics are presented.

  13. ACADEMIC TRAINING

    CERN Multimedia

    Françoise Benz

    2002-01-01

    6, 7 May LECTURE SERIES from 11.00 to 12.00 hrs - Auditorium, bldg. 500 Decoding the Human Genome, Scientific basis and ethic and social aspects by S.E. Antonarakis and A. Mauron / Univ. of Geneva Decoding the Human genome is a very up-to-date topic, raising several questions besides purely scientific, in view of the two competing teams (public and private), the ethics of using the results, and the fact that the project went apparently faster and easier than expected. The lecture series will address the following chapters: Scientific basis and challenges, Ethical and social aspects of genomics. Academic Training Françoise Benz Tel. 73127

  14. Media Training

    CERN Document Server

    CERN. Geneva

    2009-01-01

    With the LHC starting up soon, the world's media are again turning their attention to CERN. We're all likely to be called upon to explain what is happening at CERN to media, friends and neighbours. The seminar will be given by BBC television news journalists Liz Pike and Nadia Marchant, and will deal with the kind of questions we're likely to be confronted with through the restart period. The training is open for everybody. Make sure you arrive early enough to get a seat - there are only 200 seats in the Globe. The session will also be webcast: http://webcast.cern.ch/

  15. Strength Training. A Key to Athletic Training.

    Science.gov (United States)

    Whiteside, Patricia W.

    Characteristics of an effective strength training program are analyzed and descriptions are offered of different kinds of weight training activities. Comparisons are made between concentric, isometric, eccentric, and isokinetic training methods. The fundamentals and techniques of an exemplary training program are outlined and the organization and…

  16. SELECTING AND TRAINING THE TRAINING OFFICER.

    Science.gov (United States)

    TAYLOR, NANCY

    TO ACHIEVE THE OBJECTIVES OF TRAINING IN INDUSTRY--TECHNICAL AND LIBERAL EDUCATION, SPECIFIC JOB SKILLS, AND THE DEVELOPMENT OF ATTITUDES--THE TRAINING OFFICER MUST KNOW THE COMPANY WITHIN WHICH HE IS WORKING, AS WELL AS MANAGEMENT THEORY AND TRAINING METHODS. THE SELECTION OF TRAINING OFFICERS IS BASED ON A JOB SPECIFICATION, AN OUTGROWTH OF A…

  17. Green pulsed lidar-radar emitter based on a multipass frequency-shifting external cavity.

    Science.gov (United States)

    Zhang, Haiyang; Brunel, Marc; Romanelli, Marco; Vallet, Marc

    2016-04-01

    This paper investigates the radio frequency (RF) up-conversion properties of a frequency-shifting external cavity on a laser beam. We consider an infrared passively Q-switched pulsed laser whose intensity modulation results from the multiple round-trips in the external cavity, which contains a frequency shifter. The output beam undergoes optical second-harmonic generation necessary to reach the green wavelength. We model the pulse train using a rate-equation model to simulate the laser pulses, together with a time-delayed interference calculation taking both the diffraction efficiency and the Gaussian beam propagation into account. The predictions are verified experimentally using a diode-pumped Nd:YAG laser passively Q-switched by Cr4+:YAG whose pulse train makes multiple round-trips in a mode-matched external cavity containing an acousto-optic frequency shifter driven at 85 MHz. Second-harmonic generation is realized in a KTP crystal, yielding RF-modulated pulses at 532 nm with a modulation contrast of almost 100%. RF harmonics up to the 6th order (1.020 GHz) are observed in the green output pulses. Such a RF-modulated green laser may find applications in underwater detection and ranging.

  18. Liquid micro pulsed plasma thruster

    Directory of Open Access Journals (Sweden)

    Szelecka Agnieszka

    2015-06-01

    Full Text Available A new type of pulsed plasma thruster (PPT for small satellite propulsion is investigated, of which the most innovative aspect is the use of a non-volatile liquid propellant. The thruster is based on an open capillary design. The thruster achieved a thrust-to-power ratio above 45 μN/W, which constitutes a 5-fold improvement over the water-propelled pulsed plasma thruster, and which is also slightly above the performance of a similarly sized PPT with a solid propellant.

  19. Pulse compressor with aberration correction

    Energy Technology Data Exchange (ETDEWEB)

    Mankos, Marian [Electron Optica, Inc., Palo Alto, CA (United States)

    2015-11-30

    In this SBIR project, Electron Optica, Inc. (EOI) is developing an electron mirror-based pulse compressor attachment to new and retrofitted dynamic transmission electron microscopes (DTEMs) and ultrafast electron diffraction (UED) cameras for improving the temporal resolution of these instruments from the characteristic range of a few picoseconds to a few nanoseconds and beyond, into the sub-100 femtosecond range. The improvement will enable electron microscopes and diffraction cameras to better resolve the dynamics of reactions in the areas of solid state physics, chemistry, and biology. EOI’s pulse compressor technology utilizes the combination of electron mirror optics and a magnetic beam separator to compress the electron pulse. The design exploits the symmetry inherent in reversing the electron trajectory in the mirror in order to compress the temporally broadened beam. This system also simultaneously corrects the chromatic and spherical aberration of the objective lens for improved spatial resolution. This correction will be found valuable as the source size is reduced with laser-triggered point source emitters. With such emitters, it might be possible to significantly reduce the illuminated area and carry out ultrafast diffraction experiments from small regions of the sample, e.g. from individual grains or nanoparticles. During phase I, EOI drafted a set of candidate pulse compressor architectures and evaluated the trade-offs between temporal resolution and electron bunch size to achieve the optimum design for two particular applications with market potential: increasing the temporal and spatial resolution of UEDs, and increasing the temporal and spatial resolution of DTEMs. Specialized software packages that have been developed by MEBS, Ltd. were used to calculate the electron optical properties of the key pulse compressor components: namely, the magnetic prism, the electron mirror, and the electron lenses. In the final step, these results were folded

  20. High-speed pulse techniques

    CERN Document Server

    Coekin, J A

    1975-01-01

    High-Speed Pulse Techniques covers the many aspects of technique in digital electronics and encompass some of the more fundamental factors that apply to all digital systems. The book describes the nature of pulse signals and their deliberate or inadvertent processing in networks, transmission lines and transformers, and then examines the characteristics and transient performance of semiconductor devices and integrated circuits. Some of the problems associated with the assembly of these into viable systems operating at ultra high speed are also looked at. The book examines the transients and w

  1. Neuromuscular disruption with ultrashort electrical pulses

    Science.gov (United States)

    Pakhomov, Andrei; Kolb, Juergen F.; Joshi, Ravindra P.; Schoenbach, Karl H.; Dayton, Thomas; Comeaux, James; Ashmore, John; Beason, Charles

    2006-05-01

    Experimental studies on single cells have shown that application of pulsed voltages, with submicrosecond pulse duration and an electric field on the order of 10 kV/cm, causes sudden alterations in the intracellular free calcium concentration, followed by immobilization of the cell. In order to examine electrical stimulation and incapacitation with such ultrashort pulses, experiments on anesthetized rats have been performed. The effect of single, 450 nanosecond monopolar pulses have been compared with that of single pulses with multi-microsecond duration (TASER pulses). Two conditions were explored: 1. the ability to elicit a muscle twitch, and, 2. the ability to suppress voluntary movement by using nanosecond pulses. The second condition is relevant for neuromuscular incapacitation. The preliminary results indicate that for stimulation microsecond pulses are advantageous over nanosecond pulses, whereas for incapacitation, the opposite seems to apply. The stimulation effects seem to scale with electrical charge, whereas the disruption effects don't follow a simple scaling law. The increase in intensity (time of incapacitation) for a given pulse duration, is increasing with electrical energy, but is more efficient for nanosecond than for microsecond pulses. This indicates different cellular mechanisms for incapacitation, most likely subcellular processes, which have been shown to become increasingly important when the pulse duration is shortened into the nanosecond range. If further studies can confirm these initial results, consequences of reduced pulse duration are a reduction in weight and volume of the pulse delivery system, and likely, because of the lower required energy for neuromuscular incapacitation, reduced safety risks.

