Why shorter half-times of repair lead to greater damage in pulsed brachytherapy

International Nuclear Information System (INIS)

Fowler, J.F.

1993-01-01

Pulsed brachytherapy consists of replacing continuous irradiation at low dose-rate with a series of medium dose-rate fractions in the same overall time and to the same total dose. For example, pulses of 1 Gy given every 2 hr or 2 Gy given every 4 hr would deliver the same 70 Gy in 140 hr as continuous irradiation at 0.5 Gy/hr. If higher dose-rates are used, even with gaps between the pulses, the biological effects are always greater. Provided that dose rates in the pulse do not exceed 3 Gy/hr, and provided that pulses are given as often as every 2 hr, the inevitable increases of biological effect are no larger than a few percent (of biologically effective dose or extrapolated response dose). However, these increases are more likely to exceed 10% (and thus become clinically significant) if the half-time of repair of sublethal damage is short (less than 1 hr) rather than long. This somewhat unexpected finding is explained in detail here. The rise and fall of Biologically Effective Dose (and hence of Relative Effectiveness, for a constant dose in each pulse) is calculated during and after single pulses, assuming a range of values of T 1/2 , the half-time of sublethal damage repair. The area under each curve is proportional to Biologically Effective Dose and therefore to log cell kill. Pulses at 3 Gy/hr do yield greater biological effect (dose x integrated Relative Effectiveness) than lower dose-rate pulses or continuous irradiation at 0.5 Gy/hr. The contrast is greater for the short T 1/2 of 0.5 hr than for the longer T 1/2 of 1.5 hr. More biological damage will be done (compared with traditional low dose rate brachytherapy) in tissues with short T 1/2 (0.1-1 hr) than in tissues with longer T 1/2 values. 8 refs., 3 figs

A nanosecond high voltage pulse device for accelerator time analytical system

International Nuclear Information System (INIS)

Lou Binqiao; Ding Furong; Xue Zhihua; Wang Xuemei; Shen Dingyu

2002-01-01

A nanosecond high voltage pulse device has been designed. The pulse rise time is 10 ns. The pulse voltage reached 16000 V. This device has been used to accelerator time analytical system, its resolution time is less than 0.8%

HPGe detectors timing using pulse shape analysis techniques

International Nuclear Information System (INIS)

Crespi, F.C.L.; Vandone, V.; Brambilla, S.; Camera, F.; Million, B.; Riboldi, S.; Wieland, O.

2010-01-01

In this work the Pulse Shape Analysis has been used to improve the time resolution of High Purity Germanium (HPGe) detectors. A set of time aligned signals was acquired in a coincidence measurement using a coaxial HPGe and a cerium-doped lanthanum chloride (LaCl 3 :Ce) scintillation detector. The analysis using a Constant Fraction Discriminator (CFD) time output versus the HPGe signal shape shows that time resolution ranges from 2 to 12 ns depending on the slope in the initial part of the signal. An optimization procedure of the CFD parameters gives the same final time resolution (8 ns) as the one achieved after a correction of the CFD output based on the current pulse maximum position. Finally, an algorithm based on Pulse Shape Analysis was applied to the experimental data and a time resolution between 3 and 4 ns was obtained, corresponding to a 50% improvement as compared with that given by standard CFDs.

Pulse Compression of Phase-matched High Harmonic Pulses from a Time-Delay Compensated Monochromator

Directory of Open Access Journals (Sweden)

Ito Motohiko

2013-03-01

Full Text Available Pulse compression of single 32.6-eV high harmonic pulses from a time-delay compensated monochromator was demonstrated down to 11±3 fs by compensating the pulse front tilt. The photon flux was intensified up to 5.7×109 photons/s on target by implementing high harmonic generation under a phase matching condition in a hollow fiber used for increasing the interaction length.

Structure analysis of liquids and disordered materials using pulsed neutron diffraction and total scattering

International Nuclear Information System (INIS)

Suzuya, Kentaro

2011-01-01

Neutron diffraction·total scattering at pulsed neutron source is a powerful method to analyze the complex structure of disordered materials: liquids, glasses, amorphous materials and disordered crystals. The basic idea of the structure of disordered materials, the fundamental diffraction theory for disordered materials, and structure analysis of disordered materials using pulsed neutron diffraction·total scattering technique (TOF method) are described in detail. In addition, the precise information of the world highest class J-PARC MLF spallation neutron source and typical J-PARC neutron total scattering instrument NOVA are also given. Recent structural modelling methods of disordered materials such like reverse Monte Carlo (RMC) simulation method is briefly described using an example of the analysis of a typical disordered material silica glass. (author)

Time-lens based optical packet pulse compression and retiming

DEFF Research Database (Denmark)

Laguardia Areal, Janaina; Hu, Hao; Palushani, Evarist

2010-01-01

recovery, resulting in a potentially very efficient solution. The scheme uses a time-lens, implemented through a sinusoidally driven optical phase modulation, combined with a linear dispersion element. As time-lenses are also used for pulse compression, we design the circuit also to perform pulse...

Active cancellation - A means to zero dead-time pulse EPR.

Science.gov (United States)

Franck, John M; Barnes, Ryan P; Keller, Timothy J; Kaufmann, Thomas; Han, Songi

2015-12-01

The necessary resonator employed in pulse electron paramagnetic resonance (EPR) rings after the excitation pulse and creates a finite detector dead-time that ultimately prevents the detection of signal from fast relaxing spin systems, hindering the application of pulse EPR to room temperature measurements of interesting chemical or biological systems. We employ a recently available high bandwidth arbitrary waveform generator (AWG) to produce a cancellation pulse that precisely destructively interferes with the resonant cavity ring-down. We find that we can faithfully detect EPR signal at all times immediately after, as well as during, the excitation pulse. This is a proof of concept study showcasing the capability of AWG pulses to precisely cancel out the resonator ring-down, and allow for the detection of EPR signal during the pulse itself, as well as the dead-time of the resonator. However, the applicability of this approach to conventional EPR experiments is not immediate, as it hinges on either (1) the availability of low-noise microwave sources and amplifiers to produce the necessary power for pulse EPR experiment or (2) the availability of very high conversion factor micro coil resonators that allow for pulse EPR experiments at modest microwave power. Copyright © 2015 Elsevier Inc. All rights reserved.

Time dependent theory of two-step absorption of two pulses

Energy Technology Data Exchange (ETDEWEB)

Rebane, Inna, E-mail: inna.rebane@ut.ee

2015-09-25

The time dependent theory of two step-absorption of two different light pulses with arbitrary duration in the electronic three-level model is proposed. The probability that the third level is excited at the moment t is found in depending on the time delay between pulses, the spectral widths of the pulses and the energy relaxation constants of the excited electronic levels. The time dependent perturbation theory is applied without using “doorway–window” approach. The time and spectral behavior of the spectrum using in calculations as simple as possible model is analyzed. - Highlights: • Time dependent theory of two-step absorption in the three-level model is proposed. • Two different light pulses with arbitrary duration is observed. • The time dependent perturbation theory is applied without “door–window” approach. • The time and spectral behavior of the spectra is analyzed for several cases.

Real-time multiparameter pulse processing with decision tables

International Nuclear Information System (INIS)

Hull, K.; Griffin, H.

1986-01-01

Decision tables offer several advantages over other real-time multiparameter, data processing techniques. These include very high collection rates, minimum number of computer instructions, rates independent of the number of conditions applied per parameter, ease of adding or removing conditions during a session, and simplicity of implementation. Decisions table processing is important in multiparameter nuclear spectroscopy, coincidence experiments, multiparameter pulse processing (HgI 2 resolution enhancement, pulse discrimination, timing spectroscopy), and other applications can be easily implemented. (orig.)

Time dependent temperature distribution in pulsed Ti:sapphire lasers

Science.gov (United States)

Buoncristiani, A. Martin; Byvik, Charles E.; Farrukh, Usamah O.

1988-01-01

An expression is derived for the time dependent temperature distribution in a finite solid state laser rod for an end-pumped beam of arbitrary shape. The specific case of end pumping by circular (constant) or Gaussian beam is described. The temperature profile for a single pump pulse and for repetitive pulse operation is discussed. The particular case of the temperature distribution in a pulsed titanium:sapphire rod is considered.

Development of a fast rise-time, high-voltage pulse generator

International Nuclear Information System (INIS)

Zhang Yanxia; Zhu Jie; Li Xianyou

2006-01-01

In order to test the attenuation of the system, a fast rise-time, high-voltage pulse generator is required for the fast pulse signal measurement. The paper presents the development of the generator. More emphasis is paid on the discussion of the difficulties occurring in the circuit debugging and their resolutions. The output rise-time of the generator is 700 ps, the amplitude is adjustable in the range of 0 to 500 V, the pulse-width is adjustable in the range of 4ns to 1μs. (authors)

Optimal Linear Filters. 2. Pulse Time Measurements in the Presence of Noise

Energy Technology Data Exchange (ETDEWEB)

Nygaard, K

1966-09-15

The problem of calculating the maximum available timing information contained in nuclear pulses in the presence of noise is solved theoretically. Practical experiments show that the theoretical values can be obtained by very simple, but untraditional, means. An output pulse from a practical filter connected to a charge sensitive amplifier with a Ge(Li) detector showed a rise time of 30 ns and a noise level of less than 5 keV. The time jitter measured was inversely proportional to the pulse height and less than 30 ns for 10 keV pulses. With the timing filter shown solid state detectors can be classified somewhere between Nal scintillators and organic scintillators with respect to time resolution.

Optimal Linear Filters. 2. Pulse Time Measurements in the Presence of Noise

International Nuclear Information System (INIS)

Nygaard, K.

1966-09-01

The problem of calculating the maximum available timing information contained in nuclear pulses in the presence of noise is solved theoretically. Practical experiments show that the theoretical values can be obtained by very simple, but untraditional, means. An output pulse from a practical filter connected to a charge sensitive amplifier with a Ge(Li) detector showed a rise time of 30 ns and a noise level of less than 5 keV. The time jitter measured was inversely proportional to the pulse height and less than 30 ns for 10 keV pulses. With the timing filter shown solid state detectors can be classified somewhere between Nal scintillators and organic scintillators with respect to time resolution

Subnanosecond-rise-time, low-impedance pulse generator

International Nuclear Information System (INIS)

Druce, R.; Vogtlin, G.

1983-01-01

This paper describes a fast rise, low-impedance pulse generator that has been developed at the Lawrence Livermore National Laboratory. The design specifications of this generator are: 50-kV operating voltage, 1-ohm output impedance, subnanosecond rise time, and a 2 to 10 nanosecond pulse length. High repetition rate is not required. The design chosen is a parallel-plate, folded Blumlein generator. A tack switch is utilized for its simple construction and high performance. The primary diagnostic is a capacitive voltage divider with a B probe used to measure the current waveform

Subnanosecond-rise-time, low-impedance pulse generator

Energy Technology Data Exchange (ETDEWEB)

Druce, R.; Vogtlin, G.

1983-06-03

This paper describes a fast rise, low-impedance pulse generator that has been developed at the Lawrence Livermore National Laboratory. The design specifications of this generator are: 50-kV operating voltage, 1-ohm output impedance, subnanosecond rise time, and a 2 to 10 nanosecond pulse length. High repetition rate is not required. The design chosen is a parallel-plate, folded Blumlein generator. A tack switch is utilized for its simple construction and high performance. The primary diagnostic is a capacitive voltage divider with a B probe used to measure the current waveform.

Subnanosecond-rise-time, low-impedance pulse generator

Science.gov (United States)

Druce, R.; Vigtlin, G.

1983-06-01

A fast rise, low impedance pulse generator developed at the Lawrence Livermore National Laboratory is described. The design specifications of this generator are: 50-kV operating voltage, 1-ohm output impedance, subnanosecond rise time, and a 2 to 10 nanosecond pulse length. High repetition rate is not required. The design chosen is a parallel plate, folded Blumlein generator. A tack switch is utilized for its simple construction and high performance. The primary diagnostic is a capacitive voltage divider with a B probe used to measure the current waveform.

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-05-01

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

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

Science.gov (United States)

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

2017-05-01

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

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

International Nuclear Information System (INIS)

Ren Changliang; Hofmann, Holger F.

2011-01-01

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

Ablation of silicon with bursts of femtosecond laser pulses

Science.gov (United States)

Gaudiuso, Caterina; Kämmer, Helena; Dreisow, Felix; Ancona, Antonio; Tünnermann, Andreas; Nolte, Stefan

2016-03-01

We report on an experimental investigation of ultrafast laser ablation of silicon with bursts of pulses. The pristine 1030nm-wavelength 200-fs pulses were split into bursts of up to 16 sub-pulses with time separation ranging from 0.5ps to 4080ps. The total ablation threshold fluence was measured depending on the burst features, finding that it strongly increases with the number of sub-pulses for longer sub-pulse delays, while a slowly increasing trend is observed for shorter separation time. The ablation depth per burst follows two different trends according to the time separation between the sub-pulses, as well as the total threshold fluence. For delays shorter than 4ps it decreases with the number of pulses, while for time separations longer than 510ps, deeper craters were achieved by increasing the number of subpulses in the burst, probably due to a change of the effective penetration depth.

Physical model of reactor pulse

International Nuclear Information System (INIS)

Petrovic, A.; Ravnik, M.

2004-01-01

Pulse experiments have been performed at J. Stefan Institute TRIGA reactor since 1991. In total, more than 130 pulses have been performed. Extensive experimental information on the pulse physical characteristics has been accumulated. Fuchs-Hansen adiabatic model has been used for predicting and analysing the pulse parameters. The model is based on point kinetics equation, neglecting the delayed neutrons and assuming constant inserted reactivity in form of step function. Deficiencies of the Fuchs-Hansen model and systematic experimental errors have been observed and analysed. Recently, the pulse model was improved by including the delayed neutrons and time dependence of inserted reactivity. The results explain the observed non-linearity of the pulse energy for high pulses due to finite time of pulse rod withdrawal and the contribution of the delayed neutrons after the prompt part of the pulse. The results of the improved model are in good agreement with experimental results. (author)

Long Pulse Integrator of Variable Integral Time Constant

International Nuclear Information System (INIS)

Wang Yong; Ji Zhenshan; Du Xiaoying; Wu Yichun; Li Shi; Luo Jiarong

2010-01-01

A kind of new long pulse integrator was designed based on the method of variable integral time constant and deducting integral drift by drift slope. The integral time constant can be changed by choosing different integral resistors, in order to improve the signal-to-noise ratio, and avoid output saturation; the slope of integral drift of a certain period of time can be calculated by digital signal processing, which can be used to deduct the drift of original integral signal in real time to reduce the integral drift. The tests show that this kind of long pulse integrator is good at reducing integral drift, which also can eliminate the effects of changing integral time constant. According to experiments, the integral time constant can be changed by remote control and manual adjustment of integral drift is avoided, which can improve the experiment efficiency greatly and can be used for electromagnetic measurement in Tokamak experiment. (authors)

Time derived sigma for pulsed neutron capture logging

International Nuclear Information System (INIS)

Randall, R.R.; Fertl, W.F.; Hopkinson, E.C.

