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Sample records for pulse duration measurements

  1. A simple technique for individual picosecond laser pulse duration measurements

    NASA Technical Reports Server (NTRS)

    Smith, W. L.; Bechtel, J. H.

    1976-01-01

    We describe here a simple nonlinear optic technique for the measurement of the duration of individual picosecond pulses. The accuracy and relative simplicity of the technique increase with the number of pulses measured. An experimental test of the basis of the technique is described.

  2. Measuring the effective pulse duration of nanosecond and femtosecond laser pulses for laser-induced damage experiments

    NASA Astrophysics Data System (ADS)

    Zorila, Alexandru; Rusen, Laurentiu; Stratan, Aurel; Nemes, George

    2013-05-01

    We report on our approach to measure the quantity named effective pulse duration as defined in the ISO 21254-1:2011 standard, which deals with laser-induced damage (LID) threshold measurements. The approach is applied to measure pulses from two laser sources: an injection-seeded electro-optically Q-switched Nd:YAG nanosecond system with 10-Hz pulse repetition frequency, and a fully integrated Ti:sapphire laser with 150-400 fs and 2-kHz pulse repetition frequency. For comparison, the full-width-half-maximum (FWHM) of the same pulses is also measured. The analysis and description of the measurement process, the experimental results, and the corresponding uncertainties are presented. A smaller combined uncertainty is obtained for the effective pulse duration than for the FWHM-defined pulse duration for each time scale involved in experiments. This suggests that the effective pulse duration is the appropriate parameter to characterize the pulse duration in LID experiments.

  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. 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.

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

    PubMed

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

    2012-08-01

    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 ~25 ps. The minimum duration at half maximum of one peak in the pulses with two peaks can reach ~25 ps too.

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

  9. 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.

  10. 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.

  11. 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.

  12. Pulsed infrared laser irradiation of biological tissue: effect of pulse duration and repetition rate

    NASA Astrophysics Data System (ADS)

    Jansen, E. Duco; Chundru, Ravi K.; Samanani, Salim A.; Tibbetts, Todd A.; Welch, Ashley J.

    1993-07-01

    Pulsed laser ablation is a trade off between minimizing thermal damage (for relatively long pulses) and mechanical damage (for relatively short pulses) to tissue adjacent to the ablation crater. Often it is not known what the optimal laser parameters are for a specific application, since clinically used parameters have at least partially been dictated by physical limitations of the laser devices. We recently obtained a novel type of cryogenic continuous wave holmium:YAG laser ((lambda) equals 2.09 micrometers ) with a galvanometric drive outcouple mirror that acts as a Q-switch. This unique device provides pulse repetition rates from a few Hz up to kHz and the pulse length is variable from microsecond(s) to ms. The effect of pulse duration and repetition rate on the thermal response of chicken breast is documented using temperature measurements with a thermal camera. We varied the pulse width from 10 microsecond(s) to 5 ms and fond that these pulse durations can be considered impulses of thermalized optical energy. In this paper some theoretical considerations of the pulse length will be described that support the experimental data. It was also found that even at 1 pulse per second thermal superposition occurs, indicating a much longer thermal relaxation time than predicted by a simple time constant model.

  13. CW seeded optical parametric amplifier providing wavelength and pulse duration tunable nearly transform limited pulses.

    PubMed

    Hädrich, S; Gottschall, T; Rothhardt, J; Limpert, J; Tünnermann, A

    2010-02-01

    An optical parametric amplifier that delivers nearly transform limited pulses is presented. The center wavelength of these pulses can be tuned between 993 nm and 1070 nm and, at the same time, the pulse duration is varied between 206 fs and 650 fs. At the shortest pulse duration the pulse energy was increased up to 7.2 microJ at 50 kHz repetition rate. Variation of the wavelength is achieved by applying a tunable cw seed while the pulse duration can be varied via altering the pump pulse duration. This scheme offers superior flexibility and scaling possibilities.

  14. Pulse laser assist optical tweezers (PLAT) with long-duration pulse laser

    NASA Astrophysics Data System (ADS)

    Maeda, Saki; Sugiura, Tadao; Minato, Kotaro

    2011-07-01

    Optical tweezers is a technique to trap and to manipulate micron sized objects under a microscope by radiation pressure force exerted by a laser beam. Optical tweezers has been utilized for single-molecular measurements of force exerted by molecular interactions and for cell palpation. To extend applications of optical tweezers we have developed a novel optical tweezers system combined with a pulse laser. We utilize a pulse laser (Q-switched Nd: YAG laser, wavelength of 1064 nm) to assist manipulations by conventional optical tweezers with a continuous wave (CW) laser. The pulse laser beam is introduced into the same optics for conventional optical tweezers. In principle, instantaneous radiation force is proportional to instantaneous power of laser beam. As a result, pulse laser beam generates strong instantaneous force on an object to be manipulated. If the radiation force becomes strong enough to get over an obstacle structure and/or to be released from adhesion, the object will be free from these difficulties. We investigate the effect of pulse laser assistance with changing pulse duration of the laser. We report optimum pulse duration of 100 ns to 200 ns deduced from motion analysis of a particle in a beam spot. Our goal is to realize in-vivo manipulation and operation of a cell. For this purpose we need to reduce light energy of pulse laser beam and to avoid laser induced breakdown caused by strong light field. So we have developed a pulse laser with 160-ns pulse duration and have confirmed that availability on manipulation of living cells.

  15. Driver sensitivity to brake pulse duration and magnitude.

    PubMed

    Lee, J D; McGehee, D V; Brown, T L; Nakamoto, J

    2007-06-01

    Adaptive cruise control (ACC) requires that the driver intervene in situations that exceed the capability of ACC. A brake pulse might provide a particularly compatible means of alerting the driver to situations in which the acceleration authority of the ACC has been exceeded. This study examined the sensitivity of the driver to brake pulses of five different amplitudes (0.01-0.025 g) and five different durations (50-800 ms). Drivers were sensitive to accelerations as low as 0.015 g. Pulse duration interacted with pulse amplitude, such that moderate duration pulses were more detectable than long and short duration pulses at intermediate levels of pulse amplitude. A power function with an exponent of 1.0 accounted for 99% of the variance in drivers' sensitivity to pulse amplitude; however, a power function with an exponent of 0.23 accounted for only 70% of the variance in drivers' sensitivity to pulse duration. These results can help designers create ACC algorithms and develop brake pulse warnings.

  16. Pulse-duration dependent sequential double ionization by elliptically polarized laser pulses

    NASA Astrophysics Data System (ADS)

    Tong, Aihong; Deng, Yongju; Liu, Dan

    2016-05-01

    Using a fully classical model, we have studied sequential double ionization of argon driven by elliptically polarized laser pulses at intensities well in the over-barrier ionization region. The results show that the joint electron momentum distributions in the minor elliptical direction depend strongly on the pulse duration. From pulse number N = 4 to 10, the clustering regions of the joint electron momentum increase with the pulse duration. For even larger pulse durations, the clustering region does not increase further but the population of the joint electron momentum in these regions changes with the pulse duration. Back analysis of double ionization trajectories shows the phenomenon of multiple ionization bursts and the pulse duration-dependent multiple ionization bursts of the second electron is responsible for the evolution of the joint electron momentum distribution with the pulse duration.

  17. Influence of pulse duration on the plasma characteristics in high-power pulsed magnetron discharges

    SciTech Connect

    Konstantinidis, S.; Dauchot, J.P.; Ganciu, M.; Ricard, A.; Hecq, M.

    2006-01-01

    High-power pulsed magnetron discharges have drawn an increasing interest as an approach to produce highly ionized metallic vapor. In this paper we propose to study how the plasma composition and the deposition rate are influenced by the pulse duration. The plasma is studied by time-resolved optical emission and absorption spectroscopies and the deposition rate is controlled thanks to a quartz microbalance. The pulse length is varied between 2.5 and 20 {mu}s at 2 and 10 mTorr in pure argon. The sputtered material is titanium. For a constant discharge power, the deposition rate increases as the pulse length decreases. With 5 {mu}s pulse, for an average power of 300 W, the deposition rate is {approx}70% of the deposition rate obtained in direct current magnetron sputtering at the same power. The increase of deposition rate can be related to the sputtering regime. For long pulses, self-sputtering seems to occur as demonstrated by time-resolved optical emission diagnostic of the discharge. In contrary, the metallic vapor ionization rate, as determined by absorption measurements, diminishes as the pulses are shortened. Nevertheless, the ionization rate is in the range of 50% for 5 {mu}s pulses while it lies below 10% in the case of a classical continuous magnetron discharge.

  18. Electropermeabilization of mammalian cells to macromolecules: control by pulse duration.

    PubMed Central

    Rols, M P; Teissié, J

    1998-01-01

    Membrane electropermeabilization to small molecules depends on several physical parameters (pulse intensity, number, and duration). In agreement with a previous study quantifying this phenomenon in terms of flow (Rols and Teissié, Biophys. J. 58:1089-1098, 1990), we report here that electric field intensity is the deciding parameter inducing membrane permeabilization and controls the extent of the cell surface where the transfer can take place. An increase in the number of pulses enhances the rate of permeabilization. The pulse duration parameter is shown to be crucial for the penetration of macromolecules into Chinese hamster ovary cells under conditions where cell viability is preserved. Cumulative effects are observed when repeated pulses are applied. At a constant number of pulses/pulse duration product, transfer of molecules is strongly affected by the time between pulses. The resealing process appears to be first-order with a decay time linearly related to the pulse duration. Transfer of macromolecules to the cytoplasm can take place only if they are present during the pulse. No direct transfer is observed with a postpulse addition. The mechanism of transfer of macromolecules into cells by electric field treatment is much more complex than the simple diffusion of small molecules through the electropermeabilized plasma membrane. PMID:9726943

  19. 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.

  20. Influence of pulse duration on mechanical effects after laser-induced breakdown in water

    NASA Astrophysics Data System (ADS)

    Noack, Joachim; Hammer, Daniel X.; Noojin, Gary D.; Rockwell, Benjamin A.; Vogel, Alfred

    1998-06-01

    The influence of the pulse duration on the mechanical effects following laser-induced breakdown in water was studied at pulse durations between 100 fs and 100 ns. Breakdown was generated by focusing laser pulses into a cuvette containing distilled water. The pulse energy corresponded to 6-times breakdown threshold energy. Plasma formation and shock wave emission were studied photographically. The plasma photographs show a strong influence of self-focusing on the plasma geometry for femtosecond pulses. Streak photographic recording of the shock propagation in the immediate vicinity of the breakdown region allowed the measurement of the near-field shock pressure. At the plasma rim, shock pressures between 3 and 9 GPa were observed for most pulse durations. The shock pressure rapidly decays proportionally to r-(2⋯3) with increasing distance r from the optical axis. At a 6 mm distance of the shock pressure has dropped to (8.5±0.6) MPa for 76 ns and to <0.1 MPa for femtosecond pulses. The radius of the cavitation bubble is reduced from 2.5 mm (76 ns pulses) to less than 50 μm for femtosecond pulses. Mechanical effects such as shock wave emission and cavitation bubble expansion are greatly reduced for shorter laser pulses, because the energy required to produce breakdown decreases with decreasing pulse duration, and because a larger fraction of energy is required to overcome the heat of vaporization with femtosecond pulses.

  1. A regenerative CO2 amplifier with controlled pulse duration

    NASA Astrophysics Data System (ADS)

    Apollonov, V. V.; Kazakov, K. Kh.; Sorochenko, V. R.; Shakir, Iu. A.

    1991-03-01

    The paper reports the development of a regenerative TEA CO2 amplifier with the pulse duration in a train controlled within the range from 10 to 40 ns, the interval between the pulses amounting to 110 ns and their total energy amounting to 4 J. Laser radiation screening by an optical-air-breakdown plasma in a lens telescope focus was used to form the injected pulse. Good reproduction of the temporal parameters of the injected pulse was achieved by virtue of the injection of radiation from a frequency stabilized CW CO2-laser into the master oscillator.

  2. Pulse duration dependence of atomic sequential double ionization by circular laser pulses

    NASA Astrophysics Data System (ADS)

    Tong, Aihong; Chen, Liangyuan; Li, Yingbin

    2016-09-01

    Using classical ensemble method, we have investigated the pulse duration dependence of sequential double ionization (SDI) of Ar atoms driven by circularly polarized laser pulses. The results show that the ion momentum distribution of Ar atoms depends strongly on the pulse duration. As the pulse duration increases, the ion momentum distribution changes from single-ring to double-ring structure, and finally to the single-ring structure. Back analysis of double ionization trajectories shows that the variation of the ring structure originates from the dependence of the ionization time of the second electron on the pulse duration. Moreover, our calculations clearly manifest the subcycle electron emission in sequential double ionization by circularly polarized laser pulses.

  3. Local field effect as a function of pulse duration

    SciTech Connect

    Novitsky, Denis V.

    2010-07-15

    In this brief report we give semiclassical consideration to the role of pulse duration in the observation of local field effects in the regime of optical switching. We show that the main parameter governing local field influence is the ratio of peak Rabi frequency corresponding to medium inversion and Lorentz frequency of the medium. To obtain significant local field effect, this parameter should be near unity that is valid only for long enough pulses. We also discuss the role of relaxation and pulse shape in this process.

  4. 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

  5. Influence of pulse duration on ultrashort laser pulse ablation of biological tissues.

    PubMed

    Kim, B M; Feit, M D; Rubenchik, A M; Joslin, E J; Celliers, P M; Eichler, J; Da Silva, L B

    2001-07-01

    Ablation characteristics of ultrashort laser pulses were investigated for pulse durations in the range of 130 fs-10 ps. Tissue samples used in the study were dental hard tissue (dentin) and water. We observed differences in ablation crater morphology for craters generated with pulse durations in the 130 fs-1 ps and the 5 ps-10 ps range. For the water experiment, the surface ablation and subsequent propagation of stress waves were monitored using Mach-Zehnder interferometry. For 130 fs-1 ps, energy is deposited on the surface while for longer pulses the beam penetrates into the sample. Both studies indicate that a transition occurs between 1 and 5 ps.

  6. Ultracold atom interferometry with pulses of variable duration

    NASA Astrophysics Data System (ADS)

    Ivannikov, Valentin

    2017-03-01

    We offer interferometry models for thermal ensembles with one-body losses and the phenomenological inclusion of perturbations covering most of the thermal atom experiments. A possible extension to the many-body case is briefly discussed. The Ramsey pulses are assumed to have variable durations and the detuning during the pulses is distinguished from the detuning during evolution. Consequently, the pulses are not restricted to resonant operation and give more flexibility to optimize the interferometer to particular experimental conditions. On this basis another model is devised in which the contrast loss due to the unequal one-body population decays is canceled by the application of a nonstandard splitting pulse. For the importance of its practical implications, an analogous spin-echo model is also provided. The developed models are suitable for the analysis of atomic clocks and a broad range of sensing applications; they are particularly useful for trapped-atom interferometers.

  7. Modeling of ablation threshold dependence on pulse duration for dielectrics with ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Sun, Mingying; Zhu, Jianqiang; Lin, Zunqi

    2017-01-01

    We present a numerical model of plasma formation in ultrafast laser ablation on the dielectrics surface. Ablation threshold dependence on pulse duration is predicted with the model and the numerical results for water agrees well with the experimental data for pulse duration from 140 fs to 10 ps. Influences of parameters and approximations of photo- and avalanche-ionization on the ablation threshold prediction are analyzed in detail for various pulse lengths. The calculated ablation threshold is strongly dependent on electron collision time for all the pulse durations. The complete photoionization model is preferred for pulses shorter than 1 ps rather than the multiphoton ionization approximations. The transition time of inverse bremsstrahlung absorption needs to be considered when pulses are shorter than 5 ps and it can also ensure the avalanche ionization (AI) coefficient consistent with that in multiple rate equations (MREs) for pulses shorter than 300 fs. The threshold electron density for AI is only crucial for longer pulses. It is reasonable to ignore the recombination loss for pulses shorter than 100 fs. In addition to thermal transport and hydrodynamics, neglecting the threshold density for AI and recombination could also contribute to the disagreements between the numerical and the experimental results for longer pulses.

  8. Reciprocity in long pulse duration laser interactions with polymers

    NASA Astrophysics Data System (ADS)

    Marchant, A. L.; Snelling, H. V.

    2012-05-01

    The laser irradiation of polyimide Kapton HN (PI), polyetheretherketone (PEEK), polyethyleneterephthalate (PET) and polypropylene (PP) by long pulse, radio frequency excited, CO2 laser radiation has been studied. In the pulse duration range 47-757 µs the minimum pulse energy required to damage the surface is found to be independent of exposure time. Hence, the threshold fluence is also independent of pulse duration; the same effect is achieved through the application of long pulses at low irradiance as shorter ones at higher irradiance. The values of these threshold fluences have been found to be 8.15 J cm-2, 5.36 J cm-2, 3.39 J cm-2 and 9.63 J cm-2 for PI, PEEK, PET and PP, respectively. The details of this behaviour have been analysed through calculations of the laser-induced temperature rise and the application of an Eyring-type rate law for the thermal decomposition of polyimide and PEEK and by considering the melting points of PP and PET.

  9. Progress toward a microsecond duration, repetitively pulsed, intense- ion beam

    SciTech Connect

    Davis, H.A.; Olson, J.C.; Reass, W.A.; Coates, D.M.; Hunt, J.W.; Schleinitz, H.M.; Lovberg, R.H.; Greenly, J.B.

    1996-07-01

    A number of intense ion beams applications are emerging requiring repetitive high-average-power beams. These applications include ablative deposition of thin films, rapid melt and resolidification for surface property enhancement, advanced diagnostic neutral beams for the next generation of Tokamaks, and intense pulsed-neutron sources. We are developing a 200-250 keV, 15 kA, 1 {mu}s duration, 1-30 Hz intense ion beam accelerator to address these applications.

  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.

  11. 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.

  12. Characteristics of moderate current vacuum discharge triggered by multipicosecond and nanosecond duration laser pulses

    SciTech Connect

    Moorti, A.; Kumbhare, S.R.; Naik, P.A.; Gupta, P.D.; Romanov, I.V.; Korobkin, Yu.V.; Rupasov, A.A.; Shikanov, A.S.

    2005-02-15

    A comparative study of the characteristics of moderate-current ({approx}10 kA), low-energy ({<=}20 J) vacuum discharge triggered by multipicosecond and nanosecond duration laser pulses is performed. Temporal profiles of the x-ray emission, discharge current, and anode voltage measured in vacuum discharge created between a planar titanium cathode and a conical point-tip anode are observed to be quite different for the two regimes of the laser pulse duration. While cathode plasma jet pinching is clearly observed in the discharge created by low-energy ({approx}5 mJ), 27 ps full width at half-maximum (FWHM) laser pulses, a feeble pinching occurred for 4 ns (FWHM) laser pulses only above a threshold energy of {approx}250 mJ. In addition to the multiple K-shell x-ray pulses emitted from the titanium anode up to 100 ns, evidence of a much harder x-ray component (h{nu}>100 keV) is also seen in the discharge triggered by picosecond laser pulses.

  13. Influence of excitation pulse duration of dielectric barrier discharges on biomedical applications

    NASA Astrophysics Data System (ADS)

    Hirschberg, J.; Omairi, T.; Mertens, N.; Helmke, A.; Emmert, S.; Viöl, W.

    2013-04-01

    Two dielectric barrier discharges created in atmospheric pressure air were compared to investigate influences of excitation pulse duration on plasma parameters. A plasma source with a pulsed excitation and pulse durations in the µs range as well as a source with pulse durations in the ns range were investigated. An aluminum plate with skin lipids of the stratum corneum on the one hand and an aluminum needle without lipids for operating in the single filamentary mode on the other hand were used as opposite electrodes. The optical emission spectroscopy was arranged to determine the rotational and vibrational temperatures by comparing experimental with simulated spectra. Vibrational temperatures were calculated in a range 2200-2600 K, rotational temperatures were measured from 300 up to 600 K. In addition, the electron temperatures (7-15 eV) and the reduced electric fields (280-800 Td) were estimated. Electric parameters were detected by both current and voltage measurements with a resulting range 200-500 mW of dissipated power.

  14. The Nature of Emission from Optical Breakdown Induced by Pulses of fs and ns Duration

    SciTech Connect

    Carr, C W; Feit, M D; Rubenchik, A M; Demange, P; Kucheyev, S; Shirk, M D; Radousky, H B; Demos, S G

    2004-11-09

    Spectral emission from optical breakdown in the bulk of a transparent dielectric contains information about the nature of the breakdown medium. We have made time resolved measurements of the breakdown induced emission caused by nanosecond and femtosecond infrared laser pulses. We previously demonstrated that the emission due to ns pulses is blackbody in nature allowing determination of the fireball temperature and pressure during and after the damage event. The emission due to femtosecond pulse breakdown is not blackbody in nature; two different spectral distributions being noted. In one case, the peak spectral distribution occurs at the second harmonic of the incident radiation, in the other the distribution is broader and flatter and presumably due to continuum generation. The differences between ns and fs breakdown emission can be explained by the differing breakdown region geometries for the two pulse durations. The possibility to use spectral emission as a diagnostic of the emission region morphology will be discussed.

  15. 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.

  16. Anodal Transcranial Pulsed Current Stimulation: The Effects of Pulse Duration on Corticospinal Excitability

    PubMed Central

    2015-01-01

    The aim is to investigate the effects of pulse duration (PD) on the modulatory effects of transcranial pulsed current (tPCS) on corticospinal excitability (CSE). CSE of the dominant primary motor cortex (M1) of right first dorsal interosseous muscle was assessed by motor evoked potentials, before, immediately, 10, 20 and 30 minutes after application of five experimental conditions: 1) anodal transcranial direct current stimulation (a-tDCS), 2) a-tPCS with 125 ms pulse duartion (a-tPCSPD = 125), 3) a-tPCS with 250 ms pulse duration (a-tPCSPD = 250), 4) a-tPCS with 500 ms pulse duration (a-tPCSPD = 500) and 5) sham a-tPCS. The total charges were kept constant in all experimental conditions except sham condition. Post-hoc comparisons indicated that a-tPCSPD = 500 produced larger CSE compared to a-tPCSPD = 125 (P<0.0001), a-tPCSPD = 250 (P = 0.009) and a-tDCS (P = 0.008). Also, there was no significant difference between a-tPCSPD = 250 and a-tDCS on CSE changes (P>0.05). All conditions except a-tPCSPD = 125 showed a significant difference to the sham group (P<0.006). All participants tolerated the applied currents. It could be concluded that a-tPCS with a PD of 500ms induces largest CSE changes, however further studies are required to identify optimal values. PMID:26177541

  17. 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.

  18. Multiplexer and time duration measuring circuit

    DOEpatents

    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.

  19. Copper bromide vapour laser with an output pulse duration of up to 320 ns

    SciTech Connect

    Gubarev, F A; Fedorov, K V; Evtushenko, G S; Fedorov, V F; Shiyanov, D V

    2016-01-31

    We report the development of a copper bromide vapour laser with an output pulse duration of up to 320 ns. To lengthen the pulse, the discharge current was limited using a compound switch comprising a pulsed hydrogen thyratron and a tacitron. This technique permits limiting the excitation of the working levels at the initial stage of the discharge development to lengthen the inversion lifetime. The longest duration of a laser pulse was reached in tubes 25 and 50 mm in diameter for a pulse repetition rate of 2 – 4 kHz. (lasers and laser beams)

  20. Investigation on the impact of pulse duration for laser induced lithotripsy

    NASA Astrophysics Data System (ADS)

    Sroka, Ronald; Kiris, Tugba; Fiedler, Sebastian; Scheib, Gabriel; Kuznetsova, Julia; Pongratz, Thomas

    2014-03-01

    Objective: In-vitro investigation of Ho:YAG-laser induced stone fragmentation was performed to identify potential impacts of different pulse durations on stone fragmentation characteristics. Materials and Methods: An innovative Ho:YAG laser system (Swiss LaserClast, EMS S.A., Nyon, Switzerland) with selectable long- or short pulse mode was tested with regard to its fragmentation properties. The pulse duration depends on the specific laser parameter used. Fragmentation tests (hand held, hands free, single pulse induced crater) on artificial BEGO-Stones and fiber burn back tests were performed under reproducible experimental conditions. Additionally, the repulsion of long versus short laser pulses was compared using the pendulum set-up. Results: Differences in fragmentation rates between the two pulse duration regimes were seen. The difference was, however, not statistically significant. Using long pulse mode, the fiber burn back is nearly negligible while in short pulse mode an increased burn back was seen. The results of the pendulum test showed that the deviation induced by the momentum of shorter pulses is increased compared to longer pulses. Conclusion: Long pulse-mode showed reduced side effects like repulsion and fiber burn back in comparison to short pulse-mode while fragmentation rates remained at a comparable level. Lower push back and reduced burn back of longer laser pulses may results in better clinical outcome of laser lithotripsy and more convenient handling during clinical use.

  1. 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).

  2. 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.

  3. Point source of UV-radiation with a frequency of 1 khz and short pulse duration

    NASA Astrophysics Data System (ADS)

    Baksht, E. Kh.; Tarasenko, V. F.; Shut'ko, Yu. V.; Erofeev, M. V.

    2012-04-01

    Radiation of the discharge plasma from a nanosecond breakdown in a nonuniform electric field of short interelectrode gaps is investigated. Voltage pulses with incident wave amplitude of ~10 kV, pulse duration of ~1 ns (FWHM), and pulse front duration of ~0.2 ns are used. It is demonstrated that for pulsed-periodic breakdown of the gap 0.5 mm long in air at atmospheric pressure, the main contribution to plasma radiation give lines of the electrode material and the continuum, and the maximum radiation intensity is registered in the region of 200-300 nm, where ~40% of total radiation energy is concentrated.

  4. Dependence the Integrated Energy of the Electromagnetic Response from Excitation Pulse Duration for Epoxy Samples With Sand Filler

    NASA Astrophysics Data System (ADS)

    Surzhikov, V. P.; Demikhova, A. A.

    2017-01-01

    Results of research of influence of the excitation pulse duration on the parameters of the electromagnetic response of epoxy samples with filler the quartz sand presented in the paper. The electric component of a response was registered by the capacitive sensors using a differential amplifier. Measurements were carried out at two frequencies of the master generator of 65 kHz and 74 kHz. The pulse duration was changing from 10 to 100 microseconds. The stepped sort of dependence of the integrated oscillations energy in the response from duration of the excitation pulse was discovered. The conclusion was made about the determining role of the normal oscillations in formation of such dependence.

  5. The measurement and comparison of jet characteristics of surgical pulse lavage devices.

    PubMed

    Morgan, J; Holder, G; Desoutter, G

    2003-01-01

    The characteristics of pulse waveform, pulse duration, pulse frequency, impact force/pressure, and flow rate of 4 commercially available pulse lavage devices are measured and compared. Validation of the measurements obtained is provided by a laboratory system that generates and measures precise jet waveforms. However, the value of the devices studied awaits clinical trials.

  6. Pulse flux measuring device

    DOEpatents

    Riggan, William C.

    1985-01-01

    A device for measuring particle flux comprises first and second photodiode detectors for receiving flux from a source and first and second outputs for producing first and second signals representing the flux incident to the detectors. The device is capable of reducing the first output signal by a portion of the second output signal, thereby enhancing the accuracy of the device. Devices in accordance with the invention may measure distinct components of flux from a single source or fluxes from several sources.

  7. Ultrashort Two-Photon-Absorption Laser-Induced Fluorescence in Nanosecond-Duration, Repetitively Pulsed Discharges

    NASA Astrophysics Data System (ADS)

    Schmidt, Jacob Brian

    Absolute number densities of atomic species produced by nanosecond duration, repetitively pulsed electric discharges are measured by two-photon absorption laser-induced fluorescence (TALIF). Relatively high plasma discharge pulse energies (=1 mJ/pulse) are used to generate atomic hydrogen, oxygen, and nitrogen in a variety of discharge conditions and geometries. Unique to this work is the development of femtosecond-laser-based TALIF (fs-TALIF). Fs-TALIF offers a number of advantages compared to more conventional ns-pulse-duration laser systems, including better accuracy of direct quenching measurements in challenging environments, significantly reduced photolytic interference including photo-dissociation and photo-ionization, higher signal and increased laser-pulse bandwidth, the ability to collect two-dimensional images of atomic species number densities with far greater spatial resolution compared with more conventional diagnostics, and much higher laser repetition rates allowing for more efficient and accurate measurements of atomic species number densities. In order to fully characterize the fs-TALIF diagnostic and compare it with conventional ns-TALIF, low pressure (100 Torr) ns-duration pulsed discharges are operated in mixtures of H2, O2, and N2 with different buffer gases including argon, helium, and nitrogen. These discharge conditions are used to demonstrate the capability for two-dimensional imaging measurements. The images produced are the first of their kind and offer quantitative insight into spatially and temporally resolved kinetics and transport in ns-pulsed discharge plasmas. The two-dimensional images make possible comparison with high-fidelity plasma kinetics models of the presented data. The comparison with the quasi-one-dimensional kinetic model show good spatial and temporal agreement. The same diagnostics are used at atmospheric pressure, when atomic oxygen fs-TALIF is performed in an atmospheric-pressure plasma jet (APPJ). Here, the

  8. 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.

  9. 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

  10. Influence Pulse Duration Methodical Error of Determination of Thermal Translucent Materials Laser Flash Method

    NASA Astrophysics Data System (ADS)

    Katz, Mark M.; Katz, Ilija M.

    2016-02-01

    The analysis of errors in the determination of thermal diffusivity of a typical semiconductor material - Germany, due to radiative energy transfer in the heated layer of material, under conditions consistent with the implementation of the method under the influence of the laser pulse on the surface of the collimated laser pulse of finite duration.

  11. The effect of finite diffusion gradient pulse duration on fibre orientation estimation in diffusion MRI.

    PubMed

    Yeh, Chun-Hung; Tournier, J-Donald; Cho, Kuan-Hung; Lin, Ching-Po; Calamante, Fernando; Connelly, Alan

    2010-06-01

    An essential step for fibre-tracking is the accurate estimation of neuronal fibre orientations within each imaging voxel, and a number of methods have been proposed to reconstruct the orientation distribution function based on sampling three-dimensional q-space. In the q-space formalism, very short (infinitesimal) gradient pulses are the basic requirement to obtain the true spin displacement probability density function. On current clinical MR systems however, the diffusion gradient pulse duration (delta) is inevitably finite due to the limit on the achievable gradient intensity. The failure to satisfy the short gradient pulse (SGP) requirement has been a recurrent criticism for fibre orientation estimation based on the q-space approach. In this study, the influence of a finite delta on the DW signal measured as a function of gradient direction is described theoretically and demonstrated through simulations and experimental models. Our results suggest that the current practice of using long delta for DW imaging on human clinical MR scanners, which is enforced by hardware limitations, might in fact be beneficial for estimating fibre orientations. For a given b-value, the prolongation of delta is advantageous for estimating fibre orientations for two reasons: first, it leads to a boost in DW signal in the transverse plane of the fibre. Second, it stretches out the shape of the measured diffusion profile, which improves the contrast between DW orientations. This is especially beneficial for resolving crossing fibres, as this contrast is essential to discriminate between different fibre directions.

  12. Investigating the effects of laser intensity and pulse duration on 6.7-nm BEUV emission from Gadolinium plasma

    NASA Astrophysics Data System (ADS)

    Cummins, Thomas; Otsuka, Takamitsu; Yugami, Noboru; Jiang, Weihua; Endo, Akira; Li, Bowen; O'Gorman, Colm; Dunne, Padraig; Sokell, Emma; O'Sullivan, Gerry; Higashiguchi, Takeshi

    2012-01-01

    In this work we present results on the influence of laser pulse duration and irradiating power density on the conversion efficiency (CE) and the ion energy of gadolinium (Gd) laser produced plasmas. Three lasers were used with 10 ns, 150 ps and 140 fs pulse durations. By varying the lasers output energies, experiments could be carried out for a power density range of 1011 - 1015 W/cm2. A maximum CE of 0.4% was achieved within a 0.6% bandwidth in 2π steradians using the picosecond laser. A faraday cup was used to calculate ion yield and time of flight measurements of each laser. The picosecond laser also showed a reduction in the ion time of flight measurements compared with the nanosecond pulse.

  13. Note: Emittance measurements of intense pulsed proton beam for different pulse length and repetition rate

    SciTech Connect

    Miracoli, R.; Gammino, S.; Celona, L.; Mascali, D.; Castro, G.; Gobin, R.; Delferriere, O.; Adroit, G.; Senee, F.; Ciavola, G.

    2012-05-15

    The high intensity ion source (SILHI), in operation at CEA-Saclay, has been used to produce a 90 mA pulsed proton beam with pulse length and repetition rates suitable for the European Spallation Source (ESS) linac. Typical r-r{sup '} rms normalized emittance values smaller than 0.2{pi} mm mrad have been measured for operation in pulsed mode (0.01 < duty cycle < 0.15 and 1 ms < pulse duration < 10 ms) that are relevant for the design update of the Linac to be used at the ESS in Lund.

  14. Reducing the duration of broadband excitation pulses using optimal control with limited RF amplitude.

    PubMed

    Skinner, Thomas E; Reiss, Timo O; Luy, Burkhard; Khaneja, Navin; Glaser, Steffen J

    2004-03-01

    Combining optimal control theory with a new RF limiting step produces pulses with significantly reduced duration and improved performance for a given maximum RF amplitude compared to previous broadband excitation by optimized pulses (BEBOP). The resulting pulses tolerate variations in RF homogeneity relevant for standard high-resolution NMR probes. Design criteria were transformation of Iz-->Ix over resonance offsets of +/-20kHz and RF variability of +/-5%, with a pulse length of 500 micros and peak RF amplitude equal to 17.5 kHz. Simulations transform Iz to greater than 0.995 Ix, with phase deviations of the final magnetization less than 2 degrees, over ranges of resonance offset and RF variability that exceed the design targets. Experimental performance of the pulse is in excellent agreement with the simulations. Performance tradeoffs for yet shorter pulses or pulses with decreased digitization are also investigated.

  15. 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.

  16. 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.

  17. Resonant transfer of large momenta from finite-duration pulse sequences

    NASA Astrophysics Data System (ADS)

    Fekete, J.; Chai, S.; Gardiner, S. A.; Andersen, M. F.

    2017-03-01

    We experimentally investigate the atom optics kicked particle at quantum resonance using finite duration kicks. Even though the underlying process is quantum interference, it can be well described by an ɛ -pseudoclassical model. The ɛ -pseudoclassical model agrees well with our experiments for a wide range of parameters. We investigate the parameters yielding maximal momentum transfer to the atoms and find that this occurs in the regime where neither the short pulse approximation nor the Bragg condition is valid. Nonetheless, the momentum transferred to the atoms can be predicted using a simple scaling law, which provides a powerful tool for choosing optimal experimental parameters. We demonstrate this in a measurement of the Talbot time (from which h /M can be deduced), in which we coherently split atomic wave functions into superpositions of momentum states that differ by 200 photon recoils. Our work may provide a convenient way to implement large momentum difference beam splitters in atom interferometers.

  18. Are long stimulus pulse durations the answer to improving spatial resolution in retinal prostheses?

    PubMed Central

    Petoe, Matthew A.

    2016-01-01

    Retinal prostheses can provide artificial vision to patients with degenerate retinae by electrically stimulating the remaining inner retinal neurons. The evoked perception is generally adequate for light localization, but of limited spatial resolution owing to the indiscriminate activation of multiple retinal cell types, leading to distortions in the perceived image. Here we present a perspective on a recent work by Weitz and colleagues who demonstrate a focal confinement of retinal ganglion cell (RGC) activation when using extended pulse durations in the stimulation waveform. Using real-time calcium imaging, they provide evidence that long pulse durations selectively stimulate inner retinal neurons, whilst avoiding unwanted axonal activations. The application of this stimulation technique may provide enhanced spatial resolution for retinal prosthesis users. These experiments provide a robust analysis of the effects of increasing pulse duration and introduce the potential for alternative stimulation paradigms in retinal prostheses. PMID:27942525

  19. Emission from Polymethyl Methacrylate Irradiated by a Beam of Runaway Electrons of Subnanosecond Pulse Durations

    NASA Astrophysics Data System (ADS)

    Baksht, E. Kh.; Burachenko, A. G.; Beloplotov, D. V.; Tarasenko, V. F.

    2016-08-01

    Spectral and amplitude-temporal characteristics of emission from polymethyl methacrylate (fiberglass, PMMA) irradiated with a beam of runaway electrons of subnanosecond duration are investigated. It is found that at the beam current pulse duration within 200-600 ps at half maximum and the beam current density 10-200 A/cm2, the intensity maximum is registered at the wavelength ~490 nm and the emission pulse FWHM in the visible spectrum is ~1.5 ns at the half width. It is shown that the main contribution into the emission comes from luminescence.

