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Sample records for pulse duration measurements

  1. PULSE DURATION LENGTHENER

    DOEpatents

    Aiken, W.R.

    1958-02-01

    This patent pertains to pulse modifying apparatus and, more particularly, describes a device to provide a rise time and time base expander for signal pulses having a very short duration. The basic element of the device is a vacuum tube comprising a charged particie beam, grid control means, an accelerating electrode, a drift tube, and a collector electrode. As the short duration input pulse modulates the particle beam through the grid control means, the voltage between the drift tube and accelerating electrode is caused to vary, whereby the output signal from the collector is a pulse having longer rise time, expanded duration and proportionate characteristics of the original pulse. The invention is particuiarly useful where subsequent pulse circultry does not have the frequency bandwidth to handle the short duration pulse without distorting it.

  2. Quasi-real-time photon pulse duration measurement by analysis of FEL radiation spectra.

    PubMed

    Engel, Robin; Düsterer, Stefan; Brenner, Günter; Teubner, Ulrich

    2016-01-01

    For photon diagnostics at free-electron lasers (FELs), the determination of the photon pulse duration is an important challenge and a complex task. This is especially true for SASE FELs with strongly fluctuating pulse parameters. However, most techniques require an extensive experimental setup, data acquisition and evaluation time, limiting the usability in all-day operation. In contrast, the presented work uses an existing approach based on the analysis of statistical properties of measured SASE FEL spectra and implements it as a software tool, integrated in FLASH's data acquisition system. This allows the calculation of the average pulse durations from a set of measured spectral distributions with only seconds of delay, whenever high-resolution spectra are recorded. PMID:26698053

  3. Quasi-real-time photon pulse duration measurement by analysis of FEL radiation spectra

    PubMed Central

    Engel, Robin; Düsterer, Stefan; Brenner, Günter; Teubner, Ulrich

    2016-01-01

    For photon diagnostics at free-electron lasers (FELs), the determination of the photon pulse duration is an important challenge and a complex task. This is especially true for SASE FELs with strongly fluctuating pulse parameters. However, most techniques require an extensive experimental setup, data acquisition and evaluation time, limiting the usability in all-day operation. In contrast, the presented work uses an existing approach based on the analysis of statistical properties of measured SASE FEL spectra and implements it as a software tool, integrated in FLASH’s data acquisition system. This allows the calculation of the average pulse durations from a set of measured spectral distributions with only seconds of delay, whenever high-resolution spectra are recorded. PMID:26698053

  4. Optimization of Pulsed-DEER Measurements for Gd-Based Labels: Choice of Operational Frequencies, Pulse Durations and Positions, and Temperature

    SciTech Connect

    Raitsimring, A.; Astashkin, A. V.; Enemark, J. H.; Kaminker, I.; Goldfarb, D.; Walter, E. D.; Song, Y.; Meade, T. J.

    2012-12-29

    In this work, the experimental conditions and parameters necessary to optimize the long-distance (≥ 60 Å) Double Electron-Electron Resonance (DEER) measurements of biomacromolecules labeled with Gd(III) tags are analyzed. The specific parameters discussed are the temperature, microwave band, the separation between the pumping and observation frequencies, pulse train repetition rate, pulse durations and pulse positioning in the electron paramagnetic resonance spectrum. It was found that: (i) in optimized DEER measurements, the observation pulses have to be applied at the maximum of the EPR spectrum; (ii) the optimal temperature range for Ka-band measurements is 14-17 K, while in W-band the optimal temperatures are between 6-9 K; (iii) W-band is preferable to Ka-band for DEER measurements. Recent achievements and the conditions necessary for short-distance measurements (<15 Å) are also briefly discussed.

  5. Effects of pulse duration on magnetostimulation thresholds

    SciTech Connect

    Saritas, Emine U.; Goodwill, Patrick W.; Conolly, Steven M.

    2015-06-15

    Purpose: Medical imaging techniques such as magnetic resonance imaging and magnetic particle imaging (MPI) utilize time-varying magnetic fields that are subject to magnetostimulation limits, which often limit the speed of the imaging process. Various human-subject experiments have studied the amplitude and frequency dependence of these thresholds for gradient or homogeneous magnetic fields. Another contributing factor was shown to be number of cycles in a magnetic pulse, where the thresholds decreased with longer pulses. The latter result was demonstrated on two subjects only, at a single frequency of 1.27 kHz. Hence, whether the observed effect was due to the number of cycles or due to the pulse duration was not specified. In addition, a gradient-type field was utilized; hence, whether the same phenomenon applies to homogeneous magnetic fields remained unknown. Here, the authors investigate the pulse duration dependence of magnetostimulation limits for a 20-fold range of frequencies using homogeneous magnetic fields, such as the ones used for the drive field in MPI. Methods: Magnetostimulation thresholds were measured in the arms of six healthy subjects (age: 27 ± 5 yr). Each experiment comprised testing the thresholds at eight different pulse durations between 2 and 125 ms at a single frequency, which took approximately 30–40 min/subject. A total of 34 experiments were performed at three different frequencies: 1.2, 5.7, and 25.5 kHz. A solenoid coil providing homogeneous magnetic field was used to induce stimulation, and the field amplitude was measured in real time. A pre-emphasis based pulse shaping method was employed to accurately control the pulse durations. Subjects reported stimulation via a mouse click whenever they felt a twitching/tingling sensation. A sigmoid function was fitted to the subject responses to find the threshold at a specific frequency and duration, and the whole procedure was repeated at all relevant frequencies and pulse durations

  6. Investigation of laser temporal pulse duration on Rayleigh scattering

    SciTech Connect

    Nee, T.A.; Roberts, J.R.

    1982-02-01

    Relative Rayleigh-scattering cross sections from nitrogen have been measured for various pulse durations and wavelengths of incident laser radiation. No pulse-duration dependence has been observed for laser pulses as short as 5 ns, and classical theory is found to be still valid over the pulse-width range (5< or =..delta..t< or =110 ns) of our observations.

  7. Note: Measurement of extreme-short current pulse duration of runaway electron beam in atmospheric pressure air

    SciTech Connect

    Tarasenko, V. F.; Rybka, D. V.; Burachenko, A. G.; Lomaev, M. I.; Balzovsky, E. V.

    2012-08-15

    This note reports the time-amplitude characteristic of the supershort avalanche electron beam with up to 20 ps time resolution. For the first time it is shown that the electron beam downstream of small-diameter diaphragms in atmospheric pressure air has a complex structure which depends on the interelectrode gap width and cathode design. With a spherical cathode and collimator the minimum duration at half maximum of the supershort avalanche electron beam current pulse was shown to be {approx}25 ps. The minimum duration at half maximum of one peak in the pulses with two peaks can reach {approx}25 ps too.

  8. Kicking atoms with finite duration pulses

    NASA Astrophysics Data System (ADS)

    Fekete, Julia; Chai, Shijie; Daszuta, Boris; Andersen, Mikkel F.

    2016-05-01

    The atom optics delta-kicked particle is a paradigmatic system for experimental studies of quantum chaos and classical-quantum correspondence. It consists of a cloud of laser cooled atoms exposed to a periodically pulsed standing wave of far off-resonant laser light. A purely quantum phenomena in such systems are quantum resonances which transfers the atoms into a coherent superposition of largely separated momentum states. Using such large momentum transfer ``beamsplitters'' in atom interferometers may have applications in high precision metrology. The growth in momentum separation cannot be maintained indefinitely due to finite laser power. The largest momentum transfer is achieved by violating the usual delta-kick assumption. Therefore we explore the behavior of the atom optics kicked particle with finite pulse duration. We have developed a semi-classical model which shows good agreement with the full quantum description as well as our experiments. Furthermore we have found a simple scaling law that helps to identify optimal parameters for an atom interferometer. We verify this by measurements of the ``Talbot time'' (a measurement of h/m) which together with other well-known constants constitute a measurement of the fine structure constant.

  9. Effect of laser pulse duration in picosecond ultrasonics

    NASA Astrophysics Data System (ADS)

    Dehoux, T.; Perton, M.; Chigarev, N.; Rossignol, C.; Rampnoux, J.-M.; Audoin, B.

    2006-09-01

    An optical grating has been introduced in a picosecond ultrasonics experiment, in order to vary continuously the duration of the laser beam pulse from 0.1to150ps. The evolution of the measured signal has been observed and analyzed through the comparison with a theoretical approach based on a two-temperature model. The latter allows matching the acoustic echoes together with the thermal background and the coincidence peak, for each pulse duration and at any time scale. The broadening of the acoustic echoes and the disappearing of its Brillouin component, along with the diminishing of the thermal coincidence peak, have been demonstrated when increasing the pulse duration. For a constant incident pulse energy, the efficiency of acoustic generation is optimum for the shortest pulses. Nevertheless, for longer pulses designed to obtain thermal conditions below the ablation threshold, acoustic generation could be enhanced.

  10. Construction of a magnetic bottle spectrometer and its application to pulse duration measurement of X-ray laser using a pump-probe method

    NASA Astrophysics Data System (ADS)

    Namba, S.; Hasegawa, N.; Kishimoto, M.; Nishikino, M.; Ishino, M.; Kawachi, T.

    2015-11-01

    To characterize the temporal evolution of ultrashort X-ray pulses emitted by laser plasmas using a pump-probe method, a magnetic bottle time-of-flight electron spectrometer is constructed. The design is determined by numerical calculations of a mirror magnetic field and of the electron trajectory in a flight tube. The performance of the spectrometer is characterized by measuring the electron spectra of xenon atoms irradiated with a laser-driven plasma X-ray pulse. In addition, two-color above-threshold ionization (ATI) experiment is conducted for measurement of the X-ray laser pulse duration, in which xenon atoms are simultaneously irradiated with an X-ray laser pump and an IR laser probe. The correlation in the intensity of the sideband spectra of the 4d inner-shell photoelectrons and in the time delay of the two laser pulses yields an X-ray pulse width of 5.7 ps, in good agreement with the value obtained using an X-ray streak camera.

  11. Construction of a magnetic bottle spectrometer and its application to pulse duration measurement of X-ray laser using a pump-probe method

    SciTech Connect

    Namba, S.; Hasegawa, N.; Kishimoto, M.; Nishikino, M.; Ishino, M.; Kawachi, T.

    2015-11-15

    To characterize the temporal evolution of ultrashort X-ray pulses emitted by laser plasmas using a pump-probe method, a magnetic bottle time-of-flight electron spectrometer is constructed. The design is determined by numerical calculations of a mirror magnetic field and of the electron trajectory in a flight tube. The performance of the spectrometer is characterized by measuring the electron spectra of xenon atoms irradiated with a laser-driven plasma X-ray pulse. In addition, two-color above-threshold ionization (ATI) experiment is conducted for measurement of the X-ray laser pulse duration, in which xenon atoms are simultaneously irradiated with an X-ray laser pump and an IR laser probe. The correlation in the intensity of the sideband spectra of the 4d inner-shell photoelectrons and in the time delay of the two laser pulses yields an X-ray pulse width of 5.7 ps, in good agreement with the value obtained using an X-ray streak camera.

  12. TDR Using Autocorrelation and Varying-Duration Pulses

    NASA Technical Reports Server (NTRS)

    Lucena, Angel; Mullinex, Pam; Huang, PoTien; Santiago, Josephine; Mata, Carlos; Zavala, Carlos; Lane, John

    2008-01-01

    In an alternative to a prior technique of time-domain-reflectometry (TDR) in which very short excitation pulses are used, the pulses have very short rise and fall times and the pulse duration is varied continuously between a minimum and a maximum value. In both the present and prior techniques, the basic idea is to (1) measure the times between the generation of excitation pulses and the reception of reflections of the pulses as indications of the locations of one or more defects along a cable and (2) measure the amplitudes of the reflections as indication of the magnitudes of the defects. In general, an excitation pulse has a duration T. Each leading and trailing edge of an excitation pulse generates a reflection from a defect, so that a unique pair of reflections is associated with each defect. In the present alternative technique, the processing of the measured reflection signal includes computation of the autocorrelation function R(tau) identical with fx(t)x(t-tau)dt where t is time, x(t) is the measured reflection signal at time t, and taus is the correlation interval. The integration is performed over a measurement time interval short enough to enable identification and location of a defect within the corresponding spatial interval along the cable. Typically, where there is a defect, R(tau) exhibits a negative peak having maximum magnitude for tau in the vicinity of T. This peak can be used as a means of identifying a leading-edge/trailing-edge reflection pair. For a given spatial interval, measurements are made and R(tau) computed, as described above, for pulse durations T ranging from the minimum to the maximum value. The advantage of doing this is that the effective signal-to-noise ratio may be significantly increased over that attainable by use of a fixed pulse duration T.

  13. Period and pulse duration with "strobe" lights

    NASA Astrophysics Data System (ADS)

    Birriel, Jennifer

    2016-01-01

    Strobe lights have traditionally been discussed in The Physics Teacher in the context of stop action strobe photography. During the Halloween season most department and hardware stores sell inexpensive, compact "strobe" lights (although these can be found online year round). These lights generally sell for under 10 and usually employ LED lights. Most such devices have a rotary switch to adjust the rate at which the LED bulbs flash. This rotary switch is not calibrated—i.e., it has no markings to indicate the rate, but in general the greater the rotation of the switch from the off position, the faster the rate of flashing. We show how these simple devices can be used with a light sensor to study both the frequency of flashing and the duration of the light pulse. We briefly discuss if these devices are truly strobe lights.

  14. Pulse measurement apparatus and method

    DOEpatents

    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.

  15. Investigation of stone retropulsion as a function of Ho:YAG Laser pulse duration

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook; Lee, Ho; Petersen, Jason; Teichman, J. H.; Welch, A. J.

    2006-02-01

    Stone retropulsion during Ho:YAG (λ = 2.12 μm) laser lithotripsy with various pulse durations (τ p: 250 ~ 495 μsec) was investigated. Depending on pulse energy, optical pulse durations were divided into two regimes: short pulse (250~350 μsec) and long pulse (315~495 μsec). Retropulsion distance was measured as a function of pulse energy from 0.4 J to 1.2 J. Calculus phantoms made from plaster of Paris were ablated with a free running Ho:YAG laser using various optical fibers (200, 400, 600 μm) in water. In order to examine the ablation efficiency of two different pulse durations, a single pulse was applied, and the dynamics of the recoil action of a calculus phantom was monitored using a high-speed camera. The correlation among laser-induced topography, ablation volume, and retropulsion was evaluated. Higher pulse energy and larger fibers resulted in larger ablation volume and retropulsion. At a given pulse energy, optical pulses with different durations yielded comparable ablation volumes. The shorter duration pulses induced more retropulsion than longer pulses did at the same pulse energy. Larger retropulsion with the shorter pulse is thought to be induced by higher temperature at the vapor-solid interface, subsequently resulting in faster plume ejection with higher recoil momentum. The results suggest that a longer pulse could minimize retropulsion of the stone during lithotripsy.

  16. Note: compact helical pulse forming line for the generation of longer duration rectangular pulse.

    PubMed

    Sharma, Surender Kumar; Deb, P; Sharma, Archana; Shukla, R; Prabaharan, T; Adhikary, B; Shyam, A

    2012-06-01

    The helical pulsed forming line (PFL) can generate longer duration rectangular pulse in a smaller length. A compact PFL using helical water line is designed and experimentally investigated. The impedance of the helical PFL is 22 [ohm sign]. The compactness is achieved in terms of reduction in length of the PFL by a factor of 5.5 using helical water PFL as compared to coaxial water PFL of same length. The helical PFL was pulsed charged to 200 kV using a high voltage pulse transformer in 4.5 μs and discharged into the matched 22 Ω resistive load through a self-breakdown pressurized spark gap switch. The rectangular voltage pulse of 100 kV, 260 ns (FWHM) is measured across the load. The effect of reduction in water temperature on the pulse width is also studied experimentally. The increase in pulse width up to 7% more is observed by reducing the temperature of the deionized water to 5 °C. It will further reduce the length of the PFL and make the system small for compact pulsed power drivers. PMID:22755669

  17. Inductively stabilized, long pulse duration transverse discharge apparatus

    DOEpatents

    Sze, Robert C.

    1986-01-01

    An inductively stabilized, long pulse duration transverse discharge apparatus. The use of a segmented electrode where each segment is attached to an inductive element permits high energy, high efficiency, long-pulsed laser outputs to be obtained. The present apparatus has been demonstrated with rare-gas halide lasing media. Orders of magnitude increase in pulse repetition frequency are obtained in lasing devices that do not utilize gas flow.

  18. Autocorrelation measurements of bursts of picosecond pulses

    NASA Astrophysics Data System (ADS)

    van Oerle, Bart M.; Ernst, Gerard J.

    1996-09-01

    In a master oscillator power amplifier system a powerful train of pulses can be generated. A simple method is described to measure the duration of these pulses. The measurements have been performed both at the fundamental frequency (1053 nm) and at the second harmonic (527 nm). In accordance with theoretical expectations we have observed a narrowing of the pulse owing to frequency doubling.

  19. Influence of laser pulse duration on extreme ultraviolet and ion emission features from tin plasmas

    SciTech Connect

    Roy, A. E-mail: aroy@barc.gov.in; Harilal, S. S.; Polek, M. P.; Hassan, S. M.; Hassanein, A.; Endo, A.

    2014-03-15

    We investigated the role of laser pulse duration and intensity on extreme ultraviolet (EUV) generation and ion emission from a laser produced Sn plasma. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm Nd:YAG laser pulses with varying pulse duration (5–20 ns) and intensity. Experimental results performed at CMUXE indicate that the conversion efficiency (CE) of the EUV radiation strongly depend on laser pulse width and intensity, with a maximum CE of ∼2.0% measured for the shortest laser pulse width used (5 ns). Faraday Cup ion analysis of Sn plasma showed that the ion flux kinetic profiles are shifted to higher energy side with the reduction in laser pulse duration and narrower ion kinetic profiles are obtained for the longest pulse width used. However, our initial results showed that at a constant laser energy, the ion flux is more or less constant regardless of the excitation laser pulse width. The enhanced EUV emission obtained at shortest laser pulse duration studied is related to efficient laser-plasma reheating supported by presence of higher energy ions at these pulse durations.

  20. Diffraction response of photorefractive polymers over nine orders of magnitude of pulse duration

    PubMed Central

    Blanche, Pierre-Alexandre; Lynn, Brittany; Churin, Dmitriy; Kieu, Khanh; Norwood, Robert A.; Peyghambarian, Nasser

    2016-01-01

    The development of a single mode fiber-based pulsed laser with variable pulse duration, energy, and repetition rate has enabled the characterization of photorefractive polymer (PRP) in a previously inaccessible regime located between millisecond and microsecond single pulse illumination. With the addition of CW and nanosecond pulse lasers, four wave mixing measurements covering 9 orders of magnitudes in pulse duration are reported. Reciprocity failure of the diffraction efficiency according to the pulse duration for a constant energy density is observed and attributed to multiple excitation, transport and trapping events of the charge carriers. However, for pulses shorter than 30 μs, the efficiency reaches a plateau where an increase in energy density no longer affects the efficiency. This plateau is due to the saturation of the charge generation at high peak power given the limited number of sensitizer sites. The same behavior is observed in two different types of devices composed of the same material but with or without a buffer layer covering one electrode, which confirm the origin of these mechanisms. This new type of measurement is especially important to optimize PRP for applications using short pulse duration. PMID:27364998

  1. Diffraction response of photorefractive polymers over nine orders of magnitude of pulse duration

    NASA Astrophysics Data System (ADS)

    Blanche, Pierre-Alexandre; Lynn, Brittany; Churin, Dmitriy; Kieu, Khanh; Norwood, Robert A.; Peyghambarian, Nasser

    2016-07-01

    The development of a single mode fiber-based pulsed laser with variable pulse duration, energy, and repetition rate has enabled the characterization of photorefractive polymer (PRP) in a previously inaccessible regime located between millisecond and microsecond single pulse illumination. With the addition of CW and nanosecond pulse lasers, four wave mixing measurements covering 9 orders of magnitudes in pulse duration are reported. Reciprocity failure of the diffraction efficiency according to the pulse duration for a constant energy density is observed and attributed to multiple excitation, transport and trapping events of the charge carriers. However, for pulses shorter than 30 μs, the efficiency reaches a plateau where an increase in energy density no longer affects the efficiency. This plateau is due to the saturation of the charge generation at high peak power given the limited number of sensitizer sites. The same behavior is observed in two different types of devices composed of the same material but with or without a buffer layer covering one electrode, which confirm the origin of these mechanisms. This new type of measurement is especially important to optimize PRP for applications using short pulse duration.

  2. Diffraction response of photorefractive polymers over nine orders of magnitude of pulse duration.

    PubMed

    Blanche, Pierre-Alexandre; Lynn, Brittany; Churin, Dmitriy; Kieu, Khanh; Norwood, Robert A; Peyghambarian, Nasser

    2016-01-01

    The development of a single mode fiber-based pulsed laser with variable pulse duration, energy, and repetition rate has enabled the characterization of photorefractive polymer (PRP) in a previously inaccessible regime located between millisecond and microsecond single pulse illumination. With the addition of CW and nanosecond pulse lasers, four wave mixing measurements covering 9 orders of magnitudes in pulse duration are reported. Reciprocity failure of the diffraction efficiency according to the pulse duration for a constant energy density is observed and attributed to multiple excitation, transport and trapping events of the charge carriers. However, for pulses shorter than 30 μs, the efficiency reaches a plateau where an increase in energy density no longer affects the efficiency. This plateau is due to the saturation of the charge generation at high peak power given the limited number of sensitizer sites. The same behavior is observed in two different types of devices composed of the same material but with or without a buffer layer covering one electrode, which confirm the origin of these mechanisms. This new type of measurement is especially important to optimize PRP for applications using short pulse duration. PMID:27364998

  3. Development of high-voltage pulse-slicer unit with variable pulse duration for pulse radiolysis system

    NASA Astrophysics Data System (ADS)

    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.

  4. Energy distribution of fast electrons accelerated by high intensity laser pulse depending on laser pulse duration

    NASA Astrophysics Data System (ADS)

    Kojima, Sadaoki; Arikawa, Yasunobu; Morace, Alessio; Hata, Masayasu; Nagatomo, Hideo; Ozaki, Tetsuo; Sakata, Shohei; Lee, Seung Ho; Matsuo, Kazuki; Farley Law, King Fai; Tosaki, Shota; Yogo, Akifumi; Johzaki, Tomoyuki; Sunahara, Atsushi; Sakagami, Hitoshi; Nakai, Mitsuo; Nishimura, Hiroaki; Shiraga, Hiroyuki; Fujioka, Shinsuke; Azechi, Hiroshi

    2016-05-01

    The dependence of high-energy electron generation on the pulse duration of a high intensity LFEX laser was experimentally investigated. The LFEX laser (λ = 1.054 and intensity = 2.5 – 3 x 1018 W/cm2) pulses were focused on a 1 mm3 gold cubic block after reducing the intensities of the foot pulse and pedestal by using a plasma mirror. The full width at half maximum (FWHM) duration of the intense laser pulse could be set to either 1.2 ps or 4 ps by temporally stacking four beams of the LFEX laser, for which the slope temperature of the high-energy electron distribution was 0.7 MeV and 1.4 MeV, respectively. The slope temperature increment cannot be explained without considering pulse duration effects on fast electron generation.

  5. Effects of stimulation frequency versus pulse duration modulation on muscle fatigue

    PubMed Central

    Kesar, Trisha; Chou, Li-Wei; Binder-Macleod, Stuart A.

    2008-01-01

    During functional electrical stimulation (FES), both the frequency and intensity can be increased to increase muscle force output and counteract the effects of muscle fatigue. Most current FES systems, however, deliver a constant frequency and only vary the stimulation intensity to control muscle force. This study compared muscle performance and fatigue produced during repetitive electrical stimulation using three different strategies: (1) constant pulse-duration and stepwise increases in frequency (frequency-modulation); (2) constant frequency and stepwise increases in pulse-duration (pulse-duration-modulation); and (3) constant frequency and pulse-duration (no-modulation). Surface electrical stimulation was delivered to the quadriceps femoris muscles of 12 healthy individuals and isometric forces were recorded. Muscle performance was assessed by measuring the percent changes in the peak forces and force–time integrals between the first and the last fatiguing trains. Muscle fatigue was assessed by measuring percent declines in peak force between the 60 Hz pre- and post-fatigue testing trains. The results showed that frequency-modulation showed better performance for both peak forces and force–time integrals in response to the fatiguing trains than pulse-duration-modulation, while producing similar levels of muscle fatigue. Although frequency-modulation is not commonly used during FES, clinicians should consider this strategy to improve muscle performance. PMID:17317219

  6. Vacuum photoelectronic devices for measuring pulsed radiation

    NASA Astrophysics Data System (ADS)

    Berkovskii, A. G.; Veretennikov, A. I.; Kozlov, O. V.

    The design of these devices is discussed, and data are presented on their characteristics. These vacuum photoelectronic devices comprise photocells, photomultipliers, and electrooptical transducers designed for measuring pulsed radiation of nanosecond and subnanosecond duration. The fluctuation characteristics of the devices are examined, and their use in detectors of pulsed luminous and ionizing radiation is considered.

  7. Short-wavelength ablation of solids: pulse duration and wavelength effects

    NASA Astrophysics Data System (ADS)

    Juha, Libor; Bittner, Michal; Chvostova, Dagmar; Letal, Vit; Krasa, Josef; Otcenasek, Zdenek; Kozlova, Michaela; Polan, Jiri; Prag, Ansgar R.; Rus, Bedrich; Stupka, Michal; Krzywinski, Jacek; Andrejczuk, Andrzej; Pelka, Jerzy B.; Sobierajski, Ryszard H.; Ryc, Leszek; Feldhaus, Josef; Boody, Frederick P.; Fiedorowicz, Henryk; Bartnik, Andrzej; Mikolajczyk, Janusz; Rakowski, Rafal; Kubat, P.; Pina, Ladislav; Grisham, Michael E.; Vaschenko, Georgiy O.; Menoni, Carmen S.; Rocca, Jorge J. G.

    2004-11-01

    For conventional wavelength (UV-Vis-IR) lasers delivering radiation energy to the surface of materials, ablation thresholds, ablation (etch) rates, and the quality of ablated structures often differ dramatically between short (typically nanosecond) and ultrashort (typically femtosecond) pulses. Various short-wavelength (l < 100 nm) lasers emitting pulses with durations ranging from ~ 10 fs to ~ 1 ns have recently been put into a routine operation. This makes it possible to investigate how the ablation characteristics depend on the pulse duration in the XUV spectral region. 1.2-ns pulses of 46.9-nm radiation delivered from a capillary-discharge Ne-like Ar laser (Colorado State University, Fort Collins), focused by a spherical Sc/Si multilayer-coated mirror were used for an ablation of organic polymers and silicon. Various materials were irradiated with ellipsoidal-mirror-focused XUV radiation (λ = 86 nm, τ = 30-100 fs) generated by the free-electron laser (FEL) operated at the TESLA Test Facility (TTF1 FEL) in Hamburg. The beam of the Ne-like Zn XUV laser (λ = 21.2 nm, τ < 100 ps) driven by the Prague Asterix Laser System (PALS) was also successfully focused by a spherical Si/Mo multilayer-coated mirror to ablate various materials. Based on the results of the experiments, the etch rates for three different pulse durations are compared using the XUV-ABLATOR code to compensate for the wavelength difference. Comparing the values of etch rates calculated for short pulses with those measured for ultrashort pulses, we can study the influence of pulse duration on XUV ablation efficiency. Ablation efficiencies measured with short pulses at various wavelengths (i.e. 86/46.9/21.2 nm from the above-mentioned lasers and ~ 1 nm from the double stream gas-puff Xe plasma source driven by PALS) show that the wavelength influences the etch rate mainly through the different attenuation lengths.

  8. Short-Duration Simulations from Measurements.

    SciTech Connect

    Mitchell, Dean J.; Enghauser, Michael

    2014-08-01

    A method is presented that ascribes proper statistical variability to simulations that are derived from longer-duration measurements. This method is applicable to simulations of either real-value or integer-value data. An example is presented that demonstrates the applicability of this technique to the synthesis of gamma-ray spectra.

  9. On pulse duration of self-terminating lasers

    NASA Astrophysics Data System (ADS)

    Bokhan, P. A.

    2011-02-01

    The problem of the maximum pulse duration τmax of self-terminating lasers is considered. It is shown that the duration depends on the transition probability in the laser channel, on the decay rate of the resonant state in all other channels, and on the excitation rate of the metastable state. As a result, τmax is found to be significantly shorter than previously estimated. The criteria for converting the 'self-terminating' lasing to quasi-cw lasing are determined. It is shown that in the case of nonselective depopulation of the metastable state, for example in capillary lasers or in a fast flow of the active medium gas, it is impossible to obtain continuous lasing. Some concrete examples are considered. It is established that in several studies of barium vapour lasers (λ = 1.5 μm) and nitrogen lasers (λ = 337 nm), collisional lasing is obtained by increasing the relaxation rate of the metastable state in collisions with working particles (barium atoms and nitrogen molecules).

  10. Thermoluminescence measurement technique using millisecond temperature pulses.

    PubMed

    Manfred, Michael E; Gabriel, Nicholas T; Yukihara, Eduardo G; Talghader, Joseph J

    2010-06-01

    A measurement technique, pulsed thermoluminescence, is described which uses short thermal pulses to excite trapped carriers leading to radiative recombination. The pulses are obtained using microstructures with approximately 500 micros thermal time constants. The technique has many of the advantages of pulsed optically stimulated luminescence without the need for optical sources and filters to isolate the luminescent signal. Charge carrier traps in alpha-Al(2)O(3):C particles on microheaters were filled using 205 nm light. Temperature pulses of 10 and 50 ms were applied to the heaters and compared with a standard thermoluminescence curve taken at a ramp rate of 5 K s(-1). This produced curves of intensity verses temperature similar to standard thermoluminescence except shifted to higher temperatures. The luminescence of single particles was read multiple times with negligible loss of population. The lower limit of the duration of useful pulses appears to be limited by particle size and thermal contact between the particle and heater. PMID:20522565

  11. Simple circuit produces high-speed, fixed duration pulses

    NASA Technical Reports Server (NTRS)

    Garrahan, N. M.

    1965-01-01

    Circuit generates an output pulse of fixed width from a variable width input pulse. The circuit consists of a tunnel diode in parallel with an inductance driven by a constant current generator. It is used for pulsed communication equipment design.

  12. Apparatus and method for optical pulse measurement

    SciTech Connect

    Trebino, R.P.; Tsang, T.; Fittinghoff, D.N.; Sweetser, J.N.; Krumbuegel, M.A.

    1999-12-28

    Practical third-order frequency-resolved optical grating (FROG) techniques for characterization of ultrashort optical pulses are disclosed. The techniques are particularly suited to the measurement of single and/or weak optical pulses having pulse durations in the picosecond and subpicosecond regime. The relative quantum inefficiency of third-order nonlinear optical effects is compensated for through (i) use of phase-matched transient grating beam geometry to maximize interaction length, and (ii) use of interface-enhanced third-harmonic generation.

  13. Apparatus and method for optical pulse measurement

    DOEpatents

    Trebino, Rick P.; Tsang, Thomas; Fittinghoff, David N.; Sweetser, John N.; Krumbuegel, Marco A.

    1999-12-28

    Practical third-order frequency-resolved optical grating (FROG) techniques for characterization of ultrashort optical pulses are disclosed. The techniques are particularly suited to the measurement of single and/or weak optical pulses having pulse durations in the picosecond and subpicosecond regime. The relative quantum inefficiency of third-order nonlinear optical effects is compensated for through i) use of phase-matched transient grating beam geometry to maximize interaction length, and ii) use of interface-enhanced third-harmonic generation.

  14. A simple highly stable and temporally synchronizable Nd:glass laser oscillator delivering laser pulses of variable pulse duration from sub-nanosecond to few nanoseconds

    NASA Astrophysics Data System (ADS)

    Sharma, A. K.; Joshi, R. A.; Patidar, R. K.; Naik, P. A.; Gupta, P. D.

    2007-04-01

    A simple flash lamp pumped Nd:phosphate glass laser oscillator has been designed and set up delivering laser pulses of variable duration from ˜800 ps to 6 ns. It is based on Q-switching and full-wavelength cavity dumping and provides single laser pulse energy of 5 mJ and 11 mJ corresponding to pulse duration of ˜800 ps and 6 ns respectively at an electrical pump energy of 50 J. While the maximum pulse duration is governed by the cavity round trip time, the lower limit is decided by the switching speed of the high voltage pulse to the Pockels cell of the cavity dumper. Output laser pulses have shown enhanced pulse energy stability by dumping the cavity four round trips after the peak buildup. The laser pulses were synchronized with 250 ps positively chirped laser pulse train derived from an independent commercial cw mode locked Nd:fluorophosphate glass laser oscillator. The temporal jitter between these two pulses was measured to be ˜200 ps, limited by the speed of the electronics used.

  15. Multiplexer and time duration measuring circuit

    SciTech Connect

    Gray, Jr., James

    1980-01-01

    A multiplexer device is provided for multiplexing data in the form of randomly developed, variable width pulses from a plurality of pulse sources to a master storage. The device includes a first multiplexer unit which includes a plurality of input circuits each coupled to one of the pulse sources, with all input circuits being disabled when one input circuit receives an input pulse so that only one input pulse is multiplexed by the multiplexer unit at any one time.

  16. Effect of wavelength and pulse duration on laser micro-welding of monocrystalline silicon and glass

    NASA Astrophysics Data System (ADS)

    Nordin, I. H. W.; Okamoto, Y.; Okada, A.; Jiang, H.; Sakagawa, T.

    2016-04-01

    Micro-welding characteristics of silicon and glass by pulsed lasers are described. In this study, four types of laser beam, which are nanosecond pulsed laser and picosecond pulsed laser of 532 and 1064 nm in wavelength, were used for joining monocrystalline silicon and glass. Influence of wavelength and pulse duration on micro-welding of monocrystalline silicon and glass was experimentally investigated under the same spot diameter, and the molten area of monocrystalline silicon and glass was characterized. Finally, the breaking strength was evaluated for the overlap weld joint with different pulse duration and wavelength. A splash area of molten silicon around the weld bead line was obvious in the nanosecond pulsed laser. On the other hand, there was no remarkable molten splash around the weld bead line in the picosecond pulsed laser. Breaking strength of specimens with 1064 nm wavelength was higher than with 532 nm wavelength in nanosecond laser, whereas breaking strength of laser-irradiated specimen by picosecond pulse duration was higher than that by nanosecond pulse duration. It is concluded that the combination of picosecond pulse duration and infrared wavelength leads to the stable molten area appearance of the weld bead and higher breaking strength in micro-welding of glass and monocrystalline silicon.

  17. Determination of the pulse duration of an x-ray free electron laser using highly resolved single-shot spectra.

    PubMed

    Inubushi, Yuichi; Tono, Kensuke; Togashi, Tadashi; Sato, Takahiro; Hatsui, Takaki; Kameshima, Takashi; Togawa, Kazuaki; Hara, Toru; Tanaka, Takashi; Tanaka, Hitoshi; Ishikawa, Tetsuya; Yabashi, Makina

    2012-10-01

    We determined the pulse duration of x-ray free electron laser light at 10 keV using highly resolved single-shot spectra, combined with an x-ray free electron laser simulation. Spectral profiles, which were measured with a spectrometer composed of an ultraprecisely figured elliptical mirror and an analyzer flat crystal of silicon (555), changed markedly when we varied the compression strength of the electron bunch. The analysis showed that the pulse durations were reduced from 31 to 4.5 fs for the strongest compression condition. The method, which is readily applicable to evaluate shorter pulse durations, provides a firm basis for the development of femtosecond to attosecond sciences in the x-ray region. PMID:23083249

  18. Method and apparatus for producing durationally short ultraviolet or x-ray laser pulses

    DOEpatents

    MacGowan, B.J.; Matthews, D.L.; Trebes, J.E.

    1987-05-05

    A method and apparatus is disclosed for producing ultraviolet or x- ray laser pulses of short duration. An ultraviolet or x-ray laser pulse of long duration is progressively refracted, across the surface of an opaque barrier, by a streaming plasma that is produced by illuminating a solid target with a pulse of conventional line focused high power laser radiation. The short pulse of ultraviolet or x-ray laser radiation, which may be amplified to high power, is separated out by passage through a slit aperture in the opaque barrier.

  19. Method and apparatus for producing durationally short ultraviolet or X-ray laser pulses

    DOEpatents

    MacGowan, Brian J.; Matthews, Dennis L.; Trebes, James E.

    1988-01-01

    A method and apparatus is disclosed for producing ultraviolet or X-ray laser pulses of short duration (32). An ultraviolet or X-ray laser pulse of long duration (12) is progressively refracted, across the surface of an opaque barrier (28), by a streaming plasma (22) that is produced by illuminating a solid target (16, 18) with a pulse of conventional line focused high power laser radiation (20). The short pulse of ultraviolet or X-ray laser radiation (32), which may be amplified to high power (40, 42), is separated out by passage through a slit aperture (30) in the opaque barrier (28).

  20. Dynamics of laser-induced channel formation in water and influence of pulse duration on the ablation of biotissue under water with pulsed erbium-laser radiation

    NASA Astrophysics Data System (ADS)

    Ith, M.; Pratisto, H.; Altermatt, H. J.; Frenz, M.; Weber, H. P.

    1994-12-01

    The ability to use fiber-delivered erbium-laser radiation for non-contact arthroscopic meniscectomy in a liquid environment was studied. The laser radiation is transmitted through a water-vapor channel created by the leading part of the laser pulse. The dynamics of the channel formation around a submerged fiber tip was investigated with time-resolved flash photography. Strong pressure transients with amplitudes up to a few hundreds of bars measured with a needle hydrophone were found to accompany the channel formation process. Additional pressure transients in the range of kbars were observed after the laser pulse associated with the collapse of the vapor channel. Transmission measurements revealed that the duration the laser-induced channel stays open, and therefore the energy transmittable through it, is substantially determined by the laser pulse duration. The optimum pulse duration was found to be in the range between 250 and 350 µS. This was confirmed by histological evaluations of the laser incisions in meniscus: Increasing the pulse duration from 300 to 800 µs leads to a decrease in the crater depth from 1600 to 300 µm. A comparison of the histological examination after laser treatment through air and through water gave information on the influence of the vapor channel on the ablation efficiency, the cutting quality and the induced thermal damage in the adjacent tissue. The study shows that the erbium laser combined with an adequate fiber delivery system represents an effective surgical instrument liable to become increasingly accepted in orthopedic surgery.

  1. Ultrashort laser pulse ablation of copper, silicon and gelatin: effect of the pulse duration on the ablation thresholds and the incubation coefficients

    NASA Astrophysics Data System (ADS)

    Nathala, Chandra S. R.; Ajami, Ali; Husinsky, Wolfgang; Farooq, Bilal; Kudryashov, Sergey I.; Daskalova, Albena; Bliznakova, Irina; Assion, Andreas

    2016-02-01

    In this paper, the influence of the pulse duration on the ablation threshold and the incubation coefficient was investigated for three different types of materials: metal (copper), semiconductor (silicon) and biopolymer (gelatin). Ablation threshold values and the incubation coefficients have been measured for multiple Ti:sapphire laser pulses (3 to 1000 pulses) and for four different pulse durations (10, 30, 250 and 550 fs). The ablation threshold fluence was determined by extrapolation of curves from squared crater diameter versus fluence plots. For copper and silicon, the experiments were conducted in vacuum and for gelatin in air. For all materials, the ablation threshold fluence increases with the pulse duration. For copper, the threshold increases as τ 0.05, for silicon as τ 0.12 and for gelatin as τ 0.22. By extrapolating the curves of the threshold fluence versus number of pulses, the single-shot threshold fluence was determined for each sample. For 30 fs pulses, the single-shot threshold fluences were found to be 0.79, 0.35, and 0.99 J/cm2 and the incubation coefficients were found to be 0.75, 0.83 and 0.68 for copper, silicon and gelatin, respectively.

  2. The effects of pulse duration on ablation pressure driven by laser radiation

    SciTech Connect

    Zhou, Lei; Li, Xiao-Ya Zhu, Wen-Jun; Wang, Jia-Xiang; Tang, Chang-Jian

    2015-03-28

    The effects of laser pulse duration on the ablation pressure induced by laser radiation are investigated using Al target. Numerical simulation results using one dimensional radiation hydro code for laser intensities from 5×10{sup 12}W/cm{sup 2} to 5×10{sup 13}W/cm{sup 2} and pulse durations from 0.5 ns to 20 ns are presented. These results suggest that the laser intensity scaling law of ablation pressure differs for different pulse durations. And the theoretical analysis shows that the effects of laser pulse duration on ablation pressure are mainly caused by two regimes: the unsteady-state flow and the radiative energy loss to vacuum.

  3. Demonstration of negative signal delay with short-duration transient pulse

    NASA Astrophysics Data System (ADS)

    Ravelo, B.

    2011-07-01

    This paper introduces theoretic and experimental analyses of short-duration pulse propagation through a negative group delay (NGD) circuit. The basic analysis method of this electronic circuit operating in baseband and microwave frequencies is investigated. Then, its electrical fundamental characteristics vis-à-vis transient signals are developed. To validate the theoretic concept, planar hybrid devices with one- and two-stage NGD cells were designed, simulated, fabricated and tested. Transient analyses with ultra-wide band (UWB) pulse signals with different widths are realized. Then, experimental results in good agreement with the theoretical predictions were observed. Consequently, group delay going down under -2.5 ns is evidenced in baseband frequency up to 63 MHz with one-stage NGD cell. In time-domain, a Gaussian pulse in advance of about t0 = -1.5 ns or 20% of its half-height time-width was measured. This corresponds to a negative group velocity of about vg = L/t0 = -0.13c (L is the physical length of the tested device and c is light speed in the vacuum). More significant NGD value over 100-MHz bandwidth is stated with two-stage NGD cells. This results in a Gaussian pulse peak advance of about -5 ns (raising a group velocity of about vg = -0.12c) or 31% of its half-height time-width. Finally, some potential applications based on the NGD function are discussed.

  4. Factors influencing the microwave pulse duration in a klystron-like relativistic backward wave oscillator

    SciTech Connect

    Xiao Renzhen; Zhang Xiaowei; Zhang Ligang; Li Xiaoze; Zhang Lijun

    2012-07-15

    In this paper, we analyze the factors that affect the microwave pulse duration in a klystron-like relativistic backward wave oscillator (RBWO), including the diode voltage, the guiding magnetic field, the electron beam collector, the extraction cavity, and the gap between the electron beam and the slow wave structure (SWS). The results show that the microwave pulse duration increases with the diode voltage until breakdown occurs on the surface of the extraction cavity. The pulse duration at low guiding magnetic field is generally 5-10 ns smaller than that at high magnetic field due to the asymmetric electron emission and the larger energy spread of the electron beam. The electron beam collector can affect the microwave pulse duration significantly because of the anode plasma generated by bombardment of the electron beam on the collector surface. The introduction of the extraction cavity only slightly changes the pulse duration. The decrease of the gap between the electron beam and the SWS can increase the microwave pulse duration greatly.

  5. Dependence of gold nanoparticle production on pulse duration by laser ablation in liquid media

    NASA Astrophysics Data System (ADS)

    Riabinina, Daria; Chaker, Mohamed; Margot, Joëlle

    2012-04-01

    The dependence on laser fluence and laser pulse duration of size, size distribution and concentration of gold nanoparticles synthesized by laser ablation in liquid media was investigated. It was demonstrated that increasing laser energy from 1 to 5 mJ/pulse enhances the ablation rate by a factor of 100. The behavior of the ablation rate, hence of the nanoparticle concentration, as a function of pulse duration (varied from 40 fs to 200 ps) was found to strongly differ from that in air, which can be explained by photoionization and important losses of laser energy in the femtosecond regime. The optimal pulse duration for maximum ablation rate in liquid media was found to be equal to 2 ps.

  6. Influence of pulse duration on erbium and holmium laser ablation under water

    NASA Astrophysics Data System (ADS)

    Ith, Michael; Frenz, Martin; Pratisto, Hans S.; Weber, Heinz P.; Altermatt, Hans J.; Staeubli, Hans U.; Asshauer, Thomas; Delacretaz, Guy P.; Salathe, Rene-Paul; Gerber, Bruno E.

    1995-01-01

    Erbium and Holmium lasers are ideally suited for cutting and drilling biological tissue. This is due to the fact that their wavelengths (Er:YSGG at 2.79 micrometers and Ho:YAG at 2.12 micrometers ) are strongly absorbed in water which is present in all tissues. Combined with an optical fiber these lasers seem to be optimal instruments for endoscopic and/or minimal invasive applications in surgery. In this study we focused our interest on cutting of human meniscus in the knee where, besides a very limited operation field, the standard arthroscopic treatment is performed in a liquid, highly absorbing environment. The bubble formation process, therefore, has to be well understood because it mainly determines relevant aspects of tissue ablation. The influence of the laser parameters in general and the influence of pulse duration in particular are determined in this paper for two different laser wavelengths. The goal was to determine the optimum laser parameters in view of a high ablation efficiency, a high precision and a minimal destruction of the adjacent tissue. To determine the optimum pulse duration for ablating tissue under water and to obtain a better understanding of the channel formation process, transmission and pressure measurements together with video flash photography were performed. Additionally, we determined experimentally the ratio between initial laser pulse energy and energy available for tissue treatment under water. To prove the results obtained, cuts in human meniscus were performed, sectioned and evaluated. The comparison between the results obtained with the Erbium and Holmium laser revealed a strong influence of the absorption coefficients on the tissue effects, especially on the ablation efficiency and on the zone of thermally and mechanically damaged tissue.

  7. Compression of X-ray Free Electron Laser Pulses to Attosecond Duration

    NASA Astrophysics Data System (ADS)

    Sadler, James D.; Nathvani, Ricky; Oleśkiewicz, Piotr; Ceurvorst, Luke A.; Ratan, Naren; Kasim, Muhammad F.; Trines, Raoul M. G. M.; Bingham, Robert; Norreys, Peter A.

    2015-11-01

    State of the art X-ray Free Electron Laser facilities currently provide the brightest X-ray pulses available, typically with mJ energy and several hundred femtosecond duration. Here we present one- and two-dimensional Particle-in-Cell simulations, utilising the process of stimulated Raman amplification, showing that these pulses are compressed to a temporally coherent, sub-femtosecond pulse at 8% efficiency. Pulses of this type may pave the way for routine time resolution of electrons in nm size potentials. Furthermore, evidence is presented that significant Landau damping and wave-breaking may be beneficial in distorting the rear of the interaction and further reducing the final pulse duration.

  8. Compression of X-ray Free Electron Laser Pulses to Attosecond Duration.

    PubMed

    Sadler, James D; Nathvani, Ricky; Oleśkiewicz, Piotr; Ceurvorst, Luke A; Ratan, Naren; Kasim, Muhammad F; Trines, Raoul M G M; Bingham, Robert; Norreys, Peter A

    2015-01-01

    State of the art X-ray Free Electron Laser facilities currently provide the brightest X-ray pulses available, typically with mJ energy and several hundred femtosecond duration. Here we present one- and two-dimensional Particle-in-Cell simulations, utilising the process of stimulated Raman amplification, showing that these pulses are compressed to a temporally coherent, sub-femtosecond pulse at 8% efficiency. Pulses of this type may pave the way for routine time resolution of electrons in nm size potentials. Furthermore, evidence is presented that significant Landau damping and wave-breaking may be beneficial in distorting the rear of the interaction and further reducing the final pulse duration. PMID:26568520

  9. Compression of X-ray Free Electron Laser Pulses to Attosecond Duration

    PubMed Central

    Sadler, James D.; Nathvani, Ricky; Oleśkiewicz, Piotr; Ceurvorst, Luke A.; Ratan, Naren; Kasim, Muhammad F.; Trines, Raoul M. G. M.; Bingham, Robert; Norreys, Peter A.

    2015-01-01

    State of the art X-ray Free Electron Laser facilities currently provide the brightest X-ray pulses available, typically with mJ energy and several hundred femtosecond duration. Here we present one- and two-dimensional Particle-in-Cell simulations, utilising the process of stimulated Raman amplification, showing that these pulses are compressed to a temporally coherent, sub-femtosecond pulse at 8% efficiency. Pulses of this type may pave the way for routine time resolution of electrons in nm size potentials. Furthermore, evidence is presented that significant Landau damping and wave-breaking may be beneficial in distorting the rear of the interaction and further reducing the final pulse duration. PMID:26568520

  10. Dynamic characterization of short duration stress pulses generated by a magnetic flyer plate in carbon-fiber/epoxy laminates

    SciTech Connect

    Bruck, H.A.; Epstein, J.S.; Perry, K.E. Jr.; Abdallah, M.G.

    1995-11-01

    There is a great deal of interest in characterizing the dynamic mechanical behavior of laminated carbon-fiber/epoxy composites for military and aerospace applications. Current research efforts have been directed at measuring the strength lost because of accumulated damage. Very little work has been done to determine how this damage is accumulated during dynamic mechanical loading. Of particular interest is the effect of short duration (< 1 {micro}s) stress pulses on mechanical behavior such as delamination. In this paper, a magnetic flyer plate apparatus is presented for generating a short duration stress pulse in a unidirectional carbon-fiber/epoxy laminated composite. The stress pulse is characterized using a dynamic moire interferometer.

  11. Porcine skin visible lesion thresholds for near-infrared lasers including modeling at two pulse durations and spot sizes

    NASA Astrophysics Data System (ADS)

    Cain, Clarence P.; Polhamus, Garrett D.; Roach, William P.; Stolarski, David J.; Schuster, Kurt J.; Stockton, Kevin; Rockwell, Benjamin A.; Chen, Bo; Welch, Ashley J.

    2006-07-01

    With the advent of such systems as the airborne laser and advanced tactical laser, high-energy lasers that use 1315-nm wavelengths in the near-infrared band will soon present a new laser safety challenge to armed forces and civilian populations. Experiments in nonhuman primates using this wavelength have demonstrated a range of ocular injuries, including corneal, lenticular, and retinal lesions as a function of pulse duration. American National Standards Institute (ANSI) laser safety standards have traditionally been based on experimental data, and there is scant data for this wavelength. We are reporting minimum visible lesion (MVL) threshold measurements using a porcine skin model for two different pulse durations and spot sizes for this wavelength. We also compare our measurements to results from our model based on the heat transfer equation and rate process equation, together with actual temperature measurements on the skin surface using a high-speed infrared camera. Our MVL-ED50 thresholds for long pulses (350 µs) at 24-h postexposure are measured to be 99 and 83 Jcm-2 for spot sizes of 0.7 and 1.3 mm diam, respectively. Q-switched laser pulses of 50 ns have a lower threshold of 11 Jcm-2 for a 5-mm-diam top-hat laser pulse.

  12. Ventricular myocyte injury by high-intensity electric field: Effect of pulse duration.

    PubMed

    Prado, Luiza Ns; Goulart, Jair T; Zoccoler, Marcelo; Oliveira, Pedro X

    2016-04-01

    Although high-intensity electric fields (HEF) application is currently the only effective therapy available to terminate ventricular fibrillation, it may cause injury to cardiac cells. In this study we determined the relation between HEF pulse length and cardiomyocyte lethal injury. We obtained lethality curves by survival analysis, which were used to determine the value of HEF necessary to kill 50% of cells (E50) and plotted a strength-duration (SxD) curve for lethality with 10 different durations: 0.1, 0.2, 0.5, 1, 3, 5, 10, 20, 35 and 70 ms. For the same durations we also obtained an SxD curve for excitation and established an indicator for stimulatory safeness (stimulation safety factor - SSF) as the ratio between the SxD curve for lethality and one for excitation. We found that the lower the pulse duration, the higher the HEF intensity required to cell death. Contrary to expectations, the highest SSF value does not correspond to the lowest pulse duration but to the one of 0.5 ms. As defibrillation threshold has been described as duration-dependent, our results imply that the use of shorter stimulus duration - instead of the one typically used in the clinic (10 ms) - might increase defibrillation safeness. PMID:26830130

  13. Role of PTHrP(1-34) Pulse Frequency Versus Pulse Duration to Enhance Mesenchymal Stromal Cell Chondrogenesis.

    PubMed

    Fischer, Jennifer; Ortel, Marlen; Hagmann, Sebastien; Hoeflich, Andreas; Richter, Wiltrud

    2016-12-01

    Generation of phenotypically stable, articular chondrocytes from mesenchymal stromal cells (MSCs) is still an unaccomplished task, with formation of abundant, hyaline extracellular matrix, and avoidance of hypertrophy being prime challenges. We recently demonstrated that parathyroid hormone-related protein (PTHrP) is a promising factor to direct chondrogenesis of MSCs towards an articular phenotype, since intermittent PTHrP application stimulated cartilage matrix production and reduced undesired hypertrophy. We here investigated the role of frequency, pulse duration, total exposure time, and underlying mechanisms in order to unlock the full potential of PTHrP actions. Human MSC subjected to in vitro chondrogenesis for six weeks were exposed to 2.5 nM PTHrP(1-34) pulses from days 7 to 42. Application frequency was increased from three times weekly (3 × 6 h/week) to daily maintaining either the duration of individual pulses (6 h/day) or total exposure time (18 h/week; 2.6 h/day). Daily PTHrP treatment significantly increased extracellular matrix deposition regardless of pulse duration and suppressed alkaline-phosphatase activity by 87%. High total exposure time significantly reduced cell proliferation at day 14. Pulse duration was critically important to significantly reduce IHH expression, but irrelevant for PTHrP-induced suppression of the hypertrophic markers MEF2C and IBSP. COL10A1, RUNX2, and MMP13 expression remained unaltered. Decreased IGFBP-2, -3, and -6 expression suggested modulated IGF-I availability in PTHrP groups, while drop of SOX9 protein levels during the PTHrP-pulse may delay chondroblast formation and hypertrophy. Overall, the significantly optimized timing of PTHrP-pulses demonstrated a vast potential to enhance chondrogenesis of MSC and suppress hypertrophy possibly via superior balancing of IGF- and SOX9-related mechanisms. J. Cell. Physiol. 231: 2673-2681, 2016. © 2016 Wiley Periodicals, Inc. PMID:27548511

  14. Ignition and Growth Modeling of Short Pulse Duration Shock Initiation Experiments on HNS IV

    NASA Astrophysics Data System (ADS)

    Tarver, Craig; Chidester, Steven

    2013-06-01

    Short pulse duration shock initiation experiments on 1.60 g/cm3 density (92% TMD) HNS IV have been reported by Schwarz, Bowden et al., Dudley et al., Goveas et al., Greenaway et al., and others. This flyer threshold velocity for detonation/failure data plus measured unreacted HNS Hugoniot data and detonation cylinder test product expansion data were used as the experimental basis for the development of an Ignition and Growth reactive flow model for the shock initiation of HNS IV. The resulting Ignition and Growth HNS IV model parameters yielded good overall agreement with all of this experimental data. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.: Explosive, HNS IV, shock to detonation transition, Ignition and Growth: 82.33.Vx, 82.40.Fp.

  15. Wide Range SET Pulse Measurement

    NASA Technical Reports Server (NTRS)

    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

  16. Dependence of Nd:YAG laser derusting and passivation of iron artifacts on pulse duration

    NASA Astrophysics Data System (ADS)

    Osticioli, Iacopo; Siano, Salvatore

    2013-11-01

    In this work laser derusting and passivation process of iron objects of conservation interest were investigated. In particular, the effects induced by laser irradiation of three lasers with different temporal emission regimes were studied, exhibiting very different behavior. Nd:YAG(1064 nm) laser systems were employed in the experiments: a Q-Switching laser with pulse duration of 8 ns, a Long Q-Switching laser with pulse duration of 120 ns and a Short Free Running pulse duration in a range of 40-120 μs. These lasers are commonly used in conservation. Lasers treatments were applied on iron samples subjected to natural weathering in outdoor conditions for about five years. Moreover some experiments were also performed on metallic parts of an original chandelier from the seventies as well as on a deeply corroded Roman sword. Results obtained reveals that longer pulse duration leads to phase changes on the rust layer and a homogeneous black-grayish coating is formed on the surface (identified as magnetite) after treatment. Whereas, QS laser pulses are capable to induce ablation of the corrosion layer exposing the pure metal underneath. Finally, LQS interaction includes deep ablation with localized micro-melting of the metal surface and partial transformation of the residual mineral areas was observed. The irradiation results were characterized through optical and BS- ESEM along with Raman spectroscopy, which allowed a clear phenomenological differentiation among the three operating regimes and provided information on their optimal exploitation in restoration of iron artifacts.

  17. Duration of Diabetes Predicts Aortic Pulse Wave Velocity and Vascular Events in Alström Syndrome

    PubMed Central

    Smith, Jamie; Carey, Catherine; Barrett, Timothy; Campbell, Fiona; Maffei, Pietro; Marshall, Jan D.; Paisey, Christopher; Steeds, Richard P.; Edwards, Nicola C.; Bunce, Susan; Geberhiwot, Tarekegn

    2015-01-01

    Context: Alström syndrome is characterized by increased risk of cardiovascular disease from childhood. Objective: To explore the association between risk factors for cardiovascular disease, aortic pulse wave velocity, and vascular events in Alström syndrome. Design: Cross-sectional analyses with 5-year follow-up. Setting: The UK NHS nationally commissioned specialist clinics for Alström syndrome. Patients: Thirty-one Alström patients undertook vascular risk assessment, cardiac studies, and aortic pulse wave velocity measurement. Subsequent clinical outcomes were recorded. Interventions: Insulin resistance was treated with lifestyle intervention and metformin, and diabetes with the addition of glitazones, glucagon-like peptide 1 agonists, and/or insulin. Thyroid and T deficiencies were corrected. Dyslipidemia was treated with statins and nicotinic acid derivatives. Cardiomyopathy was treated with standard therapy as required. Main Outcome Measures: The associations of age, gender, and risk factors for cardiovascular disease with aortic pulse wave velocity were assessed and correlated with the effects of reduction in left ventricular function. Vascular events were monitored for 5 years. Results: Aortic pulse wave velocity was positively associated with the duration of diabetes (P = .001) and inversely with left ventricular ejection fraction (P = .036). Five of the cohort with cardiovascular events had higher aortic pulse wave velocity (P = .0247), and all had long duration of diabetes. Conclusions: Duration of diabetes predicted aortic pulse wave velocity in Alström syndrome, which in turn predicted cardiovascular events. This offers hope of secondary prevention because type 2 diabetes can be delayed or reversed by lifestyle interventions. PMID:26066530

  18. Influence of the Nd:YAG Laser Pulse Duration on the Temperature of Primary Enamel

    PubMed Central

    Valério, R. A.; da Cunha, V. S.; Galo, R.; de Lima, F. A.; Bachmann, L.; Corona, S. A. M.; Borsatto, M. C.

    2015-01-01

    The aim of this study is to evaluate the temperature change on specimens of primary enamel irradiated with different pulse duration of Nd:YAG laser. Fifteen sound primary molars were sectioned mesiodistally, resulting in 30 specimens (3.5 × 3.5 × 2.0 mm). Two small holes were made on the dentin surface in which K-type thermocouples were installed to evaluate thermal changes. Specimens were randomly assigned in 3 groups (n = 10): A = EL (extra long pulse, 10.000 μs), B = LP (long pulse, 700 μs), and C = SP (short pulse, 350 μs). Nd:YAG laser (λ = 1.064 μm) was applied at contact mode (10 Hz, 0.8 W, 80 mJ) and energy density of 0.637 mJ/mm2. Analysis of variance (ANOVA) was performed for the statistical analysis (P = 0.46). Nd:YAG laser pulse duration provided no difference on the temperature changes on primary enamel, in which the following means were observed: A = EL (23.15°C ± 7.75), B = LP (27.33°C ± 11.32), and C = SP (26.91°C ± 12.85). It can be concluded that the duration of the laser pulse Nd:YAG increased the temperature of the primary enamel but was not influenced by different pulse durations used in the irradiation. PMID:25874244

  19. Toxicity of two pulsed metal exposures to Daphnia magna: relative effects of pulsed duration-concentration and influence of interpulse period.

    PubMed

    Hoang, Tham C; Gallagher, Jeffrey S; Tomasso, Joseph R; Klaine, Stephen J

    2007-11-01

    Aquatic organisms living in surface waters experience fluctuating contaminant exposures that vary in concentration, duration, and frequency. This study characterized the role of pulsed concentration, pulsed duration, and the interval between pulses on the toxicity of four metals (Cu, Zn, Se, and As) to Daphnia magna. During 21-d toxicity tests, neonatal D. magna were exposed to single or double pulses. Pulsed concentrations and durations ranged from 32 to 6000 microg/L and 8 to 96 h, respectively. Intervals between two pulses ranged from 24 to 288 h. Mortality, growth, and reproduction were characterized for exposures. For single-pulse exposures of Cu and As, metal concentration had a stronger effect on survival of D. magna than did pulsed duration: pulses with 2X concentration and 1Y duration resulted in more mortality than did pulses with 1X concentration and 2Y duration. In contrast, effects of pulsed duration were stronger than metal concentration for Zn. However, the effects of duration and concentration were similar for Se. The relative effects of pulsed concentration and duration found in the present study revealed that the common method using area under the curve (AUC = concentration x duration) may not always accurately estimate environmental risk from metals (e.g., for Cu, Zn, As). In addition, the occurrence of delayed mortality in the present study revealed that using continuous exposure bioassays might underestimate metal toxicity to aquatic biota. For double-pulse exposures, the toxicity of the second pulse was influenced by the first pulse for all four metals. This influence was dependent on the pulsed concentration and duration and the interval between pulses. Further, toxicity caused by the second pulse decreased as the time between the exposures increased. For all four metals, there existed an interval great enough that the toxicity of the two pulses was independent. This would result in less toxicity for multiple exposures than continuous

  20. Flexible control of femtosecond pulse duration and separation using an emittance-spoiling foil in x-ray free-electron lasers

    SciTech Connect

    Ding, Y.; Behrens, C.; Coffee, R.; Decker, F. -J.; Emma, P.; Field, C.; Helml, W.; Huang, Z.; Krejcik, P.; Krzywinski, J.; Loos, H.; Lutman, A.; Marinelli, A.; Maxwell, T. J.; Turner, J.

    2015-06-22

    We report experimental studies of generating and controlling femtosecond x-ray pulses in free-electron lasers (FELs) using an emittance spoiling foil. By selectivity spoiling the transverse emittance of the electron beam, the output pulse duration or double-pulse separation is adjusted with a variable size single or double slotted foil. Measurements were performed with an X-band transverse deflector located downstream of the FEL undulator, from which both the FEL lasing and emittance spoiling effects are observed directly.

  1. Simultaneous optimization of power and duration of radio-frequency pulse in PARACEST MRI.

    PubMed

    Rezaeian, Mohammad-Reza; Hossein-Zadeh, Gholam-Ali; Soltanian-Zadeh, Hamid

    2016-07-01

    Chemical exchange saturation transfer (CEST) MRI is increasingly used to probe mobile proteins and microenvironment properties, and shows great promise for tumor and stroke diagnosis. The CEST effect is complex and depends not only on the CEST agent concentration, exchange rates, the characteristic of the magnetization transfer (MT), and the relaxation properties of the tissue, but also varies with the experimental conditions such as radio-frequency (RF) pulse power and duration. The RF pulse is one of the most important factors that promote the CEST effect for biological properties such as pH, temperature and protein content, especially for contrast agents with intermediate to fast exchange rates. The CEST effect is susceptible to the RF duration and power. The present study aims at determining the optimal power and the corresponding optimal duration (that maximize the CEST effect) using an off-resonance scheme through a new definition of the CEST effect. This definition is formulated by solving the Bloch-McConnell equation through the R1ρ method (based on the eigenspace solution) for both of the MT and CEST effects as well as their interactions. The proposed formulations of the optimal RF pulse power and duration are the first formulations in which the MT effect is considered. The extracted optimal RF pulse duration and power are compared with those of the MTR asymmetry model in two- and three-pool systems, using synthetic data that are similar to the muscle tissue. To validate them further, the formulations are compared with the empirical formulation of the CEST effect and other findings of the previous researches. By extending our formulations, the optimal power and the corresponding optimal duration (in the biological systems with many chemical exchange sites) can be determined. PMID:26956610

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

    PubMed

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

    2015-11-16

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

  3. Laser ablation of GaAs in liquid: the role of laser pulse duration

    NASA Astrophysics Data System (ADS)

    De Bonis, Angela; Galasso, Agostino; Santagata, Antonio; Teghil, Roberto

    2016-01-01

    The synthesis of gallium arsenide (GaAs) nanoparticles has attracted wide scientific and technological interest due to the possibility of tuning the GaAs NP (nanoparticle) band gap across the visible spectrum and their consequent use in optoelectronic devices. In recent years, laser ablation in liquid (LAL) has been widely used for the preparation of colloidal solutions of semiconducting and metallic nanoparticles, thanks to its flexibility. With the aim of highlighting the key role played by laser pulse duration on the ablation mechanism and on the properties of the obtained materials, laser ablation of a gallium arsenide target in acetone was performed using laser sources operating in two different temporal regimes: Nd:glass laser (λ   =  527 nm, pulse duration of 250 fs and frequency repetition rate of 10 Hz) and Nd:YAG laser (λ   =  532 nm, pulse duration of 7 ns and frequency repetition rate of 10 Hz). The ablation process was studied following the dynamics of the laser induced shock waves (SWs) and cavitation bubbles (CBs) by fast shadowgraphy, showing that CB dimension and lifetime is related to the laser pulse length. A characterization of the obtained materials by TEM (transmission electron microscopy) and microRaman spectroscopy have shown that quite spherical gallium oxide/GaAs nanoparticles can be obtained by nanosecond laser ablation. On the other hand, pure polycrystalline GaAs nanoparticles can be produced by using an ultrashort laser source.

  4. Parametric amplification and compression to ultrashort pulse duration of resonant linear waves

    NASA Astrophysics Data System (ADS)

    Aguergaray, C.; Andersen, T. V.; Schimpf, D. N.; Schmidt, O.; Rothhardt, J.; Schreiber, T.; Limpert, J.; Cormier, E.; Tünnermann, A.

    2007-04-01

    We report on an optical parametric amplification system which is pumped and seeded by fiber generated laser radiation. Due to its low broadening threshold, high spatial beam quality and high stability, the fiber based broad bandwidth signal generation is a promising alternative to white light generation in bulky glass or sapphire plates. We demonstrate a novel and successful signal engineering implemented in a setup for parametric amplification and subsequent recompression of resonant linear waves resulting from soliton fission in a highly nonlinear photonic crystal fiber. The applied pump source is a high repetition rate ytterbium-doped fiber chirped pulse amplification system. The presented approach results in the generation of ~50 fs pulses at MHz repetition rate. The potential of generating even shorter pulse duration and higher pulse energies will be discussed.

  5. Laser stimulation of the auditory system at 1.94 μm and microsecond pulse durations

    NASA Astrophysics Data System (ADS)

    Izzo, Agnella D.; Walsh, Joseph T., Jr.; Ralph, Heather; Webb, Jim; Wells, Jonathon; Bendett, Mark; Richter, Claus-Peter

    2008-02-01

    Light can artificially stimulate nerve activity in vivo. A significant advantage of optical neural stimulation is the potential for higher spatial selectivity when compared with electrical stimulation. An increased spatial selectivity of stimulation could improve significantly the function of neuroprosthetics, such as cochlear implants. Cochlear implants restore a sense of hearing and communication to deaf individuals by directly electrically stimulating the remaining neural cells in the cochlea. However, performance is limited by overlapping electric fields from neighboring electrodes. Here, we report on experiments with a new laser, offering a previously unavailable wavelength, 1.94μm, and pulse durations down to 5μs, to stimulate cochlear neurons. Compound action potentials (CAP) were evoked from the gerbil cochlea with pulse durations as short as 1μs. Data show that water absorption of light is a significant factor in optical stimulation, as evidenced by the required distance between the optical fiber and the neurons during stimulation. CAP threshold measurements indicate that there is an optimal range of pulse durations over which to deposit the laser energy, less than ~100μs. The implications of these data could direct further research and design of an optical cochlear implant.

  6. Effect of adjusting pulse durations of functional electrical stimulation cycling on energy expenditure and fatigue after spinal cord injury.