1981-01-01

The purpose of this study is to review field applications of the Atlas Neutron Lifetime Log service and to examine recent technical advances in the instrumentation and data analysis system. The major improvement to be discussed is a new method for computing /SIGMA/, the thermal neutron capture cross section of an earth formation. In the new method, the time after the neutron burst is measured for each gamma ray pulse detected by the instrumentation system within a gate of fixed width. This ''average pulse time'' is uniquely related to the thermal neutron decay rate observed in a borehole environment. The technique discussed is applicable for any condition where the neutron or gamma ray flux is time dependent. The advantages of this signal processing method, however, are most apparent for cases of rapid flux change with time, as in an exponential decay. 7 refs

Electromagnetic pulses, localized and causal

Science.gov (United States)

Lekner, John

2018-01-01

We show that pulse solutions of the wave equation can be expressed as time Fourier superpositions of scalar monochromatic beam wave functions (solutions of the Helmholtz equation). This formulation is shown to be equivalent to Bateman's integral expression for solutions of the wave equation, for axially symmetric solutions. A closed-form one-parameter solution of the wave equation, containing no backward-propagating parts, is constructed from a beam which is the tight-focus limit of two families of beams. Application is made to transverse electric and transverse magnetic pulses, with evaluation of the energy, momentum and angular momentum for a pulse based on the general localized and causal form. Such pulses can be represented as superpositions of photons. Explicit total energy and total momentum values are given for the one-parameter closed-form pulse.

The use of joint time frequency analysis to quantify the effect of ventilation on the pulse oximeter waveform.

Science.gov (United States)

Shelley, Kirk H; Awad, Aymen A; Stout, Robert G; Silverman, David G

2006-04-01

In the process of determining oxygen saturation, the pulse oximeter functions as a photoelectric plethysmograph. By analyzing how the frequency spectrum of the pulse oximeter waveform changes over time, new clinically relevant features can be extracted. Thirty patients undergoing general anesthesia for abdominal surgery had their pulse oximeter, airway pressure and CO(2) waveforms collected (50 Hz). The pulse oximeter waveform was analyzed with a short-time Fourier transform using a moving 4096 point Hann window of 82 seconds duration. The frequency signal created by positive pressure ventilation was extracted using a peak detection algorithm in the frequency range of ventilation (0.08-0.4 Hz = 5-24 breaths/minute). The respiratory rate derived in this manner was compared to the respiratory rate as determined by CO(2) detection. In total, 52 hours of telemetry data were analyzed. The respiratory rate measured from the pulse oximeter waveform was found to have a 0.89 linear correlation when compared to CO(2) detection and airway pressure change. the bias was 0.03 breath/min, SD was 0.557 breath/min and the upper and lower limits of agreement were 1.145 and -1.083 breath/min respectively. The presence of motion artifact proved to be the primary cause of failure of this technique. Joint time frequency analysis of the pulse oximeter waveform can be used to determine the respiratory rate of ventilated patients and to quantify the impact of ventilation on the waveform. In addition, when applied to the pulse oximeter waveform new clinically relevant features were observed.

Real-time evolvable pulse shaper for radiation measurements

Energy Technology Data Exchange (ETDEWEB)

Lanchares, Juan, E-mail: julandan@dacya.ucm.es [Facultad de Informática, Universidad Complutense de Madrid (UCM), C/Prof. José García Santesmases s/n, 28040 Madrid (Spain); Garnica, Oscar, E-mail: ogarnica@dacya.ucm.es [Facultad de Informática, Universidad Complutense de Madrid (UCM), C/Prof. José García Santesmases s/n, 28040 Madrid (Spain); Risco-Martín, José L., E-mail: jlrisco@dacya.ucm.es [Facultad de Informática, Universidad Complutense de Madrid (UCM), C/Prof. José García Santesmases s/n, 28040 Madrid (Spain); Ignacio Hidalgo, J., E-mail: hidalgo@dacya.ucm.es [Facultad de Informática, Universidad Complutense de Madrid (UCM), C/Prof. José García Santesmases s/n, 28040 Madrid (Spain); Regadío, Alberto, E-mail: alberto.regadio@insa.es [Área de Tecnologías Electrónicas, Instituto Nacional de Técnica Aeroespacial (INTA), 28850 Torrejón de Ardoz, Madrid (Spain)

2013-11-01

In the last two decades, recursive algorithms for real-time digital pulse shaping in pulse height measurements have been developed and published in number of articles and textbooks. All these algorithms try to synthesize in real time optimum or near optimum shapes in the presence of noise. Even though some of these shapers can be considered effective designs, some side effects like aging cannot be ignored. We may observe that after sensors degradation, the signal obtained is not valid. In this regard, we present in this paper a novel technique that, based on evolvable hardware concepts, is able to evolve the degenerated shaper into a new design with better performance than the original one under the new sensor features.

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

Science.gov (United States)

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

1973-01-01

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

Time pulse profiles on a new data acquisition system for neutron time of flight diffractometer

International Nuclear Information System (INIS)

Venegas, R.; Baeza, L.; Navarro, G.

1999-01-01

A new differential acquisition system was built for a neutron diffuse scattering instrument. We analyze the time, space and velocity behavior of neutron pulse profiles, which can be obtained in a neutron diffuse scattering system of this nature, consisting of a black disc slit chopper and a circular detector bank, in order to design accurate scattering data analyzing methods. Computed direct pulse time spectra and measured spectra show satisfactory agreement. (author)

Time moments of the energy flow of optical pulses in highly dispersive media

International Nuclear Information System (INIS)

Nanda, Lipsa; Wanare, Harshawardhan; Ramakrishna, S Anantha

2010-01-01

We use the time moments of the Poynting vector associated with an electromagnetic pulse to characterize the traversal times and temporal pulse widths as the pulse propagates in highly dispersive media. The behaviour of these quantities with the propagation distance is analysed in three canonical cases: Lorentz absorptive medium, a Raman gain doublet amplifying medium and a medium exhibiting electromagnetically induced transparency. We find that superluminal pulse propagation in the first two cases with anomalous dispersion is usually accompanied by pulse compression and eventually the pulse becomes subluminal with increasing distance of propagation. In a medium with electromagnetically induced transparency with large normal dispersion, we identify a range of frequencies for which the pulse undergoes minimal temporal expansion while propagating with ultra-slow speed.

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

Energy Technology Data Exchange (ETDEWEB)

Cha, Byung Heon; Kim, S. G.; Nam, S. M.; Lee, B. C.; Lee, S. M.; Jeong, Y. U.; Cho, S. O.; Jin, J. T.; Choi, H. L

1998-01-01

The control circuit for high voltage switches, the saturable inductor for magnetic assist, and the magnetic pulse compression circuit were designed, constructed, and tested. The core materials of saturable inductors in magnetic pulse compression circuit were amorphous metal and ferrite and total compression stages were 3. By the test, in high repetition rate, high pulse compression were certified. As a result of this test, it became possible to increase life-time of thyratrons and to replace thyratrons by solid-state semiconductor switches. (author). 16 refs., 16 tabs.

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

International Nuclear Information System (INIS)

Cha, Byung Heon; Kim, S. G.; Nam, S. M.; Lee, B. C.; Lee, S. M.; Jeong, Y. U.; Cho, S. O.; Jin, J. T.; Choi, H. L.

1998-01-01

The control circuit for high voltage switches, the saturable inductor for magnetic assist, and the magnetic pulse compression circuit were designed, constructed, and tested. The core materials of saturable inductors in magnetic pulse compression circuit were amorphous metal and ferrite and total compression stages were 3. By the test, in high repetition rate, high pulse compression were certified. As a result of this test, it became possible to increase life-time of thyratrons and to replace thyratrons by solid-state semiconductor switches. (author). 16 refs., 16 tabs

Generation of fast-rise time, repetitive, (sub) nanosecond, high-voltage pulses

NARCIS (Netherlands)

Huiskamp, T.; Pemen, A.J.M.

2017-01-01

In this contribution we present our fast-rise time nanosecond pulse generator, capable of generating up to 50 kV (positive and negative) rectangular pulses at a repetition rate of up to 1 kHz and with a rise time of less than 200 picoseconds. We focus on the general concepts involved in the design

Time and Frequency Localized Pulse Shape for Resolution Enhancement in STFT-BOTDR

Directory of Open Access Journals (Sweden)

Linqing Luo

2016-01-01

Full Text Available Short-Time Fourier Transform-Brillouin Optical Time-Domain Reflectometry (STFT-BOTDR implements STFT over the full frequency spectrum to measure the distributed temperature and strain along the optic fiber, providing new research advances in dynamic distributed sensing. The spatial and frequency resolution of the dynamic sensing are limited by the Signal to Noise Ratio (SNR and the Time-Frequency (T-F localization of the input pulse shape. T-F localization is fundamentally important for the communication system, which suppresses interchannel interference (ICI and intersymbol interference (ISI to improve the transmission quality in multicarrier modulation (MCM. This paper demonstrates that the T-F localized input pulse shape can enhance the SNR and the spatial and frequency resolution in STFT-BOTDR. Simulation and experiments of T-F localized different pulses shapes are conducted to compare the limitation of the system resolution. The result indicates that rectangular pulse should be selected to optimize the spatial resolution and Lorentzian pulse could be chosen to optimize the frequency resolution, while Gaussian shape pulse can be used in general applications for its balanced performance in both spatial and frequency resolution. Meanwhile, T-F localization is proved to be useful in the pulse shape selection for system resolution optimization.

Design of a bolometer for total-energy measurement of the linear coherent light source pulsed X-ray laser

International Nuclear Information System (INIS)

Friedrich, S.; Li, L.; Ott, L.L.; Kolgani, Rajeswari M.; Yong, G.J.; Ali, Z.A.; Drury, O.B.; Ables, E.; Bionta, R.M.

2006-01-01

We are developing a cryogenic bolometer to measure the total energy of the linear coherent light source (LCLS) free electron X-ray laser to be built at the Stanford Linear Accelerator Center. The laser will produce ultrabright X-ray pulses in the energy range between 0.8 and 8 keV with ∼10 12 photons per ∼200 fs pulse at a repeat interval of 8 ms, and will be accompanied by a halo of spontaneous undulator radiation. The bolometer is designed to determine the total energy of each laser pulse to within (1- x ) Sr x MnO 3 sensor array at the metal-insulator transition, where the composition x is adjusted to produce the desired transition temperature. We discuss design considerations and material choices, and present numerical simulations of the thermal response

Nanosecond time-resolved EPR in pulse radiolysis via the spin echo method

International Nuclear Information System (INIS)

Trifunac, A.D.; Norris, J.R.; Lawler, R.G.

1979-01-01

The design and operation of a time-resolved electron spin echo spectrometer suitable for detecting transient radicals produced by 3 MeV electron radiolysis is described. Two modes of operation are available: Field swept mode which generates a normal EPR spectrum and kinetic mode in which the time dependence of a single EPR line is monitored. Techniques which may be used to minimize the effects of nonideal microwave pulses and overlapping sample tube signals are described. The principal advantages of the spin echo method over other time-resolved EPR methods are: (1) Improved time resolution (presently approx.30--50 nsec) allows monitoring of fast changes in EPR signals of transient radicals, (2) Lower susceptibility to interference between the EPR signal and the electron beam pulse at short times, and (3) Lack of dependence of transient signals on microwave field amplitude or static field inhomogeneity at short times. The performance of the instrument is illustrated using CIDEP from acetate radical formed in pulsed radiolysis of aqueous solutions of potassium acetate. The relaxation time and CIDEP enhancement factor obtained for this radical using the spin echo method compare favorably with previous determinations using direct detection EPR. Radical decay rates yield estimates of initial radical concentrations of 10 -4 10 -3 M per electron pulse. The Bloch equations are solved to give an expression for the echo signal for samples exhibiting CIDEP using arbitrary microwave pulse widths and distributions of Larmor frequencies. Conditions are discussed under which the time-dependent signal would be distorted by deviations from an ideal nonselective 90 0 --tau--180 0 pulse sequence

Programming for time resolved spectrum in pulse radiolysis experiments

International Nuclear Information System (INIS)

Betty, C.A.; Panajkar, M.S.; Shirke, N.D.

1993-01-01

A user friendly program in Pascal has been developed for data acquisition and subsequent processing of time resolved spectra of transient species produced in pulse radiolysis experiments. The salient features of the program are (i) thiocyanate dosimetry and (ii) spectrum acquisition. The thiocyanate dosimetry is carried out to normalize experimental conditions to a standard value as determined by computing absorbance of the transient signal CNS -2 that is produced from thiocyanate solution by a 7 MeV electron pulse. Spectrum acquisition allows the acquisition of the time resolved data at 20 different times points and subsequent display of the plots of absorbance vs. wavelength for the desired time points during the experiment. It is also possible to plot single time point spectrum as well as superimposed spectra for different time points. Printing, editing and merging facilities are also provided. (author). 2 refs., 7 figs

Molecular isomerization induced by ultrashort infrared pulses. II. Pump-dump isomerization using pairs of time-delayed half-cycle pulses.

Science.gov (United States)

Uiberacker, Christoph; Jakubetz, Werner

2004-06-22

We investigate population transfer across the barrier in a double-well potential, induced by a pair of time-delayed single-lobe half-cycle pulses. We apply this setup both to a one-dimensional (1D) quartic model potential and to a three-dimensional potential representing HCN-->HNC isomerization. Overall the results for the two systems are similar, although in the 3D system some additional features appear not seen in the 1D case. The generic mechanism of population transfer is the preparation by the pump pulse of a wave packet involving delocalized states above the barrier, followed by the essentially 1D motion of the delocalized part of wave packet across the barrier, and the eventual de-excitation by the dump pulse to localized states in the other well. The correct timing is given by the well-to-well passage time of the wave packet and its recurrence properties, and by the signs of the field lobes which determine the direction and acceleration or deceleration of the wave packet motion. In the 3D system an additional pump-pump-dump mechanism linked to wave packet motion in the reagent well can mediate isomerization. Since the transfer time and the pulse durations are of the same order of magnitude, there is also a marked dependence of the dynamics and the transfer yield on the pulse duration. Our analysis also sheds light on the pronounced carrier envelope phase dependence previously observed for isomerization and molecular dissociation with one-cycle and sub-one-cycle pulses. (c) 2004 American Institute of Physics.