  20. Pulse dynamics of dissipative soliton resonance with large duration-tuning range in a fiber ring laser.

    PubMed

    Luo, Zhi-Chao; Cao, Wen-Jun; Lin, Zhen-Bin; Cai, Ze-Rong; Luo, Ai-Ping; Xu, Wen-Cheng

    2012-11-15

    The pulse dynamics operating in dissipative soliton resonance (DSR) region is experimentally investigated in a fiber ring laser. With the increase of pump power, the pulse profile transit from sech-like to rectangular shape was observed. The generated pulse in DSR region exhibits the conventional soliton spectrum with sideband generation. The duration-tuning range of the rectangular pulse is up to the cavity roundtrip time. Particularly, during the process of pulse duration broadening it was found that the rectangular pulse would trap a weak pulse generated from cw background. The obtained results may be useful for better understanding the DSR phenomenon.

  1. 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.

  2. 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.

  3. 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

  4. Influence of the Nd:YAG laser pulse duration on the temperature of primary enamel.

    PubMed

    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/mm(2). 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.

  5. Influence of the Pulse Duration in the Anthropomorphic Test Device (ATD) Lower-Leg Loading Mechanics

    DTIC Science & Technology

    2015-08-01

    mitigating floor mat, the Finite Element Analysis ( FEA ) was conducted in various loading conditions. Through the FEA’s results, the pulse-duration...1 2.2 Loading Conditions in the FEA .......................................................................................... 4 2.3 Lower...3.1 FEA Results ......................................................................................................................... 9 3.2

  6. Simulation of the Melting Volume in Thin Molybdenum Films as a Function of the Laser Pulse Duration

    NASA Astrophysics Data System (ADS)

    Sotrop, J.; Domke, M.; Kersch, A.; Huber, H. P.

    The interaction of a laser pulse with molybdenum is studied over a wide range of pulse durations from 5 fs to 100 ps using the two-temperature-model (TTM) at constant energy density. The TTM is used to calculate the electron and lattice temperature dynamics and the resulting melting volume. The results show, the maximum melting volume is reached at a pulse duration of 10 ps. The electron heat transfer is dominant for the ultra-short pulse regime below 10 ps, while the lattice heat transfer is influenced by longer pulse durations.

  7. 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.

  8. Comparison of membrane electroporation and protein denature in response to pulsed electric field with different durations.

    PubMed

    Huang, Feiran; Fang, Zhihui; Mast, Jason; Chen, Wei

    2013-05-01

    In this paper, we compared the minimum potential differences in the electroporation of membrane lipid bilayers and the denaturation of membrane proteins in response to an intensive pulsed electric field with various pulse durations. Single skeletal muscle fibers were exposed to a pulsed external electric field. The field-induced changes in the membrane integrity (leakage current) and the Na channel currents were monitored to identify the minimum electric field needed to damage the membrane lipid bilayer and the membrane proteins, respectively. We found that in response to a relatively long pulsed electric shock (longer than the membrane intrinsic time constant), a lower membrane potential was needed to electroporate the cell membrane than for denaturing the membrane proteins, while for a short pulse a higher membrane potential was needed. In other words, phospholipid bilayers are more sensitive to the electric field than the membrane proteins for a long pulsed shock, while for a short pulse the proteins become more vulnerable. We can predict that for a short or ultrashort pulsed electric shock, the minimum membrane potential required to start to denature the protein functions in the cell plasma membrane is lower than that which starts to reduce the membrane integrity.

  9. Light pulse duration differentially regulates mouse locomotor suppression and phase shifts.

    PubMed

    Morin, Lawrence P; Studholme, Keith M

    2014-10-01

    Brief exposure of mice to nocturnal light causes circadian rhythm phase shifts, simultaneously inducing locomotor suppression, a drop in body temperature, and associated sleep. The exact nature of the relationship between these light-induced responses is uncertain, although locomotor suppression and phase shift magnitudes are related to stimulus irradiance. Whether stimulus duration has similar effects is less clear. Here, the relationship between stimulus duration and response magnitude was evaluated further using 100 µW/cm(2) white light-emitting diode pulses administered for 30, 300, 1200, or 3000 sec. The results show that, in general, shorter pulses yielded smaller responses and larger pulses yielded larger responses. However, the 300-sec pulse failed to augment locomotor suppression compared with the effect of a 30-sec pulse (44.7 ± 4.8 vs 40.6 ± 2.0 min) but simultaneously induced much larger phase shifts (1.28 ± 0.20 vs 0.52 ± 0.11 h). The larger phase shifts induced by the 300-sec stimulus did not differ from those induced by either the 1200- or 3000-sec pulses (1.43 ± 0.10 and 1.30 ± 0.17 h, respectively). The results demonstrate differential photic regulation of the two response types. Pulses ranging from 300 to 3000 sec produce equal phase shifts (present data); pulses ranging from 30 to 600 sec produce equal locomotor suppression levels. Greater suppression can occur additively in response to pulses of 1200 sec or more (present data), but this is not true for phase shifts. Nocturnal light appears to trigger a fixed duration event, locomotor suppression, or phase shift, with the latter followed by a light-refractory interval during which locomotor suppression can additively increase. The results also provide further support for the view that temporal integration of photic energy applies, at best, across a limited set of stimulus durations for both light-induced locomotor suppression/sleep and phase shift regulation.

  10. 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.

  11. 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

  12. Effects of pulse duration and areal density on ultrathin foil acceleration

    SciTech Connect

    Zhang Xiaomei; Shen Baifei; Ji Liangliang; Wang Fengchao; Wen Meng; Wang Wenpeng; Xu Jiancai; Yu Yahong

    2010-06-15

    The influence of laser pulse duration and areal density of target in the interaction of a circularly polarized pulse with an ultrathin overdense foil is investigated. One-dimensional particle-in-cell simulation shows that with an appropriate laser-pulse rising front, the light pressure acceleration regime is effective even though the thin foil is transparent. As the laser intensity evolves, three stages in the acceleration process can be identified: at first the total reflection of the laser pulse, followed by partial reflection, and then near total reflection again due to the Doppler effect. The influences of the rising front of laser pulse and areal density of the ultrathin foil are investigated. It is found that an optimal laser pulse rising front exists for obtaining high (saturation) ion energy with the same laser energy within a short time. An optimal areal density also exists for obtaining the highest energy. For the same laser pulse, a higher areal density or a higher density with same areal density is more appropriate for obtaining a stationary state for making light pressure acceleration mechanism more effective.

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

    PubMed

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

    2008-07-01

    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 pulsesmin was routinely reached. Using a 4 kJ power supply, the pulse duration was between 500 mus and 1 ms. The setup was used for nuclear forward scattering measurements on 57Fe 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.

  14. 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

  15. Influence of Oceanic Synoptic Eddies on the Duration of Modal Acoustic Pulses

    NASA Astrophysics Data System (ADS)

    Makarov, D. V.; Kon'kov, L. E.; Petrov, P. S.

    2016-12-01

    We consider the problem of scattering of the modal acoustic pulses from synoptic eddies with allowance for the influence of the field of internal waves. The ray formalism in terms of the action-angle variables is used. The synoptic-eddy induced distortion of the sound-speed profile is shown to enhance the scattering of certain ray bundles from internal waves. The formulas allowing one to identify the modal pulses corresponding to such ray bundles are derived. These pulses differ from the other ones by increased duration. This fact can be used for obtaining additional information during acoustic tomography. The model of the underwater acoustic channel in the Sea of Japan is considered as an example.

  16. Acoustic impedance measurements of pulse tube refrigerators

    NASA Astrophysics Data System (ADS)

    Iwase, Takashi; Biwa, Tetsushi; Yazaki, Taichi

    2010-02-01

    Complex acoustic impedance is determined in a prototype refrigerator that can mimic orifice-type, inertance-type, and double inlet-type pulse tube refrigerators from simultaneous measurements of pressure and velocity oscillations at the cold end. The impedance measurements revealed the means by which the oscillatory flow condition in the basic pulse tube refrigerator is improved by additional components such as a valve and a tank. The working mechanism of pulse tube refrigerators is explained based on an electrical circuit analogy.

  17. Objectively-measured sleep duration and hyperglycemia in pregnancy

    PubMed Central

    Herring, Sharon J.; Nelson, Deborah B.; Pien, Grace W.; Homko, Carol; Goetzl, Laura M.; Davey, Adam; Foster, Gary D.

    2013-01-01

    Objective Our primary purpose was to assess the impact of objectively-measured nighttime sleep duration on gestational glucose tolerance. We additionally examined associations of objectively-measured daytime sleep duration and nap frequency on maternal glycemic control. Methods 63 urban, low-income, pregnant women wore wrist actigraphs for an average of 6 full days in mid-pregnancy prior to screening for hyperglycemia using the 1-hour oral glucose tolerance test (OGTT). Correlations of nighttime and daytime sleep durations with 1-hour OGTT values were analyzed. Multivariable logistic regression was used to evaluate independent associations between sleep parameters and hyperglycemia, defined as 1-hour OGTT values ≥ 130 mg/dL. Results Mean nighttime sleep duration was 6.9 ± 0.9 hours which was inversely correlated with 1-hour OGTT values (r = −0.28, p = 0.03). Shorter nighttime sleep was associated with hyperglycemia, even after controlling for age and body mass index (adjusted OR: 0.2; 95% CI: 0.1, 0.8). There were no associations of daytime sleep duration and nap frequency with 1-hour OGTT values or hyperglycemia. Conclusions Using objective measures of maternal sleep time, we found that women with shorter nighttime sleep durations had an increased risk of gestational hyperglycemia. Larger prospective studies are needed to confirm our negative daytime sleep findings. PMID:24239498

  18. 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.

  19. Seebeck Coefficient Measured With Differential Heat Pulses

    NASA Technical Reports Server (NTRS)

    Zoltan, L.; Wood, C.; Stapfer, G.

    1986-01-01

    Common experimental errors reduced because pulse technique suppresses drifts in thermoelectric measurements. Differential-heat-pulse apparatus measures Seebeck coefficient in semiconductors at temperatures up to 1,900 K. Sample heated to measuring temperature in furnace. Ends of sample then differentially heated a few degrees more by lamps. Differential temperature rise and consequent Seebeck voltage measured via thermocouple leads. Because pulse technique used, errors that often arise from long-term drifts in thermoelectric measurements suppressed. Apparatus works with temperature differences of only few degrees, further increasing accuracy of coefficients obtained.

  20. Ablation Study of WC and PCD Composites Using 10 Picosecond and 1 Nanosecond Pulse Durations at Green and Infrared Wavelengths

    NASA Astrophysics Data System (ADS)

    Eberle, Gregory; Wegener, Konrad

    An ablation study is carried out to compare 10 picosecond and 1 nanosecond pulse durations as well as 532 nanometre and 1064 nanometre wavelengths at each corresponding pulse duration. All laser parameters are kept constant in order to understand the influence of pulse duration and wavelength independently. The materials processed according to the electronic band structure are a metal and an insulator/metal composite, i.e. tungsten carbide and polycrystalline diamond composite respectively. After laser processing said materials, the ablation rate and surface roughness are determined. Analysis into the ablation behaviour between the various laser parameters and the materials processed is given, with a particular emphasis on the graphitisation of diamond.

  1. 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.

  2. 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.

  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. Dependence of the absorption of pulsed CO2-laser radiation by silane on wavenumber, fluence, pulse duration, temperature, optical path length, and pressure of absorbing and nonabsorbing gases

    NASA Astrophysics Data System (ADS)

    Bl/aŻejowski, Jerzy; Gruzdiewa, Ludwika; Rulewski, Jacek; Lampe, Frederick W.

    1995-05-01

    The absorption of three lines [P(20), 944.2 cm-1; P(14), 949.2 cm-1; and R(24), 978.5 cm-1] of the pulsed CO2 laser (0001-1000 transition) by SiH4 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 CO2 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.

  5. Atomic ionization by intense laser pulses of short duration: Photoelectron energy and angular distributions

    SciTech Connect

    Dondera, M.

    2010-11-15

    We introduce an adequate integral representation of the wave function in the asymptotic region, valid for the stage postinteraction between a one-electron atom and a laser pulse of short duration, as a superposition of divergent radial spherical waves. Starting with this representation, we derive analytic expressions for the energy and angular distributions of the photoelectrons and we show their connection with expressions used before in the literature. Using our results, we propose a method to extract the photoelectron distributions from the time dependence of the wave function at large distances. Numerical results illustrating the method are presented for the photoionization of hydrogenlike atoms from the ground state and several excited states by extreme ultraviolet pulses with a central wavelength of 13.3 nm and several intensities around the value I{sub 0}{approx_equal}3.51x10{sup 16} W/cm{sup 2}.

  6. Intensity-Duration Relation in the Bartlett-Lewis Rectangular Pulse Model

    NASA Astrophysics Data System (ADS)

    Ritschel, Christoph; Rust, Henning; Ulbrich, Uwe; Névir, Peter

    2015-04-01

    For several hydrological modelling tasks precipitation time series with a high (sub-daily) resolution are indispensable. This data is, however, not always available and thus replaced by model data. A canonical class of stochastic models for sub-daily precipitation is the class of Poisson cluster processes, e.g. the Bartlett-Lewis rectangular pulse model (BLRPM). The BLRPM has been shown to be able to well reproduce certain characteristics found in observations. Our focus is on intensity-duration relationship which are of particular importance in the context of hydrological modelling. We analyse several high resolution precipitation time series (5min) from Berlin and derive empirical intensity-duration relations for several return levels of intensities (intensity-duration-frequency curves, IDF curves). In a second step, we investigate to what extend the variants of a BLRPM are able to reproduce these relations (i.e., the IDF curves) for different situations (e.g., seasons) and for the various return-levels of intensities. By means of a sensitivity study with the BLRPM, we investigate to what extend the ability to reproduce the intensity-duration relationships is related to certain relations between the model parameters. Such relations are typically useful to reduce the complexity of the model and thus robustify and facilitate parameter estimation.

  7. Measurement and modeling of pulsed microchannel plate operation (invited).

    PubMed

    Rochau, G A; Wu, M; Kruschwitz, C; Joseph, N; Moy, K; Bailey, J; Krane, M; Thomas, R; Nielsen, D; Tibbitts, A

    2008-10-01

    Microchannel plates (MCPs) are a standard detector for fast-framing x-ray imaging and spectroscopy of high-temperature plasmas. The MCP is coated with conductive striplines that carry short duration voltage pulses to control the timing and amplitude of the signal gain. This gain depends on the voltage to a large exponent so that small reflections or impedance losses along the striplines can have a significant impact on the position-dependent amplitude and pulse width of the gain. Understanding the pulsed gain response therefore requires careful measurements of the position- and time-dependent surface voltage coupled with detailed modeling of the resulting electron cascade. We present measurements and modeling of the time- and space-dependent gain response of MCP detectors designed for use at Sandia National Laboratories' Z facility. The pulsed gain response is understood through measurements using a high impedence probe to determine the voltage pulse propagating along the stripline surface. Coupling the surface voltage measurements with Monte Carlo calculations of the electron cascade in the MCP provides a prediction of the time- and position-dependent gain that agrees with measurements made on a subpicosecond UV laser source to within the 25% uncertainty in the simulations.

  8. High-Power fiber amplifier with widely tunable repetition rate, fixed pulse duration, and multiple output wavelengths.

    PubMed

    Schrader, Paul E; Farrow, Roger L; Kliner, Dahv A V; Fève, Jean-Philippe; Landru, Nicolas

    2006-11-27

    We report a pulsed, fiber-amplified microchip laser providing widely tunable repetition rate (7.1 - 27 kHz) with constant pulse duration (1.0 ns), pulse energy up to 0.41 mJ, linear output polarization, diffraction-limited beam quality (M(2) < 1.2), and < 1% pulse-energy fluctuations. The pulse duration was shown to minimize nonlinear effects that cause temporal and spectral distortion of the amplified pulses. This source employs passive Q-switching, single-stage single-pass amplification, and cw pumping, thus offering high efficiency, simplicity, and compact, rugged packaging for use in practical applications. The high peak power and high beam quality make this system an ideal pump source for nonlinear frequency conversion, and we demonstrated efficient harmonic generation and optical parametric generation of wavelengths from 213 nm to 4.4 mum with Watt-level output powers.

  9. [An integral chip for the multiphase pulse-duration modulation used for voltage changer in biomedical microprocessor systems].

    PubMed

    Balashov, A M; Selishchev, S V

    2004-01-01

    An integral chip (IC) was designed for controlling the step-down pulse voltage converter, which is based on the multiphase pulse-duration modulation, for use in biomedical microprocessor systems. The CMOS technology was an optimal basis for the IC designing. An additional feedback circuit diminishes the output voltage dispersion at dynamically changing loads.

  10. 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.

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

    PubMed Central

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

    2015-01-01

    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, 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 for them 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 stimulate inner retinal neurons while avoiding activation of ganglion cell axons, thus confining retinal responses to the site of the electrode. We show that 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

  12. 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.

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

    PubMed Central

    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

  14. 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

    2015-08-14

    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. 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.

  16. Measurements of Sonoluminescence Temporal Pulse Shape

    NASA Astrophysics Data System (ADS)

    Moran, Michael J.; Sweider, Daren

    1998-06-01

    Experiments using time-correlated photon counting and optical bandpass filters measure new features in the time and spectral dependences of single-bubble sonoluminescence (SBSL). The SBSL full width at half maximum (FWHM) varies with wavelength at 3 °C, but not at 24 °C. The pulse shapes are dominated by nearly Gaussian peaks with FWHM in the 150- to 300-ps range. At 3 °C, increases of pulse width with acoustic drive pressure are independent of wavelength. The pulses have extended tails that decay exponentially, with effective lifetimes of about 150 ps.

  17. Sensitivity to pulse phase duration in cochlear implant listeners: Effects of stimulation mode

    PubMed Central

    Chatterjee, Monita; Kulkarni, Aditya M.

    2014-01-01

    The objective of this study was to investigate charge-integration at threshold by cochlear implant listeners using pulse train stimuli in different stimulation modes (monopolar, bipolar, tripolar). The results partially confirmed and extended the findings of previous studies conducted in animal models showing that charge-integration depends on the stimulation mode. The primary overall finding was that threshold vs pulse phase duration functions had steeper slopes in monopolar mode and shallower slopes in more spatially restricted modes. While the result was clear-cut in eight users of the Cochlear CorporationTM device, the findings with the six user of the Advanced BionicsTM device who participated were less consistent. It is likely that different stimulation modes excite different neuronal populations and/or sites of excitation on the same neuron (e.g., peripheral process vs central axon). These differences may influence not only charge integration but possibly also temporal dynamics at suprathreshold levels and with more speech-relevant stimuli. Given the present interest in focused stimulation modes, these results have implications for cochlear implant speech processor design and protocols used to map acoustic amplitude to electric stimulation parameters. PMID:25096116

  18. 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.

  19. 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

  20. 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.

  1. Pulse energy measurement at the SXR instrument

    DOE PAGES

    Moeller, Stefan; Brown, Garth; Dakovski, Georgi; ...

    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

  2. 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.

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

    PubMed

    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.

  4. 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.

  5. 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.

  6. INTERACTION OF LASER RADIATION WITH MATTER: Effect of the pulse duration on graphitisation of diamond during laser ablation

    NASA Astrophysics Data System (ADS)

    Kononenko, Vitalii V.; Kononenko, Taras V.; Pimenov, S. M.; Sinyavskii, M. N.; Konov, Vitalii I.; Dausinger, F.

    2005-03-01

    Processes of graphitisation of laser-irradiated polycrystalline diamond surface exposed to multipulse irradiation are studied experimentally. The thickness of the laser-modified layer as a function of the laser-pulse duration ranging from 100 fs to 1.5 μs and the effect of the radiation wavelength on this thickness are studied. It is shown that the diamond graphitisation during multipulse laser ablation is a thermally stimulated process. The dependences of the diamond-ablation rates on the radiation energy density under the action of laser pulses of various durations are presented.

  7. Laser ablation of skull tissue using transverse excited 9.6-μm CO2 lasers with pulse durations of 1-100 μs

    NASA Astrophysics Data System (ADS)

    Fried, Nathaniel M.; Fried, Daniel

    2000-06-01

    Craniotomy using a drill and saw frequently results in fragmentation of the skull plate. Lasers have the potential to remove the skull plate intact. TE CO2 lasers operating at the peak absorption wavelength of bone ((lambda) equals 9.6 micrometer) and with pulse durations of 5 - 10 microseconds, approximately the thermal relaxation time in hard tissue, produced high ablation rates and minimal peripheral thermal damage. Both thick (2 mm) and thin (250 micrometer) bovine skull samples were perforated and the ablation rates calculated. Results were compared with Q-switched and free- running Er:YAG lasers ((lambda) equals 2.94 micrometer, (tau) p equals 150 ns and 150 microseconds). The CO2 laser perforated thick sections at ablation rates of 10 - 15 micrometer per pulse and fluences of approximately 6 J/cm2. There was no discernible thermal damage and no need for water irrigation during ablation. Pulse durations >= 20 microseconds resulted in significant tissue charring which increased with the pulse duration. Although the Er:YAG laser produced ablation rates of approximately 100 micrometer per pulse, fluences > 30 J/cm2 were required to perforate thick samples, and thermal damage measured 25 - 40 micrometer. In summary, the novel 5 - 10 microsecond pulse length of the TE CO2 laser is long enough to avoid a marked reduction in the ablation rate due to plasma formation and short enough to avoid peripheral thermal damage through thermal diffusion during the laser pulse. Further studies with the TE CO2 laser are warranted for potential clinical application craniotomy procedures.

  8. Pulsed thrust measurements using electromagnetic calibration techniques

    SciTech Connect

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

    2011-03-15

    A thrust stand for accurately measuring impulse bits, which ranged from 10-1000 {mu}N 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 {mu}N 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 {mu}N s with 95% credibility.

  9. 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

  10. 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.

  11. Plasma processes in water under effect of short duration pulse discharges

    NASA Astrophysics Data System (ADS)

    Gurbanov, Elchin

    2013-09-01

    It is very important to get a clear water without any impurities and bacteria by methods, that don't change the physical and chemical indicators of water now. In this article the plasma processes during the water treatment by strong electric fields and short duration pulse discharges are considered. The crown discharge around an electrode with a small radius of curvature consists of plasma leader channels with a high conductivity, where the thermo ionization processes and UV-radiation are taken place. Simultaneously the partial discharges around potential electrode lead to formation of atomic oxygen and ozone. The spark discharge arises, when plasma leader channels cross the all interelectrode gap, where the temperature and pressure are strongly grown. As a result the shock waves and dispersing liquid streams in all discharge gap are formed. The plasma channels extend, pressure inside it becomes less than hydrostatic one and the collapse and UV-radiation processes are started. The considered physical processes can be successfully used as a basis for development of pilot-industrial installations for conditioning of drinking water and to disinfecting of sewage.

  12. 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.

  13. Synchrotron X-ray Powder Diffraction and Absorption Spectroscopy in Pulsed Magnetic Fields with Milliseconds Duration

    NASA Astrophysics Data System (ADS)

    Vanacken, J.; Detlefs, C.; Mathon, O.; Frings, P.; Duc, F.; Lorenzo, J. E.; Nardone, M.; Billette, J.; Zitouni, A.; Dominguez, M.-C.; Herczeg, J.; Bras, W.; Moshchalkov, V. V.; Rikken, G.

    2007-03-01

    X-ray Powder Diffraction and X-ray Absorption Spectroscopy experiments (WAS) and X-ray magnetic circular dichroism (XMCD) experiments were carried out at the ESRF DUBBLE beam line (BM26) and at the energy dispersive beam line (ID24), respectively. A mobile pulse generator, developed at the LNCMP, delivered 110kJ to the load coil, which was sufficient to generate peak fields of 30T with a rise time of about 5 ms. A liquid He flow cryostat allowed us to vary the sample temperature accurately between 4.2K and 300K. Powder diffraction patterns of TbVO4 were recorded in a broad temperature range using 21 keV monochromatic X-rays and using an on-line image plate detector. We observed the suppression of the Jahn-Teller structural distortion in TbVO4 due to the high magnetic pulsed field. XAS spectra could be measured and finite XMCD signals, directly proportional to the magnetic moment on the Gd absorber atom, were measured in thin Gd foils. Thanks to its element and orbital selectivity, XMCD proofs to be very useful in probing the magnetic properties and due to the strong brilliance of the synchrotron beam, the signals can be measured even in the ms range.

  14. Toxicity of magnesium pulses to tropical freshwater species and the development of a duration-based water quality guideline.

    PubMed

    Hogan, Alicia C; Trenfield, Melanie A; Harford, Andrew J; van Dam, Rick A

    2013-09-01

    Six freshwater species (Chlorella sp., Lemna aequinoctialis, Amerianna cumingi, Hydra viridissima, Moinodaphnia macleayi, and Mogurnda mogurnda) were exposed to 4-h, 8-h, and 24-h Mg pulses in natural creek water. Magnesium toxicity to all species increased with exposure duration; however, the extent of increase and the nature of the relationship differed greatly between species. Based on median inhibitory concentrations (IC50s), and compared with continuous exposure data from a previous study, the increase in toxicity with increasing exposure duration from 4 h to continuous (72-144 h) ranged from approximately 2-fold for Chlorella sp. and H. viridissima to greater than 40-fold for A. cumingi. Moreover, the form of the relationship between Mg toxicity and duration ranged from linear or near-linear to exponential for different species. The life-stage at which M. macleayi was exposed was important, with cladocerans pulsed at the onset of reproductive maturity being approximately 4 times more sensitive (based on IC50s) than younger than 6-h-old neonates. Species sensitivity distributions were constructed for the 4-h, 8-h, and 24-h pulse durations, from which 99% species protection guideline values (95% confidence limits [CLs]) of 94 (6.4-1360) mg/L, 14 (0.5-384) mg/L, and 8.0 (0.5-144) mg/L Mg, respectively, were derived. These values were plotted against exposure duration (h) and polynomial interpolation used to derive a guideline value for any pulse duration within the range assessed.

  15. 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.

  16. Pulse-duration memory effect in NbSe3 and comparison with numerical simulations of phase organization

    NASA Astrophysics Data System (ADS)

    Jones, T. C.; Wu, Xinlei; Simpson, C. R., Jr.; Clayhold, J. A.; McCarten, J. P.

    2000-04-01

    The oscillatory response of the 59 K charge density wave (CDW) in NbSe3 to a sequence of current pulses was investigated as a function of pulse height and pulse width. Of the 16 samples investigated, seven clearly exhibited the learned behavior commonly referred to as the pulse-duration memory effect (PDME). These seven samples, after training, learned the length of the pulse, and always finished the pulse at a minimum in the voltage oscillation (maximum CDW velocity). Contrary to previous reports, we observe the PDME for pulse heights much greater than threshold. We find that as the number of metastable states accessible to the CDW during the low portion of the drive pulse is decreased, the PDME degrades. We summarize the qualitative differences between the theory of phase organization and the observed experimental data. To facilitate this comparison we have performed numerical simulations of the Fukayama-Lee-Rice (FLR) model in both the weak and strong pinning limits in an attempt to reproduce the learned response. We find no evidence for phase organization (no learning) in the weak pinning limit; also the wave forms generated in the strong pinning limit differ qualitatively from the experimental data. This comparative study suggests that the theoretical description of the PDME requires further investigation, and the importance of amplitude collapse and boundary conditions demand future examination.

  17. Pressure Pulse Measurements Using Optical Hydrophone Principles

    NASA Astrophysics Data System (ADS)

    Ueberle, Friedrich; Jamshidi-Rad, Abtin

    2011-02-01

    Pressure pulses are used in extracorporeal lithotripsy, pain therapy and other medical applications. Typical lithotripter pulses reach positive pressure amplitudes of ca. 20 to more than 100 MPa and negative pressures of -5 to more than -20 MPa, depending on the focusing properties and energy settings of the source. The IEC standard 61846, which defines the acoustic parameters of pressure pulse fields, describes the properties of "Focus-" and "Field-" type hydrophones, which were originally specified as PVDF sensors. During recent years, two types of optical sensors were developed, which are based on the principle of measuring reflection changes of a laser beam at a glass-water surface: The fiber optic sensor using bare optical fibers and the "light spot" sensor using a thick glass block. Measurements with both hydrophone types were made with a low pressure transducer (p+max=3 MPa), and two electromagnetic lithotripter sources with the same total acoustic energy (E5MPa=90mJ), one with a wide focus (FWHM = 11 mm, p+max = 30 MPa) and the other with a small focus (FWHM = 3,5 mm, p+max = 83 MPa). The results show that both optical sensor types provide high pressure-time signal fidelity comparable to PVDF membrane sensors. Both optical hydrophones can serve as "Focus-" and "Field-" hydrophones as defined in the lithotripsy measurement standard IEC 61846.

  18. 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.

  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. 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.

  1. 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.

  2. 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.

  3. Effect of pulse duration on the acoustic frequency emissions during the laser-induced breakdown of atmospheric air.

    PubMed

    Manikanta, E; Vinoth Kumar, L; Venkateshwarlu, P; Leela, Ch; Kiran, P Prem

    2016-01-20

    Acoustic shock waves (ASWs) in the frequency range of 30-120 kHz generated during laser-induced breakdown (LIB) of ambient air using 7 ns and 30 ps pulse durations are studied. The specific frequency range and peak amplitudes are observed to be different for nanosecond (ns) and picosecond (ps) LIB. The ASW frequencies for ps-LIB lie between 90 and 120 kHz with one dominant peak, whereas for ns-LIB, two dominant peaks with frequencies in the 30-70 kHz and 80-120 kHz range are observed. These frequencies are observed to be laser pulse intensity dependent. With increasing energy of ns laser pulses, acoustic frequencies move toward the audible frequency range. The variation in the acoustic parameters, such as peak-to-peak pressures, signal energy, frequency and acoustic pulse widths as a function of laser energy, for two different pulse durations are presented in detail and compared. The acoustic emissions are observed to be higher for ns-LIB than ps-LIB, indicating higher conversion efficiency of optical energy into mechanical energy.

  4. Diode-pumped Kerr-lens mode-locked Yb:LYSO laser with 61fs pulse duration.

    PubMed

    Tian, Wenlong; Wang, Zhaohua; Wei, Long; Peng, Yingnan; Zhang, Jinwei; Zhu, Zheng; Zhu, Jiangfeng; Han, Hainian; Jia, Yulei; Zheng, Lihe; Xu, Jun; Wei, Zhiyi

    2014-08-11

    A stable diode pumped Kerr-lens mode-locked (KLM) Yb:LuYSiO5 (Yb:LYSO) laser of generating 61 fs pulses at a central wavelength of 1055.4 nm is experimentally demonstrated. This is, to the best of our knowledge, the first demonstration of femtosecond KLM operation in Yb:LYSO laser, and it is believed that 61 fs is the shortest pulse duration ever produced from an Yb-doped orthosilicate laser. The average output power of the mode-locked laser is 40 mW and the repetition rate is 113 MHz.

  5. Copper vapour laser with an efficient semiconductor pump generator having comparable pump pulse and output pulse durations

    SciTech Connect

    Yurkin, A A

    2016-03-31

    We report the results of experimental studies of a copper vapour laser with a semiconductor pump generator capable of forming virtually optimal pump pulses with a current rise steepness of about 40 A ns{sup -1} in a KULON LT-1.5CU active element. To maintain the operating temperature of the active element's channel, an additional heating pulsed oscillator is used. High efficiency of the pump generator is demonstrated. (lasers)

  6. Picosecond pulses of variable duration from a high-power passively mode-locked Nd:YVO(4) laser free of spatial hole burning.

    PubMed

    Nadeau, Marie-Christine; Petit, Stéphane; Balcou, Philippe; Czarny, Romain; Montant, Sébastien; Simon-Boisson, Christophe

    2010-05-15

    We report on a high-power passively mode-locked TEM(00)Nd:YVO(4) oscillator, 888 nm diode-pumped, with pulse durations adjustable between 46 ps and 12 ps. The duration tunability was obtained by varying the output coupler (OC) transmission while avoiding resorting to spatial hole burning (SHB) for pulse shortening. At a repetition rate of 91 MHz and for an output power ranging from 15 Wto45 W, we produced SHB-free 12-ps-to32-ps-long pulses. Within this range of power, these are the shortest pulse durations obtained directly from Nd:YVO(4) oscillators.

  7. 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.

  8. 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

  9. Timing and duration of the Melt-Water Pulse 1A

    NASA Astrophysics Data System (ADS)

    Deschamps, P.; Durand, N.; Bard, E. G.; Hamelin, B.; Camoin, G.; Thomas, A. L.; Henderson, G. M.; Okuno, J.; Yokoyama, Y.

    2011-12-01

    Studying past sea levels provides invualuable information to further our understanding of ice-sheets' response to climate forcing. So far, the most complete and accurate sea-level record that encompassed the period between the Last Glacial Maximum and the present day is based on cores drilled offshore the Barbados coral reef. This record suggests a non-monotonous sea-level rise punctuated by dramatic accelerations, the so-called Melt Water Pulse events, that correspond to massive inputs of continental ice. The most extreme of these events, the MWP1-A, initially identified in the coral-based sea level record from the Barbados island, suggests a sea-level rise of ~20 meters between 14.1 and 13.6 ka. However, this event remains enigmatic and controversial. The temporal relationship between the MWP1-A and the abrupt climatic events that punctuated the last deglaciation is a subject of controversial debates. Several records are consistent with its occurrence, but no broad agreement emerges about its timing. Finally, large uncertainties surrounding the amplitude and timing of this Melt-Water Pulse 1A have raised doubts about the ice source responsible for such a step in sea-level rise and have questioned its temporal and causal relationships with the Bølling - Older Dryas - Allerød alternance, a major climatic oscillation during the last deglaciation. Consequently, it remains a key issue to fully confirm the existence, timing and amplitude of the MWP-1A by a precise coral reef record. The recent IODP Expedition 310 Tahiti Sea Level offers a unique opportunity to fully confirm the existence, timing and amplitude of the MWP-1A by a precise coral reef record. U-Th ages obtained on shallow to deeper corals collected during the IODP Expedition 310 offshore Tahiti Island extend the previous Tahiti sea-level and allow to document the sea-level rise during the key period of the MWP-1A. Our results confirm the occurrence of an acceleration of the sea-level rise during that

  10. Vibration measurements by pulsed digital holographic endoscopy

    NASA Astrophysics Data System (ADS)

    Schedin, Staffan; Pedrini, Giancarlo; Perez-Lopez, Carlos; Mendoza Santoyo, Fernando

    2005-02-01

    Digital holographic interferometry in combination with a flexible fiber endoscope allows high precision measurements of deformations on hidden objects surfaces, inside cavities and objects with small access apertures. A digital holographic endoscopy system is described with a frequency-doubled, twin oscillator Q-switched pulsed Nd:YAG laser as light source. A sequence of digital hologram pairs are recorded with a maximum repetition rate of 260 ms. Each digital hologram is captured at separate video frames of a CCD-camera. The time separation between the laser pulses from each cavity can be set in the range from 50 to 500 μs. The digital holograms are transferred to a PC via a frame grabber and evaluated quantitatively by the Fourier transform method. The resulting phase fringe pattern has the information needed to evaluate quantitatively the amount of the deformation. Experimental results of vibration measurements of hidden mechanical and biological object surfaces are presented. The quality of the results obtained by mechanical object surfaces is usually higher than for biological surfaces. This can be explained easily by the fact that a biological surface is much more complex than a mechanical surface in the sense that some parts of the surface may reflect the light well whereas other parts may absorb the light. Also, biological surfaces are translucent, which means that part of the light may enter inside the sample where it may be absorbed or reflected.

  11. Temporary tattoo for wireless human pulse measurement

    NASA Astrophysics Data System (ADS)

    Pepłowski, Andrzej; Janczak, Daniel; Krzemińska, Patrycja; Jakubowska, Małgorzata

    2016-09-01

    Screen-printed sensor for measuring human pulse was designed and first tests using a demonstrator device were conducted. Various materials and sensors' set ups were compared and the results are presented as the starting point for fabrication of fully functional device. As a screen printing substrate, commercially available temporary tattoo paper was used. Using previously developed nanomaterials-based pastes design of a pressure sensor was printed on the paper and attached to the epidermis. Measurements were aimed at determining sensors impedance constant component and its variability due to pressure wave caused by the human pulse. The constant component was ranging from 2kΩ to 6kΩ and the variations of the impedance were ranging from +/-200Ω to +/-2.5kΩ, depending on the materials used and the sensor's configuration. Calculated signal-to-noise ratio was 3.56:1 for the configuration yielding the highest signal level. As the device's net impedance influences the effectiveness of the wireless communication, the results presented allow for proper design of the sensor for future health-monitoring devices.

  12. Generation of microseconds-duration square pulses in a passively mode-locked fiber laser

    NASA Astrophysics Data System (ADS)

    Liu, Tonghui; Jia, Dongfang; Liu, Ying; Wang, Zhaoying; Yang, Tianxin

    2015-12-01

    An ultra-wide tunable square pulse operating in dissipative soliton resonance (DSR) region has been experimentally investigated in a passively mode-locked figure-of-eight fiber laser. In our experiment, by simply increasing the pump power, the pulse width can be tuned in an ultra-wide range from 135 ns to 2272 ns without wave-breaking while the peak power remains almost constant. The maximum output single pulse energy is 236.8 nJ at the pump power of 508 mW. A 960 m highly nonlinear fiber (HNLF) is employed to realize widely tunable square pulse in the DSR region. To the best of our knowledge, this is the widest tunable range of pulse width in any all-fiber passively mode-locked fiber laser.