    PubMed

    Gorgey, Ashraf S; Poarch, Hunter J; Dolbow, David D; Castillo, Teodoro; Gater, David R

    2014-01-01

    The purpose of the current study was to determine the effects of three different pulse durations (200, 350, and 500 microseconds [P200, P350, and P500, respectively]) on oxygen uptake (VO2), cycling performance, and energy expenditure (EE) percentage of fatigue of the knee extensor muscle group immediately and 48 to 72 h after cycling in persons with spinal cord injury (SCI). A convenience sample of 10 individuals with motor complete SCI participated in a repeated-measures design using a functional electrical stimulation (FES) cycle ergometer over a 3 wk period. There was no difference among the three FES protocols on relative VO2 or cycling EE. Delta EE between exercise and rest was 42% greater in both P500 and P350 compared with P200 (p = 0.07), whereas recovery VO2 was 23% greater in P350 compared with P200 (p = 0.03). There was no difference in the outcomes of the three pulse durations on muscle fatigue. Knee extensor torque significantly decreased immediately after (p < 0.001) and 48 to 72 h after (p < 0.001) FES leg cycling. Lengthening pulse duration did not affect submaximal or relative VO2 or EE, total EE, and time to fatigue. Greater recovery VO2 and delta EE were noted in P350 and P500 compared with P200. An acute bout of FES leg cycling resulted in torque reduction that did not fully recover 48 to 72 h after cycling. PMID:25803753

  7. Speech perception with interaction-compensated simultaneous stimulation and long pulse durations in cochlear implant users.

    PubMed

    Schatzer, Reinhold; Koroleva, Inna; Griessner, Andreas; Levin, Sergey; Kusovkov, Vladislav; Yanov, Yuri; Zierhofer, Clemens

    2015-04-01

    Early multi-channel designs in the history of cochlear implant development were based on a vocoder-type processing of frequency channels and presented bands of compressed analog stimulus waveforms simultaneously on multiple tonotopically arranged electrodes. The realization that the direct summation of electrical fields as a result of simultaneous electrode stimulation exacerbates interactions among the stimulation channels and limits cochlear implant outcome led to the breakthrough in the development of cochlear implants, the continuous interleaved (CIS) sampling coding strategy. By interleaving stimulation pulses across electrodes, CIS activates only a single electrode at each point in time, preventing a direct summation of electrical fields and hence the primary component of channel interactions. In this paper we show that a previously presented approach of simultaneous stimulation with channel interaction compensation (CIC) may also ameliorate the deleterious effects of simultaneous channel interaction on speech perception. In an acute study conducted in eleven experienced MED-EL implant users, configurations involving simultaneous stimulation with CIC and doubled pulse phase durations have been investigated. As pairs of electrodes were activated simultaneously and pulse durations were doubled, carrier rates remained the same. Comparison conditions involved both CIS and fine structure (FS) strategies, either with strictly sequential or paired-simultaneous stimulation. Results showed no statistical difference in the perception of sentences in noise and monosyllables for sequential and paired-simultaneous stimulation with doubled phase durations. This suggests that CIC can largely compensate for the effects of simultaneous channel interaction, for both CIS and FS coding strategies. A simultaneous stimulation paradigm has a number of potential advantages over a traditional sequential interleaved design. The flexibility gained when dropping the requirement of

  8. Miniature pulsed magnet system for synchrotron x-ray measurements

    SciTech Connect

    Linden, Peter J. E. M. van der; Mathon, Olivier; Strohm, Cornelius; Sikora, Marcin

    2008-07-15

    We have developed a versatile experimental apparatus for synchrotron x-ray measurements in pulsed high magnetic fields. The apparatus consists of a double cryostat incorporating a liquid nitrogen bath to cool the miniature pulsed coil and an independent helium flow cryostat allowing sample temperatures from 4 up to 250 K. The high duty cycle miniature pulsed coils can generate up to 38 T. During experiments at 30 T a repetition rate of 6 pulses/min was routinely reached. Using a 4 kJ power supply, the pulse duration was between 500 {mu}s and 1 ms. The setup was used for nuclear forward scattering measurements on {sup 57}Fe up to 25 T on the ESRF beamline ID18. In another experiment, x-ray magnetic circular dichroism was measured up to 30 T on the ESRF energy dispersive beamline ID24.

  9. The effect of pulse duration on laser-induced damage by 1053-nm light in potassium dihydrogen phosphate crystals

    NASA Astrophysics Data System (ADS)

    Cross, D. A.; Braunstein, M. R.; Carr, C. W.

    2007-01-01

    Laser induced damage in potassium dihydogen phosphate (KDP) has previously been shown to depend significantly on pulse duration for 351-nm Gaussian pulses. In this work we studied the properties of damage initiated by 1053-nm temporally Gaussian pulses with 10ns and 3ns FWHM durations. Our results indicate that the number of damage sites induced by 1053-nm light scales with pulse duration (τ) as τ I/τ II) 0.17 in contrast to the previously reported results for 351-nm light as (τ I/τ II) 0.35. This indicates that damage site formation is significantly less probable at longer wavelengths for a given fluence.

  10. Combining microwave beams with high peak power and long pulse duration

    SciTech Connect

    Li Guolin; Shu Ting; Yuan Chengwei; Zhang Jun; Jin Zhenxing; Yang Jianhua

    2010-03-15

    The beam combining results with a metal dichroic plate illuminated by the S/X band gigawatt level high power microwaves are presented. According to the previous experiments, the microwave breakdown problem becomes obvious when the peak power and the pulse duration increase, thus, several methods for enhancing the power handling capacity have been considered, and the metal dichroic plates are redesigned to handle the S/X band high power microwaves. Then the design, fabrication, and testing procedure are discussed in detail. The further experimental results reveal that, operated on the self-built accelerator Spark-04, the radiated powers from the S and X band sources have reached 1.8 GW with pulse durations of about 80 ns, and both beams have been successfully operated on the selected dichroic plate without microwave breakdown.

  11. Laser Pulse Duration Is Critical For the Generation of Plasmonic Nanobubbles

    PubMed Central

    2015-01-01

    Plasmonic nanobubbles (PNBs) are transient vapor nanobubbles generated in liquid around laser-overheated plasmonic nanoparticles. Unlike plasmonic nanoparticles, PNBs’ properties are still largely unknown due to their highly nonstationary nature. Here we show the influence of the duration of the optical excitation on the energy efficacy and threshold of PNB generation. The combination of picosecond pulsed excitation with the nanoparticle clustering provides the highest energy efficacy and the lowest threshold fluence, around 5 mJ cm–2, of PNB generation. In contrast, long excitation pulses reduce the energy efficacy of PNB generation by several orders of magnitude. Ultimately, the continuous excitation has the minimal energy efficacy, nine orders of magnitude lower than that for the picosecond excitation. Thus, the duration of the optical excitation of plasmonic nanoparticles can have a stronger effect on the PNB generation than the excitation wavelength, nanoparticle size, shape, or other “stationary” properties of plasmonic nanoparticles. PMID:24916057

  12. Rhythm measures and dimensions of durational variation in speech.

    PubMed

    Loukina, Anastassia; Kochanski, Greg; Rosner, Burton; Keane, Elinor; Shih, Chilin

    2011-05-01

    Patterns of durational variation were examined by applying 15 previously published rhythm measures to a large corpus of speech from five languages. In order to achieve consistent segmentation across all languages, an automatic speech recognition system was developed to divide the waveforms into consonantal and vocalic regions. The resulting duration measurements rest strictly on acoustic criteria. Machine classification showed that rhythm measures could separate languages at rates above chance. Within-language variability in rhythm measures, however, was large and comparable to that between languages. Therefore, different languages could not be identified reliably from single paragraphs. In experiments separating pairs of languages, a rhythm measure that was relatively successful at separating one pair often performed very poorly on another pair: there was no broadly successful rhythm measure. Separation of all five languages at once required a combination of three rhythm measures. Many triplets were about equally effective, but the confusion patterns between languages varied with the choice of rhythm measures. PMID:21568427

  13. Strength-duration curve: a measure for assessing sensory deficit in peripheral neuropathy.

    PubMed Central

    Friedli, W G; Meyer, M

    1984-01-01

    By using an isolated constant current stimulator producing true square-wave pulses, sensory strength-duration curves were obtained at various sites by percutaneous electrical stimulation. Strength-duration curves derived from normal groups were compared to those of patients with peripheral neuropathy. Stimulus strength at sensory threshold was shown to be a reproducible measure of sensory deficit, increasing parallel to the degree of axonal failure found by conventional methods. This may be useful as a complementary method in assessing peripheral neuropathy. PMID:6323634

  14. A rapid change of the Hercules X-1 pulse profile and high-state duration

    NASA Technical Reports Server (NTRS)

    Soong, Yang; Gruber, Duane E.; Rothschild, Richard E.

    1987-01-01

    Her X-1 has been observed in the 13-180 keV energy range by the HEAO 1 A-4 Low-Energy Detectors during selected phases of the 35 d on-off cycle. During a pointing observation in September 1978, the pulse profile was observed to change continuously from its normal shape to an anomalous double-pulsed form. Moreover, at this time the main-on state, normally of the duration 10 d, was seen to terminate after only 7 d. Since such an anomalous pulse profile has also been reported by Truemper et al. in 1986 during a short-on state, three short-on states in the HEAO 1 data were also investigated. One short-on observation had the sensitivity to detect pulsing, and the observed profile also had an anomalous double-pulsed form. Current models for the 35 d cycle of Her X-1 have been examined, and a model with a neutron star undergoing free precession could not explain the sudden change of pulse profile within 20 hr at the end of a main-on state.

  15. Pulse-duration effect in nonsequential double ionization of Ar atoms

    NASA Astrophysics Data System (ADS)

    Dong, Shansi; Chen, Xiang; Zhang, Jingtao; Ren, Xianghe

    2016-05-01

    Nonsequential double ionization of Ar atoms in intense few-cycle laser pulses is studied by a classical ensemble method. The laser pulses are of trapezoidal shape with one cycle in both ramp on and ramp off. We obtain the cycle-resolved electron dynamics by increasing the optical cycles in the laser pulse one by one. We find that, at the higher laser intensity, the correlated-electron momentum distribution (CMD) in the three-cycle laser pulse exhibits two predominate structures in the first and third quadrants. They are formed by the electron pairs in which the second electron is knocked out by the returning electron in the second cycle. As the pulse duration increases, more electron pairs accumulate in the second and fourth quadrants of the CMDs. In these electron pairs, the second electron is first excited owing to collision with the returning electron and then is ionized by the laser field. By varying the peak intensity, we show the transition of the CMDs from anticorrelation to correlation in three-cycle laser pulses, which disproves that multiple collisions cause the transition.

  16. High-order harmonic generation from laser plasma produced by pulses of different duration

    SciTech Connect

    Ganeev, R. A.; Suzuki, M.; Baba, M.; Kuroda, H.

    2007-08-15

    The high-order harmonic generation was analyzed by interaction of the femtosecond pulses with the laser plasma produced on the surfaces of various targets. The plasma formation was accomplished by the interaction of the prepulse radiation of different pulse duration (160 fs, 1.5 ps, 210 ps, and 20 ns) with the low-Z (lithium, boron, carbon), medium-Z (manganese, zinc, nickel), and high-Z (silver, barium) targets. We showed that plasma formation conditions play a crucial role in harmonic generation and the optimization of this process mostly depends on the energy of prepulse rather than its intensity at the target surface. These studies also demonstrated that the delay between the prepulse and femtosecond pulse is another important parameter, which distinguishes harmonic generation in the cases of the low- and high-Z targets.

  17. Pulse front tilt measurement of femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Dimitrov, Nikolay; Stoyanov, Lyubomir; Stefanov, Ivan; Dreischuh, Alexander; Hansinger, Peter; Paulus, Gerhard G.

    2016-07-01

    In this work we report experimental investigations of an intentionally introduced pulse front tilt on femtosecond laser pulses by using an inverted field correlator/interferometer. A reliable criterion for the precision in aligning (in principle) dispersionless systems for manipulating ultrashort pulses is developed, specifically including cases when the pulse front tilt is a result of a desired spatio-temporal coupling. The results obtained using two low-dispersion diffraction gratings are in good qualitative agreement with the data from a previously developed analytical model and from an independent interferometric measurement.

  18. Millisecond measurement of transport during and after an electroporation pulse.

    PubMed Central

    Prausnitz, M R; Corbett, J D; Gimm, J A; Golan, D E; Langer, R; Weaver, J C

    1995-01-01

    Electroporation involves the application of an electric field pulse that creates transient aqueous pathways in lipid bilayer membranes. Transport through these pathways can occur by different mechanisms during and after a pulse. To determine the time scale of transport and the mechanism(s) by which it occurs, efflux of a fluorescent molecule, calcein, across erythrocyte ghost membranes was measured with a fluorescence microscope photometer with millisecond time resolution during and after electroporation pulses several milliseconds in duration. One of four outcomes was typically observed. Ghosts were: (1) partially emptied of calcein, involving efflux primarily after the pulse; (2) completely emptied of calcein, involving efflux primarily after the pulse; (3) completely emptied of calcein, involving efflux both during and after the pulse; or (4) completely emptied of calcein, involving efflux primarily during the pulse. Partial emptying, involving significant efflux during the pulse, was generally not observed. We conclude that under some conditions transport caused by electroporation occurs predominantly by electrophoresis and/or electroosmosis during a pulse, although under other conditions transport occurs in part or almost completely by diffusion within milliseconds to seconds after a pulse. PMID:7612828

  19. Reduction of the pulse duration of the ultrafast laser pulses of the Two-Photon Laser Scanning Microscopy (2PLSM)

    PubMed Central

    Reshak, Ali Hussain

    2008-01-01

    Background We provide an update of our two-photon laser scanning microscope by compressing or reducing the broadening of the pulse width of ultrafast laser pulses for dispersion precompensation, to enable the pulses to penetrate deeply inside the sample. Findings The broadening comes as the pulses pass through the optical elements. We enhanced and modified the quality and the sharpness of images by enhancing the resolution using special polarizer namely Glan Laser polarizer GL10. This polarizer consists of two prisms separated by air space. This air separation between the two prisms uses to delay the red wavelength when the light leaves the first prism to the air then to second prism. We note a considerable enhancing with using the GL polarizer, and we can see the details of the leaf structure in early stages when we trying to get focus through z-stacks of images in comparison to exactly the same measurements without using GL polarizer. Hence, with this modification we able to reduce the time of exposure the sample to the laser radiation thereby we will reduce the probability of photobleaching and phototoxicity. When the pulse width reduced, the average power of the laser pulses maintained at a constant level. Significant enhancement is found between the two kinds of images of the Two-Photon Excitation Fluorescence (TPEF). Conclusion In summary reduction the laser pulse width allowed to collect more diffraction orders which will used to form the images. The more diffraction orders the higher resolution images. PMID:18710492

  20. System parameters germane to relativistic klystron amplifiers: how the utility of pulse energy depends on pulse duration, the target, and the atmosphere

    NASA Astrophysics Data System (ADS)

    Myers, John M.

    1994-05-01

    Relativistic klystron amplifiers (RKAs) at a variety of carrier wavelengths and pulse durations appear feasible to supply microwave pulses to an array of antennas acting as a beam weapon against targets at or above 100 km in altitude. In order to avoid voltage breakdown in the atmosphere, the array area must be large enough to converge the beam, producing a higher energy flux on target than at intermediate altitudes susceptible to breakdown. The area required depends on the physics of atmospheric ionization and on the pulse duration and the carrier wavelength of the RKA. A quantitative statement of the dependence of array area on relevant parameters is presented. The energy per RKA pulse that is usable without delay lines is determined here as a function of RKA pulse duration and wavelength. Changing the pulse length from 160 ns to 1 microsecond(s) and shortening the wavelength raise the energy usable without delay lines by a factor of 1000.

  1. Laser pulse duration dependence of the low-energy structure in strong field ionization

    NASA Astrophysics Data System (ADS)

    Lai, Yu Hang; Zhang, Kaikai; Blaga, Cosmin; Xu, Junliang; Agostini, Pierre; Dimauro, Louis; Schmidt, Bruno; Légaré, François; The Ohio State University Team; Institut National de la Recherche Scientifique Team

    2015-05-01

    Low-energy structure (LES) in strong field ionization is a spike-like feature appearing in the low energy part (a few eV) of photoelectron spectra along the laser polarization. It has been observed in rare gas atoms and diatomic molecules. In the classical picture, the formation of LES is due to the Coulomb interaction between the ionized electron and its parent ion via the process of multiple forward scattering, which can happen only if the electron is ionized with a small drift momentum. We have studied the LES in rare gas atoms with few-cycle laser pulses centered at 1800nm. We observed that the LES peak shifts to lower energy as the pulse duration decreases from 5 down to 2 optical cycles, which is in qualitative agreement with classical-trajectory Monte Carlo simulations. Classically, the shift could be attributed to the dependence of the ratio between the field amplitude of the central cycle and the adjacent cycle on the pulse duration. Our data support the classical nature of the LES.

  2. Efficient generation of mode-locked pulses in Nd:YVO4 with a pulse duration adjustable between 34 ps and 1 ns.

    PubMed

    Lührmann, Markus; Theobald, Christian; Wallenstein, Richard; L'huillier, Johannes A

    2009-04-13

    We report on the generation of highly stable active continuous mode-locked pulses in diode pumped Nd:YVO(4) with an adjustable pulse duration between 34 ps and 1 ns. With this laser an average output power of up to 7.3 W with an excellent stability and beam quality with a M(2)-value of < 1.1 is obtained. For all pulse durations the pulses were within a factor of 1.15 above the Fourier limit. Due to these characteristics the presented system is an attractive oscillator for OPCPA concepts. PMID:19365440

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

    SciTech Connect

    Tamura, Ayaka Matsumoto, Ayumu; Nishi, Naoya; Sakka, Tetsuo; Nakajima, Takashi; Ogata, Yukio H.; Fukami, Kazuhiro

    2015-01-14

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

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

    NASA Astrophysics Data System (ADS)

    Hüller, Stefan; Afeyan, Bedros

    2013-11-01

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

  5. Infrared laser damage thresholds for skin at wavelengths from 0.810 to 1.54 microns for femto-to-microsecond pulse durations

    NASA Astrophysics Data System (ADS)

    Cain, Clarence P.; Roach, William P.; Stolarski, David J.; Noojin, Gary D.; Kumru, Semih S.; Stockton, Kevin L.; Zohner, Justin J.; Rockwell, Benjamin A.

    2007-02-01

    In this paper we report on our combined measurements of the visible lesion thresholds for porcine skin for wavelengths in the infrared from 810 nm at 44 fs to 1318 nm at pulse durations of 50 ns and 350μs to 1540 nm including pulse durations of 31 ns and 600 μs. We also measure thresholds for various spot sizes from less than 1 mm to 5 mm in diameter. All three wavelengths and five pulse durations are used extensively in research and the military. We compare these minimum visible lesion thresholds with ANSI standards set for maximum permissible exposures in the infrared wavelengths. We have measured non-linear effects at the laser-tissue interface for pulse durations below 1μs and determined that damage at these short pulse durations are usually not thermal effects. Damage at the skin surface may include acoustical effects, laser ablation and/or low-density plasma effects, depending on the wavelength and pulse duration. Also the damage effects may be short-lived and disappear within a few days or may last for much longer time periods including permanent discolorations. For femtosecond pulses at 810 nm, damage was almost instant and at 1 hour had an ED50 of 8.2 mJ of pulse energy. After 24 hours, most of the lesions disappeared and the ED50 increased by almost a factor of 3 to 21.3 mJ. There was a similar trend for the 1.318 μ laser for spot sizes of 2 mm and 5 mm where the ED50 was larger after 24 hours. However, for the 1.54 μ laser with a spot size of 5 mm, the ED50 actually decreased by a small amount; from 6.3 Jcm-2 to 6.1 Jcm-2 after 24 hours. Thresholds also decreased for the 1314 nm laser at 350 μs for spot sizes of 0.7 mm and 1.3 mm diameter after 24 hours. Different results were obtained for the 1540 nm laser at 600 μs pulse durations where the ED50 decreased for spot sizes 1 mm and below, but increased slightly for the 5 mm diameter spot size from 6.4 Jcm-2 to 7.4 Jcm-2

  6. Optical Parameter Variability in Laser Nerve Stimulation: A Study of Pulse Duration, Repetition Rate, and Wavelength

    PubMed Central

    Walsh, Joseph T.; Jansen, E. Duco; Bendett, Mark; Webb, Jim; Ralph, Heather; Richter, Claus-Peter

    2012-01-01

    Pulsed lasers can evoke neural activity from motor as well as sensory neurons in vivo. Lasers allow more selective spatial resolution of stimulation than the conventional electrical stimulation. To date, few studies have examined pulsed, mid-infrared laser stimulation of nerves and very little of the available optical parameter space has been studied. In this study, a pulsed diode laser, with wavelength between 1.844–1.873 μm, was used to elicit compound action potentials (CAPs) from the auditory system of the gerbil. We found that pulse durations as short as 35 μs elicit a CAP from the cochlea. In addition, repetition rates up to 13 Hz can continually stimulate cochlear spiral ganglion cells for extended periods of time. Varying the wavelength and, therefore, the optical penetration depth, allowed different populations of neurons to be stimulated. The technology of optical stimulation could significantly improve cochlear implants, which are hampered by a lack of spatial selectivity. PMID:17554829

  7. Laser-fired contact formation on metallized and passivated silicon wafers under short pulse durations

    NASA Astrophysics Data System (ADS)

    Raghavan, Ashwin S.

    The objective of this work is to develop a comprehensive understanding of the physical processes governing laser-fired contact (LFC) formation under microsecond pulse durations. Primary emphasis is placed on understanding how processing parameters influence contact morphology, passivation layer quality, alloying of Al and Si, and contact resistance. In addition, the research seeks to develop a quantitative method to accurately predict the contact geometry, thermal cycles, heat and mass transfer phenomena, and the influence of contact pitch distance on substrate temperatures in order to improve the physical understanding of the underlying processes. Finally, the work seeks to predict how geometry for LFCs produced with microsecond pulses will influence fabrication and performance factors, such as the rear side contacting scheme, rear surface series resistance and effective rear surface recombination rates. The characterization of LFC cross-sections reveals that the use of microsecond pulse durations results in the formation of three-dimensional hemispherical or half-ellipsoidal contact geometries. The LFC is heavily alloyed with Al and Si and is composed of a two-phase Al-Si microstructure that grows from the Si wafer during resolidification. As a result of forming a large three-dimensional contact geometry, the total contact resistance is governed by the interfacial contact area between the LFC and the wafer rather than the planar contact area at the original Al-Si interface within an opening in the passivation layer. By forming three-dimensional LFCs, the total contact resistance is significantly reduced in comparison to that predicted for planar contacts. In addition, despite the high energy densities associated with microsecond pulse durations, the passivation layer is well preserved outside of the immediate contact region. Therefore, the use of microsecond pulse durations can be used to improve device performance by leading to lower total contact resistances

  8. Alignment and pulse-duration effects in two-photon double ionization of H2 by femtosecond XUV laser pulses

    NASA Astrophysics Data System (ADS)

    Guan, Xiaoxu; Bartschat, Klaus; Schneider, Barry I.; Koesterke, Lars

    2014-10-01

    We present calculations for the dependence of the two-photon double ionization (DI) of H2 on the relative orientation of the linear laser polarization to the internuclear axis and the length of the pulse. We use the fixed-nuclei approximation at the equilibrium distance of 1.4 a0, where a0=0.529 ×10-10m is the Bohr radius. Central photon energies cover the entire direct DI domain from 26.5 to 34.0 eV. In contrast to the parallel geometry studied earlier [X. Guan, K. Bartschat, B. I. Schneider, and L. Koesterke, Phys. Rev. A 83, 043403 (2011), 10.1103/PhysRevA.83.043403], the effect of the pulse duration is almost negligible for the case when the two axes are perpendicular to each other. This is a consequence of the symmetry rules for dipole excitation in the two cases. In the parallel geometry, doubly excited states of 1Σu+ symmetry affect the cross section, while in the perpendicular geometry only much longer-lived 1Πu states are present. This accounts for the different convergence patterns observed in the calculated cross sections as a function of the pulse length. When the photon energy approaches the threshold of sequential DI, a sharp increase of the generalized total cross section (GTCS) with increasing pulse duration is also observed in the perpendicular geometry, very similar to the case of the molecular axis being oriented along the laser polarization direction. Our results differ from those of Colgan et al. [J. Colgan, M. S. Pindzola, and F. Robicheaux, J. Phys. B 41, 121002 (2008), 10.1088/0953-4075/41/12/121002] and Morales et al. [F. Morales, F. Martín, D. A. Horner, T. N. Rescigno, and C. W. McCurdy, J. Phys. B 42, 134013 (2009), 10.1088/0953-4075/42/13/134013], but are in excellent agreement with the GTCSs of Simonsen et al. [A. S. Simonsen, S. A. Sørngård, R. Nepstad, and M. Førre, Phys. Rev. A 85, 063404 (2012), 10.1103/PhysRevA.85.063404] over the entire domain of direct DI.

  9. Effect of pulse duration on resonant heating of laser-irradiated argon and deuterium clusters.

    PubMed

    Gupta, Ayush; Antonsen, T M; Taguchi, T; Palastro, J

    2006-10-01

    We study the effect of pulse duration on the heating of single van der Waals bound argon and deuterium clusters by a strong laser field using a two-dimensional (2D) electrostatic particle-in-cell (PIC) code in the range of laser-cluster parameters such that kinetic as well as hydrodynamic effects are active. Heating is dominated by a collisionless resonant absorption process that involves energetic electrons transiting through the cluster. A size-dependent intensity threshold defines the onset of this resonance [T. Taguchi, Physical Review Letters, 92, 20 (2004)]. It is seen that increasing the laser pulse duration lowers this intensity threshold and the energetic electrons take multiple laser periods to transit the cluster instead of one laser period. Our simulations also show that strong electron heating is accompanied by the generation of a high-energy peak in the ion energy distribution function. We also calculate the yield of thermonuclear fusion neutrons from exploding deuterium clusters using the PIC model with periodic boundary conditions that allows for the interaction of ions from neighboring clusters. PMID:17155183

  10. Dependence of core heating properties on heating pulse duration and intensity

    NASA Astrophysics Data System (ADS)

    Johzaki, Tomoyuki; Nagatomo, Hideo; Sunahara, Atsushi; Cai, Hongbo; Sakagami, Hitoshi; Mima, Kunioki

    2009-11-01

    In the cone-guiding fast ignition, an imploded core is heated by the energy transport of fast electrons generated by the ultra-intense short-pulse laser at the cone inner surface. The fast core heating (˜800eV) has been demonstrated at integrated experiments with GEKKO-XII+ PW laser systems. As the next step, experiments using more powerful heating laser, FIREX, have been started at ILE, Osaka university. In FIREX-I (phase-I of FIREX), our goal is the demonstration of efficient core heating (Ti ˜ 5keV) using a newly developed 10kJ LFEX laser. In the first integrated experiments, the LFEX laser is operated with low energy mode (˜0.5kJ/4ps) to validate the previous GEKKO+PW experiments. Between the two experiments, though the laser energy is similar (˜0.5kJ), the duration is different; ˜0.5ps in the PW laser and ˜ 4ps in the LFEX laser. In this paper, we evaluate the dependence of core heating properties on the heating pulse duration on the basis of integrated simulations with FI^3 (Fast Ignition Integrated Interconnecting) code system.

  11. Pulse duration determines levels of Hsp70 induction in tissues following laser irradiation

    NASA Astrophysics Data System (ADS)

    Mackanos, Mark A.; Contag, Christopher H.

    2011-07-01

    Induction of heat shock protein (Hsp) expression correlates with cytoprotection, reduced tissue damage, and accelerated healing in animal models. Since Hsps are transcriptionally activated in response to stress, they can act as stress indicators in burn injury or surgical procedures that produce heat and thermal change. A fast in vivo readout for induction of Hsp transcription in tissues would allow for the study of these proteins as therapeutic effect mediators and reporters of thermal stress/damage. We used a transgenic reporter mouse in which a luciferase expression is controlled by the regulatory region of the inducible 70 kilodalton (kDa) Hsp as a rapid readout of cellular responses to laser-mediated thermal stress/injury in mouse skin. We assessed the pulse duration dependence of the Hsp70 expression after irradiation with a CO2 laser at 10.6 μm in wavelength over a range of 1000 to 1 ms. Hsp70 induction varied with changes in laser pulse durations and radiant exposures, which defined the ranges at which thermal activation of Hsp70 can be used to protect cells from subsequent stress, and reveals the window of thermal stress that tissues can endure.

  12. Thermal measurements of short-duration CO2 laser resurfacing

    NASA Astrophysics Data System (ADS)

    Harris, David M.; Fried, Daniel; Reinisch, Lou; Bell, Thomas; Lyver, Rex

    1997-05-01

    The thermal consequences of a 100 microsecond carbon-dioxide laser used for skin resurfacing were examined with infrared radiometry. Human skin was evaluated in a cosmetic surgery clinic and extirpated rodent skin was measured in a research laboratory. Thermal relaxation following single pulses of in vivo human and ex vivo animal skin were quantitatively similar in the 30 - 1000 msec range. The thermal emission from the area of the irradiated tissue increased monotonically with increasing incident laser fluence. Extremely high peak temperatures during the 100 microsecond pulse are attributed to plume incandescence. Ejecta thermal emission may also contribute to our measurements during the first several msecs. The data are combined into a thermal relaxation model. Given known coefficients, and adjusting tissue absorption to reflect a 50% water content, and thermal conductivity of 2.3 times that of water, the measured (both animal back and human forearm) and calculated values coincide. The high thermal conductance suggests preferential thermal conduction along the protein matrix. The clinical observation of a resurfacing procedure clearly shows thermal overlap and build-up is a result of sequential, adjacent pulses. A decrease of 4 - 6 degrees Celsius in surface temperature at the treatment site that appeared immediately post-Tx and gradually diminished over several days is possibly a sign of dermal convective and/or evaporative cooling.

  13. Successful management of a refractory case of postoperative herniorrhaphy pain with extended duration pulsed radiofrequency

    PubMed Central

    Thapa, D; Ahuja, V; Verma, P; Das, C

    2016-01-01

    Chronic postsurgical pain (CPSP) is a distressful condition following hernia surgery. A 25-year-old, 55 kg male patient presented with severe pain on the right side of the lower abdomen that radiated to the testicle and the inner side of the thigh. Patient was symptomatic since 5 months following inguinal herniorrhaphy surgery. The pain was not relieved with pharmacological and interventional nerve blocks. An ultrasound-guided ilioinguinal-iliohypogastric (II-IH) block with extended duration (42°C, four cycles of 120 s each) pulsed radiofrequency (PRF) and a diagnostic genital branch of genitofemoral nerve (GGFN) block provided pain relief. After 1-month, an extended duration PRF in GGFN resulted in complete resolution of symptoms. During a regular follow-up of 9 months, patient reported an improved quality-of-life. We believe the successful management of CPSP following hernia repair with single extended duration PRF of II-IH and GGFN has not been described in the literature. PMID:26955321

  14. Duration of an intense laser pulse can determine the breakage of multiple chemical bonds

    NASA Astrophysics Data System (ADS)

    Xie, Xinhua; Lötstedt, Erik; Roither, Stefan; Schöffler, Markus; Kartashov, Daniil; Midorikawa, Katsumi; Baltuška, Andrius; Yamanouchi, Kaoru; Kitzler, Markus

    2015-08-01

    Control over the breakage of a certain chemical bond in a molecule by an ultrashort laser pulse has been considered for decades. With the availability of intense non-resonant laser fields it became possible to pre-determine femtosecond to picosecond molecular bond breakage dynamics by controlled distortions of the electronic molecular system on sub-femtosecond time scales using field-sensitive processes such as strong-field ionization or excitation. So far, all successful demonstrations in this area considered only fragmentation reactions, where only one bond is broken and the molecule is split into merely two moieties. Here, using ethylene (C2H4) as an example, we experimentally investigate whether complex fragmentation reactions that involve the breakage of more than one chemical bond can be influenced by parameters of an ultrashort intense laser pulse. We show that the dynamics of removing three electrons by strong-field ionization determines the ratio of fragmentation of the molecular trication into two respectively three moieties. We observe a relative increase of two-body fragmentations with the laser pulse duration by almost an order of magnitude. Supported by quantum chemical simulations we explain our experimental results by the interplay between the dynamics of electron removal and nuclear motion.

  15. Improving the spatial resolution of epiretinal implants by increasing stimulus pulse duration.

    PubMed

    Weitz, Andrew C; Nanduri, Devyani; Behrend, Matthew R; Gonzalez-Calle, Alejandra; Greenberg, Robert J; Humayun, Mark S; Chow, Robert H; Weiland, James D

    2015-12-16

    Retinal prosthetic implants are the only approved treatment for retinitis pigmentosa, a disease of the eye that causes blindness through gradual degeneration of photoreceptors. An array of microelectrodes triggered by input from a camera stimulates surviving retinal neurons, with each electrode acting as a pixel. Unintended stimulation of retinal ganglion cell axons causes patients to see large oblong shapes of light, rather than focal spots, making it difficult to perceive forms. To address this problem, we performed calcium imaging in isolated retinas and mapped the patterns of cells activated by different electrical stimulation protocols. We found that pulse durations two orders of magnitude longer than those typically used in existing implants stimulated inner retinal neurons while avoiding activation of ganglion cell axons, thus confining retinal responses to the site of the electrode. Multielectrode stimulation with 25-ms pulses can pattern letters on the retina corresponding to a Snellen acuity of 20/312. We validated our findings in a patient with an implanted epiretinal prosthesis by demonstrating that 25-ms pulses evoke focal spots of light. PMID:26676610

  16. Duration of an intense laser pulse can determine the breakage of multiple chemical bonds.

    PubMed

    Xie, Xinhua; Lötstedt, Erik; Roither, Stefan; Schöffler, Markus; Kartashov, Daniil; Midorikawa, Katsumi; Baltuška, Andrius; Yamanouchi, Kaoru; Kitzler, Markus

    2015-01-01

    Control over the breakage of a certain chemical bond in a molecule by an ultrashort laser pulse has been considered for decades. With the availability of intense non-resonant laser fields it became possible to pre-determine femtosecond to picosecond molecular bond breakage dynamics by controlled distortions of the electronic molecular system on sub-femtosecond time scales using field-sensitive processes such as strong-field ionization or excitation. So far, all successful demonstrations in this area considered only fragmentation reactions, where only one bond is broken and the molecule is split into merely two moieties. Here, using ethylene (C2H4) as an example, we experimentally investigate whether complex fragmentation reactions that involve the breakage of more than one chemical bond can be influenced by parameters of an ultrashort intense laser pulse. We show that the dynamics of removing three electrons by strong-field ionization determines the ratio of fragmentation of the molecular trication into two respectively three moieties. We observe a relative increase of two-body fragmentations with the laser pulse duration by almost an order of magnitude. Supported by quantum chemical simulations we explain our experimental results by the interplay between the dynamics of electron removal and nuclear motion. PMID:26271602

  17. Efficient excitation of a mesospheric sodium laser guide star by intermediate-duration pulses

    SciTech Connect

    Morris, J.R.

    1994-02-01

    Calculations of backscatter emission of meosopheric sodium atoms in a laser guide star that is excited by pulses ranging from 30-ns to 0.9-{mu}s duration are described. The efficient use of such pulses at saturating irradiance values is shown to require {approximately} 3 GHz of spectral broadening to provide access to the full absorption spectrum of the D{sub 2} line. The broadening is provided by frequency modulation. A set of density matrices was used to account for all 24 hyperfine states and inhomogeneous Doppler broadening. At the broadband (3-GHz) saturation irradiance of 4 W/cm{sup 2}, both linearly and circularly polarized laser beams are shown to produce emission rates exceeding 60% of the maximum possible rate-equation rate for the 0.9-{mu}s pulses. As expected, circular polarization produced more backscatter than did linear polarization, but the enhancement never exceeded 1/3 in the calculations that are reported. A brief estimate of state precession in the Earth`s magnetic field suggests that achieving even this enhancement will require that the time scale for optical pumping be held to less than 1 {mu}s, which will require the use of irradiances greater than 0.7 W/cm{sup 2} and spectral coverage of the full 3-GHz hyperfine-plus-Doppler absorption profile, at least until most of the population is pumped out of the F = 1 ground states. 46 refs., 24 figs., 5 tabs.

  18. The effect of pulse duration on laser-induced damage by 1053-nm light in potassium dihydrogen phosphate crystals

    SciTech Connect

    Cross, D A; Braunstein, M R; Carr, C W

    2006-11-27

    Laser induced damage in potassium dihydrogen phosphate (KDP) has previously been shown to depend significantly on pulse duration for 351-nm Gaussian pulses. In this work we studied the properties of damage initiated by 1053-nm temporally Gaussian pulses with 10ns and 3ns FWHM durations. Our results indicate that the number of damage sites induced by 1053-nm light scales with pulse duration ({tau}) as ({tau}{sub 1}/{tau}{sub 2}){sup 0.17} in contrast to the previously reported results for 351-nm light as ({tau}{sub 1}/{tau}{sub 2}){sup 0.35}. This indicates that damage site formation is significantly less probable at longer wavelengths for a given fluence.

  19. Attosecond pulses measured from the attosecond lighthouse

    NASA Astrophysics Data System (ADS)

    Hammond, T. J.; Brown, Graham G.; Kim, Kyung Taec; Villeneuve, D. M.; Corkum, P. B.

    2016-03-01

    The attosecond lighthouse is a method of using ultrafast wavefront rotation with high-harmonic generation to create a series of coherent, spatially separated attosecond pulses. Previously, temporal measurements by photoelectron streaking characterized isolated attosecond pulses created by manipulating the single-atom response. The attosecond lighthouse, in contrast, generates a series of pulses that spatially separate and become isolated by propagation. Here, we show that ultrafast wavefront rotation maintains the single-atom response (in terms of temporal character) of an isolated attosecond pulse over two octaves of bandwidth. Moreover, we exploit the unique property of the attosecond lighthouse—the generation of several isolated pulses—to measure the three most intense pulses. These pulses each have a unique spectrum and spectral phase.

  20. Reliability assessment for pulse wave measurement using artificial pulse generator.

    PubMed

    Chang, Chi-Wei; Wang, Wei-Kung

    2015-04-01

    This study aimed to assess intrinsic reliabilities of devices for pulse wave measurement (PWM). An artificial pulse generator system was constructed to create a periodic pulse wave. The stability of the periodic output was tested by the DP103 pressure transducer. The pulse generator system was then used to evaluate the TD01C system. Test-re-test and inter-device reliability assessments were conducted on the TD01C system. First, 11 harmonic components of the pulse wave were calculated using Fourier series analysis. For each harmonic component, coefficient of variation (CV), intra-class correlation coefficient (ICC) and Bland-Altman plot were used to determine the degree of reliability of the TD01C system. In addition, device exclusion criteria were pre-specified to improve consistency of devices. The artificial pulse generator system was stable to evaluate intrinsic reliabilities of devices for PWM (ICCs > 0.95, p < 0.001). TD01C was reliable for repeated measurements (ICCs of test-re-test reliability > 0.95, p < 0.001; CVs all < 3%). Device exclusion criteria successfully excluded the device with defect; therefore, the criteria reduced inter-device CVs of harmonics and improved consistency of the selected devices for all harmonic components. This study confirmed the feasibility of intrinsic reliability assessment of devices for PWM using an artificial pulse generator system. Moreover, potential novel findings on the assessment combined with device exclusion criteria could be a useful method to select the measuring devices and to evaluate the qualities of them in PWM. PMID:25693606

  1. Exceptions to Hick's law: explorations with a response duration measure.

    PubMed

    Longstreth, L E; el-Zahhar, N; Alcorn, M B

    1985-12-01

    Five experiments used a new response-duration measure in explorations of the conditions necessary for confirmation of Hick's law. Hick's law states that reaction time increases logarithmically with number of choices. Exceptions to the law, venerable as it is, have been reported. They have always included the following conditions: a verbal response; a familiar stimulus with a single dominant name; and a large number of practice trials. These conditions have carried a heavy explanatory burden in accounting for the anamolous results. The present studies use none of these conditions and yet manage to replicate the anamolous result of a very shallow slope across set size, a slope less than one-tenth the usual value. This was accomplished by using a novel task in which the initial component of the response is the same for all stimuli (depression of a single response key) but the termination of the response is different (different durations for each stimulus). Using this task, a slope in the neighborhood of 15 ms per bit of stimulus uncertainty is found, as compared with the usual value of about 150 ms. A number of possible explanations are examined. Among the most important are the possibilities that response overlap is the critical factor (i.e., duration errors overlap); possible stimuli are simply ignored when more than one is involved; and the duration decision is made after the reaction-time interval rather than during it. All three possibilities, as well as some others, are found to be inconsistent with the various experimental outcomes. Instead, a new theory of choice reaction time is presented, which emphasizes the nature of the S-R code that is assumed to represent various reaction-time tasks. This theory leads to a new "law" that is put forward as a replacement for Hick's law. It is RT = a + b(1 - N-1). PMID:2934496

  2. All solid-state mode-locked flashlamp pumped Nd:YAG laser system with selectable pulse duration

    NASA Astrophysics Data System (ADS)

    Kubecek, Vaclav; Diels, Jean-Claude; Stintz, Andreas; Jelinkova, Helena; Dombrovsky, Andrej; Cech, Miroslav

    2005-04-01

    All solid state mode-locked flashlamp pumped Nd:YAG laser system with selectable pulse duration was developed based on the oscillator where a single semiconductor structure containing a multiple-quantum-well was used as a saturable absorber for mode-locking, and energy limiter for passive negative feedback. Single pulse selection from various parts of extended 200 ns long Q-switched pulse train enables the changing of pulse duration before entering into three stages of laser amplifiers. Using of additional acousto-optic mode-locker, stability enhancement of the output pulses was obtained and the amplitude fluctuations were reduced below 5%. The exploitation of the solid state saturable absorber and limiter integrated in the single element improved significantly the long term characteristics of the laser system which can be therefore used for various applications as a satellite laser ranging, spectroscopy, or medicine.

  3. Laser-induced damage measurements with 266-nm pulses

    NASA Astrophysics Data System (ADS)

    Deaton, T. F.; Smith, W. L.

    1980-07-01

    Results of a survey of laser-induced damage thresholds for optical components at 266-nm are reported. The thresholds were measured at two pulse durations; 0.150 ns and 1.0 ns. The 30 samples tested include four commercial dielectric reflectors, three metallic reflectors, two anti-reflection films, a series of eight half-wave oxide and fluoride films, and twelve bare surfaces (fluoride crystals, silica, sapphire, BK-7 glass, cesium dideuterium arsenate and potassium dihydrogen phosphate). The 266-nm pulses were obtained by frequency-quadrupling a Nd:YAG, glass laser. Equivalent plane imagery and calorimetry were used to measure the peak fluence of each of the UV pulses with an accuracy of + or - of 15%; the uncertainty in the threshold determinations is typically + or - 30%.

  4. Effect of pulse duration on plasmonic enhanced ultrafast laser-induced bubble generation in water

    NASA Astrophysics Data System (ADS)

    Lachaine, R.; Boulais, E.; Bourbeau, E.; Meunier, M.

    2013-07-01

    Bubbles generated in water by focusing femtosecond and picosecond laser pulses in the presence of 100 nm gold nanoparticles have been investigated in the fluence range usually used for efficient cell transfection (100-200 mJ/cm2). Since resulting bubbles are at the nanoscale, direct observation using optical microscopy is not possible. An optical in-situ method has been developed to monitor the time-resolved variation in the extinction cross-section of an irradiated nanoparticle solution sample. This method is used to measure the bubbles lifetime and deduce their average diameter. We show that bubbles generated with femtosecond pulses (40-500 fs) last two times longer and are larger in average than those generated with picosecond pulses (0.5-5 ps). Controlling those bubble properties is necessary for optimizing off-resonance plasmonic enhanced ultrafast laser cell transfection.

  5. Laser processing of glass fiber reinforced thermoplastics with different wavelengths and pulse durations

    NASA Astrophysics Data System (ADS)

    Schilling, N.; Krupop, B.; Klotzbach, U.

    2015-03-01

    In this paper, laser processing of fiber reinforced thermoplastics is investigated with different laser sources. Aim of the study is to determine the process windows in which selective ablation of polymer matrix and homogenous ablation of matrix and fiber occurs. To reach this, laser sources with different wavelengths (10600 nm, 1064 nm and 532 nm) and pulse durations in μs, ns and ps regime are compared on their ablation behavior of natural and black colored glass fiber reinforced polypropylene. Best results were achieved with ns lasers with IR wavelength at black colored material. At this parameter combination a wide process window can be shown where no damage of the reinforcing fibers happens.

  6. Effect of Pulse Duration on Polytetrafluoroethylene Shocked above the Crystalline Phase II-Iii Transition

    NASA Astrophysics Data System (ADS)

    Brown, E. N.; Gray, G. T.; Rae, P. J.; Trujillo, C. P.; Bourne, N. K.

    2007-12-01

    We present an experimental study of crystalline structure evolution of polytetrafluoroethylene (PTFE) due to pressure-induced phase transitions in a semi-crystalline polymer using soft-recovery, shock-loading techniques coupled with mechanical and chemical post-shock analysis. Gas-launched, plate impact experiments have been performed on pedigreed PTFE 7C, mounted in momentum-trapped, shock assemblies, with impact pressures above and below the phase II to phase III crystalline transition. Below the phase transition only subtle changes were observed in the crystallinity, microstructure, and mechanical response of PTFE. Shock loading of PTFE 7C above the phase II-III transition was seen to cause both an increase in crystallinity from 38% to ˜53% and a finer crystalline microstructure, and changed the yield and flow stress behavior. We particularly focus on the effect of pulse duration on the microstructure evolution.

  7. Effect of Pulse Duration on Polytetrafluoroethylene Shocked Above the Crystalline Phase II--III Transition

    NASA Astrophysics Data System (ADS)

    Brown, Eric N.; Gray, George T., III; Rae, Philip J.; Trujillo, Carl P.; Bourne, Neil K.

    2007-06-01

    We present an experimental study of crystalline structure evolution of polytetrafluoroethylene (PTFE) due to pressure-induced phase transitions in a semi-crystalline polymer using soft-recovery, shock-loading techniques coupled with mechanical and chemical post-shock analysis. Gas-launched, plate impact experiments have been performed on pedigreed PTFE 7C, mounted in momentum-trapped, shock assemblies, with impact pressures above and below the phase II to phase III crystalline transition. Below the phase transition only subtle changes were observed in the crystallinity, microstructure, and mechanical response of PTFE. Shock loading of PTFE 7C above the phase II--III transition was seen to cause both an increase in crystallinity from 38% to ˜53% (by Differential Scanning Calorimetry, DSC) and a finer crystalline microstructure, and changed the yield and flow stress behavior. We particularly focus on the effect of pulse duration on the microstructure evolution.

  8. Materials processing by use of a Ti:Sapphire laser with automatically-adjustable pulse duration

    NASA Astrophysics Data System (ADS)

    Kamata, M.; Imahoko, T.; Ozono, K.; Obara, M.

    We have developed an automatic pulsewidth-adjustable femtosecond Ti:Sapphire laser system that can generate an output of 50 fs-1 ps in duration, and sub-mJ/pulse at a repetition rate of 1 kpps. The automatic pulse compressor enables one to control the pulsewidth in the range of 50 fs-1 ps by use of a personal computer (PC). The compressor can change the distance in-between and the tilt angle of the grating pairs by use of two stepping motors and two piezo-electric transducer(PZT) driven actuators, respectively. Both are controlled by a PC. Therefore, not only control of the pulsewidth, but also of the optical chirp becomes easy. By use of this femtosecond laser system, we fabricated a waveguide in fused quartz. The numerical aperture is chosen to 0.007 to loosely focus the femtosecond laser. The fabricated waveguides are well controllable by the incident laser pulsewidth. We also demonstrated the ablation processing of hydroxyapatite (Ca10(PO4)6(OH)2), which is a key component of human tooth and human bone for orthopedics and dentistry. With pulsewidth tunable output from 50 fs through 2 ps at 1 kpps, the chemical content of calcium and phosphorus is kept unchanged before and after 50-fs-2-ps laser ablation. We also demonstrated the precise ablation processing of human tooth enamel with 2 ps Ti:Sapphire laser.

  9. Compact femtosecond electron diffractometer with 100 keV electron bunches approaching the single-electron pulse duration limit

    SciTech Connect

    Waldecker, Lutz Bertoni, Roman; Ernstorfer, Ralph

    2015-01-28

    We present the design and implementation of a highly compact femtosecond electron diffractometer working at electron energies up to 100 keV. We use a multi-body particle tracing code to simulate electron bunch propagation through the setup and to calculate pulse durations at the sample position. Our simulations show that electron bunches containing few thousands of electrons per bunch are only weakly broadened by space-charge effects and their pulse duration is thus close to the one of a single-electron wavepacket. With our compact setup, we can create electron bunches containing up to 5000 electrons with a pulse duration below 100 fs on the sample. We use the diffractometer to track the energy transfer from photoexcited electrons to the lattice in a thin film of titanium. This process takes place on the timescale of few-hundred femtoseconds and a fully equilibrated state is reached within 1 ps.

  10. Spectral Measurements of Pulse Solar Simulators

    SciTech Connect

    Cannon, T. W.

    1998-11-12

    Spectral measurements of pulse solar simulators are used to quantify the wavelength-dependant characteristics of the light. Because every PV device has a unique spectral response, it is important to know the spectral irradiance and to periodically monitor the spectra for changes. Measurements are made at the National Renewable Energy Laboratory (NREL) using several different techniques including the NREL-developed Pulse Analysis Spectroradiometer System (PASS).

  11. A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br2 down to 13 μs

    NASA Astrophysics Data System (ADS)

    Lam, Jessica; Rennick, Christopher J.; Softley, Timothy P.

    2015-05-01

    A chopper wheel construct is used to shorten the duration of a molecular beam to 13 μs. Molecular beams seeded with NO or with Br2 and an initial pulse width of ≥200 μs were passed through a spinning chopper wheel, which was driven by a brushless DC in vacuo motor at a range of speeds, from 3000 rpm to 80 000 rpm. The resulting duration of the molecular-beam pulses measured at the laser detection volume ranged from 80 μs to 13 μs and was the same for both NO and Br2. The duration is consistent with a simple analytical model, and the minimum pulse width measured is limited by the spreading of the beam between the chopper and the detection point as a consequence of the longitudinal velocity distribution of the beam. The setup adopted here effectively eliminates buildup of background gas without the use of a differential pumping stage, and a clean narrow pulse is obtained with low rotational temperature.

  12. A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br{sub 2} down to 13 μs

    SciTech Connect

    Lam, Jessica; Rennick, Christopher J.; Softley, Timothy P.

    2015-05-15

    A chopper wheel construct is used to shorten the duration of a molecular beam to 13 μs. Molecular beams seeded with NO or with Br{sub 2} and an initial pulse width of ≥200 μs were passed through a spinning chopper wheel, which was driven by a brushless DC in vacuo motor at a range of speeds, from 3000 rpm to 80 000 rpm. The resulting duration of the molecular-beam pulses measured at the laser detection volume ranged from 80 μs to 13 μs and was the same for both NO and Br{sub 2}. The duration is consistent with a simple analytical model, and the minimum pulse width measured is limited by the spreading of the beam between the chopper and the detection point as a consequence of the longitudinal velocity distribution of the beam. The setup adopted here effectively eliminates buildup of background gas without the use of a differential pumping stage, and a clean narrow pulse is obtained with low rotational temperature.

  13. Exact analysis of particle dynamics in combined field of finite duration laser pulse and static axial magnetic field

    SciTech Connect

    Sagar, Vikram; Sengupta, Sudip; Kaw, Predhiman

    2012-11-15

    Dynamics of a charged particle is studied in the field of a relativistically intense linearly polarized finite duration laser pulse in the presence of a static axial magnetic field. For a finite duration laser pulse whose temporal shape is defined by Gaussian profile, exact analytical expressions are derived for the particle trajectory, momentum, and energy as function of laser phase. From the solutions, it is shown that, unlike for the monochromatic plane wave case, resonant phase locking time between the particle and laser pulse is finite. The net energy transferred to the particle does not increase monotonically but tends to saturate. It is further shown that appropriate tuning of cyclotron frequency of the particle with the characteristic frequency in the pulse spectrum can lead to the generation of accelerated particles with variable energies in MeV-TeV range.

  14. Effects of laser pulse duration and intensity on Coulomb explosion of CO2: Signatures of charge-resonance enhanced ionization

    NASA Astrophysics Data System (ADS)

    Litvinyuk, Igor V.; Bocharova, Irina; Sanderson, Joseph; Kieffer, Jean-Claude; Légaré, François

    2009-11-01

    We studied laser-induced Coulomb explosion of CO2 by full triple-coincidence momentum resolved detection of resulting ion fragments. From the coincidence momentum data we can reconstruct molecular geometry immediately before explosion. We observe the dynamics of Coulomb explosion by comparing reconstructed CO2 geometries for different Ti:Sapphire laser pulse durations (at the same intensity) ranging from few cycles (7 fs) to 200 fs. We conclude that for longer pulse durations (>=100 fs) Coulomb explosion proceeds through the enhanced ionization mechanism taking place at the critical O-O distance of 8 a.u., similarly to well known charge-resonance enhanced ionization (CREI) in H2.

  15. Systematic Effects on Duration Measurements of Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Koshut, Thomas M.; Paciesas, William S.; Kouveliotou, Chryssa; vanParadijs, Jan; Pendleton, Geoffrey N.; Fishman, Gerald J.; Meegan, Charles A.

    1996-01-01

    The parameters T(sub 90) and T(sub 50) have recently been introduced as a measurement of the duration of gamma-ray bursts. We present here a description of the method of measuring T(sub 90) and T(sub 50) and its application to gamma-ray bursts observed with the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma-Ray Observatory (CGRO). We use simulated as well as observed time profiles to address some of the possible systematic effects affecting individual T(sub 90) (T(sub 50)) measurements. We show that these systematic effects do not mimic those effects that would result from time dilation if the burst sources are at distances of several Gpc. We discuss the impact of these systematic effects on the T(sub 90) (T(sub 50)) distributions for the gamma-ray bursts observed with BATSE. We distinguish between various types of T(sub 90) (T(sub 50)) distributions, and discuss the ways in which distributions observed with different experiments can vary, even though the measurements for commonly observed bursts may be the same. We then discuss the distributions observed with BATSE and compare them to those observed with other experiments.

  16. Low dose short duration pulsed electromagnetic field effects on cultured human chondrocytes: An experimental study

    PubMed Central

    Anbarasan, Selvam; Baraneedharan, Ulaganathan; Paul, Solomon FD; Kaur, Harpreet; Rangaswami, Subramoniam; Bhaskar, Emmanuel

    2016-01-01

    Background: Pulsed electromagnetic field (PEMF) is used to treat bone and joint disorders for over 30 years. Recent studies demonstrate a significant effect of PEMF on bone and cartilage proliferation, differentiation, synthesis of extracellular matrix (ECM) and production of growth factors. The aim of this study is to assess if PEMF of low frequency, ultralow field strength and short time exposure have beneficial effects on in-vitro cultured human chondrocytes. Materials and Methods: Primary human chondrocytes cultures were established using articular cartilage obtained from knee joint during joint replacement surgery. Post characterization, the cells were exposed to PEMF at frequencies ranging from 0.1 to 10 Hz and field intensities ranging from 0.65 to 1.95 μT for 60 min/day for 3 consecutive days to analyze the viability, ECM component synthesis, proliferation and morphology related changes post exposure. Association between exposure doses and cellular effects were analyzed with paired't’ test. Results: In-vitro PEMF exposure of 0.1 Hz frequency, 1.95 μT and duration of 60 min/day for 3 consecutive days produced the most favorable response on chondrocytes viability (P < 0.001), ECM component production (P < 0.001) and multiplication. Exposure of identical chondrocyte cultures to PEMFs of 0.65 μT field intensity at 1 Hz frequency resulted in less significant response. Exposure to 1.3 μT PEMFs at 10 Hz frequency does not show any significant effects in different analytical parameters. Conclusions: Short duration PEMF exposure may represent a new therapy for patients with Osteoarthritis (OA). PMID:26955182

  17. Simultaneous observation of nascent plasma and bubble induced by laser ablation in water with various pulse durations

    SciTech Connect

    Tamura, Ayaka Matsumoto, Ayumu; Nishi, Naoya; Sakka, Tetsuo; Fukami, Kazuhiro

    2015-05-07

    We investigate the effects of pulse duration on the dynamics of the nascent plasma and bubble induced by laser ablation in water. To examine the relationship between the nascent plasma and the bubble without disturbed by shot-to-shot fluctuation, we observe the images of the plasma and the bubble simultaneously by using two intensified charge coupled device detectors. We successfully observe the images of the plasma and bubble during the pulsed-irradiation, when the bubble size is as small as 20 μm. The light-emitting region of the plasma during the laser irradiation seems to exceed the bubble boundary in the case of the short-pulse (30-ns pulse) irradiation, while the size of the plasma is significantly smaller than that of the bubble in the case of the long-pulse (100-ns pulse) irradiation. The results suggest that the extent of the plasma quenching in the initial stage significantly depends on the pulse duration. Also, we investigate how the plasma-bubble relationship in the very early stage affects the shape of the atomic spectral lines observed at the later delay time of 600 ns. The present work gives important information to obtain high quality spectra in the application of underwater laser-induced breakdown spectroscopy, as well as to clarify the mechanism of liquid-phase laser ablation.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Laser-induced microjet: wavelength and pulse duration effects on bubble and jet generation for drug injection

    NASA Astrophysics Data System (ADS)

    Jang, Hun-jae; Park, Mi-ae; Sirotkin, Fedir V.; Yoh, Jack J.

    2013-12-01

    The expansion of the laser-induced bubble is the main mechanism in the developed microjet injector. In this study, Nd:YAG and Er:YAG lasers are used as triggers of the bubble formation. The impact of the laser parameters on the bubble dynamics is studied and the performance of the injector is evaluated. We found that the main cause of the differences in the bubble behavior comes from the pulse duration and wavelength. For Nd:YAG laser, the pulse duration is very short relative to the bubble lifetime making the behavior of the bubble close to that of the cavitation bubble, while in Er:YAG case, the high absorption in the water and long pulse duration change the initial behavior of the bubble making it close to a vapor bubble. The contraction and subsequent rebound are typical for cavitation bubbles in both cases. The results show that the laser-induced microjet injector generates velocity which is sufficient for the drug delivery for both laser beams of different pulse duration. We estimate the typical velocity within 30-80 m/s range and the breakup length to be larger than 1 mm suitable for trans-dermal drug injection.

  20. Short Shock Pulse Duration Experiments Plus Ignition and Growth Modeling on Composition B

    NASA Astrophysics Data System (ADS)

    May, Chadd; Tarver, Craig

    2013-06-01

    Short pulse duration shock initiation experiments were performed on 1.71 g/cm3 Composition B using electrically driven kapton flyer plates. Critical impact velocities for initiation at several flyer plate thicknesses and diameters were determined. For 2 mm diameter flyers, the critical velocities for shock initiation ranged from 4.06 to 4.72 km/s for flyer thicknesses ranging from 127 to 50.8 microns. Since the failure diameter of Composition B is approximately 4 mm, the kapton flyers imparted sufficient energy to overcome the effects of both rear and size rarefaction wave energy loses and cause detonation. The Ignition and Growth reactive flow model parameters for Composition B were modified to include unreacted Hugoniot, detonation reaction zone, and overdriven detonation experimental data and then applied to the kapton flyer data with good results. This work was performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.: Explosive, Composition B, shock to detonation transition, Ignition and Growth: 82.33.Vx, 82.40.Fp.

  1. A waveguide high-pass filter system for measuring the spectrum of pulsed terahertz sources

    NASA Astrophysics Data System (ADS)

    Glyavin, M. Yu.; Goykhman, M. B.; Gromov, A. V.; Palitsin, A. V.; Panin, A. N.; Rodin, Yu. V.; Fil'chenkov, S. E.

    2016-05-01

    We propose a system for measuring spectra of terahertz (THz) pulses, including single pulses, which is based on high-pass filters (HPFs). The system consists of channels for measuring amplitudes of pulses (initial pulses and those transmitted via HPFs with different cutoff frequencies) and an algorithm for processing of the obtained data. The pulse spectrum is restored by using the iteration method or the amplitude-frequency method. The iteration method of spectrum restoration is applicable in the range of THz pulse durations from 10-9 s to 10-7 s. The amplitude-frequency method is applicable to THz pulses with durations exceeding 10-8 s. The system for measuring of THz pulse spectra was simulated by using the characteristics of specially developed waveguide HPFs. The relative simulation error of determining the central frequency by the amplitude-frequency method is equal to 2 · 10-6 for THz pulse durations of 10-5 s and longer.

  2. Pulse energy measurement at the SXR instrument

    DOE PAGESBeta

    Moeller, Stefan; Brown, Garth; Dakovski, Georgi; Hill, Bruce; Holmes, Michael; Loos, Jennifer; Maida, Ricardo; Paiser, Ernesto; Schlotter, William; Turner, Joshua J.; et al

    2015-04-14

    A gas monitor detector was implemented and characterized at the Soft X-ray Research (SXR) instrument to measure the average, absolute and pulse-resolved photon flux of the LCLS beam in the energy range between 280 and 2000 eV. The detector is placed after the monochromator and addresses the need to provide reliable absolute pulse energy as well as pulse-resolved measurements for the various experiments at this instrument. This detector provides a reliable non-invasive measurement for determining flux levels on the samples in the downstream experimental chamber and for optimizing signal levels of secondary detectors and for the essential need of datamore » normalization. The design, integration into the instrument and operation are described, and examples of its performance are given.« less

  3. Pulse energy measurement at the SXR instrument

    SciTech Connect

    Moeller, Stefan; Brown, Garth; Dakovski, Georgi; Hill, Bruce; Holmes, Michael; Loos, Jennifer; Maida, Ricardo; Paiser, Ernesto; Schlotter, William; Turner, Joshua J.; Wallace, Alex; Jastrow, Ulf; Kreis, Svea; Sorokin, Andrey A.; Tiedtke, Kai

    2015-04-14

    A gas monitor detector was implemented and characterized at the Soft X-ray Research (SXR) instrument to measure the average, absolute and pulse-resolved photon flux of the LCLS beam in the energy range between 280 and 2000 eV. The detector is placed after the monochromator and addresses the need to provide reliable absolute pulse energy as well as pulse-resolved measurements for the various experiments at this instrument. This detector provides a reliable non-invasive measurement for determining flux levels on the samples in the downstream experimental chamber and for optimizing signal levels of secondary detectors and for the essential need of data normalization. The design, integration into the instrument and operation are described, and examples of its performance are given.

  4. Pulse energy measurement at the SXR instrument

    PubMed Central

    Moeller, Stefan; Brown, Garth; Dakovski, Georgi; Hill, Bruce; Holmes, Michael; Loos, Jennifer; Maida, Ricardo; Paiser, Ernesto; Schlotter, William; Turner, Joshua J.; Wallace, Alex; Jastrow, Ulf; Kreis, Svea; Sorokin, Andrey A.; Tiedtke, Kai

    2015-01-01

    A gas monitor detector was implemented and characterized at the Soft X-ray Research (SXR) instrument to measure the average, absolute and pulse-resolved photon flux of the LCLS beam in the energy range between 280 and 2000 eV. The detector is placed after the monochromator and addresses the need to provide reliable absolute pulse energy as well as pulse-resolved measurements for the various experiments at this instrument. This detector provides a reliable non-invasive measurement for determining flux levels on the samples in the downstream experimental chamber and for optimizing signal levels of secondary detectors and for the essential need of data normalization. The design, integration into the instrument and operation are described, and examples of its performance are given. PMID:25931075

  5. Nitriding molybdenum: Effects of duration and fill gas pressure when using 100-Hz pulse DC discharge technique

    NASA Astrophysics Data System (ADS)

    Ikhlaq, U.; R., Ahmad; Shafiq, M.; Saleem, S.; S. Shah, M.; Hussain, T.; A. Khan, I.; K., Abbas; S. Abbas, M.

    2014-10-01

    Molybdenum is nitrided by a 100-Hz pulsed DC glow discharge technique for various time durations and fill gas pressures to study the effects on the surface properties of molybdenum. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) are used for the structural and morphological analysis of the nitrided layers. Vickers' microhardness tester is utilized to investigate surface microhardness. Phase analysis shows the formation of more molybdenum nitride molecules for longer nitriding durations at fill gas pressures of 2 mbar and 3 mbar (1 bar = 105 Pa). A considerable increase in surface microhardness (approximately by a factor of 2) is observed for longer duration (10 h) and 2-mbar pressure. Longer duration (10 h) and 2-mbar fill gas pressure favors the formation of homogeneous, smooth, hard layers by the incorporation of more nitrogen.

  6. Pulsed thrust measurements using laser interferometry

    NASA Astrophysics Data System (ADS)

    Cubbin, E. A.; Ziemer, J. K.; Choueiri, E. Y.; Jahn, R. G.

    1997-06-01

    An optical interferometric proximeter system (IPS) for measuring thrust and impulse bit of pulsed electric thrusters was developed. Unlike existing thrust stands, the IPS-based thrust stand offers the advantage of a single system that can yield electromagnetic interference-free, high accuracy (<2% error) thrust measurements within a very wide range of impulses (100 μN s to above 10 N s) covering the impulse range of all known pulsed plasma thrusters. In addition to pulsed thrusters, the IPS is theoretically shown to be capable of measuring steady-state thrust values as low as 20 μN for microthrusters such as the field emission electric propulsion thruster. The IPS-based thrust stand relies on measuring the dynamic response of a swinging arm using a two-sensor laser interferometer with 10 nm position accuracy. The wide application of the thrust stand is demonstrated with thrust measurements of an ablative pulsed plasma thruster and a quasi-steady magnetoplasmadynamic thruster.

  7. 948 kHz repetition rate, picosecond pulse duration, all-PM 1.03 μm mode-locked fiber laser based on nonlinear polarization evolution

    NASA Astrophysics Data System (ADS)

    Boivinet, S.; Lecourt, J.-B.; Hernandez, Y.; Fotiadi, A.; Mégret, P.

    2014-05-01

    We present in this study a PM all-fiber laser oscillator passively mode-locked (ML) at 1.03 μm. The laser is based on Nonlinear Polarization Evolution (NPE) in polarization maintaining (PM) fibers. In order to obtain the mode-locking regime, a nonlinear reflective mirror including a fibered polarizer, a long fiber span and a fibered Faraday mirror (FM) is inserted in a Fabry-Perot laser cavity. In this work we explain the principles of operation of this original laser design that permits to generate ultrashort pulses at low repetition (lower that 1MHz) rate with a cavity length of 100 m of fiber. In this experiment, the measured pulse duration is about 6 ps. To our knowledge this is the first all-PM mode-locked laser based on the NPE with a cavity of 100m length fiber and a delivered pulse duration of few picosecondes. Furthermore, the different mode-locked regimes of the laser, i.e. multi-pulse, noise-like mode-locked and single pulse, are presented together with the ways of controlling the apparition of these regimes. When the single pulse mode-locking regime is achieved, the laser delivers linearly polarized pulses in a very stable way. Finally, this study includes numerical results which are obtained with the resolution of the NonLinear Schrodinger Equations (NLSE) with the Split-Step Fourier (SSF) algorithm. This modeling has led to the understanding of the different modes of operation of the laser. In particular, the influence of the peak power on the reflection of the nonlinear mirror and its operation are studied.

  8. Laser pulse duration dependence of blister formation on back-radiated Ti thin films for BB-LIFT

    NASA Astrophysics Data System (ADS)

    Goodfriend, N. T.; Starinskiy, S. V.; Nerushev, O. A.; Bulgakova, N. M.; Bulgakov, A. V.; Campbell, E. E. B.

    2016-03-01

    The influence of the laser pulse duration on the mechanism of blister formation in the particle transfer technique, blister-based laser-induced forward transfer, was investigated. Pulses from a fs Ti:Sapphire laser (120 fs, 800 nm) and from a ns Nd:YAG laser (7 ns, 532 nm) were used to directly compare blister formation on thin titanium films of ca. 300 nm thickness, deposited on glass. The different blister morphologies were compared and contrasted by using optical microscopy and atomic force microscopy. The results provide evidence for different blister formation mechanisms: for fs pulses the mechanism is predominantly ablation at the metal-glass interface accompanied by confined plasma expansion and deformation of the remaining metal film; for ns pulses it is heating accompanied by thermal expansion of the metal film.