  2. Control of high power pulse extracted from the maximally compressed pulse in a nonlinear optical fiber

    CERN Document Server

    Yang, Guangye; Jia, Suotang; Mihalache, Dumitru

    2013-01-01

    We address the possibility to control high power pulses extracted from the maximally compressed pulse in a nonlinear optical fiber by adjusting the initial excitation parameters. The numerical results show that the power, location and splitting order number of the maximally compressed pulse and the transmission features of high power pulses extracted from the maximally compressed pulse can be manipulated through adjusting the modulation amplitude, width, and phase of the initial Gaussian-type perturbation pulse on a continuous wave background.

  3. Pulse Delay and Speed-up of Ultra Fast Pulses in an Absorbing Quantum Well Medium

    DEFF Research Database (Denmark)

    Hansen, Per Lunnemann; Poel, Mike van der; Yvind, Kresten;

    2008-01-01

    Slow down and speed-up of 180 fs pulses in an absorbing semiconductor beyond the exisitng models is observed. Cascading gainand absorbing sections give us significant temporal pulse shifting at almost constant output pulse energy.......Slow down and speed-up of 180 fs pulses in an absorbing semiconductor beyond the exisitng models is observed. Cascading gainand absorbing sections give us significant temporal pulse shifting at almost constant output pulse energy....

  4. Dynamic Characterization of Fiber Optical Chirped Pulse Amplification for Sub-ps Pulses

    DEFF Research Database (Denmark)

    Cristofori, Valentina; Lali-Dastjerdi, Zohreh; Rishøj, Lars Søgaard

    2013-01-01

    We investigate experimentally the propagation of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers, showing a significant broadening of the pulses from 450 fs up to 720 fs due to dispersion and self-phase modulation.......We investigate experimentally the propagation of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers, showing a significant broadening of the pulses from 450 fs up to 720 fs due to dispersion and self-phase modulation....

  5. 35 Volt, 180 Ampere Pulse Generator with Droop Control for Pulsing Xenon Arcs

    DEFF Research Database (Denmark)

    Hviid, T.; Nielsen, S. O.

    1972-01-01

    The pulse generator described works as a combined switch and series current regulator and allows the shape of the current pulse to be adjusted at each optical wavelength to produce a flat pulse of monochromatic light.......The pulse generator described works as a combined switch and series current regulator and allows the shape of the current pulse to be adjusted at each optical wavelength to produce a flat pulse of monochromatic light....

  6. French training

    CERN Multimedia

    2007-01-01

    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 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 further information and registration, please consu...

  7. Language Training

    CERN Multimedia

    2003-01-01

    Formation en anglais Cours d'anglais général et professionnel La prochaine session se déroulera: du 06 octobre 2003 au 13 février 2004 (interruption de 3/4 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 Mme Benz, tél. 73127 ou Mr Liptow, tél. 72957. General and Professional English Courses The next session will take place: from 06 October 2003 to 13 February 2004 (3/4 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 Mrs. Benz: tel. 73127 or Mr. Liptow: tel. 72957. Writing Professional Documents in English This course is designed for people with a good level of spoken English. Duration: 20 hours (2 hours a week) Price: ...

  8. Language Training

    CERN Multimedia

    2003-01-01

    Formation en anglais Cours d'anglais général et professionnel La prochaine session se déroulera: du 06 octobre 2003 au 13 février 2004 (interruption de 3/4 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 06 October 2003 to 13 February 2004 (3/4 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. Writing Professional Documents in English This course is designed for people with a good level of...

  9. Language Training

    CERN Multimedia

    2003-01-01

    Formation en anglais Cours d'anglais général et professionnel La prochaine session se déroulera: du 06 octobre 2003 au 13 février 2004 (interruption de 3/4 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 Mme Benz, tél. 73127 ou Mr Liptow, tél. 72957. General and Professional English Courses The next session will take place: from 06 October 2003 to 13 February 2004 (3/4 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 Mrs. Benz: tel. 73127 or Mr. Liptow: tel. 72957. Writing Professional Documents in Engl...

  10. English Training

    CERN Multimedia

    2003-01-01

    General and Professional English Courses The next session will take place: from 03 March to 28 June 2003 (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 Mrs. Benz: tel.73127 or Mr. Liptow: tel.72957. Writing Professional Documents in English This course is designed for people with a good level of spoken English. Duration: 20 hours (2 hours a week) Price: 440 CHF (for 8 students) For registration and further information, please consult our Web pages: http://cern.ch/Training or contact Mrs. Tessa Osborne: Tessa.Osborne@cern. 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-p...

  11. English Training

    CERN Multimedia

    2003-01-01

    General and Professional English Courses The next session will take place: from 03 March to 28 June 2003 (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 Mrs. Benz: tel.73127 or Mr. Liptow: tel.72957. Writing Professional Documents in English This course is designed for people with a good level of spoken English. Duration: 20 hours (2 hours a week) Price: 440 CHF (for 8 students) For registration and further information, please consult our Web pages: http://cern.ch/Training or contact Mrs. Tessa Osborne: Tessa.Osborne@cern. 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, rol...

  12. Effects of cochlear-implant pulse rate and inter-channel timing on channel interactions and thresholds

    Science.gov (United States)

    Middlebrooks, John C.

    2004-07-01

    Interactions among the multiple channels of a cochlear prosthesis limit the number of channels of information that can be transmitted to the brain. This study explored the influence on channel interactions of electrical pulse rates and temporal offsets between channels. Anesthetized guinea pigs were implanted with 2-channel scala-tympani electrode arrays, and spike activity was recorded from the auditory cortex. Channel interactions were quantified as the reduction of the threshold for pulse-train stimulation of the apical channel by sub-threshold stimulation of the basal channel. Pulse rates were 254 or 4069 pulses per second (pps) per channel. Maximum threshold reductions averaged 9.6 dB when channels were stimulated simultaneously. Among nonsimultaneous conditions, threshold reductions at the 254-pps rate were entirely eliminated by a 1966-μs inter-channel offset. When offsets were only 41 to 123 μs, however, maximum threshold shifts averaged 3.1 dB, which was comparable to the dynamic ranges of cortical neurons in this experimental preparation. Threshold reductions at 4069 pps averaged up to 1.3 dB greater than at 254 pps, which raises some concern in regard to high-pulse-rate speech processors. Thresholds for various paired-pulse stimuli, pulse rates, and pulse-train durations were measured to test possible mechanisms of temporal integration.

  13. Generation of pulsed ion beams by an inductive storage pulsed power generator

    Science.gov (United States)

    Katsuki, Sunao; Akiyama, Hidenori; Maeda, Sadao

    1990-10-01

    A pulsed power generator by an inductive energy storage system is extremely compact and light in comparison with a conventional pulsed power generator, which consists of a Marx bank and a water pulse forming line. A compact and light pulse power generator is applied to the generation of pulsed ion beams. A thin copper fuse is used an an opening switch, which is necessary in the inductive storage pulsed power generator. A magnetically insulated diode is used for the generation of ion beams. The pulsed ion beams are successfully generated by the inductive storage pulsed power generator for the first time.

  14. Cylindrically Polarized Nondiffracting Optical Pulses

    CERN Document Server

    Ornigotti, Marco; Szameit, Alexander

    2016-01-01

    We extend the concept of radially and azimuthally polarized optical beams to the polychromatic domain by introducing cylindrically polarized nondiffracting optical pulses. In particular, we discuss in detail the case of cylindrically polarized X-waves, both in the paraxial and nonparaxial regime. The explicit expressions for the electric and magnetic fields of cylindrically polarized X-waves is also reported.

  15. Nonparametric estimation of ultrasound pulses

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Leeman, Sidney

    1994-01-01

    An algorithm for nonparametric estimation of 1D ultrasound pulses in echo sequences from human tissues is derived. The technique is a variation of the homomorphic filtering technique using the real cepstrum, and the underlying basis of the method is explained. The algorithm exploits a priori...

  16. Wave equations for pulse propagation

    Science.gov (United States)

    Shore, B. W.