  13. Green and ultraviolet pulse generation with a compact, fiber laser, chirped-pulse amplification system for aerosol fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Lou, Janet W.; Currie, Marc; Sivaprakasam, Vasanthi; Eversole, Jay D.

    2010-10-01

    We use a compact chirped-pulse amplified system to harmonically generate ultrashort pulses for aerosol fluorescence measurements. The seed laser is a compact, all-normal dispersion, mode-locked Yb-doped fiber laser with a 1050 nm center wavelength operating at 41 MHz. Average powers of more than 1.2 W at 525 nm and 350 mW at 262 nm are generated with <500 fs pulse durations. The pulses are time-stretched with high-dispersion fiber, amplified by a high-power, large-mode-area fiber amplifier, and recompressed using a chirped volume holographic Bragg grating. The resulting high-peak-power pulses allow for highly efficient harmonic generation. We also demonstrate for the first time to our knowledge, the use of a mode-locked ultraviolet source to excite individual biological particles and other calibration particles in an inlet air flow as they pass through an optical chamber. The repetition rate is ideal for biofluorescence measurements as it allows faster sampling rates as well as the higher peak powers as compared to previously demonstrated Q-switched systems while maintaining a pulse period that is longer than the typical fluorescence lifetimes. Thus, the fluorescence excitation can be considered to be quasicontinuous and requires no external synchronization and triggering.

  14. Green and ultraviolet pulse generation with a compact, fiber laser, chirped-pulse amplification system for aerosol fluorescence measurements.

    PubMed

    Lou, Janet W; Currie, Marc; Sivaprakasam, Vasanthi; Eversole, Jay D

    2010-10-01

    We use a compact chirped-pulse amplified system to harmonically generate ultrashort pulses for aerosol fluorescence measurements. The seed laser is a compact, all-normal dispersion, mode-locked Yb-doped fiber laser with a 1050 nm center wavelength operating at 41 MHz. Average powers of more than 1.2 W at 525 nm and 350 mW at 262 nm are generated with <500 fs pulse durations. The pulses are time-stretched with high-dispersion fiber, amplified by a high-power, large-mode-area fiber amplifier, and recompressed using a chirped volume holographic Bragg grating. The resulting high-peak-power pulses allow for highly efficient harmonic generation. We also demonstrate for the first time to our knowledge, the use of a mode-locked ultraviolet source to excite individual biological particles and other calibration particles in an inlet air flow as they pass through an optical chamber. The repetition rate is ideal for biofluorescence measurements as it allows faster sampling rates as well as the higher peak powers as compared to previously demonstrated Q-switched systems while maintaining a pulse period that is longer than the typical fluorescence lifetimes. Thus, the fluorescence excitation can be considered to be quasicontinuous and requires no external synchronization and triggering.

  15. Evolution of few-cycle pulses in nonlinear dispersive media: Velocity of the center of mass and root-mean-square duration

    NASA Astrophysics Data System (ADS)

    Kapoyko, Yury A.; Drozdov, Arkadiy A.; Kozlov, Sergei A.; Zhang, Xi-Cheng

    2016-09-01

    Simple arithmetic dependencies of the velocity of the mass center motion and the root-mean-square duration of initially single-cycle, two-cycle, and Gaussian pulses with a random number of oscillations under the pulse envelope are derived depending on their center frequency, initial duration, and peak field amplitude, as well as on dispersive and nonlinear characteristics of homogeneous isotropic dielectric media. In media with normal group dispersion, it is shown that due to nonresonant dispersion the square of the few-cycle pulse duration increases with distance inversely proportional to the fourth power of the number of input pulse cycles. In media with normal group dispersion, the square of the pulse duration is inversely proportional to the number of input pulse cycles due to cubic nonlinearity. In media with anomalous group dispersion, it is shown that due to cubic nonlinearity, few-cycle pulse self-compression decreases with the reduction of the number of cycles in the initial pulse. This pulse self-compression effect has a threshold nature and terminates at a fixed number of cycles of the input pulse. Such a number of cycles is determined by the input intensity and the central frequency of the pulse, as well as by the dispersive and nonlinear characteristics of the medium.

  16. 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.

  17. 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.

  18. 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.

  19. 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).

  20. Plastic scintillator detector for pulsed flux measurements

    NASA Astrophysics Data System (ADS)

    Kadilin, V. V.; Kaplun, A. A.; Taraskin, A. A.

    2017-01-01

    A neutron detector, providing charged particle detection capability, has been designed. The main purpose of the detector is to measure pulsed fluxes of both charged particles and neutrons during scientific experiments. The detector consists of commonly used neutron-sensitive ZnS(Ag) / 6LiF scintillator screens wrapping a layer of polystyrene based scintillator (BC-454, EJ-254 or equivalent boron loaded plastic). This type of detector design is able to log a spatial distribution of events and may be scaled to any size. Different variations of the design were considered and modelled in specialized toolkits. The article presents a review of the detector design features as well as simulation results.

  1. 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.

  2. 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).

  3. Unstable and multiple pulsing can be invisible to ultrashort pulse measurement techniques

    SciTech Connect

    Rhodes, Michelle A.; Guang, Zhe; Trebino, Rick

    2016-12-29

    Here, multiple pulsing occurs in most ultrashort-pulse laser systems when pumped at excessively high powers, and small fluctuations in pump power in certain regimes can cause unusual variations in the temporal separations of sub-pulses. Unfortunately, the ability of modern intensity-and-phase pulse measurement techniques to measure such unstable multi-pulsing has not been studied. Here we report calculations and simulations finding that allowing variations in just the relative phase of a satellite pulse causes the second pulse to completely disappear from a spectral interferometry for direct electric field reconstruction (SPIDER) measurement. We find that, although neither frequency-resolved optical gating (FROG) nor autocorrelation can determine the precise properties of satellite pulses due to the presence of instability, they always succeed in, at least, seeing the satellite pulses. Also, additional post-processing of the measured FROG trace can determine the correct approximate relative height of the satellite pulse and definitively indicate the presence of unstable multiple-pulsing.

  4. Unstable and multiple pulsing can be invisible to ultrashort pulse measurement techniques

    DOE PAGES

    Rhodes, Michelle A.; Guang, Zhe; Trebino, Rick

    2016-12-29

    Here, multiple pulsing occurs in most ultrashort-pulse laser systems when pumped at excessively high powers, and small fluctuations in pump power in certain regimes can cause unusual variations in the temporal separations of sub-pulses. Unfortunately, the ability of modern intensity-and-phase pulse measurement techniques to measure such unstable multi-pulsing has not been studied. Here we report calculations and simulations finding that allowing variations in just the relative phase of a satellite pulse causes the second pulse to completely disappear from a spectral interferometry for direct electric field reconstruction (SPIDER) measurement. We find that, although neither frequency-resolved optical gating (FROG) nor autocorrelationmore » can determine the precise properties of satellite pulses due to the presence of instability, they always succeed in, at least, seeing the satellite pulses. Also, additional post-processing of the measured FROG trace can determine the correct approximate relative height of the satellite pulse and definitively indicate the presence of unstable multiple-pulsing.« less

  5. Recruitment of the intracellular Ca2+ by ultrashort electric stimuli: the impact of pulse duration.

    PubMed

    Semenov, Iurii; Xiao, Shu; Pakhomova, Olga N; Pakhomov, Andrei G

    2013-09-01

    Nanosecond-duration electric stimuli are distinguished by the ability to permeabilize intracellular membranes and recruit Ca2+ from intracellular stores. We quantified this effect in non-excitable cells (CHO) using ratiometric Ca2+ imaging with Fura-2. In a Ca(2+)-free medium, 10-, 60-, and 300-ns stimuli evoked Ca2+ transients by mobilization of Ca2+ from the endoplasmic reticulum. With 2 mM external Ca2+, the transients included both extra- and intracellular components. The recruitment of intracellular Ca2+ increased as the stimulus duration decreased. At the threshold of 200-300 nM, the transients were amplified by calcium-induced calcium release. We conclude that nanosecond stimuli mimic Ca2+ signaling while bypassing the usual receptor- and channels-mediated cascades. The recruitment of the intracellular Ca2+ can be controlled by the duration of the stimulus.

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

    PubMed

    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.

  7. Low-loss flake-graphene saturable absorber mirror for laser mode-locking at sub-200-fs pulse duration

    NASA Astrophysics Data System (ADS)

    Cunning, B. V.; Brown, C. L.; Kielpinski, D.

    2011-12-01

    Saturable absorbers are a key component for mode-locking femtosecond lasers. Polymer films containing graphene flakes have recently been used in transmission as laser mode-lockers but suffer from high nonsaturable loss, limiting their application in low-gain lasers. Here, we present a saturable absorber mirror based on a film of pure graphene flakes. The device is used to mode lock an erbium-doped fiber laser, generating pulses with state-of-the-art, sub-200-fs duration. The laser characteristic indicates that the film exhibits low nonsaturable loss (13% per pass) and large absorption modulation depth (45% of low-power absorption).

  8. Selective removal of composite sealants with near-ultraviolet laser pulses of nanosecond duration.

    PubMed

    Louie, Tiffany M; Jones, Robert S; Sarma, Anupama V; Fried, Daniel

    2005-01-01

    It is often necessary to replace pit and fissure sealants and composite restorations. This task is complicated by the necessity for complete removal of the remaining composite to enable suitable adhesion of new composite. Previous studies have shown that 355-nm laser pulses from a frequency-tripled Nd:YAG laser can selectively remove residual composite after orthodontic bracket removal on enamel surfaces. Our objective is to determine if such laser pulses are suitable for selective removal of composite pit and fissure sealants and restorations. Optical coherence tomography is used to acquire optical cross sections of the occlusal topography nondestructively before sealant application, after sealant application, and after sealant removal. Thermocouples are used to monitor the temperature in the pulp chamber during composite removal under clinically relevant ablation rates, i.e., 30 Hz and 30 mJ/pulse. At an irradiation intensity of 1.3 J/cm2, pit and fissure sealants are completely removed without visible damage to the underlying enamel. At intensities above 1.5 J/cm2, incident laser pulses remove the resin layer while at the same time preferentially etching the surface of the enamel. Temperature excursions in the pulp chamber of extracted teeth are limited to less than 5 degrees C if air-cooling is used during the rapid removal (1 to 2 min) of sealants, water-cooling is not necessary. Selective removal of composite restorative materials is possible without damage to the underlying sound tooth structure.

  9. 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.

  10. 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.

  11. Picosecond pulse measurements using the active laser medium

    NASA Technical Reports Server (NTRS)

    Bernardin, James P.; Lawandy, N. M.

    1990-01-01

    A simple method for measuring the pulse lengths of synchronously pumped dye lasers which does not require the use of an external nonlinear medium, such as a doubling crystal or two-photon fluorescence cell, to autocorrelate the pulses is discussed. The technique involves feeding the laser pulses back into the dye jet, thus correlating the output pulses with the intracavity pulses to obtain pulse length signatures in the resulting time-averaged laser power. Experimental measurements were performed using a rhodamine 6G dye laser pumped by a mode-locked frequency-doubled Nd:YAG laser. The results agree well with numerical computations, and the method proves effective in determining lengths of picosecond laser pulses.

  12. 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%.

  13. Multifunctional optical correlator for picosecond ultraviolet laser pulse measurement.

    PubMed

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

    2014-11-01

    A compact multifunctional optical correlator system for pulse width measurement of ultrashort ultraviolet (UV) pulses has been designed and experimentally demonstrated. Both autocorrelation and cross-correlation functions are measured using a single nonlinear crystal, and the switching between two measurements requires no adjustment of phase matching and detector. The system can measure UV pulse widths from sub-picoseconds to 100 ps, and it involves no auxiliary pulse in the measurement. The measurement results on a burst-mode picosecond UV laser show a high-quality performance on speed, accuracy, resolution, and dynamic range. The proposed correlator can be applied to measure any ultrashort UV pulses produced through sum-frequency generation or second-harmonic generation.

  14. 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.

  15. Mean velocities measured with the double pulse technique

    NASA Astrophysics Data System (ADS)

    Nielsen, E.

    2004-10-01

    It was recently observed that double-pulse measurements of the mean velocities of a wide asymmetric spectrum are a function of the time lag between the pulses (Uspensky et al., 2004). Here we demonstrate that the observed relationship probably is influenced by the measurement technique in a way that is consistent with theoretical prediction. It is further shown that for small time lags the double pulse velocity is a good approximation to the mean Doppler velo-city.

  16. 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.

  17. 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.

  18. High-power passively mode-locked Nd:YVO4 oscillator with adjustable pulse duration between 46 ps and 12 ps

    NASA Astrophysics Data System (ADS)

    Nadeau, Marie-Christine; Petit, Stéphane; Balcou, Philippe; Czarny, Romain; Montant, Sébastien; Simon-Boisson, Christophe

    2010-05-01

    We report on a high-power, passively mode-locked, TEM00 Nd:YVO4 oscillator with adjustable pulse duration between 46 and 12ps. The laser is end-pumped by an 888nm laser diode and mode-locking is achieved with a semiconductor saturable absorber mirror (SESAM). The laser has a repetition rate of 91MHz and the M2 beam quality factor is better than 1.2 at 15ps. At the optimum output coupler, it provides a maximum average output power of 45W with 32ps pulse duration. In literature, the presence of spatial hole burning (SHB) often helps to shorten the pulse length down to few picoseconds. However, SHB might be an issue for some specific application requiring e.g. low noise picosecond oscillators. In this contribution, we demonstrate that it is possible to shorten the pulse duration by lowering the intracavity losses without SHB. Pulse tunability from 46 to 12ps is achieved by changing the output coupler of the cavity while staying in the continuous-wave mode-locked regime. Pulse duration is almost linear with the output coupler transmission and increases from 12 to 32ps with average output power ranging from 15 to 45W. In this range of output power, we demonstrate the shortest pulses directly from a Nd:YVO4 oscillator.

  19. 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.

  20. 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

  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. Pulse

    MedlinePlus

    ... the underside of the opposite wrist, below the base of the thumb. Press with flat fingers until ... determine if the patient's heart is pumping. Pulse measurement has other uses as well. During or immediately ...

  3. 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.

  4. 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.

  5. CIDME: Short distances measured with long chirp pulses.

    PubMed

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

    2016-12-01

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

  6. CIDME: Short distances measured with long chirp pulses

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  7. High-power sources with smoothly adjustable pulse duration for powering gas-discharge tubes of laser pumping systems

    NASA Astrophysics Data System (ADS)

    Vakulenko, V. M.; Ivanov, L. P.; Ganshin, Y. A.; Karpyshev, I. L.; Korneyev, V. A.

    1985-10-01

    A series of power supplies for gas-discharge tubes in laser pumping systems has been developed on the basis of the same circuit but with different levels of partial discharge of the capacitive energy storing device. The charger converts the a.c. network voltage into a constant current, very efficiently and at the same charging rate regardless of the discharge level. An overall size and weight reduction is made possible by an intermediate frequency conversion from 50 Hz to 1 kHz, which also allows raising the repetition rate of output pulses. The charger consists of an inverter and a rectifier. The parallel-type inverter includes a thyristor-diode bridge with capacitors and a transformer, and a choke coil, for converting the sine-wave a.c. network voltage into a higher-frequency (1 kHz) square-wave alternating one after the first rectifying it. An important feature here is stiff overvoltage suppression, especially across the switching capacitors, during wide swings such as from no load to full load. The rectifier includes a 300/1000 V step-up transformer with another thyristor-diode bridge and a choke coil in series. A discharge commutator across the rectifier output shunted by a filter-capacitance ensures proper cutoff of the charge discharge current and corresponding control of the pulse duration.

  8. Picosecond pulse duration laser treatment for dermal melanocytosis in Asians : A retrospective review.

    PubMed

    Ohshiro, Takafumi; Ohshiro, Toshio; Sasaki, Katsumi; Kishi, Kazuo

    2016-06-29

    Background and aims: Recently novel picosecond duration lasers (ps-lasers) have been developed for the treatment of multicolored and recalcitrant tattoos, and safety and efficacy have been reported. We therefore hypothesized that the ps-laser could be an alternative treatment for dermal pigmented lesions and performed a retrospective review to evaluate the efficacy and safety of the ps-laser. Subjects and methods: A retrospective photographic review of 10 patients with dermal pigmented lesions was performed (ages from 4 months to 52 yr), 6 nevus of Ota, 3 ectopic Mongolian spots and 1 Mongolian spots. The patients were treated in the Ohshiro Clinic with picosecond 755 nm alexandrite laser (ps-Alex laser) and picosecond 1064 nm Nd:YAG laser (ps-Nd:YAG laser) from April 2014 to December 2015 (ps-Alex laser, 7 patients; ps-Nd:YAG laser, 3 patients, 1 to 3 treatment sessions). Improvement was evaluated as percentage of pigmentation clearance comparing the baseline findings with those at 3 months after the final treatment using a five category grading scale: Poor, 0-24%; Fair, 25-49%; Good, 50-74%; Excellent, 75-94%; and Complete, 95-100% improvement. Adverse events were also assessed. Results: All ten patients obtained clinical improvement ranging from fair to excellent. Treatment with the ps-Alex laser caused transient hyperpigmentation followed by improvement to complete resolution at 3 months follow-up. The ps-Nd:YAG laser caused severe transient erythema and swelling but no post-inflammatory hyperpigmentation. Conclusions: Our results suggest that the 755 nm and 1064 nm ps-lasers are efficacious for the treatment of dermal pigment lesions, with minimum adverse events.

  9. Picosecond pulse duration laser treatment for dermal melanocytosis in Asians : A retrospective review

    PubMed Central

    Ohshiro, Toshio; Sasaki, Katsumi; Kishi, Kazuo

    2016-01-01

    Background and aims: Recently novel picosecond duration lasers (ps-lasers) have been developed for the treatment of multicolored and recalcitrant tattoos, and safety and efficacy have been reported. We therefore hypothesized that the ps-laser could be an alternative treatment for dermal pigmented lesions and performed a retrospective review to evaluate the efficacy and safety of the ps-laser. Subjects and methods: A retrospective photographic review of 10 patients with dermal pigmented lesions was performed (ages from 4 months to 52 yr), 6 nevus of Ota, 3 ectopic Mongolian spots and 1 Mongolian spots. The patients were treated in the Ohshiro Clinic with picosecond 755 nm alexandrite laser (ps-Alex laser) and picosecond 1064 nm Nd:YAG laser (ps-Nd:YAG laser) from April 2014 to December 2015 (ps-Alex laser, 7 patients; ps-Nd:YAG laser, 3 patients, 1 to 3 treatment sessions). Improvement was evaluated as percentage of pigmentation clearance comparing the baseline findings with those at 3 months after the final treatment using a five category grading scale: Poor, 0–24%; Fair, 25–49%; Good, 50–74%; Excellent, 75–94%; and Complete, 95–100% improvement. Adverse events were also assessed. Results: All ten patients obtained clinical improvement ranging from fair to excellent. Treatment with the ps-Alex laser caused transient hyperpigmentation followed by improvement to complete resolution at 3 months follow-up. The ps-Nd:YAG laser caused severe transient erythema and swelling but no post-inflammatory hyperpigmentation. Conclusions: Our results suggest that the 755 nm and 1064 nm ps-lasers are efficacious for the treatment of dermal pigment lesions, with minimum adverse events. PMID:27721561

  10. 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

  11. Differential processing for frequency chirp measurement using optical pulse synthesizer

    NASA Astrophysics Data System (ADS)

    Kashiwagi, Ken; Seki, Satoshi; Tsuda, Hiroyuki; Takenouchi, Hirokazu; Kurokawa, Takashi

    2017-03-01

    In this study, we introduced an optical pulse synthesizer (OPS) to measure frequency chirps of optical pulses by differential processing. The OPS has a single-chip integrated structure of all elements for the differential filtering and enables stable measurement. Because the exact filter causes a large loss, we employed a phase-only filter, whose frequency response was only in phase. We measured chirp rates of pulses which were induced by propagating standard single mode fibers with different lengths. The retrieved chirp rates were comparable to calculated results. We simulated accuracy of the method and concluded that our experiment had phase control accuracy within 0.07π.

  12. 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.

  13. Validation of a software program for measuring fatigue-related changes in keystroke durations.

    PubMed

    Kim, Jeong Ho; Johnson, Peter W

    2011-01-01

    Intensive computer use has been associated with musculoskeletal disorders (MSDs). Although the underlying mechanisms are still not fully understood, muscle fatigue is thought to be a contributing factor. Previous studies have shown that keystroke durations are related to muscle twitch durations and may be used as a surrogate measure of muscle fatigue. Software tools have been developed to measure keystroke durations; however, the accuracy of these programs may be influenced by the computer and/or the operating system (OS). Keystrokes were collected from six subjects and analyzed to determine whether there were any differences in keystroke durations measured by an OS-dependant software program and keystrokes collected directly from the keyboard using a USB analyzer (gold standard). The results demonstrated that the OS-dependant software program underestimated keystroke durations by 3.8 ms (103.5 vs. 107.3 ms; p < 0.0001) but keystroke durations at the individual level were highly correlated between the two systems (R(2) = 0.997). Despite the small differences, the high correlation between systems indicated that the software program could be used to collect keystroke durations.

  14. Magnetic plethysmograph transducers for local blood pulse wave velocity measurement.

    PubMed

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

    2014-01-01

    We present the design of magnetic plethysmograph (MPG) transducers for detection of blood pulse waveform and evaluation of local pulse wave velocity (PWV), for potential use in cuffless blood pressure (BP) monitoring. The sensors utilize a Hall effect magnetic field sensor to capture the blood pulse waveform. A strap based design is performed to enable reliable capture of large number of cardiac cycles with relative ease. The ability of the transducer to consistently detect the blood pulse is verified by in-vivo trials on few volunteers. A duality of such transducers is utilized to capture the local PWV at the carotid artery. The pulse transit time (PTT) between the two detected pulse waveforms, measured along a small section of the carotid artery, was evaluated using automated algorithms to ensure consistency of measurements. The correlation between the measured values of local PWV and BP was also investigated. The developed transducers provide a reliable, easy modality for detecting pulse waveform on superficial arteries. Such transducers, used for measurement of local PWV, could potentially be utilized for cuffless, continuous evaluation of BP at various superficial arterial sites.

  15. Rapid scanning autocorrelator for measurements of picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Harde, H.; Burggraf, H.

    1981-08-01

    A rapid scanning autocorrelation interferometer for measurements of picosecond laser pulses is described which uses a rotating prism as scanning device in one arm of the interferometer to permit continuous display of autocorrelation traces at audio frequencies on an oscilloscope. Scan widths of more than 500 ps with high linearity can be achieved. Autocorrelation measurements of picosecond pulses from a synchronously pumped mode-locked dye laser are presented.

  16. Measuring alpha eigenvalue of a subcritical system by a intense pulsed neutron source

    SciTech Connect

    Hu, Meng-chun; Gong, Jian; Peng, Tai-ping; Li, Zhong-bao; Zhang, Jian-hua; Tang, Deng-pan; Bai, Yun; Peng, Xian-jue; Zeng, Qing

    2015-07-01

    Intense-Pulsed-Neutron-Source (IPNS) technique is a new approach to measure the subcriticality of a reactor system, which has been theoretically analyzed by us while not been verified in experiment in other reference. In INPS technique the reactivity is derived via the system response to a prompt pulsed neutron source. The method utilizes very intense neutron pulses (about 1010 neutrons/pulse) with the duration ranging from 10 ns to 100 ns, which are generated by the dense plasma focus (DPF) device filled with pure DT mixture as the working gas. The neutron pulse in high intensity provides the opportunity to measure the signal using a scintillator and a photo-multiplier tube (PMT) (the intense pulse radiation measure method) with the flight distance of only twenty centimeters. The attenuation of the dense plasma focus device must be faster than the subcritical system so that the attenuation of the system can be researched. In this paper, after a neutron pulse is injected into the subcritical reactor, the subcriticality is determined by measuring the instantaneous characteristics of the leaking reactor neutron. The Monte Carlo analysis shows that, with the linear arrangement of the dense plasma focus, the subcritical system and the detector, the signal-to-noise ratio at the measure point meets the investigate requirement, in which the 14 MeV neutrons are attenuated by the subcritical system. The detector is close with the subcritical system to reduce the influence of the outer background and the spread of time-of-flight of the neutrons. The measure system utilizing gated detection technology is characterized with fast attenuation time and large linear current, the a value obtained with this method is 2.05 μs{sup -1} while the measurements using the {sup 252}Cf stochastic pulsed source method and the Rossi-a method were 2.18μs{sup -1} and 2.16μs{sup -1}.It showed that the measured result obtained with dense plasma focus instantaneous pulsed source is consistent

  17. 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.

  18. 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.

  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. Influence of loading pulse duration on dynamic load transfer in a simulated granular medium

    NASA Astrophysics Data System (ADS)

    Shukla, A.; Sadd, M. H.; Xu, Y.; Tai, Q. M.

    1993-11-01

    AN EXPERIMENTAL and numerical investigation was conducted to study the dynamic response of granular media when subjected to impact loadings with different periods or wavelengths. The granular medium was simulated by a one-dimensional assembly of circular disks arranged in a straight single chain. In the experimental study, the dynamic loading was produced using projectile impact from a gas gun onto one end of the granular assembly, and the measured wave signal was collected using strain gages. The numerical simulations were conducted using the distinct element method. It was found from the experiments and numerical simulations that input waves with a short period (τ ≈ 90 μs) will propagate in this granular medium with little waveform change under steady amplitude attenuation ; whereas longer waves (τ $̆200 μs) will propagate with significant waveform dispersion. For these longer wavelength signals, the smooth waveform will undergo separation into a series of short oscillatory signals, and this rearrangement of energy allows a portion of the transmitted signal to increase in amplitude during the initial phases of propagation. Thus the granular medium acts as a nonlinear wave guide, and local microstructure and contact nonlinearity will allow input signals of sufficiently long wavelength to excite resonant sub-units of the medium to produce this observed ringing separation. Following a modeling scheme originally proposed by NESTERENKO[J. Appl. Mech. Tech. Phys. 5,733 (1983)], a nonlinear wave equation model was developed which is related to soliton dynamics and leads to travelling wave solutions of specific wavelength found in our experimental and numerical studies.

  1. EML pulse ionization chamber systems for /sup 222/Rn measurements

    SciTech Connect

    Fisenne, I M; Keller, H W

    1985-03-01

    Radon measurements have been performed with pulse ionization chambers at the Environmental Measurements Laboratory (EML) for over 35 years. This report describes the evolution of radon measurement systems, with emphasis on the continuous quality control efforts at EML. 38 refs., 3 figs., 3 tabs.

  2. Pulse train fluorescence technique for measuring triplet state dynamics.

    PubMed

    De Boni, Leonardo; Franzen, Paulo L; Gonçalves, Pablo J; Borissevitch, Iouri E; Misoguti, Lino; Mendonça, Cleber R; Zilio, Sergio C

    2011-05-23

    We report on a method to study the dynamics of triplet formation based on the fluorescence signal produced by a pulse train. Basically, the pulse train acts as sequential pump-probe pulses that precisely map the excited-state dynamics in the long time scale. This allows characterizing those processes that affect the population evolution of the first excited singlet state, whose decay gives rise to the fluorescence. The technique was proven to be valuable to measure parameters of triplet formation in organic molecules. Additionally, this single beam technique has the advantages of simplicity, low noise and background-free signal detection.

  3. Yeast cell inactivation related to local heating induced by low-intensity electric fields with long-duration pulses.

    PubMed

    Guyot, Stéphane; Ferret, Eric; Boehm, Jean-Baptiste; Gervais, Patrick

    2007-01-25

    The effects of electric field (EF) treatments on Saccharomyces cerevisiae viability were investigated using a PG200 electroporator (Hoefer Scientific Instrument, San Fransisco, CA, USA) with specific attention to induced thermal effects on cell death. Lethal electric fields (1.5 kV cm(-1) for 5 s) were shown to cause heat variations in the cell suspension medium (water+glycerol), while corresponding classical thermal treatments at equivalent temperatures had no effect on the cells viability. Variations of the electrical conductivity of the intra- and extracellular matrix caused by ions and solutes transfer across the membrane were shown to be involved in the observed heating. The results permitted to build a theoretical model for the temperature variations induced by electric fields. Using this model and the electrical conductivity of the different media, a plausible explanation of the cell death induced by low-intensity electric fields with long-duration pulses has been proposed. Indeed, cell mortality could in part be caused by direct and indirect effects of electric fields. Direct effects are related to well known electromechanical phenomena, whereas indirect effects are related to secondary thermal stress caused by plasma membrane thermoporation. This thermoporation was attributed to electrical conductivity variations and the corresponding intracellular heating.

  4. 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.

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

    PubMed

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

    2014-01-01

    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.

  6. 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

  7. Measurements of femtosecond pulse temporal profile by means of a Michelson interferometer with a Schottky junction.

    PubMed

    Ling, Yan; Lu, Fang

    2006-12-20

    We introduce a new method for femtosecond pulse shape measurement. The interference of two pulses is employed rather than the second-harmonic generation (SHG). Usually, the measurements of the femtosecond pulse is realized by an interferometer in combination with a nonlinear optical material, while the measurement that we describe is realized by means of a Michelson interferometer with a Schottky junction. Only a metal-semiconductor junction (Schottky junction) is needed, and neither the nonlinear optical material nor a photodetector is included. The two-photon absorption arises when the light is strong enough, while there is only a one-photon absorption when the light is weak. And the calculations are in good agreement with the experimental results. In principle, the new technique could be used for the measuring of pulses with any duration and with very low power. Unlike the SHG scheme, in the new method the quality of optics, mechanics, and other elements of the scheme are not essential, and the measurement is easily realized, but the results are quite precise and very sensitive to the light.

  8. 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.

  9. 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.

  10. 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

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

    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.

  11. Magneto-chiral dichroism measurements using a pulsed electromagnet

    NASA Astrophysics Data System (ADS)

    Hattori, Shingo; Yamamoto, Yusuke; Miyatake, Tomohiro; Ishii, Kazuyuki

    2017-04-01

    A system for measuring magneto-chiral dichroism (MChD) under strong magnetic fields using a pulsed electromagnet was constructed. We succeeded in observing a relatively intense MChD signal for chiral J-aggregates of a zinc chlorin at 5 T using this measurement system. This study will be useful for observing weak MChD signals of various organic molecules.

  12. 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.

  13. 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.

  14. 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

  15. Sensors for Measurement of Intense Electromagnetic Pulses

    DTIC Science & Technology

    1981-06-01

    to measure. The FMM (flush moebius mutual inductance) has been suc- cessfully used here, as well as a modified FPD design. Electric field (open... moebius loop) design has been most commonly used for this appli- cation, although both TML (twin moebius loop) and MHL (multi-turn hardened loop...concern. There are the OMM (outside moebius mutual inductance), FMM (flush moebius mutual inductance), and IMM (inside moebius mutual inductance). The

  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.

    2016-11-01

    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. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Lethality of Bacillus Anthracis Spores Due to Short Duration Heating Measured Using Infrared Spectroscopy

    DTIC Science & Technology

    2005-03-01

    wavelengths were these differences distinguished. Individual bacterial endospores from four species of Bacillus (cereus, megaterium , subtilis, and... Bacillus (cereus, megaterium , and subtilis) at various wavelengths. Spectral comparisons were made between spores and vegetative cells. Results...LETHALITY OF BACILLUS ANTHRACIS SPORES DUE TO SHORT DURATION HEATING MEASURED USING INFRARED SPECTROSCOPY THESIS Kristina M

  2. Precision CMB measurements with long-duration stratospheric balloons: activities in the Arctic

    NASA Astrophysics Data System (ADS)

    de Bernardis, P.; Masi, S.; OLIMPO and LSPE Teams

    2013-01-01

    We report on the activities preparing long duration stratospheric flights, suitable for CMB (Cosmic Microwave Background) measurements, in the Arctic region. We focus on pathfinder flights, and on two forthcoming experiments to be flown from Longyearbyen (Svalbard islands): the OLIMPO Sunyaev-Zeldovich spectrometer, and the Large-Scale Polarization Explorer (LSPE).

  3. Accurate measurement of the pulse wave delay with imaging photoplethysmography

    PubMed Central

    Kamshilin, Alexei A.; Sidorov, Igor S.; Babayan, Laura; Volynsky, Maxim A.; Giniatullin, Rashid; Mamontov, Oleg V.

    2016-01-01

    Assessment of the cardiovascular parameters using noncontact video-based or imaging photoplethysmography (IPPG) is usually considered as inaccurate because of strong influence of motion artefacts. To optimize this technique we performed a simultaneous recording of electrocardiogram and video frames of the face for 36 healthy volunteers. We found that signal disturbances originate mainly from the stochastically enhanced dichroic notch caused by endogenous cardiovascular mechanisms, with smaller contribution of the motion artefacts. Our properly designed algorithm allowed us to increase accuracy of the pulse-transit-time measurement and visualize propagation of the pulse wave in the facial region. Thus, the accurate measurement of the pulse wave parameters with this technique suggests a sensitive approach to assess local regulation of microcirculation in various physiological and pathological states. PMID:28018731

  4. 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 niobates (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 sensors U95 estimated combined uncertainty could decrease to ~0.025% for DC, AC, and pulsed voltage measurements.

  5. Constant-Frequency Pulsed Phase-Locked-Loop Measuring Device

    NASA Technical Reports Server (NTRS)

    Yost, William T.; Cantrell, John H.; Kushnick, Peter W.

    1992-01-01

    Constant-frequency pulsed phase-locked-loop measuring device is sensitive to small changes in phase velocity and easily automated. Based on use of fixed-frequency oscillator in measuring small changes in ultrasonic phase velocity when sample exposed to such changes in environment as changes in pressure and temperature. Automatically balances electrical phase shifts against acoustical phase shifts to obtain accurate measurements of acoustical phase shifts.

  6. 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.

  7. 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.

  8. Absolute distance measurement by chirped pulse interferometry using a femtosecond pulse laser.

    PubMed

    Wu, Hanzhong; Zhang, Fumin; Liu, Tingyang; Meng, Fei; Li, Jianshuang; Qu, Xinghua

    2015-11-30

    We propose here a method for absolute distance measurement by chirped pulse interferometry using frequency comb. The principle is introduced, and the distance can be measured via the shift of the widest fringe. The experimental results show an agreement within 26 μm in a range up to 65 m, corresponding to a relative precision of 4 × 10-7, compared with a reference distance meter.

  9. 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.

    2016-05-01

    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.

  10. 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.

  11. Comparing Eye Tracking with Electrooculography for Measuring Individual Sentence Comprehension Duration

    PubMed Central

    Müller, Jana Annina; Wendt, Dorothea; Kollmeier, Birger; Brand, Thomas

    2016-01-01

    The aim of this study was to validate a procedure for performing the audio-visual paradigm introduced by Wendt et al. (2015) with reduced practical challenges. The original paradigm records eye fixations using an eye tracker and calculates the duration of sentence comprehension based on a bootstrap procedure. In order to reduce practical challenges, we first reduced the measurement time by evaluating a smaller measurement set with fewer trials. The results of 16 listeners showed effects comparable to those obtained when testing the original full measurement set on a different collective of listeners. Secondly, we introduced electrooculography as an alternative technique for recording eye movements. The correlation between the results of the two recording techniques (eye tracker and electrooculography) was r = 0.97, indicating that both methods are suitable for estimating the processing duration of individual participants. Similar changes in processing duration arising from sentence complexity were found using the eye tracker and the electrooculography procedure. Thirdly, the time course of eye fixations was estimated with an alternative procedure, growth curve analysis, which is more commonly used in recent studies analyzing eye tracking data. The results of the growth curve analysis were compared with the results of the bootstrap procedure. Both analysis methods show similar processing durations. PMID:27764125

  12. The Relationship Between Submental Surface Electromyography and Hyo-Laryngeal Kinematic Measures of Mendelsohn Maneuver Duration

    PubMed Central

    Azola, Alba M.; Greene, Lindsey R.; Taylor-Kamara, Isha; Macrae, Phoebe; Anderson, Cheryl

    2015-01-01

    Purpose The Mendelsohn Maneuver (MM) is a commonly prescribed technique that is taught to individuals with dysphagia to improve swallowing ability. Due to cost and safety concerns associated with videofluoroscopy (VFS) use, submental surface electromyography (ssEMG) is commonly used in place of VFS to train the MM in clinical and research settings. However, it is unknown whether ssEMG accurately reflects the prolonged hyo-laryngeal movements required for execution of the MM. The primary goal of this study was to examine the relationship among ssEMG duration, duration of laryngeal vestibule closure, and duration of maximum hyoid elevation during MM performance. Method Participants included healthy adults and patients with dysphagia due to stroke. All performed the MM during synchronous ssEMG and VFS recording. Results Significant correlations between ssEMG duration and VFS measures of hyo-laryngeal kinematic durations during MM performance ranged from very weak to moderate. None of the correlations in the group of stroke patients reached statistical significance. Conclusion Clinicians and researchers should consider that the MM involves novel hyo-laryngeal kinematics that may be only moderately represented with ssEMG. Thus, there is a risk that these target therapeutic movements are not consistently being trained. PMID:26426312

  13. Real-time energy measurement of high repetition rate ultrashort laser pulses using pulse integration and FPGA processing.