  9. Millisecond duration pulses for flow-through electro-induced protein extraction from E. coli and associated eradication.

    PubMed

    Coustets, M; Ganeva, V; Galutzov, B; Teissie, J

    2015-06-01

    Pulsed electric fields are used to induce membrane permeabilization on cells. In the case of species with cell wall (yeasts, microalgae), it was previously shown that when the pulse duration was several ms long, this resulted in a cytoplasmic soluble protein slow leakage. In this work, we show that a similar consequence can be obtained with different strains of E. coli. Experimental evidences of a resulting wall alteration are described. Pre-industrial flow process pilots are used. As the membrane electropermeabilization can be irreversible by applying a proper choice of the pulse parameters, this approach is used for bacterial inactivation in flow process. It is observed that sub-millisecond pulse trains are more cost effective than longer ones. PMID:25183448

  10. Influence of laser pulse duration on the electrochemical performance of laser structured LiFePO4 composite electrodes

    NASA Astrophysics Data System (ADS)

    Mangang, M.; Seifert, H. J.; Pfleging, W.

    2016-02-01

    Lithium iron phosphate is a promising cathode material for lithium-ion batteries, despite its low electrical conductivity and lithium-ion diffusion kinetic. To overcome the reduced rate performance, three dimensional (3D) architectures were generated in composite cathode layers. By using ultrashort laser radiation with pulse durations in the femtosecond regime the ablation depth per pulse is three times higher compared to nanosecond laser pulses. Due to the 3D structuring, the surface area of the active material which is in direct contact with liquid electrolyte, i.e. the active surface, is increased. As a result the capacity retention and the cycle stability were significantly improved, especially for high charging/discharging currents. Furthermore, a 3D structure leads to higher currents during cyclic voltammetry. Thus, the lithium-ion diffusion kinetic in the cell was improved. In addition, using ultrashort laser pulses results in a high aspect ratio and further improvement of the cell kinetic was achieved.

  11. Pulsed thrust measurements using electromagnetic calibration techniques.

    PubMed

    Tang, Haibin; Shi, Chenbo; Zhang, Xin'ai; Zhang, Zun; Cheng, Jiao

    2011-03-01

    A thrust stand for accurately measuring impulse bits, which ranged from 10-1000 μN s using a noncontact electromagnetic calibration technique is described. In particular, a permanent magnet structure was designed to produce a uniform magnetic field, and a multiturn coil was made to produce a calibration force less than 10 mN. The electromagnetic calibration force for pulsed thrust measurements was linear to the coil current and changed less than 2.5% when the distance between the coil and magnet changed 6 mm. A pulsed plasma thruster was first tested on the thrust stand, and afterward five single impulse bits were measured to give a 310 μN s average impulse bit. Uncertainty of the measured impulse bit was analyzed to evaluate the quality of the measurement and was found to be 10 μN s with 95% credibility. PMID:21456799

  12. High power laser pulses with voltage controlled durations of 400 - 1000 ps.

    PubMed

    Harth, F; Ulm, T; Lührmann, M; Knappe, R; Klehr, A; Hoffmann, Th; Erbert, G; L'huillier, J A

    2012-03-26

    We report on the generation and amplification of pulses with pulse widths of 400 - 1000 ps at 1064 nm. For pulse generation an ultra-fast semiconductor modulator is used that modulates a cw-beam of a DFB diode laser. The pulse lengths could be adjusted by the use of a voltage control. The pulses were amplified in a solid state Nd:YVO₄ regenerative amplifier to an average power of up to 47.7 W at 100 - 816 kHz. PMID:22453379

  13. Progress toward a microsecond duration, repetitive, intense-ion beam for active spectroscopic measurements on ITER

    SciTech Connect

    Davis, H.A.; Bartsch, R.R.; Barnes, C.W.

    1996-06-01

    The authors describe the design of an intense, pulsed, repetitive, neutral beam based on magnetically insulated diode technology for injection into ITER for spectroscopic measurements of thermalizing alpha particle and thermal helium density profiles, ion temperature, plasma rotation, and low Z impurity concentrations in the confinement region. The beam is being developed to enhance low signal-to-noise ratios expected with conventional steady-state ion beams because of severe beam attenuation and intense bremstrahlung emission. A 5 GW (e.g., 100 keV, 50 kA) one-microsecond-duration beam would increase the signal by 10{sup 3} compared to a conventional 5 MW beam with signal-to-noise ratios comparable to those from a chopped conventional beam in one second.

  14. Source duration of stress and water-pressure induced seismicity derived from experimental analysis of P wave pulse width in granite

    NASA Astrophysics Data System (ADS)

    Masuda, K.

    2013-12-01

    Pulse widths of P waves in granite, measured in the laboratory, were analyzed to investigate source durations of rupture processes for water-pressure induced and stress-induced microseismicity. Much evidence suggests that fluids in the subsurface are intimately linked to faulting processes. Studies of seismicity induced by water injection are thus important for understanding the trigger mechanisms of earthquakes as well as for engineering applications such as hydraulic fracturing of rocks at depth for petroleum extraction. Determining the cause of seismic events is very important in seismology and engineering; however, water-pressure induced seismic events are difficult to distinguish from those induced by purely tectonic stress. To investigate this problem, we analyzed the waveforms of acoustic emissions (AEs) produced in the laboratory by both water-pressure induced and stress-induced microseismicity. We used a cylinder (50 mm in diameter and 100 mm in length) of medium-grained granite. We applied a differential stress of about 70% of fracture strength, to the rock sample under 40 MPa confining pressure and held it constant throughout the experiment. When the primary creep stage and acoustic emissions (AEs) caused by the initial loading had ceased, we injected distilled water into the bottom end of the sample at a constant pressure of 17 MPa until macroscopic fracture occurred. We analysed AE waveforms produced by stress-induced AEs which occurred before the water-injection and by water-pressure induced AEs which occurred after the water-injection. Pulse widths were measured from the waveform traces plotted from the digital data. To investigate the source duration of the rupture process, we estimated the pulse width at the source and normalized by event magnitude to obtain a scaled pulse width at the source. After the effects of event size and hypocentral distance were removed from observed pulse widths, the ratio of the scaled source durations of water

  15. Pulse

    MedlinePlus

    Heart rate; Heart beat ... The pulse can be measured at areas where an artery passes close to the skin. These areas include the: ... side of the foot Wrist To measure the pulse at the wrist, place the index and middle ...

  16. Spectral, kinetic and polarization characteristics of luminescence of acriflavine in polymeric matrix under pulsed excitation with different durations and intensities

    NASA Astrophysics Data System (ADS)

    Kaputskaya, I. A.; Ermilov, E. A.; Tannert, S.; Röder, B.; Gorbatsevich, S. K.

    2006-08-01

    Spectral, kinetic and polarization characteristics of fluorescence and thermally activated delayed fluorescence (TADF) of dye solid solutions have been investigated. It was shown that the increasing of the excitation pulse duration results in rise of TADF decay time, but an increasing of the long pulse excitation intensity results in a faster TADF decay. In the presence of Förster resonance energy transfer (FRET) the fluorescence spectrum is shifting non-monotonically with time when the intensity of the excitation pulse is high. At the time moment when the excitation is switched off the polarization degree of luminescence of the concentrated dye solutions strongly reduces. The energy transfer from the molecules in the S 1 state to the molecules in the T 1 state reduces the depolarization of luminescence caused by FRET. Numerical simulations were made by means of Monte-Carlo integrations and results were compared with experimental data obtained for acriflavine in polyvinyl alcohol films.

  17. III Lead ECG Pulse Measurement Sensor

    NASA Astrophysics Data System (ADS)

    Thangaraju, S. K.; Munisamy, K.

    2015-09-01

    Heart rate sensing is very important. Method of measuring heart pulse by using an electrocardiogram (ECG) technique is described. Electrocardiogram is a measurement of the potential difference (the electrical pulse) generated by a cardiac tissue, mainly the heart. This paper also reports the development of a three lead ECG hardware system that would be the basis of developing a more cost efficient, portable and easy to use ECG machine. Einthoven's Three Lead method [1] is used for ECG signal extraction. Using amplifiers such as the instrumentation amplifier AD620BN and the conventional operational amplifier Ua741 that would be used to amplify the ECG signal extracted develop this system. The signal would then be filtered from noise using Butterworth filter techniques to obtain optimum output. Also a right leg guard was implemented as a safety feature to this system. Simulation was carried out for development of the system using P-spice Program.

  18. Force measurement using strain-gauge balance in a shock tunnel with long test duration.

    PubMed

    Wang, Yunpeng; Liu, Yunfeng; Luo, Changtong; Jiang, Zonglin

    2016-05-01

    Force tests were conducted at the long-duration-test shock tunnel JF12, which has been designed and built in the Institute of Mechanics, Chinese Academy of Sciences. The performance tests demonstrated that this facility is capable of reproducing a flow of dry air at Mach numbers from 5 to 9 at more than 100 ms test duration. Therefore, the traditional internal strain-gauge balance was considered for the force tests use in this large impulse facility. However, when the force tests are conducted in a shock tunnel, the inertial forces lead to low-frequency vibrations of the test model and its motion cannot be addressed through digital filtering because a sufficient number of cycles cannot be found during a shock tunnel run. The post-processing of the balance signal thus becomes extremely difficult when an averaging method is employed. Therefore, the force measurement encounters many problems in an impulse facility, particularly for large and heavy models. The objective of the present study is to develop pulse-type sting balance by using a strain-gauge sensor that can be applied in the force measurement of 100 ms test time, especially for the force test of the large-scale model. Different structures of the S-series (i.e., sting shaped balances) strain-gauge balance are proposed and designed, and the measuring elements are further optimized to overcome the difficulties encountered during the measurement of aerodynamic force in a shock tunnel. In addition, the force tests were conducted using two large-scale test models in JF12 and the S-series strain-gauge balances show good performance in the force measurements during the 100 ms test time. PMID:27250471

  19. Quantum nondemolition measurement by pulsed oscillation

    NASA Astrophysics Data System (ADS)

    Zhang, Gui-Ying; Zhao, Kai-Feng

    2016-03-01

    Paramagnetic Faraday rotation is a quantum nondemolition measurement method that can generate spin squeezing and improve the measurement precision of a collective spin component beyond the standard quantum limit. In practice, a constant bias magnetic field is used to drive the spin precessing at sufficiently high frequency in order to lift the signal out of low-frequency technical noises. However, continuous measurement of precessing spins introduces back-action noise (BAN) due to the light-shift effect. Two types of back-action-evading (BAE) measurement of collective spin components have been demonstrated recently: continuous measurement of a two-ensemble system and stroboscopic measurement of a single ensemble. Here we propose another single ensemble BAE measurement by periodically modulating the bias field with π pulses. Our theoretical calculation shows that under experimental settings where pulse-field modulation does not introduce significant decoherences, the proposed method can suppress the BAN and generate spin squeezing faster than the stroboscopic one at the same probe light power. Moreover, if it is combined with synchronous stroboscopic probing, light-shift BAN can be completely eliminated.

  20. FEM modeling and histological analyses on thermal damage induced in facial skin resurfacing procedure with different CO2 laser pulse duration

    NASA Astrophysics Data System (ADS)

    Rossi, Francesca; Zingoni, Tiziano; Di Cicco, Emiliano; Manetti, Leonardo; Pini, Roberto; Fortuna, Damiano

    2011-07-01

    Laser light is nowadays routinely used in the aesthetic treatments of facial skin, such as in laser rejuvenation, scar removal etc. The induced thermal damage may be varied by setting different laser parameters, in order to obtain a particular aesthetic result. In this work, it is proposed a theoretical study on the induced thermal damage in the deep tissue, by considering different laser pulse duration. The study is based on the Finite Element Method (FEM): a bidimensional model of the facial skin is depicted in axial symmetry, considering the different skin structures and their different optical and thermal parameters; the conversion of laser light into thermal energy is modeled by the bio-heat equation. The light source is a CO2 laser, with different pulse durations. The model enabled to study the thermal damage induced into the skin, by calculating the Arrhenius integral. The post-processing results enabled to study in space and time the temperature dynamics induced in the facial skin, to study the eventual cumulative effects of subsequent laser pulses and to optimize the procedure for applications in dermatological surgery. The calculated data where then validated in an experimental measurement session, performed in a sheep animal model. Histological analyses were performed on the treated tissues, evidencing the spatial distribution and the entity of the thermal damage in the collageneous tissue. Modeling and experimental results were in good agreement, and they were used to design a new optimized laser based skin resurfacing procedure.

  1. Single-shot measurement of the spectral envelope of broad-bandwidth terahertz pulses from femtosecond electron bunches

    SciTech Connect

    van Tilborg, Jeroen; Toth, Csaba; Matlis, Nicholas; Plateau, Guillaume; Leemans, Wim

    2011-06-17

    We present a new approach (demonstrated experimentally and through modeling) to characterize the spectral envelope of a terahertz (THz) pulse in a single shot. The coherent THz pulse is produced by a femtosecond electron bunch and contains information on the bunch duration. The technique, involving a single low-power laser probe pulse, is an extension of the conventional spectral encoding method (limited in time resolution to hundreds of femtoseconds) into a regime only limited in resolution by the laser pulse length (tens of femtoseconds). While only the bunch duration is retrieved (and not the exact charge profile), such a measurement provides a useful and critical parameter for optimization of the electron accelerator.

  2. Ultrashort Pulse Reflectometry (USPR) Density Profile Measurements on GAMMA-10

    NASA Astrophysics Data System (ADS)

    Domier, C. W.; Roh Luhmann, Y., Jr.; Mase, A.; Kubota, S.

    1999-11-01

    Ultrashort pulse reflectometry (USPR) involves time-of-flight measurements of extremely broadband, high speed chirped signals ( ns sweep times). A multichannel USPR system has been installed on the central cell of the GAMMA-10 mirror machine located at the University of Tsukuba, Japan. Here, the output from a 65 ps FWHM impulse generator is stretched and amplified to form a 10 ns duration, 11-18 GHz chirp signal. A five channel X-mode USPR receiver, with frequency channels at 12, 13, 15, 16 and 17 GHz, measures the double-pass time delay of each reflected subpacket simultaneously with 25 ps time resolution. Density profile and fluctuation data collected on GAMMA-10 will be presented.

  3. An investigation of fatigue phenomenon in the upper limb muscle due to short duration pulses in an FES system

    NASA Astrophysics Data System (ADS)

    Naeem, Jannatul; Wong Azman, Amelia; Khan, Sheroz; Mohd Mustafah, Yasir

    2013-12-01

    Functional Electrical Stimulation (FES) is a method of artificially stimulating muscles or nerves in order to result in contraction or relaxation of muscles. Many studies have shown that FES system has helped patients to live a better lives especially those who are suffering from physical mobility. Unfortunately, one of the main limitations of an FES system besides of its high cost is largely due to muscle fatigue. Muscle fatigue will affect the training duration which could delay patients' recovery rate. In this paper, we analyzed the occurrence of this fatigue phenomenon in terms of stimulator parameters such as amplitude, frequency, pulse width and pulse shape. The objective of this investigation is to identify other key features of the FES system parameters in order to prolong the training duration among patients. The experiment has been done on a healthy person for the duration of one minute and later the muscles response will be observed. Resultant muscle response is recorded as force using force resistive sensor. The experimental results show muscles will get fatigue at a different rate as the frequency increases. The experiment also shows that the duty cycle is reciprocal to the resultant force.

  4. Laser-induced damage of hafnia coatings as a function of pulse duration in the femtosecond to nanosecond range

    SciTech Connect

    Gallais, Laurent; Mangote, Benoit; Zerrad, Myriam; Commandre, Mireille; Melninkaitis, Andrius; Mirauskas, Julius; Jeskevic, Maksim; Sirutkaitis, Valdas

    2011-03-20

    Laser-damage thresholds and morphologies of hafnia single layers exposed under femtosecond, picosecond, and nanosecond single pulses (1030/1064nm) are reported. The samples were made with different deposition parameters in order to study how the damage behavior of the samples evolves with the pulse duration and how it is linked to the deposition process. In the femtosecond to picosecond regime, the scaling law of the laser-induced damage threshold as a function of pulse duration is in good agreement with the models of photo and avalanche ionization based on the rate equation for free electron generation. However, differences in the damage morphologies between samples are shown. No correlation between the nanosecond and femtosecond/picosecond laser-damage resistance of hafnia coatings could be established. We also report evidence of the transition in damage mechanisms for hafnia, from an ablation process linked to intrinsic properties of the material to a defect-induced process, that exists between a few picoseconds and a few tens of picoseconds.

  5. 140-fs duration and 60-W peak power blue-violet optical pulses generated by a dispersion-compensated GaInN mode-locked semiconductor laser diode using a nonlinear pulse compressor.

    PubMed

    Kono, Shunsuke; Watanabe, Hideki; Koda, Rintaro; Fuutagawa, Noriyuki; Narui, Hironobu

    2015-12-14

    Blue-violet optical pulses of 140-fs duration and 60-W peak power were obtained from a dispersion-compensated GaInN mode-locked semiconductor laser diode using a nonlinear pulse compression technique. Wavelength-dependent group velocity dispersion expressed by third-order phase dispersion was applied to the optical pulses using a pulse compressor with a spatial light modulator. The obtained optical pulses had the shortest duration ever obtained for a mode-locked semiconductor laser diode using edge-emitting type devices. PMID:26698968

  6. Electromagnetic pulse-induced current measurement device

    NASA Astrophysics Data System (ADS)

    Gandhi, Om P.; Chen, Jin Y.

    1991-08-01

    To develop safety guidelines for exposure to high fields associated with an electromagnetic pulse (EMP), it is necessary to devise techniques that would measure the peak current induced in the human body. The main focus of this project was to design, fabricate, and test a portable, self-contained stand-on device that would measure and hold the peak current and the integrated change Q. The design specifications of the EMP-Induced Current Measurement Device are as follows: rise time of the current pulse, 5 ns; peak current, 20-600 A; charge Q, 0-20 microcoulombs. The device uses a stand-on parallel-plate bilayer sensor and fast high-frequency circuit that are well-shielded against spurious responses to high incident fields. Since the polarity of the incident peak electric field of the EMP may be either positive or negative, the induced peak current can also be positive or negative. Therefore, the device is designed to respond to either of these polarities and measure and hold both the peak current and the integrated charge which are simultaneously displayed on two separate 3-1/2 digit displays. The prototype device has been preliminarily tested with the EMP's generated at the Air Force Weapons Laboratory (ALECS facility) at Kirtland AFB, New Mexico.

  7. Performance of Variable Duration STUD Pulses with Fixed Peal Intensity and their Compliments

    NASA Astrophysics Data System (ADS)

    Hüller, Stefan; Afeyan, Bedros

    2015-11-01

    The simplest approach to STUD pulse implementation, given the requisite bandwidth of the laser is to keep the peak spike intensities fixed while modulating the lasers on and off on a 1-10 ps time scale. To what extent spatial scrambling is required in this case is compared to cases where the peak spike intensity varies with the duty cycle at fixed pulse width, to preserve the energy of the overall laser pulse. We compare RPP/CPP, SSD and STUD pulses at fixed energy with both variable pulse width and fixed peak intensity configurations and vice versa. This allows us to highlight the effects of speckle statistics, memory accumulation and pump depletion in setting gain saturation levels from the ideal democratized, incoherent sums of small growth spurts equally from all regions of the plasma, vs localized and highly nonlinear growth and re-amplification due to the unchanging or much too slowly changing nature of the illumination strategy, such as RPP/CPP or SSD. Work supported by the DOE NNSA-OFES Joint Program on HEDLP.

  8. Propagation of the pulsed electron beam of nanosecond duration in gas composition of high pressure

    NASA Astrophysics Data System (ADS)

    Kholodnaya, G.; Sazonov, R.; Ponomarev, D.; Remnev, G.

    2015-11-01

    This paper presents the results of the investigation of the propagation of an electron beam in the high-pressure gas compositions (50, 300, and 760 Torr): sulfur hexafluoride and hydrogen, sulfur hexafluoride and nitrogen, sulfur hexafluoride and argon. The experiments have been performed using the TEA-500 laboratory accelerator. The main parameters of the accelerator are as follows: an accelerating voltage of 500 kV; an electron beam current of 10 kA; a pulse width at half maximum of 60 ns; a pulse energy of 200 J; a pulse repetition rate of up to 5 pulses per second, a beam diameter of 5 cm. The pulsed electron beam was injected into a 55 cm metal drift tube. The drift tube is equipped with three reverse-current shunts with simultaneous detecting of signals. The obtained results of the investigation make it possible to conclude that the picture of the processes occurring in the interaction of an electron beam in the high-pressure gas compositions is different from that observed in the propagation of the electron beam in the low-pressure gas compositions (1 Torr).

  9. Preliminary total dose measurements on LDEF. [long duration exposure facility

    NASA Technical Reports Server (NTRS)

    Reitz, G.

    1992-01-01

    After spending nearly six years in Earth's orbit twenty stacks consisting of radiation detectors and biological objects are now back on Earth. These Free Flyer Biostack experiments are part of the Long Duration Exposure Facility (LDEF). The major objective of the experiments are to investigate the biological effectiveness of single heavy ions of the cosmic radiation in various biological systems and to provide information about the spectral composition of the radiation field and the total dose received in the LDEF orbit. The preliminary analysis of the thermoluminescence dosimeters (TLD) yields maximum absorbed dose rates of 2.24 mGy day(exp -1) behind 0.7 g cm(exp -2) shielding and 1.17 mGy day(exp -1) behind 12 g cm(exp -2) shielding. A thermal neutron fluence of 1.7 n cm(exp -2)s(exp -1) is determined from the differences in absorbed dose for different isotopic mixtures of lithium. The results of this experiment on LDEF are especially valuable since LDEF stayed for almost six years in the prospected orbit of the Space Station Freedom.

  10. Precision control of lesions by high-intensity focused ultrasound cavitation-based histotripsy through varying pulse duration.

    PubMed

    Xu, Jin; Bigelow, Timothy A; Nagaraju, Ravindra

    2013-07-01

    The goal of this experimental study was to explore the feasibility of acquiring controllable precision through varying pulse duration for lesions generated by cavitation-based histotripsy. Histotripsy uses high-intensity focused ultrasound (HIFU) at low duty factor to create energetic bubble clouds inside tissue to liquefy a region. It uses cavitation-mediated mechanical effects while minimizing heating, and has the advantages of real-time monitoring and lesion fidelity to treatment planning. In our study, histotripsy was applied to three groups of tissue-mimicking agar samples of different stiffnesses (29.4 ± 5.3, 44.8 ± 5.9, and 66.4 ± 7.1 kPa). B-mode imaging was used first to quantify bubble cluster dimensions in both water and agar. Then, a 4.5-mm-wide square (lateral to the focal plane) was scanned in a raster pattern with a step size of 0.75 mm in agar histotripsy experiments to estimate equivalent bubble cluster dimensions based on the histotripsyinduced damage. The 15-s exposure at each treatment location comprised 5000 sine-wave tone bursts at a spatial-peak pulseaverage intensity of 41.1 kW/cm2, with peak compressional and rarefactional pressures of 102 and 17 MPa, respectively. The results showed that bubble cluster width and length increased with pulse duration and decreased with agar stiffness. Therefore, a significant improvement in histotripsy precision could be achieved by reducing the pulse duration. PMID:25004507

  11. Living human face measurements using pulsed holography

    NASA Astrophysics Data System (ADS)

    Bongartz, Jens; Giel, Dominik M.; Hering, Peter

    2000-10-01

    A method to measure precisely the 2D portrait of patients undergoing maxillofacial surgery based on holography is presented. We record holograms of patients with a pulsed Nd:YLF laser system on high resolution photographic glass plates. These images contain the 3D spatial information which, due to the extremely short recording time, is not affected at all by involuntary movements. The reconstructed real image of the hologram is sliced into a series of 2D projections by means of a screen. A first approach to reconstruct the patient's 3D surface information from the captured data set is presented.

  12. Influence of pulse duration, energy, and focusing on laser-assisted water condensation

    SciTech Connect

    Petit, Y.; Henin, S.; Kasparian, J.; Wolf, J. P.; Rohwetter, P.; Stelmaszczyk, K.; Hao, Z. Q.; Nakaema, W. M.; Woeste, L.; Vogel, A.; Pohl, T.; Weber, K.

    2011-01-24

    We investigate the influence of laser parameters on laser-assisted water condensation in the atmosphere. Pulse energy is the most critical parameter. Nanoparticle generation depends linearly on energy beyond the filamentation threshold. Shorter pulses are more efficient than longer ones with saturation at {approx}1.5 ps. Multifilamenting beams appear more efficient than strongly focused ones in triggering the condensation and growth of submicronic particles, while polarization has a negligible influence on the process. The data suggest that the initiation of laser-assisted condensation relies on the photodissociation of the air molecules rather than on their photoionization.

  13. High power fiber MOPA based QCW laser delivering pulses with arbitrary duration on demand at high modulation bandwidth.

    PubMed

    Petkovšek, Rok; Novak, Vid; Agrež, Vid

    2015-12-28

    We report on a concept of a fiber MOPA based quasi-CW laser working at high modulation bandwidths up to 40 MHz capable of producing arbitrary pulse durations at arbitrary repetition rates. An output power of over 100 W was achieved and an on-off contrast of 25 dB. The laser features a dual-channel (dual-wavelength) seed source, a double stage YDF amplifier and a volume-Bragg-grating-based signal de-multiplexer. Minimization of transients was conducted through experiment and model analysis. PMID:26831982

  14. Pulse shape measurements using single shot-frequency resolved optical gating for high energy (80 J) short pulse (600 fs) laser

    SciTech Connect

    Palaniyappan, S.; Johnson, R.; Shimada, T.; Gautier, D. C.; Letzring, S.; Offermann, D. T.; Fernandez, J. C.; Shah, R. C.; Jung, D.; Hegelich, B. M.; Hoerlein, R.

    2010-10-15

    Relevant to laser based electron/ion accelerations, a single shot second harmonic generation frequency resolved optical gating (FROG) system has been developed to characterize laser pulses (80 J, {approx}600 fs) incident on and transmitted through nanofoil targets, employing relay imaging, spatial filter, and partially coated glass substrates to reduce spatial nonuniformity and B-integral. The device can be completely aligned without using a pulsed laser source. Variations of incident pulse shape were measured from durations of 613 fs (nearly symmetric shape) to 571 fs (asymmetric shape with pre- or postpulse). The FROG measurements are consistent with independent spectral and autocorrelation measurements.

  15. Measurement Capabilities of Single-Pulse Planar Doppler Velocimetry

    NASA Technical Reports Server (NTRS)

    McKenzie, Robert L.; Kutler, Paul F. (Technical Monitor)

    1994-01-01

    Preliminary investigations are described of a method that is capable of measuring instantaneous, 3-D, velocity vectors everywhere in a light sheet generated by a pulsed laser. The technique, here called Planar Doppler Velocimetry (PDV), is a variation of a new concept for velocity measurements that was called Doppler Global Velocimetry (DGV) in its original disclosure. The concept relies on the use of a narrowband laser and measurements of the Doppler shift of scattered light from particles moving with a flow. The Doppler shift is recorded as a variation in transmission through a sharp-edged spectral filter provided by iodine vapor in a cell. Entire fields of velocity can be determined by using a solid-state camera to record the intensity variations throughout the field of view. However, the implementation of DGV has been centered principally on the use of high power, continuous-wave, ion lasers and measurement times that are determined by the 30-ms framing times of standard video cameras. Hence, they provide velocity fields that are averaged in time at least over that period. On the other hand, the PDV concept described in this presentation incorporates a high energy, repetitively pulsed, Nd-YAG laser that is injection-seeded to make it narrowband and then frequency-doubled to provide light at frequencies absorbed by the iodine vapor. The duration of each pulse is less than 10 nanoseconds. When used in combination with nonstandard, scientific quality, solid state cameras, a sequence of images can be obtained that provides instantaneous velocity vectors everywhere in the field of view. The investigations described in this paper include an accurate characterization of the iodine cell spectral behavior and its influence on the PDV measurements, a derivation of the PDV signal analysis requirements, and the unique aspects of the pulsed laser behavior related to this application. In addition, PDV measurements are to be demonstrated using data from a rotating wheel

  16. Systems approach to measuring short-duration acceleration transients

    NASA Astrophysics Data System (ADS)

    Schelby, F.

    It is common for failures to occur when attempting to acquire acceleration structural response measurements during crash, impact, and pyrotechnic testing. The structural response of a mechanical system to severe transient loading is commonly measured by accelerometers which are less than ideal. In particular, their amplitude-frequency response has one or more resonant peaks so that the output of the accelerometer may not be an exact replica of the input if the transient input stimulus contains frequencies near these resonant peaks, signal distortion, over-ranging of signal conditioning electronics, or even failure of the sensing element may occur. These and other problems have spurred the development of a new acceleration-measuring system which incorporates the following features; Transduction Element; Connectors; Mounting; Electronics; and Transducer Resonance.

  17. Systems approach to measuring short-duration acceleration transients

    NASA Astrophysics Data System (ADS)

    Schelby, F.

    A shock measurement system was developed in which the quartz seismic system, two poole active filter and an FET source follower are incorporated in a transducer housing. It is shown that the system will survive + or 100,000g without damage. The PCB can supply different ranges as required. The PCB Model 305M23, can obtain data comparable to those of standard piezoelectric and piezoresistive accelerometers when high frequencies are absent. In the presence of high frequency stimuli, the accelerometer has obtained data without over ranging its data channel and without introducing error signals from excitation of the resonant frequency of its seismic system. It is useful for impact and pyrotechnic measurements. The development effort and test program have enhanced the probability of acquiring successful structural measurements in harsh mechanical loading environments.

  18. Systems approach to measuring short-duration acceleration transients

    SciTech Connect

    Schelby, F.

    1983-01-01

    A shock measurement system has been developed in which the quartz seismic system, two-poole active filter and an FET source follower are incorporated in a transducer housing measuring 5/16'' hex.x 5/8''. Tests have shown that the system will survive +- 100,000g without damage. Although the results reported here are for accelerometers ranged to +- 20,000g, there is no reason to limit the accelerometers to that range and PCB can supply different ranges as required. The PCB Model 305M23, developed to Sandia's specifications, has proved capable of obtaining data comparable to that of standard piezoelectric and piezoresistive accelerometers when high frequencies are absent. In the presence of high frequency stimuli, the accelerometer has obtained data without over-ranging its data channel and without introducing error signals from excitation of the resonant frequency of its seismic system. It should, therefore, be especially useful for impact and pyrotechnic measurements. These shock accelerometers are in the process of being fielded in earth penetrator vehicles; in shale rubblization experiments will soon be available. It appears this joint development effort and test program has greatly enhanced the probability of acquiring successful structural measurements in harsh mechanical loading environments.

  19. APPROPRIATE DURATIONS AND MEASURES FOR 'CERIODAPHNIA' TOXICITY TESTS

    EPA Science Inventory

    The Mount-Norberg test, which employs a measure of the size of three broods over seven days, has been used extensively in toxicity testing. The authors have applied it to estimating sublethal ecosystem effects of complex effluents in the Raisin River drainage (of Michigan) on the...

  20. Altered gene expression in cultured microglia in response to simulated blast overpressure: possible role of pulse duration.

    PubMed

    Kane, Michael J; Angoa-Pérez, Mariana; Francescutti, Dina M; Sykes, Catherine E; Briggs, Denise I; Leung, Lai Yee; VandeVord, Pamela J; Kuhn, Donald M

    2012-07-26

    Blast overpressure has long been known to cause barotrauma to air-filled organs such as lung and middle ear. However, experience in Iraq and Afghanistan is revealing that individuals exposed to explosive munitions can also suffer traumatic brain injury (TBI) even in the absence of obvious external injury. The interaction of a blast shock wave with the brain in the intact cranial vault is extremely complex making it difficult to conclude that a blast wave interacts in a direct manner with the brain to cause injury. In an attempt to "isolate" the shock wave and test its primary effects on cells, we exposed cultured microglia to simulated blast overpressure in a barochamber. Overpressures ranging from 15 to 45 psi did not change microglial Cox-2 levels or TNF-α secretion nor did they cause cell damage. Microarray analysis revealed increases in expression of a number of microglial genes relating to immune function and inflammatory responses to include Saa3, Irg1, Fas and CxCl10. All changes in gene expression were dependent on pulse duration and were independent of pressure. These results indicate that microglia are mildly activated by blast overpressure and uncover a heretofore undocumented role for pulse duration in this process. PMID:22698585

  1. Altered Gene Expression in Cultured Microglia in Response to Simulated Blast Overpressure: Possible Role of Pulse Duration

    PubMed Central

    Kane, Michael J.; Angoa-Pérez, Mariana; Francescutti, Dina M.; Sykes, Catherine E.; Briggs, Denise I.; Leung, Lai Yee; VandeVord, Pamela J.; Kuhn, Donald M.

    2012-01-01

    Blast overpressure has long been known to cause barotrauma to air-filled organs such as lung and middle ear. However, experience in Iraq and Afghanistan is revealing that individuals exposed to explosive munitions can also suffer traumatic brain injury (TBI) even in the absence of obvious external injury. The interaction of a blast shock wave with the brain in the intact cranial vault is extremely complex making it difficult to conclude that a blast wave interacts in a direct manner with the brain to cause injury. In an attempt to “isolate” the shock wave and test its primary effects on cells, we exposed cultured microglia to simulated blast overpressure in a barochamber. Overpressures ranging from 15–45 psi did not change microglial Cox-2 levels or TNF-α secretion nor did they cause cell damage. Microarray analysis revealed increases in expression of a number of microglial genes relating to immune function and inflammatory responses to include Saa3, Irg1, Fas and CxCl10. All changes in gene expression were dependent on pulse duration and were independent of pressure. These results indicate that microglia are mildly activated by blast overpressure and uncover a heretofore undocumented role for pulse duration in this process. PMID:22698585

  2. System for generating shaped optical pulses and measuring optical pulses using spectral beam deflection (SBD)

    DOEpatents

    Skupsky, S.; Kessler, T.J.; Letzring, S.A.

    1993-11-16

    A temporally shaped or modified optical output pulse is generated from a bandwidth-encoded optical input pulse in a system in which the input pulse is in the form of a beam which is spectrally spread into components contained within the bandwidth, followed by deflection of the spectrally spread beam (SBD) thereby spatially mapping the components in correspondence with the temporal input pulse profile in the focal plane of a lens, and by spatially selective attenuation of selected components in that focal plane. The shaped or modified optical output pulse is then reconstructed from the attenuated spectral components. The pulse-shaping system is particularly useful for generating optical pulses of selected temporal shape over a wide range of pulse duration, such pulses finding application in the fields of optical communication, optical recording and data storage, atomic and molecular spectroscopy and laser fusion. An optical streak camera is also provided which uses SBD to display the beam intensity in the focal plane as a function of time during the input pulse. 10 figures.

  3. System for generating shaped optical pulses and measuring optical pulses using spectral beam deflection (SBD)

    DOEpatents

    Skupsky, Stanley; Kessler, Terrance J.; Letzring, Samuel A.

    1993-01-01

    A temporally shaped or modified optical output pulse is generated from a bandwidth-encoded optical input pulse in a system in which the input pulse is in the form of a beam which is spectrally spread into components contained within the bandwidth, followed by deflection of the spectrally spread beam (SBD) thereby spatially mapping the components in correspondence with the temporal input pulse profile in the focal plane of a lens, and by spatially selective attenuation of selected components in that focal plane. The shaped or modified optical output pulse is then reconstructed from the attenuated spectral components. The pulse-shaping system is particularly useful for generating optical pulses of selected temporal shape over a wide range of pulse duration, such pulses finding application in the fields of optical communication, optical recording and data storage, atomic and molecular spectroscopy and laser fusion. An optical streak camera is also provided which uses SBD to display the beam intensity in the focal plane as a function of time during the input pulse.

  4. Analysis of Mg spectral features produced by irradiations of laser pulses with different contrast and pulse durations

    NASA Astrophysics Data System (ADS)

    Stafford, A.; Safronova, A. S.; Safronova, U. I.; Kantsyrev, V. L.; Faenov, A. Y.; Wiewior, P.; Weller, M. E.; Shrestha, I.; Shlyaptseva, V. V.; Paudel, Y.

    2014-03-01

    Experiments performed at the Leopard Laser Facility at the Nevada Terawatt Facility of the University of Nevada, Reno have produced K-shell Mg spectra with complex satellite features. K-shell Mg spectra were collected from experiments comprised of three different conditions related to laser pulse and contrast. Two spectrometers were fielded: a survey convex spectrometer with a potassium hydrogen phthalate (KAP) crystal (R ˜ 300) and a high resolution focusing spectrometer with spatial resolution using a spherically bent mica crystal (R ˜ 3000). These spectra included dielectronic satellite (DS) lines that were investigated using the quasi-relativistic many-body perturbation theory (MZ) code for previously identified transitions from autoionizing 2lnl‧ states in He-like Mg and new transitions involving autoionizing 1s3lnl‧ states in Li-like Mg and 1s3l3l‧3l″ in Be-like Mg calculated using the Hartree-Fock-relativistic method (COWAN code). Radiative and non-radiative data are combined to obtain branching ratios, intensities and effective emission rate coefficients of DS lines. Synthetic spectra were matched to experimental data to identify strong satellite structures to the Heβ (7.8507 Å) and Lyα (8.4192 Å) resonance transitions.

  5. Plasma Sensor Measurements in Pulse Detonation Engines

    NASA Astrophysics Data System (ADS)

    Matlis, Eric; Marshall, Curtis; Corke, Thomas; Gogineni, Sivaram

    2014-11-01

    Measurements have been conducted in a pulse detonation and rotating detonation engine using a newly developed plasma sensor. This sensor relies on the novel approach of using an ac-driven, weakly-ionized electrical discharge as the main sensing element. The advantages of this approach include a native high bandwidth of 1 MHz without the need for electronic frequency compensation, a dual-mode capability that provides sensitivity to multiple flow parameters, including velocity, pressure, temperature, and gas-species, and a simple and robust design making it very cost effective. The sensor design is installation-compatible with conventional sensors commonly used in gas-turbine research such as the Kulite dynamic pressure sensor while providing much better longevity. Developmental work was performed in high temperature facilities that are relevant to the propulsion and high-speed research community. This includes tests performed in a J85 augmentor at full afterburner and pulse-detonation engines at the University of Cincinnati (UC) at temperatures approaching 2760°C (5000°F).

  6. Sensitivity enhancement in pulse EPR distance measurements.

    PubMed

    Jeschke, G; Bender, A; Paulsen, H; Zimmermann, H; Godt, A

    2004-07-01

    Established pulse EPR approaches to the measurement of small dipole-dipole couplings between electron spins rely on constant-time echo experiments to separate relaxational contributions from dipolar time evolution. This requires a compromise between sensitivity and resolution to be made prior to the measurement, so that optimum data are only obtained if the magnitude of the dipole-dipole coupling is known beforehand to a good approximation. Moreover, the whole dipolar evolution function is measured with relatively low sensitivity. These problems are overcome by a variable-time experiment that achieves suppression of the relaxation contribution by reference deconvolution. Theoretical and experimental results show that this approach leads to significant sensitivity improvements for typical systems and experimental conditions. Further sensitivity improvements or, equivalently, an extension of the accessible distance range can be obtained by matrix deuteration or digital long-pass filtering of the time-domain data. Advantages and limitations of the new variable-time experiment are discussed by comparing it to the established analogous constant-time experiment for measurements of end-to-end distances of 5 and 7.5 nm on rod-like shape-persistent biradicals and for the measurement of a broadly distributed transmembrane distance in a doubly spin-labeled mutant of plant light harvesting complex II. PMID:15183350

  7. Influence of wavelength and pulse duration on single-shot x-ray diffraction patterns from nonspherical nanoparticles

    NASA Astrophysics Data System (ADS)

    Sander, Katharina; Peltz, Christian; Varin, Charles; Scheel, Stefan; Brabec, Thomas; Fennel, Thomas

    2015-10-01

    We introduce a complex scaling discrete dipole approximation (CSDDA) method and study single-shot x-ray diffraction patterns from non-spherical, absorbing nanotargets in the limit of linear response. The convergence of the employed Born series-based iterative solution of the discrete dipole approximation problem via optimal complex mixing turns out to be substantially faster than the original approach with real-valued mixing coefficients, without additional numerical effort per iteration. The CSDDA method is employed to calculate soft x-ray diffraction patterns from large icosahedral silver nanoparticles with diameters up to about 250 {nm}. Our analysis confirms the requirement of relatively long wavelengths to map truly 3D structure information to the experimentally accessible regions of 2D scattering images. On the other hand, we show that short wavelengths are preferable to retain visibility of fine structures such as interference fringes in the scattering patterns when using ultrashort x-ray pulses in the attosecond domain. A simple model is presented to estimate the minimal pulse duration below which the fringe contrast vanishes. Knowledge of the impact of the bandwidth of short pulses on the diffraction images is important to extract information on ultrafast dynamical processes from time-resolved x-ray diffractive imaging experiments on free nanoparticles, in particular at long wavelengths.

  8. Generation of high-quality parabolic pulses with optimized duration and energy by use of dispersive frequency-to-time mapping.

    PubMed

    Huh, Jeonghyun; Azaña, José

    2015-10-19

    We propose and demonstrate a novel linear-optics method for high-fidelity parabolic pulse generation with durations ranging from the picosecond to the sub-nanosecond range. This method is based on dispersion-induced frequency-to-time mapping combined with spectral shaping in order to overcome constraints of previous linear shaping approaches. Temporal waveform distortions associated with the need to satisfy a far-field condition are eliminated by use of a virtual time-lens process, which is directly implemented in the linear spectral shaping stage. Using this approach, the generated parabolic pulses are able to maintain most energy spectrum available from the input pulse frequency bandwidth, regardless of the target pulse duration, which is not anymore limited by the finest spectral resolution of the optical pulse spectrum shaper. High-quality parabolic pulses, with durations from 25ps to 400ps and output powers exceeding 4dBm before amplification, have been experimentally synthesized from a picosecond mode-locked optical source using a commercial optical pulse shaper with a frequency resolution >10GHz. In particular, we report the synthesis of full-duty cycle parabolic pulses that match up almost exactly with an ideal fitting over the entire pulse period. PMID:26480437

  9. Pulse duration effects on laser-assisted electron transfer cross section for He2+ ions colliding with atomic hydrogen

    NASA Astrophysics Data System (ADS)

    Domínguez-Gutiérrez, Francisco Javier; Cabrera-Trujillo, Remigio

    2014-08-01

    We study the effect of the pulse duration for an ultra-fast and intense laser on the fundamental process of electron capture by analyzing the excitation probability into the n = 2 and n = 3 states when He2+ collides with atomic hydrogen in the 0.05-10 keV/amu energy range, a region of interest for diagnostic processes on plasma and fusion power reactors. We solve the time-dependent Schrödinger equation to calculate the electron capture probability by means of a finite-differences, as well as by an electron-nuclear dynamics approach. In particular, we study the effects of 1, 3, 6, and 10 fs laser pulses at FWHM, wavelength of 780 nm and intensity of 3.5 × 1012 W/cm2. We report good agreement for the laser-free state and total electron transfer cross-sections when compared to available theoretical and experimental data. The effect of the laser pulse on the electron capture probability as a function of the impact parameter is such that the charge exchange probability increases considerably in the impact parameter radial region with an increase in the amplitude oscillations and a phase shift on the Stückelberg oscillations. We find an increase on the total electron exchange cross-section for low projectile collision energy when compared to the laser-free case with a minimal effect at high collision energies. We find that the 1 fs laser pulse has a minimal effect, except for very low collision energies. Although in general, the longer the laser pulse, the larger the electron capture probability, at very low collision energies all pulse widths have an effect. For processes in the atto-second region, our findings suggest that to enhance the laser-assisted charge exchange, the best region for short pulses is at very low collision energies. We also find that the s and p state charge exchange cross section are equally affected. We provide a qualitative discussion of these findings.

  10. Pulsed laser Doppler measurements of wind shear

    NASA Technical Reports Server (NTRS)

    Dimarzio, C.; Harris, C.; Bilbro, J. W.; Weaver, E. A.; Burnham, D. C.; Hallock, J. N.

    1979-01-01

    There is a need for a sensor at the airport that can remotely detect, identify, and track wind shears near the airport in order to assure aircraft safety. To determine the viability of a laser wind-shear system, the NASA pulsed coherent Doppler CO2 lidar (Jelalian et al., 1972) was installed in a semitrailer van with a rooftop-mounted hemispherical scanner and was used to monitor thunderstorm gust fronts. Wind shears associated with the gust fronts at the Kennedy Space Center (KSC) between 5 July and 4 August 1978 were measured and tracked. The most significant data collected at KSC are discussed. The wind shears were clearly visible in both real-time velocity vs. azimuth plots and in postprocessing displays of velocities vs. position. The results indicate that a lidar system cannot be used effectively when moderate precipitation exists between the sensor and the region of interest.

  11. The effect of pulse duration on the growth rate of laser-induced damage sites at 351 nm on fused silica surfaces

    SciTech Connect

    Negres, R A; Norton, M A; Liao, Z M; Cross, D A; Bude, J D; Carr, C W

    2009-10-29

    Past work in the area of laser-induced damage growth has shown growth rates to be primarily dependent on the laser fluence and wavelength. More recent studies suggest that growth rate, similar to the damage initiation process, is affected by a number of additional parameters including pulse duration, pulse shape, site size, and internal structure. In this study, we focus on the effect of pulse duration on the growth rate of laser damage sites located on the exit surface of fused silica optics. Our results demonstrate, for the first time, a significant dependence of growth rate at 351 nm on pulse duration from 1 ns to 15 ns as {tau}{sup 0.3} for sites in the 50-100 {micro}m size range.

  12. Rotational CARS Temperature Measurements in Nanosecond Pulse Discharge Plasmas

    NASA Astrophysics Data System (ADS)

    Zuzeek, Yvette; Takashima, Keisuke; Adamovich, Igor; Lempert, Walter

    2009-10-01

    Time-resolved and spatially resolved temperatures in repetitively pulsed nanosecond discharges in air and ethylene-air mixtures have been measured by purely rotational Coherent Anti-Stokes Raman Specroscopy (CARS). The experiments have been done in a capacitively coupled plane-to-plane discharge and in an atmospheric pressure near-surface Dielectric Barrier Discharge (DBD), both powered by repetitive nanosecond duration voltage pulses. Gated ICCD camera images demonstrated that the capacitively coupled discharge plasma remains diffuse and stable, with no sign of arc filaments. Comparison of the experimental results with plasma chemical kinetic modeling calculations shows good agreement. The results demonstrate that the rate of heating in the fuel-air plasma is significantly more rapid compared to the one in the air plasma. Kinetic model analysis shows that this occurs due to exothermic reactions of fuel with radical species generated in the plasma, such as O atoms. The present results provide additional insight into kinetics of hydrocarbon fuel oxidation in low-temperature plasmas and into the mechanism of localized heating of air flows by nanosecond DBD discharges.

  13. Evolution dynamics of charge state distribution in neon interaction with x-ray pulses of variant intensities and durations

    NASA Astrophysics Data System (ADS)

    Gao, Cheng; Zeng, Jiaolong; Yuan, Jianmin

    2015-03-01

    The level population and charge state distribution (CSD) of the neon atomic system interacting with x-ray pulses of variant intensities and durations at a central photon energy of 1110 eV are investigated by solving the time-dependent rate equations. The laser beam has a circular spot size with a Gaussian intensity pattern and the time history of the intensity is represented by Gaussian distribution in time. As an example, the CSD as a function of time is given at different distances from the spot center for an x-ray beam of intensity 1.5 × 1017 W/cm2 and duration 75 fs (fs) for a spot size of 1 μm (full width at half maximum). The final CSD after averaging over the space and time is compared with a recent experiment and good agreement is found between the theory and experiment. Then systematic investigations are carried out to study the evolution of CSD with a wide range of intensity from 1.0 × 1015 W/cm2 to 1.0 × 1019 W/cm2 and duration from 30 fs to 100 fs. The results show that at intensities lower than 1.0 × 1015 W/cm2, the CSD shows a typical physical picture of weak x-ray photoionization of the neutral atomic neon. At higher intensity, i.e., larger than 5.0 × 1016 W/cm2, the dominant ionization stages are Ne7+ and Ne8+, while the fractions of ions in the Ne3+-Ne6+ stages are low for all laser durations and intensities.

  14. A new sealed RF-excited CO2 laser for enamel ablation operating at 9.4μm with pulse duration of 26 μs

    NASA Astrophysics Data System (ADS)

    Chan, Kenneth H.; Jew, Jamison M.; Fried, Daniel

    2016-02-01

    Several studies over the past 20 years have identified that carbon dioxide lasers operating at wavelengths between 9.3 and 9.6-μm with pulse durations near 20-µs are ideal for hard tissue ablation. Those wavelengths are coincident with the peak absorption of the mineral phase and the pulse duration is close to the thermal relaxation time of the deposited energy of a few microseconds to minimize peripheral thermal damage and long enough to minimize plasma shielding effects to allow efficient ablation at practical rates. The desired pulse duration near 20-μs has been difficult to achieve since it is too long for TEA lasers and too short for RF-excited lasers for efficient operation. Recently, Coherent Inc. (Santa Clara, CA) developed the J5-V laser for microvia drilling which can produce laser pulses greater than 100 mJ in energy at 9.4-μm with a pulse duration of 26-µs and it can achieve pulse repetition rates of 3 KHz. We report the first results using this laser to ablate enamel and dentin. The onset of plasma shielding does not occur until the fluence exceeds 100 J/cm2 allowing efficient ablation at rates exceeding 50-μm per pulse. This laser is ideally suited for the selective ablation of carious lesions.

  15. Convoluted effect of laser fluence and pulse duration on the property of a nanosecond laser-induced plasma into an argon ambient gas at the atmospheric pressure

    SciTech Connect

    Bai Xueshi; Ma Qianli; Motto-Ros, Vincent; Yu Jin; Sabourdy, David; Nguyen, Luc; Jalocha, Alain

    2013-01-07

    We studied the behavior of the plasma induced by a nanosecond infrared (1064 nm) laser pulse on a metallic target (Al) during its propagation into argon ambient gas at the atmospheric pressure and especially over the delay interval ranging from several hundred nanoseconds to several microseconds. In such interval, the plasma is particularly interesting as a spectroscopic emission source for laser-induced plasma spectroscopy (LIBS). We show a convoluted effect between laser fluence and pulse duration on the structure and the emission property of the plasma. With a relatively high fluence of about 160 J/cm{sup 2} where a strong plasma shielding effect is observed, a short pulse of about 4 ns duration is shown to be significantly more efficient to excite the optical emission from the ablation vapor than a long pulse of about 25 ns duration. While with a lower fluence of about 65 J/cm{sup 2}, a significantly more efficient excitation is observed with the long pulse. We interpret our observations by considering the post-ablation interaction between the generated plume and the tailing part of the laser pulse. We demonstrate that the ionization of the layer of ambient gas surrounding the ablation vapor plays an important role in plasma shielding. Such ionization is the consequence of laser-supported absorption wave and directly dependent on the laser fluence and the pulse duration. Further observations of the structure of the generated plume in its early stage of expansion support our explanations.

  16. Effects of Biphasic Current Pulse Frequency, Amplitude, Duration and Interphase Gap on Eye Movement Responses to Prosthetic Electrical Stimulation of the Vestibular Nerve

    PubMed Central

    Davidovics, Natan S.; Fridman, Gene Y.; Chiang, Bryce; Della Santina, Charles C.

    2011-01-01

    An implantable prosthesis that stimulates vestibular nerve branches to restore sensation of head rotation and vision-stabilizing reflexes could benefit individuals disabled by bilateral loss of vestibular (inner ear balance) function. We developed a prosthesis that partly restores normal function in animals by delivering pulse frequency modulated (PFM) biphasic current pulses via electrodes implanted in semicircular canals. Because the optimal stimulus encoding strategy is not yet known, we investigated effects of varying biphasic current pulse frequency, amplitude, duration and interphase gap on vestibulo-ocular reflex (VOR) eye movements in chinchillas. Increasing pulse frequency increased response amplitude while maintaining a relatively constant axis of rotation. Increasing pulse amplitude (range 0–325 μA) also increased response amplitude but spuriously shifted eye movement axis, probably due to current spread beyond the target nerve. Shorter pulse durations (range 28–340 μs) required less charge to elicit a given response amplitude and caused less axis shift than longer durations. Varying interphase gap (range 25–175 μs) had no significant effect. While specific values reported herein depend on microanatomy and electrode location in each case, we conclude that PFM with short duration biphasic pulses should form the foundation for further optimization of stimulus encoding strategies for vestibular prostheses intended to restore sensation of head rotation. PMID:20813652

  17. Dependence of the absorption of pulsed CO{sub 2}-laser radiation by silane on wavenumber, fluence, pulse duration, temperature, optical path length, and pressure of absorbing and nonabsorbing gases

    SciTech Connect

    Blazejowski, J.; Gruzdiewa, L.; Rulewski, J.; Lampe, F.W.

    1995-05-15

    The absorption of three lines [{ital P}(20), 944.2 cm{sup {minus}1}; {ital P}(14), 949.2 cm{sup {minus}1}; and {ital R}(24), 978.5 cm{sup {minus}1}] of the pulsed CO{sub 2} laser (00{sup 0}1--10{sup 0}0 transition) by SiH{sub 4} was measured at various pulse energy, pulse duration, temperature, optical path length, and pressure of the compound and nonabsorbing foreign gases. In addition, low intensity infrared absorption spectrum of silane was compared with high intensity absorption characteristics for all lines of the pulsed CO{sub 2} laser. The experimental dependencies show deviations from the phenomenological Beer--Lambert law which can be considered as arising from the high intensity of an incident radiation and collisions of absorbing molecules with surroundings. These effects were included into the expression, being an extended form of the Beer--Lambert law, which reasonably approximates all experimental data. The results, except for extending knowledge on the interaction of a high power laser radiation with matter, can help understanding and planning processes leading to preparation of silicon-containing technologically important materials.

  18. Measurement Issues In Pulsed Laser Propulsion

    SciTech Connect

    Sinko, John E.; Scharring, Stefan; Eckel, Hans-Albert; Roeser, Hans-Peter; Sasoh, Akihiro

    2010-05-06

    Various measurement techniques have been used throughout the over 40-year history of laser propulsion. Often, these approaches suffered from inconsistencies in definitions of the key parameters that define the physics of laser ablation impulse generation. Such parameters include, but are not limited to the pulse energy, spot area, imparted impulse, and ablated mass. The limits and characteristics of common measurement techniques in each of these areas will be explored as they relate to laser propulsion. The idea of establishing some standardization system for laser propulsion data is introduced in this paper, so that reported results may be considered and studied by the general community with more certain understanding of particular merits and limitations. In particular, it is the intention to propose a minimum set of requirements a literature study should meet. Some international standards for measurements are already published, but modifications or revisions of such standards may be necessary for application to laser ablation propulsion. Issues relating to development of standards will be discussed, as well as some examples of specific experimental circumstances in which standardization would have prevented misinterpretation or misuse of past data.

  19. A very high sensitivity RF pulse profile measurement system.

    SciTech Connect

    Christodoulou, Christos George; Lai, Jesse B.

    2009-06-01

    A technique for characterizing the pulse profile of a radio-frequency (RF) amplifier over a very wide power range under fast-pulsing conditions is presented. A pulse-modulated transmitter is used to drive a device under test (DUT) with a phase-coded signal that allows for an increased measurement range beyond standard techniques. A measurement receiver that samples points on the output pulse power profile and performs the necessary signal processing and coherent pulse integration, improving the detectability of low-power signals, is described. The measurement technique is applied to two sample amplifiers under fast-pulsing conditions with a pulsewidth of 250 ns at 3-GHz carrier frequency. A full measurement range of greater than 160 dB is achieved, extending the current state of the art in pulse-profiling techniques.

  20. Induced Radioactivity Measured in a Germanium Detector After a Long Duration Balloon Flight

    NASA Technical Reports Server (NTRS)

    Starr, R.; Evans, L. G.; Floyed, S. R.; Drake, D. M.; Feldman, W. C.; Squyres, S. W.; Rester, A. C.

    1997-01-01

    A 13-day long duration balloon flight carrying a germanium detector was flown from Williams Field, Antartica in December 1992. After recovery of the payload the activity induced in the detector was measured.

  1. Lidar sensing of the atmosphere with gigawatt laser pulses of femtosecond duration

    SciTech Connect

    Bukin, O A; Golik, S S; Il'in, A A; Kulchin, Yu N; Lisitsa, V V; Shmirko, K A; Babii, M Yu; Kolesnikov, A V; Kabanov, A M; Matvienko, G G; Oshlakov, V K

    2014-06-30

    We present the results of sensing of the atmosphere in the condition of a transition 'continent – ocean' zone by means of gigawatt femtosecond pulses of the fundamental and second harmonics of a Ti : sapphire laser. In the regime of multi-frequency sensing (supercontinuum from the fundamental harmonic) the emission lines of the first positive system of the nitrogen molecule B{sup 3}Π{sub g} – A{sup 3}Σ{sub u}{sup +} have been recorded, while the sensing using of the second harmonic have revealed the possibility of detecting the lines of Raman scattering of nitrogen (λ = 441 nm). The intensity ratio of the line of Raman scattering of nitrogen and the line of elastic scattering at the wavelength of λ = 400 nm amounts to 5.6 × 10{sup -4}. (extreme light fields and their applications)

  2. Intense-Field Ionization of Monoaromatic Hydrocarbons using Radiation Pulses of Ultrashort Duration: Monohalobenzenes and Azabenzenes

    NASA Astrophysics Data System (ADS)

    Scarborough, T.; Strohaber, J.; Foote, D.; McAcy, C.; Uiterwaal, C. J.

    2014-04-01

    Using 50-fs, 800-nm pulses, we study the intense-field ionization and fragmentation of the monohalobenzenes C6H5-X (X=F, Cl, Br, I) and of the heterocyclics azabenzene C5H5N (pyridine) and the three diazabenzenes C4H4N2 (pyridazine, pyrimidine, and pyrazine). Avoiding focal intensity averaging we find indications of resonance-enhanced MPI. In the monohalobenzenes the propensity for fragmentation increases for increasing Z: fluorobenzene yields predominantly C6H5Fn+, while iodobenzene yields atomic ions with charges up to I8+. We ascribe this to the heavy-atom effect: the large charge of the heavy halogens' nuclei induces ultrafast intersystem crossing to dissociative triplet states.

  3. Long duration measurements of whole-body vibration exposures associated with surface coal mining equipment compared to previous short-duration measurements.

    PubMed

    Burgess-Limerick, Robin; Lynas, Danellie

    2016-01-01

    Previous measurements of whole-body vibration associated with earth-moving equipment at surface coal mines have highlighted the significance of the hazard. Considerable variability in measurement amplitudes, even within the same equipment type operated at the same site, has been noted. However, the measurements have previously been undertaken for relatively short durations. Fifty-nine measurements were collected from a range of earth-moving equipment in operation at a surface coal mine. Measurement durations ranged from 100-460 min (median = 340 min). The results indicate that the measurements previously observed are not an artifact of the relatively short durations and confirm that operators of dozers and off-road haul trucks, in particular, are frequently exposed to vertical whole-body vibration levels which lie within, or above, the Health Guidance Caution Zone defined by ISO2631.1. Further investigations are justified to identify opportunities for reducing operators' exposure to high amplitude vibrations. PMID:26771238

  4. Measuring 8–250 ps short pulses using a high-speed streak camera on kilojoule, petawatt-class laser systems

    SciTech Connect

    Qiao, J.; Jaanimagi, P. A.; Boni, R.; Bromage, J.; Hill, E.

    2013-07-15

    Short-pulse measurements using a streak camera are sensitive to space-charge broadening, which depends on the pulse duration and shape, and on the uniformity of photocathode illumination. An anamorphic-diffuser-based beam-homogenizing system and a space-charge-broadening calibration method were developed to accurately measure short pulses using an optical streak camera. This approach provides a more-uniform streak image and enables one to characterize space-charge-induced pulse-broadening effects.

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

    NASA Astrophysics Data System (ADS)

    Afeyan, Bedros

    2013-10-01

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

  6. Laser Activated Streak Camera for Measurement of Electron Pulses with Femtosecond Resolution

    NASA Astrophysics Data System (ADS)

    Zandi, Omid; Desimone, Alice; Wilkin, Kyle; Yang, Jie; Centurion, Martin

    2015-05-01

    The duration of femtosecond electron pulses used in time-resolved diffraction and microscopy experiments is challenging to measure in-situ. To overcome this problem, we have fabricated a streak camera that uses the time-varying electric field of a discharging parallel plate capacitor. The capacitor is discharged using a laser-activated GaAs photoswitch, resulting in a damped oscillation of the electric field. The delay time between the laser pulse and electron pulse is set so that the front and back halves of the bunch encounter opposite electric fields of the capacitor and are deflected in opposite directions. Thus, the electron bunch appears streaked on the detector with a length proportional to its duration. The temporal resolution of the streak camera is proportional to the maximum value of the electric field and the frequency of the discharge oscillation. The capacitor is charged by high voltage short pulses to achieve a high electric field and prevent breakdown. We have achieved an oscillation frequency in the GHz range by reducing the circuit size and hence its inductance. The camera was used to measure 100 keV electron pulses with up to a million electrons that are compressed transversely by magnetic lenses and longitudinally by an RF cavity. This work was supported mainly by the Air Force Office of Scientific Research, Ultrashort Pulse Laser Matter Interaction program, under grant # FA9550-12-1-0149.

  7. Pulse transit time differential measurement by fiber Bragg grating pulse recorder

    NASA Astrophysics Data System (ADS)

    Umesh, Sharath; Padma, Srivani; Ambastha, Shikha; Kalegowda, Anand; Asokan, Sundarrajan

    2015-05-01

    The present study reports a noninvasive technique for the measurement of the pulse transit time differential (PTTD) from the pulse pressure waveforms obtained at the carotid artery and radial artery using fiber Bragg grating pulse recorders (FBGPR). PTTD is defined as the time difference between the arrivals of a pulse pressure waveform at the carotid and radial arterial sites. The PTTD is investigated as an indicator of variation in the systolic blood pressure. The results are validated against blood pressure variation obtained from a Mindray Patient Monitor. Furthermore, the pulse wave velocity computed from the obtained PTTD is compared with the pulse wave velocity obtained from the color Doppler ultrasound system and is found to be in good agreement. The major advantage of the PTTD measurement via FBGPRs is that the data acquisition system employed can simultaneously acquire pulse pressure waveforms from both FBGPRs placed at carotid and radial arterial sites with a single time scale, which eliminates time synchronization complexity.

  8. Formation of an electron beam with a duration shorter than 100 fs during photoemission of electrons by femtosecond laser pulses

    SciTech Connect

    Mironov, B. N.; Aseev, S. A. Minogin, V. G. Chekalin, S. V.

    2008-06-15

    Irradiation of a thin metal target by 38-fs laser pulses at a wavelength of 800 nm is shown to generate a beam of photoelectrons that contains a component whose duration is shorter than 100 fs. The ensemble of photoelectrons is formed by photoemission of a gold film about 10 nm thick sputtered on the base of a prism made of fused silica. The laser beam irradiates a dielectric-metal interface and propagates inside the prism at an angle of 45{sup o} to a normal to the interface. The photoelectron beam is formed by accelerating photoelectrons in a spatially inhomogeneous electrostatic potential. The ultrashort component of the photoelectron beam is found to be formed under the action of a ponderomotive potential. It is shown that the ultrashort electron component can be separated from the remaining part of the photoelectron beam with the help of an inhomogeneous electrostatic field.

  9. Effect of dye laser pulse duration on selective cutaneous vascular injury

    SciTech Connect

    Garden, J.M.; Tan, O.T.; Kerschmann, R.; Boll, J.; Furumoto, H.; Anderson, R.R.; Parrish, J.A.

    1986-11-01

    The pulsed dye laser at 577 nm, a wavelength well absorbed by oxyhemoglobin, causes highly selective thermal injury to cutaneous blood vessels. Confinement of thermal damage to microvessels is, in theory, related to the laser exposure time (pulsewidth) on selective vascular injury. This study investigates the effect of 577 nm dye laser pulsewidth on selective vascular injury. Nine Caucasian, normal volunteers received 577 nm dye laser exposures at pulsewidths of 1.5-350 microseconds to their skin. Clinical purpura threshold exposure doses were determined in each volunteer, and biopsies of threshold and suprathreshold doses were examined in each volunteer. The laser exposure dose required to produce purpura increased as pulsewidth increased in all 9 subjects (p less than 0.001). This finding corresponds to laser pulsewidths equal to or exceeding the thermal relaxation times for dermal blood vessels. Histologically, vessel damage was selectively, but qualitatively, different for short vs long pulsewidths. Pulsewidths shorter than 20 microseconds caused vessel wall fragmentation and hemorrhage, whereas longer pulsewidths caused no significant hemorrhage. The purpura noted clinically appears to be due to a coagulum of intralumenal denatured erythrocytes. At 24 h, there was marked vessel wall necrosis at all pulsewidths. The short pulsewidths may cause erythrocyte vaporization, rapid thermal expansion, and mechanical vessel rupture with hemorrhage. Long pulsewidths appear to cause thermal denaturation with less mechanical vessel damage. The selective, nonhemorrhagic, vascular necrosis caused by the long-pulsewidth dye laser may lead to a more desirable clinical outcome in the therapy of blood vessel disease processes.

  10. Comparison of Echocardiographic Measurements Before and After Short and Long Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Fritsch-Yelle, Janice M.; South, Donna A.; Wood, Margie L.; Bungo, Michael W.

    2000-01-01

    Previous echocardiography studies in astronauts before and after short duration (4 - 17 days) missions have demonstrated a decrease in resting left ventricular (LV) stroke volume (SV), but maintained ejection fraction (EF) and cardiac output. Similar studies before and after long duration (129 - 144 days) spaceflight have been rare and their overall results equivocal. The purpose of this work was to compare the echocardiographic measurements (M-mode, 2-D and Doppler) from short duration (n = 13) and long duration (n = 4) crewmembers. Compared to short duration astronauts, long duration crewmembers had a significantly greater percent decrease in EF (+6+/-0.02 vs.-10.5+/-0.03, p = 0.005) and percent fractional shortening (+7+/-0.03 vs. -11+/-0.07, p = 0.0 15), and an increase in LV end systolic volume (-12+/-0.06 vs. +39+/-0.24, p = 0.011). These data suggest a reduction in cardiac function that relates to mission duration. As the changes in blood pressure and circulating blood volume (9% - 12%) are reported to be similar after short and long duration flights, the drop in EF after longer spaceflights is likely due to a decrease in cardiac function rather than altered blood volume.

  11. Objectively Measured Walking Duration and Sedentary Behaviour and Four-Year Mortality in Older People

    PubMed Central

    Denkinger, Michael Dieter; Rapp, Kilian; Koenig, Wolfgang; Rothenbacher, Dietrich

    2016-01-01

    Background Physical activity is an important component of health. Recommendations based on sensor measurements are sparse in older people. The aim of this study was to analyse the effect of objectively measured walking and sedentary duration on four-year mortality in community-dwelling older people. Methods Between March 2009 and April 2010, physical activity of 1271 participants (≥65 years, 56.4% men) from Southern Germany was measured over one week using a thigh-worn uni-axial accelerometer (activPAL; PAL Technologies, Glasgow, Scotland). Mortality was assessed during a four-year follow-up. Cox-proportional-hazards models were used to estimate the associations between walking (including low to high intensity) and sedentary duration with mortality. Models were adjusted for age and sex, additional epidemiological variables, and selected biomarkers. Results An inverse relationship between walking duration and mortality with a minimum risk for the 3rd quartile (102.2 to128.4 minutes walking daily) was found even after multivariate adjustment with HRs for quartiles 2 to 4 compared to quartile 1 of 0.45 (95%-CI: 0.26; 0.76), 0.18 (95%-CI: 0.08; 0.41), 0.39 (95%-CI: 0.19; 0.78), respectively. For sedentary duration an age- and sex-adjusted increased mortality risk was observed for the 4th quartile (daily sedentary duration ≥1137.2 min.) (HR 2.05, 95%-CI: 1.13; 3.73), which diminished, however, after full adjustment (HR 1.63, 95%-CI: 0.88; 3.02). Furthermore, our results suggest effect modification between walking and sedentary duration, such that in people with low walking duration a high sedentary duration was noted as an independent factor for increased mortality. Conclusions In summary, walking duration was clearly associated with four-year overall mortality in community-dwelling older people. PMID:27082963

  12. Phase control and measurement of ultrashort optical pulses

    SciTech Connect

    Sullivan, A.; White, W.E.; Chu, K.C.; Heritage, J.P.