Drilling of Copper Using a Dual-Pulse Femtosecond Laser

Directory of Open Access Journals (Sweden)

Chung-Wei Cheng

2016-02-01

Full Text Available The drilling of copper using a dual-pulse femtosecond laser with wavelength of 800 nm, pulse duration of 120 fs and a variable pulse separation time (0.1–150 ps is investigated theoretically. A one-dimensional two-temperature model with temperature-dependent material properties is considered, including dynamic optical properties and the thermal-physical properties. Rapid phase change and phase explosion models are incorporated to simulate the material ablation process. Numerical results show that under the same total laser fluence of 4 J/cm2, a dual-pulse femtosecond laser with a pulse separation time of 30–150 ps can increase the ablation depth, compared to the single pulse. The optimum pulse separation time is 85 ps. It is also demonstrated that a dual pulse with a suitable pulse separation time for different laser fluences can enhance the ablation rate by about 1.6 times.

Four-deep charge-time and pulse-width scaling discriminator for delay line MWPC's

International Nuclear Information System (INIS)

Lee, K.L.; Kirsten, F.A.; Grigorian, A.; Guiragossian, Z.G.T.

1976-01-01

A discriminator has been developed for digitizing both intercepted total charge and location of electromagnetic shower and particle trajectories in multi-wire proportional chambers read by delay lines. Determination of shower trajectory is aided by video signal integration followed by centroid-locating discrimination. Calibrated run-down of the signal integrating capacitor gives the charge information above a given threshold level. The discriminator is designed to handle up to four shower-induced video signals per event by incorporating steering circuits within the module. Each video signal is examined for time over an adjustable threshold. Video pulses with separation of less than 20 nsec are treated as a single pulse. Counter-logic circuits indicate the number of video signals digitized. These signal processing circuits provide a first level of data sifting which otherwise must be carried out with additional discriminator channels and added complexity in data recognition

Analytical modeling of pulse-pileup distortion using the true pulse shape; applications to Fermi-GBM

International Nuclear Information System (INIS)

Chaplin, Vandiver; Bhat, Narayana; Briggs, Michael S.; Connaughton, Valerie

2013-01-01

Pulse-pileup affects most photon counting systems and occurs when photon detections occur faster than the detector's shaping and recovery time. At high input rates, shaped pulses interfere and the source spectrum, as well as intensity information, get distorted. For instruments using bipolar pulse shaping there are two aspects to consider: ‘peak’ and ‘tail’ pileup effects, which raise and lower the measured energy, respectively. Peak effects have been extensively modeled in the past. Tail effects have garnered less attention due to increased complexity. We leverage previous work to derive an accurate, semi-analytical prediction for peak and tail pileup including high order effects. We use the pulse shape of the detectors of the Fermi Gamma-ray Burst Monitor. The measured spectrum is calculated by expressing exposure time with a state-space expansion of overlapping pileup states and is valid up to very high rates. The model correctly predicts deadtime and pileup losses, and energy-dependent losses due to tail subtraction (sub-threshold) effects. We discuss total losses in terms of the true rate of photon detections versus the recorded count rate. -- Highlights: • A derivation of pulse-pileup spectral and intensity distortion is presented. • Applies to bipolar shaping instruments in general, but is calculated for Fermi-GBM. • Exposure time is partitioned with pulse widths as states of a Poisson process. • Each state has an associated energy distribution function for peak and tail pileup. • The total spectrum is the union of pulse states and their associated spectra

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

Science.gov (United States)

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

2016-12-01

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

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

International Nuclear Information System (INIS)

André, Jean-Michel; Jonnard, Philippe

2015-01-01

The time-dependence of the Bragg diffraction by one-dimensional photonic crystals and its influence on the short pulse reflection are studied in the framework of the coupled-wave theory. The indicial response of the photonic crystal is calculated and it appears that it presents a time-delay effect with a transient time conditioned by the extinction length. A numerical simulation is presented for a Bragg mirror in the x-ray domain and a pulse envelope modelled by a sine-squared shape. The potential consequences of the time-delay effect in time-dependent optics of short-pulses are emphasized. (paper)

Time profiles and pulse structure of bright, long gamma-ray bursts using BATSE TTS data

International Nuclear Information System (INIS)

Lee, A.; Bloom, E.; Scargle, J.

1996-04-01

The time profiles of many gamma-ray bursts observed by BATSE consist of distinct pulses, which offer the possibility of characterizing the temporal structure of these bursts using a relatively small set of pulse-shape parameters. This pulse analysis has previously been performed on some bright, long bursts using binned data, and on some short bursts using BATSE Time-Tagged Event (TTE) data. The BATSE Time- to-Spill (TTS) burst data records the times required to accumulate a fixed number of photons, giving variable time resolution. The spill times recorded in the TTS data behave as a gamma distribution. We have developed an interactive pulse-fitting program using the pulse model of Norris et al. and a maximum-likelihood fitting algorithm to the gamma distribution of the spill times. We then used this program to analyze a number of bright, long bursts for which TTS data is available. We present statistical information on the attributes of pulses comprising these bursts

Key technology research of nuclear signal digitized pulse shaping in real time

International Nuclear Information System (INIS)

Zhou Jianbin; Wang Min; Zhou Wei; Zhu Xing; Liu Yi; Chen Bao; Lu Baoping; Yue Aizhong; Qin Li; He Xuxin

2014-01-01

The computer simulation and analysis were carried out for the ideal nuclear pulse signal and the actual detector output signals, and the determination method of digital trapezoidal shape parameter for different nuclear pulse shaping time was summarized. At high count rate measurement occasion, the effective count rate is increased, some pile-up pulses are eliminated and the accumulation of dead time of the system is reduced. Meanwhile, Si-PIN semiconductor detector performance was tested by 256 points and 512 points digital triangle forming methods and the analog circuit forming methods for comparative tests. Test results show that the pulse forming treatment method increases the count rate performance and the resolution of detector. (authors)

Modeling associations between latent event processes governing time series of pulsing hormones.

Science.gov (United States)

Liu, Huayu; Carlson, Nichole E; Grunwald, Gary K; Polotsky, Alex J

2017-10-31

This work is motivated by a desire to quantify relationships between two time series of pulsing hormone concentrations. The locations of pulses are not directly observed and may be considered latent event processes. The latent event processes of pulsing hormones are often associated. It is this joint relationship we model. Current approaches to jointly modeling pulsing hormone data generally assume that a pulse in one hormone is coupled with a pulse in another hormone (one-to-one association). However, pulse coupling is often imperfect. Existing joint models are not flexible enough for imperfect systems. In this article, we develop a more flexible class of pulse association models that incorporate parameters quantifying imperfect pulse associations. We propose a novel use of the Cox process model as a model of how pulse events co-occur in time. We embed the Cox process model into a hormone concentration model. Hormone concentration is the observed data. Spatial birth and death Markov chain Monte Carlo is used for estimation. Simulations show the joint model works well for quantifying both perfect and imperfect associations and offers estimation improvements over single hormone analyses. We apply this model to luteinizing hormone (LH) and follicle stimulating hormone (FSH), two reproductive hormones. Use of our joint model results in an ability to investigate novel hypotheses regarding associations between LH and FSH secretion in obese and non-obese women. © 2017, The International Biometric Society.

PENERAPAN PULSED ELECTRIC FIELD PADA PASTEURISASI SARI BUAH APEL VARIETAS ANA: KAJIAN KARAKTERISTIK NILAI GIZI, SIFAT FISIK, SIFAT KIMIAWI DAN MIKROBIA TOTAL Application of Pulsed Electric Field in Pasteurization of Apple Juice of Ana Cultivar : Study on

Directory of Open Access Journals (Sweden)

La Choviya Hawa

2012-05-01

Full Text Available Apple juice, extracted from apple of ana cultivar , was pasteurized using a pulsed electric field (PEF method. The aimof this research was to analyze the changes on nutritional, physical and chemical properties and total microbes from apple juice after pasteurization. The research was conducted from July until Oktober 2009 located in Malang. The PEF treatment was carried out using treatment time variation for 10, 20, 30, 40, 50 and 60 seconds. Several parameters of vitamin A and C, water content, density, pH, total soluable solid and total microbes were observed. The results showed that PEF treatment did not significantly change nutritional, physical and chemical properties and total microbes after pasteurization with PEF in compared with no treatment pasteurization. The highest degradation was found in treatment time for 60 seconds, i.e. 93.53 %. ABSTRAK Sari buah apel, yang diekstrak dari apel varietas ana, dipasteurisasi dengan metode pulsed electric field (PEF. Tujuanpenelitian ini adalah untuk mengetahui perubahan karakteristik nilai gizi, sifat fisik, kimiawi dan total mikrobia sari buah apel sesudah dipasteurisasi. Penelitian dilaksanakan bulan Juli sampai dengan Oktober 2009 di Malang. Penelitian ini menggunakan variasi waktu pengolahan 10, 20, 30, 40, 50 dan 60 detik. Parameter pengamatan yaitu vitamin A dan C, kadar air, berat jenis, pH, total padatan terlarut dan total mikrobia. Hasil penelitian menunjukkan bahwa nilai gizi, sifat fisik dan kimiawi dari sari apel  tidak mengalami perubahan signifikan dibandingkan sari apel tanpa perlakuan PEF. Penurunan total mikrobia terbesar pada waktu perlakuan 60 detik dengan efektivitas pembunuhan sebesar 93,53%.

In Vitro Comparison of Holmium Lasers: Evidence for Shorter Fragmentation Time and Decreased Retropulsion Using a Modern Variable-pulse Laser.

Science.gov (United States)

Bell, John Roger; Penniston, Kristina L; Nakada, Stephen Y

2017-09-01

To compare the performance of variable- and fixed-pulse lasers on stone phantoms in vitro. Seven-millimeter stone phantoms were made to simulate calcium oxalate monohydrate stones using BegoStone plus. The in vitro setting was created with a clear polyvinyl chloride tube. For each trial, a stone phantom was placed at the open end of the tubing. The Cook Rhapsody H-30 variable-pulse laser was tested on both long- and short-pulse settings and was compared to the Dornier H-20 fixed-pulse laser; 5 trials were conducted for each trial arm. Fragmentation was accomplished with the use of a flexible ureteroscope and a 273-micron holmium laser fiber using settings of 1 J × 12 Hz. The treatment time (in minute) for complete fragmentation was recorded as was the total retropulsion distance (in centimeter) during treatment. Laser fibers were standardized for all repetitions. The treatment time was significantly shorter with the H-30 vs the H-20 laser (14.3 ± 2.5 vs 33.1 ± 8.9 minutes, P = .008). There was no difference between the treatment times using the long vs short pulse widths of the H-30 laser (14.4 ± 3.4 vs 14.3 ± 1.7 minutes, P = .93). Retropulsion differed by laser type and pulse width, H-30 long pulse (15.8 ± 5.7 cm), H-30 short pulse (54.8 ± 7.1 cm), and H-20 (33.2 ± 12.5 cm) (P laser fragmented stone phantoms in half the time of the H-20 laser regardless of the pulse width. Retropulsion effects differed between the lasers, with the H-30 causing the least retropulsion. Longer pulse widths result in less stone retropulsion. Copyright © 2017 Elsevier Inc. All rights reserved.

Pulse pile-up. I: Short pulses

International Nuclear Information System (INIS)

Wilkinson, D.H.

1990-07-01

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

Time-resolved measurements with intense ultrashort laser pulses: a 'molecular movie' in real time

International Nuclear Information System (INIS)

Rudenko, A; Ergler, Th; Feuerstein, B; Zrost, K; Schroeter, C D; Moshammer, R; Ullrich, J

2007-01-01

We report on the high-resolution multidimensional real-time mapping of H 2 + and D 2 + nuclear wave packets performed employing time-resolved three-dimensional Coulomb explosion imaging with intense laser pulses. Exploiting a combination of a 'reaction microscope' spectrometer and a pump-probe setup with two intense 6-7 fs laser pulses, we simultaneously visualize both vibrational and rotational motion of the molecule, and obtain a sequence of snapshots of the squared ro-vibrational wave function with time-step resolution of ∼ 0.3 fs, allowing us to reconstruct a real-time movie of the ultrafast molecular motion. We observe fast dephasing, or 'collapse' of the vibrational wave packet and its subsequent revival, as well as signatures of rotational excitation. For D 2 + we resolve also the fractional revivals resulting from the interference between the counter-propagating parts of the wave packet

Biological effect of pulsed dose rate brachytherapy with stepping sources if short half-times of repair are present in tissues

International Nuclear Information System (INIS)

Fowler, Jack F.; Limbergen, Erik F.M. van

1997-01-01

Purpose: To explore the possible increase of radiation effect in tissues irradiated by pulsed brachytherapy (PDR) for local tissue dose rates between those 'averaged over the whole pulse' and the instantaneous high dose rates close to the dwell positions. Increased effect is more likely for tissues with short half-times of repair of the order of a few minutes, similar to pulse durations. Methods and Materials: Calculations were done assuming the linear quadratic formula for radiation damage, in which only the dose-squared term is subject to exponential repair. The situation with two components of T (1(2)) is addressed. A constant overall time of 140 h and a constant total dose of 70 Gy were assumed throughout, the continuous low dose rate of 0.5 Gy/h (CLDR) providing the unitary standard effects for each PDR condition. Effects of dose rates ranging from 4 Gy/h to 120 Gy/h (HDR at 2 Gy/min) were studied, covering the gap in an earlier publication. Four schedules were examined: doses per pulse of 0.5, 1, 1.5, and 2 Gy given at repetition frequencies of 1, 2, 3, and 4 h, respectively, each with a range of assumed half-times of repair of 4 min to 1.5 h. Results are presented for late-responding tissues, the differences from CLDR being two or three times greater than for early-responding tissues and most tumors. Results: Curves are presented relating the ratio of increased biological effect (proportional to log cell kill) calculated for PDR relative to CLDR. Ratios as high as 1.5 can be found for large doses per pulse (2 Gy) if the half-time of repair in tissues is as short as a few minutes. The major influences on effect are dose per pulse, half-time of repair in tissue, and--when T (1(2)) is short--the instantaneous dose rate. Maximum ratios of PDR/CLDR occur when the dose rate is such that pulse duration is approximately equal to T (1(2)) . As dose rate in the pulse is increased, a plateau of effect is reached, for most T (1(2)) s, above 10 to 20 Gy/h, which is

Optimal time-domain technique for pulse width modulation in power electronics

Directory of Open Access Journals (Sweden)

I. Mayergoyz

2018-05-01

Full Text Available Optimal time-domain technique for pulse width modulation is presented. It is based on exact and explicit analytical solutions for inverter circuits, obtained for any sequence of input voltage rectangular pulses. Two optimal criteria are discussed and illustrated by numerical examples.

Modular High Voltage Pulse Converter for Short Rise and Decay Times

NARCIS (Netherlands)

Mao, S.