    1987-06-01

    Theoretical discussions of the propagation of pulses of laser radiation through atomic or molecular vapor rely on a number of traditional approximations for idealizing the radiation and the molecules, and for quantifying their mutual interaction by various equations of propagation (for the radiation) and excitation (for the molecules). In treating short-pulse phenomena it is essential to consider coherent excitation phenomena of the sort that is manifest in Rabi oscillations of atomic or molecular populations. Such processes are not adequately treated by rate equations for excitation nor by rate equations for radiation. As part of a more comprehensive treatment of the coupled equations that describe propagation of short pulses, this memo presents background discussion of the equations that describe the field. This memo discusses the origin, in Maxwell's equations, of the wave equation used in the description of pulse propagation. It notes the separation into lamellar and solenoidal (or longitudinal and transverse) and positive and negative frequency parts. It mentions the possibility of separating the polarization field into linear and nonlinear parts, in order to define a susceptibility or index of refraction and, from these, a phase and group velocity.

  17. All about Heart Rate (Pulse)

    Science.gov (United States)

    ... get a picture of your health. Learn more: Blood Pressure Vs. Heart Rate Target Heart Rate Arrhythmias (abnormal heart rhythms) This ... Healthy 6 What are the Symptoms of High Blood Pressure? 7 All About Heart Rate (Pulse) 8 Warning Signs of a Heart Attack ...

  18. Atomic collisions involving pulsed positrons

    DEFF Research Database (Denmark)

    Merrison, J. P.; Bluhme, H.; Field, D.

    2000-01-01

    Conventional slow positron beams have been widely and profitably used to study atomic collisions and have been instrumental in understanding the dynamics of ionization. The next generation of positron atomic collision studies are possible with the use of charged particle traps. Not only can large...... of accelerators for producing intense positron pulses will be discussed in the context of atomic physics experiments....

  19. Ptychographic reconstruction of attosecond pulses

    CERN Document Server

    Lucchini, M; Ludwig, A; Gallmann, L; Keller, U; Feurer, T

    2015-01-01

    We demonstrate a new attosecond pulse reconstruction modality which uses an algorithm that is derived from ptychography. In contrast to other methods, energy and delay sampling are not correlated, and as a result, the number of electron spectra to record is considerably smaller. Together with the robust algorithm, this leads to a more precise and fast convergence of the reconstruction.

  20. CSR Pulsed Switching Power Supplies

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In 2001, CSR power supply system made a great progress. Three prototypes were designed for CSR quadruple and correct magnet. Three different companies provided the three prototypes, but the same circuit-chopper were employed. The simplified diagram is showed in Fig.1. All pulsed switching power supply prototypes were tested successfully before the end of 2001.

  1. Generation of frequency-chirped optical pulses with FELIX

    Science.gov (United States)

    Knippels, G. M. H.; van der Meer, A. F. G.; Mols, R. F. X. A. M.; Oepts, D.; van Amersfoort, P. W.

    1996-02-01

    By ramping the energy of the electron beam on a microsecond timescale, a frequency chirp on a picosecond timescale has been induced. The results of such an experiment are discussed as well as the results of an external pulse chirping experiment. Furthermore, the output of FELIX under normal operating conditions is investigated. For the first time a detailed series of measurements of the evolution of the optical micropulse into a train of subpulses is made when FELIX operates in the limit-cycle mode.

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

    Science.gov (United States)

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

    2003-12-01

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

  3. Knowledge of pulse oximetry among medical and nursing staff

    Directory of Open Access Journals (Sweden)

    Dimitrios Kosmidis

    2007-04-01

    Full Text Available The pulse oximetry is a widely used non invasive method for monitoring the arterial oxygenation. The doctors and the nurses are persons which are in charge for right interpretation of measurements, receiving suitable interventions for the management of patients. Aim: To assess nurses' and doctors' knowledge of pulse oximetry and identify training needs. Material and method: Participants in this study were 376 doctors and nurses from critical and general care settings in seven hospitals in Greece. The data collection was done through a self-administered questionnaire. Frequency of use, critical care experience, and opinions about education needs were included in demographic data. The knowledge test consisted of a 15 item, multiple-choice questionnaire, designed by researchers based on international bibliography. Results: A 70,7% of participants, use pulse oximeter often and 66,3% consider that is very useful in daily clinical practice. 83,7% didn't have some type of past education while more than 81,4% believes that they need further education. The average score for all (on a 15-point scale was 8,5. Ιn particular, the average score for each team had as follows: 10,5±2,7 for the specialized doctors, 9,6±3,1 for residents, 7,8±3,3 for the nurses and 7,4±3,4 for the nurse assistants. Low percentages of right answers were observed mainly in the questions about principles on which the pulse oximetry are based, clinical application and limitations, as well as normal ranges. Conclusion: The comprehension of pulse oximetry is insufficient, mainly in the nursing staff while totally is observed the need for further education.

  4. ACADEMIC TRAINING

    CERN Multimedia

    Françoise Benz

    2002-01-01

    25, 26, 27, 28 February and 1st March from 11.00 to 12.00 hrs - Auditorium, bldg. 500 LECTURE SERIES Neutrino masses and oscillations by A. de Rujula / CERN-TH This course will not cover its subject in the customary way. The emphasis will be on the simple theoretical concepts (helicity, handedness, chirality, Majorana masses) which are obscure in most of the literature, and on the quantum mechanics of oscillations, that ALL books get wrong. Which, hopefully, will not deter me from discussing some of the most interesting results from the labs and from the cosmos. Academic Training Françoise Benz Secretariat Tel. 73127 francoise.benz@cern.ch

  5. English training

    CERN Multimedia

    2003-01-01

    You have a good level of English BUT... You still need to improve your speaking or You have problems writing professional documents Would you like to work in a small group on either of these areas? Then, the following courses are for you! Writing Professional Documents in English The aim of the course is for students to improve their professional writing. Participants will work on technical, scientific or administrative documents depending on the needs of the group. Duration: 20 hours (2 hours a week) Price: 440 CHF (for 8 students) Oral Expression The emphasis will be on oral expression with necessary feed-back. Speaking activities will include discussions, meeting simulations, role-plays etc. Duration: 20 hours (2 hours a week) Price: 440 CHF (for 8 students) For registration and further information, please consult our Web pages: http://cern.ch/Training or contact Mr. Liptow: tel. 72957 / Mrs. Tessa Osborne: Tessa.Osborne@cern.ch.

  6. English Training

    CERN Multimedia

    2003-01-01

    You have a good level of English BUT... You still need to improve your speaking or You have problems writing professional documents Would you like to work in a small group on either of these areas? Then, the following courses are for you! Writing Professional Documents in English The aim of the course is for students to improve their professional writing. Participants will work on technical, scientific or administrative documents depending on the needs of the group. Duration: 20 hours (2 hours a week) Price: 440 CHF (for 8 students) Oral Expression The emphasis will be on oral expression with necessary feed-back. Speaking activities will include discussions, meeting simulations, role-plays etc. Duration: 20 hours (2 hours a week) Price: 440 CHF (for 8 students) For registration and further information, please consult our Web pages: http://cern.ch/Training or contact Mr. Liptow: tel. 72957 / Mrs. Tessa Osborne: Tessa.Osborne@cern.ch.

  7. Temporal resolution beyond the average pulse duration in shaped noisy-pulse transient absorption spectroscopy.

    Science.gov (United States)

    Meyer, Kristina; Müller, Niklas; Liu, Zuoye; Pfeifer, Thomas

    2016-12-20

    In time-resolved spectroscopy, it is a widespread belief that the temporal resolution is determined by the laser pulse duration. Recently, it was observed and shown that partially coherent laser pulses as they are provided by free-electron-laser (FEL) sources offer an alternative route to reach a temporal resolution below the average pulse duration. Here, we demonstrate the generation of partially coherent light in the laboratory like we observe it at FELs. We present the successful implementation of such statistically fluctuating pulses by using the pulse-shaping technique. These pulses exhibit an average pulse duration about 10 times larger than their bandwidth limit. The shaped pulses are then applied to transient-absorption measurements in the dye IR144. Despite the noisy characteristics of the laser pulses, features in the measured absorption spectra occurring on time scales much faster than the average pulse duration are resolved, thus proving the universality of the described noisy-pulse concept.