    1995-02-10

    We have used the Direct Optical Spectral Phase Measurement (DOSPM) technique to characterize the cubic phase tuning ability of our pulse stretcher. We have compared the measured phase to the phase determined from cross-correlation measurements.

  13. Phase measurement of fast light pulse in electromagnetically induced absorption.

    PubMed

    Lee, Yoon-Seok; Lee, Hee Jung; Moon, Han Seb

    2013-09-23

    We report the phase measurement of a fast light pulse in electromagnetically induced absorption (EIA) of the 5S₁/₂ (F = 2)-5P₃/₂ (F' = 3) transition of ⁸⁷Rb atoms. Using a beat-note interferometer method, a stable measurement without phase dithering of the phase of the probe pulse before and after it has passed through the EIA medium was achieved. Comparing the phases of the light pulse in air and that of the fast light pulse though the EIA medium, the phase of the fast light pulse at EIA resonance was not shifted and maintained to be the same as that of the free-space light pulse. The classical fidelity of the fast light pulse according to the advancement of the group velocity by adjusting the atomic density was estimated to be more than 97%. PMID:24104135

  14. Effect of coil orientation on strength–duration time constant and I-wave activation with controllable pulse parameter transcranial magnetic stimulation

    PubMed Central

    D’Ostilio, Kevin; Goetz, Stefan M.; Hannah, Ricci; Ciocca, Matteo; Chieffo, Raffaella; Chen, Jui-Cheng A.; Peterchev, Angel V.; Rothwell, John C.

    2016-01-01

    Objective To compare the strength–duration (S–D) time constants of motor cortex structures activated by current pulses oriented posterior–anterior (PA) or anterior–posterior (AP) across the central sulcus. Methods Motor threshold and input–output curve, along with motor evoked potential (MEP) latencies, of first dorsal interosseus were determined at pulse widths of 30, 60, and 120 μs using a controllable pulse parameter (cTMS) device, with the coil oriented PA or AP. These were used to estimate the S–D time constant and we compared with data for responses evoked by cTMS of the ulnar nerve at the elbow. Results The S–D time constant with PA was shorter than for AP stimulation (230.9 ± 97.2 vs. 294.2 ± 90.9 μs; p < 0.001). These values were similar to those calculated after stimulation of ulnar nerve (197 ± 47 μs). MEP latencies to AP, but not PA stimulation were affected by pulse width, showing longer latencies following short duration stimuli. Conclusion PA and AP stimuli appear to activate the axons of neurons with different time constants. Short duration AP pulses are more selective than longer pulses in recruiting longer latency corticospinal output. Significance More selective stimulation of neural elements may be achieved by manipulating pulse width and orientation. PMID:26077634

  15. 47 W, 6 ns constant pulse duration, high-repetition-rate cavity-dumped Q-switched TEM(00) Nd:YVO(4) oscillator.

    PubMed

    McDonagh, Louis; Wallenstein, Richard; Knappe, Ralf

    2006-11-15

    We report on a cavity-dumped Q-switched TEM(00) Nd:YVO(4) oscillator offering a unique combination of high power, constant short pulse duration, and high repetition rate, suppressing the gain dependence of pulse duration in classical Q-switched oscillators. Its performance is compared with that of the same oscillator operated in a classical Q-switched regime, demonstrating the much higher peak powers achievable with this technique, especially at high repetition rates. Up to 31 W of 532 nm green light was generated by frequency doubling in a noncritical phase matched LBO crystal, corresponding to 70% conversion efficiency. PMID:17072404

  16. Fixation duration surpasses pupil size as a measure of memory load in free viewing

    PubMed Central

    Meghanathan, Radha Nila; van Leeuwen, Cees; Nikolaev, Andrey R.

    2015-01-01

    Oculomotor behavior reveals, not only the acquisition of visual information at fixation, but also the accumulation of information in memory across subsequent fixations. Two candidate measures were considered as indicators of such dynamic visual memory load: fixation duration and pupil size. While recording these measures, we displayed an arrangement of 3, 4 or 5 targets among distractors. Both occurred in various orientations. Participants searched for targets and reported whether in a subsequent display one of them had changed orientation. We determined to what extent fixation duration and pupil size indicate dynamic memory load, as a function of the number of targets fixated during the search. We found that fixation duration reflects the number of targets, both when this number is within and above the limit of working memory capacity. Pupil size reflects the number of targets only when it exceeds the capacity limit. Moreover, the duration of fixations on successive targets but not on distractors increases whereas pupil size does not. The increase in fixation duration with number of targets both within and above working memory capacity suggests that in free viewing fixation duration is sensitive to actual memory load as well as to processing load, whereas pupil size is indicative of processing load only. Two alternative models relating visual attention and working memory are considered relevant to these results. We discuss the results as supportive of a model which involves a temporary buffer in the interaction of attention and working memory. PMID:25653606

  17. Straining GOR tolerance determinations are a measure of G-duration not G-level tolerance.

    PubMed

    Burton, R R

    1999-03-01

    Straining gradual G onset rate (GOR) tolerances are considered by physiologists as a measure of G-level tolerance. Using recently developed G-level and G-duration mathematical models, it was found that straining GOR tolerances may well be a measure of tolerance to G-duration. G-duration tolerance was determined to be limited with the onset of fatigue and not cardiovascular insufficiency. G-level tolerances that were predicted using a mathematical model were higher than determined using straining GOR tolerance measurements of subjects on a centrifuge. Also the G-duration tolerance mathematical model showed that those centrifuge subjects had not expended all of their "energy reserve" during their sustained G exposure most probably because of the onset of fatigue. Even if they were able to use all of their potential energy reserve, their G-duration tolerance would not have allowed them to reach the maximum G-level predicted with the G-level tolerance model. It is therefore concluded that the straining GOR tolerance profile, with G onset rates of 0.1G/s, is not a measure of G-level tolerance, as has been assumed, but is a measure of G-duration tolerance. These findings have significant safety implications world-wide since this straining GOR profile is commonly used as a G-level tolerance fighter-pilot-selection determination; i.e. pilot selection standards for G-level tolerance are not a measure of G-level tolerance. In testing equipment design changes, the proper G tolerance profiles must be used to correctly measure its impact on G tolerance. PMID:11543406

  18. Measurement of performance using acceleration control and pulse control in simulated spacecraft docking operations

    NASA Technical Reports Server (NTRS)

    Brody, Adam R.; Ellis, Stephen R.

    1992-01-01

    Nine commercial airline pilots served as test subjects in a study to compare acceleration control with pulse control in simulated spacecraft maneuvers. Simulated remote dockings of an orbital maneuvering vehicle (OMV) to a space station were initiated from 50, 100, and 150 meters along the station's -V-bar (minus velocity vector). All unsuccessful missions were reflown. Five way mixed analysis of variance (ANOVA) with one between factor, first mode, and four within factors (mode, bloch, range, and trial) were performed on the data. Recorded performance measures included mission duration and fuel consumption along each of the three coordinate axes. Mission duration was lower with pulse mode, while delta V (fuel consumption) was lower with acceleration mode. Subjects used more fuel to travel faster with pulse mode than with acceleration mode. Mission duration, delta V, X delta V, Y delta V., and Z delta V all increased with range. Subjects commanded the OMV to 'fly' at faster rates from further distances. These higher average velocities were paid for with increased fuel consumption. Asymmetrical transfer was found in that the mode transitions could not be predicted solely from the mission duration main effect. More testing is advised to understand the manual control aspects of spaceflight maneuvers better.

  19. Short pulse duration shock initiation experiments plus ignition and growth modeling on Composition B

    NASA Astrophysics Data System (ADS)

    May, Chadd M.; Tarver, Craig M.

    2014-05-01

    Composition B (63% RDX, 36% TNT, 1% wax) is still a widely used energetic material whose shock initiation characteristics are necessary to understand. It is now possible to shock initiate Composition B and other secondary explosives at diameters well below their characteristic failure diameters for unconfined self-sustaining detonation. This is done using very high velocity, very thin, small diameter flyer plates accelerated by electric or laser power sources. Recently experimental detonation versus failure to detonate threshold flyer velocity curves for Composition B using several KaptonTM flyer thicknesses and diameters were measured. Flyer plates with diameters of 2 mm successfully detonated Composition B, which has a nominal failure diameter of 4.3 mm. The shock pressures required for these initiations are greater than the Chapman-Jouguet (C-J) pressure in self-sustaining Composition B detonation waves. The initiation process is two-dimensional, because both rear and side rarefactions can affect the shocked Composition B reaction rates. The Ignition and Growth reactive flow model for Composition B is extended to yield accurate simulations of this new threshold velocity data for various flyer thicknesses.

  20. Long Duration Exposure Facility (LDEF) attitude measurements of the interplanetary dust experiment

    NASA Technical Reports Server (NTRS)

    Kassel, Philip C., Jr.; Singer, S. Fred; Mulholland, J. Derral; Oliver, John P.; Weinberg, Jerry L.; Cooke, William J.; Wortman, Jim J.; Motley, William R., III

    1992-01-01

    The Long Duration Exposure Facility (LDEF) Interplanetary Dust Experiment (IDE) was unique in providing a time history of impacts of micron-sized particles on six orthogonal faces of LDEF during the first year in orbit. The value of this time resolved data depended on and was enhanced by the proper operation of some basic LDEF systems. Thus, the value of the data is greatly enhanced when the location and orientation of LDEF is known for each time of impact. The location and velocity of LDEF as a function of time can be calculated from the 'two-line elements' published by GSFC during the first year of the LDEF mission. The attitude of LDEF was passively stabilized in a gravity-gradient mode and a magnetically anchored viscous damper was used to dissipate roll, pitch, and yaw motions. Finally, the IDE used a standard LDEF Experiment Power and Data System (EPDS) to collect and store data and also to provide a crystal derived clock pulse (1 count every 13.1072 seconds) for all IDE time measurements. All that remained for the IDE was to provide a system to calibrate the clock, eliminating accumulative errors, and also verify the attitude of LDEF. The IDE used solar cells on six orthogonal faces to observe the LDEF sunrise and provide data about the LDEF attitude. The data was recorded by the EPDS about 10 times per day for the first 345 days of the LDEF mission. This data consist of the number of IDE counts since the last LDEF sunrise and the status of the six solar cells (light or dark) at the time of the last IDE count. The EPDS determined the time that data was recorded and includes, with each record, the master EPDS clock counter (1 count every 1.6384 seconds) that provided the range and resolution for time measurements. The IDE solar cells provided data for an excellent clock calibration, meeting their primary purpose, and the time resolved LDEF attitude measurements that can be gleaned from this data are presented.

  1. Proceedings of Pulsed Magnet Design and Measurement Workshop

    SciTech Connect

    Shaftan, T.; Heese, R.; Ozaki,S.

    2010-01-19

    The goals of the Workshop are to assess the design of pulsed system at the NSLS-II and establish mitigation strategies for critical issues during development. The focus of the Workshop is on resolving questions related to the set-up of the pulsed magnet laboratory, on measuring the pulsed magnet's current waveforms and fields, and on achieving tight tolerances on the magnet's alignment and field quality.

  2. Arterial pulse shape measurement using self-mixing inteferometry

    NASA Astrophysics Data System (ADS)

    Hast, Jukka T.; Myllyla, Risto A.; Sorvoja, Hannu; Miettinen, Jari

    2003-07-01

    This paper investigates the correlation between the shape of the first derivative of a blood pressure pulse and the corresponding Doppler spectrogram, reconstructed from a Doppler signal produced by the movement of the skin above the radial artery in the human wrist. The aim is to study to what extent the arterial pulse shape can be measured using self-mixing interferometry. To obtain a point of reference, a commercial non-invasive blood pressure monitor was first used to measure both blood pressure and pulse shape. Then, a self-mixing interferometer was applied to measure the arterial pulse above the radial artery. Measurements on 10 volunteers yielded a total of 738 pulses for analysis. A cross correlation of 0.84 +/- 0.05 was established between the shape of the first derivative of the pressure pulse and the Doppler spectrogram. Using an empirical constant of 0.7 as a limit for successfully detected pulses produced a detection accuracy of 95.7%. The results show that self-mixing interferometry lends itself to the measurement of the arterial pulse shape, and that the thus obtained shape is in good agreement with that produced by a commercial blood pressure monitor.

  3. Strip Velocity Measurements for Gated X-Ray Imagers Using Short Pulse Lasers

    SciTech Connect

    Ross, P. W.; Cardenas, M.; Griffin, M.; Mead, A.; Silbernagel, C. T.; Bell, P.; Haque, S. H.

    2013-09-01

    Strip velocity measurements of gated X-ray imagers are presented using an ultra-short pulse laser. Obtaining time-resolved X-ray images of inertial confinement fusion shots presents a difficult challenge. One diagnostic developed to address this challenge is the gated X-ray imagers. The gated X-ray detectors (GXDs) developed by Lawrence Livermore National Laboratory and Los Alamos National Laboratory use a microchannel plate (MCP) coated with a gold strip line, which serves as a photocathode. GXDs are used with an array of pinholes, which image onto various parts of the GXD image plane. As the pulse sweeps over the strip lines, it creates a time history of the event with consecutive images. In order to accurately interpret the timing of the images obtained using the GXDs, it is necessary to measure the propagation of the pulse over the strip line. The strip velocity was measured using a short pulse laser with a pulse duration of approximately 1-2 ps. The 200nm light from the laser is used to illuminate the GXD MCP. The laser pulse is split and a retroreflective mirror is used to delay one of the legs. By adjusting the distance to the mirror, one leg is temporally delayed compared to the reference leg. The retroreflective setup is calibrated using a streak camera with a 1 ns full sweep. Resolution of 0.5 mm is accomplished to achieve a temporal resolution of ~5 ps on the GXD strip line.

  4. Optical damage performance measurements of multilayer dielectric gratings for high energy short pulse lasers

    NASA Astrophysics Data System (ADS)

    Alessi, D.; Carr, C. W.; Negres, R. A.; Hackel, R. P.; Stanion, K. A.; Cross, D. A.; Guss, G.; Nissen, J. D.; Luthi, R.; Fair, J. E.; Britten, J. A.; Haefner, C.

    2015-02-01

    We investigate the laser damage resistance of multilayer dielectric (MLD) diffraction gratings used in the pulse compressors for high energy, high peak power laser systems such as the Advanced Radiographic Capability (ARC) Petawatt laser on the National Ignition Facility (NIF). Our study includes measurements of damage threshold and damage density (ρ(Φ)) with picosecond laser pulses at 1053 nm under relevant operational conditions. Initial results indicate that sparse defects present on the optic surface from the manufacturing processes are responsible for damage initiation at laser fluences below the damage threshold indicated by the standard R-on-1 test methods, as is the case for laser damage with nanosecond pulse durations. As such, this study supports the development of damage density measurements for more accurate predictions on the damage performance of large area optics.

  5. Low noise laser system generating 26-fs pulse duration, 30-kW peak power, and tunability from 800- to 1200-nm for ultrafast spectroscopy and multiphoton microscopy

    NASA Astrophysics Data System (ADS)

    Resan, Bojan; Brunner, Felix; Rohrbacher, Andreas; Ammann, Hubert; Weingarten, Kurt J.

    2012-01-01

    We demonstrate a novel low noise, tunable, high-peak-power, ultrafast laser system based on a SESAM-modelocked, solid-state Yb tungstate laser plus spectral broadening via a microstructured fiber followed by pulse compression. The spectral selection, tuning, and pulse compression are performed with a simple prism compressor. The spectral broadening and fiber parameters are chosen to insure low-noise operation of the tunable output. The long-term stable output pulses are tunable from 800 to 1200 nm, with a peak power up to 30 kW and pulse duration down to 26 fs. This system is attractive for variety of applications including ultrafast spectroscopy, multiphoton (TPE, SHG, THG, CARS) and multimodal microscopy, nanosurgery, nanostructuring, and optical coherence tomography (OCT). Such system is simpler, lower-cost, and much easier to use (fully turn-key) compared to a currently available solutions for near-infrared ultrashort pulses, typically a Ti:sapphire laser-pumped OPO.

  6. High-efficiency PPMgLN-based mid-infrared optical parametric oscillator pumped by a MOPA-structured fiber laser with long pulse duration

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Liu, Hao; Huang, Yuxiang; Shu, Rong

    2015-12-01

    We report our recent investigation on the conversion efficiency improvement of a PPMgLN-based single pump pass, singly resonant optical parametric oscillator (OPO) pumped by an acousto-optic Q-switched fiber MOPA. The impacts of the pump pulse duration and signal reflectivity on the pump-to-idler conversion efficiency were studied by numerically solving the coupled wave equations in the first place. The results revealed that longer pulse durations were beneficial to higher conversion efficiencies as long as the signal reflectivity of the OPO cavity was optimized accordingly. Experiments were carried out thereafter utilizing the optimal parameters obtained from the simulation. Idler powers of 4.7 and 3.81 W were achieved at 3.4 and 3.8 μm, respectively, under the highest pump power of 28 W with pump pulse duration of 240 ns. The experimental results were in good agreement with the calculated results. According to our simulation, higher conversion efficiency could be expected when such an OPO was pumped by pulses with even longer duration provided that the signal reflectivity of the output coupler was optimized under that pump condition.

  7. Mood Influences the Concordance of Subjective and Objective Measures of Sleep Duration in Older Adults

    PubMed Central

    Baillet, Marion; Cosin, Charlotte; Schweitzer, Pierre; Pérès, Karine; Catheline, Gwenaëlle; Swendsen, Joel; Mayo, Willy

    2016-01-01

    Objective/Background: Sleep plays a central role in maintaining health and cognition. In most epidemiologic studies, sleep is evaluated by self-report questionnaires but several reports suggest that these evaluations might be less accurate than objective measures such as polysomnography or actigraphy. Determinants of the discrepancy between objective and subjective measures remain to be investigated. The aim of this pilot-study was to examine the role of mood states in determining the discrepancy observed between objective and subjective measures of sleep duration in older adults. Patients/Methods: Objective sleep quantity and quality were recorded by actigraphy in a sample of 45 elderly subjects over at least three consecutive nights. Subjective sleep duration and supplementary data, such as mood status and memory, were evaluated using ecological momentary assessment (EMA). Results: A significant discrepancy was observed between EMA and actigraphic measures of sleep duration (p < 0.001). The magnitude of this difference was explained by the patient’s mood status (p = 0.020). No association was found between the magnitude of this discrepancy and age, sex, sleep quality or memory performance. Conclusion: The discrepancy classically observed between objective and subjective measures of sleep duration can be explained by mood status at the time of awakening. These results have potential implications for epidemiologic and clinical studies examining sleep as a risk factor for morbidity or mortality. PMID:27507944

  8. Industrial applications of high-average power high-peak power nanosecond pulse duration Nd:YAG lasers

    NASA Astrophysics Data System (ADS)

    Harrison, Paul M.; Ellwi, Samir

    2009-02-01

    Within the vast range of laser materials processing applications, every type of successful commercial laser has been driven by a major industrial process. For high average power, high peak power, nanosecond pulse duration Nd:YAG DPSS lasers, the enabling process is high speed surface engineering. This includes applications such as thin film patterning and selective coating removal in markets such as the flat panel displays (FPD), solar and automotive industries. Applications such as these tend to require working spots that have uniform intensity distribution using specific shapes and dimensions, so a range of innovative beam delivery systems have been developed that convert the gaussian beam shape produced by the laser into a range of rectangular and/or shaped spots, as required by demands of each project. In this paper the authors will discuss the key parameters of this type of laser and examine why they are important for high speed surface engineering projects, and how they affect the underlying laser-material interaction and the removal mechanism. Several case studies will be considered in the FPD and solar markets, exploring the close link between the application, the key laser characteristics and the beam delivery system that link these together.

  9. Spectroscopic measurement of temperatures in pulsed TIG welding arcs

    NASA Astrophysics Data System (ADS)

    Ma, Shuiliang; Gao, Hongming; Zheng, Senmu; Wu, Lin

    2011-10-01

    Time resolved plasma temperatures in a pulsed tungsten-inert-gas (TIG) welding arc have been measured using optical emission spectroscopy. The peak and base pulse-averaged plasma temperatures both decrease with time after the arc ignition, and the plasma temperature decreases during the peak pulse period and increases during the base pulse period when the arc reaches the steady state. The decrease in the plasma temperature is associated with the increase in the cathode surface temperature and the decrease in the arc voltage and vice versa. The importance of the cathode surface temperature on the arc properties has been discussed.

  10. Measurement of the Optical Coherence of a Femtosecond Pulsed Laser by Shearing Interferometry with a Double-Frequency Grating

    NASA Astrophysics Data System (ADS)

    Ming, Hai; Qian, Jiang-yuan; Xie, Jian-ping; A, B. Fedotov; X, Xiao; M, M. T. Loy

    1998-01-01

    Shearing interferometry of an ion-etched holographic double-frequency grating is used to measure the optical coherence of femtosecond pulsed lasers. The experimental results show that the optical coherence of the femtosecond light beam is not only related to the spectral width and size of the light source but is also related to the pulse duration and mode-locked laser state. The results of theoretical analysis and numerical calculation are also given. Application of this research is also discussed.

  11. Electro-optic measurement of terahertz pulse energy distribution

    NASA Astrophysics Data System (ADS)

    Sun, J. H.; Gallacher, J. G.; Brussaard, G. J. H.; Lemos, N.; Issac, R.; Huang, Z. X.; Dias, J. M.; Jaroszynski, D. A.

    2009-11-01

    An accurate and direct measurement of the energy distribution of a low repetition rate terahertz electromagnetic pulse is challenging because of the lack of sensitive detectors in this spectral range. In this paper, we show how the total energy and energy density distribution of a terahertz electromagnetic pulse can be determined by directly measuring the absolute electric field amplitude and beam energy density distribution using electro-optic detection. This method has potential use as a routine method of measuring the energy density of terahertz pulses that could be applied to evaluating future high power terahertz sources, terahertz imaging, and spatially and temporarily resolved pump-probe experiments.

  12. Breakdown of a gas on a metallic surface by CO2 laser pulses of 10-1000 microsec duration

    NASA Astrophysics Data System (ADS)

    Kovalev, A. S.; Popov, A. M.; Rakhimov, A. T.; Seleznev, B. V.; Khropov, S. M.

    1985-04-01

    The formation of a plasma on the surface of a metal target under direct exposure to a CO2 laser is studied theoretically. A classical kinetic equation is derived to calculate the critical radiation intensity of several metallic target materials. Experimental measurements of the time to the development of optical breakdown are found to agree with the theoretical results. It is shown that the breakdown discontinuity of the target shifts to the front of the laser pulse if the temperature of the radiation exceeds the critical temperature. No relation was found between the breakdown discontinuity and the boiling point of the metallic target materials.

  13. Direct measurement of transient pulses induced by laser and heavy ion irradiation in deca-nanometer devices.

    SciTech Connect

    Knudson, A. R.; Torres, A.; McMorrow, D.; Ferlet-Cavrois, Veronique; Schwank, James Ralph; Paillet, Philippe; Melinger, J. S.; Tosti, L.; Jahan, C.; Barna, Gabriel; Faynot, O.; Shaneyfelt, Marty Ray; Campbell, A. B.; Gaillardin, M.; Hirose, K.; Vizkelethy, Gyorgy

    2005-07-01

    This paper investigates the transient response of 50-nm gate length fully and partially depleted SOI and bulk devices to pulsed laser and heavy ion microbeam irradiations. The measured transient signals on 50-nm fully depleted devices are very short, and the collected charge is small compared to older 0.25-{micro}m generation SOI and bulk devices. We analyze in detail the influence of the SOI architecture (fully or partially depleted) on the pulse duration and the amount of bipolar amplification. For bulk devices, the doping engineering is shown to have large effects on the duration of the transient signals and on the charge collection efficiency.

  14. Perceptual, durational and tongue displacement measures following articulation therapy for rhotic sound errors.

    PubMed

    Bressmann, Tim; Harper, Susan; Zhylich, Irina; Kulkarni, Gajanan V

    2016-01-01

    Outcomes of articulation therapy for rhotic errors are usually assessed perceptually. However, our understanding of associated changes of tongue movement is limited. This study described perceptual, durational and tongue displacement changes over 10 sessions of articulation therapy for /ɹ/ in six children. Four of the participants also received ultrasound biofeedback of their tongue shape. Speech and tongue movement were recorded pre-therapy, after 5 sessions, in the final session and at a one month follow-up. Perceptually, listeners perceived improvement and classified more productions as /ɹ/ in the final and follow-up assessments. The durations of VɹV syllables at the midway point of the therapy were longer. Cumulative tongue displacement increased in the final session. The average standard deviation was significantly higher in the middle and final assessments. The duration and tongue displacement measures illustrated how articulation therapy affected tongue movement and may be useful for outcomes research about articulation therapy. PMID:26979162

  15. The influence of laser pulse duration and energy on ICP-MS signal intensity, elemental fractionation, and particle size distribution in NIR fs-LA-ICP-MS

    PubMed Central

    Diwakar, Prasoon K.; Harilal, Sivanandan S.; LaHaye, Nicole L.; Hassanein, Ahmed; Kulkarni, Pramod

    2015-01-01

    Laser parameters, typically wavelength, pulse width, irradiance, repetition rate, and pulse energy, are critical parameters which influence the laser ablation process and thereby influence the LA-ICP-MS signal. In recent times, femtosecond laser ablation has gained popularity owing to the reduction in fractionation related issues and improved analytical performance which can provide matrix-independent sampling. The advantage offered by fs-LA is due to shorter pulse duration of the laser as compared to the phonon relaxation time and heat diffusion time. Hence the thermal effects are minimized in fs-LA. Recently, fs-LA-ICP-MS demonstrated improved analytical performance as compared to ns-LA-ICP-MS, but detailed mechanisms and processes are still not clearly understood. Improvement of fs-LA-ICP-MS over ns-LA-ICP-MS elucidates the importance of laser pulse duration and related effects on the ablation process. In this study, we have investigated the influence of laser pulse width (40 fs to 0.3 ns) and energy on LA-ICP-MS signal intensity and repeatability using a brass sample. Experiments were performed in single spot ablation mode as well as rastering ablation mode to monitor the Cu/Zn ratio. The recorded ICP-MS signal was correlated with total particle counts generated during laser ablation as well as particle size distribution. Our results show the importance of pulse width effects in the fs regime that becomes more pronounced when moving from femtosecond to picosecond and nanosecond regimes. PMID:26664120

  16. Design of a pulse-type strain gauge balance for a long-test-duration hypersonic shock tunnel

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Liu, Y.; Jiang, Z.

    2016-01-01

    When the measurement of aerodynamic forces is conducted in a hypersonic shock tunnel, the inertial forces lead to low-frequency vibrations of the model, and its motion cannot be addressed through digital filtering because a sufficient number of cycles cannot be obtained during a tunnel run. This finding implies restrictions on the model size and mass as the natural frequencies are inversely proportional to the length scale of the model. Therefore, the force measurement still has many problems, particularly for large and heavy models. Different structures of a strain gauge balance (SGB) are proposed and designed, and the measurement element is further optimized to overcome the difficulties encountered during the measurement of aerodynamic forces in a shock tunnel. The motivation for this study is to assess the structural performance of the SGB used in a long-test-duration JF12 hypersonic shock tunnel, which has more than 100 ms of test time. Force tests were conducted for a large-scale cone with a 10° semivertex angle and a length of 0.75 m in the JF12 long-test-duration shock tunnel. The finite element method was used for the analysis of the vibrational characteristics of the Model-Balance-Sting System (MBSS) to ensure a sufficient number of cycles, particularly for the axial force signal during a shock tunnel run. The higher-stiffness SGB used in the test shows good performance, wherein the frequency of the MBSS increases because of the stiff construction of the balance. The experimental results are compared with the data obtained in another wind tunnel and exhibit good agreement at M = 7 and α =5°.

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

    SciTech Connect

    Bolton, P.R.

    1987-06-01

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

  18. 1 MHz repetition rate hollow fiber pulse compression to sub-100-fs duration at 100 W average power.

    PubMed

    Rothhardt, Jan; Hädrich, Steffen; Carstens, Henning; Herrick, Nicholas; Demmler, Stefan; Limpert, Jens; Tünnermann, Andreas

    2011-12-01

    We report on nonlinear pulse compression at very high average power. A high-power fiber chirped pulse amplification system based on a novel large pitch photonic crystal fiber delivers 700 fs pulses with 200 μJ pulse energy at a 1 MHz repetition rate, resulting in 200 W of average power. Subsequent spectral broadening in a xenon-filled hollow-core fiber and pulse compression with chirped mirrors is employed for pulse shortening and peak power enhancement. For the first time, to our knowledge, more than 100 W of average power are transmitted through a noble-gas-filled hollow fiber. After pulse compression of 81 fs, 93 μJ pulses are obtained at a 1 MHz repetition rate. PMID:22139257

  19. Performance of high-convergence, layered DT implosions with extended-duration pulses at the National Ignition Facility.

    PubMed

    Smalyuk, V A; Atherton, L J; Benedetti, L R; Bionta, R; Bleuel, D; Bond, E; Bradley, D K; Caggiano, J; Callahan, D A; Casey, D T; Celliers, P M; Cerjan, C J; Clark, D; Dewald, E L; Dixit, S N; Döppner, T; Edgell, D H; Edwards, M J; Frenje, J; Gatu-Johnson, M; Glebov, V Y; Glenn, S; Glenzer, S H; Grim, G; Haan, S W; Hammel, B A; Hartouni, E P; Hatarik, R; Hatchett, S; Hicks, D G; Hsing, W W; Izumi, N; Jones, O S; Key, M H; Khan, S F; Kilkenny, J D; Kline, J L; Knauer, J; Kyrala, G A; Landen, O L; Le Pape, S; Lindl, J D; Ma, T; MacGowan, B J; Mackinnon, A J; MacPhee, A G; McNaney, J; Meezan, N B; Moody, J D; Moore, A; Moran, M; Moses, E I; Pak, A; Parham, T; Park, H-S; Patel, P K; Petrasso, R; Ralph, J E; Regan, S P; Remington, B A; Robey, H F; Ross, J S; Spears, B K; Springer, P T; Suter, L J; Tommasini, R; Town, R P; Weber, S V; Widmann, K

    2013-11-22

    Radiation-driven, low-adiabat, cryogenic DT layered plastic capsule implosions were carried out on the National Ignition Facility (NIF) to study the sensitivity of performance to peak power and drive duration. An implosion with extended drive and at reduced peak power of 350 TW achieved the highest compression with fuel areal density of ~1.3±0.1 g/cm2, representing a significant step from previously measured ~1.0 g/cm2 toward a goal of 1.5 g/cm2. Future experiments will focus on understanding and mitigating hydrodynamic instabilities and mix, and improving symmetry required to reach the threshold for thermonuclear ignition on NIF. PMID:24313493

  20. System for measuring temporal profiles of scintillation at high and different linear energy transfers by using pulsed ion beams

    SciTech Connect

    Koshimizu, Masanori Asai, Keisuke; Kurashima, Satoshi; Taguchi, Mitsumasa; Kimura, Atsushi; Iwamatsu, Kazuhiro

    2015-01-15

    We have developed a system for measuring the temporal profiles of scintillation at high linear energy transfer (LET) by using pulsed ion beams from a cyclotron. The half width at half maximum time resolution was estimated to be 1.5–2.2 ns, which we attributed mainly to the duration of the pulsed ion beam and timing jitter between the trigger signal and the arrival of the ion pulse. The temporal profiles of scintillation of BaF{sub 2} at different LETs were successfully observed. These results indicate that the proposed system is a powerful tool for analyzing the LET effects in temporal profiles of scintillation.

  1. Ultrafast saturation of electronic-resonance-enhanced coherent anti-Stokes Raman scattering and comparison for pulse durations in the nanosecond to femtosecond regime

    NASA Astrophysics Data System (ADS)

    Patnaik, Anil K.; Roy, Sukesh; Gord, James R.

    2016-02-01

    The saturation threshold of a probe pulse in an ultrafast electronic-resonance-enhanced (ERE) coherent anti-Stokes Raman spectroscopy (CARS) configuration is calculated. We demonstrate that while the underdamping condition is a sufficient condition for saturation of ERE-CARS with the long-pulse excitations, a transient gain must be achieved to saturate the ERE-CARS signal for the ultrafast probe regime. We identify that the area under the probe pulse can be used as a definitive parameter to determine the criterion for a saturation threshold for ultrafast ERE-CARS. From a simplified analytical solution and a detailed numerical calculation based on density-matrix equations, the saturation threshold of ERE-CARS is compared for a wide range of probe-pulse durations from the 10-ns to the 10-fs regime. The theory explains both qualitatively and quantitatively the saturation thresholds of resonant transitions and also gives a predictive capability for other pulse duration regimes. The presented criterion for the saturation threshold will be useful in establishing the design parameters for ultrafast ERE-CARS.

  2. Non-invasive measurement of local pulse pressure by pulse wave-based ultrasound manometry (PWUM)

    PubMed Central

    Vappou, J; Luo, J; Okajima, K; Di Tullio, M; Konofagou, E E

    2014-01-01

    The central Blood Pressure (CBP) has been established as a relevant indicator of cardiovascular disease. Despite its significance, CBP remains particularly challenging to measure in standard clinical practice. The objective of this study is to introduce Pulse Wave-based Ultrasound Manometry (PWUM) as a simple-touse, non-invasive ultrasound-based method for quantitative measurement of the central pulse pressure. Arterial wall displacements are estimated using radiofrequency (RF) ultrasound signals acquired at high frame rates and the pulse pressure waveform is estimated using both the distension waveform and the local Pulse Wave Velocity (PWV). The method was tested on the abdominal aorta of 11 healthy subjects (age 35.7± 16 y.o.). PWUM pulse pressure measurements were compared to those obtained by radial applanation tonometry using a commercial system. The average intra-subject variability of the pulse pressure amplitude was found to be equal to 4.2 mmHg, demonstrating good reproducibility of the method. Excellent correlation was found between the waveforms obtained by PWUM and those obtained by tonometry in all subjects (0.94 pulse pressure waveform at the imaged location, and may offer therefore the possibility to estimate the pulse pressure at different arterial sites. Future developments include the validation of the method against invasive estimates on patients, as well as its application to other large arteries. PMID:21904023

  3. Influence of the Duration of Thermal Action on the Errors in Determining the Thermophysical Characteristics of Ceramic Materials by a Laser Pulse Method

    NASA Astrophysics Data System (ADS)

    Kuznetsov, G. V.; Kats, M. D.

    2016-06-01

    An analysis of the errors involved in determining the thermophysical characteristics of a special-purpose ceramic material — zirconium carbide — is made. It is shown that the errors of determining the heat capacity and thermal diffusivity of the indicated material under conditions corresponding to the implementation of the laser pulse method vary nonmonotonically depending on the pulse duration. The possibility of attaining minimum values of methodical errors by appropriately selecting the thickness of a sample and of the time of its heating is shown.

  4. Measurement of ice accretion using ultrasonic pulse echo techniques

    NASA Technical Reports Server (NTRS)

    Hansman, R. John, Jr.; Kirby, Mark S.

    1987-01-01

    Many figures are given to illustrate the measurement of ice deposition using ultrasonic pulse echo techniques. The basic concept is to measure the thickness of the ice by relating the pulse echo time to the speed of sound. The measurements are made in an icing research tunnel (IRT), where echo patterns are videotaped during icing exposures under a variety of conditions. Typical echo patterns for different types of ice are illustrated. A table summarizing the icing rates measured in the IRT, along with the presence or absence of surface water is also given.

  5. A novel measurement scheme for the radial group delay of large-aperture ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Wu, Fenxiang; Xu, Yi; Li, Zhaoyang; Li, Wenkai; Lu, Jun; Wang, Cheng; Li, Yanyan; Liu, Yanqi; Lu, Xiaoming; Peng, Yujie; Wang, Ding; Leng, Yuxin; Li, Ruxin

    2016-05-01

    In femtosecond high-peak-power laser system, the radial group delay (RGD) of the pulse front introduced by conventional lens-based beam expanders can significantly decrease the achievable focal intensity, especially when it is larger than the pulse duration. In order to quantitatively analyze and compensate the RGD, a novel measurement scheme based on self-reference and second-order cross-correlation technology is proposed and applied to measure the RGD of the large-aperture ultra-short laser pulses directly. The measured result of the RGD in a 200 TW Ti:sapphire laser system is in good agreement with the theoretical calculation. To our knowledge, it is the first time to realize the direct RGD measurement of large-aperture ultra-short laser pulses.

  6. Oh Laser-Induced Fluorescence Measurements in Nanosecond Pulse Discharge Plasmas

    NASA Astrophysics Data System (ADS)

    Choi, Inchul; Adamovich, Igor V.; Lempert, Walter R.

    2010-06-01

    We present recent results of laser-induced fluorescence measurements of hydroxyl radical density in repetitively pulsed nanosecond plasmas, created using 10-20 nsec duration, high (up to 20 kV) voltage pulsers, capable of operation at repetition rates as high as 40-50 kHz. OH mole fraction as a function of time with respect to discharge creation is determined, with absolute calibration performed using a Hencken flat flame burner. This paper will focus on a series of low temperature, non-equilibrium kinetics measurements in hydrogen and hydrocarbon-air mixtures, with results compared to predictions of a recently developed plasma chemical oxidation model.

  7. Unraveling the roles of thermal annealing and off-time duration in magnetic properties of pulsed electrodeposited NiCu nanowire arrays

    NASA Astrophysics Data System (ADS)

    Haji jamali, Z.; Almasi Kashi, M.; Ramazani, A.; Montazer, A. H.

    2015-05-01

    Magnetic alloy nanowires (ANWs) have long been studied owing to both their fundamental aspects and possible applications in magnetic storage media and magnetoresistance devices. Here, we report on the roles of thermal annealing and duration of off-time between pulses (toff) in crystalline characteristics and magnetic properties of arrays of pulsed electrodeposited NiCu ANWs (35 nm in diameter and a length of 1.2 μm), embedded in porous anodic alumina template. Increasing toff enabled us to increase the Cu content thereby fabricating NiCu ANWs with different crystallinity and alloy compositions. Although major hysteresis curve measurements showed no considerable change in magnetic properties before and after annealing, the first-order reversal curve (FORC) analysis provided new insights into the roles of thermal annealing and toff. In other words, FORC diagrams indicated the presence of low and high coercive field regions in annealed Ni-rich ANWs, coinciding with the increase in toff in as-deposited ANWs. The former has a small coercivity with strong demagnetizing magnetostatic interactions from neighboring NWs and may correspond to a soft magnetic phase. The latter has a greater coercivity with weak interactions, corresponding to a hard magnetic phase. On the other hand, for as-deposited and annealed Cu-rich NiCu ANWs, a mixed phase of the soft and hard segments could be found. Furthermore, a transition from the interacting Ni-rich to non-interacting Cu-rich ANWs took place with a magnetic field applied parallel to the NW axis. Thus, these arrays of ANWs with tunable magnetic phases and interactions may have potential applications in the nanoscale devices.

  8. Comparison of sunshine duration measurements from Campbell-Stokes sunshine recorder and CSD1 sensor

    NASA Astrophysics Data System (ADS)

    Urban, Grzegorz; Zając, Ireneusz

    2016-03-01

    Paper presents comparative analysis of sunshine duration measurement results obtained using Campbell-Stokes sunshine recorder (CS) and electronic sensor (CSD1). The comparison is based on data from 2009 to 2010 collected at seven weather stations (Leszno, Wrocław-Strachowice, Legnica, Opole, Zielona Góra, Jelenia Góra, Kłodzko) operated by the Institute of Meteorology and Water Management—National Research Institute (IMWM-NRI) in south-western Poland. Results obtained in Opole and Legnica stations are erroneous. In case of other stations, the relationship between daily total sunshine duration as measured by CS and CSD1 was strong. Coefficients of determination were 0.96-0.97. Mean differences in daily totals of sunshine duration were ±0.3 h. Differences of mean monthly and annual totals were both positive and negative with no pattern of occurrences. Implementation of permanent corrections is not possible. The highest consistency between both measurement devices was found during winter months.

  9. Towards higher stability of resonant absorption measurements in pulsed plasmas

    NASA Astrophysics Data System (ADS)

    Britun, Nikolay; Michiels, Matthieu; Snyders, Rony

    2015-12-01

    Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called "dynamic source triggering," between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source.

  10. Towards higher stability of resonant absorption measurements in pulsed plasmas

    SciTech Connect

    Britun, Nikolay; Michiels, Matthieu; Snyders, Rony

    2015-12-15

    Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called “dynamic source triggering,” between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source.

  11. Towards higher stability of resonant absorption measurements in pulsed plasmas.

    PubMed

    Britun, Nikolay; Michiels, Matthieu; Snyders, Rony

    2015-12-01

    Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called "dynamic source triggering," between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source. PMID:26724013

  12. Effects of presentation duration on measures of complexity in affective environmental scenes and representational paintings.

    PubMed

    Marin, Manuela M; Leder, Helmut

    2016-01-01

    Complexity constitutes an integral part of humans' environment and is inherent to information processing. However, little is known about the dynamics of visual complexity perception of affective environmental scenes (IAPS pictures) and artworks, such as affective representational paintings. In three experiments, we studied the time course of visual complexity perception by varying presentation duration and comparing subjective ratings with objective measures of complexity. In Experiment 1, 60 females rated 96 IAPS pictures, presented either for 1, 5, or 25s, for familiarity, complexity, pleasantness and arousal. In Experiment 2, another 60 females rated 96 representational paintings. Mean ratings of complexity and pleasantness changed according to presentation duration in a similar vein in both experiments, suggesting an inverted U-shape. No common pattern of results was observed for arousal and familiarity ratings across the two picture sets. The correlations between subjective and objective measures of complexity increased with longer exposure durations for IAPS pictures, but results were more ambiguous for paintings. Experiment 3 explored the time course of the multidimensionality of visual complexity perception. Another 109 females rated the number of objects, their disorganization and the differentiation between a figure-ground vs. complex scene composition of pictures presented for 1 and 5s. The multidimensionality of visual complexity only clearly emerged in the 5-s condition. In both picture sets, the strength of the correlations with objective measures depended on the type of subdimension of complexity and was less affected by presentation duration than correlations with general complexity in Experiments 1 and 2. These results have clear implications for perceptual and cognitive theories, especially for those of esthetic experiences, in which the dynamical changes of complexity perception need to be integrated. PMID:26595281

  13. Laser-spectroscopic electric field measurements in a ns-pulsed microplasma in nitrogen

    NASA Astrophysics Data System (ADS)

    Boehm, Patrick; Luggenhoelscher, Dirk; Czarnetzki, Uwe; 1123 Research Group Collaboration

    2013-09-01

    In this work for the first time ns-pulsed discharges in nitrogen at near atmospheric pressures are investigated by laser-spectroscopic electric field measurements, ultra-fast optical emission spectroscopy, current and voltage measurements. The discharge is operated with kV-pulses of about 150 ns duration between two parallel plate electrodes with a 1.2 mm gap. The laser technique for electric field measurement is based on a four-wave mixing process similar to Coherent anti-Stokes Raman Scattering (CARS). Here the static electric field acts effectively as the third wave with a zero frequency. The frequency of the generated anti-Stokes wave is in the IR regime and the amplitude is proportional to the electric field strength. By measuring the intensity of the IR- and anti-Stokes-signal it is now possible to determine the static electric field. Due to the short pulse-length of the lasers a temporal resolution in the ns range and a typical sensitivity of 50 - 100 V/mm in pure nitrogen is achieved (p > 50 mbar). Field-measurements are accompanied by emission measurements using a streak-camera with sub-ns resolutions. Further, current and voltage measurements combined with the electric field measurements allow determination of the plasma density. Funding by DFG through FOR 1123.

  14. Determination of Spring Onset and Growing Season Duration using Satellite Measurements

    NASA Technical Reports Server (NTRS)

    Min, Q.; Lin, Bing

    2006-01-01

    An integrated approach to retrieve microwave emissivity difference vegetation index (EDVI) over land regions has been developed from combined multi-platform/multi-sensor satellite measurements, including SSM/I measurements. A possible relationship of the remotely sensed EDVI and the leaf physiology of canopy is exploited at the Harvard Forest site for two growing seasons. This study finds that the EDVI is sensitive to leaf development through vegetation water content of the crown layer of the forest canopy, and has demonstrated that the spring onset and growing season duration can be determined accurately from the time series of satellite estimated EDVI within uncertainties about 3 and 7 days for spring onsets and growing season duration, respectively, compared to in-situ observations. The leaf growing stage may also be quantitatively monitored by a normalized EDVI. Since EDVI retrievals from satellite are generally possible during both daytime and nighttime under non-rain conditions, the EDVI technique studied here may provide higher temporal resolution observations for monitoring the onset of spring and the duration of growing season compared to currently operational satellite methods.

  15. Fade-durations derived from land-mobile-satellite measurements in Australia

    NASA Technical Reports Server (NTRS)

    Hase, Yoshihiro; Vogel, Wolfhard J.; Goldhirsh, Julius

    1991-01-01

    Transmissions from the Japanese ETS-V geostationary satellite were measured at L band (1.5 GHz) in a vehicle driving on roads of southeastern Australia. The measurements were part of a program designed to characterize propagation effects due to roadside trees and terrain for mobile satellite service. It is shown that the cumulative distributions of fade and nonfade durations follow a lognormal and power law, respectively. At 1 percent probability, fades last 2-8 m, and nonfades 10-100 m, depending on the degree of shadowing. Phase fluctuations are generally small, allowing the channel characteristics to be estimated from levels only.

  16. Balances for the measurement of multiple components of force in flows of a millisecond duration

    NASA Technical Reports Server (NTRS)

    Mee, D. J.; Daniel, W. J.; Tuttle, S. L.; Simmons, J. M.

    1995-01-01

    This paper reports a new balance for the measurement of three components of force - lift, drag and pitching moment - in impulsively starting flows which have a duration of about one millisecond. The basics of the design of the balance are presented and results of tests on a 15 deg semi-angle cone set at incidence in the T4 shock tunnel are compared with predictions. These results indicate that the prototype balance performs well for a 1.9 kg, 220 mm long model. Also presented are results from initial bench tests of another application of the deconvolution force balance to the measurement of thrust produced by a 2D scramjet nozzle.

  17. Low cost laser system generating 26-fs pulse duration, 30-kW peak power, and tunability from 800 to 1200 nm for multiphoton microscopy

    NASA Astrophysics Data System (ADS)

    Resan, Bojan; Brunner, Felix; Rohrbacher, Andreas; Ammann, Hubert; Weingarten, Kurt J.

    2012-03-01

    We demonstrate a novel low-cost, low-noise, tunable, high-peak-power, ultrafast laser system based on a SESAMmodelocked, solid-state Yb tungstate laser plus spectral broadening via a microstructured fiber followed by pulse compression. The spectral selection, tuning, and pulse compression are performed with a simple prism compressor. The spectral broadening and fiber parameters are chosen to insure low-noise and short pulse operation of the tunable output. The long-term stable output pulses are tunable from 800 to 1200 nm, with a peak power up to 30 kW and pulse duration down to 26 fs. We demonstrate the generation of an output beam with 30 fs pulsewidth and multiple colors in infrared. In particular, we compressed selected spectral slices centered at 960 and 1100 nm suitable for imaging with green fluorescent protein and red dyes. Such a multicolor, 30 fs laser is ideally suited for simultaneous multispectral multiphoton imaging. This system is attractive for variety of applications including multiphoton (TPE, SHG, THG, CARS) and multimodal microscopy, nanosurgery, and optical coherence tomography (OCT). Such system is simpler, lower-cost, and much easier to use (fully turn-key) compared to a currently available solutions for near-infrared ultrashort pulses, typically a Ti:sapphire laser-pumped OPO.

  18. Evaluation of an innovative sensor for measuring global and diffuse irradiance, and sunshine duration

    NASA Astrophysics Data System (ADS)

    Muneer, Tariq; Zhang, Xiaodong; Wood, John

    2002-03-01

    Delta-T Device Limited of Cambridge, UK have developed an integrated device which enables simultaneous measurement of horizontal global and diffuse irradiance as well as sunshine status at any given instance in time. To evaluate the performance of this new device, horizontal global and diffuse irradiance data were simultaneously collected from Delta-T device and Napier University's CIE First Class daylight monitoring station. To enable a cross check a Kipp & Zonen CM11 global irradiance sensor has also been installed in Currie, south-west Edinburgh. Sunshine duration data have been recorded at the Royal Botanical Garden, Edinburgh using their Campbell-Stokes recorder. Hourly data sets were analysed and plotted within the Microsoft Excel environment. Using the common statistical measures, Root Mean Square Difference (RMSD) and Mean Bias Difference (MBD) the accuracy of measurements of Delta-T sensor's horizontal global and diffuse irradiance, and sunshine duration were investigated. The results show a good performance on the part of Delta-T device for the measurement of global and diffuse irradiance. The sunshine measurements were found to have a lack of consistency and accuracy. It is argued herein that the distance between the respective sensors and the poor accuracy of Campbell-Stokes recorder may be contributing factors to this phenomenon.

  19. Measuring ultrashort pulses using frequency-resolved optical gating

    SciTech Connect

    Trebino, R.

    1993-12-01

    The purpose of this program is the development of techniques for the measurement of ultrafast events important in gas-phase combustion chemistry. Specifically, goals of this program include the development of fundamental concepts and spectroscopic techniques that will augment the information currently available with ultrafast laser techniques. Of equal importance is the development of technology for ultrafast spectroscopy. For example, methods for the production and measurement of ultrashort pulses at wavelengths important for these studies is an important goal. Because the specific vibrational motion excited in a molecule depends sensitively on the intensity, I(t), and the phase, {psi}(t), of the ultrashort pulse used to excite the motion, it is critical to measure both of these quantities for an individual pulse. Unfortunately, this has remained an unsolved problem for many years. Fortunately, this year, the authors present a technique that achieves this goal.

  20. Measurement of dynamic magnetization induced by a pulsed field: Proposal for a new rock magnetism method

    NASA Astrophysics Data System (ADS)

    Kodama, Kazuto

    2015-02-01

    This study proposes a new method for measuring transient magnetization of natural samples induced by a pulsed field with duration of 11 ms using a pulse magnetizer. An experimental system was constructed, consisting of a pair of differential sensing coils connected with a high-speed digital oscilloscope for data acquisition. The data were transferred to a computer to obtain an initial magnetization curve and a descending branch of a hysteresis loop in a rapidly changing positive field. This system was tested with synthetic samples (permalloy ribbon, aluminum plate, and nickel powder) as well as two volcanic rock samples. Results from the synthetic samples showed considerable differences from those measured by a quasi-static method using a vibrating sample magnetometer (VSM). These differences were principally due to the time-dependent magnetic properties or to electromagnetic effects, such as magnetic viscosity, eddy current loss, or magnetic relaxation. Results from the natural samples showed that the transient magnetization-field curves were largely comparable to the corresponding portions of the hysteresis loops. However, the relative magnetization (scaled to the saturation magnetization) at the end of a pulse was greater than that measured by a VSM. This discrepancy, together with the occurrence of rapid exponential decay after a pulse, indicates magnetic relaxations that could be interpreted in terms of domain wall displacement. These results suggest that with further developments, the proposed technique can become a useful tool for characterizing magnetic particles contained in a variety of natural materials.

  1. A focused air-pulse system for optical-coherence-tomography-based measurements of tissue elasticity

    NASA Astrophysics Data System (ADS)

    Wang, Shang; Larin, K. V.; Li, Jiasong; Vantipalli, S.; Manapuram, R. K.; Aglyamov, S.; Emelianov, S.; Twa, M. D.

    2013-07-01

    Accurate non-invasive assessment of tissue elasticity in vivo is required for early diagnostics of many tissue abnormalities. We have developed a focused air-pulse system that produces a low-pressure and short-duration air stream, which can be used to excite transient surface waves (SWs) in soft tissues. System characteristics were studied using a high-resolution analog pressure transducer to describe the excitation pressure. Results indicate that the excitation pressure provided by the air-pulse system can be easily controlled by the air source pressure, the angle of delivery, and the distance between the tissue surface and the port of the air-pulse system. Furthermore, we integrated this focused air-pulse system with phase-sensitive optical coherence tomography (PhS-OCT) to make non-contact measurements of tissue elasticity. The PhS-OCT system is used to assess the group velocity of SW propagation, which can be used to determine Young’s modulus. Pilot experiments were performed on gelatin phantoms with different concentrations (10%, 12% and 14% w/w). The results demonstrate the feasibility of using this focused air-pulse system combined with PhS-OCT to estimate tissue elasticity. This easily controlled non-contact technique is potentially useful to study the biomechanical properties of ocular and other tissues in vivo.

  2. On the use of spot measurements for graphical flow duration curves determination

    NASA Astrophysics Data System (ADS)

    Rianna, Maura; Elena, Ridolfi; Russo, Fabio; Napolitano, Francesco

    2015-04-01

    Flow duration curves (FDCs) determination represents the key to solve issues related to water resources engineering such as water quality management, hydropower systems design, water use planning, flood management and river and reservoirs regime estimation. FDCs graphically depict the amount of water resource corresponding to a specific river cross-section. For instance, in the hydroelectric scheme framework, FDCs permit to design a system that could cope with extreme flows, operate efficiently in the medium range of flows and operate at a low power output in the case of low flows. FDCs are easily determined in river cross-sections provided with hydrological gauging stations. However, in ungauged basins flow duration curves evaluation remains a problem to solve, especially in small basins where calibration data are sparse and refer to larger catchments scales. This work investigates a direct method to estimate FDCs using spot measures. Specifically, a graphical regionalization approach based on the flood index method of FDCs is proposed. The approach combines a regional dimensionless flow duration curve with a direct method to estimate the flood index. This is based on the evaluation of the mean annual flow at a specific site through instantaneous flow measurements. The optimal number of instantaneous measures necessary to minimize the error between observed and simulated curves is found. A jack knife procedure is applied to simulate the ungauged basins situation. The method gives indications about the optimal lag frequency and measurement year period. To test the methodology, analysis are carried out in the Liri-Garigliano basin, located in Central Italy.

  3. Measuring enzyme binding using shaped ultrafast laser pulses

    NASA Astrophysics Data System (ADS)

    Pearson, B. J.; Tseng, C.-H.; Weinacht, T. C.

    2013-03-01

    We use multiphoton quantum-control spectroscopy to discriminate between enzyme-bound and unbound NADH (reduced nicotinamide adenine dinucleotide) molecules in solution. Shaped ultrafast laser pulses are used to illuminate both forms of NADH, and the ratio of the fluorescence from the bound and unbound molecules for different pulse shapes allows us to measure binding without spectrally resolving the emitted fluorescence or relying on the absolute fluorescence yield. This permits determination of enzyme binding in situations where spectrally resolved measurements and absolute fluorescence yields are difficult to obtain, and makes the approach ideal for multiphoton microscopy with molecular discrimination.

  4. Rise Time Measurement for Ultrafast X-Ray Pulses

    DOEpatents

    Celliers, Peter M.; Weber, Franz A.; Moon, Stephen J.

    2005-04-05

    A pump-probe scheme measures the rise time of ultrafast x-ray pulses. Conventional high speed x-ray diagnostics (x-ray streak cameras, PIN diodes, diamond PCD devices) do not provide sufficient time resolution to resolve rise times of x-ray pulses on the order of 50 fs or less as they are being produced by modern fast x-ray sources. Here, we are describing a pump-probe technique that can be employed to measure events where detector resolution is insufficient to resolve the event. The scheme utilizes a diamond plate as an x-ray transducer and a p-polarized probe beam.

  5. Rise time measurement for ultrafast X-ray pulses

    DOEpatents

    Celliers, Peter M.; Weber, Franz A.; Moon, Stephen J.

    2005-04-05

    A pump-probe scheme measures the rise time of ultrafast x-ray pulses. Conventional high speed x-ray diagnostics (x-ray streak cameras, PIN diodes, diamond PCD devices) do not provide sufficient time resolution to resolve rise times of x-ray pulses on the order of 50 fs or less as they are being produced by modern fast x-ray sources. Here, we are describing a pump-probe technique that can be employed to measure events where detector resolution is insufficient to resolve the event. The scheme utilizes a diamond plate as an x-ray transducer and a p-polarized probe beam.

  6. Plasma absorption evidence via chirped pulse spectral transmission measurements

    SciTech Connect

    Jedrkiewicz, Ottavia; Minardi, Stefano; Couairon, Arnaud; Jukna, Vytautas; Selva, Marco; Di Trapani, Paolo

    2015-06-08

    This work aims at highlighting the plasma generation dynamics and absorption when a Bessel beam propagates in glass. We developed a simple diagnostics allowing us to retrieve clear indications of the formation of the plasma in the material, thanks to transmission measurements in the angular and wavelength domains. This technique featured by the use of a single chirped pulse having the role of pump and probe simultaneously leads to results showing the plasma nonlinear absorption effect on the trailing part of the pulse, thanks to the spectral-temporal correspondence in the measured signal, which is also confirmed by numerical simulations.

  7. A compact streak camera for 150 fs time resolved measurement of bright pulses in ultrafast electron diffraction.

    PubMed

    Kassier, G H; Haupt, K; Erasmus, N; Rohwer, E G; von Bergmann, H M; Schwoerer, H; Coelho, S M M; Auret, F D

    2010-10-01

    We have developed a compact streak camera suitable for measuring the duration of highly charged subrelativistic femtosecond electron bunches with an energy bandwidth in the order of 0.1%, as frequently used in ultrafast electron diffraction (UED) experiments for the investigation of ultrafast structural dynamics. The device operates in accumulation mode with 50 fs shot-to-shot timing jitter, and at a 30 keV electron energy, the full width at half maximum temporal resolution is 150 fs. Measured durations of pulses from our UED gun agree well with the predictions from the detailed charged particle trajectory simulations. PMID:21034115

  8. Pulse Analysis Spectroradiometer System for Measuring the Spectral Distribution of Flash Solar Simulators: Preprint

    SciTech Connect

    Andreas, A. M.; Myers, D. R.

    2008-07-01

    Flashing artificial light sources are used extensively in photovoltaic module performance testing and plant production lines. There are several means of attempting to measure the spectral distribution of a flash of light; however, many of these approaches generally capture the entire pulse energy. We report here on the design and performance of a system to capture the waveform of flash at individual wavelengths of light. Any period within the flash duration can be selected, over which to integrate the flux intensity at each wavelength. The resulting spectral distribution is compared with the reference spectrum, resulting in a solar simulator classification.

  9. Pulse-to-pulse jitter measurement by photon correlation in high-β lasers

    SciTech Connect

    Lebreton, Armand; Abram, Izo; Belabas, Nadia; Sagnes, Isabelle; Robert-Philip, Isabelle Beveratos, Alexios; Braive, Rémy; Marsili, Francesco; Verma, Varun B.; Nam, Sae Woo; Gerrits, Thomas; Stevens, Martin J.

    2015-01-19

    The turn-on delay jitter in pulsed lasers in which a large fraction (β) of spontaneous emission is channeled into the lasing mode is measured by use of a photon correlation technique. This jitter is found to significantly increase with β, reaching values of the order of the pulse width at threshold. This is due to the increase in the relative value of the discretization noise when the number of photons at threshold becomes small, as is the case in high-β lasers.

  10. Numerical simulations of ultrasimple ultrashortlaser-pulse measurement.

    PubMed

    Liu, Xuan; Trebino, Rick; Smith, Arlee V

    2007-04-16

    We numerically simulate the performance of the ultrasimple frequency-resolved-optical-gating (FROG) technique, GRENOUILLE, for measuring ultrashort laser pulses. While simple in practice, GRENOUILLE has many theoretical subtleties because it involves the second-harmonic generation of relatively tightly focused and broadband pulses. In addition, these processes occur in a thick crystal, in which the phase-matching bandwidth is deliberately made narrow compared to the pulse bandwidth. In these simulations, we include all sum-frequency-generation processes, both collinear and noncollinear. We also include dispersion using the Sellmeier equation for the crystal BBO. Working in the frequency domain, we compute the GRENOUILLE trace for practical-and impractical- examples and show that accurate measurements are easily obtained for properly designed devices. PMID:19532705

  11. Experimental validation of a high voltage pulse measurement method.

    SciTech Connect

    Cular, Stefan; Patel, Nishant Bhupendra; Branch, Darren W.

    2013-09-01

    This report describes X-cut lithium niobate's (LiNbO3) utilization for voltage sensing by monitoring the acoustic wave propagation changes through LiNbO3 resulting from applied voltage. Direct current (DC), alternating current (AC) and pulsed voltage signals were applied to the crystal. Voltage induced shift in acoustic wave propagation time scaled quadratically for DC and AC voltages and linearly for pulsed voltages. The measured values ranged from 10 - 273 ps and 189 ps - 2 ns for DC and non-DC voltages, respectively. Data suggests LiNbO3 has a frequency sensitive response to voltage. If voltage source error is eliminated through physical modeling from the uncertainty budget, the sensor's U95 estimated combined uncertainty could decrease to ~0.025% for DC, AC, and pulsed voltage measurements.

  12. Long Duration Exposure Facility (LDEF) attitude measurements of the Interplanetary Dust Experiment

    NASA Technical Reports Server (NTRS)

    Kassel, Philip C., Jr.; Motley, William R., III; Singer, S. Fred; Mulholland, J. Derral; Oliver, John P.; Weinberg, Jerry L.; Cooke, William J.; Wortman, Jim J.

    1993-01-01

    Analysis of the data from the Long Duration Exposure Facility (LDEF) Interplanetary Dust Experiment (IDE) sun sensors has allowed a confirmation of the attitude of LDEF during its first year in orbit. Eight observations of the yaw angle at specific times were made and are tabulated in this paper. These values range from 4.3 to 12.4 deg with maximum uncertainty of plus or minus 2.0 deg and an average of 7.9 deg. No specific measurements of pitch or roll were made but the data indicates that LDEF had an average pitch down attitude of less than 0.7 deg.

  13. ONLINE SAG MILL PULSE MEASUREMENT AND OPTIMIZATION

    SciTech Connect

    Raj Rajamani; Jose Delgadillo; Vishal Duriseti

    2006-06-24

    The grinding efficiency of semi autogenous milling or ball milling depends on the tumbling motion of the total charge within the mill. Utilization of this tumbling motion for efficient breakage of particles depends on the conditions inside the mill. However, any kind of monitoring device to measure the conditions inside the mill shell during operation is virtually impossible due to the severe environment presented by the tumbling charge. An instrumented grinding ball, which is capable of surviving a few hours and transmitting the impacts it experiences, is proposed here. The spectrum of impacts collected over 100 revolutions of the mills presents the signature of the grinding environment inside mill. This signature could be effectively used to optimize the milling performance by investigating this signature's relation to mill product size, mill throughput, make-up ball size, mill speed, liner profile and ball addition rates. At the same time, it can also be used to design balls and liner systems that can survive longer in the mill. The technological advances made in electronics and communication makes this leap in instrumentation certainly viable. Hence, the instrumented grinding ball offers the ability to qualitatively observe and optimize the milling environment.

  14. Human Pulse Wave Measurement by MEMS Electret Condenser Microphone

    NASA Astrophysics Data System (ADS)

    Nomura, Shusaku; Hanasaka, Yasushi; Ishiguro, Tadashi; Ogawa, Hiroshi

    A micro Electret Condenser Microphone (ECM) fabricated by Micro Electro Mechanical System (MEMS) technology was employed as a novel apparatus for human pulse wave measurement. Since ECM frequency response characteristic, i.e. sensitivity, logically maintains a constant level at lower than the resonance frequency (stiffness control), the slightest pressure difference at around 1.0Hz generated by human pulse wave is expected to detect by MEMS-ECM. As a result of the verification of frequency response of MEMS-ECM, it was found that -20dB/dec of reduction in the sensitivity around 1.0Hz was engendered by a high input-impedance amplifier, i.e. the field effect transistor (FET), mounted near MEMS chip for amplifying tiny ECM signal. Therefore, MEMS-ECM is assumed to be equivalent with a differentiation circuit at around human pulse frequency. Introducing compensation circuit, human pulse wave was successfully obtained. In addition, the radial and ulnar artery tracing, and pulse wave velocity measurement at forearm were demonstrated; as illustrating a possible application of this micro device.

  15. Measuring the temporal structure of few-femtosecond free-electron laser X-ray pulses directly in the time domain

    NASA Astrophysics Data System (ADS)

    Helml, W.; Maier, A. R.; Schweinberger, W.; Grguraš, I.; Radcliffe, P.; Doumy, G.; Roedig, C.; Gagnon, J.; Messerschmidt, M.; Schorb, S.; Bostedt, C.; Grüner, F.; Dimauro, L. F.; Cubaynes, D.; Bozek, J. D.; Tschentscher, Th.; Costello, J. T.; Meyer, M.; Coffee, R.; Düsterer, S.; Cavalieri, A. L.; Kienberger, R.

    2014-12-01

    Short-wavelength free-electron lasers are now well established as essential and unrivalled sources of ultrabright coherent X-ray radiation. One of the key characteristics of these intense X-ray pulses is their expected few-femtosecond duration. No measurement has succeeded so far in directly determining the temporal structure or even the duration of these ultrashort pulses in the few-femtosecond range. Here, by deploying the so-called streaking spectroscopy technique at the Linac Coherent Light Source, we demonstrate a non-invasive scheme for temporal characterization of X-ray pulses with sub-femtosecond resolution. This method is independent of photon energy, decoupled from machine parameters, and provides an upper bound on the X-ray pulse duration. We measured the duration of the shortest X-ray pulses currently available to be on average no longer than 4.4 fs. Analysing the pulse substructure indicates a small percentage of the free-electron laser pulses consisting of individual high-intensity spikes to be on the order of hundreds of attoseconds.

  16. Measurements of semi-volatile organic compounds in settled dust: influence of storage temperature and duration.

    PubMed

    Blanchard, O; Mercier, F; Ramalho, O; Mandin, C; Le Bot, B; Glorennec, P

    2014-04-01

    Indoor dust samples cannot always be analyzed immediately after collection. However, little information is currently available on how storage conditions may affect measurements. This study was designed to determine how sample storage conditions may affect the concentration of semi-volatile organic compounds (SVOCs) in the dust. A composite dust was prepared using a Standard Reference Material (SRM 2585) with real indoor dust samples. The composite dust was stored in various types of packaging, at different temperatures (-18°C, 5°C, 20°C, and 35°C), and in different light conditions. The concentration of SVOCs was measured after various storage durations. No effect on SVOC concentrations was observed for the composite dust stored in an amber glass vial at -18°C for 36 months. At 5°C, 20°C, and 35°C, losses occurred for the more volatile compounds. The experimental storage conditions clearly showed that temperature and duration affected the concentrations of SVOCs in the composite dust. The type of packaging material (polyethylene zip bag or polyethylene garbage bag) did not seem to have a systematic effect on the preservation of SVOCs in the composite dust. Maximum storage duration times are proposed for each compound at various temperatures. For most compounds, samples can be stored for 2 months at 20°C. For samples that cannot be analyzed immediately, we recommend to store them in the dark at -18°C to ensure a good recovery of all tested compounds. PMID:24033516

  17. Measurements of Intense Femtosecond Laser Pulse Propagation in Air

    NASA Astrophysics Data System (ADS)

    Ting, Antonio

    2004-11-01

    Intense femtosecond pulses generated from chirped pulse amplification (CPA) lasers can deliver laser powers many times above the critical power for self-focusing in air. Catastrophic collapse of the laser pulse is usually prevented by the defocusing of the plasma column formed when the laser intensity gets above the threshold for multiphoton ionization. The resultant laser/plasma filament can extend many meters as the laser pulse propagates in the atmosphere. We have carried out a series of experiments both for understanding the formation mechanisms of the filaments and the nonlinear effects such as white light and harmonics generation associated with them. Many applications of these filaments such as remote atmospheric breakdown, laser induced electrical discharge and femtosecond laser material interactions require direct measurements of their characteristics. Direct measurements of these filaments had been difficult because the high laser intensity ( ˜10^13 W/cm^2) can damage practically any optical diagnostics. A novel technique was invented to obtain the first absolute measurements of laser energy, transverse profile, fluence and spectral content of the filaments. We are investigating a ``remote atmospheric breakdown'' concept of remotely sensing chemical and biological compounds. A short intense laser pulse can be generated at a remote position by using the group velocity dispersion (GVD) of the air to compress an initially long, frequency negatively chirped laser pulse to generate the air breakdown and filaments. We have observed that nonlinear contributions to the laser spectrum through self-phase modulation can lead to modification of the linear GVD compression. We have also observed the generation of ultraviolet (UV) radiations from these filaments in air and the induced fluorescence by the UV radiation of a surrogate biological agent. These and other results such as laser induced electrical discharges will be presented.