    PubMed

    Tang, Qi-Jie; Yang, Dong-Xu; Wang, Jian; Feng, Yi; Zhang, Hong-Fei; Chen, Teng-Yun

    2016-11-01

    Real-time energy measurement using pulse integration method for high repetition rate ultrashort laser pulses based on FPGA (Field-Programmable Gate Array) and high-speed pipeline ADC (Analog-to-Digital Convertor) is introduced in this paper. There are two parts contained in this method: pulse integration and real-time data processing. The pulse integration circuit will convert the pulse to the step type signals which are linear to the laser pulse energy. Through the real-time data processing part, the amplitude of the step signals will be obtained by ADC sampling and conducting calculation in real time in FPGA. The test result shows that the method with good linearity (4.770%) and without pulse measurement missing is suitable for ultrashort laser pulses with high repetition rate up to 100 MHz.

  14. Real-time energy measurement of high repetition rate ultrashort laser pulses using pulse integration and FPGA processing

    NASA Astrophysics Data System (ADS)

    Tang, Qi-jie; Yang, Dong-xu; Wang, Jian; Feng, Yi; Zhang, Hong-fei; Chen, Teng-yun

    2016-11-01

    Real-time energy measurement using pulse integration method for high repetition rate ultrashort laser pulses based on FPGA (Field-Programmable Gate Array) and high-speed pipeline ADC (Analog-to-Digital Convertor) is introduced in this paper. There are two parts contained in this method: pulse integration and real-time data processing. The pulse integration circuit will convert the pulse to the step type signals which are linear to the laser pulse energy. Through the real-time data processing part, the amplitude of the step signals will be obtained by ADC sampling and conducting calculation in real time in FPGA. The test result shows that the method with good linearity (4.770%) and without pulse measurement missing is suitable for ultrashort laser pulses with high repetition rate up to 100 MHz.

  15. Pulsed photoacoustic Doppler flow measurements in blood-mimicking phantoms

    NASA Astrophysics Data System (ADS)

    Brunker, J.; Beard, P.

    2011-03-01

    The feasibility of making spatially resolved measurements of blood flow using pulsed photoacoustic Doppler techniques has been explored. Doppler time shifts were quantified via cross-correlation of pairs of photoacoustic waveforms generated within a blood-simulating phantom using pairs of laser light pulses. The photoacoustic waves were detected using a focussed or planar PZT ultrasound transducer. For each flow measurement, a series of 100 waveform pairs was collected. Previous data processing methods involved rejection of poorly correlated waveform pairs; the modal velocity value and standard deviation were then extracted from the selected distribution of velocity measurements. However, the data selection criteria used in this approach is to some extent arbitrary. A new data analysis protocol, which involves averaging the 100 cross-correlation functions and thus uses all of the measured data, has been designed in order to prevent exclusion of outliers. This more rigorous approach has proved effective for quantifying the linear motion of micron-scale absorbers imprinted on an acetate sheet moving with velocities in the range 0.14 to 1.25 ms-1. Experimental parameters, such as the time separation between the laser pulses and the transducer frequency response, were evaluated in terms of their effect on the accuracy, resolution and range of measurable velocities. The technique was subsequently applied to fluid phantoms flowing at rates less than 5 mms-1 along an optically transparent tube. Preliminary results are described for three different suspensions of phenolic resin microspheres, and also for whole blood. Velocity information was obtained even under non-optimal conditions using a low frequency transducer and a low pulse repetition frequency. The distinguishing advantage of pulsed rather than continuous-wave excitation is that spatially resolved velocity measurements can be made. This offers the prospect of mapping flow within the microcirculation and thus

  16. 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.

  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. Blood pulse wave velocity measured by photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Yeh, Chenghung; Hu, Song; Maslov, Konstantin; Wang, Lihong V.

    2013-03-01

    Blood pulse wave velocity (PWV) is an important indicator for vascular stiffness. In this letter, we present electrocardiogram-synchronized photoacoustic microscopy for in vivo noninvasive quantification of the PWV in the peripheral vessels of mice. Interestingly, strong correlation between blood flow speed and ECG were clearly observed in arteries but not in veins. PWV is measured by the pulse travel time and the distance between two spot of a chose vessel, where simultaneously recorded electrocardiograms served as references. Statistical analysis shows a linear correlation between the PWV and the vessel diameter, which agrees with known physiology. Keywords: photoacoustic microscopy, photoacoustic spectroscopy, bilirubin, scattering medium.

  19. Self-integrating inductive loop for measuring high frequency pulses

    NASA Astrophysics Data System (ADS)

    Rojas-Moreno, Mónica V.; Robles, Guillermo; Martínez-Tarifa, Juan M.; Sanz-Feito, Javier

    2011-08-01

    High frequency pulses can be measured by means of inductive sensors. The main advantage of these sensors consists of non-contact measurements that isolate and protect measuring equipment. The objective of this paper is to present the implementation of an inductive sensor for measuring rapidly varying currents. It consists of a rectangular loop with a resistor at its terminals. The inductive loop gives the derivative of the current according to Faraday's law and the resistor connected to the loop modifies the sensor's frequency response to obtain an output proportional to the current pulse. The self-integrating inductive sensor was validated with two sensors, a non-inductive resistor and a commercial high frequency current transformer. The results were compared to determine the advantages and drawbacks of the probe as an adequate inductive transducer.

  20. Electronic measurement of microchannel plate pulse height distributions

    SciTech Connect

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

    2010-10-15

    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 10{sup 3}-10{sup 5}, 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.

  1. Measuring ultracomplex supercontinuum pulses and spatio-temporal distortions

    NASA Astrophysics Data System (ADS)

    Gu, Xun

    This thesis contains two components of research: studies of supercontinuum pulses generated in the novel microstructure fiber, and research on spatio-temporal coupling in ultrafast laser beams. One of the most exciting developments in optics in recent years has been the invention of the microstructure optical fiber. By controlling the structural parameters of these novel fibers in design and manufacturing, their dispersion profile can be freely tailored, opening up a huge application base. One particularly interesting effect in the microstructure fiber is the generation of ultrabroadband supercontinuum with only nJ-level Ti:sapphire oscillator pulse pump. This supercontinuum is arguably the most complicated ultrafast pulse ever generated, with its huge time-bandwidth product (>1000 from a 16-cm-long fiber). Although many applications have been demonstrated or envisioned with this continuum, its generation is a very complicated process that is poorly understood, and the characteristics of the continuum pulses are not clearly known. In this work, we make a full-intensity-and-phase measurement of the continuum pulses using cross-correlation frequency-resolved optical gating (XFROG). The results reveal surprising unstable fine spectral structure in the continuum pulses, which is confirmed by single-shot measurements. Our study on the coherence of the continuum, on the other hand, shows that the spectral phase of the supercontinuum is fairly stable. Numerical simulations are carried out whose results are in good agreement with experiments. The second component of this thesis is the study of spatio-temporal coupling in ultrafast beams. We propose two definitions of spatial chirp, point out their respective physical meanings, and derive their relationship. On the common perception of the equivalence between pulse-front tilt and angular dispersion, we show that the equivalence only holds for plane waves. We establish a generalized theory of ultrafast laser beams with first

  2. ɛ -pseudoclassical model for quantum resonances in a cold dilute atomic gas periodically driven by finite-duration standing-wave laser pulses

    NASA Astrophysics Data System (ADS)

    Beswick, Benjamin T.; Hughes, Ifan G.; Gardiner, Simon A.; Astier, Hippolyte P. A. G.; Andersen, Mikkel F.; Daszuta, Boris

    2016-12-01

    Atom interferometers are a useful tool for precision measurements of fundamental physical phenomena, ranging from the local gravitational-field strength to the atomic fine-structure constant. In such experiments, it is desirable to implement a high-momentum-transfer "beam splitter," which may be achieved by inducing quantum resonance in a finite-temperature laser-driven atomic gas. We use Monte Carlo simulations to investigate these quantum resonances in the regime where the gas receives laser pulses of finite duration and derive an ɛ -classical model for the dynamics of the gas atoms which is capable of reproducing quantum resonant behavior for both zero-temperature and finite-temperature noninteracting gases. We show that this model agrees well with the fully quantum treatment of the system over a time scale set by the choice of experimental parameters. We also show that this model is capable of correctly treating the time-reversal mechanism necessary for implementing an interferometer with this physical configuration and that it explains an unexpected universality in the dynamics.

  3. Simultaneous measurement of magnetization and magnetostriction in 50 T pulsed high magnetic fields.

    PubMed

    Doerr, M; Lorenz, W; Neupert, T; Loewenhaupt, M; Kozlova, N V; Freudenberger, J; Bartkowiak, M; Kampert, E; Rotter, M

    2008-06-01

    To simultaneously perform magnetization and magnetostriction measurements in high magnetic fields, a miniaturized device was developed that combines an inductive magnetometer with a capacitive dilatometer and, therefore, it is called "dilamagmeter." This combination of magnetic and magnetoelastic investigations is a new step to a complex understanding of solid state properties. The whole system can be mounted in a 12 mm clear bore of any cryostat usually used in nondestructive pulsed high field magnets. The sensitivity of both methods is about 10(-5) A m(2) for magnetization and 10(-5) relative changes in length for striction measurements. Measurements on a GdSi single crystal, which are corrected by the background signal of the experimental setup, agree well with the results of steady field experiments. All test measurements, which are up until now performed in the temperature range of 4-100 K, confirm the perfect usability and high stability in pulsed fields up to 50 T with a pulse duration of 10 ms.

  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. Multifunctional optical correlator for picosecond ultraviolet laser pulse measurement

    DOE PAGES

    Rakhman, Abdurahim; Wang, Yang; Garcia, Frances; ...

    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

  6. 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.

  7. Precise measurement of magnetization characteristics in high pulsed field

    NASA Astrophysics Data System (ADS)

    Nakahata, Y.; Borkowski, B.; Shimoji, H.; Yamada, K.; Todaka, T.; Enokizono, M.

    2012-04-01

    Permanent magnets, especially Nd-Fe-B magnets, are very important engineering elements that are widely used in many applications. The detailed design of electrical and electronic equipment using permanent magnets requires the precise measurement of magnetization characteristics. High pulsed magnetic fields can be used to measure the magnetization characteristics of permanent magnets in the easy and hard magnetization directions. Errors influencing the measurements stem from the relationship between the tested material, pick-up sensor configuration, and excitation coil. We present an analysis of the effect of the sensor construction on the accuracy of the measurements of the material's magnetic properties. We investigated the coaxial and series types sensor configurations.

  8. 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.

  9. 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.

  10. Probabilistic model for estimating snow cover duration from ground temperature measurements in the Austrian Alpine region

    NASA Astrophysics Data System (ADS)

    Teubner, Irene; Haimberger, Leopold; Hantel, Michael; Dorigo, Wouter

    2016-04-01

    Snow cover duration represents a key climate parameter. Trends in the seasonal snow cover duration can be linked to changes of the mean annual air temperature and precipitation pattern and, therefore, can serve as a sentinel for climate change. Snow cover duration is commonly inferred from snow depth or snow water equivalent measurements provided by ground observations or satellites. Recently, methods have been developed to estimate the presence or absence of a snow cover from daily ground temperature variations. This method commonly includes the definition of station-specific thresholds. In our study, we propose to use a probabilistic model for determining a single threshold for the whole dataset. The model takes the daily range and/or the daily mean of ground temperature at 10 cm depth as input and is further calibrated with in situ snow depth observations. Applying the model to 87 measuring sites in the Austrian Alps, we showed that the snow cover estimation was improved when combining the daily range and the mean of ground temperature. Our results suggest that ground temperature records are a valuable source for the validation of satellite-derived snow cover, complementary to traditional ground-based snow measurements.

  11. 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.

  12. 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.

  13. STARE velocities: 3. Double-pulse and multi-pulse measurements

    NASA Astrophysics Data System (ADS)

    Uspensky, M.; Koustov, A.; Sofieva, V.; Amm, O.; Kauristie, K.; Schmidt, W.; Nielsen, E.; Pulkkinen, T.; Pellinen, R.; Pirjola, R.

    The STARE coherent radars are a powerfull instrument for studying the auroral zone electrodynamics, first of all with respect to plasma convection. For decades, the radars have been using the double-pulse (DP) technique to measure the velocity. Recently, the multi-pulse (MP) scheme has been implemented. The detailed comparisons (Uspensky et al., 2003, 2004) between EISCAT and STARE MP measurements showed a good performance of the MP scheme for convection estimates, contrary to the known difficulties of the DP method. In the present study we consider differences in the velocity estimates by the MP and DP schemes in order to evaluate the uncertainties of the convection predictions by the DP scheme. We confirm previous warnings by Schlegel et al. (1986) and Schlegel and Thomas (1988) that the STARE DP scheme with fixed pulse separation can give a systematic error in the velocity estimate. We show that the DP velocities are typically smaller than the MP velocities, especially for large flow angle observations in the afternoon/evening sector. We also report occasional cases of small DP velocity overestimations. It is argued that the observed differences between DP and MP velocities originate from a minor, but not negligible, correlation between the signals coming from the main and aliasing volumes of the DP scheme particularly under the condition of broad backscatter spectra.

  14. 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.

  15. Pulsed Raman measurements of lattice temperature: Validity tests

    NASA Astrophysics Data System (ADS)

    Compaan, A.; Lee, M. C.; Lo, H. W.; Trott, G. J.; Aydinli, A.

    1983-10-01

    We measure the temperature dependence of the Raman correction factors and present data on the spot size and transverse beam quality of lasers used in the pulsed Raman measurements of lattice temperature in Si. Recent criticisms are also evaluated and shown to be inappropriate or in error. Finally we measure the shift of the 520-cm-1 Raman line and find it also to be consistent with the observed Stokes/anti-Stokes ratios indicating optic phonon populations characteristic of ˜450 °C.

  16. Multiwavelength pulse oximetry in the measurement of hemoglobin fractions

    NASA Astrophysics Data System (ADS)

    Manzke, Bernd; Schwider, Johannes; Lutter, Norbert O.; Engelhardt, Kai; Stork, Wilhelm

    1996-04-01

    The two wavelength design of the majority of pulse oximeters assumes only two absorbing hemoglobin fractions, oxyhemoglobin (O2Hb), and reduced hemoglobin (HHb) irrespective of the presence of methemoglobin (MetHb) and carboxyhemoglobin (COHb). If MetHb or COHb is present, it contributes to the pulse-added absorbance signal and will be interpreted as either HHb or O2Hb or some combination of the two. In this paper we describe a noninvasive multi-wavelength pulse oximeter measuring O2Hb, HHb, MetHb, and COHb at a specified accuracy of 1.0%. The system was designed with respect to the results of numerical simulations. It consists of 9 laserdiodes (LDs) and 7 light emitting diodes (LEDs), a 16-bit analog-digital converter (ADC) and has a sampling rate of 16 kHz. The laser didoes and LEDs were coupled into multi-mode fibers and led with a liquid lightguide to the finger clip and then the photodiode. It also presents the results of a clinical study, including a setup with a quartz tungsten halogen lamp (with fiber output) and a diode array spectrometer, a standard pulse oximeter and two in-vitro oximeters (radiometer OSM3 and radiometer ABL 520) as references.

  17. Limitations and strategies to improve measurement accuracy in differential pulse-width pair Brillouin optical time-domain analysis sensing.

    PubMed

    Minardo, Aldo; Bernini, Romeo; Zeni, Luigi

    2013-05-01

    In this work, we analyze the effects of Brillouin gain and Brillouin frequency drifts on the accuracy of the differential pulse-width pair Brillouin optical time-domain analysis (DPP-BOTDA). In particular, we demonstrate numerically that the differential gain is highly sensitive to variations in the Brillouin gain and/or Brillouin shift occurring during the acquisition process, especially when operating with a small pulse pair duration difference. We also propose and demonstrate experimentally a method to compensate for these drifts and consequently improve measurement accuracy.

  18. 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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  1. 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}.

  2. Measurement duration impacts variability but not impedance measured by the forced oscillation technique in healthy, asthma and COPD subjects

    PubMed Central

    Watts, Joanna C.; Farah, Claude S.; Seccombe, Leigh M.; Handley, Blake M.; Schoeffel, Robin E.; Bertolin, Amy; Dame Carroll, Jessica; King, Gregory G.

    2016-01-01

    The forced oscillation technique (FOT) is gaining clinical acceptance, facilitated by more commercial devices and clinical data. However, the effects of variations in testing protocols used in FOT data acquisition are unknown. We describe the effect of duration of data acquisition on FOT results in subjects with asthma, chronic obstructive pulmonary disease (COPD) and healthy controls. FOT data were acquired from 20 healthy, 22 asthmatic and 18 COPD subjects for 60 s in triplicate. The first 16, 30 and 60 s of each measurement were analysed to obtain total, inspiratory and expiratory resistance of respiratory system (Rrs) and respiratory system reactance (Xrs) at 5 and 19 Hz. With increasing duration, there was a decrease in total and expiratory Rrs for healthy controls, total and inspiratory Rrs for asthmatic subjects and magnitude of total and inspiratory Xrs for COPD subjects at 5 Hz. These decreases were small compared to the differences between clinical groups. Measuring for 16, 30 and 60 s provided ≥3 acceptable breaths in at least 90, 95 and 100% of subjects, respectively. The coefficient of variation for total Rrs and Xrs also decreased with duration. Similar results were found for Rrs and Xrs at 19 Hz. FOT results are statistically, but likely minimally, impacted by acquisition duration in healthy, asthmatic or COPD subjects. PMID:27730194

  3. Associations of Objectively Measured and Self-Reported Sleep Duration With Carotid Artery Intima Media Thickness Among Police Officers

    PubMed Central

    Ma, Claudia C.; Burchfiel, Cecil M.; Charles, Luenda E.; Dorn, Joan M.; Andrew, Michael E.; Gu, Ja Kook; Joseph, Parveen Nedra; Fekedulegn, Desta; Slaven, James E.; Hartley, Tara A.; Mnatsakanova, Anna; Violanti, John M.

    2015-01-01

    Background We aimed to examine the association of objectively measured and self-reported sleep duration with carotid artery intima media thickness (IMT) among 257 police officers, a group at high risk for cardiovascular disease (CVD). Methods Sleep duration was estimated using actigraphic data and through self-reports. The mean maximum IMT was the average of the largest 12 values scanned bilaterally from three angles of the near and far wall of the common carotid, bulb, and internal carotid artery. Linear and quadratic regression models were used to assess the association of sleep duration with IMT. Results Officers who had fewer than 5 or 8 hr or more of objectively measured sleep duration had significantly higher maximum IMT values, independent of age. Self-reported sleep duration was not associated with either IMT measure. Conclusion Attainment of sufficient sleep duration may be considered as a possible strategy for atherosclerosis prevention among police officers. PMID:24038303

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Ultrasonic pulsed phase locked loop interferometer for bolt load measurements

    NASA Technical Reports Server (NTRS)

    Allison, S. G.; Clendenin, C. G.

    1989-01-01

    The pulsed phase-locked-loop bolt monitor (P2L2) that uses ultrasonic waves to measure bolt preload with accuracies ranging from 1 to 3 percent (depending on the specific bolt) is described. To remeasure bolt load after installation, a thermal calibration factor compensates for bolt temperature changes, and a standard reference block allows correction for acoustic phase errors due to measurement equipment configuration such as utilization of a different transducer, couplant, or cable. Some examples of critical applications including Space Shuttle landing-gear wheels and NASA wind-tunnel fan blades are discussed.

  10. Measurement of pulse pressure in plasma by crusher gauge

    SciTech Connect

    Kalachnikov, E.V.; Rogovtsev, P.N.

    1988-06-01

    Results are presented of pressure measurements in the plasma of a stabilized pinched discharge with axial blow through of the current channel by plasma using static and dynamic methods for crusher gauge calibration. Accuracies for maximum pressure measurements for both calibration methods are evaluated. The dynamic properties of the crusher gauge are taken into account experimentally in studying pulse forces and pressures in the 1-100 MPa range for times of 10/sup /minus/5/ to 10/sup /minus/3/ seconds. A piezoelectric method and device for dynamic calibration of the pressure gauges is described.

  11. 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.

  12. Airborne Double Pulsed 2-Micron IPDA Lidar for Atmospheric CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Singh, Upendra

    2015-01-01

    We have developed an airborne 2-micron Integrated Path Differential Absorption (IPDA) lidar for atmospheric CO2 measurements. The double pulsed, high pulse energy lidar instrument can provide high-precision CO2 column density measurements.

  13. 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.

  14. 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.

  15. Optimization of passively mode-locked Nd:GdVO4 laser with the selectable pulse duration 15-70 ps

    NASA Astrophysics Data System (ADS)

    Frank, Milan; Jelínek, Michal; Vyhlídal, David; Kubeček, Václav

    2016-12-01

    In this paper the optimization of a continuously diode-pumped Nd:GdVO4 laser oscillator in bounce geometry passively mode-locked using semiconductor saturable absorber mirror is presented. In the previous results the Nd:GdVO4 laser system generating 30 ps pulses with the average output power of 6.9 W at the repetition rate of 200 MHz at the wavelength of 1063 nm was reported. Now we are demonstrating up to three times increase of peak power due to the optimization of mode-matching in the laser resonator. Depending on the oscillator configuration we obtained the stable continuously mode-locked operation with pulses having selectable duration from 15 ps to 70 ps with the average output power of 7 W and the repetition rate of 150 MHz.

  16. Ultrasonic Power Output Measurement by Pulsed Radiation Pressure.

    PubMed

    Fick, Steven E; Breckenridge, Franklin R

    1996-01-01

    Direct measurements of time-averaged spatially integrated output power radiated into reflectionless water loads can be made with high accuracy using techniques which exploit the radiation pressure exerted by sound on all objects in its path. With an absorptive target arranged to intercept the entirety of an ultrasound beam, total beam power can be determined as accurately as the radiation force induced on the target can be measured in isolation from confounding forces due to buoyancy, streaming, surface tension, and vibration. Pulse modulation of the incident ultrasound at a frequency well above those characteristics of confounding phenomena provides the desired isolation and other significant advantages in the operation of the radiation force balance (RFB) constructed in 1974. Equipped with purpose-built transducers and electronics, the RFB is adjusted to equate the radiation force and a counterforce generated by an actuator calibrated against reference masses using direct current as the transfer variable. Improvements made during its one overhaul in 1988 have nearly halved its overall measurement uncertainty and extended the capabilities of the RFB to include measuring the output of ultrasonic systems with arbitrary pulse waveforms.

  17. Ultrasonic Power Output Measurement by Pulsed Radiation Pressure

    PubMed Central

    Fick, Steven E.; Breckenridge, Franklin R.

    1996-01-01

    Direct measurements of time-averaged spatially integrated output power radiated into reflectionless water loads can be made with high accuracy using techniques which exploit the radiation pressure exerted by sound on all objects in its path. With an absorptive target arranged to intercept the entirety of an ultrasound beam, total beam power can be determined as accurately as the radiation force induced on the target can be measured in isolation from confounding forces due to buoyancy, streaming, surface tension, and vibration. Pulse modulation of the incident ultrasound at a frequency well above those characteristics of confounding phenomena provides the desired isolation and other significant advantages in the operation of the radiation force balance (RFB) constructed in 1974. Equipped with purpose-built transducers and electronics, the RFB is adjusted to equate the radiation force and a counterforce generated by an actuator calibrated against reference masses using direct current as the transfer variable. Improvements made during its one overhaul in 1988 have nearly halved its overall measurement uncertainty and extended the capabilities of the RFB to include measuring the output of ultrasonic systems with arbitrary pulse waveforms. PMID:27805084

  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.

  19. 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.

  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. Associations Between Step Duration Variability and Inertial Measurement Unit Derived Gait Characteristics.

    PubMed

    Rantalainen, Timo; Hart, Nicolas H; Nimphius, Sophia; Wundersitz, Daniel W

    2016-08-01

    Inertial measurement units (IMU) provide a convenient tool for gait stability assessment. However, it is unclear how various gait characteristics relate to each other and whether gait characteristics can be obtained from resultant acceleration. Therefore, step duration variability was measured in treadmill walking from 39 young ambulant volunteers (age 24.2 [± 2.5] y; height 1.79 [± 0.09] m; mass 71.6 [± 12.0] kg) using motion capture. Accelerations and gyrations were simultaneously recorded with an IMU. Harmonic ratio, maximum Lyapunov exponents, and multiscale sample entropy (MSE) were calculated. Step duration variability was positively associated with MSE with coarseness levels = 3-6 (r = -.33 to -.42, P ≤ .045). Harmonic ratio and MSE with all coarseness levels were negatively associated (r = -.45 to -.57, P ≤ .004). The MSE with coarseness level = 2 was negatively associated with short-term maximum Lyapunov exponents (r = -.32, P = .047). The agreement between resultant and vertical acceleration derived gait characteristics was excellent (ICC = 0.97-0.99). In conclusion, MSE with varying coarseness levels was associated with the other gait characteristics evaluated in the study. Resultant and vertical acceleration derived results had excellent agreement, which suggests that resultant acceleration is a viable alternative to considering the acceleration dimensions independently.

  2. 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.

  3. Neutron lifetime measurement with pulsed beam at JPARC: Overview

    NASA Astrophysics Data System (ADS)

    Mishima, Kenji; Ino, Takashi; Taketani, Kaoru; Yamada, Takahito; Katayama, Ryo; Higashi, Nao; Yokoyama, Harumichi; Sumino, Hirochika; Yamashita, Satoru; Sakakibara, Risa; Sugino, Tomoaki; Kitaguchi, Masaaki; Hirota, Katsuya; Shimizu, Hirohiko M.; Tanaka, Genki; Sumi, Naoyuki; Otono, Hidetoshi; Yoshioka, Tamaki; Kitahara, Ryunosuke; Iwashita, Yoshihisa; Oide, Hideyuki; Shima, Tatsushi; Seki, Yoshichika; NOP Collaboration

    2014-09-01

    The neutron lifetime is an important parameter for a test of the Standard Model of elementary particles, as well for the production of light mass nuclei in big bang nucleosynthesis. There are two principally different approaches to measure the neutron lifetime: In-beam methods and storage of ultracold neutron. At present, there is a discrepancy of 8.4 sec (3.8 sigma) between the two methods. We are performing a new In-beam experiment with an intense pulsed neutron source at J-PARC, which has different systematic uncertainties from the previous experiments. We introduce the overview of the experiment and report present status.

  4. Pulsed Electron Beam Spectroscopy for Temperature Measurements in Hypersonic Flows

    DTIC Science & Technology

    2010-01-01

    atmospheric pr essures wit hin the fligh t envelope of scramjet-powered flight vehicles. Because of the pressure disparity between measured flow and me...represents what might be o btained from the pulse d e-beam s ystem if it were used in the high-te mperature (but high-pr essure ) st agnation cha...di fferential pressure pump has been developed for pressure separations up to approximately 1 torr. F or higher pr essures , a f ast act ion r otary

  5. 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.

  6. 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

  7. Post-exercise left ventricular dysfunction measured after a long-duration cycling event

    PubMed Central

    2013-01-01

    Background In this research, an extension to our previous work published in the Clinical Journal of Sports Medicine in 2009, we studied subjects that differed in terms of age and training status and assessed the impact of prolonged exercise on systolic and left ventricular diastolic function and cardiac biomarkers levels, recognized as identifiers of cardiac damage and dysfunction. We also assessed the possible influence of event duration, exercise intensity and weight loss (dehydration) on left ventricular diastolic function. Findings Ninety-one male cyclists were assessed by echocardiography and serum biomarkers before and after the 2005 Quebrantahuesos cycling event (206 km long and with an accumulated slope of 3800 m). Cardiac function was assessed by echocardiography and cardiac biomarkers were assessed in blood serum. Echocardiograms measured left ventricular internal dimension during diastole and systole, left ventricular posterior wall thickness during diastole, interventricular septum thickness during diastole, left ventricular ejection fraction and diastolic filling. The heart rate of 50 cyclists was also monitored during the race to evaluate exercise intensity. Echocardiograph results indicated that left ventricular diastolic and systolic function decreased after the race, with systolic function reduced to a significant degree. Left ventricular ejection fraction was below 55% in 29 cyclists. The decrease in left ventricular systolic and diastolic function did not correlate with age, training status, race duration, weight loss or exercise intensity. Conclusions Left ventricular systolic and diastolic function was reduced and cardiac biomarkers were increased after the cycling event, but the mechanisms behind such outcomes remain unclear. PMID:23706119

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  9. An improved visualization-based force-measurement technique for short-duration hypersonic facilities

    NASA Astrophysics Data System (ADS)

    Laurence, Stuart J.; Karl, Sebastian

    2010-06-01

    This article is concerned with describing and exploring the limitations of an improved version of a recently proposed visualization-based technique for the measurement of forces and moments in short-duration hypersonic wind tunnels. The technique is based on tracking the motion of a free-flying body over a sequence of high-speed visualizations; while this idea is not new in itself, the use of high-speed digital cinematography combined with a highly accurate least-squares tracking algorithm allows improved results over what have been previously possible with such techniques. The technique precision is estimated through the analysis of artificially constructed and experimental test images, and the resulting error in acceleration measurements is characterized. For wind-tunnel scale models, position measurements to within a few microns are shown to be readily attainable. Image data from two previous experimental studies in the T5 hypervelocity shock tunnel are then reanalyzed with the improved technique: the uncertainty in the mean drag acceleration is shown to be reduced to the order of the flow unsteadiness, 2-3%, and time-resolved acceleration measurements are also shown to be possible. The response time of the technique for the configurations studied is estimated to be ˜0.5 ms. Comparisons with computations using the DLR TAU code also yield agreement to within the overall experimental uncertainty. Measurement of the pitching moment for blunt geometries still appears challenging, however.

  10. Polysomnographic Measurement of Sleep Duration and Bodily Pain Perception in the Sleep Heart Health Study

    PubMed Central

    Weingarten, Jeremy A.; Dubrovsky, Boris; Basner, Robert C.; Redline, Susan; George, Liziamma; Lederer, David J.

    2016-01-01

    Study Objectives: To determine whether total sleep time (TST) and specific sleep stage duration are associated with bodily pain perception and whether sex, age, or subjective sleepiness modifies this relationship. Methods: Data from adults ages 39–90 y (n = 5,199) who took part in the Sleep Heart Health Study Exam 1 were analyzed. TST, rapid eye movement (REM) sleep time, and slow wave sleep (SWS) time were measured by unattended, in-home nocturnal polysomnography. Bodily pain perception was measured via the Short Form-36 questionnaire bodily pain component. We used logistic regression to examine associations between total and individual sleep stage durations and bodily pain perception controlling for age, sex, race, body mass index, apnea-hypopnea index, antidepressant use, and important cardiovascular conditions (smoking [pack-years], history of diabetes, and history of percutaneous coronary intervention and/or coronary artery bypass graft). Results: In the fully adjusted model, REM sleep time and SWS time were not associated with “moderate to severe pain,” whereas TST was: Each 1-h decrement in TST was associated with a 7% increased odds of “moderate to severe pain” (odds ratio 1.07, 95% confidence interval 1.002, 1.14). Due to modification of the association between SWS time and “moderate to severe pain” by sex (P for interaction = 0.01), we performed analyses stratified by sex: Each 1-h decrement in SWS time was associated with a 20% higher odds of “moderate to severe pain” among men (odds ratio 1.20, 95% confidence interval 1.03–1.42) whereas an association was not observed among women. Conclusions: Shorter TST among all subjects and shorter SWS time in men was associated with “moderate to severe pain.” REM sleep time was not associated with bodily pain perception in this cohort. Citation: Weingarten JA, Dubrovsky B, Basner RC, Redline S, George L, Lederer DJ. Polysomnographic measurement of sleep duration and bodily pain perception in

  11. Vibration measurement based on the optical cross-correlation technique with femtosecond pulsed laser

    NASA Astrophysics Data System (ADS)

    Han, Jibo; Wu, Tengfei; Zhao, Chunbo; Li, Shuyi

    2016-10-01

    Two vibration measurement methods with femtosecond pulsed laser based on the optical cross-correlation technique are presented independently in this paper. The balanced optical cross-correlation technique can reflect the time jitter between the reference pluses and measurement pluses by detecting second harmonic signals using type II phase-matched nonlinear crystal and balanced amplified photo-detectors. In the first method, with the purpose of attaining the vibration displacement, the time difference of the reference pulses relative to the measurement pluses can be measured using single femtosecond pulsed laser. In the second method, there are a couple of femtosecond pulsed lasers with high pulse repetition frequency. Vibration displacement associated with cavity length can be calculated by means of precisely measuring the pulse repetition frequency. The results show that the range of measurement attains ±150μm for a 500fs pulse. These methods will be suited for vibration displacement measurement, including laboratory use, field testing and industrial application.

  12. Measurement of Seebeck coefficient using a light pulse

    NASA Technical Reports Server (NTRS)

    Wood, C.; Zoltan, D.; Stapfer, G.

    1985-01-01

    A high-temperature (1900 K) Seebeck coefficient apparatus is described in which small thermal gradients are generated in a sample by light pulses transmitted via light pipes. By employing an analog subtraction circuit, the Seebeck coefficient is displayed directly on an X-Y recorder. This technique presents a convenient, accurate, and rapid method for measuring the Seebeck coefficient in highly doped semiconductors as a function of temperature. The nature of the resulting display (X-Y recording) is a valuable tool in determining validity of the data. A straight line results (i.e., a minimum of hysteresis) only if all potential experimental errors are minimized. Under these conditions, the error of measurements of the Seebeck coefficient is estimated to be less than + or - 1 percent.

  13. 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.

  14. Aerosol Measurements by the Globally Distributed Micro Pulse Lidar Network

    NASA Technical Reports Server (NTRS)

    Spinhirne, James; Welton, Judd; Campbell, James; Berkoff, Tim; Starr, David (Technical Monitor)

    2001-01-01

    Full time measurements of the vertical distribution of aerosol are now being acquired at a number of globally distributed MP (micro pulse) lidar sites. The MP lidar systems provide full time profiling of all significant cloud and aerosol to the limit of signal attenuation from compact, eye safe instruments. There are currently eight sites in operation and over a dozen planned. At all sited there are also passive aerosol and radiation measurements supporting the lidar data. Four of the installations are at Atmospheric Radiation Measurement program sites. The network operation includes instrument operation and calibration and the processing of aerosol measurements with standard retrievals and data products from the network sites. Data products include optical thickness and extinction cross section profiles. Application of data is to supplement satellite aerosol measurements and to provide a climatology of the height distribution of aerosol. The height distribution of aerosol is important for aerosol transport and the direct scattering and absorption of shortwave radiation in the atmosphere. Current satellite and other data already provide a great amount of information on aerosol distribution, but no passive technique can adequately resolve the height profile of aerosol. The Geoscience Laser Altimeter System (GLAS) is an orbital lidar to be launched in early 2002. GLAS will provide global measurements of the height distribution of aerosol. The MP lidar network will provide ground truth and analysis support for GLAS and other NASA Earth Observing System data. The instruments, sites, calibration procedures and standard data product algorithms for the MPL network will be described.

  15. 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.

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

    PubMed

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

    2016-02-13

    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.

  17. 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

  18. Theory of photoselection by intense light pulses. Influence of reorientational dynamics and chemical kinetics on absorbance measurements.

    PubMed Central

    Ansari, A; Szabo, A

    1993-01-01

    The theory of absorbance measurements on a system (e.g., chromophore(s) in a protein) that undergoes a sequence of reactions initiated by a linearly polarized light pulse is developed for excitation pulses of arbitrary intensity. This formalism is based on a set of master equations describing the time evolution of the orientational distribution function of the various species resulting from excitation, reorientational dynamics, and chemical kinetics. For intense but short excitation pulses, the changes in absorbance (for arbitrary polarization directions of the excitation and probe pulses) and the absorption anisotropy are expressed in terms of reorientational correlation functions. The influence of the internal motions of the chromophore as well as the overall motions of the molecules is considered. When the duration of the excitation pulse is long compared to the time-scale of internal motions but comparable to the overall correlation time of the molecule that is reorienting isotropically, the problem of calculating the changes in absorbance is reduced to the solution of a set of first-order coupled differential equations. Emphasis is placed on obtaining explicit results for quantities that are measured in photolysis and fluorescence experiments so as to facilitate the analysis of experimental data. PMID:8471729

  19. Prediction of absorption coefficients by pulsed laser induced photoacoustic measurements.

    PubMed

    Priya, Mallika; Satish Rao, B S; Ray, Satadru; Mahato, K K

    2014-06-05

    In the current study, a pulsed laser induced photoacoustic spectroscopy setup was designed and developed, aiming its application in clinical diagnostics. The setup was optimized with carbon black samples in water and with various tryptophan concentrations at 281nm excitations. The sensitivity of the setup was estimated by determining minimum detectable concentration of tryptophan in water at the same excitation, and was found to be 0.035mM. The photoacoustic experiments were also performed with various tryptophan concentrations at 281nm excitation for predicting optical absorption coefficients in them and for comparing the outcomes with the spectrophotometrically-determined absorption coefficients for the same samples. Absorption coefficients for a few serum samples, obtained from some healthy female volunteers, were also determined through photoacoustic and spectrophotometric measurements at the same excitations, which showed good agreement between them, indicating its clinical implications.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    Sahoo, Niranjan; Kumar, Rakesh

    2016-09-01

    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 %.