  8. Cryosurgery with pulsed electric fields.

    Science.gov (United States)

    Daniels, Charlotte S; Rubinsky, Boris

    2011-01-01

    This study explores the hypothesis that combining the minimally invasive surgical techniques of cryosurgery and pulsed electric fields will eliminate some of the major disadvantages of these techniques while retaining their advantages. Cryosurgery, tissue ablation by freezing, is a well-established minimally invasive surgical technique. One disadvantage of cryosurgery concerns the mechanism of cell death; cells at high subzero temperature on the outer rim of the frozen lesion can survive. Pulsed electric fields (PEF) are another minimally invasive surgical technique in which high strength and very rapid electric pulses are delivered across cells to permeabilize the cell membrane for applications such as gene delivery, electrochemotherapy and irreversible electroporation. The very short time scale of the electric pulses is disadvantageous because it does not facilitate real time control over the procedure. We hypothesize that applying the electric pulses during the cryosurgical procedure in such a way that the electric field vector is parallel to the heat flux vector will have the effect of confining the electric fields to the frozen/cold region of tissue, thereby ablating the cells that survive freezing while facilitating controlled use of the PEF in the cold confined region. A finite element analysis of the electric field and heat conduction equations during simultaneous tissue treatment with cryosurgery and PEF (cryosurgery/PEF) was used to study the effect of tissue freezing on electric fields. The study yielded motivating results. Because of decreased electrical conductivity in the frozen/cooled tissue, it experienced temperature induced magnified electric fields in comparison to PEF delivered to the unfrozen tissue control. This suggests that freezing/cooling confines and magnifies the electric fields to those regions; a targeting capability unattainable in traditional PEF. This analysis shows how temperature induced magnified and focused PEFs could be used to

  9. Cryosurgery with pulsed electric fields.

    Directory of Open Access Journals (Sweden)

    Charlotte S Daniels

    Full Text Available This study explores the hypothesis that combining the minimally invasive surgical techniques of cryosurgery and pulsed electric fields will eliminate some of the major disadvantages of these techniques while retaining their advantages. Cryosurgery, tissue ablation by freezing, is a well-established minimally invasive surgical technique. One disadvantage of cryosurgery concerns the mechanism of cell death; cells at high subzero temperature on the outer rim of the frozen lesion can survive. Pulsed electric fields (PEF are another minimally invasive surgical technique in which high strength and very rapid electric pulses are delivered across cells to permeabilize the cell membrane for applications such as gene delivery, electrochemotherapy and irreversible electroporation. The very short time scale of the electric pulses is disadvantageous because it does not facilitate real time control over the procedure. We hypothesize that applying the electric pulses during the cryosurgical procedure in such a way that the electric field vector is parallel to the heat flux vector will have the effect of confining the electric fields to the frozen/cold region of tissue, thereby ablating the cells that survive freezing while facilitating controlled use of the PEF in the cold confined region. A finite element analysis of the electric field and heat conduction equations during simultaneous tissue treatment with cryosurgery and PEF (cryosurgery/PEF was used to study the effect of tissue freezing on electric fields. The study yielded motivating results. Because of decreased electrical conductivity in the frozen/cooled tissue, it experienced temperature induced magnified electric fields in comparison to PEF delivered to the unfrozen tissue control. This suggests that freezing/cooling confines and magnifies the electric fields to those regions; a targeting capability unattainable in traditional PEF. This analysis shows how temperature induced magnified and focused

  10. Cryosurgery with Pulsed Electric Fields

    Science.gov (United States)

    Daniels, Charlotte S.; Rubinsky, Boris

    2011-01-01

    This study explores the hypothesis that combining the minimally invasive surgical techniques of cryosurgery and pulsed electric fields will eliminate some of the major disadvantages of these techniques while retaining their advantages. Cryosurgery, tissue ablation by freezing, is a well-established minimally invasive surgical technique. One disadvantage of cryosurgery concerns the mechanism of cell death; cells at high subzero temperature on the outer rim of the frozen lesion can survive. Pulsed electric fields (PEF) are another minimally invasive surgical technique in which high strength and very rapid electric pulses are delivered across cells to permeabilize the cell membrane for applications such as gene delivery, electrochemotherapy and irreversible electroporation. The very short time scale of the electric pulses is disadvantageous because it does not facilitate real time control over the procedure. We hypothesize that applying the electric pulses during the cryosurgical procedure in such a way that the electric field vector is parallel to the heat flux vector will have the effect of confining the electric fields to the frozen/cold region of tissue, thereby ablating the cells that survive freezing while facilitating controlled use of the PEF in the cold confined region. A finite element analysis of the electric field and heat conduction equations during simultaneous tissue treatment with cryosurgery and PEF (cryosurgery/PEF) was used to study the effect of tissue freezing on electric fields. The study yielded motivating results. Because of decreased electrical conductivity in the frozen/cooled tissue, it experienced temperature induced magnified electric fields in comparison to PEF delivered to the unfrozen tissue control. This suggests that freezing/cooling confines and magnifies the electric fields to those regions; a targeting capability unattainable in traditional PEF. This analysis shows how temperature induced magnified and focused PEFs could be used to

  11. Wave equations for pulse propagation

    Energy Technology Data Exchange (ETDEWEB)

    Shore, B.W.

    1987-06-24

    Theoretical discussions of the propagation of pulses of laser radiation through atomic or molecular vapor rely on a number of traditional approximations for idealizing the radiation and the molecules, and for quantifying their mutual interaction by various equations of propagation (for the radiation) and excitation (for the molecules). In treating short-pulse phenomena it is essential to consider coherent excitation phenomena of the sort that is manifest in Rabi oscillations of atomic or molecular populations. Such processes are not adequately treated by rate equations for excitation nor by rate equations for radiation. As part of a more comprehensive treatment of the coupled equations that describe propagation of short pulses, this memo presents background discussion of the equations that describe the field. This memo discusses the origin, in Maxwell's equations, of the wave equation used in the description of pulse propagation. It notes the separation into lamellar and solenoidal (or longitudinal and transverse) and positive and negative frequency parts. It mentions the possibility of separating the polarization field into linear and nonlinear parts, in order to define a susceptibility or index of refraction and, from these, a phase and group velocity. The memo discusses various ways of characterizing the polarization characteristics of plane waves, that is, of parameterizing a transverse unit vector, such as the Jones vector, the Stokes vector, and the Poincare sphere. It discusses the connection between macroscopically defined quantities, such as the intensity or, more generally, the Stokes parameters, and microscopic field amplitudes. The material presented here is a portion of a more extensive treatment of propagation to be presented separately. The equations presented here have been described in various books and articles. They are collected here as a summary and review of theory needed when treating pulse propagation.

  12. Variation associated with measurement of retinal vessel diameters at different points in the pulse cycle

    Science.gov (United States)

    Knudtson, M D; Klein, B E K; Klein, R; Wong, T Y; Hubbard, L D; Lee, K E; Meuer, S M; Bulla, C P

    2004-01-01

    Background/aims: To assess the variability in retinal vessel measurements at different points in the pulse cycle. Methods: A healthy white male aged 19 years had 30 digitised images taken at three distinct points in the pulse cycle over a one hour period. A pulse synchronised ear clip trigger device was used to capture images at the desired point in the pulse cycle. Two trained graders measured the retinal vessel diameter of one large arteriole, one large venule, one small arteriole, and one small venule 10 times in each of these 30 images. Results: Within an image, variability was similar between graders, pulse point, and vessel type. Across images taken at the same point in the pulse period, the change from the minimum to maximum measurement was between 6% and 17% for arterioles and between 2% and 11% for venules. In addition, measurements of small vessels had greater changes than large vessels and no point in the pulse period was more variable than another. Ignoring pulse cycle increased variability across images in the large venule, but not in the other vessel types. Mixed effect models were fit for each of the vessel types to determine the greatest source of variability. Controlling for pulse point and grader, the largest source of variability for all four vessels measured was across images, accounting for more than 50% of the total variability. Conclusion: Measurements of large retinal venules is generally less variable than measurements of other retinal vessels. After controlling for pulse point and grader, the largest source of variation is across images. Understanding the components of variability in measuring retinal vessels is important as these techniques are applied in epidemiological studies. PMID:14693774

  13. "Training Floors" and "Training Ceilings": Metonyms for Understanding Training Trends

    Science.gov (United States)