2018-01-01

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

MR pulse sequences for selective relaxation time measurements: a phantom study

DEFF Research Database (Denmark)

Thomsen, C; Jensen, K E; Jensen, M

1990-01-01

a Siemens Magnetom wholebody magnetic resonance scanner operating at 1.5 Tesla was used. For comparison six imaging pulse sequences for relaxation time measurements were tested on the same phantom. The spectroscopic pulse sequences all had an accuracy better than 10% of the reference values....

Pulse shape analyzer/timing-SCA application to beta measurement

International Nuclear Information System (INIS)

Selvi, S.; Celiktas, C.

2001-01-01

Electrical noise contribution to pulse height distributions from beta sources due to BC-400 plastic scintillator(PS), preamplifier and spectroscopy amplifier was rejected by setting the electronic set-up processing of the modified beta spectrometer consisted of pulse shape analyzer/timing single channel analyzer (PSA/SCA) and related complementary equipments. Improved noise rejection performance was evaluated in terms of elimination practically only all of the noise band of C-14 and Tl-204 spectra obtained using the two alternate beta spectrometer

Comparison of power pulses from homogeneous and time-average-equivalent models

International Nuclear Information System (INIS)

De, T.K.; Rouben, B.

1995-01-01

The time-average-equivalent model is an 'instantaneous' core model designed to reproduce the same three dimensional power distribution as that generated by a time-average model. However it has been found that the time-average-equivalent model gives a full-core static void reactivity about 8% smaller than the time-average or homogeneous models. To investigate the consequences of this difference in static void reactivity in time dependent calculations, simulations of the power pulse following a hypothetical large-loss-of-coolant accident were performed with a homogeneous model and compared with the power pulse from the time-average-equivalent model. The results show that there is a much smaller difference in peak dynamic reactivity than in static void reactivity between the two models. This is attributed to the fact that voiding is not complete, but also to the retardation effect of the delayed-neutron precursors on the dynamic flux shape. The difference in peak reactivity between the models is 0.06 milli-k. The power pulses are essentially the same in the two models, because the delayed-neutron fraction in the time-average-equivalent model is lower than in the homogeneous model, which compensates for the lower void reactivity in the time-average-equivalent model. (author). 1 ref., 5 tabs., 9 figs

The Real-time Frequency Spectrum Analysis of Neutron Pulse Signal Series

International Nuclear Information System (INIS)

Tang Yuelin; Ren Yong; Wei Biao; Feng Peng; Mi Deling; Pan Yingjun; Li Jiansheng; Ye Cenming

2009-01-01

The frequency spectrum analysis of neutron pulse signal is a very important method in nuclear stochastic signal processing Focused on the special '0' and '1' of neutron pulse signal series, this paper proposes new rotation-table and realizes a real-time frequency spectrum algorithm under 1G Hz sample rate based on PC with add, address and SSE. The numerical experimental results show that under the count rate of 3X10 6 s -1 , this algorithm is superior to FFTW in time-consumption and can meet the real-time requirement of frequency spectrum analysis. (authors)

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

International Nuclear Information System (INIS)

Kyrala, G.A.

1987-01-01

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

An Algorithm for Real-Time Pulse Waveform Segmentation and Artifact Detection in Photoplethysmograms.

Science.gov (United States)

Fischer, Christoph; Domer, Benno; Wibmer, Thomas; Penzel, Thomas

2017-03-01

Photoplethysmography has been used in a wide range of medical devices for measuring oxygen saturation, cardiac output, assessing autonomic function, and detecting peripheral vascular disease. Artifacts can render the photoplethysmogram (PPG) useless. Thus, algorithms capable of identifying artifacts are critically important. However, the published PPG algorithms are limited in algorithm and study design. Therefore, the authors developed a novel embedded algorithm for real-time pulse waveform (PWF) segmentation and artifact detection based on a contour analysis in the time domain. This paper provides an overview about PWF and artifact classifications, presents the developed PWF analysis, and demonstrates the implementation on a 32-bit ARM core microcontroller. The PWF analysis was validated with data records from 63 subjects acquired in a sleep laboratory, ergometry laboratory, and intensive care unit in equal parts. The output of the algorithm was compared with harmonized experts' annotations of the PPG with a total duration of 31.5 h. The algorithm achieved a beat-to-beat comparison sensitivity of 99.6%, specificity of 90.5%, precision of 98.5%, and accuracy of 98.3%. The interrater agreement expressed as Cohen's kappa coefficient was 0.927 and as F-measure was 0.990. In conclusion, the PWF analysis seems to be a suitable method for PPG signal quality determination, real-time annotation, data compression, and calculation of additional pulse wave metrics such as amplitude, duration, and rise time.

Attosecond time-energy structure of X-ray free-electron laser pulses

Science.gov (United States)

Hartmann, N.; Hartmann, G.; Heider, R.; Wagner, M. S.; Ilchen, M.; Buck, J.; Lindahl, A. O.; Benko, C.; Grünert, J.; Krzywinski, J.; Liu, J.; Lutman, A. A.; Marinelli, A.; Maxwell, T.; Miahnahri, A. A.; Moeller, S. P.; Planas, M.; Robinson, J.; Kazansky, A. K.; Kabachnik, N. M.; Viefhaus, J.; Feurer, T.; Kienberger, R.; Coffee, R. N.; Helml, W.

2018-04-01

The time-energy information of ultrashort X-ray free-electron laser pulses generated by the Linac Coherent Light Source is measured with attosecond resolution via angular streaking of neon 1s photoelectrons. The X-ray pulses promote electrons from the neon core level into an ionization continuum, where they are dressed with the electric field of a circularly polarized infrared laser. This induces characteristic modulations of the resulting photoelectron energy and angular distribution. From these modulations we recover the single-shot attosecond intensity structure and chirp of arbitrary X-ray pulses based on self-amplified spontaneous emission, which have eluded direct measurement so far. We characterize individual attosecond pulses, including their instantaneous frequency, and identify double pulses with well-defined delays and spectral properties, thus paving the way for X-ray pump/X-ray probe attosecond free-electron laser science.

Electronic system for recording proportional counter rare pulses with the pulse shape analysis

International Nuclear Information System (INIS)

Barabanov, I.R.; Gavrin, V.N.; Zakharov, Yu.I.; Tikhonov, A.A.

1984-01-01

The anutomated system for recording proportional counter rare pulses is described. The proportional counters are aimed at identification of 37 Ar and H7 1 Gr decays in chemical radiation detectors of solar neutrino. Pulse shape recording by means of a storage oscilloscope and a TV display is performed in the system considered besides two-parametric selection of events (measurement of pulse amplitude in a slow channel and the amplitude of pulse differentiated with time constant of about 10 ns in a parallel fast channel). Pulse discrimination by a front rise rate provides background decrease in the 55 Fe range (5.9 keV) by 6 times; the visual analysis of pulse shapes recorded allows to decrease the background additionally by 25-30%. The background counting rate in the 55 Fe range being equal to 1 pulse per 1.5 days, is obtained when using the installation described above, as well as the passive Pb shield 5 cm thick, and the active shield based on the anticoincidence NaI(Tl) detector with the cathode 5.6 mm in-diameter made of Fe fabircated by zone melting. The installation described allows to reach the background level of 0.6 pulse/day (the total coefficient of background attenuation is 400). Further background decrease is supposed to be provided by installation allocation in the low-noise underground laboratory of the Baksan Neutrino Observatory

Time resolved Thomson scattering diagnostic of pulsed gas metal arc welding (GMAW) process

International Nuclear Information System (INIS)

Kühn-Kauffeldt, M; Schein, J; Marquès, J L

2014-01-01

In this work a Thomson scattering diagnostic technique was applied to obtain time resolved electron temperature and density values during a gas metal arc welding (GMAW) process. The investigated GMAW process was run with aluminum wire (AlMg 4,5 Mn) with 1.2 mm diameter as a wire electrode, argon as a shielding gas and peak currents in the range of 400 A. Time resolved measurements could be achieved by triggering the laser pulse at shifted time positions with respect to the current pulse driving the process. Time evaluation of resulting electron temperatures and densities is used to investigate the state of the plasma in different phases of the current pulse and to determine the influence of the metal vapor and droplets on the plasma properties

Design of a bolometer for total-energy measurement of the linear coherent light source pulsed X-ray laser

Energy Technology Data Exchange (ETDEWEB)

Friedrich, S. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore CA 94550 (United States)]. E-mail: Friedrich1@llnl.gov; Li, L. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore CA 94550 (United States); Ott, L.L. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore CA 94550 (United States); Kolgani, Rajeswari M. [Department of Physics, Geosciences and Astronomy, Towson University, 8000 York Avenue, Towson MD 21252 (United States); Yong, G.J. [Department of Physics, Geosciences and Astronomy, Towson University, 8000 York Avenue, Towson MD 21252 (United States); Ali, Z.A. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore CA 94550 (United States); Drury, O.B. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore CA 94550 (United States); Ables, E. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore CA 94550 (United States); Bionta, R.M. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore CA 94550 (United States)

2006-04-15

We are developing a cryogenic bolometer to measure the total energy of the linear coherent light source (LCLS) free electron X-ray laser to be built at the Stanford Linear Accelerator Center. The laser will produce ultrabright X-ray pulses in the energy range between 0.8 and 8 keV with {approx}10{sup 12} photons per {approx}200 fs pulse at a repeat interval of 8 ms, and will be accompanied by a halo of spontaneous undulator radiation. The bolometer is designed to determine the total energy of each laser pulse to within <0.1%, taking into account thermal and mechanical stress to prevent melting in the LCLS beam due to its high energy density. We propose to use a magnetoresistive Nd{sub (1-} {sub x} {sub )}Sr {sub x} MnO{sub 3} sensor array at the metal-insulator transition, where the composition x is adjusted to produce the desired transition temperature. We discuss design considerations and material choices, and present numerical simulations of the thermal response.

Effect of pulse lasting time of ion implantation on the growth of Hericium ernaceus

International Nuclear Information System (INIS)

Yan Tao; Li Guan; Zeng Xianxian

2007-01-01

Low energy ion implantation technology was used in mutation breeding of Hericium erinaceus. The growth speed of the Hericium erinaceus hypha is as an index to study the influence of the pulse lasting time of N + ion implantation. The result shows that the growth speed of Hericium erinaceus hypha presents 'saddle shape' curve, which was descend first, then rising up and descend again when the pulse time lasts for longer and longer. It is concluded that the pulse time obviously influence N + ion implantation. When the dosage keeps the same. (authors)

Digital synthesis of pulse shapes in real time for high resolution radiation spectroscopy

International Nuclear Information System (INIS)

Jordanov, Valentin T.; Knoll, Glenn F.

1994-01-01

Techniques have been developed for the synthesis of pulse shapes using fast digital schemes in place of the traditional analog methods of pulse shaping. Efficient recursive algorithms have been developed that allow real time implementation of a shaper that can produce either trapezoidal or triangular pulse shapes. Other recursive techniques are presented which allow a synthesis of finite cusp-like shapes. Preliminary experimental tests show potential advantages of using these techniques in high resolution, high count rate pulse spectroscopy. ((orig.))

On the Time Evolution of Gamma-Ray Burst Pulses: A Self-Consistent Description.

Science.gov (United States)

Ryde; Svensson

2000-01-20

For the first time, the consequences of combining two well-established empirical relations that describe different aspects of the spectral evolution of observed gamma-ray burst (GRB) pulses are explored. These empirical relations are (1) the hardness-intensity correlation and (2) the hardness-photon fluence correlation. From these we find a self-consistent, quantitative, and compact description for the temporal evolution of pulse decay phases within a GRB light curve. In particular, we show that in the case in which the two empirical relations are both valid, the instantaneous photon flux (intensity) must behave as 1&solm0;&parl0;1+t&solm0;tau&parr0;, where tau is a time constant that can be expressed in terms of the parameters of the two empirical relations. The time evolution is fully defined by two initial constants and two parameters. We study a complete sample of 83 bright GRB pulses observed by the Compton Gamma-Ray Observatory and identify a major subgroup of GRB pulses ( approximately 45%) which satisfy the spectral-temporal behavior described above. In particular, the decay phase follows a reciprocal law in time. It is unclear what physics causes such a decay phase.

Identification of fractional-order systems with time delays using block pulse functions

Science.gov (United States)

Tang, Yinggan; Li, Ning; Liu, Minmin; Lu, Yao; Wang, Weiwei

2017-07-01

In this paper, a novel method based on block pulse functions is proposed to identify continuous-time fractional-order systems with time delays. First, the operational matrices of block pulse functions for fractional integral operator and time delay operator are derived. Then, these operational matrices are applied to convert the continuous-time fractional-order systems with time delays to an algebraic equation. Finally, the system's parameters along with the differentiation orders and the time delays are all simultaneously estimated through minimizing a quadric error function. The proposed method reduces the computation complexity of the identification process, and also it does not require the system's differentiation orders to be commensurate. The effectiveness of the proposed method are demonstrated by several numerical examples.

Two-stage optical parametric chirped-pulse amplifier using sub-nanosecond pump pulse generated by stimulated Brillouin scattering compression

Science.gov (United States)

Ogino, Jumpei; Miyamoto, Sho; Matsuyama, Takahiro; Sueda, Keiichi; Yoshida, Hidetsugu; Tsubakimoto, Koji; Miyanaga, Noriaki

2014-12-01

We demonstrate optical parametric chirped-pulse amplification (OPCPA) based on two-beam pumping, using sub-nanosecond pulses generated by stimulated Brillouin scattering compression. Seed pulse energy, duration, and center wavelength were 5 nJ, 220 ps, and ˜1065 nm, respectively. The 532 nm pulse from a Q-switched Nd:YAG laser was compressed to ˜400 ps in heavy fluorocarbon FC-40 liquid. Stacking of two time-delayed pump pulses reduced the amplifier gain fluctuation. Using a walk-off-compensated two-stage OPCPA at a pump energy of 34 mJ, a total gain of 1.6 × 105 was obtained, yielding an output energy of 0.8 mJ. The amplified chirped pulse was compressed to 97 fs.

From reactors to long pulse sources

International Nuclear Information System (INIS)

Mezei, F.