  2. Measuring Neutron Star Radii via Pulse Profile Modeling with NICER

    NASA Astrophysics Data System (ADS)

    Özel, Feryal; Psaltis, Dimitrios; Arzoumanian, Zaven; Morsink, Sharon; Bauböck, Michi

    2016-11-01

    The Neutron-star Interior Composition Explorer is an X-ray astrophysics payload that will be placed on the International Space Station. Its primary science goal is to measure with high accuracy the pulse profiles that arise from the non-uniform thermal surface emission of rotation-powered pulsars. Modeling general relativistic effects on the profiles will lead to measuring the radii of these neutron stars and to constraining their equation of state. Achieving this goal will depend, among other things, on accurate knowledge of the source, sky, and instrument backgrounds. We use here simple analytic estimates to quantify the level at which these backgrounds need to be known in order for the upcoming measurements to provide significant constraints on the properties of neutron stars. We show that, even in the minimal-information scenario, knowledge of the background at a few percent level for a background-to-source countrate ratio of 0.2 allows for a measurement of the neutron star compactness to better than 10% uncertainty for most of the parameter space. These constraints improve further when more realistic assumptions are made about the neutron star emission and spin, and when additional information about the source itself, such as its mass or distance, are incorporated.

  3. A General Purpose Q-Measuring Circuit Using Pulse Ring-Down.

    PubMed

    Quine, Richard W; Mitchell, Deborah G; Eaton, Gareth R

    2011-02-01

    A general purpose pulsed microwave circuit was developed for the purpose of measuring resonator Q by the pulse ring-down method in EPR spectrometers without pulse capability. The circuit was installed and tested in a Bruker X-band EPR bridge. This method and circuit could be adapted for use in a variety of spectrometers operating at various microwave frequencies.

  4. 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.

  5. Influence of aerosols on propagation of intensive pulses of a CO2-laser of microsecond duration in the near-surface atmosphere

    NASA Astrophysics Data System (ADS)

    Chistyakova, Liliya K.

    2002-02-01

    The results of the field experiments on propagation of intensive pulses of CO2- laser on the near surface atmospheric path have been discussed. The data are given on non-linear aerosol scattering, luminescence of aerosol particles and plasma in a light beam and their influence on the beam characteristics. The field experiments have shown that the optical breakdown and thermal luminescence of aerosol particles are possible under the effect of the CO2-laser pulses. The heating aerosol particle up to the temperature, when the developed evaporation is occurred, yet does not guarantee the appearance of the plasma initiation core, which is capable to evolve in the regime of light detonation. At the thermal mechanism of development of equilibrium plasma the luminescence intensity maxims in different ranges of the spectrum coincide in time and occur after a maximum of an effecting pulse. The intensity fluctuations in the beam at the beginning of the pulse do not result in the luminescence fluctuations, which arise only to the end of a pulse. It testifies to an essential role of energy of a line-transmitted spectrum of the luminescence core, i.e., not too high temperatures (T approximately 103 K) and the pressures achievable at absorption by particles of energy of the initiating pulse. The thermal blooming of luminescent particles are new radiation sources with dimensions, exceeding the size of aerosol particles by two orders that results in the 104 increase of the scattering radiation. The essential part of the laser energy scattered on these blooming, as well as on shock waves, will be concentrated in a narrow angle in a forward direction, as their dielectric constant is less, than it is for aerosol particles. The measured aerosol scattering coefficient is higher than the calculated linear coefficient by one order. It is shown, that the overcondensation at explosive destruction of a water aerosol by fragments can also result in the considerable increase of scattering for

  6. 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.

  7. Autocorrelation measurement of femtosecond laser pulses based on two-photon absorption in GaP photodiode

    NASA Astrophysics Data System (ADS)

    Chong, E. Z.; Watson, T. F.; Festy, F.

    2014-08-01

    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.

  8. 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.

  9. 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.

  10. Simultaneous PSP and TSP measurements of transient flow in a long-duration hypersonic tunnel

    NASA Astrophysics Data System (ADS)

    Peng, Di; Jiao, Lingrui; Sun, Zhijun; Gu, Yunsong; Liu, Yingzheng

    2016-12-01

    The current work presents simultaneous measurements of transient flow using fast-responding pressure- and temperature-sensitive paints in a long-duration hypersonic tunnel; the pressure, temperature and heat flux fields were obtained on a standard model (HB-2) at Ma = 5. Fast PSP and TSP were applied symmetrically on the model with low thermal conductivity. Both coatings were illuminated by a UV-LED, and unsteady pressure and temperature data were recorded at 500 Hz using a high-speed camera. Time-dependent temperature correction was applied on the PSP data based on the TSP results, while the heat flux was calculated from the time-resolved temperature fields using a 1D semi-finite heat conduction model. The temperature-induced errors in PSP data were effectively removed by the current compensation method. The pressure and heat flux results showed good agreement with the reference data from previous studies. The key events throughout the hypersonic tunnel run were captured by the unsteady PSP/TSP data, including the tunnel start-up, the flow build-up, the steady flow period and the tunnel shutdown. The differences caused by the change of attack angle were also clearly recognized. The current PSP/TSP system has shown great potential for unsteady flow diagnostics in hypersonic flows.

  11. Optical properties of tissue measured using terahertz-pulsed imaging

    NASA Astrophysics Data System (ADS)

    Berry, Elizabeth; Fitzgerald, Anthony J.; Zinov'ev, Nickolay N.; Walker, Gillian C.; Homer-Vanniasinkam, Shervanthi; Sudworth, Caroline D.; Miles, Robert E.; Chamberlain, J. Martyn; Smith, Michael A.

    2003-06-01

    The first demonstrations of terahertz imaging in biomedicine were made several years ago, but few data are available on the optical properties of human tissue at terahertz frequencies. A catalogue of these properties has been established to estimate variability and determine the practicality of proposed medical applications in terms of penetration depth, image contrast and reflection at boundaries. A pulsed terahertz imaging system with a useful bandwidth 0.5-2.5 THz was used. Local ethical committee approval was obtained. Transmission measurements were made through tissue slices of thickness 0.08 to 1 mm, including tooth enamel and dentine, cortical bone, skin, adipose tissue and striated muscle. The mean and standard deviation for refractive index and linear attenuation coefficient, both broadband and as a function of frequency, were calculated. The measurements were used in simple models of the transmission, reflection and propagation of terahertz radiation in potential medical applications. Refractive indices ranged from 1.5 +/- 0.5 for adipose tissue to 3.06 +/- 0.09 for tooth enamel. Significant differences (P < 0.05) were found between the broadband refractive indices of a number of tissues. Terahertz radiation is strongly absorbed in tissue so reflection imaging, which has lower penetration requirements than transmission, shows promise for dental or dermatological applications.

  12. Measurement and control of the frequency chirp rate of high-order harmonic pulses

    SciTech Connect

    Mauritsson, J.; Johnsson, P.; Lopez-Martens, R.; Varju, K.; L'Huillier, A.; Kornelis, W.; Biegert, J.; Keller, U.; Gaarde, M.B.; Schafer, K.J.

    2004-08-01

    We measure the chirp rate of harmonics 13 to 23 in argon by cross correlation with a 12 femtosecond probe pulse. Under low ionization conditions, we directly measure the negative chirp due to the atomic dipole phase, and show that an additional chirp on the pump pulse is transferred to the qth harmonic as q times the fundamental chirp. Our results are in accord with simulations using the experimentally measured 815 nm pump and probe pulses. The ability to measure and manipulate the harmonic chirp rate is essential for the characterization and optimization of attosecond pulse trains.

  13. Measuring pulse rate variability using long-range, non-contact imaging photoplethysmography.

    PubMed

    Blackford, Ethan B; Piasecki, Alyssa M; Estepp, Justin R

    2016-08-01

    Camera-based measurement of the blood volume pulse via non-contact, imaging photoplethysmography is a very popular approach for measuring pulse rate using a remote imaging sensor. Comparatively less attention has been paid to the usefulness of the method for measuring features of pulse rate variability, and even less focus has been put on the accuracy of any cardiac activity feature that can be achieved at long imager-to-subject distances. In this study, video was recorded from 19 participants, while at rest, at a distance of 25 meters from the imaging sensor. A digital camera was used to record video while cardiovascular measures of both electrical and optical physiological ground truth were recorded. Pulse rate data obtained from the imager using a common blind source separation and periodogram approach were compared to physiological ground truth signals. The quality of the recovered blood volume pulse morphology was sufficient to calculate time-domain measures of pulse rate using inter-pulse interval (IPI) time series. Following this, several features of pulse rate variability were calculated from the IPI time series and compared to those calculated from the corresponding physiological ground truth signals. Use of the time-domain data as compared to the periodogram approach to measure pulse rate reduced the error in the estimate from 1.6 to 0.2 beats per minute. Correlation analysis (r2) between the camera-based measures of pulse rate variability and ECG-derived heart rate variability ranged from 0.779 to 0.973; these results are of comparable outcome to those obtained at imager-to-subject distances of no more than 3 meters. This study demonstrates that pulse rates of less than one beat-per-minute error can be obtained when the recovered blood volume pulse morphology is of adequate quality to resolve systolic onsets for individual cardiac cycles. Further, this approach can yield data of very promising quality for estimating measures of pulse rate variability.

  14. 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.

  15. Onset-Duration Matching of Acoustic Stimuli Revisited: Conventional Arithmetic vs. Proposed Geometric Measures of Accuracy and Precision

    PubMed Central

    Friedrich, Björn; Heil, Peter

    2017-01-01

    Onsets of acoustic stimuli are salient transients and are relevant in humans for the perception of music and speech. Previous studies of onset-duration discrimination and matching focused on whether onsets are perceived categorically. In this study, we address two issues. First, we revisit onset-duration matching and measure, for 79 conditions, how accurately and precisely human listeners can adjust the onset duration of a comparison stimulus to subjectively match that of a standard stimulus. Second, we explore measures for quantifying performance in this and other matching tasks. The conventional measures of accuracy and precision are defined by arithmetic descriptive statistics and the Euclidean distance function on the real numbers. We propose novel measures based on geometric descriptive statistics and the log-ratio distance function, the Euclidean distance function on the positive-real numbers. Only these properly account for the fact that the magnitude of onset durations, like the magnitudes of most physical quantities, can attain only positive real values. The conventional (arithmetic) measures possess a convexity bias that yields errors that grow with the width of the distribution of matches. This convexity bias leads to misrepresentations of the constant error and could even imply the existence of perceptual illusions where none exist. This is not so for the proposed (geometric) measures. We collected up to 68 matches from a given listener for each condition (about 34,000 matches in total) and examined inter-listener variability and the effects of onset duration, plateau duration, sound level, carrier, and restriction of the range of adjustable comparison stimuli on measures of accuracy and precision. Results obtained with the conventional measures generally agree with those reported in the literature. The variance across listeners is highly heterogeneous for the conventional measures but is homogeneous for the proposed measures. Furthermore, the proposed

  16. 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.

  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. 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.

  19. Leaf wetness duration measurement: comparison of cylindrical and flat plate sensors under different field conditions.

    PubMed

    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 degrees 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

  20. How Mechanical Ventilation Measurement, Cutoff and Duration Affect Rapid Shallow Breathing Index Accuracy: A Randomized Trial

    PubMed Central

    Goncalves, Elaine Cristina; Lago, Alessandra Fabiane; Silva, Elaine Caetano; de Almeida, Marcelo Barros; Basile-Filho, Anibal; Gastaldi, Ada Clarice

    2017-01-01

    Background Decreased accuracy of the rapid shallow breathing index (RSBI) can stem from 1) the method used to obtain this index, 2) duration of mechanical ventilation (MV), and 3) the established cutoff point. The objective was to evaluate the values of RSBI determined by three different methods, using distinct MV times and cutoff points. Methods This prospective study included 40 subjects. Before extubation, three different methods were employed to measure RSBI: pressure support ventilator (PSV) (PSV = 5 - 8 cm H2O; positive end-expiratory pressure (PEEP) = 5 cm H2O) (RSBI_MIN), automatic tube compensation (ATC) (PSV = 0, PEEP = 5 cm H2O, and 100% tube compensation) (RSBI_ATC), and disconnected MV (RSBI_SP). The results were analyzed according to the MV period (less than or over 72 h) and to the outcome of extubation (< 72 h, successful and failed; > 72 h successful and failed). The accuracy of each method was determined at different cutoff points (105, 78, and 50 cycles/min/L). Results The RSBI_MIN, RSBI_ATC, and RSBI_SP values in the group < 72 h were 38 ± 18, 45 ± 26 and 55 ± 22; in the group > 72 h, RSBI_SP value was higher than those of RSBI_ATC and RSBI_MIN (78 ± 29, 51 ± 19 and 39 ± 14) (P < 0.001). For patients with MV > 72 h who failed in removing MV, the RSBI_SP was higher (93 ± 28, 58 ± 18 and 41 ± 10) (P < 0.000), with greater accuracy at cutoff of 78. Conclusion RSBI_SP associated with cutoff point < 78 cycles/min/L seems to be the best strategy to identify failed extubation in subjects with MV for over 72 h. PMID:28270888

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Development of a pulsed 9.5 micron lidar for regional scale O3 measurement

    NASA Technical Reports Server (NTRS)

    Stewart, R. W.

    1980-01-01

    A pulsed infrared lidar system designed for application to the remote sensing of atmospheric trace gases from an airborne platform is described. The system is also capable of measuring the infrared backscatter characteristics of the ocean surface, terrain, cloud, and aerosol targets. The lidar employed is based on dual wavelength pulse energy measurements in the 9-11 micrometer wavelength region.

  7. [Evaluation of circulatory state using pulse oximeter: 2. Measurement of total hemoglobin employing pulse CO-oximetry (Masimo Radical-7)].

    PubMed

    Miyoshi, Hiroshi; Sumikawa, Koji

    2009-07-01

    Development of pulse oximeter technology has made it possible to measure total hemoglobin noninvasively. The use of Radical-7 would improve patient care in emergency medicine and chronic internal medicine as well as perioperative medicine, and could reduce the burden of the patient.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. Measurement of Spatial and Temporal Profiles of Electron Plasma Oscillation Excited by Ultrashort Laser Pulse

    NASA Astrophysics Data System (ADS)

    Takahashi, Eiji; Katsura, Keisuke; Miura, Eisuke; Yugami, Noboru; Nishida, Yasushi; Honda, Hiroshi; Kondo, Kiminori

    1999-11-01

    Large amplitude electron plasma waves (EPW), which are produced by ultrashort laser pulses, are of great interest for particle acceleration or photon acceleration. In this study, we present the temporally and spatially resolved measurements of the electron density perturbation produced by the laser wakefield (LWF) process. 0.6 TW Ti:sapphire laser pulse ionized the helium gas of ~ 1 Torr near the focus and excited the electron density perturbation. We observed this electron density perturbation by the frequency-domain interferometry technique. The probe pulse was the second harmonic of the partially separated pulse from the main pump pulse. The probe pulse was sent into the Michelson interferometer and make two colinear pulses. These two probe pulses go through the EPW, and are affected by EPW of which phase velocity is almost equal to the light velocity. Each pulse obtains a phase shift depending on the phase of EPW. These two pulses interfer each other in the spectometer. Spatialy resolved relative phase shift can be obtained from the interferogram. With varying the relative delay between the two probe pulses, 2 THz periodic change of the relative phase shift was observed. It was caused by 2THz electron density oscillation in LWF.

  13. 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.

  14. Effects of pulse phase duration and location of stimulation within the inferior colliculus on auditory cortical evoked potentials in a guinea pig model.

    PubMed

    Neuheiser, Anke; Lenarz, Minoo; Reuter, Guenter; Calixto, Roger; Nolte, Ingo; Lenarz, Thomas; Lim, Hubert H

    2010-12-01

    The auditory midbrain implant (AMI), which consists of a single shank array designed for stimulation within the central nucleus of the inferior colliculus (ICC), has been developed for deaf patients who cannot benefit from a cochlear implant. Currently, performance levels in clinical trials for the AMI are far from those achieved by the cochlear implant and vary dramatically across patients, in part due to stimulation location effects. As an initial step towards improving the AMI, we investigated how stimulation of different regions along the isofrequency domain of the ICC as well as varying pulse phase durations and levels affected auditory cortical activity in anesthetized guinea pigs. This study was motivated by the need to determine in which region to implant the single shank array within a three-dimensional ICC structure and what stimulus parameters to use in patients. Our findings indicate that complex and unfavorable cortical activation properties are elicited by stimulation of caudal-dorsal ICC regions with the AMI array. Our results also confirm the existence of different functional regions along the isofrequency domain of the ICC (i.e., a caudal-dorsal and a rostral-ventral region), which has been traditionally unclassified. Based on our study as well as previous animal and human AMI findings, we may need to deliver more complex stimuli than currently used in the AMI patients to effectively activate the caudal ICC or ensure that the single shank AMI is only implanted into a rostral-ventral ICC region in future patients.

  15. Objectively measured physical activity, sedentary time and sleep duration: independent and combined associations with adiposity in canadian children

    PubMed Central

    Chaput, J-P; Leduc, G; Boyer, C; Bélanger, P; LeBlanc, A G; Borghese, M M; Tremblay, M S

    2014-01-01

    Objective: To examine independent and combined associations among objectively measured movement/non-movement behaviors (moderate-to-vigorous-intensity physical activity (MVPA), total sedentary time and sleep duration) and adiposity indicators in a sample of Canadian children. Methods: A cross-sectional study was conducted on 507 children aged 9–11 years from Ottawa, Canada. Movement/non-movement behaviors were assessed using an Actigraph GT3X+ accelerometer over 7 days (24-h protocol). Outcomes included percentage body fat (bioelectrical impedance) and waist-to-height ratio. Results: After adjustment for age, sex, ethnicity, maturity offset, fast food consumption, annual household income and highest level of parental education, MVPA was inversely and sedentary time positively associated with adiposity indicators, whereas sleep duration was not. However, only MVPA remained significantly associated with adiposity indicators after additional adjustment for the other movement/non-movement behaviors. Combined associations using tertiles of the three movement/non-movement behaviors showed that higher levels of MVPA were associated with lower adiposity indicators, irrespective of total sedentary time and sleep duration. Conclusions: Higher levels of MVPA were associated with lower adiposity in this sample of children regardless of sedentary time and sleep duration. Although correlational in nature, these findings suggest that future efforts of obesity reduction should focus more on increasing MVPA than on reducing sedentary time or increasing sleep duration to maximize the effectiveness of interventions. PMID:24911633

  16. Arterial pulse shape measurement using self-mixing effect in a diode laser

    SciTech Connect

    Hast, J; Myllylae, Risto; Sorvoja, H; Miettinen, J

    2002-11-30

    The self-mixing effect in a diode laser and the Doppler technique are used for quantitative measurements of the cardiovascular pulses from radial arteries of human individuals. 738 cardiovascular pulses from 10 healthy volunteers were studied. The Doppler spectrograms reconstructed from the Doppler signal, which is measured from the radial displacement of the radial artery, are compared to the first derivative of the blood pressure signals measured from the middle finger by the Penaz technique. The mean correlation coefficient between the Doppler spectrograms and the first derivative of the blood pressure signals was 0.84, with a standard deviation of 0.05. Pulses with the correlation coefficient less than 0.7 were neglected in the study. Percentage of successfully detected pulses was 95.7%. It is shown that cardiovascular pulse shape from the radial artery can be measured noninvasively by using the self-mixing interferometry. (laser biology and medicine)

  17. 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.

  18. Direct measurement of group delay dispersion in metamagnetics for ultrafast pulse shaping.

    PubMed

    Brown, Dean P; Walker, Mark A; Urbas, Augustine M; Kildishev, Alexander V; Xiao, Shumin; Drachev, Vladimir P

    2012-10-08

    In this paper, we explore the use of magnetic resonant metamaterials, so called metamagnetics, as dispersive elements for optical pulse shaping. We measure both positive and negative group delay dispersion (GDD) values in a metamagnetic material using the multiphoton interference phase scan (MIIPS) technique and show pulse temporal profiles numerically. The results are compared with finite element models. These GDD properties of metamagnetics, along with previously shown tunability and loss control with gain media, enable their use in ultrashort pulse optical applications.

  19. Pulsed eldor measurement of nitrogen T1 in spin labels

    NASA Astrophysics Data System (ADS)

    Hyde, James S.; Froncisz, W.; Mottley, C.

    1984-10-01

    A 180° pulse is delivered to one hyperfine line of a nitroxide spin label, and the arrival and disappearance of saturation at another hyperfine line is monitored with a second microwave field. Electron and nitrogen nuclear relaxation times are found to be in poor agreement ,vith the electron-nuclear dipolar (END) mechanism.

  20. 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.

  1. 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.

  2. Full-field dynamic displacement and strain measurement using pulsed and high-speed 3D image correlation photogrammetry

    NASA Astrophysics Data System (ADS)

    Schmidt, Timothy; Tyson, John; Galanulis, Konstantin

    2004-02-01

    3D image correlation is a robust method for measuring full-field displacements and strains using a calibrated pair of video cameras. Underlying principles and benefits are reviewed, and the method is compared to both 3D ESPI and 2D image correlation. Several applications combining image correlation photogrammetry with stroboscopic illumination and/or high-speed video cameras are presented. Operational strains in ionic polymeric muscle samples and electro-restrictive actuators are determined. The use of short-duration white light pulses to study automobile tires on road wheels at speeds up to 150 miles per hour is demonstrated. Initial work measuring strains on an 18" flywheel in a spin pit at up to 35,000 rpm is described. A notched rubber dogbone sample is pulled to failure at 125% strain in 38 milliseconds, and hundreds of full-field strain maps are captured. This paper includes discussion of sample preparation methods and special lighting systems, including pulsed arc lamps and pulsed lasers. A matrix of capability using available high speed cameras is included.

  3. Evidence of secondary electron emission during PIII pulses as measured by calorimetric probe

    NASA Astrophysics Data System (ADS)

    Haase, Fabian; Manova, Darina; Mändl, Stephan; Kersten, Holger

    2016-09-01

    Secondary electrons are an ubiquitous nuisance during plasma immersion ion implantation (PIII) necessitating excessive current supplies and shielding for X-rays generated by them. However, additional effects - especially at low pulse voltages - can include interactions with the plasma and transient increases in the plasma density. Here, it is shown that the transient thermal flux associated with secondary electrons emitted from the pulsed substrate can be directly measured using a passive calorimetric probe mounted near the chamber wall away from the pulsed substrate holder. A small increase of a directed energy flux from the substrate towards the probe is consistently observed on top of the isotropic flux from the plasma surrounding the probe, scaling with pulse frequency, pulse voltage, pulse length - as well as depending on gas and substrate material. A strong correlation between voltage and substrate-probe distance is observed, which should allow further investigation of low energy electrons with the plasma itself.

  4. Computer-controlled pulsed magnetic field gradient NMR system for electrophoretic mobility measurements

    NASA Astrophysics Data System (ADS)

    Saarinen, Timothy R.; Woodward, W. Stephen

    1988-05-01

    A computer-controlled pulsed magnetic field gradient NMR (PFGNMR) system for making electrophoretic mobility and diffusion measurements is described. Emphasis is placed on the design and capabilities of the gradient and electrophoretic pulse generators. Various pulse sequences can be applied by the programmable gradient generator that can produce 0- to 10-A current pulses for 0 to 13 ms and continuous currents from 0 to 50 mA. The pulse areas are reproducible to within approximately 1 ppm. A pair of opposed Helmholtz coils in the probe create linear magnetic field gradients during the current pulses. Electric fields are applied across a U-tube electrophoretic cell by a 550-V constant current generator.

  5. 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.

  6. Method to precisely measure the phase of few-cycle laser pulses.

    PubMed

    Liao, Qing; Lu, Peixiang; Lan, Pengfei; Yang, Zhenyu; Li, Yunhua

    2008-04-28

    A new method of accurately measuring the carrier-envelope phase (CEP) of few-cycle pulses is presented. The high-energy photo-electron spectrum by a few-cycle pulse is dominated by photoelectrons bursting in very few short time intervals near the maximum of the pulse envelope. For high laser intensities, the positions of interference fringes in the high-energy cutoff region are very sensitive to the CEP, which can be used to measure and stabilize the CEP precisely. The measurement precision of the CEP strongly depends on the laser intensity for the fastest photoelectrons.

  7. Measurements of acoustic environments for urban soundscapes: choice of homogeneous periods, optimization of durations, and selection of indicators.

    PubMed

    Brocolini, Laurent; Lavandier, Catherine; Quoy, Mathias; Ribeiro, Carlos

    2013-07-01

    In order to minimize the duration of acoustic measurements and to characterize homogeneous areas from a temporal point of view, a series of six location measurements was carried out continuously during three months in Paris. Around fifty thousand samples of 5-min, 10-min, 15-min, 20-min, 30-min, and 1-h duration measurements were extracted for each location. Each sample is characterized by eleven energy indicators and ten event descriptors. In this paper, analysis of a crossroad location is detailed. Through hierarchical ascendant classification and artificial neural networks classification, it is shown that four homogeneous periods can be detected: two during the night, one during the day, and one transition corresponding either to the awakening or to the moment when the city falls asleep. 10-min measurements are necessary to discriminate these time periods at the crossroad location. At the end of the paper, a comparison with the other locations shows that minimum duration states in between 10 and 20 min. The homogeneous periods are connected to the human activities and depend on the location. Energy indicators such as LAeq, LA10, or LA90 and event indicators are necessary to characterize the different clusters.

  8. 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.

  9. Quantification of adipose volume reduction with a prospective study analyzing the application of external radiofrequency energy and high voltage ultrashort pulse duration electrical fields.

    PubMed

    Duncan, Diane Irvine; Kim, Theresa H M; Temaat, Robbin

    2016-10-01

    To date, there have been no objective measurements of subcutaneous volume loss following treatments with a noninvasive radiofrequency (RF)-based device. Twenty female patients were treated with a suction-coupled bipolar RF device using external RF energy combined with pulsed electromagnetic RF energy for subcutaneous fat reduction. Parameters followed included weight, Vectra measurements of abdominal circumference and torso volume, and high-definition ultrasound measurements of fat thickness. Measurements were taken before treatment and three times following treatment. Analysis of the measured parameters showed that mean circumference reduction of 2.30 cm was noted at three months post-treatment. Independent volumetric analysis showed a mean subcutaneous volume reduction of 428 cc three months following RF treatment. High-resolution ultrasound fat thickness was reduced by a mean of 39.6% three months following the final BodyFX treatment. Independent and paired-sample t-tests showed a p value of < 0.05. Repeated measures of analysis of covariance (ANCOVA) adjusted for differences in age, as well as height and weight (proxy for body mass index) to minimize individual differences and control for extraneous variables that may affect the pre- and post-treatment results were analyzed. No confounding variables were found. All analyses were conducted using IBM SPSS 21.0.

  10. 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.

  11. 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

  12. 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.

  13. Development of a Tonometric Sensor with a Decoupled Circular Array for Precisely Measuring Radial Artery Pulse.

    PubMed

    Jun, Min-Ho; Kim, Young-Min; Bae, Jang-Han; Jung, Chang Jin; Cho, Jung-Hee; Jeon, Young Ju

    2016-05-26

    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.

  14. High precision laser ranging by time-of-flight measurement of femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Lee, Joohyung; Lee, Keunwoo; Lee, Sanghyun; Kim, Seung-Woo; Kim, Young-Jin

    2012-06-01

    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 the production of a balanced optical cross-correlation signal between two overlapping 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 of 1.5, 60 and 700 m. This method is found well suited for future space missions based on formation-flying satellites as well as large-scale industrial applications for land surveying, aircraft manufacturing and shipbuilding.

  15. 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.

  16. 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.

  17. [A calibrated method for blood pressure measurement based on volume pulse wave].

    PubMed

    Youde, Ding; Qinkai, Deng; Feixue, Liang; Jinseng, Guo

    2010-01-01

    Physiology parameters measurement based on volume pulse wave is suitable for the monitoring blood pressure continuously. This paper described that the systolic blood pressure (SBP) and diastolic blood pressure (DBP) can be calibrated by measuring the pulse propagation time, just on one point of finger tip. The volume pulse wave was acquired by lighting the red and infrared LED alternately, and after signal processing, an accelerated pulse wave was obtained. Then by measuring the pulse wave propagation time between the progressive wave and reflected wave, we can find the relationship of the time and the blood pressure, and establish the related systolic blood pressure measurement equation. At the same time, based on the relationship between alternating current and direct current components in the volume pulse waveforms and through regression analysising, the relevant diastolic blood pressure measurement equation can be established. 33 clinical experimentation cases have been worked by dividing them into two groups: training group (18 cases) and control group (15 cases), by comparing with the measuring results of the OMRON electronic sphygmomanometer. The results indicated that the two methods had good coherence. The measurement described is simple and reliable, and may be served as a new method for noninvasively and continuously measurement of blood pressure.

  18. 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

  19. 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

  20. 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.

  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. 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.

  5. 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.

  6. Dew Duration and Amount on Corn Leaves as Determined From SMEX05 Measurements and Reanalysis Using the ALEX Model

    NASA Astrophysics Data System (ADS)

    Kabela, E. D.; Hornbuckle, B. K.; Cosh, M. H.; Anderson, M. C.; Gleason, M. L.

    2006-05-01

    Dew plagues crop producers in many facets of agriculture. Many studies have been done on the effects of dew in terms of pest formation and diseases on crops. Although the formation of dew is significant on a micro- scale, satellite projects such as SMOS aim to measure soil moisture on a meso or synoptic scale. The presence of dew has been found to decrease soil brightness temperature, which in turn effects soil moisture readings. The purpose of the dew collection portion of the Soil Moisture Experiment in 2005 (SMEX05) was to manually measure dew so that the effect could be studied on measurements made by remotely sensed soil moisture readings. The purpose of this paper is to determine if manual dew measurements obtained during SMEX05 are accurately modeled by the atmosphere-land exchange model, ALEX. Dew measurements were taken during SMEX05 from June 16 to July 3, 2005 in corn, soybean, and alfalfa fields south of Ames, Iowa. Collection usually began at approximately 645 CDT and commenced at approximately 900 CDT each morning. My hypothesis for this paper is that dew amount and duration collected from SMEX05 are predicted accurately by the atmosphere-land exchange (ALEX) model. Accuracy for dew amount is definded as an amount within 0.05 to 0.1 mm of manual measurements. Accuracy for dew duration is defined as 0.5 hours within automated observations from leaf wetness sensors deployed in various fields within the Walnut Creek watershed. It was found that dew amount is accurate for light, moderate, and heavy dew events, while dew duration is predicted within 0.5 to 1.0 hours.

  7. Pulse-to-pulse alignment based on interference fringes and the second-order temporal coherence function of optical frequency combs for distance measurement.

    PubMed

    Zhu, Jigui; Cui, Pengfei; Guo, Yin; Yang, Linghui; Lin, Jiarui

    2015-05-18

    A pulse-to-pulse alignment method based on interference fringes and the second-order temporal coherence function of optical frequency combs is proposed for absolute distance measurement. The second-order temporal coherence function of the pulse train emitted from optical frequency combs is studied. A numerical model of the function is developed with an assumption of Gaussian pulse and has good agreement with experimental measurements taken by an ordinary Michelson interferometer. The experimental results show an improvement of standard deviation of peak finding results from 27.3 nm to 8.5 nm by the method in ordinary laboratory conditions. The absolute distance measurement with the pulse-to-pulse alignment method is also proposed and experimentally proved.

  8. 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.

  9. Single Molecule Measurements of F1-ATPase Reveal an Interdependence between the Power Stroke and the Dwell Duration

    PubMed Central

    Spetzler, David; Ishmukhametov, Robert; Hornung, Tassilo; Day, Lixia Jin; Martin, James; Frasch, Wayne D.

    2009-01-01

    Increases in the power stroke and dwell durations of single molecules of E. coli F1-ATPase were measured in response to viscous loads applied to the motor and inhibition of ATP hydrolysis. The load was varied using different sizes of gold nanorods attached to the rotating γ subunit and/or by increasing the viscosity of the medium using PEG-400, a noncompetitive inhibitor of ATPase activity. Conditions that increase the duration of the power stroke were found to cause 20-fold increases in the length of the dwell. These results suggest that the order of hydrolysis, product release, and substrate binding may change as the result of external load on the motor or inhibition of hydrolysis. PMID:19610671

  10. Improving quantum gate fidelities by using a qubit to measure microwave pulse distortions.

    PubMed

    Gustavsson, Simon; Zwier, Olger; Bylander, Jonas; Yan, Fei; Yoshihara, Fumiki; Nakamura, Yasunobu; Orlando, Terry P; Oliver, William D

    2013-01-25

    We present a new method for determining pulse imperfections and improving the single-gate fidelity in a superconducting qubit. By applying consecutive positive and negative π pulses, we amplify the qubit evolution due to microwave pulse distortions, which causes the qubit state to rotate around an axis perpendicular to the intended rotation axis. Measuring these rotations as a function of pulse period allows us to reconstruct the shape of the microwave pulse arriving at the sample. Using the extracted response to predistort the input signal, we are able to reduce the average error per gate by 37%, which enables us to reach an average single-qubit gate fidelity higher than 0.998.

  11. 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).

  12. Pulse Oximeter Derived Blood Pressure Measurement in Patients With a Continuous Flow Left Ventricular Assist Device.

    PubMed

    Hellman, Yaron; Malik, Adnan S; Lane, Kathleen A; Shen, Changyu; Wang, I-Wen; Wozniak, Thomas C; Hashmi, Zubair A; Munson, Sarah D; Pickrell, Jeanette; Caccamo, Marco A; Gradus-Pizlo, Irmina; Hadi, Azam

    2016-10-26

    Currently, blood pressure (BP) measurement is obtained noninvasively in patients with continuous flow left ventricular assist device (LVAD) by placing a Doppler probe over the brachial or radial artery with inflation and deflation of a manual BP cuff. We hypothesized that replacing the Doppler probe with a finger-based pulse oximeter can yield BP measurements similar to the Doppler derived mean arterial pressure (MAP). We conducted a prospective study consisting of patients with contemporary continuous flow LVADs. In a small pilot phase I inpatient study, we compared direct arterial line measurements with an automated blood pressure (ABP) cuff, Doppler and pulse oximeter derived MAP. Our main phase II study included LVAD outpatients with a comparison between Doppler, ABP, and pulse oximeter derived MAP. A total of five phase I and 36 phase II patients were recruited during February-June 2014. In phase I, the average MAP measured by pulse oximeter was closer to arterial line MAP rather than Doppler (P = 0.06) or ABP (P < 0.01). In phase II, pulse oximeter MAP (96.6 mm Hg) was significantly closer to Doppler MAP (96.5 mm Hg) when compared to ABP (82.1 mm Hg) (P = 0.0001). Pulse oximeter derived blood pressure measurement may be as reliable as Doppler in patients with continuous flow LVADs.

  13. Development of a 2-micron Pulsed Direct Detection IPDA Lidar for CO2 Measurement

    NASA Astrophysics Data System (ADS)

    Yu, J.; Petros, M.; Singh, U. N.

    2013-12-01

    NASA Langley is developing a 2-micron pulsed Integrated Path Differential Absorption (IPDA) lidar for atmospheric CO2 measurements. 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. The objective of this development is to integrate an existing high energy double-pulsed 2-micron laser transmitter with a direct detection receiver and telescope to enable a first proof of principle demonstration of airborne direct detection CO2 measurements at 2-micron wavelength. It is expected to provide high-precision measurement capability by unambiguously eliminating contamination from aerosols and clouds that can bias the IPDA measurement. The system is scheduled to fly on NASA UC12 or B200 research aircrafts before the end of 2013. 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; and lidar signal to noise ratio estimation.

  14. 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.

  15. Measurement of duration and signal-to-noise ratio of astronomical transients using a Spectral Kurtosis spectrometer

    NASA Astrophysics Data System (ADS)

    Nita, Gelu M.; Gary, Dale E.

    2016-08-01

    Following our prior theoretical and instrumental work addressing the problem of automatic real-time radio frequency interference (RFI) detection and excision from astronomical signals, the wideband Spectral Kurtosis (SK) spectrometer design we proposed is currently being considered as an alternative to the traditional spectrometers when building the new generation of radio instruments. The unique characteristic of an SK spectrometer is that it accumulates both power and power-squared, which are then used to compute an SK statistical estimator proven to be very effective in detecting and excising certain types of RFI signals. In this paper we introduce a novel measurement technique that exploits the power and power square statistics of an SK spectrometer to determine durations and signal-to-noise ratios of transient signals, whether they are RFI or natural signals, even when they are below the time resolution of the instrument. We demonstrate this novel experimental technique by analyzing a segment of data recorded by the Expanded Owens Valley Solar Array Subsystem Testbed (EST) during a solar radio burst in which microwave spike bursts occurred with durations shorter than the 20 ms time resolution of the instrument. The duration of one well-observed spike is quantitatively shown to be within a few percent of 8 ms despite the 20 ms resolution of the data.