  18. Effect of level, duration, and inter-pulse interval of 1-2 kHz sonar signal exposures on harbor porpoise hearing.

    PubMed

    Kastelein, Ronald A; Hoek, Lean; Gransier, Robin; Rambags, Martijn; Claeys, Naomi

    2014-07-01

    Safety criteria for underwater low-frequency active sonar sounds produced during naval exercises are needed to protect harbor porpoise hearing. As a first step toward defining criteria, a porpoise was exposed to sequences consisting of series of 1-s, 1-2 kHz sonar down-sweeps without harmonics (as fatiguing noise) at various combinations of average received sound pressure levels (SPLs; 144-179 dB re 1 μPa), exposure durations (1.9-240 min), and duty cycles (5%-100%). Hearing thresholds were determined for a narrow-band frequency-swept sine wave centered at 1.5 kHz before exposure to the fatiguing noise, and at 1-4, 4-8, 8-12, 48, 96, 144, and 1400 min after exposure, to quantify temporary threshold shifts (TTSs) and recovery of hearing. Results show that the inter-pulse interval of the fatiguing noise is an important parameter in determining the magnitude of noise-induced TTS. For the reported range of exposure combinations (duration and SPL), the energy of the exposure (i.e., cumulative sound exposure level; SELcum) can be used to predict the induced TTS, if the inter-pulse interval is known. Exposures with equal SELcum but with different inter-pulse intervals do not result in the same induced TTS. PMID:24993225

  19. Trepanning drilling of stainless steel using a high-power Ytterbium-doped fiber ultrafast laser: influence of pulse duration on hole geometry and processing quality

    NASA Astrophysics Data System (ADS)

    Lopez, John; Dijoux, Mathieu; Devillard, Raphael; Faucon, Marc; Kling, Rainer

    2014-03-01

    Percussion drilling is a well-established technique for several applicative markets such as for aircraft and watch industries. Lamp pumped solid state lasers and more recently fiber lasers, operating in millisecond or nanosecond regimes, are classically used for these applications. However, due to their long pulse duration, these technologies are not suitable for emerging applicative market such as fuel injectors for automotive industry. Only the ultrashort laser technology, combined with special drilling optics like trepanning head, has the potential to fulfill the needs for this new market in terms of processing quality, custom-shape capabilities and short drilling time. Although numerous papers dealing with percussion drilling have been reported in the literature, only few papers are dedicated to trepanning drilling. In this context, we present some results on the influence of pulse duration on gas-assisted laser drilling of stainless steel using a trepanning head and a high power Ytterbium doped fiber ultrafast laser (20W). The influence of pulse energy (7- 64μJ), fluence (3-25 J/cm2), drilling time (1-20s), processing gas pressure and drilling strategy will be discussed as well.

  20. Assessment of classical performance measures and signature indices from Flow Duration Curves for model evaluation.

    NASA Astrophysics Data System (ADS)

    Ley, Rita; Hellebrand, Hugo; Casper, Markus C.; Fenicia, Fabrizio

    2015-04-01

    The result of model evaluation is strongly influenced by the choice of the used performance measures. There exist a large variety of performance measures, each with its strengths and weaknesses. Although all of them represent the ability of a hydrological model to reproduce observed stream flow, it is unclear which one is most appropriate for specific applications. The objective of this study is to investigate which performance measure is best suited to find a best performing model structure for a single basin out of multiple model structures. We compare the usability of a new performance measure, the Standardized Signature Index Sum, with several classical statistical performance measures and hydrological performance measures like the Root Mean Square Error or the Nash and Sutcliffe Efficiency. In contrast to the classical and hydrological performance measures, the Standardized Signature Index Sum is based on the comparison of observed and simulated Flow Duration Curves (FDCs). It combines the performance for different parts of the FDC to one measure considering the whole FDC and therefore the whole hydrograph. For this purpose 12 model structures were generated using the SUPERFLEX modeling framework and applied to 53 meso-scale basins in Rhineland Palatinate (Germany). For all calibrated models based on the 12 model structures and 53 basins, we calculate several performance measures and compare their usability to identify a best performing model structure for each basin. In many cases the classical performance measures and the hydrological performance measures assigned similar values to seemingly different hydrographs simulated with different model structures. Therefore, these measures are not well suited for model comparison. The proposed Standardized Signature Index Sum is more effective in revealing differences between model results. Furthermore, it provides information in which part of the hydrograph and how a model fails. The Signature Index Sum allows for a

  1. Piston cylinder cell for high pressure ultrasonic pulse echo measurements

    NASA Astrophysics Data System (ADS)

    Kepa, M. W.; Ridley, C. J.; Kamenev, K. V.; Huxley, A. D.

    2016-08-01

    Ultrasonic techniques such as pulse echo, vibrating reed, or resonant ultrasound spectroscopy are powerful probes not only for studying elasticity but also for investigating electronic and magnetic properties. Here, we report on the design of a high pressure ultrasonic pulse echo apparatus, based on a piston cylinder cell, with a simplified electronic setup that operates with a single coaxial cable and requires sample lengths of mm only. The design allows simultaneous measurements of ultrasonic velocities and attenuation coefficients up to a pressure of 1.5 GPa. We illustrate the performance of the cell by probing the phase diagram of a single crystal of the ferromagnetic superconductor UGe2.

  2. Piston cylinder cell for high pressure ultrasonic pulse echo measurements.

    PubMed

    Kepa, M W; Ridley, C J; Kamenev, K V; Huxley, A D

    2016-08-01

    Ultrasonic techniques such as pulse echo, vibrating reed, or resonant ultrasound spectroscopy are powerful probes not only for studying elasticity but also for investigating electronic and magnetic properties. Here, we report on the design of a high pressure ultrasonic pulse echo apparatus, based on a piston cylinder cell, with a simplified electronic setup that operates with a single coaxial cable and requires sample lengths of mm only. The design allows simultaneous measurements of ultrasonic velocities and attenuation coefficients up to a pressure of 1.5 GPa. We illustrate the performance of the cell by probing the phase diagram of a single crystal of the ferromagnetic superconductor UGe2. PMID:27587156

  3. Electron density measurements in a pulse-repetitive microwave discharge in air

    SciTech Connect

    Nikolic, M.; Popovic, S.; Vuskovic, L.; Herring, G. C.; Exton, R. J.

    2011-12-01

    We have developed a technique for absolute measurements of electron density in pulse-repetitive microwave discharges in air. The technique is based on the time-resolved absolute intensity of a nitrogen spectral band belonging to the Second Positive System, the kinetic model and the detailed particle balance of the N{sub 2}C{sup 3}{Pi}{sub u} ({nu} = 0) state. This new approach bridges the gap between two existing electron density measurement methods (Langmuir probe and Stark broadening). The electron density is obtained from the time-dependent rate equation for the population of N{sub 2}C{sup 3}{Pi}{sub u} ({nu} = 0) using recorded waveforms of the absolute C{sup 3}{Pi}{sub u}{yields}B{sup 3}{Pi}{sub g} (0-0) band intensity, the forward and reflected microwave power density. Measured electron density waveforms using numerical and approximated analytical methods are presented for the case of pulse repetitive planar surface microwave discharge at the aperture of a horn antenna covered with alumina ceramic plate. The discharge was generated in air at 11.8 Torr with a X-band microwave generator using 3.5 {mu}s microwave pulses at peak power of 210 kW. In this case, we were able to time resolve the electron density within a single 3.5 {mu}s pulse. We obtained (9.0 {+-} 0.6) x 10{sup 13} cm{sup -3} for the peak and (5.0 {+-} 0.6) x 10{sup 13} cm{sup -3} for the pulse-average electron density. The technique presents a convenient, non-intrusive diagnostic method for local, time-defined measurements of electron density in short duration discharges near atmospheric pressures.

  4. Spectral encoding method for measuring the relative arrival time between x-ray/optical pulses

    SciTech Connect

    Bionta, M. R.; Hartmann, N.; Weaver, M.; French, D.; Glownia, J. M.; Bostedt, C.; Chollet, M.; Ding, Y.; Fritz, D. M.; Fry, A. R.; Krzywinski, J.; Lemke, H. T.; Messerschmidt, M.; Schorb, S.; Zhu, D.; White, W. E.; Nicholson, D. J.; Cryan, J. P.; Baker, K.; Kane, D. J.; and others

    2014-08-15

    The advent of few femtosecond x-ray light sources brings promise of x-ray/optical pump-probe experiments that can measure chemical and structural changes in the 10–100 fs time regime. Widely distributed timing systems used at x-ray Free-Electron Laser facilities are typically limited to above 50 fs fwhm jitter in active x-ray/optical synchronization. The approach of single-shot timing measurements is used to sort results in the event processing stage. This has seen wide use to accommodate the insufficient precision of active stabilization schemes. In this article, we review the current technique for “measure-and-sort” at the Linac Coherent Light Source at the SLAC National Accelerator Laboratory. The relative arrival time between an x-ray pulse and an optical pulse is measured near the experimental interaction region as a spectrally encoded cross-correlation signal. The cross-correlation provides a time-stamp for filter-and-sort algorithms used for real-time sorting. Sub-10 fs rms resolution is common in this technique, placing timing precision at the same scale as the duration of the shortest achievable x-ray pulses.

  5. Arterial compliance probe for local blood pulse wave velocity measurement.

    PubMed

    Nabeel, P M; Joseph, Jayaraj; Sivaprakasam, Mohanasankar

    2015-08-01

    Arterial compliance and vessel wall dynamics are significant in vascular diagnosis. We present the design of arterial compliance probes for measurement of local pulse wave velocity (PWV). Two designs of compliance probe are discussed, viz (a) a magnetic plethysmograph (MPG) based probe, and (b) a photoplethysmograph (PPG) based probe. The ability of the local PWV probes to consistently capture carotid blood pulse waves is verified by in-vivo trials on few volunteers. The probes could reliably perform repeatable measurements of local PWV from carotid artery along small artery sections less than 20 mm. Further, correlation between the measured values of local PWV using probes and various measures of blood pressure (BP) was also investigated. The study indicates that such arterial compliance probes have strong potential in cuff less BP monitoring. PMID:26737589

  6. Electronic measurement of microchannel plate pulse height distributionsa)

    NASA Astrophysics Data System (ADS)

    Gamboa, E. J.; Huntington, C. M.; Harding, E. C.; Drake, R. P.

    2010-10-01

    Microchannel plates are a central component of the x-ray framing cameras used as analog imagers in many plasma experiment diagnostic systems. The microchannel plate serves as an amplifying element, increasing the electronic signal from incident radiation by factors of 103-105, with a broad pulse-height distribution. Seeking to optimize the photon-to-electron conversion efficiency and noise distribution of x-ray cameras, we will characterize the pulse-height distribution of the electron output from a single microchannel plate. Replacing the framing camera's phosphor-coated fiber optic screen with a charge-collection plate and coupling to a low-noise multichannel analyzer, we quantified the distribution in the total charge generated per photon event. The electronically measured pulse height distribution is used to estimate the signal-to-noise ratio of radiographic images from framing cameras.

  7. Noninvasive porosity measurement of biconvex tablets using terahertz pulses.

    PubMed

    Bawuah, Prince; Ervasti, Tuomas; Tan, Nicholas; Zeitler, J Axel; Ketolainen, Jarkko; Peiponen, Kai-Erik

    2016-07-25

    Biconvex pharmaceutical microcrystalline cellulose (MCC) compacts were investigated by the detection of terahertz (THz) pulse delay in the transmission measurement mode. The dimensions of the tablets were kept as constants but the porosity was a priori known variable. It is shown that the porosity of the biconvex compact has a linear correlation with the THz pulse delay. By constructing a calibration line between these two parameters (i.e. porosity and THz pulse delay), it is possible to non-invasively detect porosity of biconvex tablets. We suggest that this preliminary study could be the starting point of in-depth future studies on the screening of porosity and related properties of real biconvex pharmaceutical tablets using terahertz sensing techniques. PMID:27289013

  8. Future radiation measurements in low Earth orbit. [long duration exposure facility

    NASA Technical Reports Server (NTRS)

    Adams, James H., Jr.

    1992-01-01

    The first Long Duration Exposure Facility (LDEF) mission has demonstrated the value of the LDEF concept for deep surveys of the space radiation environment. This paper will survey the types of measurements that could be done on a second LDEF mission. One of the most surprising discoveries on LDEF1 was the Be-7 that was found imbedded on the windward surface. LDEF2 could follow up on this discovery and search for evidence of other cosmogenic nuclei. Another experiment could be designed to investigate the presence of energetic heavy ions observed on LDEF1. The relative abundance of rare earths can also be used to search for evidence that cosmic rays accelerate in episodes which occur throughout their propagation in the stellar medium. Further investigations of radiation effects could also be undertaken. A second LDEF mission also offers the opportunity for new investigations such as measurements of cosmic ray differential energy spectrum to ultrahigh energies. These and other ideas will be discussed.

  9. Investigating signatures of cosmological time dilation in duration measures of prompt gamma-ray burst light curves

    NASA Astrophysics Data System (ADS)

    Littlejohns, O. M.; Butler, N. R.

    2014-11-01

    We study the evolution with redshift of three measures of gamma-ray burst (GRB) duration (T90, T50 and TR45) in a fixed rest-frame energy band for a sample of 232 Swift/Burst Alert Telescope (BAT) detected GRBs. Binning the data in redshift we demonstrate a trend of increasing duration with increasing redshift that can be modelled with a power law for all three measures. Comparing redshift defined subsets of rest-frame duration reveals that the observed distributions of these durations are broadly consistent with cosmological time dilation. To ascertain if this is an instrumental effect, a similar analysis of Fermi/Gamma-ray Burst Monitor data for the 57 bursts detected by both instruments is conducted, but inconclusive due to small number statistics. We then investigate underpopulated regions of the duration redshift parameter space. We propose that the lack of low-redshift, long duration GRBs is a physical effect due to the sample being volume limited at such redshifts. However, we also find that the high-redshift, short duration region of parameter space suffers from censorship as any Swift GRB sample is fundamentally defined by trigger criteria determined in the observer frame energy band of Swift/BAT. As a result, we find that the significance of any evidence for cosmological time dilation in our sample of duration measures typically reduces to <2σ.

  10. Nonperturbative measurement of the local magnetic field using pulsed polarimetry for fusion reactor conditions (invited)

    SciTech Connect

    Smith, Roger J.

    2008-10-15

    A novel diagnostic technique for the remote and nonperturbative sensing of the local magnetic field in reactor relevant plasmas is presented. Pulsed polarimetry [Patent No. 12/150,169 (pending)] combines optical scattering with the Faraday effect. The polarimetric light detection and ranging (LIDAR)-like diagnostic has the potential to be a local B{sub pol} diagnostic on ITER and can achieve spatial resolutions of millimeters on high energy density (HED) plasmas using existing lasers. The pulsed polarimetry method is based on nonlocal measurements and subtle effects are introduced that are not present in either cw polarimetry or Thomson scattering LIDAR. Important features include the capability of simultaneously measuring local T{sub e}, n{sub e}, and B{sub ||} along the line of sight, a resiliency to refractive effects, a short measurement duration providing near instantaneous data in time, and location for real-time feedback and control of magnetohydrodynamic (MHD) instabilities and the realization of a widely applicable internal magnetic field diagnostic for the magnetic fusion energy program. The technique improves for higher n{sub e}B{sub ||} product and higher n{sub e} and is well suited for diagnosing the transient plasmas in the HED program. Larger devices such as ITER and DEMO are also better suited to the technique, allowing longer pulse lengths and thereby relaxing key technology constraints making pulsed polarimetry a valuable asset for next step devices. The pulsed polarimetry technique is clarified by way of illustration on the ITER tokamak and plasmas within the magnetized target fusion program within present technological means.

  11. Nonperturbative measurement of the local magnetic field using pulsed polarimetry for fusion reactor conditions (invited).

    PubMed

    Smith, Roger J

    2008-10-01

    A novel diagnostic technique for the remote and nonperturbative sensing of the local magnetic field in reactor relevant plasmas is presented. Pulsed polarimetry [Patent No. 12/150,169 (pending)] combines optical scattering with the Faraday effect. The polarimetric light detection and ranging (LIDAR)-like diagnostic has the potential to be a local B(pol) diagnostic on ITER and can achieve spatial resolutions of millimeters on high energy density (HED) plasmas using existing lasers. The pulsed polarimetry method is based on nonlocal measurements and subtle effects are introduced that are not present in either cw polarimetry or Thomson scattering LIDAR. Important features include the capability of simultaneously measuring local T(e), n(e), and B(parallel) along the line of sight, a resiliency to refractive effects, a short measurement duration providing near instantaneous data in time, and location for real-time feedback and control of magnetohydrodynamic (MHD) instabilities and the realization of a widely applicable internal magnetic field diagnostic for the magnetic fusion energy program. The technique improves for higher n(e)B(parallel) product and higher n(e) and is well suited for diagnosing the transient plasmas in the HED program. Larger devices such as ITER and DEMO are also better suited to the technique, allowing longer pulse lengths and thereby relaxing key technology constraints making pulsed polarimetry a valuable asset for next step devices. The pulsed polarimetry technique is clarified by way of illustration on the ITER tokamak and plasmas within the magnetized target fusion program within present technological means. PMID:19044521

  12. Multifunctional optical correlator for picosecond ultraviolet laser pulse measurement

    DOE PAGESBeta

    Rakhman, Abdurahim; Wang, Yang; Garcia, Frances; Long, Cary D.; Huang, Chunning; Takeda, Yasuhiro; Liu, Yun

    2014-01-01

    A compact optical correlator system that measures both the autocorrelation between two infrared (IR) lights and the cross-correlation between an IR and an ultraviolet (UV) light using a single nonlinear optical crystal has been designed and experimentally demonstrated. The rapid scanning of optical delay line, switching between auto and cross-correlations, crystal angle tuning, and data acquisition and processing are all computer controlled. Pulse widths of an IR light from a mode-locked laser are measured by the correlator and the results are compared with a direct measurement using a high-speed photodetector system. The correlator has been used to study the parametermore » dependence of the pulse width of a macropulse UV laser designed for laser-assisted hydrogen ion (H-) beam stripping for the Spallation Neutron Source at Oak Ridge National Laboratory.« less

  13. Multifunctional optical correlator for picosecond ultraviolet laser pulse measurement

    SciTech Connect

    Rakhman, Abdurahim; Wang, Yang; Garcia, Frances; Long, Cary D.; Huang, Chunning; Takeda, Yasuhiro; Liu, Yun

    2014-01-01

    A compact optical correlator system that measures both the autocorrelation between two infrared (IR) lights and the cross-correlation between an IR and an ultraviolet (UV) light using a single nonlinear optical crystal has been designed and experimentally demonstrated. The rapid scanning of optical delay line, switching between auto and cross-correlations, crystal angle tuning, and data acquisition and processing are all computer controlled. Pulse widths of an IR light from a mode-locked laser are measured by the correlator and the results are compared with a direct measurement using a high-speed photodetector system. The correlator has been used to study the parameter dependence of the pulse width of a macropulse UV laser designed for laser-assisted hydrogen ion (H-) beam stripping for the Spallation Neutron Source at Oak Ridge National Laboratory.

  14. Electrical measurement techniques for pulsed high current electron beams

    SciTech Connect

    Struve, K.W.

    1986-04-01

    The advent of high current (1 to 100 kA), moderate energy (>10 MeV), short pulse (1 to 100 ns) electron accelerators used for charged particle beam research has motivated a need to complement standard diagnostics with development of new diagnostic techniques to measure electron beam parameters. A brief survey is given of the diagnostics for measuring beam current, position, size, energy, and emittance. While a broad scope of diagnostics will be discussed, this survey will emphasize diagnostics used on the Experimental Test Accelerator (ETA) and Advanced Test Accelerator (ATA). Focus is placed on diagnostics measuring beam current, position and size. Among the diagnostics discussed are resistive wall current monitors, B/sub theta/ loops, Rogowski coils, Faraday cups, and x-ray wire diagnostics. Operation at higher current levels also increases radiation and electromagnetic pulse interference. These difficulties and methods for circumventing them are also discussed.

  15. Pulse height spectrum measurement experiment for code benchmarking: first results

    SciTech Connect

    Sale, K E; Hall, J M; Brown, C M

    2000-10-27

    The authors have completed a set of gamma-ray pulse height benchmark experiments using a high purity germanium detector to measure absolute counting rate spectra from {sup 60}Co, {sup 137}Cs and {sup 57}Co isotopic sources. The detector was carefully shielded and collimated so that the geometry of the system was completely known. The measured absolute pulse height spectrum counting rates as a function of detector position relative to the source are compared to energy deposit spectra calculated using the Monte Carlo radiation transport code COG. They present here a small subset of our results. The agreement between the calculated and measured spectra and known sources of discrepancies will be discussed.

  16. Pulsed eddy current thickness measurements of transuranic waste containers

    SciTech Connect

    O`Brien, T.K.; Kunerth, D.C.

    1995-12-31

    Thickness measurements on fifty five gallon waste drums for drum integrity purposes have been traditionally performed at the INEL using ultrasonic testing methods. Ultrasonic methods provide high resolution repeatable thickness measurements in a timely manner, however, the major drawback of using ultrasonic techniques is coupling to the drum. Areas with severe exterior corrosion, debonded paper labels or any other obstacle in the acoustic path will have to be omitted from the ultrasonic scan. We have developed a pulsed eddy current scanning system that can take thickness measurements on fifty five gallon carbon steel drums with wall thicknesses up to 65 mils. This type of measurement is not susceptible to the problems mentioned above. Eddy current measurements in the past have excluded ferromagnetic materials such as carbon steel because of the difficulty in penetrating the material and in compensating for changes in permeability from material to material. New developments in data acquisition electronics as well as advances in personal computers have made a pulsed eddy current system practical and inexpensive. Certain aspects of the pulsed eddy current technique as well as the operation of such a system and features such as real time pass/fail thresholds for overpacking identification and full scan data archiving for future evaluation will be discussed.

  17. Time- and frequency-dependent model of time-resolved coherent anti-Stokes Raman scattering (CARS) with a picosecond-duration probe pulse

    NASA Astrophysics Data System (ADS)

    Stauffer, Hans U.; Miller, Joseph D.; Slipchenko, Mikhail N.; Meyer, Terrence R.; Prince, Benjamin D.; Roy, Sukesh; Gord, James R.

    2014-01-01

    The hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) technique presents a promising alternative to either fs time-resolved or ps frequency-resolved CARS in both gas-phase thermometry and condensed-phase excited-state dynamics applications. A theoretical description of time-dependent CARS is used to examine this recently developed probe technique, and quantitative comparisons of the full time-frequency evolution show excellent accuracy in predicting the experimental vibrational CARS spectra obtained for two model systems. The interrelated time- and frequency-domain spectral signatures of gas-phase species produced by hybrid fs/ps CARS are explored with a focus on gas-phase N2 vibrational CARS, which is commonly used as a thermometric diagnostic of combusting flows. In particular, we discuss the merits of the simple top-hat spectral filter typically used to generate the ps-duration hybrid fs/ps CARS probe pulse, including strong discrimination against non-resonant background that often contaminates CARS signal. It is further demonstrated, via comparison with vibrational CARS results on a time-evolving solvated organic chromophore, that this top-hat probe-pulse configuration can provide improved spectral resolution, although the degree of improvement depends on the dephasing timescales of the observed molecular modes and the duration and timing of the narrowband final pulse. Additionally, we discuss the virtues of a frequency-domain Lorentzian probe-pulse lineshape and its potential for improving the hybrid fs/ps CARS technique as a diagnostic in high-pressure gas-phase thermometry applications.

  18. Time- and frequency-dependent model of time-resolved coherent anti-Stokes Raman scattering (CARS) with a picosecond-duration probe pulse.

    PubMed

    Stauffer, Hans U; Miller, Joseph D; Slipchenko, Mikhail N; Meyer, Terrence R; Prince, Benjamin D; Roy, Sukesh; Gord, James R

    2014-01-14

    The hybrid femtosecond∕picosecond coherent anti-Stokes Raman scattering (fs∕ps CARS) technique presents a promising alternative to either fs time-resolved or ps frequency-resolved CARS in both gas-phase thermometry and condensed-phase excited-state dynamics applications. A theoretical description of time-dependent CARS is used to examine this recently developed probe technique, and quantitative comparisons of the full time-frequency evolution show excellent accuracy in predicting the experimental vibrational CARS spectra obtained for two model systems. The interrelated time- and frequency-domain spectral signatures of gas-phase species produced by hybrid fs∕ps CARS are explored with a focus on gas-phase N2 vibrational CARS, which is commonly used as a thermometric diagnostic of combusting flows. In particular, we discuss the merits of the simple top-hat spectral filter typically used to generate the ps-duration hybrid fs∕ps CARS probe pulse, including strong discrimination against non-resonant background that often contaminates CARS signal. It is further demonstrated, via comparison with vibrational CARS results on a time-evolving solvated organic chromophore, that this top-hat probe-pulse configuration can provide improved spectral resolution, although the degree of improvement depends on the dephasing timescales of the observed molecular modes and the duration and timing of the narrowband final pulse. Additionally, we discuss the virtues of a frequency-domain Lorentzian probe-pulse lineshape and its potential for improving the hybrid fs∕ps CARS technique as a diagnostic in high-pressure gas-phase thermometry applications. PMID:24437886

  19. Analytical spectroscopic investigation of wavelength and pulse duration effects on laser-induced changes of egg-yolk-based tempera paints.

    PubMed

    Oujja, Mohamed; Pouli, Paraskevi; Domingo, Concepción; Fotakis, Costas; Castillejo, Marta

    2010-05-01

    The application of laser cleaning methodologies to light-sensitive substrates such as those encountered in artistic paintings is an extremely delicate issue. The cleaning of paintings and polychromes is an irreversibly invasive intervention; therefore, prior to the implementation of laser cleaning methodologies, a thorough characterization of the interaction between laser pulses and painting components is required. In this work, the modifications induced by irradiation with pulses of 150 picoseconds (at 1064 and 213 nm) and 15 nanoseconds (at 213 nm) on unvarnished aged model egg-yolk-based paints were examined following a spectroanalytical approach. Laser-induced chemical changes on samples of unpigmented and widely used artist's pigment temperas were investigated by spectrofluorimetry and Fourier transform Raman spectroscopy, while color changes were quantified by colorimetry. Noticeable modifications of the Raman and fluorescence bands attributed to pigments are absent except for vermillion, for which the pigment bands tend to disappear upon irradiation at 1064 nm. Interestingly, no discoloration was observed on most of the pigments upon irradiation at 213 nm (150 ps), including the light-sensitive vermillion, while no indications of carbonization or charring of the paint layers, which could give rise to amorphous carbon bands, were obtained at any of the irradiation conditions explored. Comparison of the results using the two different pulse durations and wavelengths illustrates the participation of mechanisms of diverse origin according to the chemical composition of the pigment and highlights the importance of the optimization of the laser parameters, specifically fluence, pulse duration, and wavelength, in conservation treatments of paintings. PMID:20482972

  20. Measuring multimegavolt pulsed voltages using Compton-generated electrons

    NASA Astrophysics Data System (ADS)

    Swanekamp, S. B.; Weber, B. V.; Pereira, N. R.; Hinshelwood, D. D.; Stephanakis, S. J.; Young, F. C.

    2004-01-01

    The "Compton-Hall" voltmeter is a radiation-based voltage diagnostic that has been developed to measure voltages on high-power (TW) pulsed generators. The instrument collimates photons generated from bremsstrahlung produced in the diode onto an aluminum target to generate Compton-generated electrons. Permanent magnets bend the Compton electron orbits that escape the target toward a silicon pin diode detector. A GaAs photoconductive detector (PCD) detects photons that pass through the Compton target. The diode voltage is determined from the ratio of the electron dose in the pin detector to the x-ray dose in the PCD. The Integrated Tiger Series of electron-photon transport codes is used to determine the relationship between the measured dose ratio and the diode voltage. Variations in the electron beam's angle of incidence on the bremsstrahlung target produce changes in the shape of the photon spectrum that lead to large variations in the voltage inferred from the voltmeter. The voltage uncertainty is minimized when the voltmeter is fielded at an angle of 45° with respect to the bremsstrahlung target. In this position, the photon spectra for different angles of incidence all converge onto a single spectrum reducing the uncertainty in the voltage to less than 10% for voltages below 4 MV. Higher and lower voltages than the range considered in this article can be measured by adjusting the strength of the applied magnetic field or the position of the electron detector relative to the Compton target. The instrument was fielded on the Gamble II pulsed-power generator configured with a plasma opening switch. Measurements produced a time-dependent voltage with a peak (3.7 MV) that agrees with nuclear activation measurements and a pulse shape that is consistent with the measured radiation pulse shape.

  1. Long Duration Exposure Facility post-flight data as it influences the Tropical Rainfall Measuring Mission

    NASA Technical Reports Server (NTRS)

    Straka, Sharon A.

    1995-01-01

    The Tropical Rainfall Measuring Mission (TRMM) is an earth observing satellite that will be in a low earth orbit (350 kilometers) during the next period of maximum solar activity. The TRMM observatory is expected to experience an atomic oxygen fluence of 8.9 x 10(exp 22) atoms per square centimeter. This fluence is ten times higher than the atomic oxygen impingement incident to the Long Duration Exposure Facility (LDEF). Other environmental concerns on TRMM include: spacecraft glow, silicon oxide contaminant build-up, severe spacecraft material degradation, and contamination deposition resulting from molecular interactions with the dense ambient atmosphere. Because of TRMM's predicted harsh environment, TRMM faces many unique material concerns and subsystem design issues. The LDEF data has influenced the design of TRMM and the TRMM material selection process.

  2. Microwave pulse propagation measurements in left-handed materials

    NASA Astrophysics Data System (ADS)

    di Gennaro, Emiliano; Parimi, Patanjali V.; Vodo, Plarenta; Lu, Wentao; Sridhar, Srinivas

    2004-03-01

    Left handed electromagnetism is well established in media with negative permeability and permittivity and in photonic crystals [1]. In such media the negative refractive index is accompanied by large dispersion dn/dω, and consequently a very low group velocity is predicted for left-handed metamaterial (LHM). It is well known that an artificial material consisting of interleaved arrays of wires and split ring resonators in a certain microwave frequency range shows left handed behavior. We have carried out pulse measurements on LHM using a transition analyzer in order to measure the group velocity. Time delay measurements are performed in an X-band and parallel plate waveguide. Sending a 100ns width pulse with a carrier frequency ranging between 9 and 11 GHz, we analyze the signal delay due to the sample. The results suggest that the group velocity in the LHM is very low. Pulse delay measurements in photonic crystals are also discussed. Work supported by NSF & AFRL [1]. P. V. Parimi et al., submitted (2003).

  3. A Resonant Cavity Approach to Non-Invasive, Pulse-to-Pulse EmittanceMeasurement

    SciTech Connect

    Kim, J.S.; Nantista, C.D.; Miller, R.H.; Weidemann, A.W.; /FARTECH, San Diego /SLAC

    2010-06-15

    We present a resonant cavity approach for non-invasive, pulse-to-pulse, beam emittance measurements of non-circular multi-bunch beams. In a resonant cavity, desired field components can be enhanced up to Q{sub L{lambda}}/{pi}, where Q{sub L{lambda}} is the loaded quality factor of the resonant mode {lambda}, when the cavity resonant mode matches the bunch frequency of a bunch-train beam pulse. In particular, a quad-cavity, with its quadrupole mode (TM{sub 220} for rectangular cavities) at beam operating frequency, rotated 45{sup o} with respect to the beamline, extracts the beam quadrupole moment exclusively, utilizing the symmetry of the cavity and some simple networks to suppress common modes. Six successive beam quadrupole moment measurements, performed at different betatron phases in a linear transport system determine the beam emittance, i.e. the beam size and shape in the beam's phase space, if the beam current and position at these points are known. In the presence of x-y beam coupling, ten measurements are required. One measurement alone provides the rms-beam size of a large aspect ratio beam. The resolution for such a measurement of rms-beam size with the rectangular quad-cavity monitor presented in this article is estimated to be on the order of ten microns. A prototype quad-cavity was fabricated and preliminary beam tests were performed at the Next Linear Collider Test Accelerator (NLCTA) at the Stanford Linear Accelerator Center (SLAC). Results were mainly limited by beam jitter and uncertainty in the beam position measurement at the cavity location. This motivated the development of a position-emittance integrated monitor.

  4. Setup for fast-pulsed measurements of large critical currents

    NASA Astrophysics Data System (ADS)

    D'Ovidio, Claudio Alberto; Esparza, Daniel Antonio; Malachevsky, Maria Teresa

    2000-07-01

    We describe a set of equipments for pulsed measurements of transport critical currents in superconducting materials having a critical current of tens or hundreds of amperes. It is based on the appliance of an electrical current for a very short period of time, rapid enough to preserve the integrity of the current leads and to minimize the Joule effect. Power is applied to the wire-sample setup and the voltage drop is measured within seconds, with a resolution of the order of 10 nV. In this way the I- V characteristics can be obtained with a 1% error, if the 1 μV/ cm criterion is employed. The hardware is composed of three parts: the current pulse generator, a fast low-noise voltage amplifier and a PC with a DAC-ADC card. The data acquisition is achieved via an Assembler program.

  5. Water depth measurement using an airborne pulsed neon laser system

    NASA Technical Reports Server (NTRS)

    Hoge, F. E.; Swift, R. N.; Frederick, E. B.

    1980-01-01

    The paper presents the water depth measurement using an airborne pulsed neon laser system. The results of initial base-line field test results of NASA airborne oceanographic lidar in the bathymetry mode are given, with water-truth measurements of depth and beam attenuation coefficients by boat taken at the same time as overflights to aid in determining the system's operational performance. The nadir-angle tests and field-of-view data are presented; this laser bathymetry system is an improvement over prior models in that (1) the surface-to-bottom pulse waveform is digitally recorded on magnetic tape, and (2) wide-swath mapping data may be routinely acquired using a 30 deg full-angle conical scanner.

  6. 180 mJ, long-pulse-duration, master-oscillator power amplifier with linewidth less than 25.6 kHz for laser guide stars.

    PubMed

    Wang, Chunhua; Zhang, Xiang; Ye, Zhibin; Liu, Chong; Chen, Jun

    2013-07-01

    A high-energy single-frequency hundred-microsecond long-pulse solid-state laser is demonstrated, which features an electro-optically modulated seed laser and two-stage double-passed pulse-pumped solid-state laser rod amplifier. Laser output with energy of 180 mJ, repetition rate of 50 Hz, and pulse width of 150 μs is achieved. The laser linewidth is measured to be less than 25.52 kHz by a fiber delay self-heterodyne method. In addition, a closed-loop controlling system is adopted to lock the center wavelength. No relaxation oscillation spikes appear in the pulse temporal profile, which is beneficial for further amplification. PMID:23842267

  7. Desynchronization of electrically evoked auditory-nerve activity by high-frequency pulse trains of long duration

    NASA Astrophysics Data System (ADS)

    Litvak, Leonid M.; Smith, Zachary M.; Delgutte, Bertrand; Eddington, Donald K.

    2003-10-01

    Rubinstein et al. [Hear. Res. 127, 108-118 (1999)] suggested that the neural representation of the waveforms of electric stimuli might be improved by introducing an ongoing, high-rate, desynchronizing pulse train (DPT). A DPT may desynchronize neural responses to electric stimulation in a manner similar to spontaneous activity in a healthy ear. To test this hypothesis, responses of auditory-nerve fibers (ANFs) to 10-min-long electric pulse trains (5 kpps) were recorded from acutely deafened, anesthetized cats. Stimuli were delivered via an intracochlear electrode, and their amplitude was chosen to elicit a response in most ANFs. Responses to pulse trains showed pronounced adaptation during the first 1-2 min, followed by either a sustained response or cessation of spike discharges for the remainder of the stimulus. The adapted discharge rates showed a broad distribution across the ANF population like spontaneous activity. However, a higher proportion of fibers (46%) responded to the DPT at rates below 5 spikes/s than for spontaneous activity, and 12% of the fibers responded at higher rates than any spontaneously active fiber. Interspike interval histograms of sustained responses for some fibers had Poisson-like (exponential) shapes, resembling spontaneous activity, while others exhibited preferred intervals and, occasionally, bursting. Simultaneous recordings from pairs of fibers revealed no evidence of correlated activity, suggesting that the DPT does desynchronize the auditory nerve activity. Overall, these results suggest that responses to an ongoing DPT resemble spontaneous activity in a normal ear for a substantial fraction of the ANFs.

  8. Radioactive effluent measurements at the Army Pulse Radiation Facility

    SciTech Connect

    Scherpelz, R.I.; Glissmeyer, J.A.

    1994-11-01

    Staff from the Pacific Northwest Laboratory (PNL) performed measurements of the radioactive effluents emitted by the Army Pulse Radiation Facility (APRF). These measurements were performed by collecting the cooling air that passed by the APRF reactor as it operated, passing the air through filters to collect the particulates and iodines, and collecting samples of the air to be analyzed for noble gases. The reactor operated for four test runs, including two pulses and two steady state runs. After each reactor run, the filters were counted using gamma spectrometry to identify the nuclides and to determine the activity of nuclides deposited on the filters. The study provided radionuclide release fraction data that can be used to estimate the airborne emissions resulting from APRF operations. The release fraction for particulate fission products and radioiodines, as derived from these measurements, was found to be 8.9 {times} 10{sup {minus}6} for reactor pulses and 4.3 {times} 10{sup {minus}6} for steady state operation. These values compare to a theoretical value of 1.5 {times} 10{sup {minus}5}.

  9. Nozzle geometry and injection duration effects on diesel sprays measured by x-ray radiography.

    SciTech Connect

    Kastengren, A. L.; Powell, C. F.; Riedel, T.; Cheong, S.-K.; Im, K.-S.; Liu, X.; Wang, Y. J.; Wang, J.; Robert Bosch GmbH

    2008-04-01

    X-ray radiography was used to measure the behavior of four fuel sprays from a light-duty common-rail diesel injector. The sprays were at 250 bar injection pressure and 1 bar ambient pressure. Injection durations of 400 {micro}s and 1000 {micro}s were tested, as were axial single-hole nozzles with hydroground and nonhydroground geometries. The X-ray data provide quantitative measurements of the internal mass distribution of the spray, including near the injector orifice. Such measurements are not possible with optical diagnostics. The 400 {micro}s sprays from the hydroground and nonhydroground nozzles appear qualitatively similar. The 1000 {micro}s spray from the nonhydroground nozzle has a relatively consistent moderate width, while that from the hydroground nozzle is quite wide before transitioning into a narrow jet. The positions of the leading- and trailing-edges of the spray have also been determined, as has the amount of fuel residing in a concentrated structure near the leading edge of the spray.

  10. High-fidelity rotor gap measurements in a short-duration turbine rig

    NASA Astrophysics Data System (ADS)

    Lavagnoli, Sergio; Paniagua, Guillermo; Tulkens, Maxime; Steiner, Alexander

    2012-02-01

    The distance between the tip of rotating airfoils and the stationary casing, i.e., the tip clearance, is a vital parameter to characterize turbomachinery performance. The larger the tip clearance, the lower the turbine efficiency due to the increased loss associated with the hot jet flowing through the gap without generating work. Following the increasing demands in efficiency, these small clearances must be surveyed to avoid mechanical rubbing. The appropriate design of control systems to adjust these small clearances requires a constant monitoring during the whole engine envelope. This paper describes the complete implementation of a high-frequency capacitive sensor on the shroud of a large transonic turbine stage. The presented system and data analysis procedure allow the accurate measurement of the tip clearance of each rotating airfoil. The measurement system performances are first assessed in a simplified test bench and uncertainty analysis is provided. The technique is demonstrated in an aero-propulsion turbine, tested in a short duration rig. The turbine facility has running times of less than 0.5 s, characterized by temperature and rotor speed transients, which requires particular in-situ sensor calibrations. Extensive running tip clearance measurements of the large aero-engine turbine stage validate the system concept and design.

  11. Measuring formation properties through well casing with pulsed neutron instrumentation

    NASA Astrophysics Data System (ADS)

    Trcka, Darryl

    2010-05-01

    Measuring formation properties through well casing with pulsed neutron instrumentation In the process of developing an oil or gas reservoir, the exploration team first confirms the existence of a potential reservoir with a discovery well. Then the size, content, and character of the reservoir are mapped with roughly six to twelve delineation wells. From this information the development team plans a development program to produce the oil and gas, which can run into hundreds of wells. Whereas the exploration and delineation wellbores are left open to the formation to allow measurement of the reservoir properties, the development wellbores are cased with cemented-in-place steel casing to isolate zones and allow targeting of specific oil or gas layers for production (which is accomplished by perforating the casing in the target zones with explosive charges). Once the casing is in place it obviously becomes more difficult to measure reservoir and formation properties since one-quarter to one-half inch of steel casing plus another inch or so of cement between the formation and the borehole greatly restrict the measurement methods that can be used. But there are over a million cased wellbores penetrating the earth's crust, many plugged, cemented, and abandoned, but many still producing oil and gas or otherwise available for logging. However difficult it may be, formation measurements through the steel casing are of importance to oil and gas production companies, and they could be of some value to earth scientists. Since 1964 when the first instrument was introduced, pulsed neutron instrumentation for oil and gas well logging has been used to measure formation properties through casing. The basic downhole instrumentation consists of a pulsed fusion reactor for a source of high energy neutrons and gamma ray detectors for gamma ray spectroscopy. The early generation instruments measured water and oil proportions crudely and only in reservoirs where the connate water was

  12. Transmural Optical Measurements of Vm Dynamics during Long-Duration Ventricular Fibrillation in Canine Hearts

    PubMed Central

    Kong, Wei; Ideker, Raymond E.; Fast, Vladimir G.

    2009-01-01

    Background Knowledge of transmural Vm changes is important for understanding the mechanism of long-duration ventricular fibrillation (LDVF). Methods Vm was recorded optically at up to 8 transmural points separated by 1.5 mm in the left ventricle of Langendorff-perfused canine hearts (n=6) using a bundle of optical fibers (optrode) during 10 min of LDVF followed by 3 min of VF with reperfusion. Measurements were grouped into 4 layers: epicardium, sub-epicardium, midwall and sub-endocardium. Results Activation rates (ARs) and action potential durations (APDs) decreased while diastolic intervals (DIs) increased during LDVF in all transmural layers (p<0.05). After ~3 min of LDVF, ARs were faster and DIs shorter in the midwall and sub-endocardium than in the epicardium and sub-epicardium (p<0.05). Activations persisted at the sub-endocardium but disappeared from other layers after ~8 min of VF in the majority of hearts. There were no transmural differences in APD during LDVF or during pacing before and after LDVF (p>0.05). Restitution plots revealed no functional relationship between APD and DI in any layer at any stage of LDVF. Partial reperfusion during VF for 3 min restored transmural synchronicity of activation and eliminated gradients in activation parameters. Conclusions Vm dynamics evolve differently at different transmural layers. The sub-endocardium maintains persistent and the fastest activation during 10 min of LDVF suggesting it contains the source of VF wavefronts. There are no transmural APD gradients and no restitution relationship between APD and DI at any transmural layer indicating these are not the primary factors in the mechanism of LDVF. PMID:19467507

  13. Performance assessment of thermal sensors during short-duration convective surface heating measurements

    NASA Astrophysics Data System (ADS)

    Sahoo, Niranjan; Kumar, Rakesh

    2015-10-01

    The determination of convective surface heating is a very crucial parameter in high speed flow environment. Most of the ground based facilities in this domain have short duration experimental time scale (~milliseconds) of measurements. In these facilities, the calorimetric heat transfer sensors such as thin film gauges (TFGs) and coaxial surface junction thermocouple (CSJT) are quite effective temperature detectors. They have thickness in the range of few microns and have capability of responding in microsecond time scale. The temperature coefficient of resistance (TCR) and the sensitivity are calibration parameter indicators that show the linear change in the resistance of the gauge as a function of temperature. In the present investigation, three of types of heat transfer gauges are fabricated in the laboratory namely, TFG made out of platinum, TFG made out of platinum mixed with CNT and chromel-alumel surface junction coaxial thermocouple (K-type). The calibration parameters of the gauges are determined though oil-bath experiments. The average value TCR and sensitivity of platinum TFG is found to be 0.0024 K-1 and 465 μV/K, while similar values of CSJT are obtained as, 0.064 K-1 and 40.5 μV/K, respectively. The TFG made out of platinum mixed with CNT (5 % by mass) shows the enhancement of TCR as well as sensitivity and the corresponding values are 0.0034 K-1 and 735 μV/K, respectively. The relative performances of heat transfer gauges are compared in a simple laboratory scale experiment in which the gauges are exposed to a sudden step heat load in convection mode for the time duration of 200 ms. The surface heat fluxes are predicted from the temperature history through one dimensional heat conduction modeling. While comparing the experimental results, it is seen that prediction of surface heat flux from all the heat transfer gauges are within the range of ±4 %.

  14. Pulsed Airborne Lidar Measurements of C02 Column Absorption

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Riris, Haris; Allan, Graham R.; Weaver, Clark J.; Mao, Jianping; Sun, Xiaoli; Hasselbrack, William E.; Rodriquez, Michael; Browell, Edward V.

    2011-01-01

    We report on airborne lidar measurements of atmospheric CO2 column density for an approach being developed as a candidate for NASA's ASCENDS mission. It uses a pulsed dual-wavelength lidar measurement based on the integrated path differential absorption (IPDA) technique. We demonstrated the approach using the CO2 measurement from aircraft in July and August 2009 over four locations. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. The 2009 measurements have been analyzed in detail and the results show approx.1 ppm random errors for 8-10 km altitudes and approx.30 sec averaging times. Airborne measurements were also made in 2010 with stronger signals and initial analysis shows approx. 0.3 ppm random errors for 80 sec averaging times for measurements at altitudes> 6 km.

  15. Auditory-nerve responses to varied inter-phase gap and phase duration of the electric pulse stimulus as predictors for neuronal degeneration.

    PubMed

    Ramekers, Dyan; Versnel, Huib; Strahl, Stefan B; Smeets, Emma M; Klis, Sjaak F L; Grolman, Wilko

    2014-04-01

    After severe hair cell loss, secondary degeneration of spiral ganglion cells (SGCs) is observed-a gradual process that spans years in humans but only takes weeks in guinea pigs. Being the target for cochlear implants (CIs), the physiological state of the SGCs is important for the effectiveness of a CI. For assessment of the nerve's state, focus has generally been on its response threshold. Our goal was to add a more detailed characterization of SGC functionality. To this end, the electrically evoked compound action potential (eCAP) was recorded in normal-hearing guinea pigs and guinea pigs that were deafened 2 or 6 weeks prior to the experiments. We evaluated changes in eCAP characteristics when the phase duration (PD) and inter-phase gap (IPG) of a biphasic current pulse were varied. We correlated the magnitude of these changes to quantified histological measures of neurodegeneration (SGC packing density and SGC size). The maximum eCAP amplitude, derived from the input-output function, decreased after deafening, and increased with both PD and IPG. The eCAP threshold did not change after deafening, and decreased with increasing PD and IPG. The dynamic range was wider for the 6-weeks-deaf animals than for the other two groups. Excitability increased with IPG (steeper slope of the input-output function and lower stimulation level at the half-maximum eCAP amplitude), but to a lesser extent for the deafened animals than for normal-hearing controls. The latency was shorter for the 6-weeks-deaf animals than for the other two groups. For several of these eCAP characteristics, the effect size of IPG correlated well with histological measures of degeneration, whereas effect size of PD did not. These correlations depend on the use of high current levels, which could limit clinical application. Nevertheless, their potential of these correlations towards assessment of the condition of the auditory nerve may be of great benefit to clinical diagnostics and prognosis in cochlear

  16. Averaging of Replicated Pulses for Enhanced-Dynamic-Range Single-Shot Measurement of Nanosecond Optical Pulses

    SciTech Connect

    Marciante, J.R.; Donaldson, W.R.; Roides, R.G.

    2007-10-04

    Measuring optical pulse shapes beyond the dynamic range of oscilloscopes is achieved by temporal pulse stacking in a low-loss, passive, fiber-optic network. Optical pulses are averaged with their time-delayed replicas without introducing additional noise or jitter, allowing for high-contrast pulse-shape measurements of single-shot events. A dynamic-range enhancement of three bits is experimentally demonstrated and compared with conventional multi-shot averaging. This technique can be extended to yield an increase of up to seven bits of additional dynamic range over nominal oscilloscope performance.

  17. Mobile micro-pulse lidar measurement in Hong Kong

    NASA Astrophysics Data System (ADS)

    Cheng, A. Y. S.; Walton, A.; Chan, R. L. M.; Chan, C. S.

    2005-05-01

    An eye-safe, mobile micro-pulse Mie lidar system has been established at City University of Hong Kong since November 2002. The system is a co-axial setup with a diode pumped Nd:YAG laser source of 532nm. Since measurements in public areas are required, the system was designed to be eye-safe by operating at a few micro-Joules pulse energy and high repetition rates (1 to 4 kHz) and the beam diameter was expanded to about 3 inches. Since the lower atmosphere is of interest, a co-axial design setup was adopted for improved near range performance. The receiver is a 235mm diameter Schmidt-Cassegrain telescope with a variable iris diaphragm for adjustable field-of-view, allowing for optimal near range or far range measurements. A narrow bandwidth filter (0.3nm) is used to reduce the stron solar radiation. The system is housed in a small van for field measurements at various sites around Hong Kong. Data is inverted using Fernald's method to obtain extinction profiles. Aerosol loading and boundary layer height have been examined at several sites for each season of the year 2003. The boundary layer heights obtained from lidar data measured at City University of Hong Kong are compared with radiosonde data measured at the King's Park meteorological station of the Hong Kong Observatory. In addition, seasonal trends of the maximum mixing height (MMH) measured at City University will be discussed.

  18. Pulsed airborne lidar measurements of atmospheric CO2 column absorption

    NASA Astrophysics Data System (ADS)

    Abshire, James B.; Riris, Haris; Allan, Graham R.; Weaver, Clark J.; Mao, Jianping; Sun, Xiaoli; Hasselbrack, William E.; Kawa, S. Randoph; Biraud, Sebastien

    2010-11-01

    ABSTRACT We report initial measurements of atmospheric CO2 column density using a pulsed airborne lidar operating at 1572 nm. It uses a lidar measurement technique being developed at NASA Goddard Space Flight Center as a candidate for the CO2 measurement in the Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) space mission. The pulsed multiple-wavelength lidar approach offers several new capabilities with respect to passive spectrometer and other lidar techniques for high-precision CO2 column density measurements. We developed an airborne lidar using a fibre laser transmitter and photon counting detector, and conducted initial measurements of the CO2 column absorption during flights over Oklahoma in December 2008. The results show clear CO2 line shape and absorption signals. These follow the expected changes with aircraft altitude from 1.5 to 7.1 km, and are in good agreement with column number density estimates calculated from nearly coincident airborne in-situ measurements.

  19. X-ray reverberations and the giant X-ray bursts. [short duration pulse in plasma cloud surrounding X-ray source

    NASA Technical Reports Server (NTRS)

    Canizares, C. R.

    1976-01-01

    It is shown that the shape and spectral evolution of the giant X-ray bursts from the source 3U 1820-30 can be explained by Compton scattering of a short, intense X-ray pulse in a cloud surrounding the source. Pulse shapes due to Thomson scattering of an X-ray burst in an electron cloud were calculated for the (1) optically thin case on the assumption of one scattering per photon, (2) intermediate case with optical depth of about unity, and (3) optically thick case where the process is regarded as diffusion of photons through a uniform sphere. For the intermediate case, the effects of the reverberation were determined explicitly by Monte Carlo calculation. For an optical depth of 3, square pulse duration of 2 sec, characteristic cloud radius of 70,000 km, characteristic cloud density of 4 times 10 to the 14th per cu cm, and temperature of 5-30 keV, the calculations give a reasonably accurate description of X-ray bursts from 3U 1820-30. The scattering model does not imply the existence of a supermassive, central black hole.

  20. Ultrashort-laser-pulse measurement using swept beams.

    PubMed

    O'Shea, D; Kimmel, M; O'Shea, P; Trebino, R

    2001-09-15

    We demonstrate a frequency-resolved optical gating (FROG) device that uses a sweepshot geometry that combines the advantages of multishot and single-shot pulse-measurement devices, has only one moving part, a galvanometer, and requires no computer control. Like a multishot device, it focuses the beam to a small spot (rather than a line focus) and has a high intensity in the nonlinear medium. Like single-shot devices, it makes measurements quickly, generating an entire FROG trace on a single camera screen (rather than requiring many camera downloads). PMID:18049632

  1. Direct nn-Scattering Measurement With the Pulsed Reactor YAGUAR

    PubMed Central

    Mitchell, G. E.; Furman, W. I.; Lychagin, E. V.; Muzichka, A. Yu.; Nekhaev, G. V.; Strelkov, A. V.; Sharapov, E. I.; Shvetsov, V. N.; Chernuhin, Yu. I.; Levakov, B. G.; Litvin, V. I.; Lyzhin, A. E.; Magda, E. P.; Crawford, B. E.; Stephenson, S. L.; Howell, C. R.; Tornow, W

    2005-01-01

    Although crucial for resolving the issue of charge symmetry in the nuclear force, direct measurement of nn-scattering by colliding free neutrons has never been performed. At present the Russian pulsed reactor YAGUAR is the best neutron source for performing such a measurement. It has a through channel where the neutron moderator is installed. The neutrons are counted by a neutron detector located 12 m from the reactor. In preliminary experiments an instantaneous value of 1.1 × 1018/cm2s was obtained for the thermal neutron flux density. The experiment will be performed by the DIANNA Collaboration as International Science & Technology Center (ISTC) project No. 2286. PMID:27308126

  2. Using piezoelectric sensors for ultrasonic pulse velocity measurements in concrete

    NASA Astrophysics Data System (ADS)

    Kee, Seong-Hoon; Zhu, Jinying

    2013-11-01

    The ultrasonic pulse velocity (UPV) test has been a widely used non-destructive testing method for concrete structures. However, the conventional UPV test has limitations in consistency of results and applicability in hard-to-access regions of structures. The authors explore the feasibility of embedded piezoelectric (PZT) sensors for ultrasonic measurements in concrete structures. Two PZT sensors were embedded in a reinforced concrete specimen. One sensor worked as an actuator driven by an ultrasonic pulse-receiver, and another sensor worked as a receiver. A series of ultrasonic tests were conducted to investigate the performance of the embedded sensors in crack-free concrete and concrete specimens having a surface-breaking crack under various external loadings. Signals measured by the embedded sensors show a broad bandwidth with a centre frequency around 80 kHz, and very good coherence in the frequency range from 30 to 180 kHz. Furthermore, experimental variability in ultrasonic pulse velocity and attenuation is substantially reduced compared to previously reported values from conventional UPV equipment. Findings from this study demonstrate that the embedded sensors have great potential as a low-cost solution for ultrasonic transducers for health monitoring of concrete in structures.

  3. Recovery Time Measurements of Silicon Photomultipliers Using a Pulsed Laser

    NASA Astrophysics Data System (ADS)

    Gruber, L.; Brunner, S. E.; Curceanu, C.; Marton, J.; Romero Vidal, A.; Scordo, A.; Suzuki, K.; Vazquez, O. D.

    We performed an experimental study to determine the pixel recovery time of various Multi Pixel Photon Counters (MPPCs) in order to characterize their rate capability and double-hit resolution. The recovery time constant and its dependence on the operating voltage has been evaluated by measuring the photosensor response to two consecutive laser pulses with varying relative time differences of a few ns (2-3 ns) up to some 100 ns using a waveform analysis technique. A Monte Carlo simulation tool is being developed to model the MPPC recovery process and interpret experimental data. In this context, the influence of after-pulsing, cross-talk and dark-noise on the recovery process can be studied.

  4. Plasma detector for TEA CO2 laser pulse measurement

    NASA Astrophysics Data System (ADS)

    Ichikawa, Y.; Yamanaka, M.; Mitsuishi, A.; Fujita, S.; Yamanaka, T.; Yamanaka, C.; Tsunawaki, Y.; Iwasaki, T.; Takai, M.

    1983-10-01

    Laser-pulse evolution can be detected by measuring the emf generated by fast electrons in a laser-produced plasma when the laser radiation is focused onto a solid metal target in a vacuum. Using this phenomenon a 'plasma detector' is constructed, and its characteristics for the TEA CO2 laser radiation of intensity 10 to the 9th to 10 to the 10th W/sq cm are investigated experimentally. The plasma detector operates at room temperature and is strong against laser damages. For the evacuated plasma detector down to 0.1 torr, a maximum output voltage of 90 V and a rise time shorter than 1 ns are observed. The plasma detector, therefore, can be used as a power monitor for laser pulses and as a trigger voltage source.

  5. Leaf wetness duration: importance of estimated and measured data for Plasmopara viticola infection forecasting

    NASA Astrophysics Data System (ADS)

    dalla Marta, A.; de Vincenzi, M.; Dietrich, S.; Orlandini, S.

    2003-04-01

    The use of simulation models and remote sensing data seem to be a useful alternative to leaf wetness duration (LWD) field measurements. In the last years some researchers have applied in agroenvironmental sector a particular type of model: Artificial Neural Networks (ANNs). ANNs are particular devices for numerical elaboration that have the ability to map the input-output relationships between phenomena and their influencing quantities and to make an internal function from a data set given as example. Radar provides a gridded values of LWD with a precise description of climatic spatial variability. The principal aim of this work was to carry out an ANN capable to find out the relationships between the agrometeorological input and LWD and to analyse and compare the impact of radar and ANN estimated and measured LWD on the quality of the epidemiological simulation. All the input data were collected with hourly time step from 3 weather stations placed in Friuli Venezia Giulia (North East of Italy). In this work a progressively higher number of agrometeorological data was used as input for the LWD simulation and the results were compared in order to find out the network structure capable to give the best result with the minimum possible number of input. Air temperature and relative humidity were the first two parameters used for the simulation; in the following elaborations the data of rainfall, wind speed, global solar radiation and vapour pressure deficit were added one by one creating a model each time more complex. LWD data were also obtained from the weather station measurement using leaf wetness gauge, and from the elaboration of rainfall data estimated by a polarimetric radar GPM 500. Finally, the LWD estimated with the above mentioned methods were used, together with measured data, as input for an epidemiological model to predict grapevine downy mildew (Plasmopara viticola) infections.

  6. A new sealed RF-excited CO2 laser for enamel ablation operating at 9.4-μm with a pulse duration of 26-μs

    PubMed Central

    Chan, Kenneth H.; Jew, Jamison M.; Fried, Daniel

    2016-01-01

    Several studies over the past 20 years have shown that carbon dioxide lasers operating at wavelengths between 9.3 and 9.6-μm with pulse durations near 20-μs are ideal for hard tissue ablation. Those wavelengths are coincident with the peak absorption of the mineral phase. The pulse duration is close to the thermal relaxation time of the deposited energy of a few microseconds which is short enough to minimize peripheral thermal damage and long enough to minimize plasma shielding effects to allow efficient ablation at practical rates. The desired pulse duration near 20-μs has been difficult to achieve since it is too long for transverse excited atmospheric pressure (TEA) lasers and too short for radio-frequency (RF) excited lasers for efficient operation. Recently, Coherent Inc. (Santa Clara, CA) developed the Diamond J5-V laser for microvia drilling which can produce laser pulses greater than 100-mJ in energy at 9.4-μm with a pulse duration of 26-μs and it can achieve pulse repetition rates of 3 KHz. We report the first results using this laser to ablate dental enamel. Efficient ablation of dental enamel is possible at rates exceeding 50-μm per pulse. This laser is ideally suited for the selective ablation of carious lesions. PMID:27006521

  7. LOFT experimental measurements uncertainty analyses. Volume XX. Fluid-velocity measurement using pulsed-neutron activation

    SciTech Connect

    Lassahn, G.D.; Taylor, D.J.N.

    1982-08-01

    Analyses of uncertainty components inherent in pulsed-neutron-activation (PNA) measurements in general and the Loss-of-Fluid-Test (LOFT) system in particular are given. Due to the LOFT system's unique conditions, previously-used techniques were modified to make the volocity measurement. These methods render a useful, cost-effective measurement with an estimated uncertainty of 11% of reading.

  8. Instrument for the measurement and determination of chemical pulse column parameters

    DOEpatents

    Marchant, Norman J.; Morgan, John P.

    1990-01-01

    An instrument for monitoring and measuring pneumatic driving force pulse parameters applied to chemical separation pulse columns obtains real time pulse frequency and root mean square amplitude values, calculates column inch values and compares these values against preset limits to alert column operators to the variations of pulse column operational parameters beyond desired limits.

  9. Effects of Treatment Duration and Cooling Rate on Pure Aluminum Solidification Upon Pulse Magneto-Oscillation Treatment

    NASA Astrophysics Data System (ADS)

    Edry, Itzhak; Mordechai, Tomer; Frage, Nachum; Hayun, Shmuel

    2016-03-01

    The effect of pulse magneto-oscillation (PMO) treatment on casting grain size has been widely investigated. Nevertheless, its mechanism remains unclear, especially when PMO is applied at different periods during solidification, namely when only applied above the melting point. In the present work, the effect of PMO treatment applied at different segments during solidification was investigated. It was found that the dendrite fragmentation model may well explain the effect of PMO applied during the dendrite growth stage. However, only the cavities activation model may account for the effect when PMO is conducted above the melting point. In current study, the effect of PMO treatment on grain size was also investigated at various cooling rates. It was established that the cooling rate had only a slight effect on grain size when PMO treatment was applied. Thus, PMO treatment may provide homogeneous grain size distribution in castings with different wall thicknesses that solidified with various cooling rates.

  10. Pulsed remote Raman system for daytime measurements of mineral spectra.

    PubMed

    Misra, Anupam K; Sharma, Shiv K; Chio, Chi Hong; Lucey, Paul G; Lienert, Barry

    2005-08-01

    A remote Raman system has been developed utilizing a 532nm pulsed laser and gated intensified charged couple device (ICCD) detector in the oblique geometry. When the system is set for 50m sample distance it is capable of measuring Raman spectra of minerals located at distances in the range of 10-65m from the telescope. Both daytime and nighttime operations are feasible and the spectra of minerals can be measured in a short period of time, of the order of a few seconds. In oblique geometry, measured sampling depth is more than 30m, during which the system maintains very high performance without any adjustments. Much longer sampling depth (0.1-120m) has been observed when the system is configured in the coaxial geometry. Clear advantages of using a gated detection mode over the continuous (CW) mode of operation in reducing the background signal and eliminating long-lived fluorescence signals from the Raman spectra are presented. The performance of the pulsed Raman system is demonstrated by measuring spectra of Raman standards including benzene (C(6)H(6)) and naphthalene (C(10)H(8)), a low Raman cross section silicate mineral muscovite (KAl(2)(Si(3)Al)O(10)(OH)(2)), and a medium Raman cross section mineral calcite (CaCO(3)). PMID:16029850

  11. Short-duration transient visual evoked potential for objective measurement of refractive errors.

    PubMed

    Anand, Aashish; De Moraes, Carlos Gustavo V; Teng, Christopher C; Liebmann, Jeffrey M; Ritch, Robert; Tello, Celso

    2011-12-01

    This study examined effects of uncorrected refractive errors (RE) in a short-duration transient visual evoked potential (SD t-VEP) system and investigated their role for objective measurement of RE. Refractive errors were induced by means of trial lenses in 35 emmetropic subjects. A synchronized single-channel EEG was recorded for emmetropia, and each simulated refractive state to generate 21 VEP responses for each subject. P100 amplitude (N75 trough to P100 peak) and latency were identified by an automated post-signal processing algorithm. Induced hypermetropia and myopia correlated strongly with both P100 amplitude and latency. To minimize the effect of baseline shift and waveform fluctuations, a VEP scoring system, based on software-derived P100 latency, amplitude and waveform quality, was used to estimate the RE. Using the VEP scores, a single VEP response had a high sensitivity and specificity for discerning emmetropia, small RE (<2 diopter) within a 2 diopter range and large RE (2-14 diopter) within a 4 diopter range. The VEP scoring system has a potential for objective screening of RE and for a more accurate 3-step objective refraction. PMID:21931961

  12. Laser-tissue interaction with fs pulses: measurement of the recoil momentum by laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Sessa, Gaetano; Travaglini, Michele; Mittnacht, Dirk; Foth, Hans-Jochen

    2003-07-01

    Currently ultra short pulses with pluse duration close to 100 fs are investigated for tissue ablation to perform laser surgery in a microscopic scale without any damage to the remaining tissue. Several groups showed already that the risk of thermal damage can be avoided; however the ablated material leaves the surface with a high velocity which leads to significant recoil momentum to the tissue. This paper focuses on the experimental set-up to measure this momentum transfer. Various set-ups had been developd over the last years like a pendulum that is highly senstive but cannot ensure that in a train of pulses each pulse will impact at exactly the same spot. A sliding rod in a glass tube ensured the constant impact point but is sensitive to several environmental conditions, which are hard to control. Recently, special swing plates were designed as vibration disks. The small sample was mounted in the center of this plate and exposed by fs pulses of a TiSa laser. The beam of a laser Doppler vibrometer was focused onto the backside of the plate monitored its motion. This set-up enabled us to measure the recoil momentum. While the total momentum transfer could be well determined to Δp=6 10-3 g mm/s, the question about a mechanical damage, for example for hair cells in the inner ear is much more difficult to answer, since this depends on the time in which the ablated materials leaves the surface. Evaporation times of 40 ps would lead to serious risk ofhar cell damage.

  13. Ultrashort pulse chirp measurement via transverse second-harmonic generation in strontium barium niobate crystal

    SciTech Connect

    Trull, J.; Wang, B.; Parra, A.; Vilaseca, R.; Cojocaru, C.; Sola, I.; Sheng, Y.

    2015-06-01

    Pulse compression in dispersive strontium barium niobate crystal with a random size and distribution of the anti-parallel orientated nonlinear domains is observed via transverse second harmonic generation. The dependence of the transverse width of the second harmonic trace along the propagation direction allows for the determination of the initial chirp and duration of pulses in the femtosecond regime. This technique permits a real-time analysis of the pulse evolution and facilitates fast in-situ correction of pulse chirp acquired in the propagation through an optical system.

  14. Thrust Augmentation Measurements Using a Pulse Detonation Engine Ejector

    NASA Technical Reports Server (NTRS)

    Santoro, Robert J.; Pal, Sibtosh

    2005-01-01

    Results of an experimental effort on pulse detonation driven ejectors are presented and discussed. The experiments were conducted using a pulse detonation engine (PDE)/ejector setup that was specifically designed for the study and operated at frequencies up to 50 Hz. The results of various experiments designed to probe different aspects of the PDE/ejector setup are reported. The baseline PDE was operated using ethylene (C2H4) as the fuel and an oxygen/nitrogen O2 + N2) mixture at an equivalence ratio of one. The PDE only experiments included propellant mixture characterization using a laser absorption technique, high fidelity thrust measurements using an integrated spring-damper system, and shadowgraph imaging of the detonation/shock wave structure emanating from the tube. The baseline PDE thrust measurement results at each desired frequency agree with experimental and modeling results reported in the literature. These PDE setup results were then used as a basis for quantifying thrust augmentation for various PDE/ejector setups with constant diameter ejector tubes and various ejector lengths, the radius of curvature for the ejector inlets and various detonation tube/ejector tube overlap distances. For the studied experimental matrix, the results showed a maximum thrust augmentation of 106% at an operational frequency of 30 Hz. The thrust augmentation results are complemented by shadowgraph imaging of the flowfield in the ejector tube inlet area and high frequency pressure transducer measurements along the length of the ejector tube.