1995-01-01

We will show, that by using an adapted instrumentation concept, the performance of a continuous source can be emulated by one switch on in long pulses for only about 10% of the total time. This 10 fold gain in neutron economy opens up the way for building reactor like sources with an order of magnitude higher flux than the present technological limits. Linac accelerator driven spallation lends itself favorably for the realization of this kind of long pulse sources, which will be complementary to short pulse spallation sources, the same way continuous reactor sources are

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

Energy Technology Data Exchange (ETDEWEB)

Engel, Robin, E-mail: robin.engel@uni-oldenburg.de [Deutsches Elektronen-Synchrotron, Notkestrasse 85, D-22603 Hamburg (Germany); Institut für Physik, Carl von Ossietzky Universität Oldenburg, D-26111 Oldenburg (Germany); Institut für Laser und Optik, Hochschule Emden/Leer, University of Applied Sciences, Constantiaplatz 4, D-26723 Emden (Germany); Düsterer, Stefan; Brenner, Günter [Deutsches Elektronen-Synchrotron, Notkestrasse 85, D-22603 Hamburg (Germany); Teubner, Ulrich [Deutsches Elektronen-Synchrotron, Notkestrasse 85, D-22603 Hamburg (Germany); Institut für Physik, Carl von Ossietzky Universität Oldenburg, D-26111 Oldenburg (Germany); Institut für Laser und Optik, Hochschule Emden/Leer, University of Applied Sciences, Constantiaplatz 4, D-26723 Emden (Germany)

2016-01-01

Considering the second-order spectral correlation function of SASE-FEL radiation allows a real-time observation of the photon pulse duration during spectra acquisition. 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.

Pulse radiolysis with (sub) nanosecond time resolution using a 3 MV electron accelerator

International Nuclear Information System (INIS)

Luthjens, L.H.

1986-01-01

In this thesis the development of equipment for pulse radiolysis is described and the application of the technique to time-resolved measurements of the fluorescence emission of excited states formed after irradiation of some alkanes is dealt with. A review is given of the development of the pulsed 3MV Van de Graaf electron accelerator for the generation of subnanosecond electron beam pulses and of the development of the equipment for optical detection as accomplished by the author. The initial stage of a further development for shorter pulses and higher time resolution is briefly discussed. A collection of papers on the development of apparatus and a collection of papers dealing with the results obtained from measurements of the fluorescence of excited states, formed by the recombination of electrons and ions in irradiated alkanes such as cyclohexane and the decalines, are included. (Auth.)

Time differentiated nuclear resonance spectroscopy coupled with pulsed laser heating in diamond anvil cells

Energy Technology Data Exchange (ETDEWEB)

Kupenko, I., E-mail: kupenko@esrf.fr; Strohm, C. [Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth (Germany); ESRF-The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9 (France); McCammon, C.; Cerantola, V.; Petitgirard, S.; Dubrovinsky, L. [Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth (Germany); Glazyrin, K. [Photon Science, DESY, D-22607 Hamburg (Germany); Vasiukov, D.; Aprilis, G. [Laboratory of Crystallography, Material Physics and Technology at Extreme Conditions, Universität Bayreuth, D-95440 Bayreuth (Germany); Chumakov, A. I.; Rüffer, R. [ESRF-The European Synchrotron, CS 40220, 38043 Grenoble Cedex 9 (France)

2015-11-15

Developments in pulsed laser heating applied to nuclear resonance techniques are presented together with their applications to studies of geophysically relevant materials. Continuous laser heating in diamond anvil cells is a widely used method to generate extreme temperatures at static high pressure conditions in order to study the structure and properties of materials found in deep planetary interiors. The pulsed laser heating technique has advantages over continuous heating, including prevention of the spreading of heated sample and/or the pressure medium and, thus, a better stability of the heating process. Time differentiated data acquisition coupled with pulsed laser heating in diamond anvil cells was successfully tested at the Nuclear Resonance beamline (ID18) of the European Synchrotron Radiation Facility. We show examples applying the method to investigation of an assemblage containing ε-Fe, FeO, and Fe{sub 3}C using synchrotron Mössbauer source spectroscopy, FeCO{sub 3} using nuclear inelastic scattering, and Fe{sub 2}O{sub 3} using nuclear forward scattering. These examples demonstrate the applicability of pulsed laser heating in diamond anvil cells to spectroscopic techniques with long data acquisition times, because it enables stable pulsed heating with data collection at specific time intervals that are synchronized with laser pulses.

PULSE INTENSITY MODULATION AND THE TIMING STABILITY OF MILLISECOND PULSARS: A CASE STUDY OF PSR J1713+0747

Energy Technology Data Exchange (ETDEWEB)

Shannon, Ryan M. [CSIRO Astronomy and Space Science, Box 76, Epping, NSW 1710 (Australia); Cordes, James M., E-mail: ryan.shannon@csiro.au, E-mail: cordes@astro.cornell.edu [Astronomy Department, Cornell University, Ithaca, NY 14853 (United States)

2012-12-10

Most millisecond pulsars, like essentially all other radio pulsars, show timing errors well in excess of what is expected from additive radiometer noise alone. We show that changes in amplitude, shape, and pulse phase for the millisecond pulsar J1713+0747 cause this excess error. These changes appear to be uncorrelated from one pulse period to the next. The resulting time of arrival (TOA) variations are correlated across a wide frequency range and is observed with different backend processors on different days, confirming that they are intrinsic in origin and not an instrumental effect or caused by strongly frequency-dependent interstellar scattering. Centroids of single pulses show an rms phase variation Almost-Equal-To 40 {mu}s, which dominates the timing error and is the same phase jitter phenomenon long known in slower spinning, canonical pulsars. We show that the amplitude modulations of single pulses are modestly correlated with their arrival time fluctuations. We also demonstrate that single-pulse variations are completely consistent with arrival time variations of pulse profiles obtained by integrating N pulses such that the arrival-time error decreases proportional to 1/{radical}N. We investigate methods for correcting TOAs for these pulse-shape changes, including multi-component TOA fitting and principal component analysis. These techniques are not found to improve the timing precision of the observations. We conclude that when pulse-shape changes dominate timing errors, the timing precision of PSR J1713+0747 can be only improved by averaging over a larger number of pulses.

Pulsed rf excited spectrometer having improved pulse width control

International Nuclear Information System (INIS)

1977-01-01

RF excitation for a spectrometer is obtained by pulse width modulating an RF carrier to produce the desired broadband RF exciting spectrum. The RF excitation includes a train of composite RF pulses, each composite pulse having a primary pulse portion of a first RF phase and a second pulse portion of a second RF phase opposite that of the first. In this manner, the finite rise and fall times of the primary pulse portion are compensated for by the corresponding rise and fall times of the secondary pulse portion. The primary pulse portion is lengthened by an amount equal to the secondary pulse portion so that the secondary pulse portion cancels the added primary pulse portion. In a spectrometer, the compensating second pulse component removes certain undesired side bands of the RF excitation caused by the finite rise and fall times of the applied RF pulses. The compensating second pulse component removes certain undesired side bands associated with each of the resonant lines of the excited resonance spectrum of the sample under analysis, particularly for wide band RF excitation

Rietveld refinement with time-of-flight powder diffraction data from pulsed neutron sources

International Nuclear Information System (INIS)

David, W.I.F.; Jorgensen, J.D.

1990-10-01

The recent development of accelerator-based pulsed neutron sources has led to the widespread use of the time-of-flight technique for neutron powder diffraction. The properties of the pulsed source make possible unusually high resolution over a wide range of d spacings, high count rates, and the ability to collect complete data at fixed scattering angles. The peak shape and other instrument characteristics can be accurately modelled, which make Rietveld refinement possible for complex structures. In this paper we briefly review the development of the Rietveld method for time-of-flight diffraction data from pulsed neutron sources and discuss the latest developments in high resolution instrumentation and advanced Rietveld analysis methods. 50 refs., 12 figs., 14 tabs

Strong-field Breit–Wheeler pair production in two consecutive laser pulses with variable time delay

Directory of Open Access Journals (Sweden)

Martin J.A. Jansen

2017-03-01

Full Text Available Photoproduction of electron–positron pairs by the strong-field Breit–Wheeler process in an intense laser field is studied. The laser field is assumed to consist of two consecutive short pulses, with a variable time delay in between. By numerical calculations within the framework of scalar quantum electrodynamics, we demonstrate that the time delay exerts a strong impact on the pair-creation probability. For the case when both pulses are identical, the effect is traced back to the relative quantum phase of the interfering S-matrix amplitudes and explained within a simplified analytical model. Conversely, when the two laser pulses differ from each other, the pair-creation probability depends not only on the time delay but, in general, also on the temporal order of the pulses.

Space-time-dependent development of the plasma in a pulsed hollow-cathode discharge

International Nuclear Information System (INIS)

Schaefer, G.; Wages, M.

1988-01-01

This paper presents streak camera investigations on the space-time-dependent development of pulsed hollow-cathode discharges (HCD's) starting from low-current preionization discharges. The discharges started closer to the end of the cathode, then moved further into the cathode, and then spread over a longer range along the axis of the cathode. The depth range of the intense pulsed hollow-cathode plasma was found to be two to eight times the cathode diameter

Shaper for time fixing of photomultiplier pulses

International Nuclear Information System (INIS)

Akimov, D.Yu.; Merzlyakov, S.I.

1982-01-01

A shaper for time fixing of photoelectron multiplier pulses is described. The shaper is a part of gamma telescope time-of-flight system used for prolonged astrophysical observations. Nonlinear attenuation is provided when shaping a bipolar signal. This permits to conduct discrimination not at zero level but at a higher level in order to increase noise immunity and long-time stability. The shaper is based on the integrated circuits of the 100 series. The accuracy of the time fixing in the amplitude range of 0.5-5 V constitutes +-0.1 ns. The proper delay of the shaper is about 30 ns. Tests of several shapers in the temperature range of 25-55 deg C have shown that the mean increase in the output signal delay constitutes 0.2 ns per 10 deg C. The component proper selection permits to decrease the drift of delay for different specimens up to [ru

Pulse Splitting for Harmonic Beamforming in Time-Modulated Linear Arrays

Directory of Open Access Journals (Sweden)

Lorenzo Poli

2014-01-01

Full Text Available A novel strategy for harmonic beamforming in time-modulated linear arrays is proposed. The pulse splitting technique is exploited to simultaneously generate two harmonic patterns, one at the central frequency and another at a preselected harmonic of arbitrary order, while controlling the maximum level of the remaining sideband radiations. An optimization strategy based on the particle swarm optimizer is developed in order to determine the optimal parameters describing the pulse sequence used to modulate the excitation weights of the array elements. Representative numerical results are reported and discussed to point out potentialities and limitations of the proposed approach.

Pulse GaAs field transistor amplifier with subnanosecond time transient

International Nuclear Information System (INIS)

Sidnev, A.N.

1987-01-01

Pulse amplifier on fast field effect GaAs transistors with Schottky barrier is described. The amplifier contains four cascades, the first three of which are made on combined transistors on the common-drain circuit. The last cascade is made on high-power field effect GaAs transistor for coordination with 50 ohm load. The amplifier operates within the range of input signals from 0.5 up to 100 mV with repetition frequency up to 16 Hz, The gain of the amplifier is ≅ 20 dB. The setting time at output pulses amplitude up to 1 V constitutes ∼ 0.2 ns

Pulse on pulse: modulation and signification in Rafael Lozano-Hemmer's Pulse Room

Directory of Open Access Journals (Sweden)

Merete Carlson

2012-06-01

Full Text Available This article investigates the relation between signifying processes and non-signifying material dynamism in the installation Pulse Room (2006 by Mexican Canadian artist Rafael Lozano-Hemmer. In Pulse Room the sense of pulse is ambiguous. Biorhythms are transmitted from the pulsing energy of the visitor's beating heart to the flashing of a fragile light bulb, thereby transforming each light bulb into a register of individual life. But at the same time the flashing light bulbs together produce a chaotically flickering light environment composed by various layers of repetitive rhythms, a vibrant and pulsating “room”. Hence, the visitor in Pulse Room is invited into a complex scenario that continuously oscillates between various aspects of signification (the light bulbs representing individual lives; the pulse itself as the symbolic “rhythm of life” and instants of pure material processuality (flickering light bulbs; polyrhythmic layers. Taking our point of departure in a discussion of Gilles Deleuze's concepts of modulation and signaletic material in relation to electronic media, we examine how the complex orchestration of pulsation between signification and material modulation produces a multilayered sense of time and space that is central to the sensory experience of Pulse Room as a whole. Pulse Room is, at the very same time, a relational subject–object intimacy and an all-encompassing immersive environment modulating continuously in real space-time.

Time resolved studies of H2+ dissociation with phase-stabilized laser pulses

International Nuclear Information System (INIS)

Fischer, Bettina

2010-01-01

In the course of this thesis, experimental studies on the dissociation of H 2 + (H 2 + →p+H) in ultrashort laser pulses with a stabilized carrier-envelope phase (CEP) were carried out. In single-pulse measurements, the ability to control the emission direction of low energetic protons, i.e. the localization of the bound electron at one of the nuclei after dissociation, by the CEP was demonstrated. The coincident detection of the emitted protons and electrons and the measurement of their three-dimensional momentum vectors with a reaction microscope allowed to clarify the localization mechanism. Further control was achieved by a pump-control scheme with two timedelayed CEP-stabilized laser pulses. Here the neutral H 2 molecule was ionized in the first pulse and dissociation was induced by the second pulse. Electron localization was shown to depend on the properties of the bound nuclear wave packet in H 2 + at the time the control pulse is applied, demonstrating the ability to use the shape and dynamics of the nuclear wave packet as control parameters. Wave packet simulations were performed reproducing qualitatively the experimental results of the single and the two-pulse measurements. For both control schemes, intuitive models are presented, which qualitatively explain the main features of the obtained results. (orig.)

Simultaneous hit finding and timing method for pulse shape analysis of drift chamber signals

Energy Technology Data Exchange (ETDEWEB)

Schaile, D; Schaile, O; Schwarz, J

1986-01-01

An algorithm for the analysis of the digitized signal waveform of drift chamber pulses is described which yields a good multihit resolution and an accurate drift time determination with little processing time. The method has been tested and evaluated with measured pulse shapes from the full size prototype of the OPAL central detector which were digitized by 100 MHz FADCs. (orig.).

Simultaneous hit finding and timing method for pulse shape analysis of drift chamber signals

Energy Technology Data Exchange (ETDEWEB)

Schaile, D; Schaile, O; Schwarz, J

1986-01-01

An algorithm for the analysis of the digitized signal waveform of drift chamber pulses is described which yields a good multihit resolution and an accurate drift time determination with little processing time. The method has been tested and evaluated with measured pulse shapes from the full size prototype of the OPAL central detector which were digitized by 100 MHz FADCs.

Use of a prototype pulse oximeter for time series analysis of heart rate variability

Science.gov (United States)

González, Erika; López, Jehú; Hautefeuille, Mathieu; Velázquez, Víctor; Del Moral, Jésica

2015-05-01

This work presents the development of a low cost pulse oximeter prototype consisting of pulsed red and infrared commercial LEDs and a broad spectral photodetector used to register time series of heart rate and oxygen saturation of blood. This platform, besides providing these values, like any other pulse oximeter, processes the signals to compute a power spectrum analysis of the patient heart rate variability in real time and, additionally, the device allows access to all raw and analyzed data if databases construction is required or another kind of further analysis is desired. Since the prototype is capable of acquiring data for long periods of time, it is suitable for collecting data in real life activities, enabling the development of future wearable applications.