  16. 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.

  17. Time-of-flight measurement with femtosecond pulses for high precision ranging lidar

    NASA Astrophysics Data System (ADS)

    Lee, J.; Kim, Y.-J.; Lee, K.; Lee, S.; Kim, S.-W.

    2010-10-01

    The time-of-flight of light pulses has long been used as a direct measure of distance, but the state-of-the-art measurement precision using conventional light pulses or microwaves reaches only several hundreds of micromeres. This is due to the bandwidth limit of the photodetectors available today, which is in the picosecond range at best. Here, we improve the time-of-flight precision to the nanometer regime by timing femtosecond pulses through phase-locking control of the pulse repetition rate using the optical cross-correlation technique that exploits a second-harmonic birefringence crystal and a balance photodetector. The enhanced capability is maintained at long range without periodic ambiguity, being well suited to terrestrial lidar applications such as geodetic surveying, range finders and absolute altimeters. This method could also be applied to future space missions of formation-flying satellites for synthetic aperture imaging and remote experiments related to the general relativity theory.

  18. 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.

  19. Pulse compression in plasma: Generation of femtosecond pulses without CPA

    SciTech Connect

    G. Shvets; N. J. Fisch; A. Pukhov; J. Meyer-ter-Vehn

    2000-07-20

    Laser pulses can be efficiently compressed to femtosecond duration when a smaller-frequency short pulse collides with high frequency long pulse in rare plasma, absorbing most of its energy. The mechanism of short pulse amplification is nonlinear superradiance.

  20. 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.

  1. Measurement and Generation of Ultra-High Power Fiber Laser Pulses by Coherent Combination

    DTIC Science & Technology

    2010-06-01

    through a Michelson interferometer and generated a double pulse as shown in Figure 10. Figure 10. Experimental setup for testing and calibrating...Measuring the Free Spectral Range of the VIPA etalons Using the spectral fringes generated by the Michelson interferometer , we can quantify the spectral...Testing the FROG To test the FROG, we again used use the double pulse from a Michelson interferometer , which yields a FROG trace unlikely to occur by

  2. Measurement of the temperature dependence of pulse lengths in an n-type germanium detector

    NASA Astrophysics Data System (ADS)

    Abt, I.; Caldwell, A.; Liu, J.; Majorovits, B.; Volynets, O.

    2011-10-01

    The temperature dependence of the pulse length was measured for an 18-fold segmented n-type germanium detector in the temperature range of 77-120 K. The interactions of 122 keV photons originating from a 152Eu source were selected and pulses as observed on the core and segment electrodes were studied. In both cases, the temperature dependence can be well described by a Boltzmann-like ansatz.

  3. Vascular responsiveness measured by tissue oxygen saturation reperfusion slope is sensitive to different occlusion durations and training status.

    PubMed

    McLay, Kaitlin M; Gilbertson, James E; Pogliaghi, Silvia; Paterson, Donald H; Murias, Juan M

    2016-10-01

    What is the central question of this study? Is the near-infrared spectroscopy-derived measure of tissue oxygen saturation (StO2) reperfusion slope sensitive to a range of ischaemic conditions, and do differences exist between trained and untrained individuals? What is the main finding and its importance? The StO2 reperfusion rate is sensitive to different occlusion durations, and changes in the reperfusion slope in response to a variety of ischaemic challenges can be used to detect differences between two groups. These data indicate that near-infrared spectroscopy-derived measures of StO2, specifically the reperfusion slope following a vascular occlusion, can be used as a sensitive measure of vascular responsiveness. The reperfusion rate of near-infrared spectroscopy-derived measures of tissue oxygen saturation (StO2) represents vascular responsiveness. This study examined whether the reperfusion slope of StO2 is sensitive to different ischaemic conditions (i.e. a dose-response relationship) and whether differences exist between two groups of different fitness levels. Nine healthy trained (T; age 25 ± 3 years; maximal oxygen uptake 63.4 ± 6.7 ml kg(-1)  min(-1) ) and nine healthy untrained men (UT; age 21 ± 1 years; maximal oxygen uptake 46.6 ± 2.5 ml kg(-1)  min(-1) ) performed a series of vascular occlusion tests of different durations (30 s, 1, 2, 3 and 5 min), each separated by 30 min. The StO2 was measured over the tibialis anterior using near-infrared spectroscopy, with the StO2 reperfusion slope calculated as the upslope during 10 s following cuff release. The reperfusion slope was steeper in T compared with UT at all occlusion durations (P < 0.05). For the T group, the reperfusion slopes for 30 s and 1 min occlusions were less than for all longer durations (P < 0.05). The reperfusion slope following 2 min occlusion was similar to that for 3 min (P > 0.05), but both were less steep than for 5 min of occlusion. In UT, the

  4. Photocathode rf gun emittance measurements using variable-length laser pulses

    NASA Astrophysics Data System (ADS)

    Schmerge, John F.; Hernandez, Mike; Hogan, Mark J.; Reis, David A.; Winick, Herman

    1999-07-01

    The Gun Test Facility (GTF) at the Stanford Linear Accelerator Center (SLAC) was created to develop an appropriate injector for the proposed Linac Coherent Light Source (LCLS) at SLAC. The LCLS design requires the injector to produce a beam with at least 1 nC of charge in a 10 ps or shorter pulse with no greater than 1 (pi) mm-mrad normalized rms emittance. The first photoinjector under study at the GTF is a 1.6 cell S-band symmetrized gun with an emittance compensation solenoid. Emittance measurements, reported here, were made as function of the transverse laser pulse shape and the Gaussian longitudinal laser pulse length. The lowest achieved emittance to data with 1 nC of charge is 5.6 (pi) mm-mrad and was obtained with both a Gaussian longitudinal and transverse pulse shape with 5 ps FWHM and 2.4 mm FWHM respectively. The measurement is in agreement with a PARMELA simulation using measured beam parameters. There are indications that the accelerator settings used in the results presented here were not optimal. Simulations indicate that a normalized emittance meeting the LCLS requirement can be obtained using appropriately shaped transverse and temporal laser/electron beam pulses. Work has begun on producing temporal flat top laser pulses which combined with transverse clipping of the laser is expected to lower the emittance to approximately 1 (pi) mm-mrad for 1 nC beams with optimal accelerator settings.

  5. 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

    2015-04-27

    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.

  6. Reliability of BOD POD Measurements Remains High After a Short-Duration Low-Carbohydrate Diet.

    PubMed

    Greer, Beau Kjerulf; Edsall, Kathleen M; Greer, Anna E

    2016-04-01

    The purpose of the current study was to determine whether expected changes in body weight via a 3-day low-carbohydrate (LC) diet will disrupt the reliability of air displacement plethysmography measurements via BOD POD. Twenty-four subjects recorded their typical diets for 3 days before BOD POD and 7-site skinfold analyses. Subjects were matched for lean body mass and divided into low-CHO (LC) and control (CON) groups. The LC group was given instruction intended to prevent more than 50 grams/day of carbohydrate consumption for 3 consecutive days, and the CON group replicated their previously recorded diet. Body composition measurements were repeated after dietary intervention. Test-retest reliability measures were significant (p < .01) and high for body fat percentage in both the LC and the CON groups (rs = .993 and .965, respectively). Likewise, skinfold analysis for body fat percentage reliability was high in both groups (rs = .996 and .997, respectively). There were significant differences between 1st and 2nd BOD POD measurements for body mass (72.9 ± 13.3 vs. 72.1 ± 13.0 kg [M ± SD]) and body volume (69.0 ± 12.7-68.1 ± 12.2 L) in the LC group (p < .05). However, there were no differences (p > .05) in BOD POD-determined body fat percentage, lean body mass, or fat mass between the 1st and 2nd trial in either group. Body composition measures via BOD POD and 7-site skinfolds remain reliable after 3 days of an LC diet despite significant decreases in body mass.

  7. 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.

  8. 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.

  9. Absolute distance measurement by intensity detection using a mode-locked femtosecond pulse laser.

    PubMed

    Wu, Hanzhong; Zhang, Fumin; Cao, Shiying; Xing, Shujian; Qu, Xinghua

    2014-05-05

    We propose an interferometric method that enables to measure a distance by the intensity measurement using the scanning of the interferometer reference arm and the recording of the interference fringes including the brightest fringe. With the consideration of the dispersion and absorption of the pulse laser in a dispersive and absorptive medium, we investigate the cross-correlation function between two femtosecond laser pulses in the time domain. We also introduce the measurement principle. We study the relationship between the position of the brightest fringe and the distance measured, which can contribute to the distance measurement. In the experiments, we measure distances using the method of the intensity detection while the reference arm of Michelson interferometer is scanned and the fringes including the brightest fringe is recorded. Firstly we measure a distance in a range of 10 µm. The experimental results show that the maximum deviation is 45 nm with the method of light intensity detection. Secondly, an interference system using three Michelson interferometers is developed, which combines the methods of light intensity detection and time-of-flight. This system can extend the non-ambiguity range of the method of light intensity detection. We can determine a distance uniquely with a larger non-ambiguity range. It is shown that this method and system can realize absolute distance measurement, and the measurement range is a few micrometers in the vicinity of Nl(pp), where N is an integer, and lpp is the pulse-to-pulse length.

  10. 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.

  11. Direct Measurement of Basilar Membrane Motion Using Pulsed-Wave Doppler High-Frequency Ultrasound

    NASA Astrophysics Data System (ADS)

    Torbatian, Z.; Garland, P.; Adamson, R. B. A.; Bance, M.; Brown, J. A.

    2011-11-01

    We present a preliminary report on the use of a new technique for measuring the motion of the basilar membrane, high-frequency ultrasound Doppler vibrometry. Using a custom-built, 1 mm diameter probe, we collected ultrasonic reflections from intracochlear structures and applied pulsed-wave Doppler vibrometry to measure the basilar membrane response to pressure applied in the ear canal.

  12. 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.

  13. ±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.

  14. Measurement of ultrashort laser pulses using single-crystal films of 4-aminobenzophenone

    NASA Astrophysics Data System (ADS)

    Bhowmik, Achintya K.; Tan, Shida; Ahyi, Ayayi C.; Dharmadhikari, J. A.; Dharmadhikari, A. K.; Mathur, D.

    2007-12-01

    Single-crystal thin-film of an organic second-order nonlinear optical material, 4-aminobenzophenone (ABP), is used to measure the pulsewidth of a Ti-Sapphire laser producing ˜45 fs pulses at 1 kHz repetition rate, by the non-collinear second-harmonic generation (SHG) intensity autocorrelation technique. These films are suitable for measurements over a broad wavelength range, down to 780 nm, due to their wide optical transparency. The single-crystal film with thickness (˜3 μm) less than the coherence length requires no phase-matching for efficient broadband SHG. Pulse walk-off due to group-velocity mismatch (GVM) and temporal broadening of the pulses due to group-velocity dispersion (GVD) are found to be negligible. These effects have been estimated for pulse width down to few-cycle pulses (˜10 fs), and the analyses show that these films can be used to characterize such ultrashort optical pulses.

  15. Optoelectronic measurement of x-ray synchrotron pulses: A proof of concept demonstration

    NASA Astrophysics Data System (ADS)

    Durbin, Stephen M.; Mahmood, Aamer; Caffee, Marc; Savikhin, Sergei; Dufresne, Eric M.; Wen, Haidan; Li, Yuelin

    2013-02-01

    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 ˜50 ps x-ray pulse width convoluted with the ˜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.

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. Measurement and analysis of energy flow in Stirling-type pulse tube refrigerator

    NASA Astrophysics Data System (ADS)

    Ki, Taekyung; Jeong, Sangkwon; Seo, Mansu; Park, Inmyong

    2012-06-01

    The analysis of energy flow is a useful method for understanding a system. This paper focuses on the instantaneous measurement of physical conditions and analysis of energy flow in the Stirling-type pulse tube refrigerator. For measuring physical conditions of the working fluid such as the mass flow rate, the temperature, and the pressure, several cryogenic sensors are installed in the Stirling-type pulse tube refrigerator optimally designed in the operating condition of 60 Hz and 2.5 MPa. The physical conditions of the working fluid in the Stirling-type pulse tube refrigerator are carefully measured as varying the operating frequency and the charging pressure. From the measured results, the enthalpy, the PV work, and the loss are quantified in each location of the PTR and the conversion of energy flows is experimentally confirmed. The results of this paper can be used for understanding the optimal operating condition and modifying correlations of various losses in the Stirling-type pulse tube refrigerator. KEYWORDS: Energy flow, Loss, Pulse tube refrigerator

  2. Electron density and electron temperature measurements in nanosecond pulse discharges over liquid water surface

    NASA Astrophysics Data System (ADS)

    Simeni Simeni, M.; Roettgen, A.; Petrishchev, V.; Frederickson, K.; Adamovich, I. V.

    2016-12-01

    Time-resolved electron density, electron temperature, and gas temperature in nanosecond pulse discharges in helium and O2-He mixtures near liquid water surface are measured using Thomson/pure rotational Raman scattering, in two different geometries, (a) ‘diffuse filament’ discharge between a spherical high-voltage electrode and a grounded pin electrode placed in a reservoir filled with distilled water, with the tip exposed, and (b) dielectric barrier discharge between the high-voltage electrode and the liquid water surface. A diffuse plasma filament generated between the electrodes in helium during the primary discharge pulse exhibits noticeable constriction during the secondary discharge pulse several hundred ns later. Adding oxygen to the mixture reduces the plasma filament diameter and enhances constriction during the secondary pulse. In the dielectric barrier discharge, diffuse volumetric plasma occupies nearly the entire space between the high voltage electrode and the liquid surface, and extends radially along the surface. In the filament discharge in helium, adding water to the container results in considerable reduction of plasma lifetime compared to the discharge in dry helium, by about an order of magnitude, indicating rapid electron recombination with water cluster ions. Peak electron density during the pulse is also reduced, by about a factor of two, likely due to dissociative attachment to water vapor during the discharge pulse. These trends become more pronounced as oxygen is added to the mixture, which increases net rate of dissociative attachment. Gas temperature during the primary discharge pulse remains near room temperature, after which it increases up to T ~ 500 K over 5 µs and decays back to near room temperature before the next discharge pulse several tens of ms later. As expected, electron density and electron temperature in diffuse DBD plasmas are considerably lower compared to peak values in the filament discharge. Use of Thomson

  3. 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.

  4. Electric field measurements in a nanosecond pulse discharge by picosecond CARS/4-wave mixing

    NASA Astrophysics Data System (ADS)

    Goldberg, Ben; Shkurenkov, Ivan; Adamovich, Igor; Lempert, Walter

    2014-10-01

    Time-resolved electric field measurements in hydrogen by picosecond CARS/4-wave mixing are presented. Measurements are carried out in a high voltage nanosecond pulse discharge in hydrogen in plane-to-plane geometry, at pressures of up to several hundred Torr, and with a time resolution of 0.2 ns. Absolute calibration of the diagnostics is done using a sub-breakdown high voltage pulse of 12 kV/cm. A diffuse discharge is obtained by applying a peak high voltage pulse of 40 kV/cm between the electrodes. It is found that breakdown occurs at a lower field, 15--20 kV/cm, after which the field in the plasma is reduced rapidly due to plasma self shielding The experimental results are compared with kinetic modeling calculations, showing good agreement between the measured and the predicted electric field.

  5. Two-Pulsed Technique for Ablative Laser Propulsion: Force Measurement in Vacuum

    NASA Technical Reports Server (NTRS)

    Herren, Kenneth A.; Cohen, Timothy; Lin, Jun; Pakhomov, Andrew V.

    2004-01-01

    This is a continuation of studies using a two-pulsed technique for Ablative Laser Propulsion (ALP) extended to force measurements in vacuum. Aluminum samples were ablated using pairs of laser pulses, each of 100 ps width, 532 nm wavelength and 5 mJ energy. The pulses were temporally separated in the 0 - 0.67 ns range. The force imparted on Al targets was measured in situ by means of a piezoelectric force gauge. The preliminary results confirm the previously reported oscillatory behavior of ion velocity and number density observed by means of a time-of-flight energy analyzer. The uncertainties of presented measurements and future directions for the study are discussed.

  6. Adiabatic measurements of magneto-caloric effects in pulsed high magnetic fields up to 55 T

    NASA Astrophysics Data System (ADS)

    Kihara, T.; Kohama, Y.; Hashimoto, Y.; Katsumoto, S.; Tokunaga, M.

    2013-07-01

    Magneto-caloric effects (MCEs) measurement system in adiabatic condition is proposed to investigate the thermodynamic properties in pulsed magnetic fields up to 55 T. With taking the advantage of the fast field-sweep rate in pulsed field, adiabatic measurements of MCEs were carried out at various temperatures. To obtain the prompt response of the thermometer in the pulsed field, a thin film thermometer is grown directly on the sample surfaces. The validity of the present setup was demonstrated in the wide temperature range through the measurements on Gd at about room temperature and on Gd3Ga5O12 at low temperatures. The both results show reasonable agreement with the data reported earlier. By comparing the MCE data with the specific heat data, we could estimate the entropy as functions of magnetic field and temperature. The results demonstrate the possibility that our approach can trace the change in transition temperature caused by the external field.

  7. 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.

  8. Airborne 2-micron double-pulsed integrated path differential absorption lidar for column CO2 measurement

    NASA Astrophysics Data System (ADS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

    2014-10-01

    Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 mJ and up to 10 Hz repetition rate. The two laser pulses are separated by 200 µs 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-µm direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-μm 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.

  9. 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.

  10. Electric field simulation and measurement of a pulse line ion accelerator

    NASA Astrophysics Data System (ADS)

    Shen, Xiao-Kang; Zhang, Zi-Min; Cao, Shu-Chun; Zhao, Hong-Wei; Wang, Bo; Shen, Xiao-Li; Zhao, Quan-Tang; Liu, Ming; Jing, Yi

    2012-07-01

    An oil dielectric helical pulse line to demonstrate the principles of a Pulse Line Ion Accelerator (PLIA) has been designed and fabricated. The simulation of the axial electric field of an accelerator with CST code has been completed and the simulation results show complete agreement with the theoretical calculations. To fully understand the real value of the electric field excited from the helical line in PLIA, an optical electric integrated electric field measurement system was adopted. The measurement result shows that the real magnitude of axial electric field is smaller than that calculated, probably due to the actual pitch of the resister column which is much less than that of helix.

  11. 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.

  12. 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.

  13. Temperature measurements in small holes drilled in superconducting bulk during pulsed field magnetization

    NASA Astrophysics Data System (ADS)

    Fujishiro, H.; Naito, T.; Furuta, D.; Kakehata, K.

    2010-11-01

    The time dependence of the temperatures T(z, t) has been measured along the thickness direction z in several drilled holes in a superconducting bulk during pulsed field magnetization (PFM) and the heat generation and heat transfer in the bulk have been discussed. In the previous paper [H. Fujishiro, S. Kawaguchi, K. Kakehata, A. Fujiwara, T. Tateiwa, T. Oka, Supercond. Sci. Technol. 19 (2006) S540], we calculated the T(z, t) profiles in the bulk by solving a three-dimensional heat-diffusion equation to reproduce the measured T(t) on the bulk surface; the heat generation took place adiabatically and the calculated T(z, t) was isothermal along the z direction. In this study, the measured T(z, t) at the top surface was higher than that at the bottom surface just after the pulse field application at t < 0.5 s, and then became isothermal with increasing time. These results suggest that the magnetic flux intrudes inhomogeneously into the bulk from the edge of the top surface and the periphery at the early stage. The inhomogeneous magnetic flux intrusion and the flux trap during PFM change depending on the strength of the pulsed field and the pulse number in the successive pulse field application.

  14. 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.

  15. 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%.

  16. Estimating of pulsed electric fields using optical measurements.

    SciTech Connect

    Flanagan, Timothy McGuire; Chantler, Gary.

    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.

  17. Transverse emittance measurements from a photocathode RF gun with variable laser pulse length

    NASA Astrophysics Data System (ADS)

    Reis, D. A.; Hernandez, M.; Schmerge, J. F.; Winick, H.; Hogan, M. J.

    1999-06-01

    The gun test facility (GTF) at SSRL was started in 1996 to develop an appropriate injector for the proposed linac coherent light source (LCLS) at SLAC. The LCLS design requires the injector to produce a beam with at least 1 nC of charge in a 10 ps or shorter pulse with no greater than 1π mm mrad normalized rms emittance. The photoinjector at the GTF is 1.6 cell S-band symmetrized gun and emittance compensation solenoid. Emittance measurements, reported here, were made as function of laser pulse width using Gaussian longitudinal pulses. The lowest achieved emittance to date with 1 nC of charge is 5.6π mm mrad and was obtained with a pulse width of 5 ps (FWHM) and is in agreement with simulation. There are indications that the accelerator settings for these results may not have been optimal. Simulations also indicate that a normalized emittance meeting the LCLS requirement can be obtained using appropriately shaped transverse and temporal laser/electron beam pulses. Work has begun on producing temporal flat top laser pulses which combined with transverse clipping of the laser is expected to lower the emittance to approximately 1π mm mrad for 1 nC with optimal accelerator settings.

  18. Single-shot laser pulse reconstruction based on self-phase modulated spectra measurements

    PubMed Central

    Anashkina, Elena A.; Ginzburg, Vladislav N.; Kochetkov, Anton A.; Yakovlev, Ivan V.; Kim, Arkady V.; Khazanov, Efim A.

    2016-01-01

    We report a method for ultrashort pulse reconstruction based only on the pulse spectrum and two self-phase modulated (SPM) spectra measured after pulse propagation through thin media with a Kerr nonlinearity. The advantage of this method is that it is a simple and very effective tool for characterization of complex signals. We have developed a new retrieval algorithm that was verified by reconstructing numerically generated fields, such as a complex electric field of double pulses and few-cycle pulses with noises, pedestals and dips down to zero spectral intensity, which is challenging for commonly used techniques. We have also demonstrated a single-shot implementation of the technique for the reconstruction of experimentally obtained pulses. This method can be used for high power laser systems operating in a single-shot mode in the optical, near- and mid-IR spectral ranges. The method is robust, low cost, stable to noise, does not require a priori information, and has no ambiguity related to time direction. PMID:27646027

  19. Frequency-resolved optical gating measurement of ultrashort pulses by using single nanowire

    NASA Astrophysics Data System (ADS)

    Yu, Jiaxin; Liao, Feng; Gu, Fuxing; Zeng, Heping

    2016-09-01

    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.

  20. 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

  1. Single-shot laser pulse reconstruction based on self-phase modulated spectra measurements

    NASA Astrophysics Data System (ADS)

    Anashkina, Elena A.; Ginzburg, Vladislav N.; Kochetkov, Anton A.; Yakovlev, Ivan V.; Kim, Arkady V.; Khazanov, Efim A.

    2016-09-01

    We report a method for ultrashort pulse reconstruction based only on the pulse spectrum and two self-phase modulated (SPM) spectra measured after pulse propagation through thin media with a Kerr nonlinearity. The advantage of this method is that it is a simple and very effective tool for characterization of complex signals. We have developed a new retrieval algorithm that was verified by reconstructing numerically generated fields, such as a complex electric field of double pulses and few-cycle pulses with noises, pedestals and dips down to zero spectral intensity, which is challenging for commonly used techniques. We have also demonstrated a single-shot implementation of the technique for the reconstruction of experimentally obtained pulses. This method can be used for high power laser systems operating in a single-shot mode in the optical, near- and mid-IR spectral ranges. The method is robust, low cost, stable to noise, does not require a priori information, and has no ambiguity related to time direction.

  2. 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.

  3. 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

  4. Simple autocorrelator for ultraviolet pulse-width measurements based on the nonlinear photoelectric effect.

    PubMed

    Takagi, Y

    1994-09-20

    An optical pulse-width measurement in the ultraviolet spectral region has been performed in a simple manner by introducing into the second-order autocorrelator a nonlinear response of the optical detector based on the two-photon photoelectric effect. The pulse widths of the third, fourth, and fifth harmonics of a mode-locked Nd:YAG laser were measured by the use of a photomultiplier with a cesium iodide photocathode with a minimum required pulse energy of 10 nJ and a power density of 10 kW/cm(2). The effect of transient interband optical excitation with different photon energies on the intensity correlation profile was also studied for the case of a copper iodide photocathode, and the result provides a background-free intensity correlation in a part of the ultraviolet spectral region.

  5. 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.

  6. Investigation of pulse voltage shape effects on electrohydrodynamic jets using a vision measurement technique

    NASA Astrophysics Data System (ADS)

    Kwon, Kye-Si; Lee, Dae-Yong

    2013-06-01

    In this paper, we present a vision measurement technique to evaluate electrohydrodynamic (EHD) inkjet behavior, and discuss the effects of the pulse voltage shape on the EHD jets for drop-on-demand printing, including the falling and rising time in the pulse voltage. Sequential images acquired by a charge-coupled device (CCD) camera with a strobe light-emitting diode (LED) were used to visualize EHD jet behavior with respect to time. A vision algorithm was implemented in an EHD jet system to enable in situ measurement and analysis of EHD jets. A guideline for selecting pulse shape parameters is also presented, to enable the achievement of high-frequency reliable jets for drop-on-demand printing. Printing results are presented to demonstrate the drop consistency of jets.

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

    NASA Astrophysics Data System (ADS)

    Wada, Sanehiro; Furuichi, Noriyuki; Shimada, Takashi

    2016-11-01

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

  8. Measurement capabilities of a compact thermal-type standard of energy unit of pulse laser radiation

    NASA Astrophysics Data System (ADS)

    Skrzeczanowski, Wojciech

    2001-08-01

    New instrument for measurements of laser pulse energy is described. Due to its parameters it can be used as a standard for unit of energy of pulse laser radiation. The instrument consists of a control unit, three sources of laser radiation, two receivers of optical signal, and a laptop. The whole system can be easily transported enabling one to carry out measurements in situ, at customer's, not only in laboratory conditions. This is a very important feature of the instrument because it allows inexpensive calibration and testing of large industrial laser installations and interesting laboratory intercomparisons as well. A method of measurement used in operation of the standard is presented. Main characteristics of the standard are shown. Methods of calculation of uncertainties of measurement during laser energy meters calibration by means of the standard of energy unit of pulse laser radiation are also presented. An alternative measurement option of the standard operating as an energy calibrator for unknown pulse optical radiation source is also available. Some results of testing of laser energy meters at eye-safe wavelength (1.54 micrometer) are presented.

  9. White matter measures are near normal in controlled HIV infection except in those with cognitive impairment and longer HIV duration.

    PubMed

    Cysique, Lucette A; Soares, James R; Geng, Guangqiang; Scarpetta, Maia; Moffat, Kirsten; Green, Michael; Brew, Bruce J; Henry, Roland G; Rae, Caroline

    2017-03-21

    The objective of the current study was to quantify the degree of white matter (WM) abnormalities in chronic and virally suppressed HIV-infected (HIV+) persons while carefully taking into account demographic and disease factors. Diffusion tensor imaging (DTI) was conducted in 40 HIV- and 82 HIV+ men with comparable demographics and life style factors. The HIV+ sample was clinically stable with successful viral control. Diffusion was measured across 32 non-colinear directions with a b-value of 1000 s/mm(2); fractional anisotropy (FA) and mean diffusivity (MD) maps were quantified with Itrack IDL. Using the ENIGMA DTI protocol, FA and MD values were extracted for each participant and in 11 skeleton regions of interest (SROI) from standard labels in the JHU ICBM-81 atlas covering major striato-frontal and parietal tracks. We found no major differences in FA and MD values across the 11 SROI between study groups. Within the HIV+ sample, we found that a higher CNS penetrating antiretroviral treatment, higher current CD4+ T cell count, and immune recovery from the nadir CD4+ T cell count were associated with increased FA and decreased MD (p < 0.05-0.006), while HIV duration, symptomatic, and asymptomatic cognitive impairment were associated with decreased FA and increased MD (p < 0.01-0.004). Stability of HIV treatment and antiretroviral CNS penetration efficiency in addition to current and historical immune recovery were related to higher FA and lower MD (p = 0.04-p < 0.01). In conclusion, WM DTI measures are near normal except for patients with neurocognitive impairment and longer HIV disease duration.

  10. 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

  11. Pulsed magnetic field measurement using a ferrite waveguide in a phase bridge circuit

    SciTech Connect

    William A Pellico and Patrick Colestock

    2002-07-01

    There are several standard methods used for measuring pulsed magnetic fields. However the induction or Hall probe methods have limited bandwidth and experience reflection problems. The integrated magnetic field can only be found by measuring along the entire length of the magnet. Problems with reflections, noise and bandwidth will limit the accuracy of measurement. Presented in the following paper is a method for measuring pulsed fields without the typical noise errors and bandwidth limitations. This paper will describe a phase bridge network that relies upon the permeability of a ferrite waveguide to accurately measure the integrated field of a Main Injector kicker magnet. The authors present some data taken with the system, a first pass at the analysis of this data, and discuss some possible design variations.

  12. Development of a pulsed 2-micron integrated path differential absorption lidar for CO2 measurement

    NASA Astrophysics Data System (ADS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Reithmaier, Karl

    2013-09-01

    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.

  13. 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

  14. Time-domain measurement of terahertz frequency magnetoplasmon resonances in a two-dimensional electron system by the direct injection of picosecond pulsed currents

    NASA Astrophysics Data System (ADS)

    Wu, Jingbo; Sydoruk, Oleksiy; Mayorov, Alexander S.; Wood, Christopher D.; Mistry, Divyang; Li, Lianhe; Linfield, Edmund H.; Giles Davies, A.; Cunningham, John E.

    2016-02-01

    We have investigated terahertz (THz) frequency magnetoplasmon resonances in a two-dimensional electron system through the direct injection of picosecond duration current pulses. The evolution of the time-domain signals was measured as a function of magnetic field, and the results were found to be in agreement with calculations using a mode-matching approach for four modes observed in the frequency range above 0.1 THz. This introduces a generic technique suitable for sampling ultrafast carrier dynamics in low-dimensional semiconductor nanostructures at THz frequencies.

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

    SciTech Connect

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

    1981-08-28

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

  16. 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…

  17. 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.

  18. 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.

  19. On the Use of Double FM Pulses for Detection of Targets and Measurement of Their Properties

    DTIC Science & Technology

    1981-11-15

    This report discusses the use of double FM pulses to measure the sonar path length and rate of change of sonar path length (range and range rate in...the monostatic case) and length and rate of change of length or apparent turning rate for a long thin target such as a submarine. Equations are derived

  20. Heat pulse probe measurements of soil water evaporation in a corn field

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Latent heat fluxes from cropped fields consist of soil water evaporation and plant transpiration. It is difficult to accurately separate evapotranspiration into evaporation and transpiration. Heat pulse probes have been used to measure bare field subsurface soil water evaporation, however, the appl...

  1. 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.

  2. The paired-pulse index: a measure of hippocampal dentate granule cell modulation.

    PubMed

    Bronzino, J D; Blaise, J H; Morgane, P J

    1997-01-01

    This study was undertaken to assess whether the paired-pulse index (PPI) is an effective measure of the modulation of dentate granule cell excitability during normal development. Paired-pulse stimulations of the perforant path were, therefore, used to construct a PPI for 15-, 30-, and 90-day old, freely moving male rats. Significant age-dependent differences in the PPI were obtained. Fifteen-day old rats showed significantly less inhibition at short interpulse intervals [interpulse interval (IPI): 20 to 30 msec), a lack of facilitation at intermediate IPIs (50 to 150 msec), and significantly less inhibition at longer IPIs (300 to 1,000 msec) than adults.

  3. 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.

  4. A pulsed wire probe for the measurement of velocity and flow direction in slowly moving air.

    PubMed

    Olson, D E; Parker, K H; Snyder, B

    1984-02-01

    This report describes the theory and operation of a pulsed-probe anemometer designed to measure steady three-dimensional velocity fields typical of pulmonary tracheo-bronchial airflows. Local velocities are determined by measuring the transport time and orientation of a thermal pulse initiated at an upstream wire and sensed at a downstream wire. The transport time is a reproducible function of velocity and the probe wire spacing, as verified by a theoretical model of convective heat transfer. When calibrated the anemometer yields measurements of velocity accurate to +/- 5 percent and resolves flow direction to within 1 deg at airspeeds greater than or equal to 10 cm/s. Spatial resolution is +/- 0.5 mm. Measured flow patterns typical of curved circular pipes are included as examples of its application.

  5. 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.

  6. Compact high-pulse-energy ultraviolet laser source for ozone lidar measurements.

    PubMed

    Elsayed, Khaled A; DeYoung, Russell J; Petway, Larry B; Edwards, William C; Barnes, James C; Elsayed-Ali, Hani E

    2003-11-20

    An all solid-state Ti:sapphire laser differential absorption lidar transmitter was developed. This all-solid-state laser provides a compact, robust, and highly reliable laser transmitter for potential application in differential absorption lidar measurements of atmospheric ozone. Two compact, high-energy-pulsed, and injection-seeded Ti:sapphire lasers operating at a pulse repetition frequency of 30 Hz and wavelengths of 867 and 900 nm, with M2 of 1.3, have been experimentally demonstrated and their properties compared with model results. The output pulse energy was 115 mJ at 867 nm and 105 mJ at 900 nm, with a slope efficiency of 40% and 32%, respectively. At these energies, the beam quality was good enough so that we were able to achieve 30 mJ of ultraviolet laser output at 289 and 300 nm after frequency tripling with two lithium triborate nonlinear crystals.

  7. Low-noise pulsed current source for magnetic-field measurements of magnets for accelerators

    NASA Astrophysics Data System (ADS)

    Omelyanenko, M. M.; Borisov, V. V.; Donyagin, A. M.; Khodzhibagiyan, H. G.; Kostromin, S. A.; Makarov, A. A.; Shemchuk, A. V.

    2017-01-01

    The schematic diagram, design, and technical characteristics of the pulsed current source developed and produced for the magnetic-field measurement system of superconducting magnets for accelerators are described. The current source is based on the current regulator with pass transistor bank in the linear mode. Output current pulses (0-100 A) are produced by utilizing the energy of the preliminarily charged capacitor bank (5-40 V), which is additionally charged between pulses. The output current does not have the mains frequency and harmonics ripple. The relative noise level is less than-100 dB (or 10-5) of RMS value (it is defined as the ratio of output RMS noise current to a maximal output current of 100 A within the operating bandwidth, expressed in dB). The work was performed at the Veksler and Baldin Laboratory of High Energy Physics, Joint Institute for Nuclear Research (JINR).

  8. 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

  9. Curling probe measurement of a large-volume pulsed plasma with surface magnetic confinement

    NASA Astrophysics Data System (ADS)

    Pandey, A.; Tashiro, H.; Sakakibara, W.; Nakamura, K.; Sugai, H.

    2016-12-01

    A curling probe (CP) based on microwave resonance is applied to the measurement of electron density in a pulsed DC glow discharge under surface magnetic confinement (SMC) provided by a number of permanent magnets on a chamber wall. Owing to the SMC effects, a 1 m scale large-volume plasma is generated by a relatively low voltage (~1 kV) at low pressure (~1 Pa) in various gases (Ar, CH4, and C2H2). Temporal variation of the electron density is measured for pulse frequency f  =  0.5-25 kHz for various discharge-on times (T ON) with a high resolution time (~0.2 µs), using the on-point mode. In general, the electron density starts to increase at time t  =  0 after turn-on of the discharge voltage, reaches peak density at t  =  T ON, and then decreases after turn-off. The peak electron density is observed to increase with the pulse frequency f for constant T ON owing to the residual plasma. This dependence is successfully formulated using a semi-empirical model. The spatio-temporal evolution of the cathode sheath in the pulsed discharge is revealed by a 1 m long movable CP. The measured thickness of the high-voltage cathode fall in a steady state coincides with the value of the so-called Child-Langmuir sheath.

  10. Measurements on a FET based 1 MHz, 10 kV pulse generator

    SciTech Connect

    Wait, G.D.; Barnes, M.J.

    1995-08-01

    A prototype pulser, which incorporates thirty-two 1 kV Field-Effect Transistor (FET) modules, has been built and tested at TRIUMF. The pulser has been developed for application in a scheme for pulsed extraction from the TRIUMF 500 MeV cyclotron. Deflection of the beam will be provided by an electric field between a set of 1 in long deflector plates. The pulser generates a continuous, unipolar, pulse train at a fundamental frequency of approximately 1 MHz and a magnitude of 10 kV. The pulses have 38 ns rise and fall times and are stored on a low-loss coaxial cable which interconnects the pulse generator and the deflector plates. The circuit performance was evaluated with the aid of PSpice in the design stage and confirmed by measurements on the prototype. Temperature measurements have been performed on 1 kV FET modules under DC conditions and compared with temperatures under operating conditions to ensure that switching losses are acceptable. Results of various measurements are presented and compared with simulations.