  15. Thrust Augmentation Measurements for a Pulse Detonation Engine Driven Ejector

    NASA Technical Reports Server (NTRS)

    Pal, S.; Santoro, Robert J.; Shehadeh, R.; Saretto, S.; Lee, S.-Y.

    2005-01-01

    Thrust augmentation results of an ongoing study of pulse detonation engine driven ejectors are presented and discussed. The experiments were conducted using a pulse detonation engine (PDE) setup with various ejector configurations. The PDE used in these experiments utilizes ethylene (C2H4) as the fuel, and an equi-molar mixture of oxygen and nitrogen as the oxidizer at an equivalence ratio of one. High fidelity thrust measurements were made using an integrated spring damper system. The baseline thrust of the PDE engine was first measured and agrees with experimental and modeling results found in the literature. Thrust augmentation measurements were then made for constant diameter ejectors. The parameter space for the study included ejector length, PDE tube exit to ejector tube inlet overlap distance, and straight versus rounded ejector inlets. The relationship between the thrust augmentation results and various physical phenomena is described. To further understand the flow dynamics, shadow graph images of the exiting shock wave front from the PDE were also made. For the studied parameter space, the results showed a maximum augmentation of 40%. Further increase in augmentation is possible if the geometry of the ejector is tailored, a topic currently studied by numerous groups in the field.

  16. Effects of adsorbed proteins, an antifouling agent and long-duration DC voltage pulses on the impedance of silicon-based neural microelectrodes.

    PubMed

    Sommakia, Salah; Rickus, Jenna L; Otto, Kevin J

    2009-01-01

    The successful use of implantable neural microelectrodes as neuroprosthetic devices depends on the mitigation of the reactive tissue response of the brain. One of the factors affecting the ultimate severity of the reactive tissue response and the in vivo electrical properties of the microelectrodes is the initial adsorption of proteins onto the surface of the implanted microelectrodes. In this study we quantify the increase in microelectrode impedance magnitude at physiological frequencies following electrode immersion in a 10% bovine serum albumin (BSA) solution. We also demonstrate the efficacy of a common antifouling molecule, poly(ethylene glycol) (PEG), in preventing a significant increase in microelectrode impedance. In addition, we show the feasibility of using long-duration DC voltage pulses to remove adsorbed proteins from the microelectrode surface. PMID:19963693

  17. Cross-correlation measurement of femtosecond hard x-ray pulses from a laser plasma source: approaching 100 fs benchmark

    NASA Astrophysics Data System (ADS)

    Iqbal, Mazhar; Ijaz, M.; Stiel, H.; Noh, D. Y.; Janulewicz, K. A.

    2015-09-01

    Extremely fast processes happening on sub picosecond time scale can be captured by the well-known pump-probe scheme using ultrashort x-ray pulses as shutter. XFELs and femtosecond slicing beam lines on synchrotrons together-with ultra-short laser driven plasma x-ray sources (LPXs) as an attractive supplement offer exceptional parameters to unleash ultra-fast phenomenon. As pump-probe techniques based on the compact LPXs attract attention being jitter free, more precise knowledge of their emission duration, determining the measurement temporal resolution, became indispensable. We report here, for the first time, x-ray pulse duration from LPX using NIR pump x-ray probe cross-correlation method. The underlying mechanism is ultrafast relaxation of femtosecond laser-induced non-thermal electrons generated on the surface of transition metals. The emission duration of x-ray pulse is estimated by the evolution of transmission (110 +/-6 fs) and fluorescence signals (129 +/- 19 fs) and found in good agreement with the theoretical prediction of <=100 fs for LPXs.

  18. Thrust Measurements for a Pulse Detonation Engine Driven Ejector

    NASA Technical Reports Server (NTRS)

    Santoro, Robert J.; Pak, Sibtosh; Shehadeh, R.; Saretto, S. R.; Lee, S.-Y.

    2005-01-01

    Results of an experimental effort on pulse detonation driven ejectors aimed at probing different aspects of PDE ejector processes, are presented and discussed. The PDE was operated using ethylene as the fuel and an equimolar oxygen/nitrogen mixture as the oxidizer at an equivalence ratio of one. The thrust measurements for the PDE alone are in excellent agreement with experimental and modeling results reported in the literature and serve as a Baseline for the ejector studies. These thrust measurements were then used as a basis for quantifying thrust augmentation for various PDE/ejector setups using constant diameter ejector tubes and various detonation tube/ejector tube overlap distances. The results show that for the geometries studied here, a maximum thrust augmentation of 24% is achieved. The thrust augmentation results are complemented by shadowgraph imaging of the flowfield in the ejector tube inlet area and high frequency pressure transducer measurements along the length of the ejector tube.

  19. Direct thrust force measurement of pulse detonation engine

    NASA Astrophysics Data System (ADS)

    Wahid, Mazlan Abdul; Faiz, M. Z. Ahmad; Saqr, Khalid M.

    2012-06-01

    In this paper we present the result of High-Speed Reacting Flow Laboratory (HiREF) pulse detonation engine (PDE) experimental study on direct thrust measurement. The thrust force generated by the repetitive detonation from a 50 mm inner diameter and 600 mm length tube was directly measured using load cell. Shchelkin spiral was used as an accelerator for the Deflagration to Detonation Transition (DDT) phenomenon. Propane-oxygen at stoichiometric condition was used as the combustible fuel-air mixture for the PDE. The PDE was operated at the operation frequency of 3Hz during the test. The amount of thrust force that was measured during the test reaching up to 70N. These values of thrust force were found to be fluctuating and its combustion phenomenon has been analyzed and discussed.

  20. Paramagnetic metal ions in pulsed ESR distance distribution measurements.

    PubMed

    Ji, Ming; Ruthstein, Sharon; Saxena, Sunil

    2014-02-18

    The use of pulsed electron spin resonance (ESR) to measure interspin distance distributions has advanced biophysical research. The three major techniques that use pulsed ESR are relaxation rate based distance measurements, double quantum coherence (DQC), and double electron electron resonance (DEER). Among these methods, the DEER technique has become particularly popular largely because it is easy to implement on commercial instruments and because programs are available to analyze experimental data. Researchers have widely used DEER to measure the structure and conformational dynamics of molecules labeled with the methanethiosulfonate spin label (MTSSL). Recently, researchers have exploited endogenously bound paramagnetic metal ions as spin probes as a way to determine structural constraints in metalloproteins. In this context Cu(2+) has served as a useful paramagnetic metal probe at X-band for DEER based distance measurements. Sample preparation is simple, and a coordinated-Cu(2+) ion offers limited spatial flexibility, making it an attractive probe for DEER experiments. On the other hand, Cu(2+) has a broad absorption ESR spectrum at low temperature, which leads to two potential complications. First, the Cu(2+)-based DEER time domain data has lower signal to noise ratio compared with MTSSL. Second, accurate distance distribution analysis often requires high-quality experimental data at different external magnetic fields or with different frequency offsets. In this Account, we summarize characteristics of Cu(2+)-based DEER distance distribution measurements and data analysis methods. We highlight a novel application of such measurements in a protein-DNA complex to identify the metal ion binding site and to elucidate its chemical mechanism of function. We also survey the progress of research on other metal ions in high frequency DEER experiments. PMID:24289139

  1. Nonperturbative measurement of the local magnetic field using pulsed polarimetry for fusion reactor conditions (invited)a)

    NASA Astrophysics Data System (ADS)

    Smith, Roger J.

    2008-10-01

    A novel diagnostic technique for the remote and nonperturbative sensing of the local magnetic field in reactor relevant plasmas is presented. Pulsed polarimetry [Patent No. 12/150,169 (pending)] combines optical scattering with the Faraday effect. The polarimetric light detection and ranging (LIDAR)-like diagnostic has the potential to be a local Bpol diagnostic on ITER and can achieve spatial resolutions of millimeters on high energy density (HED) plasmas using existing lasers. The pulsed polarimetry method is based on nonlocal measurements and subtle effects are introduced that are not present in either cw polarimetry or Thomson scattering LIDAR. Important features include the capability of simultaneously measuring local Te, ne, and B∥ along the line of sight, a resiliency to refractive effects, a short measurement duration providing near instantaneous data in time, and location for real-time feedback and control of magnetohydrodynamic (MHD) instabilities and the realization of a widely applicable internal magnetic field diagnostic for the magnetic fusion energy program. The technique improves for higher neB∥ product and higher ne and is well suited for diagnosing the transient plasmas in the HED program. Larger devices such as ITER and DEMO are also better suited to the technique, allowing longer pulse lengths and thereby relaxing key technology constraints making pulsed polarimetry a valuable asset for next step devices. The pulsed polarimetry technique is clarified by way of illustration on the ITER tokamak and plasmas within the magnetized target fusion program within present technological means.

  2. Unsteady thrust measurement techniques for pulse detonation engines

    NASA Astrophysics Data System (ADS)

    Joshi, Dibesh Dhoj

    Thrust is a critical performance parameter and its correct determination is necessary to characterize an engine. Many conventional thrust measurement techniques prevail. However, further developments are required for correct measurement of thrust in the case of a pulse detonation engine (PDE), since the entire thrust generation process is intermittent. The significant effect of system dynamics in the form of inertial forces, stress wave propagation and reflections initiated in the structure due to detonations and pulse-to-pulse interaction in a fast operating PDE further complicate the thrust measurement process. These complications call for a further, detailed study of the unsteady thrust characteristics. A general approach was first developed to recover actual thrust from the measured thrust generated by the PDE. The developed approach consisted of two steps. The first step incorporated a deconvolution procedure using a pre-established system transfer function and measured input to reconstruct the output yielding the deconvolved thrust. The second step accounted for inertial forces through an acceleration compensation procedure. These two steps allowed the actual thrust to be determined. A small scale PDE operating at 10 and 20 Hz with varied filling fractions and mixture equivalence ratios was used for the experimental application of the general approach. The analytical study of gas dynamics in the PDE while in operation and the measured pressure histories at the exit of the engine allowed the generated thrust during a cycle to be determined semi-empirically. The thrust values determined semi-empirically were compared against the experimental results. A dynamical model of the PDE was created for the study of the unsteady thrust characteristics using finite element analysis. The results from finite element analysis were compared against semi-empirical and experimental results. In addition, finite element analysis also facilitated to numerically determine the

  3. The effects of optical scattering on pulsed photoacoustic measurement in weakly absorbing liquids

    NASA Astrophysics Data System (ADS)

    Zhao, Zuomin; Myllylä, Risto

    2001-12-01

    In this article, a photoacoustic technique, excited by a pulsed diode laser, is used in a study of optically absorbing and scattering liquids. The article discusses the effects of optical scattering on the photoacoustic source and signal. In the empirical part, varying amounts of milk and carbon powder were added to water to control the absorption and scattering coefficients of the resulting liquids. The results showed that scattering increases the duration of the photoacoustic signal while decreasing the signal amplitude to some degree. This paper also shows a quite simple method for measuring the scattering coefficient in weakly absorbing materials using a PZT transducer, which can be used to determine the concentration of highly scattering compositions in some cases.

  4. Leaf wetness duration measurement: comparison of cylindrical and flat plate sensors under different field conditons

    NASA Astrophysics Data System (ADS)

    Sentelhas, Paulo C.; Gillespie, Terry J.; Santos, Eduardo A.

    2007-03-01

    In general, leaf wetness duration (LWD) is a key parameter influencing plant disease epidemiology, since it provides the free water required by pathogens to infect foliar tissue. LWD is used as an input in many disease warning systems, which help growers to decide the best time to spray their crops against diseases. Since there is no observation standard either for sensor or exposure, LWD measurement is often problematic. To assess the performance of electronic sensors, LWD measurements obtained with painted cylindrical and flat plate sensors were compared under different field conditions in Elora, Ontario, Canada, and in Piracicaba, São Paulo, Brazil. The sensors were tested in four different crop environments—mowed turfgrass, maize, soybean, and tomatoes—during the summer of 2003 and 2004 in Elora and during the winter of 2005 in Piracicaba. Flat plate sensors were deployed facing north and at 45° to horizontal, and cylindrical sensors were deployed horizontally. At the turfgrass site, both sensors were installed 30 cm above the ground, while at the crop fields, the sensors were installed at the top and inside the canopy (except for maize, with a sensor only at the top). Considering the flat plate sensor as a reference (Sentelhas et al. Operational exposure of leaf wetness sensors. Agric For Meteorol 126:59-72, 2004a), the results in the more humid climate at Elora showed that the cylindrical sensor overestimated LWD by 1.1-4.2 h, depending on the crop and canopy position. The main cause of the overestimation was the accumulation of big water drops along the bottom of the cylindrical sensors, which required much more energy and, consequently, time to evaporate. The overall difference between sensors when evaporating wetness formed during the night was around 1.6 h. Cylindrical sensors also detected wetness earlier than did flat plates—around 0.6 h. Agreement between plate and cylinder sensors was much better in the drier climate at Piracicaba. These

  5. Hybrid femtosecond/picosecond rotational coherent anti-Stokes Raman scattering temperature and concentration measurements using two different picosecond-duration probes.

    PubMed

    Kearney, Sean P; Scoglietti, Daniel J; Kliewer, Christopher J

    2013-05-20

    A hybrid fs/ps pure-rotational CARS scheme is characterized in furnace-heated air at temperatures from 290 to 800 K. Impulsive femtosecond excitation is used to prepare a rotational Raman coherence that is probed with a ps-duration beam generated from an initially broadband fs pulse that is bandwidth limited using air-spaced Fabry-Perot etalons. CARS spectra are generated using 1.5- and 7.0-ps duration probe beams with corresponding coarse and narrow spectral widths. The spectra are fitted using a simple phenomenological model for both shot-averaged and single-shot measurements of temperature and oxygen mole fraction. Our single-shot temperature measurements exhibit high levels of precision and accuracy when the spectrally coarse 1.5-ps probe beam is used, demonstrating that high spectral resolution is not required for thermometry. An initial assessment of concentration measurements in air is also provided, with best results obtained using the higher resolution 7.0-ps probe. This systematic assessment of the hybrid CARS technique demonstrates its utility for practical application in low-temperature gas-phase systems. PMID:23736451

  6. Water depth measurement using an airborne pulsed neon laser system

    SciTech Connect

    Hoge, F.E.; Swift, R.N.; Frederick, E.B.

    1980-03-15

    Initial base-line field test performance results of the National Aeronautics and Space Administration's airborne oceanographic lidar (AOL) in the bathymetry mode are presented. Flight tests over the Atlantic Ocean yielded water depth measurements to 10 m. Water depths to 4.6 m were measured in the more turbid Chesapeake Bay. Water-truth measurements of depth and beam attenuation coefficients by boat were taken at the same time as the air craft overflights to aid in determining the system's operational performance. Beam attenuation coefficient and depth d product d was established early in the program as the performance criterion index. A performance product of 6 was determined to be the goal. This performance goal was successfully met or exceeded in the large number of field tests executed. Included are selected data from nadir-angle tests conducted at 0, 5, 10, and 15. Field-of-view data chosen from the 2-, 5-, 10-, and 20-mrad tests are also presented. Depth measurements obtained to altitudes of 456 m are given for additional comparison. This laser bathymetry system represents a significant improvement over prior models in that (1) the complete surface-to-bottom pulse waveform is digitally recorded on magnetic tape at a rate of 400 pulse waveforms/sec, and (2) wide-swath mapping data may be routinely acquired using the 30 full-angle conical scanner. Space does not allow all the 5,000,000 laser soundings to be included. Qualified interested users may obtain complete data sets for their own in-depth analysis. 15 references, 9 figures, 1 table.

  7. iPad-Assisted Measurements of Duration Estimation in Psychiatric Patients and Healthy Control Subjects

    PubMed Central

    Preuschoff, Irene; Müller, Helge H.; Sperling, Wolfgang; Biermann, Teresa; Bergner, Matthias; Kornhuber, Johannes; Groemer, Teja W.

    2013-01-01

    Handheld devices with touchscreen controls have become widespread in the general population. In this study, we examined the duration estimates (explicit timing) made by patients in a major general hospital and healthy control subjects using a custom iPad application. We methodically assessed duration estimates using this novel device. We found that both psychiatric and non-psychiatric patients significantly overestimated time periods compared with healthy control subjects, who estimated elapsed time very precisely. The use of touchscreen-based methodologies can provide valuable information about patients. PMID:23658689

  8. Substrate heating measurements in pulsed ion beam film deposition

    SciTech Connect

    Olson, J.C.; Davis, H.A.; Rej, D.J.; Waganaar, W.J.; Tallant, D.R.; Thompson, M.O.

    1995-05-01

    Diamond-like Carbon (DLC) films have been deposited at Los Alamos National Laboratory by pulsed ion beam ablation of graphite targets. The targets were illuminated by an intense beam of hydrogen, carbon, and oxygen ions at a fluence of 15-45 J/cm{sup 2}. Ion energies were on the order of 350 keV, with beam current rising to 35 kA over a 400 ns ion current pulse. Raman spectra of the deposited films indicate an increasing ratio of sp{sup 3} to sp{sup 2} bonding as the substrate is moved further away from the target and further off the target normal. Using a thin film platinum resistor at varying positions, we have measured the heating of the substrate surface due to the kinetic energy and heat of condensation of the ablated material. This information is used to determine if substrate heating is responsible for the lack of DLC in positions close to the target and near the target normal. Latest data and analysis will be presented.

  9. Spatial corrections for pulsed-neutron reactivity measurements.

    SciTech Connect

    Cao, Y.; Lee, J.; Nuclear Engineering Division; Univ. of Michigan

    2010-07-01

    For pulsed-neutron experiments performed in a subcritical reactor, the reactivity obtained from the area-ratio method is sensitive to detector positions. The spatial effects are induced by the presence of both the prompt neutron harmonics and the delayed neutron harmonics in the reactor. The traditional kinetics distortion factor is only limited to correcting the spatial effects caused by the fundamental prompt-{alpha} mode. In this paper, we derive spatial correction factors fp and fd to account for spatial effects induced by the prompt neutron harmonics and the delayed neutron harmonics, respectively. Our numerical simulations with the FX2-TH time-dependent multigroup diffusion code indicate that the high-order prompt neutron harmonics lead to significant spatial effects and cannot be neglected in calculating the spatial correction factors. The prompt spatial correction factor fp can be simply determined by the ratio of the normalized detector responses corresponding to the fundamental k-mode and the prompt neutron flux integrated over the pulse period. Thus, it is convenient to calculate and provides physically intuitive explanations on the spatial dependence of reactivity measured in the MUSE-4 experiments: overestimation of the subcriticality in regions close to the external neutron source and underestimation of the subcriticality away from the source but within the fuel region.

  10. High pulse repetition frequency, multiple wavelength, pulsed CO(2) lidar system for atmospheric transmission and target reflectance measurements.

    PubMed

    Ben-David, A; Emery, S L; Gotoff, S W; D'Amico, F M

    1992-07-20

    A multiple wavelength, pulsed CO(2) lidar system operating at a pulse repetition frequency of 200 Hz and permitting the random selection of CO(2) laser wavelengths for each laser pulse is presented. This system was employed to measure target reflectance and atmospheric transmission by using laser pulse bursts consisting of groups with as many as 16 different wavelengths at a repetition rate of 12 Hz. The wavelength tuning mechanism of the transversely excited atmospheric laser consists of a stationary grating and a flat mirror controlled by a galvanometer. Multiple wavelength, differential absorption lidar (DIAL) measurements reduce the effects of differential target reflectance and molecular absorption interference. Examples of multiwavelength DIAL detection for ammonia and water vapor show the dynamic interaction between these two trace gases. Target reflectance measurements for maple trees in winter and autumn are presented. PMID:20725406

  11. Novel Techniques for Pulsed Field Gradient NMR Measurements

    NASA Astrophysics Data System (ADS)

    Brey, William Wallace

    Pulsed field gradient (PFG) techniques now find application in multiple quantum filtering and diffusion experiments as well as in magnetic resonance imaging and spatially selective spectroscopy. Conventionally, the gradient fields are produced by azimuthal and longitudinal currents on the surfaces of one or two cylinders. Using a series of planar units consisting of azimuthal and radial current elements spaced along the longitudinal axis, we have designed gradient coils having linear regions that extend axially nearly to the ends of the coil and to more than 80% of the inner radius. These designs locate the current return paths on a concentric cylinder, so the coils are called Concentric Return Path (CRP) coils. Coils having extended linear regions can be made smaller for a given sample size. Among the advantages that can accrue from using smaller coils are improved gradient strength and switching time, reduced eddy currents in the absence of shielding, and improved use of bore space. We used an approximation technique to predict the remaining eddy currents and a time-domain model of coil performance to simulate the electrical performance of the CRP coil and several reduced volume coils of more conventional design. One of the conventional coils was designed based on the time-domain performance model. A single-point acquisition technique was developed to measure the remaining eddy currents of the reduced volume coils. Adaptive sampling increases the dynamic range of the measurement. Measuring only the center of the stimulated echo removes chemical shift and B_0 inhomogeneity effects. The technique was also used to design an inverse filter to remove the eddy current effects in a larger coil set. We added pulsed field gradient and imaging capability to a 7 T commercial spectrometer to perform neuroscience and embryology research and used it in preliminary studies of binary liquid mixtures separating near a critical point. These techniques and coil designs will find

  12. Use of Minute-by-Minute Cardiovascular Measurements During Tilt Tests to Strengthen Inference on the Effect of Long-Duration Space Flight on Orthostatic Hypotension

    NASA Technical Reports Server (NTRS)

    Feiveson, Alan H.; Lee, Stuart M. C.; Stenger, Michael B.; Stein, Sydney P.; Platts, Steven H.

    2011-01-01

    Typical methodology for evaluating the effects of spaceflight on orthostatic hypotension (OH) has been survival analysis of tolerance times from 80 head-up tilt tests. However when scheduled test durations are short, there may not be enough failures to allow survival analysis to adequately estimate and compare the effects of flight phase (e.g. pre-flight, number of days post-flight), flight duration, and their interaction, as well as interactions with effects of interventions or countermeasures. The problem is exacerbated in the presence of a repeated measures design, in which subjects participate in tilt tests during various flight phases. Here we show how it is possible to dramatically improve the efficiency of statistical inference in this setting by making use of the additional information contained in minute-by-minute observations of cardiovascular parameters thought to be reflective of progression towards presyncope during tilt testing. Methods: We retrospectively examined operational tilt test (OTT; 10 -min 80 head-up tilt) data from 20 International Space Station (ISS) and 66 Shuttle astronauts 10 d before launch (L-10), on landing day (R+0) and during recovery (R+1, R+3, R+6-10) depending on the level of participation. Data from 5 ISS astronauts tested on R+0 or R+1 who used non-standard countermeasures were excluded. In addition to OTT survival time, 8 cardiovascular parameters (CP: heart rate, systolic, diastolic, and mean arterial blood pressure, pulse pressure, stroke volume, cardiac output, and total peripheral resistance) that might be predictive of progression towards presyncope were measured every minute of each OTT. Statistical analysis was predicated on a two ]stage model of causation. In the first stage, flight duration and time from landing affect the astronauts' degree of OH, which is manifested in the time trends and variation of the above CPs during OTTs. In the second stage, the behavior of these parameters directly affects OTT survival

  13. Pulsed electro-acoustic (PEA) measurements of embedded charge distributions

    NASA Astrophysics Data System (ADS)

    Dennison, J. R.; Pearson, Lee H.

    2013-09-01

    Knowledge of the spatial distribution and evolution of embedded charge in thin dielectric materials has important applications in semiconductor, high-power electronic device, high-voltage DC power cable insulation, high-energy and plasma physics apparatus, and spacecraft industries. Knowing how, where, and how much charge accumulates and how it redistributes and dissipates can predict destructive charging effects. Pulsed Electro-acoustic (PEA) measurements— and two closely related methods, Pressure Wave Propagation (PWP) and Laser Intensity Modulation (LIMM)— nondestructively probe such internal charge distributions. We review the instrumentation, methods, theory and signal processing of simple PEA experiments, as well as the related PPW and LIMM methods. We emphasize system improvements required to achieve high spatial resolution for in vacuo measurements of thin dielectrics charged using electron beam injection.

  14. Breath holding duration as a measure of distress tolerance: examining its relation to measures of executive control.

    PubMed

    Sütterlin, Stefan; Schroijen, Mathias; Constantinou, Elena; Smets, Elyn; Van den Bergh, Omer; Van Diest, Ilse

    2013-01-01

    Recent research considers distress (in)tolerance as an essential component in the development of various forms of psychopathology. A behavioral task frequently used to assess distress tolerance is the breath holding task. Although breath holding time (BHT) has been associated with behavioral outcomes related to inhibitory control (e.g., smoking cessation), the relationship among breath holding and direct measures of executive control has not yet been thoroughly examined. The present study aims to assess (a) the BHT-task's test-retest reliability in a 1-year follow-up and (b) the relationship between a series of executive function tasks and breath holding duration. One hundred and thirteen students completed an initial BHT assessment, 58 of which also completed a series of executive function tasks [the Wisconsin Card Sorting Test (WCST), the Parametric Go/No-Go task and the N-back memory updating task]. A subsample of these students (N = 34) repeated the breath holding task in a second session 1 year later. Test-retest reliability of the BHT-task over a 1-year period was high (r = 0.67, p < 0.001), but none of the executive function tasks was significantly associated with BHT. The rather moderate levels of unpleasantness induced by breath holding in our sample may suggest that other processes (physiological, motivational) besides distress tolerance influence BHT. Overall, the current findings do not support the assumption of active inhibitory control in the BHT-task in a healthy sample. Our findings suggest that individual differences (e.g., in interoceptive or anxiety sensitivity) should be taken into account when examining the validity of BHT as a measure of distress tolerance. PMID:23908639

  15. Multiscale analysis: a way to investigate laser damage precursors in materials for high power applications at nanosecond pulse duration

    NASA Astrophysics Data System (ADS)

    Natoli, J. Y.; Wagner, F.; Ciapponi, A.; Capoulade, J.; Gallais, L.; Commandré, M.

    2010-11-01

    The mechanism of laser induced damage in optical materials under high power nanosecond laser irradiation is commonly attributed to the presence of precursor centers. Depending on material and laser source, the precursors could have different origins. Some of them are clearly extrinsic, such as impurities or structural defects linked to the fabrication conditions. In most cases the center size ranging from sub-micrometer to nanometer scale does not permit an easy detection by optical techniques before irradiation. Most often, only a post mortem observation of optics permits to proof the local origin of breakdown. Multi-scale analyzes by changing irradiation beam size have been performed to investigate the density, size and nature of laser damage precursors. Destructive methods such as raster scan, laser damage probability plot and morphology studies permit to deduce the precursor densities. Another experimental way to get information on nature of precursors is to use non destructive methods such as photoluminescence and absorption measurements. The destructive and non destructive multiscale studies are also motivated for practical reasons. Indeed LIDT studies of large optics as those used in LMJ or NIF projects are commonly performed on small samples and with table top lasers whose characteristics change from one to another. In these conditions, it is necessary to know exactly the influence of the different experimental parameters and overall the spot size effect on the final data. In this paper, we present recent developments in multiscale characterization and results obtained on optical coatings (surface case) and KDP crystal (bulk case).

  16. Synchronized ps fiber lasers with pulse durations (25, 50, 100-2000ps) and repetition rates (100kHz-150Mhz) continuously tunable over three orders of magnitude

    NASA Astrophysics Data System (ADS)

    Dupuis, Alexandre; Burgoyne, Bryan; Pena, Guido; Archambault, André; Lemieux, Dominic; Solomonean, Vasile; Duong, Maxime; Villeneuve, Alain

    2013-03-01

    Ultrafast lasers are enabling precision machining of a wide variety of materials. However, the optimal laser parameters for proper material processing can differ greatly from one material to another. In order to cut high aspect-ratio features at high processing speeds the laser parameters such as pulse energy, repetition rate, and cutting speed need to be optimized. In particular, a shorter pulse duration plays an important role in reducing the thermal damage in the Heat-Affected Zones. In this paper we present a novel ps fiber laser whose electronically tunable parameters aim to facilitate the search for optimal processing parameters. The 20W 1064nm Yb fiber laser is based on a Master Oscillator Power Amplifier (MOPA) architecture with a repetition rate that can be tuned continuously from 120kHz to 120MHz. More importantly, the integration of three different pulse generators enables the pulse duration to be switched from 25ps to 50ps, or to any value within the 55ps to 2000ps range. By reducing the pulse duration from the ns-regime down to 25ps, the laser approaches the transition from the thermal processing regime to the ablation regime of most materials. Moreover, in this paper we demonstrate the synchronization of the pulses from two such MOPA lasers. This enables more elaborate multipulse processing schemes where the pulses of each laser can be set to different parameter values, such as an initial etching pulse followed by a thermal annealing pulse. It should be noted that all the laser parameters are controlled electronically with no moving parts, including the synchronization.

  17. Autocorrelation measurement of femtosecond laser pulses based on two-photon absorption in GaP photodiode

    SciTech Connect

    Chong, E. Z.; Watson, T. F.; Festy, F.

    2014-08-11

    Semiconductor materials which exhibit two-photon absorption characteristic within a spectral region of interest can be useful in building an ultra-compact interferometric autocorrelator. In this paper, we report on the evidence of a nonlinear absorption process in GaP photodiodes which was exploited to measure the temporal profile of femtosecond Ti:sapphire laser pulses with a tunable peak wavelength above 680 nm. The two-photon mediated conductivity measurements were performed at an average laser power of less than a few tenths of milliwatts. Its suitability as a single detector in a broadband autocorrelator setup was assessed by investigating the nonlinear spectral sensitivity bandwidth of a GaP photodiode. The highly favourable nonlinear response was found to cover the entire tuning range of our Ti:sapphire laser and can potentially be extended to wavelengths below 680 nm. We also demonstrated the flexibility of GaP in determining the optimum compensation value of the group delay dispersion required to restore the positively chirped pulses inherent in our experimental optical system to the shortest pulse width possible. With the rise in the popularity of nonlinear microscopy, the broad two-photon response of GaP and the simplicity of this technique can provide an alternative way of measuring the excitation laser pulse duration at the focal point of any microscopy systems.

  18. A large shock vein in L chondrite Roosevelt County 106: Evidence for a long-duration shock pulse on the L chondrite parent body

    NASA Astrophysics Data System (ADS)

    Sharp, Thomas G.; Xie, Zhidong; de Carli, Paul S.; Hu, Jinping

    2015-11-01

    A large shock-induced melt vein in L6 ordinary chondrite Roosevelt County 106 contains abundant high-pressure minerals, including olivine, enstatite, and plagioclase fragments that have been transformed to polycrystalline ringwoodite, majorite, lingunite, and jadeite. The host chondrite at the melt-vein margins contains olivines that are partially transformed to ringwoodite. The quenched silicate melt in the shock veins consists of majoritic garnets, up to 25 μm in size, magnetite, maghemite, and phyllosilicates. The magnetite, maghemite, and phyllosilicates are the terrestrial alteration products of magnesiowüstite and quenched glass. This assemblage indicates crystallization of the silicate melt at approximately 20-25 GPa and 2000 °C. Coarse majorite garnets in the centers of shock veins grade into increasingly finer grained dendritic garnets toward the vein margins, indicating increasing quench rates toward the margins as a result of thermal conduction to the surrounding chondrite host. Nanocrystalline boundary zones, that contain wadsleyite, ringwoodite, majorite, and magnesiowüstite, occur along shock-vein margins. These zones represent rapid quench of a boundary melt that contains less metal-sulfide than the bulk shock vein. One-dimensional finite element heat-flow calculations were performed to estimate a quench time of 750-1900 ms for a 1.6-mm thick shock vein. Because the vein crystallized as a single high-pressure assemblage, the shock pulse duration was at least as long as the quench time and therefore the sample remained at 20-25 GPa for at least 750 ms. This relatively long shock pulse, combined with a modest shock pressure, implies that this sample came from deep in the L chondrite parent body during a collision with a large impacting body, such as the impact event that disrupted the L chondrite parent body 470 Myr ago.

  19. Two-pulse rapid remote surface contamination measurement.

    SciTech Connect

    Headrick, Jeffrey M.; Kulp, Thomas J.; Bisson, Scott E.; Reichardt, Thomas A.; Farrow, Roger L.

    2010-11-01

    This project demonstrated the feasibility of a 'pump-probe' optical detection method for standoff sensing of chemicals on surfaces. Such a measurement uses two optical pulses - one to remove the analyte (or a fragment of it) from the surface and the second to sense the removed material. As a particular example, this project targeted photofragmentation laser-induced fluorescence (PF-LIF) to detect of surface deposits of low-volatility chemical warfare agents (LVAs). Feasibility was demonstrated for four agent surrogates on eight realistic surfaces. Its sensitivity was established for measurements on concrete and aluminum. Extrapolations were made to demonstrate relevance to the needs of outside users. Several aspects of the surface PF-LIF physical mechanism were investigated and compared to that of vapor-phase measurements. The use of PF-LIF as a rapid screening tool to 'cue' more specific sensors was recommended. Its sensitivity was compared to that of Raman spectroscopy, which is both a potential 'confirmer' of PF-LIF 'hits' and is also a competing screening technology.

  20. Pulse

    MedlinePlus

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

  1. Measuring the intensity and phase of two ultrashort pulses on a single shot

    SciTech Connect

    DeLong, K.W.; Trebino, R.

    1994-12-31

    The method of Frequency-Resolved Optical Gating (FROG) allows one to measure the amplitude and phase of an arbitrary femtosecond pulse on a single laser shot. An extension of this method, which they call Twin Recovery of Excitation E-fields using FROG (TREEFROG) allows one to measure two separate laser pulses. The two dissimilar pulses are used to generate a single ``TREEFROG trace`` from a simple experimental apparatus, and the two pulse electric fields are determined using a modified FROG pulse-retrieval algorithm.

  2. Unstable multipulsing can be invisible to some ultrashort pulse measurement techniques

    NASA Astrophysics Data System (ADS)

    Rhodes, Michelle; Guang, Zhe; Trebino, Rick

    2016-03-01

    Multiple pulsing is a feature of most mode-locked ultrafast laser systems at very high pump powers, and slight variations in the pump power around certain regimes can cause sinusoidally-varying or even chaotic separations among pulses. The impact of this type of unstable multipulsing on modern pulse measurement methods has not been studied. We have performed calculations and simulations and find that allowing only the relative phase of a satellite pulse to vary causes the satellite to wash out of the SPIDER measurement completely. Although techniques like FROG and autocorrelation cannot accurately determine the precise properties of satellite pulses, they do succeed in seeing them.

  3. The effect of laser pulse duration and beam shape on the selective removal of novel thin film layers for flexible electronic devices

    NASA Astrophysics Data System (ADS)

    Moorhouse, C.; Karnakis, D. M.; Kapnopoulos, C.; Laskarakis, A.; Logothetidis, S.; Antonopoulos, G.; Mekeridis, E.

    2015-07-01

    Lightweight, flexible substrates coated with thin film layers <0.5μm thick are commonly utilized for modern electronic devices that are portable and constantly reducing in size, weight, power consumption and material cost. Patterning techniques for these thin films are required to provide device functionality and alternatives to photolithography such as direct write laser processes are particularly attractive. However, for complex devices with multiple thin layers, the quality requirements for laser scribing are extremely high, since each individual thin film layer must be patterned without damaging the underlying thin film layer(s) and also provide a suitable topography for subsequent layers to be deposited upon. Hence, the choice of the laser parameters is critical for a number of emerging thin film materials used in flexible electronic devices such as ITO, pedot:PSS, silver nanoparticle inks, amongst others. These thin films can be extremely sensitive to the thermal interaction with lasers and this report outlines the influence of laser pulse duration and beam shaping techniques on laser patterning of these thin films and the implications for laser system design.

  4. Coaxial-type water load for measuring high voltage, high current and short pulse of a compact Marx system for a high power microwave source

    NASA Astrophysics Data System (ADS)

    Han, Jaeeun; Kim, Jung-ho; Park, Sang-duck; Yoon, Moohyun; Park, Soo Yong; Choi, Do Won; Shin, Jin Woo; So, Joon Ho

    2009-11-01

    A coaxial-type water load was used to measure the voltage output from a Marx generator for a high power microwave source. This output had a rise time of 20 ns, a pulse duration of a few hundred ns, and an amplitude up to 500 kV. The design of the coaxial water load showed that it is an ideal resistive divider and can also accurately measure a short pulse. Experiments were performed to test the performance of the Marx generator with the calibrated coaxial water load.

  5. Invariance to Rotation in Depth Measured by Masked Repetition Priming is Dependent on Prime Duration

    PubMed Central

    Eddy, Marianna D.; Holcomb, Phillip J.

    2011-01-01

    The current experiment examined invariance to pictures of objects rotated in depth using event-related potentials (ERPs) and masked repetition priming. Specifically we rotated objects 30°, 60° or 150° from their canonical view and, across two experiments, varied the prime duration (50 or 90 milliseconds (ms)). We examined three ERP components, the P/N190, N300 and N400. In Experiment 1, only the 30° rotation condition produced repetition priming effects on the N/P190, N300 and N400. The other rotation conditions only showed repetition priming effects on the early perceptual component, the N/P190. Experiment 2 extended the prime duration to 90 ms to determine whether additional exposure to the prime may produce invariance on the N300 and N400 for the 60° and 150° rotation conditions. Repetition priming effects were found for all rotation conditions across the N/P190, N300 and N400 components. We interpret these results to suggest that whether or not view invariant priming effects are found depends partly on the extent to which representation of an object has been activated. PMID:22005687

  6. Airborne 2-Micron Double Pulsed Direct Detection IPDA Lidar for Atmospheric CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Reithmaier, Karl; Remus, Ruben; Singh, Upendra; Johnson, Will; Boyer, Charlie; Fay, James; Johnston, Susan; Murchison, Luke

    2015-01-01

    An airborne 2-micron double-pulsed Integrated Path Differential Absorption (IPDA) lidar has been developed for atmospheric CO2 measurements. This new 2-miron pulsed IPDA lidar has been flown in spring of 2014 for total ten flights with 27 flight hours. It provides high precision measurement capability by unambiguously eliminating contamination from aerosols and clouds that can bias the IPDA measurement.

  7. A Relationship between REM Sleep Measures and the Duration of Posttraumatic Stress Disorder in a Young Adult Urban Minority Population

    PubMed Central

    Mellman, Thomas A.; Kobayashi, Ihori; Lavela, Joseph; Wilson, Bryonna; Hall Brown, Tyish S.

    2014-01-01

    Study Objective: To determine relationships of polysomnographic (PSG) measures with posttraumatic stress disorder (PTSD) in a young adult, urban African American population. Design: Cross-sectional, clinical and laboratory evaluation. Setting: Community recruitment, evaluation in the clinical research unit of an urban University hospital. Participants: Participants (n = 145) were Black, 59.3% female, with a mean age of 23.1 y (SD = 4.8). One hundred twenty-one participants (83.4%) met criteria for trauma exposure, the most common being nonsexual violence. Thirty-nine participants (26.9%) met full (n = 19) or subthreshold criteria (n = 20) for current PTSD, 41 (28.3%) had met lifetime PTSD criteria and were recovered, and 65 (45%) were negative for PTSD. Measurements and Results: Evaluations included the Clinician Administered PTSD Scale (CAPS) and 2 consecutive nights of overnight PSG. Analysis of variance did not reveal differences in measures of sleep duration and maintenance, percentage of sleep stages, and the latency to and duration of uninterrupted segments of rapid eye movement (REM) sleep by study group. There were significant relationships between the duration of PTSD and REM sleep percentage (r = 0.53, P = 0.001), REM segment length (r = 0.43, P = 0.006), and REM sleep latency (r = -0.34, P < 0.03) among those with current PTSD that persisted when removing cases with, or controlling for, depression. Conclusions: The findings are consistent with observations in the literature of fragmented and reduced REM sleep with posttraumatic stress disorder (PTSD) relatively proximate to trauma exposure and nondisrupted or increased REM sleep with chronic PTSD. Citation: Mellman TA, Kobayashi I, Lavela J, Wilson B, Hall Brown TS. A relationship between REM sleep measures and the duration of posttraumatic stress disorder in a young adult urban minority population. SLEEP 2014;37(8):1321-1326. PMID:25083012

  8. Measurements of the elemental and isotopic composition of interplanetary dust collected on LDEF. [Long Duration Exposure Facility

    NASA Technical Reports Server (NTRS)

    Fechtig, H.; Jessberger, E.; Hoerz, F.; Igenbergs, E.; Kuczera, H.

    1985-01-01

    A passive interplanetary dust collection experiment, currently in orbit aboard the Long Duration Exposure Facility, is described. The collectors, germanium target plates covered by metallized Mylar foils, are designed for secondary ion mass spectrometry measurements of the elemental and isotopic compositions of residues resulting from micrometeoroid (greater than 10 to the -10th grams) impacts. Impact simulation experiments have demonstrated the validity of the collection concept. Quantitative elemental analyses are complicated by the nonuniform distribution of projectile-derived elements.

  9. Generation and Propagation of a Picosecond Acoustic Pulse at a Buried Interface: Time-Resolved X-Ray Diffraction Measurements

    SciTech Connect

    Lee, S.H.; Cavalieri, A.L.; Fritz, D.M.; Swan, M.C.; Reis, D.A.; Hegde, R.S.; Reason, M.; Goldman, R.S.

    2005-12-09

    We report on the propagation of coherent acoustic wave packets in (001) surface oriented Al{sub 0.3}Ga{sub 0.7}As/GaAs heterostructure, generated through localized femtosecond photoexcitation of the GaAs. Transient structural changes in both the substrate and film are measured with picosecond time-resolved x-ray diffraction. The data indicate an elastic response consisting of unipolar compression pulses of a few hundred picosecond duration traveling along [001] and [001] directions that are produced by predominately impulsive stress. The transmission and reflection of the strain pulses are in agreement with an acoustic mismatch model of the heterostructure and free-space interfaces.

  10. Combining transcutaneous blood gas measurement and pulse oximetry.

    PubMed

    Eberhard, Patrick; Gisiger, P A; Gardaz, J P; Spahn, D R

    2002-01-01

    We are describing the preliminary results of tests performed in adult volunteers and in adult patients during and after general anesthesia with a miniaturized single sensor combining the continuous and non-invasive measurement of oxygen saturaiton by pulse oximetry (SpO2) and transcutaneous PCO2 (OxiCarbo sensor). The sensor is heated to 42 degrees C to arterialize the cutaneous tissue and is applied at the ear lobe with a special low-pressure clip. The results indicate a good agreement between ear lobe PCO2 and arterial PCO2 in the range 35 to 70 mmHg (10 patients, number of measurements 104, regression line TcPCO2 = 1.01 PaCO2 + 0.59 mmHg, bias 1.22 mmHg, SD 3.69 mmHg) and between ear lobe SpO2 and SaO2 (bias 0.44% with SD 0.77% in the range 80% to 100%, bias 1.39% with SD 1.43% in the range 60% to 80%). The ear lobe OxiCarbog sensor detects the SpO2 change 5 to 37 sec faster than a finger sensor and the PCO2 change 9 to 48 sec faster than a transcutaneous sensor fixed at the upper arm. Further improvements versus single sensors are a higher stability of the SpO2 signal and the possibility of performing long term SpO2 and PCO2 measurement at the ear lobe. PMID:11900043

  11. Dual polarized receiving steering antenna array for measurement of ultrawideband pulse polarization structure.

    PubMed

    Balzovsky, E V; Buyanov, Yu I; Koshelev, V I; Nekrasov, E S

    2016-03-01

    To measure simultaneously two orthogonal components of the electromagnetic field of nano- and subnano-second duration, an antenna array has been developed. The antenna elements of the array are the crossed dipoles of dimension 5 × 5 cm. The arms of the dipoles are connected to the active four-pole devices to compensate the frequency response variations of a short dipole in the frequency band ranging from 0.4 to 4 GHz. The dipoles have superimposed phase centers allowing measuring the polarization structure of the field in different directions. The developed antenna array is the linear one containing four elements. The pattern maximum position is controlled by means of the switched ultrawideband true time delay lines. Discrete steering in seven directions in the range from -40° to +40° has been realized. The error at setting the pattern maximum position is less than 4°. The isolation of the polarization exceeds 29 dB in the direction orthogonal to the array axis and in the whole steering range it exceeds 23 dB. Measurement results of the polarization structure of radiated and scattered pulses with different polarization are presented as well. PMID:27036799

  12. Dual polarized receiving steering antenna array for measurement of ultrawideband pulse polarization structure

    NASA Astrophysics Data System (ADS)

    Balzovsky, E. V.; Buyanov, Yu. I.; Koshelev, V. I.; Nekrasov, E. S.

    2016-03-01

    To measure simultaneously two orthogonal components of the electromagnetic field of nano- and subnano-second duration, an antenna array has been developed. The antenna elements of the array are the crossed dipoles of dimension 5 × 5 cm. The arms of the dipoles are connected to the active four-pole devices to compensate the frequency response variations of a short dipole in the frequency band ranging from 0.4 to 4 GHz. The dipoles have superimposed phase centers allowing measuring the polarization structure of the field in different directions. The developed antenna array is the linear one containing four elements. The pattern maximum position is controlled by means of the switched ultrawideband true time delay lines. Discrete steering in seven directions in the range from -40° to +40° has been realized. The error at setting the pattern maximum position is less than 4°. The isolation of the polarization exceeds 29 dB in the direction orthogonal to the array axis and in the whole steering range it exceeds 23 dB. Measurement results of the polarization structure of radiated and scattered pulses with different polarization are presented as well.

  13. The Pain Frequency-Severity-Duration Scale as a Measure of Pain: Preliminary Validation in a Pediatric Chronic Pain Sample

    PubMed Central

    Salamon, Katherine S.; Davies, W. Hobart; Fuentes, Melissa R.; Weisman, Steven J.; Hainsworth, Keri R.

    2014-01-01

    Typically, pain is measured by intensity and sensory characteristics. Although intensity is one of the most common dimensions of pain assessment, it has been suggested that measuring pain intensity in isolation is only capturing part of the pain experience and may not lead to an accurate measurement of how pain impacts a child's daily functioning. The current study aimed to develop a measure that would capture pain intensity along with frequency and duration in a clinical sample of youth diagnosed with chronic pain. The pain-frequency-severity-duration (PFSD) scale was developed and data were collected from a multidisciplinary pain clinic at a large, midwestern children's hospital. Validated measures of functional limitations and health related quality of life were also collected. Significant correlations were found between the PFSD composite score, functional limitations, and health related quality of life. Future research should continue to evaluate this questionnaire utilizing other validated pain measures and other areas potentially impacted by chronic pain and with more diverse samples. This initial finding suggests that the PFSD is a convenient self-reported measure and is strongly related to health related quality of life and functional disability. PMID:24579046

  14. Suzaku Wide-band All-sky Monitor measurements of duration distributions of gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Ohmori, Norisuke; Yamaoka, Kazutaka; Ohno, Masanori; Sugita, Satoshi; Kinoshita, Ryuuji; Nishioka, Yusuke; Hurley, Kevin; Hanabata, Yoshitaka; Tashiro, Makoto; Enomoto, Junichi; Fujinuma, Takeshi; Fukazawa, Yasushi; Iwakiri, Wataru; Kawano, Takafumi; Kokubun, Motohide; Makishima, Kazuo; Matsuoka, Shunsuke; Nagayoshi, Tsutomu; Nakagawa, Yujin E.; Nakaya, Souhei; Nakazawa, Kazuhiro; Takahashi, Tadayuki; Takeda, Sawako; Terada, Yukikatsu; Urata, Yuji; Yabe, Seiya; Yasuda, Tetsuya; Yamauchi, Makoto

    2016-03-01

    We report on the T90 and T50 duration distributions and their relations with spectral hardness using 1464 gamma-ray bursts (GRBs), which were observed by the Suzaku Wide-band All-sky Monitor (WAM) from 2005 August 4 to 2010 December 29. The duration distribution is clearly bimodal in three energy ranges (50-120, 120-250, and 250-550 keV), but is unclear in the 550-5000 keV range, probably because of the limited sample size. The WAM durations decrease with energy according to a power-law index of -0.058(-0.034, +0.033). The hardness-duration relation reveals the presence of short-hard and long-soft GRBs. The short:long event ratio tends to be higher with increasing energy. We compared the WAM distribution with ones measured by eight other GRB instruments. The WAM T90 distribution is very similar to those of INTEGRAL/SPI-ACS and Granat/PHEBUS, and least likely to match the Swift/BAT distribution. The WAM short:long event ratio (0.25:0.75) is much different from Swift/BAT (0.08:0.92), but is almost the same as CGRO/BATSE (0.25:0.75). To explain this difference for BAT, we examined three effects: BAT trigger types, energy dependence of the duration, and detection sensitivity differences between BAT and WAM. As a result, we found that the ratio difference could be explained mainly by energy dependence including soft extended emissions for short GRBs and much better sensitivity for BAT which can detect weak/long GRBs. The reason for the same short:long event ratio for BATSE and WAM was confirmed by calculation using the trigger efficiency curve.

  15. Suzaku Wide-band All-sky Monitor measurements of duration distributions of gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Ohmori, Norisuke; Yamaoka, Kazutaka; Ohno, Masanori; Sugita, Satoshi; Kinoshita, Ryuuji; Nishioka, Yusuke; Hurley, Kevin; Hanabata, Yoshitaka; Tashiro, Makoto S.; Enomoto, Junichi; Fujinuma, Takeshi; Fukazawa, Yasushi; Iwakiri, Wataru; Kawano, Takafumi; Kokubun, Motohide; Makishima, Kazuo; Matsuoka, Shunsuke; Nagayoshi, Tsutomu; Nakagawa, Yujin E.; Nakaya, Souhei; Nakazawa, Kazuhiro; Takahashi, Tadayuki; Takeda, Sawako; Terada, Yukikatsu; Urata, Yuji; Yabe, Seiya; Yasuda, Tetsuya; Yamauchi, Makoto

    2016-06-01

    We report on the T90 and T50 duration distributions and their relations with spectral hardness using 1464 gamma-ray bursts (GRBs), which were observed by the Suzaku Wide-band All-sky Monitor (WAM) from 2005 August 4 to 2010 December 29. The duration distribution is clearly bimodal in three energy ranges (50-120, 120-250, and 250-550 keV), but is unclear in the 550-5000 keV range, probably because of the limited sample size. The WAM durations decrease with energy according to a power-law index of -0.058(-0.034, +0.033). The hardness-duration relation reveals the presence of short-hard and long-soft GRBs. The short:long event ratio tends to be higher with increasing energy. We compared the WAM distribution with ones measured by eight other GRB instruments. The WAM T90 distribution is very similar to those of INTEGRAL/SPI-ACS and Granat/PHEBUS, and least likely to match the Swift/BAT distribution. The WAM short:long event ratio (0.25:0.75) is much different from Swift/BAT (0.08:0.92), but is almost the same as CGRO/BATSE (0.25:0.75). To explain this difference for BAT, we examined three effects: BAT trigger types, energy dependence of the duration, and detection sensitivity differences between BAT and WAM. As a result, we found that the ratio difference could be explained mainly by energy dependence including soft extended emissions for short GRBs and much better sensitivity for BAT which can detect weak/long GRBs. The reason for the same short:long event ratio for BATSE and WAM was confirmed by calculation using the trigger efficiency curve.

  16. Thrust Augmentation Measurements Using a Pulse Detonation Engine Ejector

    NASA Technical Reports Server (NTRS)

    Santoro, Robert J.; Pal, Sibtosh

    2003-01-01

    The present NASA GRC-funded three-year research project is focused on studying PDE driven ejectors applicable to a hybrid Pulse Detonation/Turbofan Engine. The objective of the study is to characterize the PDE-ejector thrust augmentation. A PDE-ejector system has been designed to provide critical experimental data for assessing the performance enhancements possible with this technology. Completed tasks include demonstration of a thrust stand for measuring average thrust for detonation tube multi-cycle operation, and design of a 72-in.-long, 2.25-in.-diameter (ID) detonation tube and modular ejector assembly. This assembly will allow testing of both straight and contoured ejector geometries. Initial ejectors that have been fabricated are 72-in.-long-constant-diameter tubes (4-, 5-, and 6-in.-diameter) instrumented with high-frequency pressure transducers. The assembly has been designed such that the detonation tube exit can be positioned at various locations within the ejector tube. PDE-ejector system experiments with gaseous ethylene/ nitrogen/oxygen propellants will commence in the very near future. The program benefits from collaborations with Prof. Merkle of University of Tennessee whose PDE-ejector analysis helps guide the experiments. The present research effort will increase the TRL of PDE-ejectors from its current level of 2 to a level of 3.

  17. Generation and measurement of ultrashort pulses from the Stanford Superconducting Accelerator free-electron laser

    SciTech Connect

    Richman, B.A.; DeLong, K.W.; Trebino, R.

    1995-11-01

    The authors present results of frequency resolved optical gating (FROG) measurements on the Superconducting Accelerator (SCA) mid-IR free-electron laser (FEL) at Stanford. FROG retrieves complete amplitude and phase content of an optical pulse. First, they review the properties of FELs including the ability to tune wavelength and pulse length. In addition, the electron beam driving the FEL often affects the optical pulse shape. The SCA mid-IR FEL currently operates at wavelengths between 4 {micro}m and 10 {micro}m and its pulse length can be varied from 700 fs to 2 ps. They then describe details of the experimental layout and procedures particular to FELs and to the mid-IR. Finally, they show FROG measurements on the FEL including examples of nearly transform limited pulses, frequency chirped pulses, and pulses distorted by atmospheric water vapor absorption.

  18. Bactericidal effect of a Nd:YAG laser on Enterococcus faecalis at pulse durations of 15 and 25 ms in dentine depths of 500 and 1,000 μm.

    PubMed

    Franzen, René; Gutknecht, Norbert; Falken, Silke; Heussen, Nicole; Meister, Jörg

    2011-01-01

    The success of endodontic treatment depends on the effective elimination of microorganisms from the root canal, and lasers provide more effective disinfection than conventional treatment using rinsing solutions. The objective of this in vitro study was to determine the bactericidal effect of laser irradiation in dentine of various depths at a wavelength of 1,064 nm and pulse durations of 15 and 25 ms. A total of 90 dentine slices were cut from bovine incisors and divided into two groups (45 slices each) of thickness 500 and 1,000 μm. All were inoculated with a suspension of Enterococcus faecalis (5.07 × 10(9) bacteria/ml). Based on the clinically accepted dose (approximately 300 J/cm(2)), the following laser settings were chosen for this study: 1.75 W, 0.7 Hz for 4 s, three repetitions. The two groups were divided into two subgroups of 15 slices each to be irradiated with pulse durations of 15 and 25 ms. The remaining 15 slices per group were not irradiated to serve as a control. After irradiation, the colony-forming units (CFU) were counted and evaluated. To determine the bactericidal effect of irradiation with different pulse durations, the results in the different groups were compared statistically. For all irradiated subgroups a bactericidal effect was observed at pulse durations of 15 and 25 ms (p=0.0085 and p<0.0001). The corresponding average log kills were 0.29 (15 ms) and 0.52 (25 ms) for 500 μm and 0.15 and 0.3 for 1,000 μm, respectively. The results of this in vitro study showed that Nd:YAG laser irradiation with a pulse duration of 15 ms eliminated an average of 49% and 29% of E. faecalis at dentine depths of 500 μm and 1,000 μm, respectively, and irradiation with a pulse duration of 25 ms eliminated 70% (500 μm) and 50% (1,000 μm). However, these values are lower than those achieved with the established protocol using microsecond pulses. PMID:20809081

  19. An apparatus for the measurement of regenerator performance in pulse tube refrigerators

    NASA Technical Reports Server (NTRS)

    Rawlins, Wayne; Radebaugh, Ray

    1990-01-01

    This paper discusses the design and construction of an apparatus to measure the ineffectiveness of regenerators used for pulse tube refrigerators. Because of the fairly large mass flow rates which occur in pulse tube refrigerators, the regenerator ineffectiveness must be made quite small. The apparatus described here allows for the measurement of the refrigerator. A low temperature heat sink of liquid nitrogen is used since it approximates the temperatures normally achieved in a one-stage pulse tube.

  20. Proposal for the measuring molecular velocity vector with single-pulse coherent Raman spectroscopy

    NASA Technical Reports Server (NTRS)

    She, C. Y.

    1983-01-01

    Methods for simultaneous measurements of more than one flow velocity component using coherent Raman spectroscopy are proposed. It is demonstrated that using a kilowatt broad-band probe pulse (3-30 GHz) along with a megawatt narrow-band pump pulse (approximately 100 MHz), coherent Raman signal resulting from a single laser pulse is sufficient to produce a high-resolution Raman spectrum for a velocity measurement.

  1. Pulsed laser manipulation of an optically trapped bead: averaging thermal noise and measuring the pulsed force amplitude.

    PubMed

    Lindballe, Thue B; Kristensen, Martin V G; Berg-Sørensen, Kirstine; Keiding, Søren R; Stapelfeldt, Henrik

    2013-01-28

    An experimental strategy for post-eliminating thermal noise on position measurements of optically trapped particles is presented. Using a nanosecond pulsed laser, synchronized to the detection system, to exert a periodic driving force on an optically trapped 10 μm polystyrene bead, the laser pulse-bead interaction is repeated hundreds of times. Traces with the bead position following the prompt displacement from equilibrium, induced by each laser pulse, are averaged and reveal the underlying deterministic motion of the bead, which is not visible in a single trace due to thermal noise. The motion of the bead is analyzed from the direct time-dependent position measurements and from the power spectrum. The results show that the bead is on average displaced 208 nm from the trap center and exposed to a force amplitude of 71 nanoNewton, more than five orders of magnitude larger than the trapping forces. Our experimental method may have implications for microrheology. PMID:23389179

  2. Measurement of the cosmic-ray antiproton spectrum at solar minimum with a long-duration balloon flight over antarctica.

    PubMed

    Abe, K; Fuke, H; Haino, S; Hams, T; Hasegawa, M; Horikoshi, A; Kim, K C; Kusumoto, A; Lee, M H; Makida, Y; Matsuda, S; Matsukawa, Y; Mitchell, J W; Nishimura, J; Nozaki, M; Orito, R; Ormes, J F; Sakai, K; Sasaki, M; Seo, E S; Shinoda, R; Streitmatter, R E; Suzuki, J; Tanaka, K; Thakur, N; Yamagami, T; Yamamoto, A; Yoshida, T; Yoshimura, K

    2012-02-01

    The energy spectrum of cosmic-ray antiprotons (p's) from 0.17 to 3.5 GeV has been measured using 7886 p's detected by BESS-Polar II during a long-duration flight over Antarctica near solar minimum in December 2007 and January 2008. This shows good consistency with secondary p calculations. Cosmologically primary p's have been investigated by comparing measured and calculated p spectra. BESS-Polar II data show no evidence of primary p's from the evaporation of primordial black holes. PMID:22400920

  3. Measurement of the Cosmic-Ray Antiproton Spectrum at Solar Minimum with a Long-Duration Balloon Flight over Antarctica

    NASA Technical Reports Server (NTRS)

    Abe, K.; Fuke, H.; Haino, S.; Hams, T.; Hasegawa, M.; Horikoshi, A.; Kim, K. C.; Kusumoto, A.; Lee, M. H.; Makida, Y.; Matsuda, S.; Matsukawa, Y.; Mitchell, J. W.; Nishimura, J.; Nozaki, M.; Orito, R.; Ormes, J. F.; Sakai, K.; Sasaki, M.; Seo, E. S.; Shinoda, R.; Streitmatter, R. E.; Suzuki, J.; Tanaka, K.; Thakur, N.

    2012-01-01

    The energy spectrum of cosmic-ray antiprotons (p-bar's) from 0.17 to 3.5 GeV has been measured using 7886 p-bar's detected by BESS-Polar II during a long-duration flight over Antarctica near solar minimum in December 2007 and January 2008. This shows good consistency with secondary p-bar calculations. Cosmologically primary p-bar's have been investigated by comparing measured and calculated p-bar spectra. BESS-Polar II data.show no evidence of primary p-bar's from the evaporation of primordial black holes.

  4. SAMPLING DURATION DEPENDENCE OF SEMI-CONTINUOUS ORGANIC CARBON MEASUREMENTS ON STEADY STATE SECONDARY ORGANIC AEROSOLS

    EPA Science Inventory

    Semi-continuous organic carbon concentrations were measured through several experiments of statically generated secondary organic aerosol formed by hydrocarbon + NOx irradiations. Repeated, randomized measurements of these steady state aerosols reveal decreases in the observed c...

  5. Pulse and hold strategy for switching current measurements

    NASA Astrophysics Data System (ADS)

    Walter, Jochen; Tholén, Erik; Haviland, David B.; Sjöstrand, Joachim

    2007-03-01

    We investigate by theory and experiment, the Josephson junction switching current detector in an environment with frequency-dependent damping. Analysis of the circuit’s phase space shows that a favorable topology for switching can be obtained with overdamped dynamics at high frequencies. A pulse-and-hold method is described, where a fast switch pulse brings the circuit close to an unstable point in the phase space when biased at the hold level. Experiments are performed on Cooper pair transistors and quantronium circuits, which are overdamped at high frequencies with an on-chip RC shunt. For 20μs switch pulses the switching process is well described by thermal equilibrium escape, based on a generalization of the Kramers formula to the case of frequency-dependent damping. A capacitor bias method is used to create very rapid, 25ns switch pulses, where it is observed that the switching process is not governed by thermal equilibrium noise.

  6. Measurement of ultrashort pulses with a non-instantaneous nonlinearity

    SciTech Connect

    DeLong, K.W.; Ladera, C.L.; Trebino, R.; Kohler, B.; Wilson, K.R.

    1995-02-01

    We show how non-instantaneous nonlinearities can be used to characterize an ultrashort pulse in an extension of the Frequency-Resolved Optical Gating technique. We demonstrate this principle using the Raman effect in fused silica.

  7. A measurement of the fast-neutron sensitivity of a Geiger - Müller detector in the pulsed neutron beam from a superconducting cyclotron

    NASA Astrophysics Data System (ADS)

    Maughan, R. L.; Yudelev, M.; Kota, C.

    1996-08-01

    The value of a commercially available miniature energy compensated Geiger - Müller (GM) detector has been determined using the modified lead attenuation method of Hough. The measurements were made in a d(48.5) - Be neutron beam produced by the superconducting cyclotron based neutron therapy facility at Harper Hospital. The unique problems associated with making measurements in a 2 ms duration pulsed beam with a 20% duty cycle are discussed. The beam monitoring system, which allows the beam pulse shape at low beam intensities to be measured, is described. By gating the GM output with a discriminator pulse derived from the beam pulse shape, the gamma-ray count rates and dead-time corrections within the 2 ms pulse and between pulses can be measured separately. The value of determined for this GM detector is consistent with the values measured by other workers with identical and similar detectors in neutron beams with comparable, but not identical, neutron spectra.

  8. Continuous blood pressure measurement using the pulse transit time: Comparison to intra-arterial measurement.

    PubMed

    Patzak, Andreas; Mendoza, Yuri; Gesche, Heiko; Konermann, Martin

    2015-01-01

    Continuous blood pressure (BP) measurement allows the investigation of transient changes in BP and thus may give insights into mechanisms of BP control. We validated a continuous, non-invasive BP measurement based on the pulse transit time (PTT), i.e., BP(PTT), by comparing it with the intra-arterial BP (BP(i.a.)) measurement. Twelve subjects (five females and seven males) were included. BP(i.a.) was obtained from the radial artery using a system from ReCor Medical. Systolic and diastolic BP were calculated using the PTT (BP(PTT), SOMNOscreen). (PTT) was determined from the electrocardiogram and the peripheral pulse wave. The BP was modulated by application of increasing doses of dobutamine (5, 10, 20 μg/kg body mass). Systolic BP(PTT) and systolic BP(i.a.) correlated significantly (R = 0.94). The limits of agreement in the Bland-Altman plot were ± 19 mmHg; the mean values differed by 1 mmHg. The correlation coefficient for the diastolic BP measurements was R = 0.42. The limits of agreement in the Bland-Altman plot were ± 18 mmHg, with a mean difference of 5 mmHg in favour of the BP(PTT). The study demonstrates a significant correlation between the measurement methods for systolic BP. The results encourage the application of PTT-based BP measurement for the evaluation of BP dynamics and pathological BP changes. PMID:25857601

  9. Low noise measurement system for determination of the critical currents in superconducting tapes by a pulse method.

    PubMed

    Ciszek, M; Trojanowski, S

    2011-11-01

    Steady state measurements of the high critical currents in superconducting composite wires and tapes might be burdened with some errors. The origin of the errors is mainly associated with the Joule heat generated at current leads contacts, which at high transport currents can considerably increase temperature of an investigated sample wire. To avoid this unwanted heating phenomenon pulsed current methods are widely used. A waveform of the current pulse is usually shaped by means of a series RLC circuit with the subcritical dumping condition. Measurement results (i.e., a value of current peak, its time derivative, and a voltage drop along a superconducting sample) are recorded by means of a 4-channels, 12-bit resolution, 50 ns sampling time, digital recorder. Very low noise, broadband, voltage preamplifiers, based on rf bipolar transistors, were designed and fabricated. From the data, current-voltage characteristics are plotted and then the critical currents of investigated tapes are determined. Presented in the work our home-made, low noise, measurement setup allows to obtain a current pulse of about 4000 A at duration time of several milliseconds. PMID:22128996

  10. A prospective study analyzing the application of radiofrequency energy and high-voltage, ultrashort pulse duration electrical fields on the quantitative reduction of adipose tissue

    PubMed Central

    Duncan, Diane Irvine; Kim, Theresa H. M.; Temaat, Robbin

    2016-01-01

    Noninvasive fat reduction is claimed by many device manufacturers, but proof of efficacy has been difficult to establish. This prospective study was designed to measure the reduction of fat thickness and actual volume reduction in 20 female patients treated with an external radiofrequency (RF) device. This device combines RF heat, suction coupled vacuum, and oscillating electrical pulses that induce adipocyte death over time. Patients underwent pre- and post-treatment and intercurrent measurements of weight, body mass index, ultrasonic transcutaneous fat thickness, and 2D and 3D Vectra photography with independent calculation of circumferential and volumetric change. Mean transcutaneous ultrasound thickness at reproducible points was 2.78 cm; at 1-month post-treatment, the mean fat thickness was 1.71 cm. At 3-month post-treatment, the mean fat thickness reduction was 39.6%. Vectra circumference measurements were taken at 10-mm intervals, with postural and breathing cycle control. Independent analysis of serial measurements from + 60 to − 70 mm showed mean abdominal circumference measurement of 2.3 cm. Mean abdominal volume loss was 202.4 and 428.5 cc at 1- and 3-month post-treatment, respectively. Scanning electron microscopy confirmed that permanent cell destruction was caused by irreversible electroporation. Pyroptosis appears to be the mechanism of action. PMID:26962636

  11. A prospective study analyzing the application of radiofrequency energy and high-voltage, ultrashort pulse duration electrical fields on the quantitative reduction of adipose tissue.