Time-resolved pulsed hydrogen/deuterium exchange mass spectrometry probes gaseous proteins structural kinetics.

Science.gov (United States)

Rajabi, Khadijeh

2015-01-01

A pulsed hydrogen/deuterium exchange (HDX) method has been developed for rapid monitoring of the exchange kinetics of protein ions with D2O a few milliseconds after electrospray ionization (ESI). The stepwise gradual evolution of HDX of multiply charged protein ions was monitored using the pulsed HDX mass spectrometry technique. Upon introducing a very short pulse of D2O (in the μs to ms time scale) into the linear ion trap (LIT) of a time-of-flight (TOF) mass spectrometer, bimodal distributions were detected for the ions of cytochrome c and ubiquitin. Mechanistic details of HDX reactions for ubiquitin and cytochrome c in the gas phase were uncovered and the structural transitions were followed by analyzing the kinetics of HDX.

Analysis on the arcelin expression in bruchid pest resistant wild pulses using real time RT-qPCR.

Science.gov (United States)

Sakthivelkumar, Shanmugavel; Veeramani, Velayutham; Hilda, Karuppiah; Arumugam, Munusamy; Janarthanan, Sundaram

2014-12-01

Arcelin, the antimetabolic protein from wild pulses is a known natural insecticidal molecule. Wild pulses with high arcelin content could serve as potential source to. increase the levels of insect resistance in cultivated pulse crops. In this study, arcelin (Arl) gene expression was screened in seven stored product insect pest resistant wild pulse varieties using real time RT-qPCR. Arcelin gene specific real time PCR primers were synthesized from arcelin mRNA sequence of the wild pulse variety, Lablab purpureus. The results revealed different levels of arcelin gene expression in the tested varieties. Canavalia virosa registered significantly high content indicating its suitability for utilization of arcelin gene in developing stored product insect pest resistance with other cultivated pulses.

Realtime aspects of pulse-to-pulse modulation

International Nuclear Information System (INIS)

Steiner, R.; Riedel, C.; Roesch, W.

1992-01-01

The pulse-to-pulse modulation of the SIS-ESR control system is described. Fast response to operator interaction and to changes in process conditions is emphasized as well as the essential part played by the timing system in pulse-to-pulse modulation. (author)

Dynamical suppression of nuclear-spin decoherence time in Si and GaAs using inversion pulses

International Nuclear Information System (INIS)

Watanabe, S.; Harada, J.; Sasaki, S.; Hirayama, Y.

2007-01-01

We found that nuclear-spin decoherence is suppressed by applying inversion pulses such as alternating phase Carr-Purcell (APCP) and Carr-Purcell-Meiboom-Gill (CPMG) sequences in silicon and GaAs. The decoherence time reaches ∼1.3s by applying inversion pulses, which is ∼200 times as long as the characteristic decay time obtained from the Hahn echo sequence (∼6ms) in silicon

Pulse shape analyzer/timing-SCA application to beta measurement by plastic scintillator

International Nuclear Information System (INIS)

Celiktas, C.; Selvi, S.

2000-01-01

Noise contribution to pulses from BC-400 plastic scintillators, preamplifier and spectroscopy amplifier is rejected by using electronics processing of the modified beta spectrometer containing pulse shape analyzer/timing SCA and related complementary equipment. The noise rejection capability of the spectrometer which have been developed to measure pure and scattered beta spectra, which are reliable in view of evaluations of the detector and target electron scattering characteristics correctly. (author)

Real-time optical diagnostics of graphene growth induced by pulsed chemical vapor deposition

Science.gov (United States)

Puretzky, Alexander A.; Geohegan, David B.; Pannala, Sreekanth; Rouleau, Christopher M.; Regmi, Murari; Thonnard, Norbert; Eres, Gyula

2013-06-01

The kinetics and mechanisms of graphene growth on Ni films at 720-880 °C have been measured using fast pulses of acetylene and real-time optical diagnostics. In situ UV-Raman spectroscopy was used to unambiguously detect isothermal graphene growth at high temperatures, measure the growth kinetics with ~1 s temporal resolution, and estimate the fractional precipitation upon cooldown. Optical reflectivity and videography provided much faster temporal resolution. Both the growth kinetics and the fractional isothermal precipitation were found to be governed by the C2H2 partial pressure in the CVD pulse for a given film thickness and temperature, with up to ~94% of graphene growth occurring isothermally within 1 second at 800 °C at high partial pressures. At lower partial pressures, isothermal graphene growth is shown to continue 10 seconds after the gas pulse. These flux-dependent growth kinetics are described in the context of a dissolution/precipitation model, where carbon rapidly dissolves into the Ni film and later precipitates driven by gradients in the chemical potential. The combination of pulsed-CVD and real-time optical diagnostics opens new opportunities to understand and control the fast, sub-second growth of graphene on various substrates at high temperatures.The kinetics and mechanisms of graphene growth on Ni films at 720-880 °C have been measured using fast pulses of acetylene and real-time optical diagnostics. In situ UV-Raman spectroscopy was used to unambiguously detect isothermal graphene growth at high temperatures, measure the growth kinetics with ~1 s temporal resolution, and estimate the fractional precipitation upon cooldown. Optical reflectivity and videography provided much faster temporal resolution. Both the growth kinetics and the fractional isothermal precipitation were found to be governed by the C2H2 partial pressure in the CVD pulse for a given film thickness and temperature, with up to ~94% of graphene growth occurring isothermally

Comparison of WDM/Pulse-Position-Modulation (WDM/PPM) with Code/Pulse-Position-Swapping (C/PPS) Based on Wavelength/Time Codes

Energy Technology Data Exchange (ETDEWEB)

Mendez, A J; Hernandez, V J; Gagliardi, R M; Bennett, C V

2009-06-19

Pulse position modulation (PPM) signaling is favored in intensity modulated/direct detection (IM/DD) systems that have average power limitations. Combining PPM with WDM over a fiber link (WDM/PPM) enables multiple accessing and increases the link's throughput. Electronic bandwidth and synchronization advantages are further gained by mapping the time slots of PPM onto a code space, or code/pulse-position-swapping (C/PPS). The property of multiple bits per symbol typical of PPM can be combined with multiple accessing by using wavelength/time [W/T] codes in C/PPS. This paper compares the performance of WDM/PPM and C/PPS for equal wavelengths and bandwidth.

A combined time-of-flight and depth-of-interaction detector for total-body positron emission tomography

Energy Technology Data Exchange (ETDEWEB)

Berg, Eric, E-mail: eberg@ucdavis.edu; Roncali, Emilie; Du, Junwei; Cherry, Simon R. [Department of Biomedical Engineering, University of California, Davis, One Shields Avenue, Davis, California 95616 (United States); Kapusta, Maciej [Molecular Imaging, Siemens Healthcare, Knoxville, Tennessee 37932 (United States)

2016-02-15

Purpose: In support of a project to build a total-body PET scanner with an axial field-of-view of 2 m, the authors are developing simple, cost-effective block detectors with combined time-of-flight (TOF) and depth-of-interaction (DOI) capabilities. Methods: This work focuses on investigating the potential of phosphor-coated crystals with conventional PMT-based block detector readout to provide DOI information while preserving timing resolution. The authors explored a variety of phosphor-coating configurations with single crystals and crystal arrays. Several pulse shape discrimination techniques were investigated, including decay time, delayed charge integration (DCI), and average signal shapes. Results: Pulse shape discrimination based on DCI provided the lowest DOI positioning error: 2 mm DOI positioning error was obtained with single phosphor-coated crystals while 3–3.5 mm DOI error was measured with the block detector module. Minimal timing resolution degradation was observed with single phosphor-coated crystals compared to uncoated crystals, and a timing resolution of 442 ps was obtained with phosphor-coated crystals in the block detector compared to 404 ps without phosphor coating. Flood maps showed a slight degradation in crystal resolvability with phosphor-coated crystals; however, all crystals could be resolved. Energy resolution was degraded by 3%–7% with phosphor-coated crystals compared to uncoated crystals. Conclusions: These results demonstrate the feasibility of obtaining TOF–DOI capabilities with simple block detector readout using phosphor-coated crystals.

A combined time-of-flight and depth-of-interaction detector for total-body positron emission tomography

International Nuclear Information System (INIS)

Berg, Eric; Roncali, Emilie; Du, Junwei; Cherry, Simon R.; Kapusta, Maciej

2016-01-01

Purpose: In support of a project to build a total-body PET scanner with an axial field-of-view of 2 m, the authors are developing simple, cost-effective block detectors with combined time-of-flight (TOF) and depth-of-interaction (DOI) capabilities. Methods: This work focuses on investigating the potential of phosphor-coated crystals with conventional PMT-based block detector readout to provide DOI information while preserving timing resolution. The authors explored a variety of phosphor-coating configurations with single crystals and crystal arrays. Several pulse shape discrimination techniques were investigated, including decay time, delayed charge integration (DCI), and average signal shapes. Results: Pulse shape discrimination based on DCI provided the lowest DOI positioning error: 2 mm DOI positioning error was obtained with single phosphor-coated crystals while 3–3.5 mm DOI error was measured with the block detector module. Minimal timing resolution degradation was observed with single phosphor-coated crystals compared to uncoated crystals, and a timing resolution of 442 ps was obtained with phosphor-coated crystals in the block detector compared to 404 ps without phosphor coating. Flood maps showed a slight degradation in crystal resolvability with phosphor-coated crystals; however, all crystals could be resolved. Energy resolution was degraded by 3%–7% with phosphor-coated crystals compared to uncoated crystals. Conclusions: These results demonstrate the feasibility of obtaining TOF–DOI capabilities with simple block detector readout using phosphor-coated crystals

Smartphone-based Continuous Blood Pressure Measurement Using Pulse Transit Time.

Science.gov (United States)

Gholamhosseini, Hamid; Meintjes, Andries; Baig, Mirza; Linden, Maria

2016-01-01

The increasing availability of low cost and easy to use personalized medical monitoring devices has opened the door for new and innovative methods of health monitoring to emerge. Cuff-less and continuous methods of measuring blood pressure are particularly attractive as blood pressure is one of the most important measurements of long term cardiovascular health. Current methods of noninvasive blood pressure measurement are based on inflation and deflation of a cuff with some effects on arteries where blood pressure is being measured. This inflation can also cause patient discomfort and alter the measurement results. In this work, a mobile application was developed to collate the PhotoPlethysmoGramm (PPG) waveform provided by a pulse oximeter and the electrocardiogram (ECG) for calculating the pulse transit time. This information is then indirectly related to the user's systolic blood pressure. The developed application successfully connects to the PPG and ECG monitoring devices using Bluetooth wireless connection and stores the data onto an online server. The pulse transit time is estimated in real time and the user's systolic blood pressure can be estimated after the system has been calibrated. The synchronization between the two devices was found to pose a challenge to this method of continuous blood pressure monitoring. However, the implemented continuous blood pressure monitoring system effectively serves as a proof of concept. This combined with the massive benefits that an accurate and robust continuous blood pressure monitoring system would provide indicates that it is certainly worthwhile to further develop this system.

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

Science.gov (United States)

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

2018-04-16

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

Increasing accuracy of pulse transit time measurements by automated elimination of distorted photoplethysmography waves

NARCIS (Netherlands)

M.H.N. van Velzen (M. H N); A.J. Loeve (Arjo J.); S.P. Niehof (Sjoerd); E.G. Mik (Egbert)

2017-01-01

textabstractPhotoplethysmography (PPG) is a widely available non-invasive optical technique to visualize pressure pulse waves (PWs). Pulse transit time (PTT) is a physiological parameter that is often derived from calculations on ECG and PPG signals and is based on tightly defined characteristics of

Radiofrequency glow discharge time of flight mass spectrometry: pulsed vs. continuous mode

International Nuclear Information System (INIS)

Lobo, L.; Pereiro, R.; Sanz-Medel, A.; Bordel, N.; Tempez, A.; Chapon, P.; Hohl, M.; Michler, J.

2009-01-01

Full text: Glow discharge (GD) is a well established tool for the direct analysis of solids. The application field of the original direct current GD, restricted to conductive samples, has been extended by radiofrequency powered GDs that can be applied for conductive and non-conductive samples. Moreover, the introduction of pulsed GD has opened the possibility of applying higher instantaneous powers that can improve the atomization-ionization processes and therefore the sensitivity. Furthermore, pulsed-GD may enable temporal separation of discharge gas species from the sample ions. In this work the analytical performances of radiofrequency and pulsed radiofrequency glow discharges are evaluated by using a time of flight mass analyzer (TOFMS). (author)

Bipolar pulse generator for intense pulsed ion beam accelerator

International Nuclear Information System (INIS)

Ito, H.; Igawa, K.; Kitamura, I.; Masugata, K.

2007-01-01

A new type of pulsed ion beam accelerator named ''bipolar pulse accelerator'' (BPA) has been proposed in order to improve the purity of intense pulsed ion beams. To confirm the principle of the BPA, we developed a bipolar pulse generator for the bipolar pulse experiment, which consists of a Marx generator and a pulse forming line (PFL) with a rail gap switch on its end. In this article, we report the first experimental result of the bipolar pulse and evaluate the electrical characteristics of the bipolar pulse generator. When the bipolar pulse generator was operated at 70% of the full charge condition of the PFL, the bipolar pulse with the first (-138 kV, 72 ns) and the second pulse (+130 kV, 70 ns) was successfully obtained. The evaluation of the electrical characteristics indicates that the developed generator can produce the bipolar pulse with fast rise time and sharp reversing time

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

International Nuclear Information System (INIS)

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.

2014-01-01

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

Experimental investigations of argon spark gap recovery times by developing a high voltage double pulse generator.

Science.gov (United States)

Reddy, C S; Patel, A S; Naresh, P; Sharma, Archana; Mittal, K C

2014-06-01

The voltage recovery in a spark gap for repetitive switching has been a long research interest. A two-pulse technique is used to determine the voltage recovery times of gas spark gap switch with argon gas. First pulse is applied to the spark gap to over-volt the gap and initiate the breakdown and second pulse is used to determine the recovery voltage of the gap. A pulse transformer based double pulse generator capable of generating 40 kV peak pulses with rise time of 300 ns and 1.5 μs FWHM and with a delay of 10 μs-1 s was developed. A matrix transformer topology is used to get fast rise times by reducing L(l)C(d) product in the circuit. Recovery Experiments have been conducted for 2 mm, 3 mm, and 4 mm gap length with 0-2 bars pressure for argon gas. Electrodes of a sparkgap chamber are of rogowsky profile type, made up of stainless steel material, and thickness of 15 mm are used in the recovery study. The variation in the distance and pressure effects the recovery rate of the spark gap. An intermediate plateu is observed in the spark gap recovery curves. Recovery time decreases with increase in pressure and shorter gaps in length are recovering faster than longer gaps.