  11. Measurement of the Pulse Radiation of an IRA in Time Domain

    NASA Astrophysics Data System (ADS)

    Stadtler, Thiemo; Ter Haseborg, Jan Luiken; Sabath, Frank

    For radiation of UWB pulses special Impulse Radiating Antennas (IRA) have been designed and are continuously improved. The measurement of its near field can help optimizing this antenna type. This paper presents a time domain scanner which is able to determine the transient near field. The so called double probe near field scanner can be employed to measure the two dimensional field distribution in time domain.

  12. 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.

  13. PULSE GENERATOR

    DOEpatents

    Roeschke, C.W.

    1957-09-24

    An improvement in pulse generators is described by which there are produced pulses of a duration from about 1 to 10 microseconds with a truly flat top and extremely rapid rise and fall. The pulses are produced by triggering from a separate input or by modifying the current to operate as a free-running pulse generator. In its broad aspect, the disclosed pulse generator comprises a first tube with an anode capacitor and grid circuit which controls the firing; a second tube series connected in the cathode circuit of the first tube such that discharge of the first tube places a voltage across it as the leading edge of the desired pulse; and an integrator circuit from the plate across the grid of the second tube to control the discharge time of the second tube, determining the pulse length.

  14. A comparison of systolic blood pressure measurement obtained using a pulse oximeter, and direct systolic pressure measurement in anesthetized sows.

    PubMed Central

    Caulkett, N A; Duke, T; Bailey, J V

    1994-01-01

    Systolic blood pressure measurement obtained with a pulse oximeter has been compared to values obtained by other indirect methods in man. Direct pressure measurement is subject to less error than indirect techniques. This study was designed to compare systolic pressure values obtained using a pulse oximeter, with values obtained by direct arterial pressure measurement. The pulse oximeter waveform was used as an indication of perfusion. A blood pressure cuff was applied proximal to the pulse oximeter probe. The cuff was inflated until the oximeter waveform disappeared, this value was recorded as the systolic pressure at the disappearance of the waveform (SPD). The cuff was inflated to a pressure > 200 mmHg, then gradually deflated until the waveform reappeared, this value was recorded as the systolic pressure at reappearance of the waveform (SPR). The average of the two values, SPD and SPR, was calculated and recorded as SPA. The study was performed in sows (n = 21) undergoing cesarean section under epidural anesthesia and IV sedation. A total of 280 measurements were made of SPD, SPR and SPA. Regression analysis of SPA and direct measurement revealed a correlation coefficient (r) of 0.81. Calculation of mean difference (bias) and standard deviation of the bias (precision) for direct pressure--SPA revealed a value of 1.3 +/- 12.1. When compared with direct measurement, the correlation of this technique was similar to that recorded for other indirect techniques used in small animals. This indicates that this technique would be useful for following systolic pressure trends.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8004540

  15. 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.

  16. Gd(III)-Gd(III) distance measurements with chirp pump pulses.

    PubMed

    Doll, Andrin; Qi, Mian; Wili, Nino; Pribitzer, Stephan; Godt, Adelheid; Jeschke, Gunnar

    2015-10-01

    The broad EPR spectrum of Gd(III) spin labels restricts the dipolar modulation depth in distance measurements between Gd(III) pairs to a few percent. To overcome this limitation, frequency-swept chirp pulses are utilized as pump pulses in the DEER experiment. Using a model system with 3.4 nm Gd-Gd distance, application of one single chirp pump pulse at Q-band frequencies leads to modulation depths beyond 10%. However, the larger modulation depth is counteracted by a reduction of the absolute echo intensity due to the pump pulse. As supported by spin dynamics simulations, this effect is primarily driven by signal loss to double-quantum coherence and specific to the Gd(III) high spin state of S=7/2. In order to balance modulation depth and echo intensity for optimum sensitivity, a simple experimental procedure is proposed. An additional improvement by 25% in DEER sensitivity is achieved with two consecutive chirp pump pulses. These pulses pump the Gd(III) spectrum symmetrically around the observation position, therefore mutually compensating for dynamical Bloch-Siegert phase shifts at the observer spins. The improved sensitivity of the DEER data with modulation depths on the order of 20% is due to mitigation of the echo reduction effects by the consecutive pump pulses. In particular, the second pump pulse does not lead to additional signal loss if perfect inversion is assumed. Moreover, the compensation of the dynamical Bloch-Siegert phase prevents signal loss due to spatial dependence of the dynamical phase, which is caused by inhomogeneities in the driving field. The new methodology is combined with pre-polarization techniques to measure long distances up to 8.6 nm, where signal intensity and modulation depth become attenuated by long dipolar evolution windows. In addition, the influence of the zero-field splitting parameters on the echo intensity is studied with simulations. Herein, larger sensitivity is anticipated for Gd(III) complexes with zero-field splitting

  17. Gd(III)-Gd(III) distance measurements with chirp pump pulses

    NASA Astrophysics Data System (ADS)

    Doll, Andrin; Qi, Mian; Wili, Nino; Pribitzer, Stephan; Godt, Adelheid; Jeschke, Gunnar

    2015-10-01

    The broad EPR spectrum of Gd(III) spin labels restricts the dipolar modulation depth in distance measurements between Gd(III) pairs to a few percent. To overcome this limitation, frequency-swept chirp pulses are utilized as pump pulses in the DEER experiment. Using a model system with 3.4 nm Gd-Gd distance, application of one single chirp pump pulse at Q-band frequencies leads to modulation depths beyond 10%. However, the larger modulation depth is counteracted by a reduction of the absolute echo intensity due to the pump pulse. As supported by spin dynamics simulations, this effect is primarily driven by signal loss to double-quantum coherence and specific to the Gd(III) high spin state of S = 7/2. In order to balance modulation depth and echo intensity for optimum sensitivity, a simple experimental procedure is proposed. An additional improvement by 25% in DEER sensitivity is achieved with two consecutive chirp pump pulses. These pulses pump the Gd(III) spectrum symmetrically around the observation position, therefore mutually compensating for dynamical Bloch-Siegert phase shifts at the observer spins. The improved sensitivity of the DEER data with modulation depths on the order of 20% is due to mitigation of the echo reduction effects by the consecutive pump pulses. In particular, the second pump pulse does not lead to additional signal loss if perfect inversion is assumed. Moreover, the compensation of the dynamical Bloch-Siegert phase prevents signal loss due to spatial dependence of the dynamical phase, which is caused by inhomogeneities in the driving field. The new methodology is combined with pre-polarization techniques to measure long distances up to 8.6 nm, where signal intensity and modulation depth become attenuated by long dipolar evolution windows. In addition, the influence of the zero-field splitting parameters on the echo intensity is studied with simulations. Herein, larger sensitivity is anticipated for Gd(III) complexes with zero

  18. Measurement and Modeling of Dispersive Pulse Propagation in Drawn Wire Waveguides

    NASA Technical Reports Server (NTRS)

    Madaras, Eric I.; Kohl, Thomas W.; Rogers, Wayne P.

    1995-01-01

    An analytical model of dispersive pulse propagation in semi-infinite cylinders due to transient axially symmetric end conditions has been experimentally investigated. Specifically, the dispersive propagation of the first axially symmetric longitudinal mode in thin wire waveguides, which have ends in butt contact with longitudinal piezoelectric ultrasonic transducers, is examined. The method allows for prediction of a propagated waveform given a measured source waveform, together with the material properties of the cylinder. Alternatively, the source waveform can be extracted from measurement of the propagated waveform. The material properties required for implementation of the pulse propagation model are determined using guided wave phase velocity measurements. Hard tempered aluminum 1100 and 304 stainless steel wires, with 127, 305, and 406 micron diam., were examined. In general, the drawn wires were found to behave as transversely isotropic media.

  19. Measurement and modeling of dispersive pulse propagation in draw wire waveguides

    NASA Technical Reports Server (NTRS)

    Madaras, Eric I.; Kohl, Thomas W.; Rogers, Wayne P.

    1995-01-01

    An analytical model of dispersive pulse propagation in semi-infinite cylinders due to transient axially symmetric end conditions has been experimentally investigated. Specifically, the dispersive propagation of the first axially symmetric longitudinal mode in thin wire waveguides, which have ends in butt contact with longitudinal piezoelectric ultrasonic transducers, is examined. The method allows for prediction of a propagated waveform given a measured source waveform, together with the material properties of the cylinder. Alternatively, the source waveform can be extracted from measurement of the propagated waveform. The material properties required for implementation of the pulse propagation model are determined using guided wave phase velocity measurements. Hard tempered aluminum 1100 and 304 stainless steel wires, with 127, 305, and 406 micron diam., were examined. In general, the drawn wires were found to behave as transversely isotropic media.

  20. Short pulse radar used to measure sea surface wind speed and SWH. [Significant Wave Height

    NASA Technical Reports Server (NTRS)

    Hammond, D. L.; Mennella, R. A.; Walsh, E. J.

    1977-01-01

    A joint airborne measurement program is being pursued by NRL and NASA Wallops Flight Center to determine the extent to which wind speed and sea surface significant wave height (SWH) can be measured quantitatively and remotely with a short pulse (2 ns), wide-beam (60 deg), nadir-looking 3-cm radar. The concept involves relative power measurements only and does not need a scanning antenna, Doppler filters, or absolute power calibration. The slopes of the leading and trailing edges of the averaged received power for the pulse limited altimeter are used to infer SWH and surface wind speed. The interpretation is based on theoretical models of the effects of SWH on the leading edge shape and rms sea-surface slope on the trailing-edge shape. The models include the radar system parameters of antenna beam width and pulsewidth.

  1. Interpretation of measured data and the resolution analysis of the RTP 4-channel pulsed radar

    NASA Astrophysics Data System (ADS)

    Pavlo, Pavol

    1993-01-01

    An analysis is conducted of a four-channel pulsed radar for a tokamak; the radar's accuracies are dependent on time-of-flight measurements and number of sampling frequencies. Because the configuration is already established, emphasis is here placed on the interpretation of measured data and overall error minimization. The central density considered is above the critical density of all four frequencies, but not so high as to restrict measurements to the edge of the plasma. The overall error in estimating the reflection point position is obtained by balancing the inversion error and the time-measurement error.

  2. Pulsed holographic microscopy as a measurement method of dynamic fracture toughness for fast propagating cracks

    NASA Astrophysics Data System (ADS)

    Suzuki, Shinichi; Homma, Hiroomi; Kusaka, Riichiro

    A METHOD OF pulsed holographic microscopy is applied to take instantaneous microscopic photographs of the neighborhoods of crack tips propagating through PMMA or through AISI 4340 steel specimens at a speed of several hundred meters per second. The cracks are in the opening mode. A fast propagating crack is recorded as a hologram at an instant during its propagation. A microscopic photograph of the crack is taken with a conventional microscope to magnify the reconstructed image from the hologram. From the microscopic photograph, crack opening displacement (COD) is measured along the crack in the vicinity of the crack tip. The COD is of the order often to one hundred microns, and in proportion to the square root of the distance from the crack tip. The dynamic fracture toughness KID is obtained using the formula for COD in the singular stress field of a fast propagating crack. Simultaneous KID measurement both through pulsed holographic microscopy and through the caustic method is furthermore carried out with PMMA specimens. The values of KID obtained through pulsed holographic microscopy are in agreement with those through the caustic method. Microcracks accompanied by a main crack are also photographed with the method of pulsed holographic microscopy.

  3. Hole boring velocity measurements in near critical density plasmas by a CO2 laser pulse

    NASA Astrophysics Data System (ADS)

    Gong, Chao; Tochitsky, Sergei; Pigeon, Jeremy; Joshi, Chan

    2014-10-01

    Measurements of plasma dynamics during the interaction of a high-power laser pulse with an above critical density plasma is important for understanding absorption, transport and particle acceleration mechanisms. An important process that affects these mechanisms is hole boring occurring at the critical density because of the radiation pressure of the laser pulse. Yet, no systematic measurements of the hole boring velocity's (vhb) dependence on laser intensity (I) have been made. In this talk, we present experimental results of vhb in near critical density plasmas produced by CO2 laser as a function of I in the range of 1*1015 to 1.6*1016 W/cm2. A novel four frame Mach-Zehnder interferometer using a 1 ps, 532 nm probe laser pulse was developed to record the evolution of the plasma density profile and the motion of the near critical density layer. Using this diagnostic, we observed the motion of the steepened plasma profile due to the incident, time-structured CO2 laser pulse. Experimental results show the hole boring velocity increases from 0.004c to 0.007c as the laser intensity is increased from 1*1015 to 1.6*1016 W/cm2. This work is supported by DOE grant DE-FG02-92-ER40727, NSF grant PHY-0936266 at UCLA.

  4. Validation of noninvasive MOEMS-assisted measurement system based on CCD sensor for radial pulse analysis.

    PubMed

    Malinauskas, Karolis; Palevicius, Paulius; Ragulskis, Minvydas; Ostasevicius, Vytautas; Dauksevicius, Rolanas

    2013-04-22

    Examination of wrist radial pulse is a noninvasive diagnostic method, which occupies a very important position in Traditional Chinese Medicine. It is based on manual palpation and therefore relies largely on the practitioner's subjective technical skills and judgment. Consequently, it lacks reliability and consistency, which limits practical applications in clinical medicine. Thus, quantifiable characterization of the wrist pulse diagnosis method is a prerequisite for its further development and widespread use. This paper reports application of a noninvasive CCD sensor-based hybrid measurement system for radial pulse signal analysis. First, artery wall deformations caused by the blood flow are calibrated with a laser triangulation displacement sensor, following by the measurement of the deformations with projection moiré method. Different input pressures and fluids of various viscosities are used in the assembled artificial blood flow system in order to test the performance of laser triangulation technique with detection sensitivity enhancement through microfabricated retroreflective optical element placed on a synthetic vascular graft. Subsequently, the applicability of double-exposure whole-field projection moiré technique for registration of blood flow pulses is considered: a computational model and representative example are provided, followed by in vitro experiment performed on a vascular graft with artificial skin atop, which validates the suitability of the technique for characterization of skin surface deformations caused by the radial pulsation.

  5. Noninvasive Measurement of Central Vascular Pressures With Arterial Tonometry: Clinical Revival of the Pulse Pressure Waveform?

    PubMed Central

    Nelson, Matthew R.; Stepanek, Jan; Cevette, Michael; Covalciuc, Michael; Hurst, R. Todd; Tajik, A. Jamil

    2010-01-01

    The arterial pulse has historically been an essential source of information in the clinical assessment of health. With current sphygmomanometric and oscillometric devices, only the peak and trough of the peripheral arterial pulse waveform are clinically used. Several limitations exist with peripheral blood pressure. First, central aortic pressure is a better predictor of cardiovascular outcome than peripheral pressure. Second, peripherally obtained blood pressure does not accurately reflect central pressure because of pressure amplification. Lastly, antihypertensive medications have differing effects on central pressures despite similar reductions in brachial blood pressure. Applanation tonometry can overcome the limitations of peripheral pressure by determining the shape of the aortic waveform from the radial artery. Waveform analysis not only indicates central systolic and diastolic pressure but also determines the influence of pulse wave reflection on the central pressure waveform. It can serve as a useful adjunct to brachial blood pressure measurements in initiating and monitoring hypertensive treatment, in observing the hemodynamic effects of atherosclerotic risk factors, and in predicting cardiovascular outcomes and events. Radial artery applanation tonometry is a noninvasive, reproducible, and affordable technology that can be used in conjunction with peripherally obtained blood pressure to guide patient management. Keywords for the PubMed search were applanation tonometry, radial artery, central pressure, cardiovascular risk, blood pressure, and arterial pulse. Articles published from January 1, 1995, to July 1, 2009, were included in the review if they measured central pressure using radial artery applanation tonometry. PMID:20435839

  6. Time resolved QCLAS measurements in pulsed cc-rf CF4/H2 plasmas

    NASA Astrophysics Data System (ADS)

    Stepanov, S.; Welzel, S.; Röpcke, J.; Meichsner, J.

    2009-03-01

    Fluorocarbon containing capacitively coupled radio frequency (cc-rf) plasmas are widely used in technical applications and as model systems for fundamental investigations of complex plasmas. Absorption spectroscopy based on pulsed quantum cascade lasers (QCL) was applied in the mid-IR spectral range of 1269-1275 cm-1. Absolute densities of the precursor molecule CF4 and of the stable product C3F8 were measured with a time resolution of up to 1 ms in pulsed CF4/H2 asymmetrical cc-rf (13.56 MHz) discharges. For this purpose both the non-negligible temperature dependence of the absorption coefficients and the interference of the absorption features of CF4 and C3F8 had to be taken into account in the target spectral range. Therefore, at two different spectral positions composite absorption spectra were acquired under the same plasma conditions in order to discriminate between CF4 and C3F8 contributions. A total consumption of~ 12 % was observed for CF4 during a 1 s plasma pulse, whereas C3F8 appeared to be produced mainly from amorphous fluorocarbon layers deposited at the reactor walls. A gas temperature increase by ~ 100 K in the plasma pulse was estimated from the measurements. Additionally, not yet identified unresolved absorption (potentially from the excited CF4 molecule) was found during the àon-phase'.

  7. Using phase retrieval to measure the intensity and phase of ultrashort pulses: Frequency-resolved optical gating

    SciTech Connect

    Trebino, R. ); Kane, D.J. )

    1993-05-01

    The authors recently introduced a new technique, frequency-resolved optical gating (FROG). For directly determining the full intensity I(t) and phase [var phi](t) of a single femtosecond pulse. By using almost any instantaneous nonlinear-optical interaction of two replicas of the ultrashort pulse to be measured, FROG involves measuring the spectrum of the signal pulse as a function of the delay between the replicas. The resulting trace of intensity versus frequency and delay yields an intuitive display of the pulse that is similar to the pulse spectrogram, except that the gate is a function of the pulse to be measured. The problem of inverting the FROG trace to obtain the pulse intensity and phase can also be considered a complex two-dimensional phase-retrieval problem. As a result, the FROG trace yields, in principle, an essentially unique pulse intensity and phase. It is shown that this is also the case in practice. An iterative-Fourier-transform algorithm is presented for inverting the FROG trace. The algorithm is unusual in its use of a novel constraint: the mathematical form of the signal field. Without the use of a support constraint, the algorithm performs quite well in practice, even for pulses with serious phase distortions and for experimental data with noise, although it occasionally stagnates when pulses with large intensity fluctuations are used. 49 refs., 15 figs.

  8. Measurement of electron density transients in pulsed RF discharges using a frequency boxcar hairpin probe

    NASA Astrophysics Data System (ADS)

    Peterson, David; Coumou, David; Shannon, Steven

    2015-11-01

    Time resolved electron density measurements in pulsed RF discharges are shown using a hairpin resonance probe using low cost electronics, on par with normal Langmuir probe boxcar mode operation. Time resolution of 10 microseconds has been demonstrated. A signal generator produces the applied microwave frequency; the reflected waveform is passed through a directional coupler and filtered to remove the RF component. The signal is heterodyned with a frequency mixer and rectified to produce a DC signal read by an oscilloscope. At certain points during the pulse, the plasma density is such that the applied frequency is the same as the resonance frequency of the probe/plasma system, creating reflected signal dips. The applied microwave frequency is shifted in small increments in a frequency boxcar routine to determine the density as a function of time. A dc sheath correction is applied for the grounded probe, producing low cost, high fidelity, and highly reproducible electron density measurements. The measurements are made in both inductively and capacitively coupled systems, the latter driven by multiple frequencies where a subset of these frequencies are pulsed. Measurements are compared to previous published results, time resolved OES, and in-line measurement of plasma impedance. This work is supported by the NSF DOE partnership on plasma science, the NSF GOALI program, and MKS Instruments.

  9. Masimo Rad-57 Pulse CO-Oximeter for noninvasive carboxyhemoglobin measurement.

    PubMed

    Suner, Selim; McMurdy, John

    2009-03-01

    Noninvasive methods of body fluid chemical measurement have been expanding. New technologies are enabling the quantification of different compounds in the blood and interstitial tissues. One example of this is the pulse oximeter, which has facilitated the measurement of oxyhemoglobin rapidly and reliably without the requirement of blood-draws. The Masimo Rad-57 Pulse CO-Oximeter expanded the capabilities of pulse-oximetry to include measurements of carboxyhemoglobin and methemoglobin. This innovation has revolutionized the paradigm for detection of patients with CO poisoning. Previously, clinicians relied on historical information and patient signs and symptoms pointing to the possibility of CO exposure or toxicity. Only then would a blood test be ordered to measure carboxyhemoglobin levels. Since the presentation of CO poisoning is nonspecific and overlaps with many other conditions, and since the presence of environmental CO is often unknown, the detection of this condition was only possible in cases where the presence of CO was obvious or where the symptoms were severe. We now know, from studies conducted using the Rad-57, the only US FDA-approved device for noninvasive measurement of SpCO, that there are a significant number of patients who experience CO exposure but are nonsymptomatic. The Rad-57 provides a clinical justification for screening in the healthcare setting to identify patients with significant CO exposure who would otherwise be undetected.

  10. Concordance among Measurements Obtained by Three Pulse Oximeters Currently Used by Health Professionals

    PubMed Central

    De La Rosa Hormiga, Milagros; MaríA Ramal LóPez, Josefa; DéNiz Rivero, Yasmina; Sandra Marrero Morales, MaríA

    2014-01-01

    Introduction: Oxygen saturation is considered as the 5th vital sign. Presently, there exist fixed and wireless pulse oximeters, being the latter most widely used in the last years. Some of them have no possibility of calibration. This situation leads the health staff to adopt therapeutic attitudes which can be wrong. Therefore, it is extremely important to know if these wireless oximeters show a right concordance as regards measurements, since it is of great interest in daily clinical practice. Objective: To evaluate concordance among measurements obtained by three different pulse oximeters currently used by health professionals. Materials and Methods: This is an observational, descriptive and cross-sectional study related to the concordance of the results obtained in measurements collected by three different pulse oximeters (one monitor and two wireless oximeters) which are available and in use in this hospital unit. The sample size calculation was performed for a concordance above 0.81 and an estimation error which did not exceed 0.20. The intraclass correlation index (ICI) was used to establish the concordance whereas the Landis-Koch criteria were used to interpret the results. Systematic errors were analyzed using the Bland-Altman plot. Results: The overall concordance among the three pulse oximeters analyzed resulted in 0.88, a value considered as “good” according to the Landis-Koch criteria. Conclusion: The results obtained show that in daily clinical practice both wireless pulse oximeters analyzed can be used with a certain reliability, taking into account the limitations of this research. PMID:25302228

  11. Comparing methods for measuring peak look duration: are individual differences observed on screen-based tasks also found in more ecologically valid contexts?

    PubMed

    Wass, Sam V

    2014-08-01

    Convergent research points to the importance of studying the ontogenesis of sustained attention during the early years of life, but little research hitherto has compared and contrasted different techniques available for measuring sustained attention. Here, we compare methods that have been used to assess one parameter of sustained attention, namely infants' peak look duration to novel stimuli. Our focus was to assess whether individual differences in peak look duration are stable across different measurement techniques. In a single cohort of 42 typically developing 11-month-old infants we assessed peak look duration using six different measurement paradigms (four screen-based, two naturalistic). Zero-order correlations suggested that individual differences in peak look duration were stable across all four screen-based paradigms, but no correlations were found between peak look durations observed on the screen-based and the naturalistic paradigms. A factor analysis conducted on the dependent variable of peak look duration identified two factors. All four screen-based tasks loaded onto the first factor, but the two naturalistic tasks did not relate, and mapped onto a different factor. Our results question how individual differences observed on screen-based tasks manifest in more ecologically valid contexts.

  12. Effects of free convection and friction on heat-pulse flowmeter measurement

    NASA Astrophysics Data System (ADS)

    Lee, Tsai-Ping; Chia, Yeeping; Chen, Jiun-Szu; Chen, Hongey; Liu, Chen-Wuing

    2012-03-01

    SummaryHeat-pulse flowmeter can be used to measure low flow velocities in a borehole; however, bias in the results due to measurement error is often encountered. A carefully designed water circulation system was established in the laboratory to evaluate the accuracy and precision of flow velocity measured by heat-pulse flowmeter in various conditions. Test results indicated that the coefficient of variation for repeated measurements, ranging from 0.4% to 5.8%, tends to increase with flow velocity. The measurement error increases from 4.6% to 94.4% as the average flow velocity decreases from 1.37 cm/s to 0.18 cm/s. We found that the error resulted primarily from free convection and frictional loss. Free convection plays an important role in heat transport at low flow velocities. Frictional effect varies with the position of measurement and geometric shape of the inlet and flow-through cell of the flowmeter. Based on the laboratory test data, a calibration equation for the measured flow velocity was derived by the least-squares regression analysis. When the flowmeter is used with a diverter, the range of measured flow velocity can be extended, but the measurement error and the coefficient of variation due to friction increase significantly. At higher velocities under turbulent flow conditions, the measurement error is greater than 100%. Our laboratory experimental results suggested that, to avoid a large error, the heat-pulse flowmeter measurement is better conducted in laminar flow and the effect of free convection should be eliminated at any flow velocities. Field measurement of the vertical flow velocity using the heat-pulse flowmeter was tested in a monitoring well. The calibration of measured velocities not only improved the contrast in hydraulic conductivity between permeable and less permeable layers, but also corrected the inconsistency between the pumping rate and the measured flow rate. We identified two highly permeable sections where the horizontal

  13. Validation of lactate measurement in American flamingo (Phoenicopterus ruber) plasma and correlation with duration and difficulty of capture.

    PubMed

    Burgdorf-Moisuk, Anne; Wack, Raymund; Ziccardi, Michael; Larsen, R Scott; Hopper, Kate

    2012-09-01

    Capture myopathy and associated death have been reported with capture and restraint of greater flamingos (Phoenicopterus ruber roseus) and lesser flamingos (Phoeniconaias minor). In chickens (Gallus gallus), blood lactate concentration levels have been used as indicators of muscle damage. Lactate has also been used to predict survival in humans and dogs. The goals of this study were to validate two common methods for measuring lactate (i-STAT and VetTest analyzers) in flamingo plasma by comparing measurements to a reference analyzer; and to correlate blood lactate concentration levels in captured flamingos with the duration and difficulty of capture as a possible indicator of capture myopathy. Twenty-seven banked flamingo plasma samples were run in triplicate on each of the three blood analyzers. Values from the i-STAT analyzer were consistently lower than those from the ABL analyzer, while values from the VetTest were consistently higher than those from the ABL analyzer. However, there was a good level of correlation between all three analyzers. Two of the three analyzers were determined to have acceptable total allowable error levels, calculated at 3.6% for the ABL and 10.7% for the VetTest. For clinical purposes, both the i-STAT and the VetTest analyzers provide adequate evaluation of lactate levels when serial samples are measured on the same analyzer. After validating the assay, 34 captive flamingos were captured for routine examinations. Blood lactate concentration levels were positively correlated with the length of time of the individual capture, but lactate did not increase significantly as capture difficulty increased. Only one animal was considered to have a difficult capture. No flamingos demonstrated clinical signs of capture myopathy during this study. Further research is required to determine if blood lactate concentration is a useful indicator of capture myopathy.

  14. Multiplexed Chirped Pulse Quantum Cascade Laser Measurements of Ammonia and Other Small Molecules

    NASA Astrophysics Data System (ADS)

    Picken, Craig; Langford, Nigel; Duxbury, Geoffrey

    2014-06-01

    Spectrometers based on Quantum Cascade (QC) lasers can be run in either continuous or pulsed operation. Although the instrumentation based upon the most recent versions of continuously operating QC lasers can have higher resolution than chirped lasers, using chirped pulse QC lasers can give an advantage when rapid changes in gas composition occur. For example, when jet engines are being tested, a variety of temperature dependent effects on the trace gas concentrations of the plume may be observed. Most pulsed QC lasers are operated in the down chirped mode, in which the chirp rate slows during the pulse. In our spectrometer the changes in frequency are recorded using two Ge etalons, one with a free spectral range of 0.0495 cm-1, and the other with a fringe spacing of 0.0195 cm-1.They can also be deployed in multiplex schemes in which two or more down-chirped lasers are used. In this paper we wish to show examples of the use of multiplexed chirped pulse lasers to allow overlapping spectra to be recorded. The examples of multiplex methods used are taken partly from measurements of 14NH3 and 15NH3 in the region from 1630 to 1622 cm-1, and partly from the use of other chirped pulse lasers operating in the 8 μm region. Among the effects seen are rapid passage effects caused by the rapid down-chirp, and the use of gases such as nitrogen to cause variation in the shape of the collisional broadened absorption lines.

  15. Temperature measurements of micro-droplets using pulsed 2-color laser-induced fluorescence with MDR-enhanced energy transfer

    NASA Astrophysics Data System (ADS)

    Palmer, Johannes; Reddemann, Manuel A.; Kirsch, Valeri; Kneer, Reinhold

    2016-12-01

    In this work, a new measurement system is presented for studying temperature of micro-droplets by pulsed 2-color laser-induced fluorescence. Pulsed fluorescence excitation allows motion blur suppression and thus simultaneous measurements of droplet size, velocity and temperature. However, high excitation intensities of pulsed lasers lead to morphology-dependent resonances inside micro-droplets, which are accompanied by disruptive stimulated emission. Investigations showed that stimulated emission can be avoided by enhanced energy transfer via an additional dye. The suitability and accuracy of the new pulsed method are verified on the basis of a spectroscopic analysis and comparison to continuously excited 2-color laser-induced fluorescence.

  16. Effects of frame rate and image resolution on pulse rate measured using multiple camera imaging photoplethysmography

    NASA Astrophysics Data System (ADS)

    Blackford, Ethan B.; Estepp, Justin R.

    2015-03-01

    Non-contact, imaging photoplethysmography uses cameras to facilitate measurements including pulse rate, pulse rate variability, respiration rate, and blood perfusion by measuring characteristic changes in light absorption at the skin's surface resulting from changes in blood volume in the superficial microvasculature. Several factors may affect the accuracy of the physiological measurement including imager frame rate, resolution, compression, lighting conditions, image background, participant skin tone, and participant motion. Before this method can gain wider use outside basic research settings, its constraints and capabilities must be well understood. Recently, we presented a novel approach utilizing a synchronized, nine-camera, semicircular array backed by measurement of an electrocardiogram and fingertip reflectance photoplethysmogram. Twenty-five individuals participated in six, five-minute, controlled head motion artifact trials in front of a black and dynamic color backdrop. Increasing the input channel space for blind source separation using the camera array was effective in mitigating error from head motion artifact. Herein we present the effects of lower frame rates at 60 and 30 (reduced from 120) frames per second and reduced image resolution at 329x246 pixels (one-quarter of the original 658x492 pixel resolution) using bilinear and zero-order downsampling. This is the first time these factors have been examined for a multiple imager array and align well with previous findings utilizing a single imager. Examining windowed pulse rates, there is little observable difference in mean absolute error or error distributions resulting from reduced frame rates or image resolution, thus lowering requirements for systems measuring pulse rate over sufficient length time windows.

  17. 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

  18. Measurement of optical path length change following pulsed laser irradiation using differential phase optical coherence tomography.

    PubMed

    Kim, Jihoon; Oh, Junghwan; Milner, Thomas E

    2006-01-01

    Differential phase optical coherence tomography (DPOCT) is introduced to measure optical path length changes in response to pulsed laser irradiation (585 nm). An analytical equation that includes thermoelastic surface displacement and thermorefractive index change is derived to predict optical path length change in response to pulsed laser irradiation for both "confined surface" and "free surface" model systems. The derived equation is tested by comparing predicted values with data recorded from experiments using two model systems. Thermorefractive index change and the thermal expansion coefficient are deduced from differential phase change (dDeltaphi) and temperature increase (DeltaT0) measurements. The measured n(T0)beta(T0)+dndT[=1.7410(-4)+/-1.710(-6) (1K)] in the free surface experiment matches with the National Institute of Standards and Technology (NIST) data value [=1.7710(-4) (1K)]. Exclusion of lateral thermal expansion in the analytical model for the confined surface experiment causes difference between the measured dndT[=-2.310(-4)+/-7.310(-6)(1K)] and the NIST value [=-9.4510(-5) (1K)]. In spite of the difference in the confined surface experiment, results of our studies indicate DPOCT can detect dynamic optical path length change in response to pulsed laser irradiation with high sensitivity, and applications to tissue diagnostics may be possible.

  19. Alternate dual pulses technique for fiber Bragg grating Ultra-multi-point strain measurement

    NASA Astrophysics Data System (ADS)

    Gong, Xin; Hua, Dengxin; Zhang, Pengbo; Hu, Liaolin; Wang, Yufeng

    2013-01-01

    The research of ultra-multi-point strain detection is one of the important topics at the forefront of optical fiber sensing technology. A newly ultra-multi-point strain measurement system was designed based on optical time-domain reflectometry (OTDR) and Fiber Bragg Grating. Two distributed feedback (DFB) lasers is proposed as laser source to generate the alternately pulsed light, and transmitted to a serial of fiber Bragg gratings with the same low-reflectivity and bandwidth. By the means of the strength of each reflectance spectrum and its return time of signals, the magnitude and location of strain can be accurately determined, and the numerical simulation shows that more than 1000 FBGs can be multiplexed in OTDR-FBG strain measurement system for a larger strain measurement range. Furthermore, the corresponding driving circuits for nanosecond pulse and temperature control circuits are designed for laser pulse modulation and frequency stabilization control. A OTDR-FBG strain measurement system is developed by using 10 FBGs with the reflectivity of less than 5%, and the system distance resolution of 43 cm is obtained, which verified the feasibility of the system.

  20. Species and temperature measurements of methane oxidation in a nanosecond repetitively pulsed discharge

    PubMed Central

    Lefkowitz, Joseph K; Guo, Peng; Rousso, Aric; Ju, Yiguang

    2015-01-01

    Speciation and temperature measurements of methane oxidation during a nanosecond repetitively pulsed discharge in a low-temperature flow reactor have been performed. Measurements of temperature and formaldehyde during a burst of pulses were made on a time-dependent basis using tunable diode laser absorption spectroscopy, and measurements of all other major stable species were made downstream of a continuously pulsed discharge using gas chromatography. The major species for a stoichiometric methane/oxygen/helium mixture with 75% dilution are H2O, CO, CO2, H2, CH2O, CH3OH, C2H6, C2H4 and C2H2. A modelling tool to simulate homogeneous plasma combustion kinetics is assembled by combining the ZDPlasKin and CHEMKIN codes. In addition, a kinetic model for plasma-assisted combustion (HP-Mech/plasma) of methane, oxygen and helium mixtures has been assembled to simulate the measurements. Predictions can accurately capture reactant consumption as well as production of the major product species. However, significant disagreement is found for minor species, particularly CH2O and CH3OH. Further analysis revealed that the plasma-activated low-temperature oxidation pathways, particularly those involving CH3O2 radical reactions and methane reactions with O(1D), are responsible for this disagreement. PMID:26170433

  1. Practical issues in ultrashort-laser-pulse measurement using frequency-resolved optical gating

    SciTech Connect

    DeLong, K.W.; Fittinghoff, D.N.; Trebino, R.

    1996-07-01

    The authors explore several practical experimental issues in measuring ultrashort laser pulses using the technique of frequency-resolved optical gating (FROG). They present a simple method for checking the consistency of experimentally measured FROG data with the independently measured spectrum and autocorrelation of the pulse. This method is a powerful way of discovering systematic errors in FROG experiments. They show how to determine the optimum sampling rate for FROG and show that this satisfies the Nyquist criterion for the laser pulse. They explore the low- and high-power limits to FROG and determine that femtojoule operation should be possible, while the effects of self-phase modulation limit the highest signal efficiency in FROG to 1%. They also show quantitatively that the temporal blurring due to a finite-thickness medium in single-shot geometries does not strongly limit the FROG technique. They explore the limiting time-bandwidth values that can be represented on a FROG trace of a given size. Finally, they report on a new measure of the FROG error that improves convergence in the presence of noise.

  2. Pressure and Thrust Measurements of a High-Frequency Pulsed Detonation Tube

    NASA Technical Reports Server (NTRS)

    Nguyen, N.; Cutler, A. D.

    2008-01-01

    This paper describes measurements of a small-scale, high-frequency pulsed detonation tube. The device utilized a mixture of H2 fuel and air, which was injected into the device at frequencies of up to 1200 Hz. Pulsed detonations were demonstrated in an 8-inch long combustion volume, at about 600 Hz, for the quarter wave mode of resonance. The primary objective of this experiment was to measure the generated thrust. A mean value of thrust was measured up to 6.0 lb, corresponding to H2 flow based specific impulse of 2970 s. This value is comparable to measurements in H2-fueled pulsed detonation engines (PDEs). The injection and detonation frequency for this new experimental case was much higher than typical PDEs, where frequencies are usually less than 100 Hz. The compact size of the device and high frequency of detonation yields a thrust-per-unit-volume of approximately 2.0 pounds per cubic inch, and compares favorably with other experiments, which typically have thrust-per-unit-volume of order 0.01 pound per cubic inch. This much higher volumetric efficiency results in a potentially much more practical device than the typical PDE, for a wide range of potential applications, including high-speed boundary layer separation control, for example in hypersonic engine inlets, and propulsion for small aircraft and missiles.