    PubMed

    Duncan, Diane Irvine; Kim, Theresa H M; Temaat, Robbin

    2016-10-01

    Noninvasive fat reduction is claimed by many device manufacturers, but proof of efficacy has been difficult to establish. This prospective study was designed to measure the reduction of fat thickness and actual volume reduction in 20 female patients treated with an external radiofrequency (RF) device. This device combines RF heat, suction coupled vacuum, and oscillating electrical pulses that induce adipocyte death over time. Patients underwent pre- and post-treatment and intercurrent measurements of weight, body mass index, ultrasonic transcutaneous fat thickness, and 2D and 3D Vectra photography with independent calculation of circumferential and volumetric change. Mean transcutaneous ultrasound thickness at reproducible points was 2.78 cm; at 1-month post-treatment, the mean fat thickness was 1.71 cm. At 3-month post-treatment, the mean fat thickness reduction was 39.6%. Vectra circumference measurements were taken at 10-mm intervals, with postural and breathing cycle control. Independent analysis of serial measurements from + 60 to - 70 mm showed mean abdominal circumference measurement of 2.3 cm. Mean abdominal volume loss was 202.4 and 428.5 cc at 1- and 3-month post-treatment, respectively. Scanning electron microscopy confirmed that permanent cell destruction was caused by irreversible electroporation. Pyroptosis appears to be the mechanism of action. PMID:26962636

  12. Cerebral responses to across- and within-category change of vowel durations measured by near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Minagawa-Kawai, Yasuyo; Mori, Koichi; Furuya, Izumi; Hayashi, Ryoko; Sato, Yutaka

    2002-05-01

    The present study examined cerebral responses to phoneme categories, using near-infrared spectroscopy (NIRS) by measuring the concentration and oxygenation of hemoglobin accompanying local brain activities. Targeted phonemes used here are Japanese long and short vowel categories realized only by durational differences. Results of NIRS and behavioral test revealed NIRS could capture phoneme-specific information. The left side of the auditory area showed large hemodynamic changes only for contrasting stimuli between which phonemic boundary was estimated (across-category condition), but not for stimuli differing by an equal duration but belonging to the same phoneme category (within-category condition). Left dominance in phoneme processing was also confirmed for the across-category stimuli. These findings indicate that the Japanese vowel contrast based only on duration is dealt with in the same language-dominant hemisphere as the other phonemic categories as studied with MEG and PET, and that the cortical activities related to its processing can be detected with NIRS. [Work supported by Japan Society for Promotion of Science (No. 8484) and a grant from Ministry of Health and Welfare of Japan.

  13. Thrust Stand Measurements of a Conical Pulsed Inductive Plasma Thruster

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.; Emsellem, Gregory D.

    2012-01-01

    Pulsed inductive plasma thrusters [1-3] are spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. The thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current. Propellant is accelerated and expelled at a high exhaust velocity (O(10-100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, pulsed inductive plasma thrusters can su er from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. The Microwave Assisted Discharge Inductive Plasma Accelerator (MAD-IPA)[4], shown in Fig. 1 is a pulsed inductive plasma thruster that is able to operate at lower pulse energies by partially ionizing propellant with an electron cyclotron resonance (ECR) discharge inside a conical inductive coil whose geometry serves to potentially increase propellant and plasma plume containment relative to at coil geometries. The ECR plasma is created with the use of permanent mag- nets arranged to produce a thin resonance region along the inner surface of the coil, restricting plasma formation and, in turn, current sheet formation to areas of high magnetic coupling to the driving coil.

  14. Thrust Stand Measurements of a Conical Inductive Pulsed Plasma Thruster

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.

    2013-01-01

    Inductive Pulsed Plasma Thrusters (iPPT) spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. The thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current Propellant is accelerated and expelled at a high exhaust velocity (O(10 -- 100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, inductive pulsed plasma thrusters can suffer from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, inductive pulsed plasma thrusters can suffer from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. A conical coil geometry may offer higher propellant utilization efficiency over that of a at inductive coil, however an increase in propellant utilization may be met with a decrease in axial electromagnetic acceleration, and in turn, a decrease in the total axially-directed kinetic energy imparted to the propellant.

  15. Effect of noise on Frequency-Resolved Optical Gating measurements of ultrashort pulses

    SciTech Connect

    Fittinghoff, D.N.; DeLong, K.W.; Ladera, C.L.; Trebino, R.

    1995-02-01

    We study the effects of noise in Frequency-Resolved Optical Gating measurements of ultrashort pulses. We quantify the measurement accuracy in the presence of additive, muliplicative, and quantization noise, and discuss filtering and pre-processing of the data.

  16. Low frequency Raman gain measurements using chirped pulses.

    PubMed

    Dogariu, A; Hagan, D

    1997-08-01

    Two-beam coupling, attributed to Raman gain, is observed in dielectrics using chirped femtosecond pulses. A time resolved pump-probe geometry is used to vary the frequency difference between pulses in the terahertz frequency band. Stimulated Raman scattering couples the pulses transferring energy from the higher to the lower frequency beam, resulting in a dispersion shaped curve as a function of the temporal delay, dependent on the product of the pump and probe irradiances. The observed signal gives the Raman gain in SiO2 and PbF2 for detunings up to 10 THz (approximately 300 cm -1 ) using mm-thick samples. This method may also be sensitive to the electronic motion responsible for bound-electronic nonlinear refractive index, which could yield the optical response time of bound electrons. PMID:19373383

  17. Dose measurements in pulsed radiation fields with commercially available measuring components.

    PubMed

    Friedrich, Sabrina; Hupe, Oliver

    2016-03-01

    Dose measurements in pulsed radiation fields with dosemeters using the counting technique are known to be inappropriate. Therefore, there is a demand for a portable device able to measure the dose in pulsed radiation fields. As a detector, ionisation chambers seem to be a good alternative. In particular, using a secondary standard ionisation chamber in combination with a reliable charge-measuring system would be a good solution. The Physikalisch-Technische Bundesanstalt (PTB) uses secondary standard ionisation chambers in combination with PTB-made measuring electronics for dose measurements at its reference fields. However, for general use, this equipment is too complex. For measurements on-site, a mobile special electronic system [Hupe, O. and Ankerhold, U. Determination of ambient and personal dose equivalent for personnel and cargo security screening. Radiat. Prot. Dosim. 121: (4), 429-437 (2006)] has been used successfully. Still, for general use, there is a need for a much simpler but a just as good solution. A measuring instrument with very good energy dependence for H*(10) is the secondary standard ionisation chamber HS01. An easy-to-use and commercially available electrometer for measuring the generated charges is the UNIDOS by PTW Freiburg. Depending on the expected dose values, the ionisation chamber used can be selected. In addition, measurements have been performed by using commercially available area dosemeters, e.g. the Mini SmartION 2120S by Thermo Scientific, using an ionisation chamber and the Szintomat 6134 A/H by Automess, using a scintillation detector. PMID:26056377

  18. A 2-Micron Pulsed Integrated Path Differential Absorption Lidar Development For Atmospheric CO2 Concentration Measurements

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Reithmaier, Karl; Bai, Yingxin; Trieu, Bo C.; Refaat, Tamer F.; Kavaya, Michael J.; Singh, Upendra N.

    2012-01-01

    A 2-micron pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This instrument will provide an alternate approach to measure atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement.

  19. Measurement of Cosmic-Ray Antiproton Spectrum at Solar Minimum with a Long-Duration Balloon Flight in Antarctica

    NASA Technical Reports Server (NTRS)

    Abe, K.; Fuke, H.; Haino, S.; Hams, T.; Hasegawa, M.; Horikoshi, A.; Kim, K. C.; Kusumoto, A.; Lee, M. H.; Makida, Y.; Matsuda, S.; Matsukawa, Y.; Mitchell, J. W.; Nishimura, J.; Nozaki, M.; Orito, R.; Ormes, J. F.; Sakai, K.; Sasaki, M.; Seo, E. S.; Shinoda, R.; Streitmatter, R. E.; Suzuki, J.; Tanaka, K.; Thakur, N.

    2011-01-01

    The energy spectrum of cosmic-ray antiprotons (p(raised bar)'s) collected by the BESS-Polar II instrument during a long-duration flight over Antarctica in the solar minimum period of December 2007 through January 2008. The p(raised bar) spectrum measured by BESS-Polar II shows good consistency with secondary p(raised bar) calculations. Cosmologically primary p(raised bar)'s have been searched for by comparing the observed and calculated p(raised bar) spectra. The BESSPolar II result shows no evidence of primary p(raised bar)'s originating from the evaporation of PBH.

  20. Pulsed-injection method for blood flow velocity measurement in intraarterial digital subtraction angiography.

    PubMed

    Shaw, C G; Plewes, D B

    1986-08-01

    The pulsed-injection method for measuring the velocity of blood flow in intraarterial digital subtraction angiography is described. With this technique, contrast material is injected at a pulsing frequency as high as 15 Hz, so that two or more boluses can be imaged simultaneously. The velocity of flow is determined by measuring the spacing between the boluses and multiplying it by the pulsing frequency. Results of tests with phantoms correlate well with flow measurements obtained with a graduated cylinder for velocities ranging from 8 to 60 cm/sec. The potential of the method for time-dependent velocity measurement has been demonstrated with simulated pulsatile flows. PMID:3523598

  1. Optical measurement on quantum cascade lasers using femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Cai, Hong

    Quantum cascade lasers (QCLs) as the state-of-the-art mid-infrared (mid-IR) coherent sources have been greatly developed in aspects such as output power, energy efficiency and spectral purity. However, there are additional applications of QCLs in high demand, namely mode-locking, mid-IR modulation, etc. The inherent optical properties and ultrafast carrier dynamics can lead to solutions to these challenges. In this dissertation, we further characterize QCLs using mid-IR femtosecond (fs) pulses generated from a laser system consisting of a Ti:sapphire oscillator, a Ti:sapphire regenerative amplifier, an optical parametric amplifier and a difference frequency generator. We study the Kerr nonlinearity of QCLs by coupling resonant and off-resonant mid-IR fs pulses into an active QCL waveguide. We observe an increase in the spectral width of the transmitted fs pulses as the coupled mid-IR pulse power increases. This is explained by the self-phase modulation effect due to the large Kerr nonlinearity of QCL waveguides. We further confirm this effect by observing the intensity dependent far-field profile of the transmitted mid-IR pulses, showing the pulses undergo self-focusing as they propagate through the active QCL due to the intensity dependent refractive index. The finite-difference time-domain simulations of QCL waveguides with Kerr nonlinearity incorporated show similar behavior to the experimental results. The giant Kerr nonlinearity investigated here may be used to realize ultrafast pulse generation in QCLs. In addition, we temporally resolved the ultrafast mid-infrared transmission modulation of QCLs using a near-infrared pump/mid-infrared probe technique at room temperature. Two different femtosecond wavelength pumps are used with photon energy above and below the quantum well (QW) bandgap. The shorter wavelength pump modulates the mid-infrared probe transmission through interband transition assisted mechanisms, resulting in a high transmission modulation depth

  2. Pulsed D-D Neutron Generator Measurements of HEU Oxide Fuel Pins

    SciTech Connect

    McConchie, Seth; Hausladen, Paul; Mihalczo, John; Blackburn, Brandon; Chichester, David

    2009-03-10

    Pulsed neutron interrogation measurements have been performed on highly enriched uranium (HEU) oxide fuel pins and depleted uranium (DU) metal using a D-D neutron generator (2x10{sup 6} neutrons-s{sup -1}) and moderated {sup 3}He tubes at the Idaho National Laboratory Power Burst Facility. These measurements demonstrate the ability to distinguish HEU from DU by coincidence counting using a pulsed source. The amount of HEU measured was 8 kg in a sealed 55-gallon drum compared to 31 kg of DU. Neutron events were counted during and after the pulse with the Nuclear Materials Identification System (NMIS) and used to calculate the neutron coincidence time distributions. Passive measurements were also performed for comparison with the pulsed measurements. This paper presents the neutron coincidence time distribution and Feynman variance results from the measurements.

  3. Pulsed D-D Neutron Generator Measurements of HEU Oxide Fuel Pins

    SciTech Connect

    McConchie, Seth M; Hausladen, Paul; Mihalczo, John T; Blackburn, Brandon; Chichester, David

    2009-01-01

    Pulsed neutron interrogation measurements have been performed on highly enriched uranium (HEU) oxide fuel pins and depleted uranium (DU) metal using a D-D neutron generator (2 x 10{sup 6} neutrons-s{sup -1}) and moderated {sup 3}He tubes at the Idaho National Laboratory Power Burst Facility. These measurements demonstrate the ability to distinguish HEU from DU by coincidence counting using a pulsed source. The amount of HEU measured was 8 kg in a sealed 55-gallon drum compared to 31 kg of DU. Neutron events were counted during and after the pulse with the Nuclear Materials Identification System (NMIS) and used to calculate the neutron coincidence time distributions. Passive measurements were also performed for comparison with the pulsed measurements. This paper presents the neutron coincidence distribution and Feynman variance results from the measurements.

  4. Pulsed D-D Neutron Generator Measurements of HEU Oxide Fuel Pins

    NASA Astrophysics Data System (ADS)

    McConchie, Seth; Hausladen, Paul; Mihalczo, John; Blackburn, Brandon; Chichester, David

    2009-03-01

    Pulsed neutron interrogation measurements have been performed on highly enriched uranium (HEU) oxide fuel pins and depleted uranium (DU) metal using a D-D neutron generator (2×106 neutrons-s-1) and moderated 3He tubes at the Idaho National Laboratory Power Burst Facility. These measurements demonstrate the ability to distinguish HEU from DU by coincidence counting using a pulsed source. The amount of HEU measured was 8 kg in a sealed 55-gallon drum compared to 31 kg of DU. Neutron events were counted during and after the pulse with the Nuclear Materials Identification System (NMIS) and used to calculate the neutron coincidence time distributions. Passive measurements were also performed for comparison with the pulsed measurements. This paper presents the neutron coincidence time distribution and Feynman variance results from the measurements.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  6. Fiber Optic Picosecond Laser Pulse Transmission Line for Hydrogen Ion Beam Profile Measurement

    SciTech Connect

    Liu, Yun; Huang, Chunning; Aleksandrov, Alexander V

    2013-01-01

    We present a fiber optic laser pulse transmission line for non-intrusive longitudinal profile measurement of the hydrogen ion (H-) beam at the front-end of the Spallation Neutron Source (SNS) accelerator. The 80.5 MHz, 2.5 ps, multi-killowatt optical pulses are delivered to the accelerator beam line through a large mode area polarization maintaining optical fiber to ensure a high measurement stability. The transmission efficiency, output laser beam quality, pulse jitter and pulse width broadening over a 100-ft fiber line are experimentally investigated. A successful measurement of the H- beam microbunch (~130 ps) profile is obtained. Our experiment is the first demonstration of particle beam profile diagnostics using fiber optic laser pulse transmission line.

  7. A New Signal Processing Technique for Neutron Capture Cross Section Measurement Based on Pulse Width Analysis

    NASA Astrophysics Data System (ADS)

    Katabuchi, T.; Matsuhashi, T.; Terada, K.; Mizumoto, M.; Hirose, K.; Kimura, A.; Furutaka, K.; Hara, K. Y.; Harada, H.; Hori, J.; Igashira, M.; Kamiyama, T.; Kitatani, F.; Kino, K.; Kiyanagi, Y.; Koizumi, M.; Nakamura, S.; Oshima, M.; Toh, Y.

    2014-05-01

    A fast data acquisition method based on pulse width analysis was developed for γ-ray spectroscopy with an NaI(Tl) detector. The new method was tested in experiments with standard γ-ray sources and pulsed neutron beam from a spallation neutron source. Pulse height spectra were successfully reconstructed from pulse width distribution by use of an energy calibration curve. The 197Au(n, γ)198Au cross section was measured by this method to test the viability. The obtained experimental cross section showed a good agreement with a calculation using the resonance parameters of JENDL-4.0.

  8. PULSED FLUORESCENCE MONITOR FOR MEASURING AMBIENT NITROGEN DIOXIDE. DEVELOPMENT OF A LABORATORY PROTOTYPE

    EPA Science Inventory

    A prototype pulsed flashlamp monitor for measuring ambient NO2 has been developed, constructed and tested. The basic principles are similar to a laser fluorescence NO2 monitor developed 3 years earlier by the Electronics Research Lab of the Aerospace Corp. The pulsed system has m...

  9. Focal spot measurement in ultra-intense ultra-short pulse laser facility

    NASA Astrophysics Data System (ADS)

    Liu, Lanqin; Peng, Hansheng; Zhou, Kainan; Wang, Xiaodong; Wang, Xiao; Zeng, Xiaoming; Zhu, Qihua; Huang, Xiaojun; Wei, Xiaofeng; Ren, Huan

    2005-06-01

    A peak power of 286-TW Ti:sapphire laser facility referred to as SILEX-I was successfully built at China Academy of Engineering Physics, for a pulse duration of 30 fs in a three-stage Ti:sapphire amplifier chain based on chirped-pulse amplification. The beam have a wavefront distortion of 0.63μm PV and 0.09μm RMS, and the focal spot with an f/2.2 OAP is 5.7μm, to our knowledge, this is the best far field obtained for high-power ultra-short pulse laser systems with no deformable mirror wavefront correction. The peak focused intensity of ~1021W /cm2 were expected.

  10. Development of Modulator Pulse Stability Measurement Device and Test Results at SLAC

    SciTech Connect

    Huang, C.; Burkhart, C.; Kemp, M.; Morris, B.; Beukers, T.; Ciprian, R.; Nguyen, M.; /SLAC

    2011-08-19

    In this paper, the development of a pulse stability measurement device is presented. The measurement accuracy is better than 250uV, about 4.2ppm of a typical 60V input pulse. Pulse signals up to +/- 80V peak can be measured. The device works together with an oscilloscope. The primary function of the measurement device is to provide a precision offset, such that variations in the flattop of the modulator voltage pulse can be accurately resolved. The oscilloscope records the difference between the pulse flattop and the reference for a series of waveforms. The scope math functions are utilized to calculate the rms variations over the series. The frequency response of the device is characterized by the measured cutoff frequency of about 6.5MHz. In addition to detailing the design and calibration of the precision pulse stability device, measurements of SLAC line-type linac modulators and recently developed induction modulators will be presented. Factors affecting pulse stability will be discussed.

  11. Reliability and Validity of Ultrasound Cross Sectional Area Measurements for Long-Duration Spaceflight

    NASA Technical Reports Server (NTRS)

    Scott, Jessica M.; Martin, David S.; Cunningham, David; Matz, Timothy; Caine, Timothy; Hackney, Kyle J.; Arzeno, Natalia; Ploutz-Snyder, Lori

    2010-01-01

    Limb muscle atrophy and the accompanying decline in function can adversely affect the performance of astronauts during mission-related activities and upon re-ambulation in a gravitational environment. Previous characterization of space flight-induced muscle atrophy has been performed using pre and post flight magnetic resonance imaging (MRI). In addition to being costly and time consuming, MRI is an impractical methodology for assessing in-flight changes in muscle size. Given the mobility of ultrasound (US) equipment, it may be more feasible to evaluate changes in muscle size using this technique. PURPOSE: To examine the reliability and validity of using a customized template to acquire panoramic ultrasound (US) images for determining quadriceps and gastrocnemius anatomical cross sectional area (CSA). METHODS: Vastus lateralis (VL), rectus femoris (RF), medial gastrocnemius (MG), and lateral gastrocnemius (LG) CSA were assessed in 10 healthy individuals (36+/-2 yrs) using US and MRI. Panoramic US images were acquired by 2 sonographers using a customized template placed on the thigh and calf and analyzed by the same 2 sonographers (CX50 Philips). MRI images of the leg were acquired while subjects were supine in a 1.5T scanner (Signa Horizon LX, General Electric) and were analyzed by 3 trained investigators. The average of the 2 US and 3 MRI values were used for validity analysis. RESULTS: High inter-experimenter reliability was found for both the US template and MRI analysis as coefficients of variation across muscles ranged from 2.4 to 4.1% and 2.8 to 3.8%, respectively. Significant correlations were found between US and MRI CSA measures (VL, r = 0.85; RF, r = 0.60; MG, r = 0.86; LG, r = 0.73; p < 0.05). Furthermore, the standard error of measurement between US and MRI ranged from 0.91 to 2.09 sq cm with high limits of agreement analyzed by Bland-Altman plots. However, there were significant differences between absolute values of MRI and US for all muscles

  12. Wave system fitting: A new method for force measurements in shock tunnels with long test duration

    NASA Astrophysics Data System (ADS)

    Luo, Changtong; Wang, Yunpeng; Wang, Chun; Jiang, Zonglin

    2015-10-01

    Force measurements in shock tunnels are difficult due to the existence of vibrations excited by a sudden aerodynamic loading. Accelerometer inertia compensation could reduce its negative effect to some extent, but has inherent problems. A new signal decomposition method, wave system fitting (WSF), is proposed to remove vibration waves of low frequency. The WSF is accelerometer-free. It decomposes the balance signal and can separate vibration waves without the influence on the DC component, and it does work no matter the cycle of the sample signal is complete or not. As a standard signal post-processing tool in JF-12, the application results show that it works reliably with high accuracy, and it can also explain puzzling signals encountered in JF-12. WSF method is especially useful and irreplaceable whenever only a few cycles of a periodic signal could be obtained, as is usual for shock tunnels.

  13. Thrust Stand Measurements of a Conical Inductive Pulsed Plasma Thruster

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.

    2012-01-01

    Inductive Pulsed Plasma Thrusters (iPPT) are spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. The thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current. Propellant is accelerated and expelled at a high exhaust velocity (O(10 .. 100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, inductive pulsed plasma thrusters can suffer from both high pulse energy requirements imposed by the voltage demands of inductive propellant ionization, and low propellant utilization efficiencies. A conical coil geometry may o er higher propellant utilization efficiency over that of a at inductive coil, however an increase in propellant utilization may be met with a decrease in axial electromagnetic acceleration, and in turn, a decrease in the total axially-directed kinetic energy imparted to the propellant.

  14. PULSE BROADENING MEASUREMENTS FROM THE GALACTIC CENTER PULSAR J1745-2900

    SciTech Connect

    Spitler, L. G.; Lee, K. J.; Eatough, R. P.; Kramer, M.; Karuppusamy, R.; Desvignes, G.; Champion, D. J.; Falcke, H.; Bassa, C. G.; Lyne, A. G.; Stappers, B. W.; Cognard, I.; Cordes, J. M.

    2014-01-01

    We present temporal scattering measurements of single pulses and average profiles of PSR J1745-2900, a magnetar recently discovered only 3 arcsec away from Sagittarius A* (Sgr A*), from 1.2 to 18.95 GHz using the Effelsberg 100 m Radio Telescope, the Nançay Decimetric Radio Telescope, and the Jodrell Bank Lovell Telescope. Single pulse analysis shows that the integrated pulse profile above 2 GHz is dominated by pulse jitter, while below 2 GHz the pulse profile shape is dominated by scattering. This is the first object in the Galactic center (GC) with both pulse broadening and angular broadening measurements. We measure a pulse broadening time scale at 1 GHz of τ{sub 1GHz} = 1.3 ± 0.2 and pulse broadening spectral index of α = –3.8 ± 0.2, which is several orders of magnitude lower than predicted by the NE2001 model (Cordes and Lazio 2002). If this scattering time scale is representative of the GC as a whole, then previous surveys should have detected many pulsars. The lack of detections implies either our understanding of scattering in the GC is incomplete or there are fewer pulsars in the GC than previously predicted. Given that magnetars are a rare class of radio pulsar, there are likely many canonical and millisecond pulsars in the GC, and not surprisingly, scattering in the GC is spatially complex.

  15. Development of a Tonometric Sensor with a Decoupled Circular Array for Precisely Measuring Radial Artery Pulse

    PubMed Central

    Jun, Min-Ho; Kim, Young-Min; Bae, Jang-Han; Jung, Chang Jin; Cho, Jung-Hee; Jeon, Young Ju

    2016-01-01

    The radial artery pulse is one of the major diagnostic indices used clinically in both Eastern and Western medicine. One of the prominent methods for measuring the radial artery pulse is the piezoresistive sensor array. Independence among channels and an appropriate sensor arrangement are important for effectively assessing the spatial-temporal information of the pulse. This study developed a circular-type seven-channel piezoresistive sensor array using face-down bonding (FDB) as one of the sensor combination methods. The three-layered housing structure that included independent pressure sensor units using the FDB method not only enabled elimination of the crosstalk among channels, but also allowed various array patterns to be created for effective pulse measurement. The sensors were arranged in a circular-type arrangement such that they could estimate the direction of the radial artery and precisely measure the pulse wave. The performance of the fabricated sensor array was validated by evaluating the sensor sensitivity per channel, and the possibility of estimating the blood vessel direction was demonstrated through a radial artery pulse simulator. We expect the proposed sensor to allow accurate extraction of the pulse indices for pulse diagnosis. PMID:27240363

  16. Influence of stem temperature changes on heat pulse sap flux density measurements.

    PubMed

    Vandegehuchte, Maurits W; Burgess, Stephen S O; Downey, Alec; Steppe, Kathy

    2015-04-01

    While natural spatial temperature gradients between measurement needles have been thoroughly investigated for continuous heat-based sap flow methods, little attention has been given to how natural changes in stem temperature impact heat pulse-based methods through temporal rather than spatial effects. By modelling the theoretical equation for both an ideal instantaneous pulse and a step pulse and applying a finite element model which included actual needle dimensions and wound effects, the influence of a varying stem temperature on heat pulse-based methods was investigated. It was shown that the heat ratio (HR) method was influenced, while for the compensation heat pulse and Tmax methods changes in stem temperatures of up to 0.002 °C s(-1) did not lead to significantly different results. For the HR method, rising stem temperatures during measurements led to lower heat pulse velocity values, while decreasing stem temperatures led to both higher and lower heat pulse velocities, and to imaginary results for high flows. These errors of up to 40% can easily be prevented by including a temperature correction in the data analysis procedure, calculating the slope of the natural temperature change based on the measured temperatures before application of the heat pulse. Results of a greenhouse and outdoor experiment on Pinus pinea L. show the influence of this correction on low and average sap flux densities. PMID:25145698

  17. In situ membrane resistance measurements in polymer electrolyte fuel cells by fast auxiliary current pulses

    SciTech Connect

    Buechi, F.N.; Scherer, G.G.; Marek, A.

    1995-06-01

    A solid-state current Pulse generator for in situ membrane resistance measurements by superimposed square current pulses in polymer electrolyte fuel cells was designed and built. The choice of the measuring technique and of parameters of the instrumentation was based on a critical analysis of the relevant electrochemical and physical processes. The inductance of the current pulse path is very low ({approx}5 nH), because the last stage of the generator is directly attached to the fuel cell. This low inductance -permits the generation of 5 A pulses with extremely fast (decay time {<=}5 ns) trailing edges (accompanied by a moderate ringing), which in turn makes it possible to measure the voltage transient induced by the current decay, with gigahertz resolution. The voltage transient is analyzed in a time window of 200 to 700 ns after the end of the pulse. By measurements in this time window, it is possible to separate accurately the ohmic series resistance of the cell (membrane resistance) from the other over potentials at the electrochemical interfaces. Because the pulse current path is independent of the dc loop, the resistance can be measured independently of the dc value, i.e., at open circuit and under high current density conditions. The instrument was tested, and the results were analyzed for accuracy. Resistances down to 2 m{Omega} can be measured with an error of <5%. The influence of the pulse length and pulse amplitude on the cell voltage response was also investigated. For cell resistances in the order of few milliohms, a current pulse amplitude of 5 A is the minimum requirement for accurate measurements.

  18. Multiresolution Approach for Noncontact Measurements of Arterial Pulse Using Thermal Imaging

    NASA Astrophysics Data System (ADS)

    Chekmenev, Sergey Y.; Farag, Aly A.; Miller, William M.; Essock, Edward A.; Bhatnagar, Aruni

    This chapter presents a novel computer vision methodology for noncontact and nonintrusive measurements of arterial pulse. This is the only investigation that links the knowledge of human physiology and anatomy, advances in thermal infrared (IR) imaging and computer vision to produce noncontact and nonintrusive measurements of the arterial pulse in both time and frequency domains. The proposed approach has a physical and physiological basis and as such is of a fundamental nature. A thermal IR camera was used to capture the heat pattern from superficial arteries, and a blood vessel model was proposed to describe the pulsatile nature of the blood flow. A multiresolution wavelet-based signal analysis approach was applied to extract the arterial pulse waveform, which lends itself to various physiological measurements. We validated our results using a traditional contact vital signs monitor as a ground truth. Eight people of different age, race and gender have been tested in our study consistent with Health Insurance Portability and Accountability Act (HIPAA) regulations and internal review board approval. The resultant arterial pulse waveforms exactly matched the ground truth oximetry readings. The essence of our approach is the automatic detection of region of measurement (ROM) of the arterial pulse, from which the arterial pulse waveform is extracted. To the best of our knowledge, the correspondence between noncontact thermal IR imaging-based measurements of the arterial pulse in the time domain and traditional contact approaches has never been reported in the literature.

  19. Laser ranging by time-of-flight measurement of femtosecond light pulses

    NASA Astrophysics Data System (ADS)

    Kim, Young-Jin

    2014-04-01

    Time-of-flight (TOF) measurement of femtosecond light pulses was investigated for laser ranging of long distances with sub-micrometer precision in the air. The bandwidth limitation of the photo-detection electronics used in timing femtosecond pulses was overcome by adopting a type-II nonlinear second-harmonic crystal that permits producing the balanced optical cross-correlation signal between two overlapped light pulses. This method offered a sub-femtosecond timing resolution in determining the temporal offset between two pulses through lock-in control of the pulse repetition rate with reference to the atomic clock. The exceptional ranging capability was verified by measuring various distances from 1.5 m to 700 m. This method is found suited for terrestrial land surveying and space missions of formation-flying satellites.

  20. Measurement of complex ultrashort laser pulses using frequency-resolved optical gating

    NASA Astrophysics Data System (ADS)

    Xu, Lina

    This thesis contains three components of research: a detailed study of the performance of Frequency-Resolved Optical Gating (FROG) for measuring complex ultrashort laser pulses, a new method for measuring the arbitrary polarization state of an ultrashort laser pulse using Tomographic Ultrafast Retrieval of Transverse Light E-fields (TURTLE) technique, and new approach for measuring two complex pulses simultaneously using PG blind FROG. In recent decades, many techniques for measuring the full intensity and phase of ultrashort laser pulses have been proposed. These techniques include: Spectral Interferometry (SI)[1], Temporal Analysis by Dispersing a Pair of Light E-Field (TADPOLE)[2], Spectral Phase Interferometry for direct electric-field reconstruction (SPIDER)[3], and Frequency-Resolved Optical Gating (FROG)[4]. Each technique is actually a class of techniques that includes different variations on the original idea, such as SEA-SPIDER[5], ZAP SPIDER[6] are two variations of SPIDER. But most of these techniques for measuring ultrashort laser pulses either do not yield the complete time-dependent intensity and phase (e.g., autocorrelation), can at best only measure simple pulses (e.g., SPIDER), or need well characterized reference pulse. In this thesis, we compare the performance of three versions of FROG: second-harmonic-generation (SHG) FROG, polarization-gate (PG) FROG, and cross-correlation FROG (XFROG), the last of which requires a well-characterized reference pulse. We found that the XFROG algorithm converged in all cases and required only one initial guess. The PG FROG algorithm converged for 99% of the moderately complex pulses that we tried, and for over 95% of the most complex pulses (TBP ˜ 100). And the SHG FROG algorithm converged for 95% of the pulses that we tried and for over 80% of the most complex pulses. After some analysis, we found that noise filtering and adding more sampling points to the FROG trace solved the non-converging problems and we

  1. Time-dependent intensity and phase measurements of ultrashort laser pulses as short as 10 fs

    SciTech Connect

    DeLong, K.W.; Fittinghoff, D.N.; Ladera, C.L.; Trebino, R.; Taft, G.; Rundquist, A.; Murnane, M.M.; Kapteyn, H.C.; Christov, I.P.

    1995-05-01

    Frequency-Resolved Optical Gating (FROG) measures the time-dependent intensity and phase of an ultrashort laser pulse. Using FROG, we have tested theories for the operation of sub{minus}10 fs laser oscillators.

  2. Signal to Noise Ratios of Pulsed and Sinewave Modulated Direct Detection Lidar for IPDA Measurements

    NASA Technical Reports Server (NTRS)

    Sun, Xiaoli; Abshire, James B.

    2011-01-01

    The signal-to-noise ratios have been derived for IPDA lidar using a direct detection receiver for both pulsed and sinewave laser modulation techniques, and the results and laboratory measurements are presented

  3. Phase retrieval and time-frequency methods in the measurement of ultrashort laser pulses

    SciTech Connect

    DeLong, K.W.; Fittinghoff, D.N.; Ladera, C.L.; Trebino, R.

    1995-02-01

    Recently several techniques have become available to measure the time- (or frequency-) dependent intensity and phase of ultrashort laser pulses. One of these, Frequency-Resolved Optical Gating (FROG), is rigorous and has achieved single-laser-shot operation. FROG combines the concepts of time-frequency analysis in the form of spectrogram generation (in order to create a two-dimensional problem), and uses a phase-retrieval-based algorithm to invert the experimental data to yield the intensity and phase of the laboratory laser pulse. In FROG it is easy to generate a spectrogram of the unknown signal, and inversion of the spectrogram to recover the signal is the main goal. Because the temporal width of a femtosecond laser pulse is much shorter than anything achievable by electronics, FROG uses the pulse to measure itself. In FROG, the laser pulse is split into two replicas of itself by a partially reflecting beamsplitter, and the two replicas interact with each other in a medium with an instantaneous nonlinear-optical response. This interaction generates a signal field that is then frequency-resolved using a spectrometer. The spectrum of the signal field is measured for all relevant values of the temporal delay between the two pulses. Here, the authors employ FROG and FROG related techniques to measure the time-dependent intensity and phase of an ultrashort laser pulse.

  4. Measuring spatiotemporal intensity-and-phase complexity of multimode fiber output pulses

    NASA Astrophysics Data System (ADS)

    Guang, Zhe; Rhodes, Michelle; Trebino, Rick

    2016-03-01

    We demonstrate ultrashort pulse spatiotemporal field measurement for multimode optical fibers, using a singleframe characterization technique, called Spatially and Temporally Resolved Intensity and Phase Evaluation Device: Full Information from a Single Hologram (STRIPED FISH). We measure STRIPED FISH traces and retrieve the pulse field E(x,y,t) or equivalently E(x,y,ω), to generate movies revealing the field structure induced by propagating modes, due to their differences in field spatial distribution, modal propagation velocity and modal dispersion inside the fiber. We launch femtosecond pulses near 800nm from Ti: Sapphire laser to investigate linearly polarized modes LP01, LP11, LP02 and LP21 in multimode fibers.

  5. Measurement of temperature rises in the femtosecond laser pulsed three-dimensional atom probe

    SciTech Connect

    Cerezo, A.; Smith, G.D.W.; Clifton, P.H.

    2006-04-10

    A previous Letter [B. Gault et al., Appl. Phys. Lett. 86, 094101 (2005)] interpreted measurements of the field evaporation enhancement under femtosecond pulsed laser irradiation of a field emitter in terms of a direct electric field enhancement by the intrinsic field of the laser light. We show that, on the contrary, the field evaporation enhancement is predominantly a thermal heating effect. Indirect measurements of the peak specimen temperature under irradiation by femtosecond laser pulses are consistent with temperature rises obtained using longer laser pulses in a range of earlier work.

  6. Pulse energy measurement at the hard x-ray laser in Japan

    SciTech Connect

    Kato, M.; Tanaka, T.; Saito, N.; Kurosawa, T.; Richter, M.; Sorokin, A. A.; Tiedtke, K.; Kudo, T.; Yabashi, M.; Tono, K.; Ishikawa, T.

    2012-07-09

    The pulse energies of a free electron laser have accurately been measured in the hard x-ray spectral range. In the photon energy regime from 4.4 keV to 16.8 keV, pulse energies up to 100 {mu}J were obtained at the hard x-ray laser facility SACLA (SPring-8 Angstrom Compact free-electron LAser). Two independent methods, using a cryogenic radiometer and a gas monitor detector, were applied and agreement within 3.3% was achieved. Based on our validated pulse energy measurement, a SACLA online monitor detector could be calibrated for all future experiments.

  7. Neutron generator burst timing measured using a pulse shape discrimination plastic scintillator with silicon photomultiplier readout

    NASA Astrophysics Data System (ADS)

    Preston, R. M.; Eberhardt, J. E.; Tickner, J. R.

    2013-12-01

    An EJ-299-34 plastic scintillator with silicon photomultiplier (SiPM) readout was used to measure the fast neutron output of a pulsed Thermo-Fisher A-325 Deuterium-Tritium sealed tube neutron generator (STNG). The SiPM signals were handled by a prototype digital pulse processing system, based on a free-running analogue to digital converter feeding a digital signal processor (DSP). Pulse shape discrimination was used to distinguish between detected fast-neutrons and gammas. Pulse detection, timing, energy and shape were all processed by the DSP in real-time. The time-dependency of the neutron output of the STNG was measured for various pulsing schemes. The switch-on characteristics of the tube strongly depended on the operating settings, with the delay between pulse turn-on and the production of neutrons ranging between 13 μs to 74 μs for the tested pulse rates and duty cycles. This work will facilitate the optimization and modeling of apparatus that use the neutron generator's pulsing abilities.

  8. Microprocessor-controlled phase-measurement system for 2856-MHz pulses

    SciTech Connect

    Fox, J.D.; Schwarz, H.

    1982-04-01

    A computer controlled phase detection system used to measure and stabilize the phase of high power rf pulses in the two mile Stanford Linear Accelerator has been developed. This system measures the phase of a 1 ..mu..sec 2856 50 MW rf pulse with respect to a CW reference signal at the same frequency at a 180 Hz rate with < 0.2/sup 0/ resolution.

  9. Intensity evaluation using a femtosecond pulse laser for absolute distance measurement.

    PubMed

    Wu, Hanzhong; Zhang, Fumin; Li, Jianshuang; Cao, Shiying; Meng, Xiangsong; Qu, Xinghua

    2015-06-10

    In this paper, we propose a method of intensity evaluation based on different pulse models using a femtosecond pulse laser, which enables long-range absolute distance measurement with nanometer precision and large non-ambiguity range. The pulse cross-correlation is analyzed based on different pulse models, including Gaussian, Sech(2), and Lorenz. The DC intensity and the amplitude of the cross-correlation patterns are also demonstrated theoretically. In the experiments, we develop a new combined system and perform the distance measurements on an underground granite rail system. The DC intensity and amplitude of the interference fringes are measured and show a good agreement with the theory, and the distance to be determined can be up to 25 m using intensity evaluation, within 64 nm deviation compared with a He-Ne incremental interferometer, and corresponds to a relative precision of 2.7×10(-9). PMID:26192864

  10. Two-color short-pulse laser altimeter measurements of ocean surface backscatter.

    PubMed

    Abshire, J B; McGarry, J F

    1987-04-01

    The timing and correlation properties of pulsed laser backscatter from the ocean surface have been measured with a two-color short-pulse laser altimeter. The Nd: YAG laser transmitted 70-and 35-ps wide pulses simultaneously at 532 and 355 nm at nadir, and the time-resolved returns were recorded by a receiver with 800-ps response time. The time-resolved backscatter measured at both 330- and 1291-m altitudes showed little pulse broadening due to the submeter laser spot size. The differential delay of the 355- and 532-nm backscattered waveforms were measured with a rms error of ~75 ps. The change in aircraft altitudes also permitted the change in atmospheric pressure to be estimated by using the two-color technique. PMID:20454319

  11. Glucose Measurement by Affinity Sensor and Pulsed Measurements of Fluidic Resistances

    PubMed Central

    Wyss, Thomas; Robin, Franck; Heinemann, Lutz

    2014-01-01

    Affinity sensors for glucose are based on a different measuring principle than the commercially available amperometric needle type sensors: reversible affinity interaction of glucose with specific receptors is the primary recognition mechanism instead of an enzymatic glucose oxidation. A novel pulsed-flow micro-fluidic system was used to characterize first the viscosity of a sensitive liquid containing the glucose receptor Concanavalin A and dextran and in a second approach to characterize the geometry of a fluidic resistance. In the viscometric sensor, glucose of the sensitive liquid is equilibrated, while passing through a dialysis chamber, with the surrounding medium. With the membrane flow sensor, the viscosity of the liquid remains constant but the pores of the flow-resisting membrane contain a swellable hydrogel affecting the width of the pores. Two types of hydrogel were tested with the membrane flow sensor; one is highly sensitive to pH and salt concentration, the other contains receptors of phenyl boronic acids to obtain sensitivity to glucose. The viscometric affinity sensor (first approach) showed a linear response over 0 to 30 mmol/L glucose concentration range. The disturbing effect of air bubbles could be compensated for. The sensing proof of principle of the second approach could be demonstrated by its linear response to different saline concentrations; however, the glucose-sensitive membrane developed showed only a small response to glucose. Glucose monitoring based on this pulsed flow measuring principle offers interesting alternatives for the development of CGM systems with different options for the glucose sensing part. PMID:24876545

  12. Measurement, comparison, and transformation of dynamic magnetization in pulse field and high-frequency alternating field

    NASA Astrophysics Data System (ADS)

    Kodama, K.

    2015-12-01

    Dynamic magnetizations of selected natural samples (sediments and volcanic rocks) were measured in time domain as well as in frequency domain. The time domain measurements were performed in pulse fields with variable lengths (10 μs to 10 ms) and amplitudes (0.5 mT to 0.7 T). To measure hysteresis parameters for small loops, one cycle of positive and negative pulses with different rate of field variation were generated. In the frequency domain, low-field magnetic susceptibility was measured over the frequency rage (1 kHz to 500 kHz) corresponding to the pulse lengths in the time domain measurements. Results in the time domain were characterized by the transient magnetization-field curves that were broadly comparable to the corresponding portions of the hysteresis loops measured by a quasi-static method using a VSM. The dynamic coercivity that is defined as the intersect with the abscissa in the negative regime increased as the pulse length reduced and the pulse peak increased. In strong pulse fields (> 0.5 T), irrespective of the kinds of samples, the magnetization remained at the end of a pulse and decayed exponentially within a few ms, suggesting rapid magnetic relaxations. In weak pulse fields, no such relaxation was observed except for the sediments rich in superparamagnetic (SP) particles. These field dependencies suggest that the relaxations in the strong fields could be due to the dynamics of the domain walls in the MD particles, while those of the sediments in weak fields may be ascribed to the relaxation of the SP particles. Results in the frequency domain were obtained in terms of the frequency spectrum of the real and imaginary components of complex susceptibility. Comparisons and interpretations of the data in these different domains were made in terms of the distribution of relaxation times. Discussions on the numerical conversion and transformation of these data as well as their rock magnetic applications will be provided.

  13. Constant frequency pulsed phase-locked loop measuring device

    NASA Technical Reports Server (NTRS)

    Yost, William T. (Inventor); Kushnick, Peter W. (Inventor); Cantrell, John H. (Inventor)

    1993-01-01

    A measuring apparatus is presented that uses a fixed frequency oscillator to measure small changes in the phase velocity ultrasonic sound when a sample is exposed to environmental changes such as changes in pressure, temperature, etc. The invention automatically balances electrical phase shifts against the acoustical phase shifts in order to obtain an accurate measurement of electrical phase shifts.

  14. 2-micron Pulsed Direct Detection IPDA Lidar for Atmospheric CO2 Measurements

    NASA Astrophysics Data System (ADS)

    Yu, J.; Singh, U.; Petros, M.

    2012-12-01

    A 2-micron high energy, pulsed Integrated Path Differential Absorption (IPDA) lidar is being developed for atmospheric CO2 measurements. Development of this lidar heavily leverages the 2-micron laser technologies developed in LaRC over the last decade. The high pulse energy, direct detection lidar operating at CO2 2-micron absorption band provides an alternate approach to measure CO2 concentrations with significant advantages. It is expected to provide high-precision measurement capability by unambiguously eliminating contamination from aerosols and clouds that can bias the IPDA measurement. Our objective is to integrate an existing high energy double-pulsed 2-micron laser transmitter with a direct detection receiver and telescope to enable an airborne capability to perform a first proof of principle demonstration of airborne direct detection CO2 measurements. The 2-micron transmitter provides 100mJ at 10Hz with double pulse format specifically designed for DIAL/IPDA instrument. The compact, rugged, highly reliable transceiver is based on unique Ho:Tm:YLF high-energy 2-micron pulsed laser technology. All the optical mounts are custom designed and have space heritage. A 16-inch diameter telescope has been designed and being manufactured for the direct detection lidar. The detector is an InGaAs Positive-Intrinsic-Negative (PIN) photodiode manufactured by Hamamatsu Corporation. The performance of the detector is characterized at various operating temperatures and bias voltages for spectral response, NEP, response time, dynamic range, and linearity. A collinear lidar structure is designed to be integrated to NASA UC12 or B200 research aircrafts. This paper will describe the design of the airborne 2-micron pulsed IPDA lidar system; the lidar operation parameters; the wavelength pair selection; laser transmitter energy, pulse rate, beam divergence, double pulse generation and accurate frequency control; detector characterization; telescope design; lidar structure design

  15. Local T2 measurement employing longitudinal Hadamard encoding and adiabatic inversion pulses in porous media.

    PubMed

    Vashaee, S; Newling, B; Balcom, B J

    2015-12-01

    Band selective adiabatic inversion radio frequency pulses were employed for multi-slice T2 distribution measurements in porous media samples. Multi-slice T2 measurement employing longitudinal Hadamard encoding has an inherent sensitivity advantage over slice-by-slice local T2 measurements. The slice selection process is rendered largely immune to B1 variation by employing hyperbolic secant adiabatic inversion pulses, which simultaneously invert spins in several well-defined slices. While Hadamard encoding is well established for local spectroscopy, the current work is the first use of Hadamard encoding for local T2 measurement. PMID:26580063

  16. Local T2 measurement employing longitudinal Hadamard encoding and adiabatic inversion pulses in porous media

    NASA Astrophysics Data System (ADS)

    Vashaee, S.; Newling, B.; Balcom, B. J.

    2015-12-01

    Band selective adiabatic inversion radio frequency pulses were employed for multi-slice T2 distribution measurements in porous media samples. Multi-slice T2 measurement employing longitudinal Hadamard encoding has an inherent sensitivity advantage over slice-by-slice local T2 measurements. The slice selection process is rendered largely immune to B1 variation by employing hyperbolic secant adiabatic inversion pulses, which simultaneously invert spins in several well-defined slices. While Hadamard encoding is well established for local spectroscopy, the current work is the first use of Hadamard encoding for local T2 measurement.

  17. Pulsed-field-gradient measurements of time-dependent gas diffusion

    NASA Technical Reports Server (NTRS)

    Mair, R. W.; Cory, D. G.; Peled, S.; Tseng, C. H.; Patz, S.; Walsworth, R. L.

    1998-01-01

    Pulsed-field-gradient NMR techniques are demonstrated for measurements of time-dependent gas diffusion. The standard PGSE technique and variants, applied to a free gas mixture of thermally polarized xenon and O2, are found to provide a reproducible measure of the xenon diffusion coefficient (5.71 x 10(-6) m2 s-1 for 1 atm of pure xenon), in excellent agreement with previous, non-NMR measurements. The utility of pulsed-field-gradient NMR techniques is demonstrated by the first measurement of time-dependent (i.e., restricted) gas diffusion inside a porous medium (a random pack of glass beads), with results that agree well with theory. Two modified NMR pulse sequences derived from the PGSE technique (named the Pulsed Gradient Echo, or PGE, and the Pulsed Gradient Multiple Spin Echo, or PGMSE) are also applied to measurements of time dependent diffusion of laser polarized xenon gas, with results in good agreement with previous measurements on thermally polarized gas. The PGMSE technique is found to be superior to the PGE method, and to standard PGSE techniques and variants, for efficiently measuring laser polarized noble gas diffusion over a wide range of diffusion times. Copyright 1998 Academic Press.

  18. Indices of cardiovascular function derived from peripheral pulse wave analysis using radial applanation tonometry: a measurement repeatability study.

    PubMed

    Crilly, Mike; Coch, Christoph; Bruce, Margaret; Clark, Hazel; Williams, David

    2007-08-01

    Pulse wave analysis (PWA) using applanation tonometry is a non-invasive technique for assessing cardiovascular function. It produces three important indices: ejection duration index (ED%), augmentation index adjusted for heart rate (AIX@75), and subendocardial viability ratio (SEVR%). The aim of this study was to assess within- and between-observer repeatability of these measurements. After resting supine for 15 minutes, 20 ambulant patients (16 male) in sinus rhythm underwent four PWA measurements on a single occasion. Two nurses (A & B) independently and alternately undertook PWA measurements using the same equipment (Omron HEM-757; SphygmoCor with Millar hand-held tonometer) blind to the other nurse's PWA measurements. Within- and between-observer differences were analysed using the Bland-Altman ;limits of agreement' approach (mean difference +/- 2 standard deviations, 2SD). Mean age was 56 (blood pressure, BP 136/79; pulse rate 64). BP/PWA measurements remained stable during assessment. Based on the average of two PWA measurements the mean +/- 2SD between-observer difference in ED% was 0.3 +/- 2.0; AIX@75 1.0 +/- 3.9; and SEVR% 1.7 +/- 14.2. Based on a single PWA measurement the between-observer difference was ED% 0.3 +/- 3.3; AIX@75 1.7 +/- 6.9; and SEVR% 0.6 +/- 22.6. Within-observer differences for nurse-A were ED% 0.0 +/- 5.4; AIX@75 1.5 +/- 7.0; and SEVR% 1.7 +/- 39.0 (nurse-B: 0.1 +/- 3.8; 0.1 +/- 8.0; and 0.6 +/- 23.3, respectively). PWA demonstrates high levels of repeatability even when used by relatively inexperienced staff and has the potential to be included in the routine cardiovascular assessment of ambulant patients. PMID:17848475

  19. Neutron generator yield measurements using a phoswich detector with the digital pulse shape analysis

    NASA Astrophysics Data System (ADS)

    Barzilov, Alexander; Novikov, Ivan; Womble, Phillip; Heinze, Julian

    2012-03-01

    The phoswich detector designed as a combination of two scintillators with dissimilar pulse shape characteristics that are optically coupled to each other and to a common photomultiplier is used for the simultaneous detection of fast and thermal neutrons. The digital signal processing of detector signals is used. The pulse shape analysis distinguishes the scintillation signals produced by photons, fast neutrons, and thermal neutrons. The phoswich was tested using the photon and neutron sources. We discuss neutron yield measurements for a pulse DT neutron generator. The spatial distribution of fast neutron flux and thermal neutron flux was evaluated for the generator in presence of neutron moderating materials.

  20. Fiber-optic pulsed photothermal radiometry for fast surface-temperature measurements.

    PubMed

    Eyal, O; Scharf, V; Katzir, A

    1998-09-01

    Temperature measurement based on pulsed photothermal radiometry is described. In this technique a body is irradiated by a laser pulse and its temperature is inferred from the shape of the emitted photothermal-signal curve. A prototypical system based on a pulsed CO(2) laser, an IR detector, and IR-transmitting silver halide optical fibers was constructed and used to evaluate the feasibility of this technique. An important feature of the technique is that changes in sample emissivity or geometric factors do not introduce errors in the temperature determination. Theory, simulation, and experimental results are given and discussed. PMID:18286089

  1. On-chip laser Doppler vibrometer for arterial pulse wave velocity measurement

    PubMed Central

    Li, Yanlu; Segers, Patrick; Dirckx, Joris; Baets, Roel

    2013-01-01

    Pulse wave velocity (PWV) is an important marker for cardiovascular risk. The Laser Doppler vibrometry has been suggested as a potential technique to measure the local carotid PWV by measuring the transit time of the pulse wave between two locations along the common carotid artery (CCA) from skin surface vibrations. However, the present LDV setups are still bulky and difficult to handle. We present in this paper a more compact LDV system integrated on a CMOS-compatible silicon-on-insulator substrate. In this system, a chip with two homodyne LDVs is utilized to simultaneously measure the pulse wave at two different locations along the CCA. Measurement results show that the dual-LDV chip can successfully conduct the PWV measurement. PMID:23847745

  2. 2-Micron Pulsed Direct Detection IPDA Lidar for Atmospheric CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Reithmaier, Karl; Remus, Ruben; Singh, Upendra; Johnson, Will; Boyer, Charlie; Fay, James; Johnston, Susan; Murchison, Luke

    2014-01-01

    A 2-micron high energy, pulsed Integrated Path Differential Absorption (IPDA) lidar has been developed for atmospheric CO2 measurements. Development of this lidar heavily leverages the 2-micron laser technologies developed in LaRC over the last decade. The high pulse energy, direct detection lidar operating at CO2 2-micron absorption band provides an alternate approach to measure CO2 concentrations. This new 2-micron pulsed IPDA lidar has been flown in spring of this year for total ten flights with 27 flight hours. It is able to make measurements of the total amount of atmospheric CO2 from the aircraft to the ground or cloud. It is expected to provide high-precision measurement capability by unambiguously eliminating contamination from aerosols and clouds that can bias the IPDA measurement.

  3. Measurement of a piezoelectric d constant for poly(vinylidene fluoride) transducers using pressure pulses

    NASA Astrophysics Data System (ADS)

    Bur, Anthony J.; Roth, Steven C.

    1985-01-01

    The hydrostatic piezoelectric coefficient dh has been measured for biaxially-oriented poly(vinylidene fluoride) transducers using pressure pulses having peak values of 1.8×107 Pa (2600 psi) and a pulse width of approximately 10 ms. For these measurements, the sample was placed in an oil pressure chamber at room temperature and the pressure pulse was initiated by dropping a 16-kg mass onto a plunger in the chamber. Since adiabatic compressional heating accompanies the pressure pulse, temperature compensation of the transducer was necessary. This was achieved by incorporating a thermocouple in the bilaminate configuration of the transducer and by amplifying the thermocouple signal appropriately to account for the pyroelectric response due to adiabatic heating, which was approximately 15% of the transducer signal. The calculation of dh shows that the response of the bilaminate transducer is linear up to 1.8×107 Pa (2600 psi).

  4. A simplified measurement of pulse wave velocity is not inferior to standard measurement in young adults and children.

    PubMed

    Edgell, Heather; Stickland, Michael K; MacLean, Joanna E

    2016-06-01

    The standard measurement of pulse wave velocity (PWV) is restricted by the need for simultaneous tonometry measurements requiring two technicians and expensive equipment, limiting this technique to well-resourced settings. In this preliminary study, we compared a simplified method of pulse wave detection from the finger and toe to pulse wave detection from the carotid and radial arteries using applanation tonometry in children and young adults. We hypothesized that the simplified method of PWV measurement would strongly correlate with the standard measurement in different age groups and oxygen conditions. Participants included (a) boys and girls aged 8-12 years and (b) men and women aged 18-40 years. Participants rested supine while carotid and radial artery pulse waves were measured using applanation tonometry and finger and toe pulse waves were simultaneously collected using a Finometer Midi and a piezo-electric pulse transducer, respectively. These measurements were repeated under hypoxic conditions. Finger-toe PWV measurements were strongly correlated to carotid-radial PWV in adults (R=0.58; P=0.011), but not in children (R=0.056; P=0.610). Finger-toe PWV was sensitive enough to show increases in PWV with age (P<0.0001) and hypoxia in children (P<0.0001) and adults (P=0.003). These results indicate that the simplified measurement of finger-toe PWV strongly correlates with the standard measurement of carotid-radial PWV in adults, but not in children. However, finger-toe PWV can be used in either population to determine changes with hypoxia. PMID:26905286

  5. Absolute atomic oxygen density measurements for nanosecond-pulsed atmospheric-pressure plasma jets using two-photon absorption laser-induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Jiang, C.; Carter, C.

    2014-12-01

    Nanosecond-pulsed plasma jets that are generated under ambient air conditions and free from confinement of electrodes have become of great interest in recent years due to their promising applications in medicine and dentistry. Reactive oxygen species that are generated by nanosecond-pulsed, room-temperature non-equilibrium He-O2 plasma jets among others are believed to play an important role during the bactericidal or sterilization processes. We report here absolute measurements of atomic oxygen density in a 1 mm-diameter He/(1%)O2 plasma jet at atmospheric pressure using two-photon absorption laser-induced fluorescence spectroscopy. Oxygen number density on the order of 1013 cm-3 was obtained in a 150 ns, 6 kV single-pulsed plasma jet for an axial distance up to 5 mm above the device nozzle. Temporally resolved O density measurements showed that there are two maxima, separated in time by 60-70 µs, and a total pulse duration of 260-300 µs. Electrostatic modeling indicated that there are high-electric-field regions near the nozzle exit that may be responsible for the observed temporal behavior of the O production. Both the field-distribution-based estimation of the time interval for the O number density profile and a pulse-energy-dependence study confirmed that electric-field-dependent, direct and indirect electron-induced processes play important roles for O production.

  6. Interglacial Durations

    NASA Astrophysics Data System (ADS)

    Mangili, Clara; McManus, Jerry F.; Raynaud, Dominique

    2014-05-01

    In the context of future global warming induced by human activities, it is essential to assess the role of natural climatic variations. Precise knowledge of the duration of past interglacial periods is fundamental to the understanding of the potential future evolution of the Holocene. Past ice age cycles provide a natural laboratory for exploring the progression and duration of interglacial climate. Palaeorecords from ice, land and oceans extend over the last 800 ka, revealing eight glacial-interglacial cycles, with a range of insolation and greenhouse gas influences. The interglacials display a correspondingly large variety of intensity and duration, thus providing an opportunity for major insights into the mechanisms involved in the behaviour of interglacial climates. A comparison of the duration of these interglacials, however, is often difficult, as the definition of an interglacial depends on the archive that is considered. Therefore, to compare interglacial length and climate conditions from different archives, a consistent definition of interglacial conditions is required, ideally one that is not bound to the method nor to the archive under consideration. Here we present a method to identify interglacials and to calculate their length by mean of a simple statistical approach. We based our method on ~ 400 ka windows of time to determine mean climatic conditions while allowing for the possibility of long term evolution of the climatic baseline. For our study of interglacials of the past 800 ka, we used two windows that largely align with the pre- (800-430 ka ago) and post- (430-0 ka ago) mid-Brunhes event (MBE), although the resulting conclusions are not sensitive to this particular division. We applied this method to the last 800 ka of a few palaeoclimate records: the deuterium ice core (EDC) record as a climatic proxy, the benthic δ18O stack (LR04) as a proxy for sea level/ice volume, ice core (Vostok, EDC) atmospheric CO2 and additional records. Although

  7. Pulse shape measurement by a non-collinear third-order correlation technique

    NASA Astrophysics Data System (ADS)

    Priebe, G.; Janulewicz, K. A.; Redkorechev, V. I.; Tümmler, J.; Nickles, P. V.

    2006-03-01

    A third-order correlator suitable for detailed shape measurements of picosecond laser pulses has been developed. The working principle in both the single shot and the scanning mode is based on detection of the phase-matched difference frequency non-collinear generated signal in a non-linear crystal. This third-order OPA correlator was applied for the characterization of the specifically shaped picosecond laser pulses from the MBI CPA Nd: glass laser system.

  8. Partial discharge current pulses in SF6 and the effect of superposition of their radiometric measurement

    NASA Astrophysics Data System (ADS)

    Reid, Alistair J.; Judd, Martin D.; Stewart, Brian G.; Fouracre, Richard A.

    2006-10-01

    The practical advantages of employing non-contact radio frequency (RF) methods for detecting partial discharges (PDs) in high voltage equipment have led to significant effort being focused on the diagnosis of electrical plants using RF techniques. This has particularly been the case for gas insulated substations, which use sulphur hexafluoride (SF6) as an insulating medium. One of the most important challenges facing RF diagnostics is the problem of relating the RF emissions to some measure of severity of the PD. Previous work has established that the amplitude or energy of RF signals radiated from a PD source is strongly dependent on the rate of change of current in the PD pulse. In this paper, measurements of PD current pulses in SF6 are presented for a point-plane configuration using an extremely wide bandwidth (13 GHz) measurement system. By this means, PD pulse shapes have been recorded with better resolution than has previously been possible and rise times have been measured with a high degree of accuracy. The results show a considerable variation in pulse shape, with the minimum rise time measured being 35 ps. With this high time-domain resolution, we have been able to distinguish features within the PD pulses that will affect the energy of the radiated RF signal. In particular, the current pulses tend to occur in bursts of up to ten individual pulses in as little as 1 ns, which will excite multiple RF signals in rapid succession. The effect of superposition of RF waveforms has been investigated by studying the variation in detected RF energy with respect to the time delay between PD pulses. It was found that when two PDs occur within a short period (< 150 ns) the combined energy of the resulting RF pulse has the potential to vary by ±30% of that resulting from two equivalent PD pulses with a wider pulse spacing (Gt 150 ns). In terms of a practical monitoring system concerned with order-of-magnitude variations; this is not considered to pose a major problem

  9. Blood pressure, pulse rate, and rhythm measurement using ionic polymer-metal composite sensors

    NASA Astrophysics Data System (ADS)

    Keshavarzi, Amid; Shahinpoor, Mohsen; Kim, Kwang J.; Lantz, Jeffrey W.

    1999-05-01

    The need for more enhanced blood pressure (BP), pulse rate and rhythm senors has given rise to the possibility of using ionic polymer-metal composites (IPMCs) sensors. In this study we propose to use the IPMC sensors to measure systolic and diastolic BP, pulse rate and rhythm. The proposed IPMC sensors take advantage of the endo-ionic mobility within the polymer- metal composite by converting normal and shear load inputs into an induced voltage output across the thickness of the IPMC sensor. The fabricated IPMC sensors are suitable to be installed on the inner surface of a cuff and, therefore, both systolic and diastolic BP, pulse rate, and rhythm can be measured. An added benefit is the ability of measuring 'pulse rhythm' which give a more amplified look at heart irregularities which a typical pulse rate sensor is unable to show. Our data shows IPMC sensors can produce consistent and reliable BP readings, pulse rate, and rhythm. Typically, a linear relationship between applied maximum load and induced maximum voltage was obtained. This result can be easily translated into good BP reading.

  10. A non-contact pulse automatic positioning measurement system for traditional Chinese medicine.

    PubMed

    Chen, Ying-Yun; Chang, Rong-Seng; Jwo, Ko-Wen; Hsu, Chung-Chi; Tsao, Chu-Pang

    2015-01-01

    This study is to construct a non-contact pulse automatic positioning measurement system for Traditional Chinese Medicine (TCM) using optical triangulation measurements. The system consists of a linear laser, a CMOS image sensor and image analysis software. The linear laser is projected on the pulse beat location on the wrists; the CMOS image sensor records the process and the software analyzes the images. The program mainly uses the optical centroid and fast Fourier transform (FFT) principles to calculate centroid changes (pulse amplitude changes) from the images taken by the CMOS image sensor. It returns the positions of cun, guan and chi pulses automatically in terms of the amplitudes and the signals are then transformed from the time domain (time-amplitude) into the frequency domain (frequency-amplitude) via FFT to obtain the waveforms and frequencies of the cun, guan and chi pulses. It successfully extracts the data from the TCM pulse reading and can be a medical aid system for TCM. Combining the advantages of optical measurement and computer automation, this system provides a non-contact, easy to operate, fast in detection and low-cost equipment design. PMID:25923936

  11. Non-contact measurement of pulse wave velocity using RGB cameras

    NASA Astrophysics Data System (ADS)

    Nakano, Kazuya; Aoki, Yuta; Satoh, Ryota; Hoshi, Akira; Suzuki, Hiroyuki; Nishidate, Izumi

    2016-03-01

    Non-contact measurement of pulse wave velocity (PWV) using red, green, and blue (RGB) digital color images is proposed. Generally, PWV is used as the index of arteriosclerosis. In our method, changes in blood volume are calculated based on changes in the color information, and is estimated by combining multiple regression analysis (MRA) with a Monte Carlo simulation (MCS) model of the transit of light in human skin. After two pulse waves of human skins were measured using RGB cameras, and the PWV was calculated from the difference of the pulse transit time and the distance between two measurement points. The measured forehead-finger PWV (ffPWV) was on the order of m/s and became faster as the values of vital signs raised. These results demonstrated the feasibility of this method.

  12. Measurement of lake ice thickness with a short-pulse radar system

    NASA Technical Reports Server (NTRS)

    Cooper, D. W.; Mueller, R. A.; Schertler, R. J.

    1976-01-01

    Measurements of lake ice thickness were made during March 1975 at the Straits of Mackinac by using a short-pulse radar system aboard an all-terrain vehicle. These measurements were compared with ice thicknesses determined with an auger. Over 25 sites were explored which had ice thicknesses in the range 29 to 60 cm. The maximum difference between radar and auger measurements was less than 9.8 percent. The magnitude of the error was less than + or - 3.5 cm. The NASA operating short-pulse radar system used in monitoring lake ice thickness from an aircraft is also described.

  13. Inexpensive pulse-train converter measures analog voltage

    NASA Technical Reports Server (NTRS)

    Sturman, J. C.

    1977-01-01

    Converter measures small voltages or currents in presence of very large common-mode voltages (thousands of volts ac or dc). Advantages are low power consumption, transmission via single isolated channel, simplicity, and operation from single-polarity power supply.

  14. Noise sensitivity in frequency-resolved optical-gating measurements of ultrashort pulses

    SciTech Connect

    Fittinghoff, D.N.; DeLong, K.W.; Trebino, R.; Ladera, C.L.

    1995-10-01

    Frequency-resolved optical gating (FROG), a technique for measuring ultrashort laser pulses, involves producing a spectrogram of the pulse and then retrieving the pulse intensity and phase with an iterative algorithm. We study how several types of noise---multiplicative, additive, and quantization---affect pulse retrieval. We define a convergence criterion and find that the algorithm converges to a reasonable pulse field, even in the presence of 10% noise. Specifically, with appropriate filtering, 1% rms retrieval error is achieved for 10% multiplicative noise, 10% additive noise, and as few as 8 bits of resolution. For additive and multiplicative noise the retrieval errors decrease roughly as the square root of the amount of noise. In addition, the background induced in the wings of the pulse by additive noise is equal to the amount of additive noise on the trace. Thus the dynamic range of the measured intensity and phase is limited by a noise floor equal to the amount of additive noise on the trace. We also find that, for best results, a region of zero intensity should surround the nonzero region of the trace. Consequently, in the presence of additive noise, baseline subtraction is important. We also find that Fourier low-pass filtering improves pulse retrieval without introducing significant distortion, especially in high-noise cases. We show that the field errors in the temporal and the spectral domains are equal. Overall, the algorithm performs well because the measured trace contains {ital N}{sup 2} data points for a pulse that has only 2{ital N} degrees of freedom; FROG has built in redundancy. {copyright} {ital 1995} {ital Optical} {ital Society} {ital of} {ital America}.

  15. Variable square pulse vs conventional PFN pumping of Er:YAG laser

    NASA Astrophysics Data System (ADS)

    Nemeš, K.; Lukač, M.; Možina, J.

    2012-04-01

    The influence of the flashlamp pump current pulse shape on Er:YAG laser efficiency and laser rod thermal focusing was studied theoretically and experimentally. Two pulse shapes, PFN (Pulse Forming Network) and VSP (Variable Square Pulse), were considered. Theoretical modeling and experimental measurements show that the pump pulse shape itself does not have a significant influence on the Er:YAG laser efficiency or thermal focusing. Instead, the major parameter influencing Er:YAG laser efficiency and thermal focusing was found to be the overall pulse duration. For PFN pulses, rise and fall times directly define the overall pulse duration, and therefore do have influence on thermal focusing. By contrast, VSP pulse duration is defined by the externally controlled on-time of the switching transistor. For square shaped pulses, short rise and fall times do not have a direct beneficial influence on thermal lensing.

  16. Comparison of dynamic measurements of pulse contour with pulsed heat continuous cardiac output in postoperative cardiac surgical patients.

    PubMed

    Boyle, Martin; Lawrence, John; Belessis, Andrew; Murgo, Margherita; Shehabi, Yahya

    2007-02-01

    Cardiac output (CO) can be measured using bolus thermodilution via a pulmonary artery catheter (PAC) and as continuous cardiac output (CCO), using pulsed heat thermoditution. Pulse contour cardiac output (PCCO) measures continuous CO by analysis of the arterial waveform after calibration with thermodilution CO. The Pulsion Medical Systems (PiCCO system) achieves this by transpulmonary aortic thermodilution (TDtpa). There is uncertainty regarding the agreement between TDtpa, CCO, and PCCO CO measurements in situations of rapid haemodynamic changes. We studied the agreement of the measures by comparing digital recordings of cardiac index (CI) determined by PCCO and CCO (PCCI and CCI, respectively) made during periods of haemodynamic instability. After ethics committee approval we studied four post-coronary artery bypass graft patients, in the immediate postoperative period. Each patient had a 7.5F CCO catheter (Edwards Lifesciences) and a 5F, 20cm PCCO femoral artery catheter. Digital recordings were obtained for the first 12-18 postoperative hours. Six epochs of instability were identified in the first two to three postoperative hours, and at the commencement of inotropic or vasoactive drugs. Notable features, despite frequent PCCO calibrations, were the marked difference of PCCI compared to CCI. In contradistinction, they tracked very closely during a period of stability. Limitations of both methods were noted. Whilst PCCO responded to rapid change, it developed significant error during haemodynmamic instability and requires frequent recalibration. CCO on the other hand has a considerable time lag in responding to changes in CO. The way a monitor measures CO must be taken into account when using the data in clinical management. PMID:17424793

  17. Nitric oxide density measurements in air and air/fuel nanosecond pulse discharges by laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Uddi, M.; Jiang, N.; Adamovich, I. V.; Lempert, W. R.