Increasing accuracy of pulse transit time measurements by automated elimination of distorted photoplethysmography waves

NARCIS (Netherlands)

van Velzen, M.H.N.; Loeve, A.J.; Niehof, S.P.; Mik, E.G.

2017-01-01

Photoplethysmography (PPG) is a widely available non-invasive optical technique to visualize pressure pulse waves (PWs). Pulse transit time (PTT) is a physiological parameter that is often derived from calculations on ECG and PPG signals and is based on tightly defined characteristics of the PW

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

Science.gov (United States)

Kim, Kyunghan; Guo, Zhixiong

2007-05-01

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

Pulse Rise Time Characterization of a High Pressure Xenon Gamma Detector for use in Resolution Enhancement

International Nuclear Information System (INIS)

TROYER, G.L.

2000-01-01

High pressure xenon ionization chamber detectors are possible alternatives to traditional thallium doped sodium iodide (NaI(Tl)) and hyperpure germanium as gamma spectrometers in certain applications. Xenon detectors incorporating a Frisch grid exhibit energy resolutions comparable to cadmium/zinc/telluride (CZT) (e.g. 2% (at) 662keV) but with far greater sensitive volumes. The Frisch grid reduces the position dependence of the anode pulse risetimes, but it also increases the detector vibration sensitivity, anode capacitance, voltage requirements and mechanical complexity. We have been investigating the possibility of eliminating the grid electrode in high-pressure xenon detectors and preserving the high energy resolution using electronic risetime compensation methods. A two-electrode cylindrical high pressure xenon gamma detector coupled to time-to-amplitude conversion electronics was used to characterize the pulse rise time of deposited gamma photons. Time discrimination was used to characterize the pulse rise time versus photo peak position and resolution. These data were collected to investigate the effect of pulse rise time compensation on resolution and efficiency

Time domain simulations of preliminary breakdown pulses in natural lightning.

Science.gov (United States)

Carlson, B E; Liang, C; Bitzer, P; Christian, H

2015-06-16

Lightning discharge is a complicated process with relevant physical scales spanning many orders of magnitude. In an effort to understand the electrodynamics of lightning and connect physical properties of the channel to observed behavior, we construct a simulation of charge and current flow on a narrow conducting channel embedded in three-dimensional space with the time domain electric field integral equation, the method of moments, and the thin-wire approximation. The method includes approximate treatment of resistance evolution due to lightning channel heating and the corona sheath of charge surrounding the lightning channel. Focusing our attention on preliminary breakdown in natural lightning by simulating stepwise channel extension with a simplified geometry, our simulation reproduces the broad features observed in data collected with the Huntsville Alabama Marx Meter Array. Some deviations in pulse shape details are evident, suggesting future work focusing on the detailed properties of the stepping mechanism. Preliminary breakdown pulses can be reproduced by simulated channel extension Channel heating and corona sheath formation are crucial to proper pulse shape Extension processes and channel orientation significantly affect observations.

Day-to-day repeatability of the Pulse Time Index of Norm

Directory of Open Access Journals (Sweden)

Posokhov IN

2014-02-01

Full Text Available Igor N Posokhov,1 Aleksandra O Konradi,2 Eugeny V Shlyakhto,2 Oleg V Mamontov,2 Artemy V Orlov,3 Anatoly N Rogoza4 1Hemodynamic Laboratory Ltd, Nizhniy Novgorod, 2Almazov Federal Heart, Blood and Endocrinology Centre, Saint Petersburg, 3Department 65 Competitive System Analysis, National Research Nuclear University, Moscow, 4Cardiology Research Center, Moscow, Russia Abstract: The pulse wave velocity (PWV threshold for hypertensive target organ damage is presently set at 10 meters per second. New 24-hour monitors (eg, BPLab® and Vasotens® provide several PWV measurements over a period of 24–72 hours. A new parameter, ie, the Pulse Time Index of Norm (PTIN, can be calculated from these data. The PTIN is defined as the percentage of a 24-hour period during which the PWV does not exceed 10 meters per second. The aim of the present study was to test the new PTIN for clinical feasibility using day-to-day repeatability analysis. Oscillometrically generated waveform files (n=85, which were previously used for research studies, were reanalyzed using the new 2013 version software of the Vasotens technology program, which enables calculation of PTIN. The intraclass correlation coefficient was 0.98 and Cronbach's alpha was 0.97, indicating that the PTIN has excellent day-to-day repeatability and internal consistency. The present results show adequate repeatability, and PTIN assessment using the Vasotens technology appears to be feasible. Keywords: pulse wave velocity, ambulatory, 24-hour, monitoring, Pulse Time Index of Norm, arterial stiffness

Towards optimized suppression of dephasing in systems subject to pulse timing constraints

International Nuclear Information System (INIS)

Hodgson, Thomas E.; D'Amico, Irene; Viola, Lorenza

2010-01-01

We investigate the effectiveness of different dynamical decoupling protocols for storage of a single qubit in the presence of a purely dephasing bosonic bath, with emphasis on comparing quantum coherence preservation under uniform versus nonuniform delay times between pulses. In the limit of instantaneous bit-flip pulses, this is accomplished by establishing a different representation of the controlled qubit evolution, where the decoherence behavior after an arbitrary number of pulses is directly expressed in terms of the uncontrolled decoherence function. In particular, analytical expressions are obtained for approximation of the long- and short-term coherence behavior for both Ohmic and supra-Ohmic environments. By focusing on the realistic case of pure dephasing in an excitonic qubit, we quantitatively assess the impact of physical constraints on achievable pulse separations, and show that little advantage of high-level decoupling schemes based on concatenated or optimal design may be expected if pulses cannot be applied sufficiently fast. In such constrained scenarios, we demonstrate how simple modifications of repeated periodic-echo protocols can offer significantly improved coherence preservation in realistic parameter regimes. We expect similar conclusions to be relevant to other constrained qubit devices exposed to quantum or classical phase noise.

Real-time lossless data compression techniques for long-pulse operation

International Nuclear Information System (INIS)

Vega, J.; Ruiz, M.; Sanchez, E.; Pereira, A.; Portas, A.; Barrera, E.

2007-01-01

Data logging and data distribution will be two main tasks connected with data handling in ITER. Data logging refers to the recovery and ultimate storage of all data, independent of the data source. Data distribution is related, on the one hand, to the on-line data broadcasting for immediate data availability and, on the other hand, to the off-line data access. Due to the large data volume expected, data compression is a useful candidate to prevent the waste of resources in communication and storage systems. On-line data distribution in a long-pulse environment requires the use of a deterministic approach to be able to ensure a proper response time for data availability. However, an essential feature for all the above purposes is to apply lossless compression techniques. This article reviews different lossless data compression techniques based on delta compression. In addition, the concept of cyclic delta transformation is introduced. Furthermore, comparative results concerning compression rates on different databases (TJ-II and JET) and computation times for compression/decompression are shown. Finally, the validity and implementation of these techniques for long-pulse operation and real-time requirements is also discussed

Real-time lossless data compression techniques for long-pulse operation

Energy Technology Data Exchange (ETDEWEB)

Vega, J. [Asociacion EURATOM/CIEMAT para Fusion, Avda. Complutense 22, 28040 Madrid (Spain)], E-mail: jesus.vega@ciemat.es; Ruiz, M. [Dpto. de Sistemas Electronicos y de Control, UPM, Campus Sur. Ctra., Valencia km 7, 28031 Madrid (Spain); Sanchez, E.; Pereira, A.; Portas, A. [Asociacion EURATOM/CIEMAT para Fusion, Avda. Complutense 22, 28040 Madrid (Spain); Barrera, E. [Dpto. de Sistemas Electronicos y de Control, UPM, Campus Sur. Ctra., Valencia km 7, 28031 Madrid (Spain)

2007-10-15

Data logging and data distribution will be two main tasks connected with data handling in ITER. Data logging refers to the recovery and ultimate storage of all data, independent of the data source. Data distribution is related, on the one hand, to the on-line data broadcasting for immediate data availability and, on the other hand, to the off-line data access. Due to the large data volume expected, data compression is a useful candidate to prevent the waste of resources in communication and storage systems. On-line data distribution in a long-pulse environment requires the use of a deterministic approach to be able to ensure a proper response time for data availability. However, an essential feature for all the above purposes is to apply lossless compression techniques. This article reviews different lossless data compression techniques based on delta compression. In addition, the concept of cyclic delta transformation is introduced. Furthermore, comparative results concerning compression rates on different databases (TJ-II and JET) and computation times for compression/decompression are shown. Finally, the validity and implementation of these techniques for long-pulse operation and real-time requirements is also discussed.

Development of an electron momentum spectrometer for time-resolved experiments employing nanosecond pulsed electron beam

Science.gov (United States)

Tang, Yaguo; Shan, Xu; Liu, Zhaohui; Niu, Shanshan; Wang, Enliang; Chen, Xiangjun

2018-03-01

The low count rate of (e, 2e) electron momentum spectroscopy (EMS) has long been a major limitation of its application to the investigation of molecular dynamics. Here we report a new EMS apparatus developed for time-resolved experiments in the nanosecond time scale, in which a double toroidal energy analyzer is utilized to improve the sensitivity of the spectrometer and a nanosecond pulsed electron gun with a repetition rate of 10 kHz is used to obtain an average beam current up to nA. Meanwhile, a picosecond ultraviolet laser with a repetition rate of 5 kHz is introduced to pump the sample target. The time zero is determined by photoionizing the target using a pump laser and monitoring the change of the electron beam current with time delay between the laser pulse and electron pulse, which is influenced by the plasma induced by the photoionization. The performance of the spectrometer is demonstrated by the EMS measurement on argon using a pulsed electron beam, illustrating the potential abilities of the apparatus for investigating the molecular dynamics in excited states when employing the pump-probe scheme.

Trichromatic π-Pulse for Ultrafast Total Inversion of a Four-Level Ladder System

Directory of Open Access Journals (Sweden)

Carles Serrat

2015-11-01

Full Text Available We present a numerical solution for complete population inversion in a four-level ladder system obtained by using a full π-pulse illumination scheme with resonant ultrashort phase-locked Gaussian laser pulses. We find that a set of pulse areas such as √3π , √2π , and √3π completely inverts the four-level system considering identical effective dipole coupling coefficients. The solution is consistent provided the involved electric fields are not too strong and it is amply accurate also in the case of diverse transition dipole moments. We study the effect of detuning and chirp of the laser pulses on the complete population inversion using the level structure of atomic sodium interacting with ps and fs pulses as an example. Our result opens the door for multiple applications such as efficient ultrashort pulse lasing in the UV or the engineering of quantum states for quantum computing.

Pulse Based Time-of-Flight Range Sensing.

Science.gov (United States)

Sarbolandi, Hamed; Plack, Markus; Kolb, Andreas

2018-05-23

Pulse-based Time-of-Flight (PB-ToF) cameras are an attractive alternative range imaging approach, compared to the widely commercialized Amplitude Modulated Continuous-Wave Time-of-Flight (AMCW-ToF) approach. This paper presents an in-depth evaluation of a PB-ToF camera prototype based on the Hamamatsu area sensor S11963-01CR. We evaluate different ToF-related effects, i.e., temperature drift, systematic error, depth inhomogeneity, multi-path effects, and motion artefacts. Furthermore, we evaluate the systematic error of the system in more detail, and introduce novel concepts to improve the quality of range measurements by modifying the mode of operation of the PB-ToF camera. Finally, we describe the means of measuring the gate response of the PB-ToF sensor and using this information for PB-ToF sensor simulation.

Wavepacket dynamics of a Rydberg atom monitored by a pair of time-delayed laser pulses

Science.gov (United States)

Xin, PeiPei; Cheng, Hong; Zhang, ShanShan; Wang, HanMu; Liu, HongPing

2018-02-01

We have investigated the Rydberg state population of an argon atom by an intense laser pulse and its wavepacket dynamics monitored by another successive laser pulse in the tunneling regime. A wavepacket comprising a superposition of close high-lying Rydberg states is irradiated by a multicycle laser pulse, where the sub-wave components in the wavepacket have fixed relative phases. A time-delayed second laser pulse is employed to apply on the excited Rydberg atom. If the time is properly chosen, one of the sub-wave components will be guided towards the ionization area while the rest remains intact. By means of this pump-probe technique, we could control and monitor the Rydberg wavepacket dynamics and reveal some interesting phenomenon such as the survival rate of individual Rydberg states related to the classical orbital period of electron.

A Radiation Dosimetry Method Using Pulsed Optically Stimulated Luminescence

International Nuclear Information System (INIS)

Akselrod, M.S.; McKeever, S.W.S.

1999-01-01

A method for the determination of absorbed radiation dose is described based on pulsed optically stimulated luminescence (POSL). The method relies upon the stimulation of an irradiated sample with a train of light pulses from a suitable light source (e.g. a laser) using a wavelength which is within the range of wavelengths corresponding to the radiation-induced optical absorption in the irradiated sample. The subsequent emitted light, due to the detrapping of trapped charges and their subsequent recombination with charge of the opposite sign, is synchronously detected in the period between each stimulation pulse. The total luminescence is summed over the desired number of stimulation pulses and this forms the measured POSL signal. By monitoring the emitted light only in the period between stimulation pulses one can reduce the optical filtering required to discriminate between the stimulation light and the emission light; in this way a high measurement efficiency, and, therefore, a high radiation sensitivity (luminescence intensity per unit absorbed dose) is achieved. Key parameters in the method are the intrinsic luminescence lifetime for the material being used as the luminescent detector, the width of the optical stimulation pulse, and the period between pulses. For optimum operation the measurement parameters should be such that both the pulse width and the time between pulses are much less than the luminescence lifetime. By appropriate choice of the power of the optical stimulation, the frequency of the stimulation pulses, and the total stimulation period, one can also re-measure the absorbed dose several times. In this way, a re-read capability is available with the procedure. The method is illustrated using light from a 2nd-harmonic Nd:YAG laser, with irradiated, anion-deficient aluminium oxide as the luminescent detector material. (author)

Timing the total reflection of light

International Nuclear Information System (INIS)

Chauvat, Dominique; Bonnet, Christophe; Dunseath, Kevin; Emile, Olivier; Le Floch, Albert

2005-01-01

We have identified for the first time the absolute delay at total reflection, envisioned by Newton. We show that there are in fact two divergent Wigner delays, depending on the polarisation of the incident light. These measurements give a new insight on the passage from total reflection to refraction

Active manipulation of the selective alignment by two laser pulses

International Nuclear Information System (INIS)

Zeng-Qiang, Yang; Zhi-Rong, Guo; Gui-Xian, Ge

2010-01-01

This paper solves numerically the full time-dependent Schrödinger equation based on the rigid rotor model, and proposes a novel strategy to determine the optimal time delay of the two laser pulses to manipulate the molecular selective alignment. The results illustrate that the molecular alignment generated by the first pulse can be suppressed or enhanced selectively, the relative populations of even and odd rotational states in the final rotational wave packet can be manipulated selectively by precisely inserting the peak of the second laser pulse at the time when the slope for the alignment parameter by the first laser locates a local maximum for the even rotational states and a local minimum for the odds, and vice versa. The selective alignment can be further optimised by selecting the intensity ratio of the two laser pulses on the condition that the total laser intensity and pulse duration are kept constant. (atomic and molecular physics)

S100 lathe bed pulse generator applied to pulsed nuclear magnetic resonance

International Nuclear Information System (INIS)

Cernicchiaro, G.R.C.; Rudge, M.G.; Albuquerque, M.P.