  3. Experimental study on double-pulse laser ablation of steel upon multiple parallel-polarized ultrashort-pulse irradiations

    NASA Astrophysics Data System (ADS)

    Schille, Joerg; Schneider, Lutz; Kraft, Sebastian; Hartwig, Lars; Loeschner, Udo

    2016-07-01

    In this paper, double-pulse laser processing is experimentally studied with the aim to explore the influence of ultrashort pulses with very short time intervals on ablation efficiency and quality. For this, sequences of 50 double pulses of varied energy and inter-pulse delay, as adjusted between 400 fs and 18 ns by splitting the laser beam into two optical paths of different length, were irradiated to technical-grade stainless steel. The depth and the volume of the craters produced were measured in order to evaluate the efficiency of the ablation process; the crater quality was analyzed by SEM micrographs. The results obtained were compared with craters produced with sequences of 50 single pulses and energies equal to the double pulse. It is demonstrated that double-pulse processing cannot exceed the ablation efficiency of single pulses of optimal fluence, but the ablation crater surface formed smoother if inter-pulse delay was in the range between 10 ns and 18 ns. In addition, the influence of pulse duration and energy distribution between the individual pulses of the double pulse on ablation was studied. For very short inter-pulse delay, no significant effect of energy variation within the double pulse on removal rate was found, indicating that the double pulse acts as a big single pulse of equal energy. Further, the higher removal efficiency was achieved when double-pulse processing using femtosecond pulses instead of picosecond pulses.

  4. Internal Magnetic Field, Temperature and Density Measurements on Magnetized HED plasmas using Pulsed Polarimetry

    SciTech Connect

    Smith, Roger J.

    2016-10-20

    The goals were to collaborate with the MSX project and make the MSX platform reliable with a performance where pulsed polarimetry would be capable of adding a useful measurement and then to achieve a first measurement using pulsed polarimetry. The MSX platform (outside of laser blow off plasmas adjacent to magnetic fields which are low beta) is the only device that can generate high beta magnetized collisionless supercritical shocks, and with a large spatial size of ~10 cm. Creating shocks at high Mach numbers and investigating the dynamics of the shocks was the main goal of the project. The MSX shocks scale to astrophysical magnetized shocks and potentially throw light on the generation of highly energetic particles via a mechanism like the Fermi process.

  5. Measurement of positive direct current corona pulse in coaxial wire-cylinder gap

    SciTech Connect

    Yin, Han Zhang, Bo He, Jinliang Wang, Wenzhuo

    2014-03-15

    In this paper, a system is designed and developed to measure the positive corona current in coaxial wire-cylinder gaps. The characteristic parameters of corona current pulses, such as the amplitude, rise time, half-wave time, and repetition frequency, are statistically analyzed and a new set of empirical formulas are derived by numerical fitting. The influence of space charges on corona currents is tested by using three corona cages with different radii. A numerical method is used to solve a simplified ion-flow model to explain the influence of space charges. Based on the statistical results, a stochastic model is developed to simulate the corona pulse trains. And this model is verified by comparing the simulated frequency-domain responses with the measured ones.

  6. Pulse wave transit time measured by imaging photoplethysmography in upper extremities

    NASA Astrophysics Data System (ADS)

    Volynsky, M. A.; Mamontov, O. V.; Sidorov, I. S.; Kamshilin, A. A.

    2016-08-01

    We describe highly reliable measurement method of the pulse wave transit time (PWTT) to human limbs by using simultaneous recordings of imaging photoplethysmography and electrocardiography. High accuracy of measurements was achieved by access to a larger number of statistically independent data obtained simultaneously in different points. The method is characterized by higher diagnostic reliability because of automatic selection of the regions less affected by environmental noise. The technique was tested in the group of 12 young healthy subjects aged from 21 to 33 years. Even though PWTT in right and left hands was comparable after averaging over the whole group of subjects, significant difference in the time delay of pulse wave between the hands was found in several individuals. The technique can be used for early-stage diagnostics of various vascular diseases.

  7. Pulsed excitation system to measure the resonant frequency of magnetoelastic biosensors

    NASA Astrophysics Data System (ADS)

    Xie, Hong; Chai, Yating; Horikawa, Shin; Wikle, Howard C.; Chin, Bryan A.

    2014-05-01

    An electrical circuit was designed and tested to measure the resonant frequency of micron-scale magnetoelastic (ME) biosensors using a pulsed wave excitation technique. In this circuit, a square pulse current is applied to an excitation coil to excite the vibration of ME biosensors and a pick-up coil is used to sense the ME biosensor's mechanical vibration and convert it to an electrical output signal. The output signal is filtered and amplified by a custom designed circuit to allow the measurement of the resonant frequency of the ME biosensor from which the detection of specific pathogens can be made. As a proof-in-concept experiment, JRB7 phage-coated ME biosensors were used to detect different concentrations of Bacillus anthracis Sterne strain spores. A statistically significant difference was observed for concentrations of 5 × 102 spore/ml and above.

  8. Double-Pulse Two-Micron IPDA Lidar Simulation for Airborne Carbon Dioxide Measurements

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta

    2015-01-01

    An advanced double-pulsed 2-micron integrated path differential absorption lidar has been developed at NASA Langley Research Center for measuring atmospheric carbon dioxide. The instrument utilizes a state-of-the-art 2-micron laser transmitter with tunable on-line wavelength and advanced receiver. Instrument modeling and airborne simulations are presented in this paper. Focusing on random errors, results demonstrate instrument capabilities of performing precise carbon dioxide differential optical depth measurement with less than 3% random error for single-shot operation from up to 11 km altitude. This study is useful for defining CO2 measurement weighting, instrument setting, validation and sensitivity trade-offs.

  9. High resolution magnetostriction measurements in pulsed magnetic fields using fiber Bragg gratings.

    PubMed

    Daou, Ramzy; Weickert, Franziska; Nicklas, Michael; Steglich, Frank; Haase, Ariane; Doerr, Mathias

    2010-03-01

    We report on a new high resolution apparatus for measuring magnetostriction suitable for use at cryogenic temperatures in pulsed high magnetic fields which we have developed at the Hochfeld-Magnetlabor Dresden. Optical fiber strain gauges based on fiber Bragg gratings are used to measure the strain in small (approximately 1 mm) samples. We describe the implementation of a fast measurement system capable of resolving strains in the order of 10(-7) with a full bandwidth of 47 kHz, and demonstrate its use on single crystal samples of GdSb and GdSi.

  10. LASER BIOLOGY AND MEDICINE: Arterial pulse shape measurement using self-mixing effect in a diode laser

    NASA Astrophysics Data System (ADS)

    Hast, J.; Myllylä, Risto; Sorvoja, H.; Miettinen, J.

    2002-11-01

    The self-mixing effect in a diode laser and the Doppler technique are used for quantitative measurements of the cardiovascular pulses from radial arteries of human individuals. 738 cardiovascular pulses from 10 healthy volunteers were studied. The Doppler spectrograms reconstructed from the Doppler signal, which is measured from the radial displacement of the radial artery, are compared to the first derivative of the blood pressure signals measured from the middle finger by the Penaz technique. The mean correlation coefficient between the Doppler spectrograms and the first derivative of the blood pressure signals was 0.84, with a standard deviation of 0.05. Pulses with the correlation coefficient less than 0.7 were neglected in the study. Percentage of successfully detected pulses was 95.7%. It is shown that cardiovascular pulse shape from the radial artery can be measured noninvasively by using the self-mixing interferometry.

  11. Characterization of a pulsed x-ray source for fluorescent lifetime measurements

    NASA Astrophysics Data System (ADS)

    Blankespoor, S. C.; Derenzo, S. E.; Moses, W. W.; Rossington, C. S.; Ito, M.; Oba, K.

    1994-08-01

    To search for new, fast, inorganic scintillators, we have developed a bench-top pulsed x-ray source for determining fluorescent lifetimes and wavelengths of compounds in crystal or powdered form. This source uses a light-excited x-ray tube which produces x-rays when light from a laser diode strikes its photocathode. The x-ray tube has a tungsten anode, a beryllium exit window, a 30 kV maximum tube bias, and a 50 mu A maximum average cathode current. The laser produces 3 x 10(sup 7) photons at 650 nm per approximately 100 ps pulse, with up to 10(sup 7) pulses/sec. The time spread for the laser diode, x-ray tube, and a microchannel plate photomultiplier tube is less than 120 ps fwhm. The mean x-ray energy at tube biases of 20, 25, and 30 kV is 9.4, 10.3, and 11.1 keV, respectively. We measured 140, 230, and 330 x-ray photons per laser diode pulse per steradian, at tube biases of 20, 25, and 30 kV, respectively. Background x-rays due to dark current occur at a rate of 1 x 10(sup 6) and 3 x 10(sup 6) photons/sec/steradian at biases of 25 and 30 kV, respectively. Data characterizing the x-ray output with an aluminum filter in the x-ray beam are also presented.

  12. Multi-Axis Thrust Measurements of the EO-1 Pulsed Plasma Thruster

    NASA Technical Reports Server (NTRS)

    Arrington, Lynn A.; Haag, Thomas W.

    1999-01-01

    Pulsed plasma thrusters are low thrust propulsive devices which have a high specific impulse at low power. A pulsed plasma thruster is currently scheduled to fly as an experiment on NASA's Earth Observing-1 satellite mission. The pulsed plasma thruster will be used to replace one of the reaction wheels. As part of the qualification testing of the thruster it is necessary to determine the nominal thrust as a function of charge energy. These data will be used to determine control algorithms. Testing was first completed on a breadboard pulsed plasma thruster to determine nominal or primary axis thrust and associated propellant mass consumption as a function of energy and then later to determine if any significant off-axis thrust component existed. On conclusion that there was a significant off-axis thrust component with the bread-board in the direction of the anode electrode, the test matrix was expanded on the flight hardware to include thrust measurements along all three orthogonal axes. Similar off-axis components were found with the flight unit.

  13. Retarding field energy analyzer for high energy pulsed electron beam measurements

    NASA Astrophysics Data System (ADS)

    Hu, Jing; Rovey, Joshua L.; Zhao, Wansheng

    2017-01-01

    A retarding field energy analyzer (RFEA) designed specifically for high energy pulsed electron beam measurements is described in this work. By proper design of the entrance grid, attenuation grid, and beam collector, this RFEA is capable of determining the time-resolved energy distribution of high energy pulsed electron beams normally generated under "soft vacuum" environment. The performance of the RFEA is validated by multiple tests of the leakage current, attenuation coefficient, and response time. The test results show that the retarding potential in the RFEA can go up to the same voltage as the electron beam source, which is 20 kV for the maximum in this work. Additionally, an attenuation coefficient of 4.2 is obtained in the RFEA while the percent difference of the rise time of the electron beam pulse before and after attenuation is lower than 10%. When compared with a reference source, the percent difference of the RFEA response time is less than 10% for fall times greater than 35 ns. Finally, the test results of the 10 kV pseudospark-based pulsed electron beam currents collected under varying retarding potentials are presented in this paper.

  14. Pulse Oximetry

    MedlinePlus

    ... www.thoracic.org amount of gases (oxygen and carbon dioxide) that are in your blood. To get ... Also, a pulse oximeter does not measure your carbon dioxide level. How accurate is the pulse oximeter? ...

  15. Plasma Sheet Velocity Measurement Techniques for the Pulsed Plasma Thruster SIMP-LEX

    NASA Technical Reports Server (NTRS)

    Nawaz, Anuscheh; Lau, Matthew

    2011-01-01

    The velocity of the first plasma sheet was determined between the electrodes of a pulsed plasma thruster using three measurement techniques: time of flight probe, high speed camera and magnetic field probe. Further, for time of flight probe and magnetic field probe, it was possible to determine the velocity distribution along the electrodes, as the plasma sheet is accelerated. The results from all three techniques are shown, and are compared for one thruster geometry.

  16. Frequency-resolved optical-gating measurements of ultrashort pulses using surface third-harmonic generation

    SciTech Connect

    Tsang, T.; Krumbuegel, M.A.; DeLong, K.W.; Fittinghoff, D.N.; Trebino, R.

    1996-09-01

    We demonstrate what is to our knowledge the first frequency-resolved optical gating (FROG) technique to measure ultrashort pulses from an unamplified Ti:sapphire laser oscillator without direction-of-time ambiguity. This technique utilizes surface third-harmonic generation as the nonlinear-optical effect and, surprisingly, is the most sensitive third-order FROG geometry yet. {copyright} {ital 1996 Optical Society of America.}

  17. Motion artefact reduction of the photoplethysmographic signal in pulse transit time measurement.

    PubMed

    Foo, J Y A; Wilson, S J; Williams, G R; Harris, M; Cooper, D M

    2004-12-01

    Motion artefact is a common occurrence that contaminates photoplethysmographic (PPG) measurements. To extract timing information from signals during artefact is challenging. PPG signal is very sensitive to artefacts and can be used in applications like, pulse transit time (PTT) as part of the polysomnographic studies. A correlation cancellation or signal processing approach is implemented with the adaptive cancelling filter concept and a triaxial accelerometry. PPG signals obtained from a Masimo (Reference) pulse oximeter is used as reference to compare with the reconstructed PPG signals. Different hands are used for each PPG source, one stationary while the other involves typical movements during sleep. A second Masimo pulse oximeter is used to register intensity of timing errors on commercial PPG signals. 108 PTT measurements are recorded in three different movements with PTT estimates from unprocessed PPG signals showing 35.51+/-27.42%, Masimo 50.02+/-29.40% and reconstructed 4.32+/-3.59% difference against those from the Reference PPG. The triaxial accelerometry can be used to detect the presence of artefact on PPG signals. This is useful in PTT measurements when signal contaminated with artefacts are required for further analysis, especially after and during arousals in sleep. The suggested filtering model can then reconstruct these corrupted PPG signals.

  18. Pulse transit time as a surrogate measure of changes in systolic arterial pressure in children during sleep.

    PubMed

    Vlahandonis, Anna; Biggs, Sarah N; Nixon, Gillian M; Davey, Margot J; Walter, Lisa M; Horne, Rosemary S C

    2014-08-01

    Pulse transit time has been proposed as a surrogate measure of systolic arterial pressure, as it is dependent upon arterial stiffness. Past research has shown that pulse transit time has a significant inverse relationship to systolic arterial pressure in adults; however, studies in children are limited. This study aimed to explore the relationship between systolic arterial pressure and pulse transit time in children during sleep. Twenty-five children (13.1 ± 1.6 years, 48% male) underwent overnight polysomnography (PSG) with a simultaneous recording of continuous systolic arterial pressure and photoplethysmography. Pulse transit time was calculated as the time delay between the R-wave peak of the electrocardiogram (ECG) to the 50% point of the upstroke of the corresponding photoplethysmography waveform; 500 beats of simultaneous systolic arterial pressure and pulse transit time were analysed in each sleep stage for each child. Pulse transit time was normalized to each subject's mean wake pulse transit time. The ability of pulse transit time to predict systolic arterial pressure change was determined by linear mixed-effects modelling. Significant negative correlations between pulse transit time and systolic arterial pressure were found for individual children for each sleep stage [mean correlations for cohort: non-rapid eye movement (NREM) sleep 1 and 2 r = -0.57, slow wave sleep (SWS) r = -0.76, REM r = -0.65, P < 0.01 for all]. Linear mixed-model analysis demonstrated that changes in pulse transit time were a significant predictor of changes in systolic arterial pressure for each sleep stage (P < 0.001). The model of pulse transit time-predicted systolic arterial pressure closely tracked actual systolic arterial pressure changes over time. This study demonstrated that pulse transit time was accurate in tracking systolic arterial pressure changes over time. Thus, the use of pulse transit time as a surrogate measure of changes in systolic arterial pressure in

  19. 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

  20. A new method for measurement of pulse wave velocity in arterial wall

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoming; Kinnick, Randall R.; Fatemi, Mostafa; Greenleaf, James F.

    2003-10-01

    Arterial wall stiffness can be associated with various diseases. The stiffness of an artery can be assessed by measurement of the pulse wave velocity (PWV). PWV is directly related to the Youngs modulus by the well-known Moens-Korteweg equation. Usually, PWV is estimated using the foot-to-foot method. However, the foot of the pressure wave is not very clear due to reflected waves. Also, the pressure wave is normally at a low frequency, hence, the time resolution is low. PWV is an average indicator of artery stiffness between the two measuring points, therefore it is not easy to identify local stiffness. We propose producing a very short pulse wave in the arterial wall using ultrasound radiation force and measuring its propagation speed along the artery by laser. The temporal resolution of this method is in the range of microseconds, which allows PWV to be measured accurately over a few millimeters. Experiments were carried out on a silicone tube in gelatin. PWV was measured by two scanning methods: (1) fixed source and scanning detector, (2) scanning source and fixed detector. Results: PWV was measured at 2 mm/40 μs by both methods. The Doppler technique was also tested which is potentially suitable for clinical applications.

  1. Envelope pulsed ultrasonic distance measurement system based upon amplitude modulation and phase modulation

    SciTech Connect

    Huang, Y. P.; Wang, J. S.; Huang, K. N.; Ho, C. T.; Huang, J. D.; Young, M. S.

    2007-06-15

    A novel microcomputer-based ultrasonic distance measurement system is presented. This study proposes an efficient algorithm which combines both the amplitude modulation (AM) and the phase modulation (PM) of the pulse-echo technique. The proposed system can reduce error caused by inertia delay and amplitude attenuation effect when using the AM and PM envelope square wave form (APESW). The APESW ultrasonic driving wave form causes a phase inversion phenomenon in the relative wave form of the receiver. The phase inversion phenomenon sufficiently identifies the ''measurement pulse'' in the received wave forms, which can be used for accurate time-of-flight (TOF) measurement. In addition, combining a countertechnique to compute the phase shifts of the last cycle for TOF, the presented system can obtain distance resolution of 0.1% of the wavelength corresponding to the 40 kHz frequency of the ultrasonic wave. The standard uncertainty of the proposed distance measurement system is found to be 0.2 mm at a range of 50-500 mm. The APESW signal generator and phase detector of this measuring system are designed on a complex programmable logic device, which is used to govern the TOF measurement and send the data to a personal computer for distance calibration and examination. The main advantages of this APESW system are high resolution, low cost, narrow bandwidth requirement, and ease of implementation.

  2. Integrated digital holography for measuring the photothermal effect induced by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Zhu, Linwei; Sun, Meiyu; Chen, Jiannong; Yu, Junjie; Zhou, Changhe

    2014-11-01

    Thermal lens (TL) and thermal mirror (TM) effects have been widely used for measuring the thermo-optical properties in materials. However, most previous research is not a direct two-dimensional measurement of the phase difference induced by photothermal effects, and the TL and TM effects cannot be measured simultaneously. We present an integrated digital holography (IDH) for measuring photothermal effects induced by femtosecond laser pulses with the laser excitation fluence below the ablation threshold. The photothermal effects of a metal sample induced by femtosecond laser pulses are studied. Our theoretical analysis reveals that when the energy of the femtosecond laser is below the ablation threshold, the theory of heat conduction and thermoelasticity can be used to explain the TL and TM effects caused by the laser-induced nonuniform temperature distribution. The experimental results show that both the nanoscale surface deformation of the TM effect and the refraction index change of the TL effect can be measured simultaneously by using the IDH. This IDH setup could be suitable for measuring the optical and thermal properties of materials.

  3. Envelope pulsed ultrasonic distance measurement system based upon amplitude modulation and phase modulation.

    PubMed

    Huang, Y P; Wang, J S; Huang, K N; Ho, C T; Huang, J D; Young, M S

    2007-06-01

    A novel microcomputer-based ultrasonic distance measurement system is presented. This study proposes an efficient algorithm which combines both the amplitude modulation (AM) and the phase modulation (PM) of the pulse-echo technique. The proposed system can reduce error caused by inertia delay and amplitude attenuation effect when using the AM and PM envelope square wave form (APESW). The APESW ultrasonic driving wave form causes a phase inversion phenomenon in the relative wave form of the receiver. The phase inversion phenomenon sufficiently identifies the "measurement pulse" in the received wave forms, which can be used for accurate time-of-flight (TOF) measurement. In addition, combining a countertechnique to compute the phase shifts of the last cycle for TOF, the presented system can obtain distance resolution of 0.1% of the wavelength corresponding to the 40 kHz frequency of the ultrasonic wave. The standard uncertainty of the proposed distance measurement system is found to be 0.2 mm at a range of 50-500 mm. The APESW signal generator and phase detector of this measuring system are designed on a complex programmable logic device, which is used to govern the TOF measurement and send the data to a personal computer for distance calibration and examination. The main advantages of this APESW system are high resolution, low cost, narrow bandwidth requirement, and ease of implementation.

  4. Attosecond streaking measurement of extreme ultraviolet pulses using a long-wavelength electric field

    PubMed Central

    Saito, Nariyuki; Ishii, Nobuhisa; Kanai, Teruto; Watanabe, Shuntaro; Itatani, Jiro

    2016-01-01

    Long-wavelength lasers have great potential to become a new-generation drive laser for tabletop coherent light sources in the soft X-ray region. Because of the significantly low conversion efficiency from a long-wavelength light field to high-order harmonics, their pulse characterization has been carried out by measuring the carrier-envelope phase and/or spatial dependences of high harmonic spectra. However, these photon detection schemes, in general, have difficulty in obtaining information on the spectral phases, which is crucial to determine the temporal structures of high-order harmonics. Here, we report the first attosecond streaking measurement of high harmonics generated by few-cycle optical pulses at 1.7 μm from a BiB3O6–based optical parametric chirped-pulse amplifier. This is also the first demonstration of time-resolved photoelectron spectroscopy using high harmonics from a long-wavelength drive laser other than Ti:sapphire lasers, which paves the way towards ultrafast soft X-ray photoelectron spectroscopy. PMID:27752115

  5. Curling probe measurement of large-volume pulsed plasma confined by surface magnetic field

    NASA Astrophysics Data System (ADS)

    Pandey, Anil; Sakakibara, Wataru; Matsuoka, Hiroyuki; Nakamura, Keiji; Sugai, Hideo; Chubu University Team; DOWA Thermotech Collaboration

    2015-09-01

    Curling probe (CP) has recently been developed which enables the local electron density measurement even in plasma for non-conducting film CVD. The electron density is obtained from a shift of resonance frequency of spiral antenna in discharge ON and OFF monitored by a network analyzer (NWA). In case of a pulsed glow discharge, synchronization of discharge pulse with frequency sweep of NWA must be established. In this paper, we report time and space-resolved CP measurement of electron density in a large volume plasma (80 cm diameter, 110 cm length) confined by surface magnetic field (multipole cusp field ~0.03 T). For plasma-aided modification of metal surface, the plasma is produced by 1 kV glow discharge at pulse frequency of 0.3 - 25 kHz with various duty ratio in gas (Ar, N2, C2H2) at pressure ~ 1 Pa. A radially movable CP revealed a remarkable effect of surface magnetic confinement: detach of plasma from the vessel wall and a fairly uniform plasma in the central region. In afterglow phase, the electron density was observed to decrease much faster in C2H2 discharge than in Ar discharge.

  6. Interferences in and lifetime measurement of a resonance electronic Raman effect using tunable pulsed laser techniques

    NASA Astrophysics Data System (ADS)

    Nicollin, D.; Koningstein, J. A.

    1980-07-01

    The excitation profile for the intensity of electronic Raman transitions of terbium aluminum garnet (TbAlG) in the spectral range of 483.0-680.0 nm is reported. The electronic Raman transitions take place between the crystal field levels of the split 7F 6 ground manifold of TbAlG with shifts of 73 cm -1 and 83 cm -1 and the electronic Raman process is induced with tunable pulsed and fixed wavelength cw lasers. The tunability of the former was employed to obtain detailed information of the behaviour of the Raman intensity if the wavelength of the exciting source is tuned throughout the region of 483.0-490.0 nm where 5Da 4 ← 7F 6 absorptions of TbAlG occur and the data reveal the occurrence of interference effects. We also report measurements of the shape of the pulse — due to resonance enhanced electronic Raman scattered light — in real time. These studies reveal that the lifetime of the resonating state (which is responsible for the enhancement of the Raman intensity) as determined from the tailing end of the said pulse is within experimental error equal to the lifetime τ = 33.5 ± 1 μs of this state measured in a direct way from the intensity decay of an appropriate fluorescence transition of TbAlG.

  7. A microNewton thrust stand for average thrust measurement of pulsed microthruster.

    PubMed

    Zhou, Wei-Jing; Hong, Yan-Ji; Chang, Hao

    2013-12-01

    A torsional thrust stand has been developed for the study of the average thrust for microNewton pulsed thrusters. The main body of the thrust stand mainly consists of a torsional balance, a pair of flexural pivots, a capacitive displacement sensor, a calibration assembly, and an eddy current damper. The behavior of the stand was thoroughly studied. The principle of thrust measurement was analyzed. The average thrust is determined as a function of the average equilibrium angle displacement of the balance and the spring stiffness. The thrust stand has a load capacity up to 10 kg, and it can theoretically measure the force up to 609.6 μN with a resolution of 24.4 nN. The static calibrations were performed based on the calibration assembly composed of the multiturn coil and the permanent magnet. The calibration results demonstrated good repeatability (less than 0.68% FSO) and good linearity (less than 0.88% FSO). The assembly of the multiturn coil and the permanent magnet was also used as an exciter to simulate the microthruster to further research the performance of the thrust stand. Three sets of force pulses at 17, 33.5, and 55 Hz with the same amplitude and pulse width were tested. The repeatability error at each frequency was 7.04%, 1.78%, and 5.08%, respectively.

  8. Pressure and Thrust Measurements of a High-Frequency Pulsed-Detonation Actuator

    NASA Technical Reports Server (NTRS)

    Nguyen, Namtran C.; Cutler, Andrew D.

    2008-01-01

    This paper describes the development of a small-scale, high-frequency pulsed detonation actuator. The device utilized a fuel mixture of H2 and air, which was injected into the device at frequencies of up to 1200 Hz. Pulsed detonations were demonstrated in an 8-inch long combustion volume, at approx.600 Hz, for the lambda/4 mode. The primary objective of this experiment was to measure the generated thrust. A mean value of thrust was measured up to 6.0 lb, corresponding to specific impulse of 2611 s. This value is comparable to other H2-fueled pulsed detonation engines (PDEs) experiments. The injection and detonation frequency for this new experimental case was approx.600 Hz, and was much higher than typical PDEs, where frequencies are usually less than 100 Hz. The compact size of the model and high frequency of detonation yields a thrust-per-unit-volume of approximately 2.0 lb/cu in, and compares favorably with other experiments, which typically have thrust-per-unit-volume values of approximately 0.01 lb/cu in.

  9. Development of glucose measurement system based on pulsed laser-induced ultrasonic method

    NASA Astrophysics Data System (ADS)

    Ren, Zhong; Wan, Bin; Liu, Guodong; Xiong, Zhihua

    2016-09-01

    In this study, a kind of glucose measurement system based on pulsed-induced ultrasonic technique was established. In this system, the lateral detection mode was used, the Nd: YAG pumped optical parametric oscillator (OPO) pulsed laser was used as the excitation source, the high sensitivity ultrasonic transducer was used as the signal detector to capture the photoacoustic signals of the glucose. In the experiments, the real-time photoacoustic signals of glucose aqueous solutions with different concentrations were captured by ultrasonic transducer and digital oscilloscope. Moreover, the photoacoustic peak-to-peak values were gotten in the wavelength range from 1300nm to 2300nm. The characteristic absorption wavelengths of glucose were determined via the difference spectral method and second derivative method. In addition, the prediction models of predicting glucose concentrations were established via the multivariable linear regression algorithm and the optimal prediction model of corresponding optimal wavelengths. Results showed that the performance of the glucose system based on the pulsed-induced ultrasonic detection method was feasible. Therefore, the measurement scheme and prediction model have some potential value in the fields of non-invasive monitoring the concentration of the glucose gradient, especially in the food safety and biomedical fields.

  10. Pulse shape effects on the measurement of temperature using a Brillouin-based optical fiber sensor

    NASA Astrophysics Data System (ADS)

    Galindez, Carlos; Madruga, Francisco-Javier; Cobo, Adolfo; Conde, Olga; Lopez-Higuera, Jose-Miguel

    2007-04-01

    Distributed fiber sensing based on Brillouin gain scattering (BGS) principle is a useful way to develop devices capable to measure temperature or/and strain in optical fibers. New effects or technologies that could achieve a larger distance and/or a better spatial resolution are a topic of special interest in this fiber sensing area. The influence of the probe-pulse shape in the interaction between the pulsed light and the continuous wave laser in a pump-probe system is presented. The purpose of this study is to improve the spatial resolution of the measurement without losing stability in the BGS. Also it is showed how the backscattering Brillouin gain is affected by inducing variations on the final value of the BGS intensity; this effect is illustrated by using an experimental set up based on the Brillouin optical time-domain analysis (BOTDA). Theoretical analysis of the probe pulse in the Brillouin shift and intensity value using triangular, sinc and saw tooth shapes around the medium phonon life time (~10ns) are presented; as well as the experimental results and possible applications are explained.

  11. Automated measurement of the EUREKA EU213 excimer laser pulse-forming line

    NASA Astrophysics Data System (ADS)

    Boardman, Allan D.; Hodgson, Elizabeth M.; Spence, A. J.; Wilkins, M.; Wu, Jian; Ashton, J. A.

    1990-08-01

    This paper describes part of the EUREKA Eurolaser project EU213, to build an excimer laser. The emphasis is on control and monitoring systems. The performance of a test-bed laser built at Salford will be described. In the design discussed, two voltage components are generated separately and combined at the laser head to form a pumping pulse. A "magnetic switch" is used to isolate the two parts of the transmission line'. A theoretical analysis of the sustainer section of the line has been carried out and compared with measurements made using a dummy load in place of the laser head. A control system is discussed that is being developed to monitor the shape of each laser pulse at a high repetition rate. The control system is designed to protect the laser from damage. The construction of various conventional probes, and the progress towards various fibre probes will be reported with emphasis on measuring fast current pulses on the various parts of the line.

  12. Simple linear technique for the measurement of space-time coupling in ultrashort optical pulses.

    PubMed

    Dorrer, Christophe; Walmsley, Ian A

    2002-11-01

    We demonstrate a simple sensitive linear technique that quantifies the spatiotemporal coupling in the electric field of an ultrashort optical pulse. The space-time uniformity of the field can be determined with only time-stationary filters and square-law integrating detectors, even if it is impossible to measure the temporal electric field in this way. A degree of spatiotemporal uniformity is defined and can be used with the demonstrated diagnostic to quantify space-time coupling. Experimental measurements of space-time coupling due to linear and nonlinear focusing, refraction, and diffraction are presented.

  13. Airborne Measurements of Atmospheric Methane Column Abundance Made Using a Pulsed IPDA Lidar

    NASA Technical Reports Server (NTRS)

    Riris, Haris; Numata, Kenji; Li, Steve; Wu, Stewart; Ramanathan, Anamd; Dawsey, Martha; Mao, Jianping; Kawa, Randolph; Abshire, James B.

    2012-01-01

    We report airborne measurements of the column abundance of atmospheric methane made over an altitude range of 3-11 km using a direct detection IPDA lidar with a pulsed laser emitting at 1651 nm. The laser transmitter was a tunable, seeded optical parametric amplifier (OPA) pumped by a Nd:YAG laser and the receiver used a photomultiplier detector and photon counting electronics. The results follow the expected changes with aircraft altitude and the measured line shapes and optical depths show good agreement with theoretical calculations.

  14. Pulsed photothermal reflectance measurement of the thermal conductivity of sputtered aluminum nitride thin films

    SciTech Connect

    Zhao Yimin; Zhu Chunlin; Wang Sigen; Tian, J.Z.; Yang, D.J.; Chen, C.K.; Cheng Hao; Hing, Peter

    2004-10-15

    We report on measurements of the thermal conductivity of reactively sputtered aluminum nitride (AlN) thin films with different thickness, ranging from 100 nm to 1 {mu}m, on silicon substrates. The measurements were made at room temperature using the pulsed photothermal reflectance technique. The thermal conductivities of the sample are found to be significantly lower than the single-crystal bulk AlN and increase with an increasing thickness. The thermal resistance at the interface between the AlN film and the silicon substrate is found to be about 7-8x10{sup -8} m{sup 2} K/W.

  15. Development of time projection chamber for precise neutron lifetime measurement using pulsed cold neutron beams

    NASA Astrophysics Data System (ADS)

    Arimoto, Y.; Higashi, N.; Igarashi, Y.; Iwashita, Y.; Ino, T.; Katayama, R.; Kitaguchi, M.; Kitahara, R.; Matsumura, H.; Mishima, K.; Nagakura, N.; Oide, H.; Otono, H.; Sakakibara, R.; Shima, T.; Shimizu, H. M.; Sugino, T.; Sumi, N.; Sumino, H.; Taketani, K.; Tanaka, G.; Tanaka, M.; Tauchi, K.; Toyoda, A.; Tomita, T.; Yamada, T.; Yamashita, S.; Yokoyama, H.; Yoshioka, T.

    2015-11-01

    A new time projection chamber (TPC) was developed for neutron lifetime measurement using a pulsed cold neutron spallation source at the Japan Proton Accelerator Research Complex (J-PARC). Managing considerable background events from natural sources and the beam radioactivity is a challenging aspect of this measurement. To overcome this problem, the developed TPC has unprecedented features such as the use of polyether-ether-ketone plates in the support structure and internal surfaces covered with 6Li-enriched tiles to absorb outlier neutrons. In this paper, the design and performance of the new TPC are reported in detail.

  16. Measuring quantum coherence in bulk solids using dual phase-locked optical pulses

    PubMed Central

    Hayashi, Shingo; Kato, Keigo; Norimatsu, Katsura; Hada, Masaki; Kayanuma, Yosuke; Nakamura, Kazutaka G.

    2014-01-01

    Electronic and phonon coherence are usually measured in different ways because their time-scales are very different. In this paper we simultaneously measure the electronic and phonon coherence using the interference of the electron-phonon correlated states induced by two phase-locked optical pulses. Interferometric visibility showed that electronic coherence remained in a semiconducting GaAs crystal until ~40 fs; in contrast, electronic coherence disappeared within 10 fs in a semimetallic Bi crystal at room temperature, differing substantially from the long damping time of its phonon coherence, in the picosecond range. PMID:24662682

  17. Application of a pulsed laser for measurements of bathymetry and algal fluorescence.

    NASA Technical Reports Server (NTRS)

    Hickman, G. D.; Hogg, J. E.; Friedman, E. J.; Ghovanlou, A. H.

    1973-01-01

    The technique of measuring water depths with an airborne pulsed dye laser is studied, with emphasis on the degrading effect of some environmental and operational parameters on the transmitted and reflected laser signals. Extrapolation of measurements of laser stimulated fluorescence, performed as a function of both the algal cell concentration and the distance between the algae and the laser/receiver, indicate that a laser system operating from a height of 500 m should be capable of detecting chlorophyll concentrations as low as 1.0 mg/cu m.-

  18. Phase effects due to previous pulses in time-resolved Faraday rotation measurements

    SciTech Connect

    Trowbridge, Christopher J.; Sih, Vanessa

    2015-02-14

    Time-resolved Faraday rotation measurements have proved transformative in the investigation of spin dynamics in semiconductors. In materials with spin lifetimes which are on the order of, or greater than, the laser repetition time, the collective effect of spin polarization due to the whole pump pulse train becomes important. Here, we discuss a relative phase shift which results from these spins. We derive and experimentally validate a closed-form expression which describes this phase shift and characterize it throughout parameter space. A spin lifetime measurement based on this phase shift is described, and we discuss situations in which the model used must be augmented to be applicable.

  19. Noncontact single-pulse optical method to measure interfacial properties in intact systems.

    PubMed

    Clark, David C; Kim, Myung K

    2012-12-15

    We introduce a noncontact purely optical approach to measuring the localized surface properties of an interface within a system using a single optical pressure pulse and a time-resolved digital holographic quantitative phase-imaging technique to track the propagating nanometric capillary disturbance. We demonstrate the proposed method's ability to measure the surface energy of deionized water, methanol, and chemical monolayers formed by surfactants with good agreement to published values. The development of this technique boasts immediate application to static and dynamic systems and near-future applications for living biological cell membranes.

  20. A short-pulse K(a)-band instrumentation radar for foliage attenuation measurements.

    PubMed

    Puranen, Mikko; Eskelinen, Pekka

    2008-10-01

    A portable K(a)-band instrumentation radar for foliage attenuation measurements has been designed. It uses direct dielectric resonator oscillator multiplier pulse modulation giving a half power pulse width of 17 ns. The dual conversion scalar receiver utilizes either a digital storage oscilloscope in envelope detection format or a special gated comparator arrangement providing 1 m resolution and associated led seven segment display for data analysis. The calibrated dynamic range is better than 37 dB with an equivalent noise floor of 0.005 dBsm at 25 m test range distance. First experiments indicate an effective beamwidth close to 1 degree. The total weight is below 5 kg and the unit can be mounted on a conventional photographic tripod. Power is supplied from a 12 V/6 A h sealed lead acid battery giving an operating time in excess of 10 h.