    Felstead, Alan; Jewson, Nick

    2014-01-01

    This article outlines a conceptual framework for mapping and understanding training trends. It uses the metonyms of floors and ceilings to distinguish between different types of training configurations. The argument is made that the ups and downs of employer reports of training activity are a crude basis on which to make judgements about the…

  14. Experimental Study of a Pulsed Ytterbium-Doped Fibre Laser with Fast and Slow Saturable Absorbers in a Linear Cavity

    Institute of Scientific and Technical Information of China (English)

    GAN Yu; XIANG Wang-Hua; ZHOU Xiao-Fang; ZHANG Gui-Zhong; ZHANG Bing; WANG Yong-Gang; MA Xiao-Yu

    2006-01-01

    @@ We present a linear-cavity stretched-pulse fibre laser with mode locking by a nonlinear polarization rotation and by semiconductor saturable-absorber mirrors. A Q-switched mode-locking cw train and a mode-locking pulse train are obtained in the experiment. We investigate the effects of the equivalent fast saturable absorber and the slow saturable absorbers in experiment. It is found that neither the nonlinear polarization evolution effect nor a semiconductor saturable absorber mirror is enough to produce the stable cw mode-locking pulses in this experiment. A nonlinear polarization evolution effect controls the cavity loss to literally carve the pulses;semiconductor saturable absorber mirrors provide the self-restarting and maintain the stability of the modelocking operation.

  15. Pulse frequency classification based on BP neural network

    Institute of Scientific and Technical Information of China (English)

    WANG Rui; WANG Xu; YANG Dan; FU Rong

    2006-01-01

    In Traditional Chinese Medicine (TCM), it is an important parameter of the clinic disease diagnosis to analysis the pulse frequency. This article accords to pulse eight major essentials to identify pulse type of the pulse frequency classification based on back-propagation neural networks (BPNN). The pulse frequency classification includes slow pulse, moderate pulse, rapid pulse etc. By feature parameter of the pulse frequency analysis research and establish to identify system of pulse frequency features. The pulse signal from detecting system extracts period, frequency etc feature parameter to compare with standard feature value of pulse type. The result shows that identify-rate attains 92.5% above.

  16. Developing classification indices for Chinese pulse diagnosis

    CERN Document Server

    Shu, Jian-Jun

    2014-01-01

    Aim: To develop classification criteria for Chinese pulse diagnosis and to objectify the ancient diagnostic technique. Methods: Chinese pulse curves are treated as wave signals. Multidimensional variable analysis is performed to provide the best curve fit between the recorded Chinese pulse waveforms and the collective Gamma density functions. Results: Chinese pulses can be recognized quantitatively by the newly-developed four classification indices, that is, the wave length, the relative phase difference, the rate parameter, and the peak ratio. The new quantitative classification not only reduces the dependency of pulse diagnosis on Chinese physician's experience, but also is able to interpret pathological wrist-pulse waveforms more precisely. Conclusions: Traditionally, Chinese physicians use fingertips to feel the wrist-pulses of patients in order to determine their health conditions. The qualitative theory of the Chinese pulse diagnosis is based on the experience of Chinese physicians for thousands of year...

  17. Dispersion compensation in chirped pulse amplification systems

    Science.gov (United States)

    Bayramian, Andrew James; Molander, William A.

    2014-07-15

    A chirped pulse amplification system includes a laser source providing an input laser pulse along an optical path. The input laser pulse is characterized by a first temporal duration. The system also includes a multi-pass pulse stretcher disposed along the optical path. The multi-pass pulse stretcher includes a first set of mirrors operable to receive input light in a first plane and output light in a second plane parallel to the first plane and a first diffraction grating. The pulse stretcher also includes a second set of mirrors operable to receive light diffracted from the first diffraction grating and a second diffraction grating. The pulse stretcher further includes a reflective element operable to reflect light diffracted from the second diffraction grating. The system further includes an amplifier, a pulse compressor, and a passive dispersion compensator disposed along the optical path.

  18. Linear transformer driver for pulse generation

    Science.gov (United States)

    Kim, Alexander A; Mazarakis, Michael G; Sinebryukhov, Vadim A; Volkov, Sergey N; Kondratiev, Sergey S; Alexeenko, Vitaly M; Bayol, Frederic; Demol, Gauthier; Stygar, William A

    2015-04-07

    A linear transformer driver includes at least one ferrite ring positioned to accept a load. The linear transformer driver also includes a first power delivery module that includes a first charge storage devices and a first switch. The first power delivery module sends a first energy in the form of a first pulse to the load. The linear transformer driver also includes a second power delivery module including a second charge storage device and a second switch. The second power delivery module sends a second energy in the form of a second pulse to the load. The second pulse has a frequency that is approximately three times the frequency of the first pulse. The at least one ferrite ring is positioned to force the first pulse and the second pulse to the load by temporarily isolating the first pulse and the second pulse from an electrical ground.

  19. Exact Solutions to Short Pulse Equation

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

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

  20. Linear transformer driver for pulse generation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Alexander A; Mazarakis, Michael G; Sinebryukhov, Vadim A; Volkov, Sergey N; Kondratiev, Sergey S; Alexeenko, Vitaly M; Bayol, Frederic; Demol, Gauthier; Stygar, William A

    2015-04-07

    A linear transformer driver includes at least one ferrite ring positioned to accept a load. The linear transformer driver also includes a first power delivery module that includes a first charge storage devices and a first switch. The first power delivery module sends a first energy in the form of a first pulse to the load. The linear transformer driver also includes a second power delivery module including a second charge storage device and a second switch. The second power delivery module sends a second energy in the form of a second pulse to the load. The second pulse has a frequency that is approximately three times the frequency of the first pulse. The at least one ferrite ring is positioned to force the first pulse and the second pulse to the load by temporarily isolating the first pulse and the second pulse from an electrical ground.

  1. Treatment Pulse Application for Magnetic Stimulation

    Directory of Open Access Journals (Sweden)

    Sun-Seob Choi

    2011-01-01

    Full Text Available Treatment and diagnosis can be made in difficult areas simply by changing the output pulse form of the magnetic stimulation device. However, there is a limitation in the range of treatments and diagnoses of a conventional sinusoidal stimulation treatment pulse because the intensity, width, and form of the pulse must be changed according to the lesion type. This paper reports a multidischarge method, where the stimulation coils were driven in sequence via multiple switching control. The limitation of the existing simple sinusoidal pulse form could be overcome by changing the intensity, width, and form of the pulse. In this study, a new sequential discharge method was proposed to freely alter the pulse width. The output characteristics of the stimulation treatment pulse were examined according to the trigger signal delay applied to the switch at each stage by applying a range of superposition pulses to the magnetic simulation device, which is widely used in industry and medicine.

  2. Nuclear manpower training

    Energy Technology Data Exchange (ETDEWEB)

    Suh, In Suk; Lee, H. Y.; Joe, B. J.; Lee, S. H.; Lee, E. J.; Yoo, B. H.; Seo, K. W.; Lee, W. K.; Jun, H. I.; Yang, K. N.; Kim, Y. J.; Kim, I. H.; Kim, M. Y.; Ju, Y. C.; Hyun, H. Y.; Choi, I. G.; Hong, C. S.; Won, J. Y.; Nam, J. Y.; Lee, H. J.

    1997-01-01

    This report describes the annual results of training courses. the scope and contents are as follows: 1. Regional and interregional training courses 2. Training courses assisted by foreign experts 3. Training courses for nuclear industry personnel 4. Training courses for internal staff-members 5. Training courses under the law. This Nuclear Training Center executed the open-door training courses for 2,400 engineers/scientists from the regulatory body, nuclear industries, research institutes and other related organizations by means of offering 51 training courses during the fiscal year 1996. (author). 23 refs.