    2009-04-01

    Laser induced fluorescence is used to measure absolute nitric oxide concentrations in air, methane-air and ethylene-air non-equilibrium plasmas, as a function of time after initiation of a single pulse, 20 kV peak voltage, 25 ns pulse duration discharge. A mixture of NO and nitrogen with known composition (4.18 ppm NO) is used for calibration. Peak NO density in air at 60 Torr, after a single pulse, is ~8 × 1012 cm-3 (~4.14 ppm) occurring at ~250 µs after the pulse, with decay time of ~16.5 ms. Peak NO atom mole fraction in a methane-air mixture with equivalence ratio of phiv = 0.5 is found to be approximately equal to that in air, with approximately the same rise and decay rate. In an ethylene-air mixture (also with equivalence ratio of phiv = 0.5), the rise and decay times are comparable to air and methane-air, but the peak NO concentration is reduced by a factor of approximately 2.5. Spontaneous emission measurements show that excited electronic states N2(C 3Π) and NO(A 2Σ) in air at P = 60 Torr decay within ~20 ns and ~1 µs, respectively. Kinetic modelling calculations incorporating air plasma kinetics complemented with the GRI Mech 3.0 hydrocarbon oxidation mechanism are compared with the experimental data using three different NO production mechanisms. It is found that NO concentration rise after the discharge pulse is much faster than predicted by Zel'dovich mechanism reactions, by two orders of magnitude, but much slower compared with reactions of electronically excited nitrogen atoms and molecules, also by two orders of magnitude. It is concluded that processes involving long lifetime (~100 µs) metastable states, such as N2(X 1Σ,v) and O2(b 1Σ), formed by quenching of the metastable N2(A 3Σ) state by ground electronic state O2, may play a dominant role in NO formation. NO decay, in all cases, is found to be dominated by the reverse Zel'dovich reaction, NO + O → N + O2, as well as by conversion into NO2 in a reaction of NO with ozone.

  18. Influence of timing algorithm on brachialankle pulse wave velocity measurement.

    PubMed

    Sun, Xin; Li, Ke; Ren, Hongwei; Li, Peng; Wang, Xinpei; Liu, Changchun

    2014-01-01

    The baPWV measurement is a non-invasive and convenient technique in an assessment of arterial stiffness. Despite its widespread application, the influence of different timing algorithms is still unclear. The present study was conducted to investigate the influence of six timing algorithms (MIN, MAX, D1, D2, MDP and INS) on the baPWV measurement and to evaluate the performance of them. Forty-five CAD patients and fifty-five healthy subjects were recruited in this study. A PVR acquisition apparatus was built up for baPWV measurement. The baPWV and other related parameters were calculated separately by the six timing algorithms. The influence and performance of the six algorithms was analyzed. The six timing algorithms generate significantly different baPWV values (left: F=29.036, P<0.001; right: F=40.076, P<0.001). In terms of reproducibility, the MAX has significantly higher CV value (≥ 18.6%) than the other methods, while the INS has the lowest CV value (≤ 2.7%). On the performance of classification, the INS produces the highest AUC values (left: 0.854; right: 0.872). The MIN and D2 also have a passable performance (AUC > 0.8). The choice of timing algorithm affects baPWV values and the quality of measurement. The INS method is recommended for baPWV measurement. PMID:24211905

  19. A Target Indirect Thrust Measurement Method of Pulse Detonation Engine

    NASA Astrophysics Data System (ADS)

    Huang, Xiqiao; Xiong, Yuefei; Li, Chao; Zheng, Longxi; Li, Qing

    2015-05-01

    An indirect thrust measurement method based on impulse of a target plate was developed, and a new thrust measurement system (TMS) was successfully designed and constructed. A series of multi-cycle experiments on thrust measurement were conducted to investigate the feasibility of this method with the newly-built indirect TMS. The thrust measurement of PDE was made at different plate target axial positions and operating frequencies. All the experiments were conducted using gasoline as fuel and air as oxidant. The experimental results implied that the thrust of PDE by using the indirect impulse method was a function of the target plate axial position, and there existed an optimum measurement position for PDE with a diameter of 60 mm. The optimum target plate position located at 3.33. According to the experimental results, the thrusts obtained by using indirect TMS were less than the actual values, and so the observed value of thrust was modified in order to make the thrust more reliable. A relative accurate calibration formula depending on the operating frequency was found.

  20. Airborne 2-Micron Double Pulsed Direct Detection IPDA Lidar for Atmospheric CO2 Measurement

    NASA Astrophysics Data System (ADS)

    Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Reithmaier, Karl; Remus, Ruben; Singh, Upendra; Johnson, Will; Boyer, Charlie; Fay, James; Johnston, Susan; Murchison, Luke

    2016-06-01

    An airborne 2-micron double-pulsed Integrated Path Differential Absorption (IPDA) lidar has been developed for atmospheric CO2 measurements. This new instrument has been flown in spring of 2014 for a total of ten flights with 27 flight hours. This IPDA lidar provides high precision measurement capability by unambiguously eliminating contamination from aerosols and clouds that can bias the results.

  1. Short Sleep Duration Measured by Wrist Actimetry Is Associated With Deteriorated Glycemic Control in Type 1 Diabetes

    PubMed Central

    Borel, Anne-Laure; Pépin, Jean-Louis; Nasse, Laure; Baguet, Jean-Philippe; Netter, Sophie; Benhamou, Pierre-Yves

    2013-01-01

    OBJECTIVE Sleep restriction has been associated with deteriorated insulin sensitivity. The effects of short sleep duration have been explored little in patients with type 1 diabetes. This study addresses the question of whether sleep curtailment affects HbA1c levels in patients with type 1 diabetes. RESEARCH DESIGN AND METHODS Seventy-nine adult patients with type 1 diabetes (median age 40 years [IQR 23–49]; 47% men) were recruited to wear a wrist actimetry sensor during 3 consecutive days to assess mean sleep duration during normal daily life. A subsample of 37 patients also performed 24-h ambulatory blood pressure monitoring (ABPM). Medical history, sleep questionnaires, and diabetes-related quality of life (DQOL) were assessed. RESULTS Patients having shorter sleep duration—less than 6.5 h (n = 21)—had higher levels of HbA1c (P = 0.01) than patients with longer sleep duration, above 6.5 h (n = 58). In a multivariable regression model including shorter versus longer sleep duration, diabetes duration, DQOL score, and daily activity, sleep duration was the only variable independently associated with HbA1c (R2 = 10%). In patients who performed 24-h ABPM, patients with a nondipping pattern of blood pressure exhibited shorter sleep duration than patients with a dipping pattern of blood pressure. CONCLUSIONS Shorter sleep duration is associated with higher HbA1c levels in patients with type 1 diabetes, as well as with a nondipping pattern of blood pressure, anticipating a long-term deleterious impact on the risk of microvascular complications. Further studies should test whether extending the duration of sleep may improve both HbA1c and blood pressure in type 1 diabetes. PMID:23715755

  2. Development of a luminous textile for reflective pulse oximetry measurements.

    PubMed

    Krehel, Marek; Wolf, Martin; Boesel, Luciano F; Rossi, René M; Bona, Gian-Luca; Scherer, Lukas J

    2014-08-01

    In this paper, a textile-based sensing principle for long term photopletysmography (PPG) monitoring is presented. Optical fibers were embroidered into textiles such that out-coupling and in-coupling of light was possible. The "light-in light-out" properties of the textile enabled the spectroscopic characterization of human tissue. For the optimization of the textile sensor, three different carrier fabrics and different fiber modifications were compared. The sample with best light coupling efficiency was successfully used to measure heart rate and SpO2 values of a subject. The latter was determined by using a modified Beer-Lambert law and measuring the light attenuation at two different wavelengths (632 nm and 894 nm). Moreover, the system was adapted to work in reflection mode which makes the sensor more versatile. The measurements were additionally compared with commercially available system and showed good correlation. PMID:25136484

  3. Development of a luminous textile for reflective pulse oximetry measurements

    PubMed Central

    Krehel, Marek; Wolf, Martin; Boesel, Luciano F.; Rossi, René M.; Bona, Gian-Luca; Scherer, Lukas J.

    2014-01-01

    In this paper, a textile-based sensing principle for long term photopletysmography (PPG) monitoring is presented. Optical fibers were embroidered into textiles such that out-coupling and in-coupling of light was possible. The “light-in light-out” properties of the textile enabled the spectroscopic characterization of human tissue. For the optimization of the textile sensor, three different carrier fabrics and different fiber modifications were compared. The sample with best light coupling efficiency was successfully used to measure heart rate and SpO2 values of a subject. The latter was determined by using a modified Beer-Lambert law and measuring the light attenuation at two different wavelengths (632 nm and 894 nm). Moreover, the system was adapted to work in reflection mode which makes the sensor more versatile. The measurements were additionally compared with commercially available system and showed good correlation. PMID:25136484

  4. ±25 ppm repeatable measurement of trapezoidal pulses with 5 MHz bandwidth

    NASA Astrophysics Data System (ADS)

    Arpaia, P.; Baccigalupi, C.; Cerqueira Bastos, M.; Martino, M.

    2014-06-01

    High-quality measurements of pulses are nowadays widely used in fields such as radars, pulsed lasers, electromagnetic pulse generators, and particle accelerators. Whilst literature is mainly focused on fast systems for nanosecond regime with relaxed metrological requirements, in this paper, the high-performance measurement of slower pulses in microsecond regime is faced. In particular, the experimental proof demonstration for a 15 MS/s, ±25 ppm repeatable acquisition system to characterize the flat-top of 3 μs rise-time trapezoidal pulses is given. The system exploits a 5 MHz bandwidth circuit for analogue signal processing based on the concept of flat-top removal. The requirements, as well as the conceptual and physical designs are illustrated. Simulation results aimed at assessing the circuit performance are also presented. Finally, an experimental case study on the characterization of a pulsed power supply for the klystrons modulators of the Compact Linear Collider (CLIC) under study at CERN is reported. In particular, the metrological characterization of the prototype in terms of bandwidth, repeatability, and linearity is presented.

  5. Long distance measurement with femtosecond pulses using a dispersive interferometer.

    PubMed

    Cui, M; Zeitouny, M G; Bhattacharya, N; van den Berg, S A; Urbach, H P

    2011-03-28

    We experimentally demonstrate long distance measurements with a femtosecond frequency comb laser using dispersive interferometry. The distance is derived from the unwrapped spectral phase of the dispersed interferometer output and the repetition frequency of the laser. For an interferometer length of 50 m this approach has been compared to an independent phase counting laser interferometer. The obtained mutual agreement is better than 1.5 μm (3×10(-8)), with a statistical averaging of less than 200 nm. Our experiments demonstrate that dispersive interferometry with a frequency comb laser is a powerful method for accurate and non-incremental measurement of long distances. PMID:21451683

  6. Terahertz pulsed imaging in vivo: measurements and processing methods

    NASA Astrophysics Data System (ADS)

    Parrott, Edward P. J.; Sy, Stanley M. Y.; Blu, Thierry; Wallace, Vincent P.; Pickwell-MacPherson, Emma

    2011-10-01

    This paper presents a number of data processing algorithms developed to improve the accuracy of results derived from datasets acquired by a recently designed terahertz handheld probe. These techniques include a baseline subtraction algorithm and a number of algorithms to extract the sample impulse response: double Gaussian inverse filtering, frequency-wavelet domain deconvolution, and sparse deconvolution. In vivo measurements of human skin are used as examples, and a comparison is made of the terahertz impulse response from a number of different skin positions. The algorithms presented enables both the spectroscopic and time domain properties of samples measured in reflection geometry to be better determined compared to previous calculation methods.

  7. Optoelectronic measurement of x-ray synchrotron pulses: A proof of concept demonstration

    SciTech Connect

    Durbin, Stephen M.; Caffee, Marc; Savikhin, Sergei; Mahmood, Aamer; Dufresne, Eric M.; Wen, Haidan; Li, Yuelin

    2013-02-04

    Optoelectronic detection using photoconductive coplanar stripline devices has been applied to measuring the time profile of x-ray synchrotron pulses, a proof of concept demonstration that may lead to improved time-resolved x-ray studies. Laser sampling of current vs time delay between 12 keV x-ray and 800 nm laser pulses reveal the {approx}50 ps x-ray pulse width convoluted with the {approx}200 ps lifetime of the conduction band carriers. For GaAs implanted with 8 MeV protons, a time profile closer to the x-ray pulse width is observed. The protons create defects over the entire depth sampled by the x-rays, trapping the x-ray excited conduction electrons and minimizing lifetime broadening of the electrical excitation.

  8. Single Frequency, Pulsed Laser Diode Transmitter for Dial Water Vapor Measurements at 935nm

    NASA Technical Reports Server (NTRS)

    Switzer, Gregg W.; Cornwell, Donald M., Jr.; Krainak, Michael A.; Abshire, James B.; Rall, Johnathan A. R.

    1998-01-01

    We report a tunable, single frequency, narrow linewidth, pulsed laser diode transmitter at 935.68nm for remote sensing of atmospheric water vapor. The transmitter consists of a CW, tunable, external cavity diode laser whose output is amplified 2OdB using a tapered diode amplifier. The output is pulsed for range resolved DIAL lidar by pulsing the drive current to the diode amplifier at 4kHz with a .5% duty cycle. The output from the transmitter is 36OnJ/pulse and is single spatial mode. It maintains a linewidth of less than 25MHz as its wavelength is tuned across the water vapor absorption line at 935.68nm. The transmitter design and its use in a water vapor measurement will be discussed.

  9. Measuring spin relaxation with standard pulse sequences in the singlet-triplet basis

    NASA Astrophysics Data System (ADS)

    Keevers, T. L.; McCamey, D. R.

    2015-08-01

    Pulsed electrically and optically-detected magnetic resonance are extremely sensitive to changes in the permutation symmetry of weakly-coupled spin pairs, and are well-suited for investigating devices with a small number of spins. However, the change in observable from conventional electron spin resonance modifies the results of standard inductively-detected pulse sequences which are routinely used to obtain phase coherence and lifetimes. Whilst these effects have been discussed for single-pulse experiments, their role in multi-pulse sequences is less clear. Here, we investigate this effect in Hahn echo and inversion-recovery sequences, and show a second set of narrower echoes are produced that distort measurement outcomes. We demonstrate that phase cycling is able to deconvolve the additional echo signals, allowing spin relaxation times to be reliably extracted.

  10. Spatially and Temporally Resolved Atomic Oxygen Measurements in Short Pulse Discharges by Two Photon Laser Induced Fluorescence

    NASA Astrophysics Data System (ADS)

    Lempert, Walter; Uddi, Mruthunjaya; Mintusov, Eugene; Jiang, Naibo; Adamovich, Igor

    2007-10-01

    Two Photon Laser Induced Fluorescence (TALIF) is used to measure time-dependent absolute oxygen atom concentrations in O2/He, O2/N2, and CH4/air plasmas produced with a 20 nanosecond duration, 20 kV pulsed discharge at 10 Hz repetition rate. Xenon calibrated spectra show that a single discharge pulse creates initial oxygen dissociation fraction of ˜0.0005 for air like mixtures at 40-60 torr total pressure. Peak O atom concentration is a factor of approximately two lower in fuel lean (φ=0.5) methane/air mixtures. In helium buffer, the initially formed atomic oxygen decays monotonically, with decay time consistent with formation of ozone. In all nitrogen containing mixtures, atomic oxygen concentrations are found to initially increase, for time scales on the order of 10-100 microseconds, due presumably to additional O2 dissociation caused by collisions with electronically excited nitrogen. Further evidence of the role of metastable N2 is demonstrated from time-dependent N2 2^nd Positive and NO Gamma band emission spectroscopy. Comparisons with modeling predictions show qualitative, but not quantitative, agreement with the experimental data.

  11. Validation study of PulseCO system for continuous cardiac output measurement.

    PubMed

    Berberian, George; Quinn, T Alexander; Vigilance, Deon W; Park, David Y; Cabreriza, Santos E; Curtis, Lauren J; Spotnitz, Henry M

    2005-01-01

    Ultrasonic flow probes have been used to optimize biventricular pacing immediately after cardiopulmonary bypass, improving cardiac output (CO) by 10%; however, flow probes must be removed with chest closure. The PulseCO system (LiDCO Limited, Cambridge, UK) may extend optimization into the postoperative period, but controlled validations have not been reported. Six anesthetized pigs were instrumented for right heart bypass. Flow was varied from 3 to 1 L/min and then back to 3 in 0.5 L/min increments for 60 second intervals. CO was measured by ultrasonic flow probe on the aorta and by PulseCO using a femoral arterial line. PulseCO and flow probe accurately measured CO (PulseCO R2: 0.79-0.95; flow probe R2: 0.96-0.99). At flow of 2 L/min, when the heart was paced 30 bpm over the sinus rate, PulseCO falsely indicated an increase in CO (2.13 vs. 2.30 L/min, p = 0.014). When mean arterial pressure was increased by 20% using a phenylephrine infusion, PulseCO falsely indicated an increase in CO (2.13 vs. 2.47 L/min, p = 0.014). When mean arterial pressure was decreased by 20% using a nitroprusside infusion, PulseCO falsely indicated a decrease in CO (2.13 vs. 1.79 L/min, p = 0.003). PulseCO appears to be useful for assessing acute changes in CO if its limitations are recognized. PMID:15745132

  12. Airborne 2-Micron Double-Pulsed Integrated Path Differential Absorption Lidar for Column CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

    2014-01-01

    Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 millijouls and up to 10 Hz repetition rate. The two laser pulses are separated by 200 microseconds and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micron IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

  13. Generation of runaway electrons and X-ray emission during breakdown of atmospheric-pressure air by voltage pulses with an ∼0.5-μs front duration

    SciTech Connect

    Kostyrya, I. D.; Tarasenko, V. F.

    2015-03-15

    Results are presented from experiments on the generation of runaway electron beams and X-ray emission in atmospheric-pressure air by using voltage pulses with an ∼0.5-μs front duration. It is shown that the use of small-curvature-radius spherical cathodes (or other cathodes with small curvature radii) decreases the intensity of the runaway electron beam and X-ray emission. It is found that, at sufficiently high voltages at the electrode gap (U{sub m} ∼ 100 kV), the gap breakdown, the formation of a spark channel, and the generation of a runaway electron beam occur over less than 10 ns. At high values of U{sub m} behind the anode that were reached by increasing the cathode size and the electrode gap length, a supershort avalanche electron beam with a full width at half-maximum (FWHM) of up to ∼100 ps was detected. At voltages of ∼50 kV, the second breakdown regime was revealed in which a runaway electron beam with an FWHM of ∼2 ns was generated, whereas the FWHM of the X-ray pulse increased to ∼100 ns. It is established that the energy of the bulk of runaway electrons decreases with increasing voltage front duration and is ⩽30 keV in the first regime and ⩽10 keV in the second regime.

  14. Generation of runaway electrons and X-ray emission during breakdown of atmospheric-pressure air by voltage pulses with an ˜0.5-μs front duration

    NASA Astrophysics Data System (ADS)

    Kostyrya, I. D.; Tarasenko, V. F.

    2015-03-01

    Results are presented from experiments on the generation of runaway electron beams and X-ray emission in atmospheric-pressure air by using voltage pulses with an ˜0.5-μs front duration. It is shown that the use of small-curvature-radius spherical cathodes (or other cathodes with small curvature radii) decreases the intensity of the runaway electron beam and X-ray emission. It is found that, at sufficiently high voltages at the electrode gap ( U m ˜ 100 kV), the gap breakdown, the formation of a spark channel, and the generation of a runaway electron beam occur over less than 10 ns. At high values of U m behind the anode that were reached by increasing the cathode size and the electrode gap length, a supershort avalanche electron beam with a full width at half-maximum (FWHM) of up to ˜100 ps was detected. At voltages of ˜50 kV, the second breakdown regime was revealed in which a runaway electron beam with an FWHM of ˜2 ns was generated, whereas the FWHM of the X-ray pulse increased to ˜100 ns. It is established that the energy of the bulk of runaway electrons decreases with increasing voltage front duration and is ⩽30 keV in the first regime and ⩽10 keV in the second regime.

  15. Pulsed EMAT (Electromagnetic Acoustic Transducer) acoustic measurements on a horizontal continuous caster for internal temperature determination

    NASA Astrophysics Data System (ADS)

    Boyd, Donald M.

    1989-10-01

    Development of a Pulsed Electromagnetic Acoustic Transducer (EMAT) through transmission system for acoustic measurements on steel billets up to 1300 C was completed. Laboratory measurements of acoustic velocity were made, and used to determine the average internal temperature of hot stainless and carbon steel billets. Following the success of the laboratory system development, the laboratory EMAT system was subsequently tested successfully at the Baltimore Specialty Steel Co. on a horizontal continuous caster. Details of the sensor system development and the steel plant demonstration results are presented. Future directions for the high temperature pulsed EMAT internal temperature concept are discussed for potential material processing applications.

  16. Single-shot spatiotemporal measurements of high-field terahertz pulses

    SciTech Connect

    van Tilborg, Jeroen; Schroeder, Carl; Toth, Csaba; Geddes, Cameron; Esarey, Eric; Leemans, Wim

    2011-06-17

    The electric field profiles of broad-bandwidth coherent terahertz (THz) pulses, emitted by laser-wakefield-accelerated electron bunches, are studied. The near-single-cycle THz pulses are measured with two single-shot techniques in the temporal and spatial domains. Spectra of 0-6 THz and peak fields up to {approx_equal} 0.4 MV cm{sup -1} are observed. The measured field substructure demonstrates the manifestation of spatiotemporal coupling at focus, which affects the interpretation of THz radiation as a bunch diagnostic and in high-field pump-probe experiments.

  17. Langmuir probe measurements of double-layers in a pulsed discharge

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Crawford, F. W.

    1980-01-01

    Langmuir probe measurements were carried out which confirm the occurrence of double-layers in an argon positive column. Pulsing the discharge current permitted probe measurements to be performed in the presence of the double-layer. Supplementary evidence, obtained from DC and pulsed discharges, indicated that the double-layers formed in the two modes of operation were similar. The double-layers observed were weak and stable; their relation to other classes of double-layers are discussed, and directions for future work are suggested.

  18. Estimating of pulsed electric fields using optical measurements.

    SciTech Connect

    Flanagan, Timothy McGuire; Chantler, Gary R.

    2013-09-01

    We performed optical electric field measurements ion nanosecond time scales using the electrooptic crystal beta barium borate (BBO). Tests were based on a preliminary bench top design intended to be a proofofprinciple stepping stone towards a modulardesign optical Efield diagnostic that has no metal in the interrogated environment. The long term goal is to field a modular version of the diagnostic in experiments on large scale xray source facilities, or similarly harsh environments.

  19. Study on technology of high-frequency pulsed magnetic field strength measurement.

    PubMed

    Chen, Yi-Mei; Liu, Zhi-Peng; Yin, Tao

    2012-01-01

    High-frequency transient weak magnetic field is always involved in researches about biomedical engineering field while common magnetic-field sensors cannot work properly at frequencies as high as MHz. To measure the value of MHz-level weak pulsed magnetic-field strength accurately, this paper designs a measurement and calibration method for pulsed magnetic-field. In this paper, a device made of Nonferromagnetic material was independently designed and applied to pulsed magnetic field measurement. It held an accurately relative position between the magnetic field generating coil and the detecting coil. By applying a sinusoidal pulse to the generator, collecting the induced electromotive force of the detector, the final magnetic field strength was worked out through algorithms written in Matlab according to Faraday's Law. Experiments were carried out for measurement and calibration. Experiments showed that, under good stability and consistency, accurate measurement of magnetic-field strength of a sinepulse magnetic-field can be achieved, with frequency at 0.5, 1, 1.5 MHz and strength level at micro-Tesla. Calibration results carried out a measuring relative error about 2.5%. PMID:23366106

  20. Pulsed, Photonuclear-induced, Neutron Measurements of Nuclear Materials with Composite Shielding

    SciTech Connect

    James Jones; Kevin Haskell; Rich Waston; William Geist; Jonathan Thron; Corey Freeman; Martyn Swinhoe; Seth McConchie; Eric Sword; Lee Montierth; John Zabriskie

    2011-07-01

    Active measurements were performed using a 10-MeV electron accelerator with inspection objects containing various nuclear and nonnuclear materials available at the Idaho National Laboratory’s Zero Power Physics Reactor (ZPPR) facility. The inspection objects were assembled from ZPPR reactor plate materials to evaluate the measurement technologies for the characterization of plutonium, depleted uranium or highly enriched uranium shielded by both nuclear and non-nuclear materials. A series of pulsed photonuclear, time-correlated measurements were performed with unshielded calibration materials and then compared with the more complex composite shield configurations. The measurements used multiple 3He detectors that are designed to detect fission neutrons between pulses of an electron linear accelerator. The accelerator produced 10-MeV bremsstrahlung X-rays at a repetition rate of 125 Hz (8 ms between pulses) with a 4-us pulse width. All inspected objects were positioned on beam centerline and 100 cm from the X-ray source. The time-correlated data was collected in parallel using both a Los Alamos National Laboratory-designed list-mode acquisition system and a commercial multichannel scaler analyzer. A combination of different measurement configurations and data analysis methods enabled the identification of each object. This paper describes the experimental configuration, the ZPPR inspection objects used, and the various measurement and analysis results for each inspected object.

  1. In-situ membrane resistance measurements in PEFC by fast current pulses

    SciTech Connect

    Buechi, F.N.; Scherer, G.G.; Marek, A.

    1994-12-31

    A solid-state current pulse generator for in situ membrane resistance measurements by superimposed square current pulses in polymer electrolyte fuel cells was designed and built. The choice of the measuring technique and of parameters of the instrumentation was based on a critical analysis of the relevant electrochemical and physical processes. The last stage of the generator is located in an active head directly attached to the fuel cell. This permits the generation of 5 A pulses with extremely fast and clean trailing edges (decay time {le} 5 ns), which in turn makes it possible to measure the voltage transient induced by the current decay, with GHz resolution. By measurements in this time window it is possible to accurate separate of the ohmic series resistance of the cell (membrane resistance) from the polarization of the electrochemical interfaces. Because the pulse current path is independent of the d.c. loop, the resistance can be measured independently of the d.c. value, i.e. under high current density conditions. The instrument was tested and the results analyzed for accuracy. Resistances down to 2 m{Omega} can be measured with an error of < 5%.

  2. Prospects for measuring neutron-star masses and radii with X-ray pulse profile modeling

    SciTech Connect

    Psaltis, Dimitrios; Özel, Feryal; Chakrabarty, Deepto E-mail: fozel@email.arizona.edu

    2014-06-01

    Modeling the amplitudes and shapes of the X-ray pulsations observed from hot, rotating neutron stars provides a direct method for measuring neutron-star properties. This technique constitutes an important part of the science case for the forthcoming NICER and proposed LOFT X-ray missions. In this paper, we determine the number of distinct observables that can be derived from pulse profile modeling and show that using only bolometric pulse profiles is insufficient for breaking the degeneracy between inferred neutron-star radius and mass. However, we also show that for moderately spinning (300-800 Hz) neutron stars, analysis of pulse profiles in two different energy bands provides additional constraints that allow a unique determination of the neutron-star properties. Using the fractional amplitudes of the fundamental and the second harmonic of the pulse profile in addition to the amplitude and phase difference of the spectral color oscillations, we quantify the signal-to-noise ratio necessary to achieve a specified measurement precision for neutron star radius. We find that accumulating 10{sup 6} counts in a pulse profile is sufficient to achieve a ≲ 5% uncertainty in the neutron star radius, which is the level of accuracy required to determine the equation of state of neutron-star matter. Finally, we formally derive the background limits that can be tolerated in the measurements of the various pulsation amplitudes as a function of the system parameters.

  3. Measurement of the information velocity in fast- and slow-light optical pulse propagation

    NASA Astrophysics Data System (ADS)

    Stenner, Michael David

    This thesis describes a study of the velocity of information on optical pulses propagating through fast- and slow-light media. In fast- and slow-light media, the group velocity vg is faster than the speed of light in vacuum c (vg > c or vg < 0) or slower than c (0 < vg < c) respectively. While it is largely accepted that optical pulses can travel at these extreme group velocities, the velocity of information encoded on them is still the subject of considerable debate. There are many contradictory theories describing the velocity of information on optical pulses, but no accepted techniques for its experimental measurement. The velocity of information has broad implications for the principle of relativistic causality (which requires that information travels no faster than c) and for modern communications and computation. In this thesis, a new technique for measuring the information velocity vi is described and implemented for fast- and slow-light media. The fast- and slow-light media are generated using modern dispersion-tailoring techniques that use large atomic coherences to generate strong normal and anomalous dispersion. The information velocity in these media can then be measured using information-theoretic concepts by creating an alphabet of two distinct pulse symbols and transmitting the symbols through the media. By performing a detailed statistical analysis of the received information as a function of time, it is possible to calculate vi. This new technique makes it possible for the first time to measure the velocity of information on optical pulses. Applying this technique to fast-light pulses, where vg/c = -0.051 +/- 0.002, it is found that vi /c = 0.4(+0.7--0.2). In the slow-light case, where vg/c = 0.0097 +/- 0.0003, information is found to propagate at vi/c = 0.6. In the slow-light case, the error bars are slightly more complicated. The fast bound is -0.5c (which is faster than positive values) and the slow bound is 0.2c . These results represent the

  4. Airborne Measurements of Atmospheric Methane Using Pulsed Laser Transmitters

    NASA Technical Reports Server (NTRS)

    Numata, Kenji; Riris, Haris; Wu, Stewart; Gonzalez, Brayler; Rodriguez, Michael; Hasselbrack, William; Fahey, Molly; Yu, Anthony; Stephen, Mark; Mao, Jianping; Kawa, Stephan

    2016-01-01

    Atmospheric methane (CH4) is the second most important anthropogenic greenhouse gas with approximately 25 times the radiative forcing of carbon dioxide (CO2) per molecule. At NASA Goddard Space Flight Center (GSFC) we have been developing a laser-based technology needed to remotely measure CH4 from orbit. We report on our development effort for the methane lidar, especially on our laser transmitters and recent airborne demonstration. Our lidar transmitter is based on an optical parametric process to generate near infrared laser radiation at 1651 nanometers, coincident with a CH4 absorption. In an airborne flight campaign in the fall of 2015, we tested two kinds of laser transmitters --- an optical parametric amplifier (OPA) and an optical parametric oscillator (OPO). The output wavelength of the lasers was rapidly tuned over the CH4 absorption by tuning the seed laser to sample the CH4 absorption line at several wavelengths. This approach uses the same Integrated Path Differential Absorption (IPDA) technique we have used for our CO2 lidar for ASCENDS. The two laser transmitters were successfully operated in the NASAs DC-8 aircraft, measuring methane from 3 to 13 kilometers with high precision.

  5. Korotkoff sound versus oscillometric cuff sphygmomanometers: comparison between auscultatory and DynaPulse blood pressure measurements.

    PubMed

    Chio, Shiu-Shin; Urbina, Elaine M; Lapointe, Jeffery; Tsai, Jeffrey; Berenson, Gerald S

    2011-01-01

    Listening to Korotkoff sounds (K-sounds) to determine systolic and diastolic blood pressure (BP) has been the standard for noninvasive BP measurement in medical practices for nearly 100 years. It is the essential tool used for evaluation and assessment of patients with hypertension and risks of cardiovascular diseases (CVD) by physicians and nurses despite limited understanding of the nature of K-sounds. Analyzing cuff oscillometric signals to obtain BP has been the foundation of most digital BP monitors available today. DynaPulse is an oscillometric digital BP monitor that records and analyzes subtle changes of pulse waveforms during the course of a BP measurement while cuff pressure slowly decreases from above systolic to below diastolic. This study compares systolic and diastolic readings obtained by K-sound method following the Bogalusa Heart Study protocol and BP measured by DynaPulse (DP2000A) monitor, in order to better understand the nature and difference between K-sound and oscillometric methods. Analysis of means and differences is applied to BP data collected from 803 subjects examined in the Bogalusa Heart Study. The results indicated: 1) DynaPulse systolic was 9 mm Hg higher (P < .0001) than Phase 1 (K1) systolic, 2) DynaPulse diastolic was 5 mm Hg lower (P < .0001) than Phase 4 (K4), and 3) is less than 1 mm Hg higher than Phase 5 (K5) diastolic (P < .0001), when compared with K-sound auscultatory measurement. Understanding the methods and differences of DynaPulse oscillometric and K-sound BP measurements is important for clinic BP screening and self-BP monitoring, as well as future research to improve hypertension and CVD managements. PMID:21269907

  6. Measurement of (222)Rn by absorption in plastic scintillators and alpha/beta pulse shape discrimination.

    PubMed

    Mitev, Krasimir K

    2016-04-01

    This work demonstrates that common plastic scintillators like BC-400, EJ-200 and SCSF-81 absorb radon and their scintillation pulse decay times are different for alpha- and beta-particles. This allows the application of pulse shape analysis for separation of the pulses of alpha- and beta-particles emitted by the absorbed radon and its progeny. It is shown that after pulse shape discrimination of beta-particles' pulses, the energy resolution of BC-400 and EJ-200 alpha spectra is sufficient to separate the peaks of (222)Rn, (218)Po and (214)Po and allows (222)Rn measurements that are unaffected by the presence of thoron ((220)Rn) in the environment. The alpha energy resolution of SCSF-81 in the experiments degrades due to imperfect collection of the light emitted inside the scintillating fibers. The experiments with plastic scintillation microspheres (PSM) confirm previous findings of other researchers that PSM have alpha-/beta-discrimination properties and show suitability for radon measurements. The diffusion length of radon in BC-400 and EJ-200 is determined. The pilot experiments show that the plastic scintillators are suitable for radon-in-soil-gas measurements. Overall, the results of this work suggest that it is possible to develop a new type of radon measurement instruments which employ absorption in plastic scintillators, pulse-shape discrimination and analysis of the alpha spectra. Such instruments can be very compact and can perform continuous, real-time radon measurements and thoron detection. They can find applications in various fields from radiation protection to earth sciences. PMID:26851823

  7. Frequency-resolved optical gating measurement of ultrashort pulses by using single nanowire.

    PubMed

    Yu, Jiaxin; Liao, Feng; Gu, Fuxing; Zeng, Heping

    2016-01-01

    The use of ultrashort pulses for fundamental studies and applications has been increasing rapidly in the past decades. Along with the development of ultrashort lasers, exploring new pulse diagnositic approaches with higher signal-to-noise ratio have attracted great scientific and technological interests. In this work, we demonstrate a simple technique of ultrashort pulses characterization with a single semiconductor nanowire. By performing a frequency-resolved optical gating method with a ZnO nanowire coupled to tapered optical microfibers, the phase and amplitude of a pulse series are extracted. The generated signals from the transverse frequency conversion process can be spatially distinguished from the input, so the signal-to-noise ratio is improved and permits lower energy pulses to be identified. Besides, since the nanometer scale of the nonlinear medium provides relaxed phase-matching constraints, a measurement of 300-nm-wide supercontinuum pulses is achieved. This system is highly compatible with standard optical fiber systems, and shows a great potential for applications such as on-chip optical communication. PMID:27609521

  8. Pulse compression radar reflectometry to measure electron density in plasma with parasitic reflections

    SciTech Connect

    Li Bin; Li Hong; Chen Zhipeng; Luo Chen; Wang Huihui; Geng Song; Feng Lei; Liu Qiuyan; Liu Wandong

    2008-07-15

    Pulse compression radar reflectometry is used to obtain electron density profile in plasma with parasitic reflections in this article. The pulse compression radar relies on the relation between the temporal width of a pulse and the frequency bandwidth of this pulse: {delta}t{proportional_to}1/{delta}f. So a set of sweep-frequency microwaves within a bandwidth {delta}f can be introduced sequentially into the plasma to obtain the same information as the one obtained by a real pulse. By applying a Fourier transform to the data of reflectivity array in the frequency domain, the temporal response in the time domain is obtained. The limitation of the parasitic reflections on measurement can be eliminated from the temporal response by the method of time gate. This is a prominent advantage when this method is compared to the traditional reflectometry. For this method, an appropriate compromise between the spatial resolution and the electron density resolution is important. Experimental results show that the profile obtained from pulse compression radar reflectometry is similar to that from a double Langmuir probe.

  9. MEASURING THE PULSE OF GRB 090618: A SIMULTANEOUS SPECTRAL AND TIMING ANALYSIS OF THE PROMPT EMISSION

    SciTech Connect

    Basak, Rupal; Rao, A. R. E-mail: arrao@tifr.res.in

    2012-01-20

    We develop a new method for simultaneous timing and spectral studies of gamma-ray burst (GRB) prompt emission and apply it to make a pulse-wise description of the prompt emission of GRB 090618, the brightest GRB detected in the Fermi era. We exploit the large area (and sensitivity) of Swift/Burst Alert Telescope and the wide bandwidth of Fermi/Gamma-ray Burst Monitor to derive the parameters for a complete spectral and timing description of the individual pulses of this GRB, based on the various empirical relations suggested in the literature. We demonstrate that this empirical model correctly describes the other observed properties of the burst, such as the variation of the lag with energy and the pulse width with energy. The measurements also show an indication of an increase in the pulse width as a function of energy at low energies for some of the pulses, which is naturally explained as an off-shoot of some particular combination of the model parameters. We argue that these model parameters, particularly the peak energy at the beginning of the pulse, are the natural choices to be used for correlation with luminosity. The implications of these results for the use of GRBs as standard candles are briefly described.

  10. Frequency-resolved optical gating measurement of ultrashort pulses by using single nanowire

    PubMed Central

    Yu, Jiaxin; Liao, Feng; Gu, Fuxing; Zeng, Heping

    2016-01-01

    The use of ultrashort pulses for fundamental studies and applications has been increasing rapidly in the past decades. Along with the development of ultrashort lasers, exploring new pulse diagnositic approaches with higher signal-to-noise ratio have attracted great scientific and technological interests. In this work, we demonstrate a simple technique of ultrashort pulses characterization with a single semiconductor nanowire. By performing a frequency-resolved optical gating method with a ZnO nanowire coupled to tapered optical microfibers, the phase and amplitude of a pulse series are extracted. The generated signals from the transverse frequency conversion process can be spatially distinguished from the input, so the signal-to-noise ratio is improved and permits lower energy pulses to be identified. Besides, since the nanometer scale of the nonlinear medium provides relaxed phase-matching constraints, a measurement of 300-nm-wide supercontinuum pulses is achieved. This system is highly compatible with standard optical fiber systems, and shows a great potential for applications such as on-chip optical communication. PMID:27609521

  11. Measuring the energy of amplified spontaneous emission (ASE) in a short pulse laser amplifier

    NASA Astrophysics Data System (ADS)

    Iliev, Marin; Adams, Daniel; Greco, Michael; Meier, Amanda; Squier, Jeff; Durfee, Charles

    2010-10-01

    In high-gain pulsed laser amplifiers, amplified spontaneous emission (ASE) tends to limit the gain in single stage fiber amplifiers. Even if ASE is not strong enough to deplete the gain of the amplifier, it still contributes strongly to a low-intensity background output in the amplified signal. The intensity contrast between the amplified short pulse and this background ASE pedestal can be measured with third-order autocorrelation, but this method cannot be used to completely specify the ASE's energy, which is distributed over many nanoseconds. We have developed a novel method that allows us to determine the energy and the spectrum of the ASE. We use a cross polarized wave (XPW) generating crystal such as BaF2 to ``clean up'' the ASE from the short pulse(SP). The input pulse (SP and ASE) and the cross-polarized signal are passed through a birefringent crystal such as sapphire. The relative group velocity difference along each crystal axis results in a delay between both channels. After passing through a polarizer, an interferogram is obtained in a spectrometer. This interferogram results from interference of the XPW pulse with the short-pulse content of the amplifier output, with a background of the ASE spectrum. Fourier analysis yields both the ASE energy and its spectrum.

  12. Accuracy of Modelled Stratospheric Temperatures in the Winter Arctic Vortex from Infra Red Montgolfier Long Duration Balloon Measurements

    NASA Technical Reports Server (NTRS)

    Pommereau, J.-P.; Garnier, A.; Knudson, B. M.; Letrenne, G.; Durand, M.; Cseresnjes, M.; Nunes-Pinharanda, M.; Denis, L.; Newman, P. A.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    The temperature of the stratosphere has been measured in the Arctic vortex every 9-10 minutes along the trajectory of four Infra Red Montgolfier long duration balloons flown for 7 to 22 days during the winters of 1997 and 1999. From a number of comparisons to independent sensors, the accuracy of the measurements is demonstrated to be plus or minus 0.5 K during nighttime and at altitude below 28 km (10 hPa). The performances of the analyses of global meteorological models, European Center for Medium Range Weather Forecasts (ECMWF) 31 and 50 levels, United Kingdom Meteorological Office (UKMO), Data Assimilation Office (DAO), National Climatic Prediction Center (NCEP) and NCEP/NCAR reanalysis, used in photochemical simulations of ozone destruction and interpretation of satellite data, are evaluated by comparison to this large (3500 data points) and homogeneous experimental data set. Most of models, except ECMWF31 in 1999, do show a smal1 average warm bias of between 0 and 1.6 K, with deviations particularly large, up to 20 K at high altitude (5hPa) in stratospheric warming conditions in 1999. Particularly wrong was ECMWF 31 levels near its top level at 10 hPa in 1999 where temperature 25 K colder than the real atmosphere were reported. The average dispersion between models and measurements varies from plus or minus 1.0 to plus or minus 3.0 K depending on the model and the year. It is shown to be the result of three contributions. The largest is a long wave modulation likely caused by the displacement of the temperature field in the analyses compared to real atmosphere. The second is the overestimation of the vertical gradient of temperature particularly in warming conditions, which explains the increase of dispersion from 1997 to 1999. Unexpectedly, the third and smallest (plus or minus 0.6-0.7 K) is the contribution of meso and subgrid scale vertical and horizontal features associated to the vertical propagation of orographic or gravity waves. Compared to other

  13. Noninvasive Method for Measuring Local Pulse Wave Velocity by Dual Pulse Wave Doppler: In Vitro and In Vivo Studies

    PubMed Central

    Wang, Zhen; Yang, Yong; Yuan, Li-jun; Liu, Jie; Duan, Yun-you; Cao, Tie-sheng

    2015-01-01

    Objectives To evaluate the validity and reproducibility of a noninvasive dual pulse wave Doppler (DPWD) method, which involves simultaneous recording of flow velocity of two independent sample volumes with a measurable distance, for measuring the local arterial pulse wave velocity (PWV) through in vitro and in vivo studies. Methods The DPWD mode of Hitachi HI Vision Preirus ultrasound system with a 5–13MHz transducer was used. An in vitro model was designed to compare the PWV of a homogeneous rubber tubing with the local PWV of its middle part measured by DPWD method. In the in vivo study, local PWV of 45 hypertensive patients (25 male, 49.8±3.1 years) and 45 matched healthy subjects (25 male, 49.3±3.0 years) were investigated at the left common carotid artery (LCCA) by DPWD method. Results In the in vitro study, the local PWV measured by DPWP method and the PWV of the homogeneous rubber tubing did not show statistical difference (5.16 ± 0.28 m/s vs 5.03 ± 0.15 m/s, p = 0.075). The coefficient of variation (CV) of the intra- and inter- measurements for local PWV were 3.46% and 4.96%, for the PWV of the homogeneous rubber tubing were 0.99% and 1.98%. In the in vivo study, a significantly higher local PWV of LCCA was found in the hypertensive patients as compared to that in healthy subjects (6.29±1.04m/s vs. 5.31±0.72m/s, P = 0.019). The CV of the intra- and inter- measurements in hypertensive patients were 2.22% and 3.94%, in healthy subjects were 2.07% and 4.14%. Conclusions This study demonstrated the feasibility of the noninvasive DPWD method to determine the local PWV, which was accurate and reproducible not only in vitro but also in vivo studies. This noninvasive echocardiographic method may be illuminating to clinical use. PMID:25786124

  14. Scintillation event energy measurement via a pulse model based iterative deconvolution method

    NASA Astrophysics Data System (ADS)

    Deng, Zhenzhou; Xie, Qingguo; Duan, Zhiwen; Xiao, Peng

    2013-11-01

    This work focuses on event energy measurement, a crucial task of scintillation detection systems. We modeled the scintillation detector as a linear system and treated the energy measurement as a deconvolution problem. We proposed a pulse model based iterative deconvolution (PMID) method, which can process pileup events without detection and is adaptive for different signal pulse shapes. The proposed method was compared with digital gated integrator (DGI) and digital delay-line clipping (DDLC) using real world experimental data. For singles data, the energy resolution (ER) produced by PMID matched that of DGI. For pileups, the PMID method outperformed both DGI and DDLC in ER and counts recovery. The encouraging results suggest that the PMID method has great potentials in applications like photon-counting systems and pulse height spectrometers, in which multiple-event pileups are common.

  15. A heat-pulse flowmeter for measuring minimal discharge rates in boreholes

    USGS Publications Warehouse

    Hess, A.E.

    1982-01-01

    The U.S. Geological Survey has tested a borehole-configured heat-pulse flowmeter which has good low-velocity flow-measuring sensitivity. The flowmeter was tested in the laboratory in 51-, 102-, and 152-millimeter-diameter columns using water velocities ranging from 0.35 to 250 millimeters per second. The heat-pulse flowmeter also was tested in a 15-meter-deep granite test pit with controlled water flow, and in a 58-meter-deep borehole in sedimentary materials. The flowmeter's capability to detect and measure naturally occurring, low-velocity, thermally induced convection currents in boreholes was demonstrated. Further improvements to the heat-pulse-flowmeter system are needed to increase its reliability and improve its response through four-conductor logging cable.

  16. Precision timing measurement of phototube pulses using a flash analog-to-digital converter

    NASA Astrophysics Data System (ADS)

    Bennett, J. V.; Kornicer, M.; Shepherd, M. R.; Ito, M. M.

    2010-10-01

    We present the timing characteristics of the flash ADC readout of the GlueX forward calorimeter, which depends on precise measurement of arrival time of pulses from FEU 84-3 photomultiplier tubes to suppress backgrounds. The tests presented were performed using two different 250 MHz prototype flash ADC devices, one with eight-bit and one with 12-bit sampling depth. All measured time resolutions were better than 1 ns, independent of signal size, which is the design goal for the GlueX forward calorimeter. For pulses with an amplitude of 100 mV the timing resolution is 0.57±0.18 ns, while for 500 mV pulses it is 0.24±0.08 ns.

  17. Method of high precision interval measurement in pulse laser ranging system

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Lv, Xin-yuan; Mao, Jin-jin; Liu, Wei; Yang, Dong

    2013-09-01

    Laser ranging is suitable for laser system, for it has the advantage of high measuring precision, fast measuring speed,no cooperative targets and strong resistance to electromagnetic interference,the measuremen of laser ranging is the key paremeters affecting the performance of the whole system.The precision of the pulsed laser ranging system was decided by the precision of the time interval measurement, the principle structure of laser ranging system was introduced, and a method of high precision time interval measurement in pulse laser ranging system was established in this paper.Based on the analysis of the factors which affected the precision of range measure,the pulse rising edges discriminator was adopted to produce timing mark for the start-stop time discrimination,and the TDC-GP2 high precision interval measurement system based on TMS320F2812 DSP was designed to improve the measurement precision.Experimental results indicate that the time interval measurement method in this paper can obtain higher range accuracy. Compared with the traditional time interval measurement system,the method simplifies the system design and reduce the influence of bad weather conditions,furthermore,it satisfies the requirements of low costs and miniaturization.

  18. In situ attosecond pulse characterization techniques to measure the electromagnetic phase

    NASA Astrophysics Data System (ADS)

    Spanner, M.; Bertrand, J. B.; Villeneuve, D. M.

    2016-08-01

    A number of techniques have been developed to characterize the attosecond emission from high-order-harmonic sources. These techniques are broadly classified as ex situ, where the attosecond pulse train photoionizes a target gas in the presence of an infrared field, and in situ, where the measurement takes place in the medium in which the attosecond pulses are generated. It is accepted that ex situ techniques measure the characteristics of the electromagnetic field, including the phase of the recombination transition moment of the emitting atom or molecule, when the phase of the second medium is known. However, there is debate about whether in situ techniques measure the electromagnetic field, or only the characteristics of the recolliding electron before recombination occurs. We show numerically that in situ measurements are not sensitive to the recombination phase, when implemented in the perturbative regime as originally envisioned, and that they do not measure the electromagnetic phase of the emission.

  19. Development of a Pulsed 2-Micron Integrated Path Differential Absorption Lidar for CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Refaat, Tamer

    2013-01-01

    Atmospheric carbon dioxide (CO2) is an important greenhouse gas that significantly contributes to the carbon cycle and global radiation budget on Earth. Active remote sensing of CO2 is important to address several limitations that contend with passive sensors. A 2-micron double-pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This active remote sensing instrument will provide an alternate approach of measuring atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise ratio level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. Commercial, on the shelf, components are implemented for the detection system. Instrument integration will be presented in this paper as well as a background for CO2 measurement at NASA Langley research Center

  20. 2-micron Double Pulsed IPDA Lidar for Atmospheric CO2 Measurement

    NASA Astrophysics Data System (ADS)

    Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Reithmaier, Karl; Remus, Ruben; Singh, Upendra; Johnson, Will; Boyer, Charlie; Fay, James; Johnston, Susan; Murchison, Luke; Scola, Tory

    2015-04-01

    We have developed a high energy pulsed 2-micron IPDA lidar instrument to measure the atmospheric CO2 column density. The IPDA lidar is operated on the long wavelength wing of R(30) CO2 line at 2050.967 nm (4875.749 cm-1) in the side-line operation mode. The R(30) line is an excellent absorption line for the measurements of CO2 in 2µm wavelength region with regard to the strength of the absorption lines, low susceptibility to atmospheric temperature variability, and freedom from problematic interference with other absorption lines. The Ho:Tm:YLF laser transmitter is designed to be operated in a unique double pulse format that can produce two-pulse pair in 10 Hz operation. Typically, the output energies of the laser transmitter are 100mJ and 45mJ for the first pulse and the second pulse, respectively. We injection seed the first pulse with on-line frequency and the second pulse with off-line frequency. The IPDA lidar instrument size, weight and power consumption were restricted to small research aircraft payload requirements. The airborne IPDA lidar instrument measures the total integrated column content of CO2 from the instrument to the ground but with weighting that can be tuned by controlling the transmitted wavelengths. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. The 2-μm CO2 IPDA lidar airborne demonstration was conducted during March 20, 2014 through April 10, 2014. IPDA lidar airborne flights included various operating and environmental conditions. Environmental conditions included different flight altitude up to 8.3 km, different ground target conditions such as vegetation, soil, ocean, snow and sand and different cloud conditions. Besides, some flights targeted power plant incinerators for investigating the IPDA sensitivity to CO2 plums. The lidar instrument is robust during all of the flights. This paper describes

  1. Psychophysiological Measures of Learning Comfort: Study Groups' Learning Styles and Pulse Changes

    ERIC Educational Resources Information Center

    Holliday, Tacy L.; Said, Sukhaynah H.

    2008-01-01

    This study provided empirical support for tutor-led study groups using a physiological measurement and study survey data. The scope of this preliminary study included determining differences in biology and chemistry study group members' (N = 25) regarding learning styles and pulse rate changes. As hypothesized, there was significant evidence that…

  2. Shock-wave measurements of solids using the long-pulsed laser

    NASA Astrophysics Data System (ADS)

    Uchino, Mazakazu; Kaetsu, Masahide; Mashimo, Tsutomu

    1997-05-01

    The optical measurement system using long-pulsed lasers were constructed for shock-wave measurements and spectroscopy under shock compression of solids. We have produced two types of long-pulsed lasers with no Q-switch for such purposes: Nd:YAG frequency-double laser using an intracavity KTP crystal, and dye laser using a rhodamine 6G. They consisted of doubled-elliptical pump cavity, two zenon flash lamps, and a high-voltage electrical-pulse source. The former one can be used as a light source for a Fabry-Perot type Interferometer (FPI), and the latter one can be used as a constant light source for a luminescence or an absorption spectroscopy and for the inclined-mirror method. The inclined-mirror Hugoniot measurements of some materials were performed by using the long-pulsed dye laser and the mirror- rotating type streak camera. The time resolution was increased by using a narrow width slit and the laser. The velocity-interferometer system for shock-wave measurements using a FPI and the time-resolved optical spectroscopy system using a spectrometer were constructed combined with the Nd:YAG frequency-doubled laser and the dye laser, respectively, and with an image-converter streak camera.

  3. A system for measuring the pulse height distribution of ultrafast photomultipliers

    NASA Technical Reports Server (NTRS)

    Abshire, J. B.

    1977-01-01

    A system for measuring the pulse height distribution of gigahertz bandwidth photomultipliers was developed. This system uses a sampling oscilloscope as a sample-hold circuit and has a bandwidth of 12 gigahertz. Test results are given for a static crossed-filed photomultiplier tested with a demonstration system. Calculations on system amplitude resolution capabilities are included for currently available system components.

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

    SciTech Connect

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

    1995-12-31

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

  5. Signal to Noise Ratio Analysis of the Data from the Pulsed Airborne CO2 Lidar Measurements

    NASA Astrophysics Data System (ADS)

    Sun, X.; Abshire, J. B.; Riris, H.; Allan, G. R.; Hasselbrack, W. E.

    2009-12-01

    We are developing a differential absorption lidar (DIAL) for measuring the CO2 column concentrations from space for the ASCENDS mission. Our technique uses two pulsed laser transmitters to simultaneously measure the total column absorption by CO2 in 1570 nm band and O2 extinction in the Oxygen A-band by periodically stepping the laser wavelength at predetermined wavelengths across the absorption lines. The reflected laser signals from the surface and clouds are collected by the receiver telescope and detected by a set of single photon counting detectors. We used pulsed lasers and time resolved photon detection to distinguish the surface echoes from cloud and aerosol backscattering and to measure the column height. . The total column absorption at a given wavelength is determined from the ratio of the received laser pulse energy to the transmitted energy. The column gas concentrations and the spectral line shape are determined from curve fitting of the column absorptions as a function of the wavelength. We have built an airborne lidar to demonstrate the CO2 column measurement technique from the NASA Lear-25 aircraft. The airborne lidar scans the laser wavelength across the CO2 absorption line in 20 steps. The line scan rate is 450 Hz, the laser pulse energy is 25 uJ, and laser pulse widths are 1 usec. The backscatter photons are collected by a 20 cm telescope and detected by a near infrared photomultiplier tube. The detected photons are binned according to their arrival times with the use of a multichannel scaler. Several airborne measurements were conducted during October and December 2008, and August 2009 with many hours of CO2 column measurement data at the 1571.4, 1572.02 and 1572.33 nm CO2 absorption lines. The measurements were made over a variety of land and water surfaces and some through thin clouds. We also made several improvements to the instrument for the later flights. Measurements from early flights showed the receiver signal and noise levels were

  6. An efficient amplification pulse sequence for measuring chemical shift anisotropy under fast magic-angle spinning.

    PubMed

    Hung, Ivan; Gan, Zhehong

    2011-12-01

    A two-dimensional experiment for measuring chemical shift anisotropy (CSA) under fast magic-angle spinning (MAS) is presented. The chemical shift anisotropy evolution is amplified by a sequence of π-pulses that repetitively interrupt MAS averaging. The amplification generates spinning sideband manifolds in the indirect dimension separated by the isotropic shift along the direct dimension. The basic unit of the pulse sequence is designed based on the magic-angle turning experiment and can be concatenated for larger amplification factors. PMID:21962909

  7. Thermal diffusivity measurements using a pulsed dual-beam thermal lens technique

    NASA Technical Reports Server (NTRS)

    Gupta, M. C.; Hong, S.-D.; Gupta, A.; Moacanin, J.

    1980-01-01

    A novel pulsed dual-beam thermal lens technique for the determination of thermal diffusivity of liquids and solids was developed. In this technique a transient thermal lens is formed in the test specimen by using a dye laser pulse as a heating source and the thermal lens decay is monitored by means of a CW He-Ne laser. The technique is fast and contactless and avoids some of the major difficulties of conventional methods. Thermal diffusivities for water and a polycarbonate plastic were measured and found to be in agreement with literature values. Considerable simplification and minimization of certain errors was achieved by use of a reference material.

  8. A new measurement of the Her X-1 X-ray pulse profile

    NASA Technical Reports Server (NTRS)

    Holt, S. S.; Boldt, E. A.; Rothschild, R. E.; Serlemitsos, P. J.

    1974-01-01

    A triple peaked 1.24 sec. pulse profile in a 1-minute rocket borne exposure to Her X-1 was measured, in contrast to the doublepeaked profiles expected from models which maximize the X ray emission at the magnetic equator of an accreting neutron star. The profile exhibits statistically significant energy dependence, with the emission approximately greater than 12 keV having narrower peaks which lag (by approximately 5% of the pulse period) the corresponding peaks at lower energies. Approximately one third of the total emission from the source is nonpulsed.

  9. Temporal correlation measurements of pulsed dual CO2 lidar returns. [for atmospheric pollution detection

    NASA Technical Reports Server (NTRS)

    Menyuk, N.; Killinger, D. K.

    1981-01-01

    A pulsed dual-laser direct-detection differential-absorption lidar DIAL system, operating near 10.6 microns, is used to measure the temporal correlation and statistical properties of backscattered returns from specular and diffuse topographic targets. Results show that atmospheric-turbulence fluctuations can effectively be frozen for pulse separation times on the order of 1-3 msec or less. The diffuse target returns, however, yielded a much lower correlation than that obtained with the specular targets; this being due to uncorrelated system noise effects and different statistics for the two types of target returns.

  10. Measurement of the laser-pulse group velocity in plasma waveguides.

    PubMed

    van Tilborg, J; Daniels, J; Gonsalves, A J; Schroeder, C B; Esarey, E; Leemans, W P

    2014-06-01

    Electrically discharged plasma channels can guide laser pulses, extending the laser-plasma interaction length to many Rayleigh ranges. In applications such as the laser-plasma accelerator, the laser group velocity in the channel plays a critical role. The laser travel time (and thus the averaged group velocity) was measured through two-pulse frequency-domain interferometry and was found to depend on the on-axis plasma density and laser spot size. The data is in agreement with theory. PMID:25019900

  11. Measurements of the asymmetric, dynamic sheath around a pulse biased sphere immersed in flowing metal plasma

    SciTech Connect

    Anders, Andre; Wu, Hongchen; Anders, Andre

    2008-06-13

    A long-probe technique was utilized to record the expansion and retreat of the dynamic sheath around a spherical substrate immersed in pulsed cathode arc metal plasma. Positively biased, long cylindrical probes were placed on the side and downstream of a negatively pulsed biased stainless steel sphere of 1" (25.4 mm) diameter. The amplitude and width of the negative high voltage pulses (HVP) were 2 kV, 5 kV, 10 kV, and 2 mu s, 4 mu s, 10 mu s, respectively. The variation of the probe (electron) current during the HVP is a direct measure for the sheath expansion and retreat. Maximum sheath sizes were determined for the different parameters of the HVP. The expected rarefaction zone behind the biased sphere (wake) due to the fast plasma flow was clearly established and quantified.

  12. Performance evaluation of quantitative adiabatic (13)C NMR pulse sequences for site-specific isotopic measurements.

    PubMed

    Thibaudeau, Christophe; Remaud, Gérald; Silvestre, Virginie; Akoka, Serge

    2010-07-01

    (2)H/(1)H and (13)C/(12)C site-specific isotope ratios determined by NMR spectroscopy may be used to discriminate pharmaceutically active ingredients based on the synthetic process used in production. Extending the Site-specific Natural Isotope Fractionation NMR (SNIF-NMR) method to (13)C is highly beneficial for complex organic molecules when measurements of (2)H/(1)H ratios lead to poorly defined molecular fingerprints. The current NMR methodology to determine (13)C/(12)C site-specific isotope ratios suffers from poor sensitivity and long experimental times. In this work, several NMR pulse sequences based on polarization transfer were evaluated and optimized to measure precise quantitative (13)C NMR spectra within a short time. Adiabatic 180 degrees (1)H and (13)C pulses were incorporated into distortionless enhancement by polarization transfer (DEPT) and refocused insensitive nuclei enhanced by polarization transfer (INEPT) to minimize the influence of 180 degrees pulse imperfections and of off-resonance effects on the precision of the measured (13)C peak areas. The adiabatic DEPT sequence was applied to draw up a precise site-specific (13)C isotope profile of ibuprofen. A modified heteronuclear cross-polarization (HCP) experiment featuring (1)H and (13)C spin-locks with adiabatic 180 degrees pulses is also introduced. This sequence enables efficient magnetization transfer across a wide (13)C frequency range although not enough for an application in quantitative (13)C isotopic analysis. PMID:20527737

  13. Individual loss distribution measurement in 32-branched PON using pulsed pump-probe Brillouin analysis.

    PubMed

    Takahashi, Hiroshi; Ito, Fumihiko; Kito, Chihiro; Toge, Kunihiro

    2013-03-25

    We describe loss distribution measurement in a passive optical network (PON) using pulsed pump-probe Brillouin analysis. A preliminary experiment is demonstrated using a 32-branched PON constructed in the laboratory. We analyze the signal to noise ratio of this measurement and show that the method can realize a 25 dB dynamic range in 90 seconds (10000 times averaging), with an event location resolution of 10 m, and a fiber length identification resolution of 2 m. PMID:23546056

  14. Single-pulse, laser-saturated fluorescence measurements of OH in turbulent nonpremixed flames

    NASA Technical Reports Server (NTRS)

    Lucht, R. P.; Sweeney, D. W.; Laurendeau, N. M.; Drake, M. C.; Lapp, M.; Pitz, R. W.

    1984-01-01

    A single-pulse, laser-saturated fluorescence technique has been developed for absolute OH concentration measurements with a temporal resolution of 2 nsec, a spatial resolution of less than 0.1 cu mm, and an estimated accuracy of + or - 30 percent. It has been applied in laminar, transitional, and turbulent hydrogen-air diffusion flames, providing the first reported quantitative measurements of average values, rms fluctuations, and probability-density functions of OH-radical concentration in nonpremixed flames.

  15. 14C AMS measurements of the bomb pulse in N- and S-hemisphere tropical trees

    NASA Astrophysics Data System (ADS)

    Murphy, J. O.; Lawson, E. M.; Fink, D.; Hotchkis, M. A. C.; Hua, Q.; Jacobsen, G. E.; Smith, A. M.; Tuniz, C.

    1997-03-01

    The 14C bomb-pulse signature has been measured by AMS on cross-dateable teak samples from N- and S-hemisphere locations in the tropics. Excellent agreement is found with the atmospheric 14C content in the period 1955 to 1980 for the respective hemispheres. These results demonstrate that 14C measurements can be used to facilitate growth rate determinations in tropical trees.

  16. The use of pulsed neutron diffraction to measure strain in composites

    SciTech Connect

    Bourke, M.A.M.; Goldstone, J.A.; Shi, N.; Gray, G.T. III; James, M.R.; Todd, R.I.

    1994-03-01

    Neutron diffraction is a technique for measuring strain in crystalline materials. It is non destructive, phase discriminatory and more penetrating than X rays. Pulsed neutron sources (in contrast with steady state reactor sources) are particularly appropriate for examining heterogeneous materials or for recording the polycrystalline response of all lattice reflections. Several different aspects of composite behavior can be characterized and examples are given of residual strain measurements, strain relaxation during heating, applied loading, and determination of the strain distribution function.

  17. a New Approach of Dynamic Blood Pressure Measurement Based on the Time Domain Analysis of the Pulse Wave

    NASA Astrophysics Data System (ADS)

    Zimei, Su; Wei, Xu; Hui, Yu; Fei, Du; Jicun, Wang; Kexin, Xu

    2009-08-01

    In this study the pulse wave characteristics were used as a new approach to measure the human blood pressure. Based the principle of pulse wave and theory of the elastic vascular, the authors analyzed the characteristic of the pulse waveforms and revealed the characteristics points which could be used to represent the blood pressure. In this investigation the relevant mathematical feature was used to identify the relationship between the blood pressure and pulse wave parameters in a more accurate way. It also provided an experimental basis to carry out continuing non-invasive blood pressure monitoring using the pulse wave method.

  18. Simultaneous measurement of two ultrashort laser pulses from a single spectrogram in a single shot

    SciTech Connect

    Kane, D.J.; Rodriguez, G.; Taylor, A.J.; Clement, T.S. ||

    1997-04-01

    Frequency-resolved optical gating (FROG) is a technique that produces a spectrogram of an ultrashort laser pulse. The intensity and phase of the ultrashort laser pulse can be determined through solving for the phase of the spectrogram with an iterative, phase-retrieval algorithm. This work presents a new phase-retrieval algorithm that retrieves both the probe and the gate pulses independently by converting the FROG phase-retrieval problem to an eigenvector problem. The new algorithm is robust and general. It is tested theoretically by use of synthetic data sets and experimentally by use of single-shot, polarization-gate FROG. We independently and simultaneously characterize the electric field amplitude and phase of a pulse (probe) that was passed though 200 mm of BK7 glass and the amplitude of an unchanged pulse (gate) from an amplified Ti:sapphire laser. When the effect of the 200 mm of BK7 glass was removed mathematically from the probe, there was good agreement between the measured gate and the calculated, prechirped probe. {copyright} 1997 Optical Society of America

  19. Pulse transmission measurements for determining near optimal profile gradings in multimode borosilicate optical fibers.

    PubMed

    Cohen, L G

    1976-07-01

    Dispersive differences between B(2)O(3) and SiCO(2) constituents make nonparabolic profiles optimal equalizers of intermodal group delays in fibers with graded B(2)O(3)-SiO(2) cores and uniform B(2)O(3)-SiO(2) cladding. Pulse dispersion measurements were correlated with profile shapes in a systematic study of multimode fibers with near power law gradients. Far field spatial ray filters were used to diagnose impulse response shapes so that new fibers could be fabricated with closer-to-optimal profile gradients. One of the fibers had an alpha approximately 1.77 power law exponent that was nearly optimal for lambda = 907.5-nm wavelength and caused 2sigma = 0.26-nsec/km full rms output pulse spreading. When expected material dispersion effects were deconvolved from the output pulse spreading, the resultant pulse width was approximately 75 times less than the result expected for a comparable step-index fiber. This is the largest pulse width reduction reported yet. PMID:20165269

  20. Conductivities of pig dermis and subcutaneous fat measured with rectangular pulse electrical current

    SciTech Connect

    Cheng, K. |; Tarjan, P.P.; Mertz, P.M.

    1996-12-31

    The authors examined experimentally the relationship between perpendicular and tangential electrical conductivities, {sigma}, and peak current density J, in pig skin dermis and subcutaneous fat specimens by using a four-electrode measuring system with rectangular pulse electrical current (RPEC). They also investigated the relationship of the conductivity, {sigma}, vs. pulse rate, f. The rates were selected at 8, 32, 64, and 128 pulses per second (pps), and the pulse width was fixed at 140 {micro}s. These values are often used in vivo to enhance cutaneous regeneration with RPEC stimulation. It was found that the conductivities may be approximated to be {sigma}{sub d} = [{sigma}{sub dx}{sigma}{sub dy}{sigma}{sub dz}] = [0.38 S/m 0.38 S/m 0.27 S/m] for the skin dermis and {sigma}{sub f} = [{sigma}{sub fx}{sigma}{sub fy}{sigma}{sub fz}] = [0.074 S/m 0.074 S/m 0.045 S/m] for the subcutaneous fat in the conditions of this experiment. These findings implies that the conductivities of the pig skin dermis and subcutaneous fat are anisotropic, i.e., {sigma}{sub x} = {sigma}{sub y} {ne} {sigma}{sub z}. It was also found that the conductivities are independent of current density and pulse rate in the current range from 20 {micro}A/cm{sup 2} to 120 mA/cm{sup 2}.