  3. First pulse effect self-suppression picosecond regenerative amplifier (Conference Presentation)

    Science.gov (United States)

    Fan, Haitao; Chang, Liang; Zhang, Yi; Yao, Siyi; Lu, Wei; Yang, Xiaohong

    2017-03-01

    First pulse effect, commonly seen in nanosecond cavity-dumped lasers and picosecond regenerative amplifiers, not only leads to degradation of processing quality, but also acts as potential threat to optical switching elements. Several methods have been developed to suppress that effect, including electronic controls, polarization controls, and diffraction controls. We present a new way for first pulse self-suppression without any additional components. By carefully arranging the cavity mirror of a regenerative amplifier, we realized `parasitic lasing like' radiation. When the regenerative amplifier works in `operation ready' status, the parasitic lasing occurs and prevents the gain crystal from saturation. When the regenerative amplifier starts working and amplifying pulses, the first pulse in a pulse train will not get much more gain and energy than pulses following it. As parasitic lasing disappears at the same time, the average output power of the amplifier does not significantly reduce. This cost effective method does not require any additional component. In addition, as it is not polarization dependent, this method is widely suitable for different kinds of regenerative amplifiers. It's the easiest and cheapest way to suppress first pulse effect, to the best of our knowledge.

  4. Characteristics of Preliminary Breakdown Pulses in Positive Ground Flashes during Summer Thunderstorms in Sweden

    Directory of Open Access Journals (Sweden)

    Dalina Johari

    2016-03-01

    Full Text Available This paper presents the characteristics of the preliminary breakdown pulses (PBP in 51 positive ground flashes recorded during 2014 summer thunderstorms in Sweden. Electric field measurements were conducted remotely using a broadband antenna system (up to 100 MHz for a recording length of 1 s with 200 ms trigger time. In the analysis, PBP trains were observed in 86% of the cases. Based on the number of trains preceding the first return stroke, the PBP were classified into single and multiple train PBP. Characteristics of the first PBP train were determined and based on the initial polarity of the pulses, three types of PBP were identified. Characteristics of the subsequent PBP trains in the multiple train PBP were also analyzed and they were compared with the first PBP train. Based on the conceptual charge cloud configuration, we found that the inverted dipole is consistent with our observation. We also found that PBP in positive ground flashes during summer thunderstorms in Sweden are weak since the average ratios of the PBP peak to the first return stroke peak lie only between 0.21 and 0.26. Possible reasons for no detection of PBP and the different types of PBP observed were also discussed.

  5. F-35 Embedded Training

    Science.gov (United States)

    2009-10-01

    from the pilot vehicle interface ( PVI ), which enables weapon and expendable countermeasures employment simulations. From TRAIN mode the pilot can...Scenario Debrief Data Aircraft Data Transfer Device ET Scenarios controlled via TRAIN Mode PVI TRAIN Mode Infrastructure JSF OMS VT Scenario...TRAIN mode from the pilot vehicle interface ( PVI ), which enables weapon and expendable countermeasures employment simulations. From TRAIN mode the

  6. Exawatt-Zettawatt Pulse Generation and Applications

    OpenAIRE

    Mourou, G. A.; Fisch, N. J.; Malkin, V. M.; Toroker, Z.; Khazanov, E. A.; Sergeev, A. M.; TAJIMA, T.

    2011-01-01

    A new amplification method, weaving the three basic compression techniques, Chirped Pulse Amplification (CPA), Optical Parametric Chirped Pulse Amplification (OPCPA) and Plasma Compression by Backward Raman Amplification (BRA) in plasma, is proposed. It is called C3 for Cascaded Conversion Compression. It has the capability to compress with good efficiency kilojoule to megajoule, nanosecond laser pulses into femtosecond pulses, to produce exawatt and beyond peak power. In the future, C3 could...

  7. High Power Picosecond Laser Pulse Recirculation

    Energy Technology Data Exchange (ETDEWEB)

    Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P

    2010-04-12

    We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering based light sources. We demonstrate up to 36x average power enhancement of frequency doubled sub-millijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

  8. High-power picosecond laser pulse recirculation.

    Science.gov (United States)

    Shverdin, M Y; Jovanovic, I; Semenov, V A; Betts, S M; Brown, C; Gibson, D J; Shuttlesworth, R M; Hartemann, F V; Siders, C W; Barty, C P J

    2010-07-01

    We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high-power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering-based light sources. We demonstrate up to 40x average power enhancement of frequency-doubled submillijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

  9. Nonlinear optics with stationary pulses of light

    OpenAIRE

    Andre, A.; Bajcsy, M.; Zibrov, A. S.; Lukin, M. D.

    2004-01-01

    We show that the recently demonstrated technique for generating stationary pulses of light [Nature {\\bf 426}, 638 (2003)] can be extended to localize optical pulses in all three spatial dimensions in a resonant atomic medium. This method can be used to dramatically enhance the nonlinear interaction between weak optical pulses. In particular, we show that an efficient Kerr-like interaction between two pulses can be implemented as a sequence of several purely linear optical processes. The resul...

  10. Chirped Pulse Microwave Spectroscopy in Pulsed Uniform Supersonic Flows

    Science.gov (United States)

    Abeysekera, Chamara; Oldham, James; Prozument, Kirill; Joalland, Baptiste; Park, Barratt; Field, Robert W.; Sims, Ian; Suits, Arthur; Zack, Lindsay

    2014-06-01

    We present preliminary results describing the development of a new instrument that combines two powerful techniques: Chirped Pulse-Fourier Transform MicroWave (CP-FTMW) spectroscopy and pulsed uniform supersonic flows. It promises a nearly universal detection method that can deliver quantitative isomer, conformer, and vibrational level specific detection, characterization of unstable reaction products and intermediates and perform unique spectroscopic, kinetics and dynamics measurements. We have constructed a new high-power K_a-band, 26-40 GHz, chirped pulse spectrometer with sub-MHz resolution, analogous to the revolutionary CP-FTMW spectroscopic technique developed in the Pate group at University of Virginia. In order to study smaller molecules, the E-band, 60-90 GHz, CP capability was added to our spectrometer. A novel strategy for generating uniform supersonic flow through a Laval nozzle is introduced. High throughput pulsed piezo-valve is used to produce cold (30 K) uniform flow with large volumes of 150 cm^3 and densities of 1014 molecules/cm3 with modest pumping facilities. The uniform flow conditions for a variety of noble gases extend as far as 20 cm from the Laval nozzle and a single compound turbo-molecular pump maintains the operating pressure. Two competing design considerations are critical to the performance of the system: a low temperature flow is needed to maximize the population difference between rotational levels, and high gas number densities are needed to ensure rapid cooling to achieve the uniform flow conditions. At the same time, collision times shorter than the chirp duration will give inaccurate intensities and reduced signal levels due to collisional dephasing of free induction decay. Details of the instrument and future directions and challenges will be discussed.

  11. LASER PERCUSSION DRILLING ON THIN MILD STEEL SHEET BASED ON THE DUTY CYCLE VARIATIONS OF A PULSED RF SLAB CO2 LASER

    OpenAIRE

    R. CORTES; Villagomez, R; Lopez, R.; V. Coello

    2008-01-01

    In this work, the influence of laser pulse trains on thin mild steel sheet blades is investigated. The method is based on varying the duty cycle (DC) of a pulsed RF slab CO2 laser during the process of laser percussion drilling. Here, an experimental methodology to correlate laser parameters and their effects on the characteristics of the melting material ejected was carried out. In the experiments, the interaction time such that of 5%, 10%, and 15% DC were considered for the pulse trains. Re...

  12. Spaced cognitive training promotes training transfer

    Directory of Open Access Journals (Sweden)

    Zuowei eWang

    2014-04-01

    Full Text Available Cognitive training studies yield wildly inconsistent results. One dimension on which studies vary is the scheduling of training sessions (Morrison & Chein, 2011. In this study, we systematically address whether or not spacing of practice influences training and transfer. We randomly assigned 115 fifth grade children to an active control group or one of four training groups who received working memory training based on a running span task (Zhao et al., 2011. All groups received the same total amount of training: 20 sessions of training with 60 trials for an average of 20 minutes per session. The training was spread across 2 days, 5 days, 10 days, or 20 days. The active control group received 20-minute sessions of math instruction for 20 sessions. Before and after training participants in all five groups performed a single transfer test that assessed fluid intelligence, the Raven's Progressive Matrices Test. Overall, participants in all four training groups improved significantly on the training task (at least partially, as reflected by increased speed. More importantly, the only training group to show significant improvement on the Raven's was the group who had the greatest amount of spacing (20 days group during training and improvement in this group was significantly higher than that of the control group.

  13. Spaced cognitive training promotes training transfer.

    Science.gov (United States)

    Wang, Zuowei; Zhou, Renlai; Shah, Priti

    2014-01-01

    Cognitive training studies yield wildly inconsistent results. One dimension on which studies vary is the scheduling of training sessions (Morrison and Chein, 2011). In this study, we systematically address whether or not spacing of practice influences training and transfer. We randomly assigned 115 fifth grade children to an active control group or one of four training groups who received working memory training based on a "running span" task (Zhao et al., 2011). All groups received the same total amount of training: 20 sessions of training with 60 trials for an average of 20 min per session. The training was spread across 2, 5, 10, or 20 days. The active control group received 20-min sessions of math instruction for 20 sessions. Before and after training participants in all five groups performed a single transfer test that assessed fluid intelligence, the Raven's Progressive Matrices Test. Overall, participants in all four training groups improved significantly on the training task (at least partially), as reflected by increased speed. More importantly, the only training group to show significant improvement on the Raven's was the group who had the greatest amount of spacing (20 days group) during training and improvement in this group was significantly higher than that of the control group.

  14. Third Harmonic Imaging using a Pulse Inversion

    DEFF Research Database (Denmark)

    Rasmussen, Joachim; Du, Yigang; Jensen, Jørgen Arendt

    2011-01-01

    The pulse inversion (PI) technique can be utilized to separate and enhance harmonic components of a waveform for tissue harmonic imaging. While most ultrasound systems can perform pulse inversion, only few image the 3rd harmonic component. PI pulse subtraction can isolate and enhance the 3rd...

  15. Pulse crop diseases in the Pacific Northwest

    Science.gov (United States)

    The United Nations declared that 2016 is the International Year of Pulses (IYP). This UN declaration of IYP will certainly increase awareness of pulses and likely position pulses as a primary source of protein and other essential nutrients for human diets. The US Pacific Northwest region (Idaho, Or...

  16. REFLECTANCE PULSE OXIMETRY IN FETAL LAMBS

    NARCIS (Netherlands)

    DASSEL, AC; GRAAFF, R; AARNOUDSE, JG; ELSTRODT, JM; HEIDA, P; KOELINK, MH; DEMUL, FF; GREVE, J

    1992-01-01

    Transmission pulse oximetry is used for monitoring in many clinical settings. However, for fetal monitoring during labor and in situations with poor peripheral perfusion, transmission pulse oximetry cannot be used. Therefore, we developed a reflectance pulse oximeter, which uses the relative intensi

  17. Hg-Arc Lamp, Pulse Excitation.

    Science.gov (United States)

    1986-09-01

    References 1. "Pulsed Mercury Capillary Lamps .,"P. Dal Pozzo, R. Polloni, and 0. Svelto , J. Appi. Phys. 6, 342 (1975). * 2. "Pulsed High-Pressure Mercury...Capillary Lamps .. ,P. Dal Pozzo, R. Polloni, * and 0. Svelto , J. Appi. Phys. 6, 381 (1975). 3. "Characteristics of the Radiation Pulses of Very-High

  18. A self-consistent Maltsev pulse model

    Science.gov (United States)

    Buneman, O.

    1985-04-01

    A self-consistent model for an electron pulse propagating through a plasma is presented. In this model, the charge imbalance between plasma ions, plasma electrons and pulse electrons creates the travelling potential well in which the pulse electrons are trapped.

  19. High speed, high current pulsed driver circuit

    Energy Technology Data Exchange (ETDEWEB)

    Carlen, Christopher R.

    2017-03-21

    Various technologies presented herein relate to driving a LED such that the LED emits short duration pulses of light. This is accomplished by driving the LED with short duration, high amplitude current pulses. When the LED is driven by short duration, high amplitude current pulses, the LED emits light at a greater amplitude compared to when the LED is driven by continuous wave current.

  20. Nonspreading Light Pulses in Photonic Crystals

    OpenAIRE

    Staliunas, K.; Serrat, C.; Herrero, R; Cojocaru, C.; Trull, J.

    2005-01-01

    We investigate propagation of light pulses in photonic crystals in the vicinity of the zero-diffraction point. We show that Gaussian pulses due to nonzero width of their spectrum spread weakly in space and time during the propagation. We also find the family of nonspreading pulses, propagating invariantly in the vicinity of the zero diffraction point of photonic crystals.

  1. Double pulse Thomson scattering system at RTP

    NARCIS (Netherlands)

    Beurskens, M. N. A.; Barth, C. J.; Chu, C.C.; Donne, A. J. H.; Herranz, J. A.; Cardozo, N. J. L.; van der Meiden, H. J.; Pijper, F.J.

    1997-01-01

    In this article a double pulse multiposition Thomson scattering diagnostic, under construction at RTP, is discussed. Light from a double pulsed ruby laser (pulse separation: 10-800 mu s, max. 2x12.5 J) is scattered by the free electrons of the tokamak plasma and relayed to a Littrow polychromator fo

  2. <3> OMEGA pulse-forming network

    CERN Multimedia

    1974-01-01

    Adjustement of the 3 W pulse-forming network of the SPS beam dumping system. When charged at 60 kV, this PFN gives 10 kA, 25 ms current pulses, with oscillations, superimposed on the pulse flat top, of an amplitude of +/- 1 Ka.

  3. Perceptions of European stakeholders of pulse fishing

    NARCIS (Netherlands)

    Kraan, M.L.; Trapman, B.K.; Rasenberg, M.M.M.

    2015-01-01

    This research project examines the concerns and questions of European stakeholders about pulse fishing, in order to assess to what extent the knowledge agenda on pulse fishing covers these issues. To get a first impression of the concerns about pulse fishing, and to get an idea of the stakeholders t

  4. A Study of New Pulse Auscultation System

    Directory of Open Access Journals (Sweden)

    Ying-Yun Chen

    2015-04-01

    Full Text Available This study presents a new type of pulse auscultation system, which uses a condenser microphone to measure pulse sound waves on the wrist, captures the microphone signal for filtering, amplifies the useful signal and outputs it to an oscilloscope in analog form for waveform display and storage and delivers it to a computer to perform a Fast Fourier Transform (FFT and convert the pulse sound waveform into a heartbeat frequency. Furthermore, it also uses an audio signal amplifier to deliver the pulse sound by speaker. The study observed the principles of Traditional Chinese Medicine’s pulsing techniques, where pulse signals at places called “cun”, “guan” and “chi” of the left hand were measured during lifting (100 g, searching (125 g and pressing (150 g actions. Because the system collects the vibration sound caused by the pulse, the sensor itself is not affected by the applied pressure, unlike current pulse piezoelectric sensing instruments, therefore, under any kind of pulsing pressure, it displays pulse changes and waveforms with the same accuracy. We provide an acquired pulse and waveform signal suitable for Chinese Medicine practitioners’ objective pulse diagnosis, thus providing a scientific basis for this Traditional Chinese Medicine practice. This study also presents a novel circuit design using an active filtering method. An operational amplifier with its differential features eliminates the interference from external signals, including the instant high-frequency noise. In addition, the system has the advantages of simple circuitry, cheap cost and high precision.

  5. Isolated sub-10 attosecond pulse generation by a 6-fs driving pulse and a 5-fs subharmonic controlling pulse

    Directory of Open Access Journals (Sweden)

    Yunhui Wang

    2012-06-01

    Full Text Available We theoretically study high-order harmonic generation by quantum path control in a special two-color laser field, which is synthesized by a 6 fs/800 nm fundamental pulse and a weaker 5 fs/1600 nm subharmonic controlling pulse. Single quantum path is selected without optimizing any carrier phase, which not only broadens the harmonic bandwidth to 400 eV, but also enhances the harmonic conversion efficiency in comparison with the short-plus-long scheme, which is based on 5 fs/800 nm driving pulse and 6 fs/1600 nm control pulse. An isolated 8-attosecond pulse is produced with currently available ultrafast laser sources.

  6. Generation of few-cycle terawatt light pulses using optical parametric chirped pulse amplification

    NARCIS (Netherlands)

    Witte, S.; Zinkstok, R.T.; Hogervorst, W.; Eikema, K.S.E.

    2005-01-01

    We demonstrate the generation of 9.8 +/- 0.3 fs laser pulses with a peak power exceeding one terawatt at 30 Hz repetition rate, using optical parametric chirped pulse amplification. The amplifier is pumped by 140 mJ, 60 ps pulses at 532 nm, and amplifies seed pulses from a Ti: Sapphire oscillator to

  7. CW seeded optical parametric amplifier providing wavelength and pulse duration tunable nearly transform limited pulses.

    Science.gov (United States)

    Hädrich, S; Gottschall, T; Rothhardt, J; Limpert, J; Tünnermann, A

    2010-02-01

    An optical parametric amplifier that delivers nearly transform limited pulses is presented. The center wavelength of these pulses can be tuned between 993 nm and 1070 nm and, at the same time, the pulse duration is varied between 206 fs and 650 fs. At the shortest pulse duration the pulse energy was increased up to 7.2 microJ at 50 kHz repetition rate. Variation of the wavelength is achieved by applying a tunable cw seed while the pulse duration can be varied via altering the pump pulse duration. This scheme offers superior flexibility and scaling possibilities.

  8. Development of high-voltage pulse-slicer unit with variable pulse duration for pulse radiolysis system

    Science.gov (United States)

    Upadhyay, J.; Sharma, M. L.; Navathe, C. P.; Toley, M. A.; Shinde, S. J.; Nadkarni, S. A.; Sarkar, S. K.

    2012-02-01

    A high-voltage pulse-slicer unit with variable pulse duration has been developed and integrated with a 7 MeV linear electron accelerator (LINAC) for pulse radiolysis investigation. The pulse-slicer unit provides switching voltage from 1 kV to 10 kV with rise time better than 5 ns. Two MOSFET based 10 kV switches were configured in differential mode to get variable duration pulses. The high-voltage pulse has been applied to the deflecting plates of the LINAC for slicing of electron beam of 2 μs duration. The duration of the electron beam has been varied from 30 ns to 2 μs with the optimized pulse amplitude of 7 kV to get corresponding radiation doses from 6 Gy to 167 Gy.

  9. Training the Sales Neophyte

    Science.gov (United States)

    Harris, Clyde E., Jr.

    1975-01-01

    The article reappraises initial sales training and presents a program emphasizing objectives, responsibility for training, program content, and teaching techniques. Formal Initial Responsive Sales Training System (FIRSTS) is the name of the program explored and evaluated. (Author/MW)

  10. Toilet training tips

    Science.gov (United States)

    Potty training ... show signs that they are ready for toilet training between ages 18 and 30 months. Before 18 ... way that she is ready to start toilet training. Children are ready when they: Show interest in ...

  11. Language training

    CERN Multimedia

    Françoise Benz

    2005-01-01

    General and Professional English Courses The next session will take place: from end of September 2005 to middle of February 2006 (2/ 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 in English The next session will take place from end of September to December 2005. 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 a maximum of 10 participants in a class. Speaking activities will include discussions, meeting simulations, role-plays etc. depending on the needs of the students. Duration: 20 hours Price: 440 CHF (for a minimum of 8 students) Writing Professional Documents in English The next session will take place from end of September 2005 to middle of Feb...

  12. Language training

    CERN Multimedia

    2007-01-01

    General and Professional English Courses The next session will take place from 26 February or 5 March to end of June 2007 (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 Françoise Benz, tel. 73127. Oral Expression The next session will take place from 26 February or 5 March to end of June 2007 (1/2 weeks break at Easter). 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 a maximum of 10 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 26 February or...

  13. Language training

    CERN Multimedia

    Françoise Benz

    2005-01-01

    General and Professional English Courses The next session will take place: from end of September 2005 to middle of February 2006 (2/ 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 in English The next session will take place from end of September to December 2005. 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 a maximum of 10 participants in a class. Speaking activities will include discussions, meeting simulations, role-plays etc. depending on the needs of the students. Duration: 20 hours Price: 440 CHF (for a minimum of 8 students) Writing Professional Documents in English The next session will take place from end of September 2005 to middle of Feb...

  14. Language training

    CERN Multimedia

    2007-01-01

    General and Professional English Courses The next session will take place: from 26 February or 5 March to end of June 2007 (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 Françoise Benz, tel. 73127. Oral Expression The next session will take place from 26 February or 5 March to end of June 2007 (1/2 weeks break at Easter). 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 a maximum of 10 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 26 February or 5 M...

  15. Language Training

    CERN Multimedia

    Françoise Benz

    2005-01-01

    General and Professional English Courses The next session will take place: from end of September 2005 to middle of February 2006 (2/ 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 in English The next session will take place from end of September to December 2005. 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 a maximum of 10 participants in a class. Speaking activities will include discussions, meeting simulations, role-plays etc. depending on the needs of the students. Duration: 20 hours Price: 440 CHF (for a minimum of 8 students) Writing Professional Documents in English The next session will take place from end of September 2005 to middle of Febr...

  16. Language training

    CERN Multimedia

    2006-01-01

    General and Professional English Courses The next session will take place from beginning of October 2006 to beginning of February 2007 (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 Tessa Osborne, tel.16 23 40. Oral Expression The next session will take place from beginning of October 2006 to beginning of February 2007 (3 weeks break at Christmas).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 a maximum of 10 participants in a class. Speaking activities will include discussions, meeting simulations, role-plays etc., depending on the needs of the students. Duration: 30 hours (2 hours a week) Price: 660 CHF (for a minimum of 8 students). Writing Professional Documents in English The next ses...

  17. Unsplit bipolar pulse forming line

    Science.gov (United States)

    Rhodes, Mark A.

    2011-05-24

    A bipolar pulse forming transmission line module and system for linear induction accelerators having first, second, third, and fourth planar conductors which form a sequentially arranged interleaved stack having opposing first and second ends, with dielectric layers between the conductors. The first and second planar conductors are connected to each other at the first end, and the first and fourth planar conductors are connected to each other at the second end via a shorting plate. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short at the first end a high voltage from the third planar conductor to the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.

  18. Pulsed Power Driven Fusion Energy

    Energy Technology Data Exchange (ETDEWEB)

    SLUTZ,STEPHEN A.

    1999-11-22

    Pulsed power is a robust and inexpensive technology for obtaining high powers. Considerable progress has been made on developing light ion beams as a means of transporting this power to inertial fusion capsules. However, further progress is hampered by the lack of an adequate ion source. Alternatively, z-pinches can efficiently convert pulsed power into thermal radiation, which can be used to drive an inertial fusion capsule. However, a z-pinch driven fusion explosion will destroy a portion of the transmission line that delivers the electrical power to the z-pinch. They investigate several options for providing standoff for z-pinch driven fusion. Recyclable Transmission Lines (RTLs) appear to be the most promising approach.

  19. Acoustic emission linear pulse holography

    Science.gov (United States)

    Collins, H.D.; Busse, L.J.; Lemon, D.K.

    1983-10-25

    This device relates to the concept of and means for performing Acoustic Emission Linear Pulse Holography, which combines the advantages of linear holographic imaging and Acoustic Emission into a single non-destructive inspection system. This unique system produces a chronological, linear holographic image of a flaw by utilizing the acoustic energy emitted during crack growth. The innovation is the concept of utilizing the crack-generated acoustic emission energy to generate a chronological series of images of a growing crack by applying linear, pulse holographic processing to the acoustic emission data. The process is implemented by placing on a structure an array of piezoelectric sensors (typically 16 or 32 of them) near the defect location. A reference sensor is placed between the defect and the array.

  20. Pulsed DEMO design assessment studies

    CERN Document Server

    Todd, T N

    2013-01-01

    Now that ITER is under construction, interest is increasing in the specification and design of the successor machine, a Demonstration Power Plant (DEMO), which in Europe is coordinated by the EFDA Power Plant Physics and Technology programme. This paper summarises the work carried out for EFDA in 2011-2012 on design issues pertinent to a pulsed version of DEMO, intended to be implemented with little or no extrapolation of technology available today. The work was carried out by the Euratom Fusion Associations CCFE, CEA, CRPP, ENEA and KIT, and in addition to a review of recent relevant literature addressed systems code analyses (pulse length vs. size), erosion of plasma facing components, thermomechanical fatigue in the blanket and first wall, a range of energy storage issues, and fatigue life improvements in Nb3Sn CICC superconductors.