1989-01-01

The project and construction of four channel pulse generator in the S100 standard plate and its control software for microcomputer are described. The microcomputer has total control on the pulse generator, which has seven programable parameters, defining the position of four pulses and the width for the three first ones. This pulse generator is controlled by a software developed in c language, and is used in pulsed nuclear magnetic resonance experiences. (M.C.K.) [pt

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

Science.gov (United States)

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

2017-05-29

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

Time-dependent plasma behavior triggered by a pulsed electron gun under conditions of beam-plasma-discharge

International Nuclear Information System (INIS)

Szuszczewicz, E.P.; Lin, C.S.

1982-01-01

This chapter reports on experiments whose purpose was to simulate spaceborne applications of energetic electron guns while exploring the ''in situ'' diagnostics of time-dependent beam-plasma behavior under pulsed electron gun conditions. Beam-plasma-discharge (BPD), the BPD afterglow that exists after gun-pulse termination, and the plasma decay process are considered. It is concluded that there is a rapid enhancement in plasma density as the gas turns on; that during the pulse-ON time a quasi-steady-state BPD can be maintained with characteristics identical with its dc counterpart; that in the period immediately following gun-pulse termination the plasma loss process is dominated by cross-field radial diffusion; and that the afterglow plasma is within + or -10% of being an isodensity contour

Propagation of an asymmetric relativistic laser pulse in plasma

International Nuclear Information System (INIS)

Garuchava, D.P.; Murusidze, I.G.; Suramlishvili, G.I.; Tsintsadze, N.L.; Tskhakaya, D.D.

1997-01-01

The interaction of a relativistically intense asymmetric laser pulse with a plasma has been studied. The asymmetric shape of the pulse implies that the rise time of the leading edge of the pulse is much greater than the fall time of the trailing edge. The numerical simulation of the propagation of such a pulse through an underdense plasma has shown that relativistic self-focusing enhances the effect of ponderomotive self-channeling. The radial ponderomotive force totally expels the electrons from the axis creating a density channel, that is, cavitation occurs. A very short fall time of the trailing edge (τ l ω p <1) causes a rapid increase in the amplitude of a laser driven longitudinal electric field to values of a few GV/cm at the back of the pulse. The numerical simulation also has shown that the channel as well as the large-amplitude longitudinal field can be sustained in the range immediately behind the pulse, thus creating favorable conditions to accelerate a trailing bunch of electrons to extremely high energies. According to our model, the accelerating electric field can reach the value 10 GV/cm. copyright 1997 The American Physical Society

Neutron Spectroscopy for pulsed beams with frame overlap using a double time-of-flight technique

Science.gov (United States)

Harrig, K. P.; Goldblum, B. L.; Brown, J. A.; Bleuel, D. L.; Bernstein, L. A.; Bevins, J.; Harasty, M.; Laplace, T. A.; Matthews, E. F.

2018-01-01

A new double time-of-flight (dTOF) neutron spectroscopy technique has been developed for pulsed broad spectrum sources with a duty cycle that results in frame overlap, where fast neutrons from a given pulse overtake slower neutrons from previous pulses. Using a tunable beam at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory, neutrons were produced via thick-target breakup of 16 MeV deuterons on a beryllium target in the cyclotron vault. The breakup spectral shape was deduced from a dTOF measurement using an array of EJ-309 organic liquid scintillators. Simulation of the neutron detection efficiency of the scintillator array was performed using both GEANT4 and MCNP6. The efficiency-corrected spectral shape was normalized using a foil activation technique to obtain the energy-dependent flux of the neutron beam at zero degrees with respect to the incoming deuteron beam. The dTOF neutron spectrum was compared to spectra obtained using HEPROW and GRAVEL pulse height spectrum unfolding techniques. While the unfolding and dTOF results exhibit some discrepancies in shape, the integrated flux values agree within two standard deviations. This method obviates neutron time-of-flight spectroscopy challenges posed by pulsed beams with frame overlap and opens new opportunities for pulsed white neutron source facilities.

Background subtraction system for pulsed neutron logging of earth boreholes

International Nuclear Information System (INIS)

Hopkinson, E.C.

1977-01-01

A neutron generator in well logging instrument is pulsed 100 times having a time between pulses of 1400 microseconds. This is followed by an off period of four cycles wherein 2800 microseconds is allowed for capture radiation to decay to an insignificant level and the remaining 2800 microseconds is used to measure background radiation. This results in the neutron source being disabled four pulses after every hundred pulses of operation, or approximately a 4 percent loss of neutron output. A first detector gate is open from 400 to 680 microseconds and a second detector gate is open from 700 to 980 microseconds. During the 100 cycles, each of the gates is thus open for 280 microseconds times 100 for a total of 28,000 microseconds. By scaling the gate count rate by a factor of 10, the background is subtracted directly

Timing of Pulsed Prompt Gamma Rays for Background Discrimination

International Nuclear Information System (INIS)

Hueso-Gonzalez, F.; Golnik, C.; Berthel, M.; Dreyer, A.; Kormoll, T.; Rohling, H.; Pausch, G.; Enghardt, W.; Fiedler, F.; Heidel, K.; Schoene, S.; Schwengner, R.; Wagner, A.

2013-06-01

In the context of particle therapy, particle range verification is a major challenge for the quality assurance of the treatment. One approach is the measurement of the prompt gamma rays resulting from the tissue irradiation. A Compton camera based on several planes of position sensitive gamma ray detectors, together with an imaging algorithm, is expected to reconstruct the prompt gamma ray emission density profile, which is correlated with the dose distribution. At Helmholtz- Zentrum Dresden-Rossendorf (HZDR) and OncoRay, a camera prototype has been developed consisting of two scatter planes (CdZnTe cross strip detectors) and an absorber plane (Lu 2 SiO 5 block detector). The data acquisition is based on VME electronics and handled by software developed on the ROOT platform. The prototype was tested at the linear electron accelerator ELBE at HZDR, which was set up to produce bunched bremsstrahlung photons. Their spectrum has similarities with the one expected from prompt gamma rays in the clinical case, and these are also bunched with the accelerator frequency. The time correlation between the pulsed prompt photons and the measured signals was used for background discrimination, achieving a time resolution of 3 ns (2 ns) FWHM for the CZT (LSO) detector. A time-walk correction was applied for the LSO detector and improved its resolution to 1 ns. In conclusion, the detectors are suitable for time-resolved background discrimination in pulsed clinical particle accelerators. Ongoing tasks are the test of the imaging algorithms and the quantitative comparison with simulations. Further experiments will be performed at proton accelerators. (authors)

Monitoring of railway embankment settlement with fiber-optic pulsed time-of-flight radar.

Science.gov (United States)

Kilpelä, Ari; Lyöri, Veijo; Duan, Guoyong

2012-12-01

This paper deals with a fiber-optic pulsed time-of-flight (PTOF) laser radar used for monitoring the settlement of a railway embankment. The operating principle is based on evaluating the changes in the lengths of the fiber-optic cables embedded in the embankment by measuring the time separation of the optical pulses reflected from both ends of the sensor fiber. The advantage of this method is that it integrates the elongation of the whole sensor, and many sensor fibers can be connected in series. In a field test, seven polyurethane-coated optical cables were installed in a railway embankment and used as 20-m long sensors. The optical timing pulses were created using specially polished optical connectors. The measured precision was 0.28 ps, which corresponds 1.8 μstrain elongation using a 20 m long sensor fiber, using an averaged value of 10,000 pulses for a single measurement value. The averaged elongation value of all sensors was used for cancelling out the effect of temperature variation on the elongation value of each individual sensor. The functionality of the method was tested by digging away a 7.5 m long and approximately 18 mm high section of sand below one sensor. It was measured as a +3 mm change in the length of the sensor fiber, which matched well with the theoretically calculated elongation value, 2.9 mm. The sensor type proved to be strong but flexible enough for this type of use.

Time-resolved processes in a pulsed electrical discharge in argon bubbles in water

Science.gov (United States)

Gershman, S.; Belkind, A.

2010-12-01

A phenomenological picture of a pulsed electrical discharge in gas bubbles in water is produced by combining electrical, spectroscopic, and imaging characterization methods. The discharge is generated by applying 1 μ s pulses of 5 to 20 kV between a needle and a disk electrode submerged in water. An Ar gas bubble surrounds the tip of the needle electrode. Imaging, electrical characteristics, and time-resolved optical emission spectroscopic data suggest a fast streamer propagation mechanism and the formation of a plasma channel in the bubble. Comparing the electrical and imaging data for consecutive pulses applied to the bubble at a frequency of 1 Hz indicates that each discharge proceeds as an entirely new process with no memory of the previous discharge aside from the presence of long-lived chemical species, such as ozone and oxygen. Imaging and electrical data show the presence of two discharge events during each applied voltage pulse, a forward discharge near the beginning of the applied pulse depositing charge on the surface of the bubble and a reverse discharge removing the accumulated charge from the water/gas interface when the applied voltage is turned off. The pd value of ~ 300-500 torr cm, the 1 μs long pulse duration, low repetition rate, and unidirectional character of the applied voltage pulses make the discharge process here unique compared to the traditional corona or dielectric barrier discharges.

Time resolved high frequency spectrum of Br2 molecules using pulsed photoacoustic technique.

Science.gov (United States)

Yehya, Fahem; Chaudhary, A K

2013-11-01

The paper reports the time resolved spectral distribution of higher order acoustic modes generated in Br2 molecules using pulsed Photoacoustic (PA) technique. New time resolved vibrational spectrum of Br2 molecules are recorded using a single 532nm, pulses of 7ns duration at 10Hz repetition rate obtained from Q-switched Nd:YAG laser. Frank-Condon principle based assignments confirms the presence of 12 numbers of (ν″-ν') vibrational transitions covered by a single 532+2nm pulse profile. Inclusions of higher order zeroth modes in Bassel's function expansion series shows the probability of overlapping of different types of acoustic modes in the designed PA cells. These modes appear in the form of clusters which occupies higher frequency range. The study of decay behavior of PA signal with respect to time confirms the photolysis of Br2 at 532nm wavelength. In addition, the shifting and clustering effect of cavity eigen modes in Br2 molecules have been studied between 1 and 10ms time scale. The estimated Q-factor of PA cell (l=16cm, R=1.4cm) is 145±4 at 27kHz frequency. Copyright © 2013 Elsevier B.V. All rights reserved.

The dynamic method for time-of-flight measurement of thermal neutron spectra from pulsed sources

International Nuclear Information System (INIS)

Pepyolyshev, Yu.N.; Chuklyaev, S.V.; Tulaev, A.B.; Bobrakov, V.F.

1995-01-01

A time-of-flight method for measurement of thermal neutron spectra in pulsed neutron sources with an efficiency more than 10 5 times higher than the standard method is described. The main problems associated with the electric current technique for time-of-flight spectra measurement are examined. The methodical errors, problems of special neutron detector design and other questions are discussed. Some experimental results for spectra from the surfaces of water and solid methane moderators obtained at the IBR-2 pulsed reactor (Dubna, Russia) are presented. (orig.)

Photonic generation of FCC-compliant UWB pulses based on modified Gaussian quadruplet and incoherent wavelength-to-time conversion

Science.gov (United States)

Mu, Hongqian; Wang, Muguang; Tang, Yu; Zhang, Jing; Jian, Shuisheng

2018-03-01

A novel scheme for the generation of FCC-compliant UWB pulse is proposed based on modified Gaussian quadruplet and incoherent wavelength-to-time conversion. The modified Gaussian quadruplet is synthesized based on linear sum of a broad Gaussian pulse and two narrow Gaussian pulses with the same pulse-width and amplitude peak. Within specific parameter range, FCC-compliant UWB with spectral power efficiency of higher than 39.9% can be achieved. In order to realize the designed waveform, a UWB generator based on spectral shaping and incoherent wavelength-to-time mapping is proposed. The spectral shaper is composed of a Gaussian filter and a programmable filter. Single-mode fiber functions as both dispersion device and transmission medium. Balanced photodetection is employed to combine linearly the broad Gaussian pulse and two narrow Gaussian pulses, and at same time to suppress pulse pedestals that result in low-frequency components. The proposed UWB generator can be reconfigured for UWB doublet by operating the programmable filter as a single-band Gaussian filter. The feasibility of proposed UWB generator is demonstrated experimentally. Measured UWB pulses match well with simulation results. FCC-compliant quadruplet with 10-dB bandwidth of 6.88-GHz, fractional bandwidth of 106.8% and power efficiency of 51% is achieved.

Optimization of the integration time of pulse shape analysis for dual-layer GSO detector with different amount of Ce

International Nuclear Information System (INIS)

Yamamoto, Seiichi

2008-01-01

For a multi-layer depth-of-interaction (DOI) detector using different decay times, pulse shape analysis based on two different integration times is often used to distinguish scintillators in DOI direction. This method measures a partial integration and a full integration, and calculates the ratio of these two to obtain the pulse shape distribution. The full integration time is usually set to integrate full width of the scintillation pulse. However, the optimum partial integration time is not obvious for obtaining the best separation of the pulse shape distribution. To make it clear, a theoretical analysis and experiments were conducted for pulse shape analysis by changing the partial integration time using a scintillation detector of GSOs with different amount of Ce. A scintillation detector with 1-in. round photomultiplier tube (PMT) optically coupled GSO of 1.5 mol% (decay time: 35 ns) and that of 0.5 mol% (decay time: 60 ns) was used for the experiments. The signal from PMT was digitally integrated with partial (50-150 ns) and full (160 ns) integration times and ratio of these two was calculated to obtain the pulse shape distribution. In the theoretical analysis, partial integration time of 50 ns showed largest distance between two peaks of the pulse shape distribution. In the experiments, it showed maximum at 70-80 ns of partial integration time. The peak to valley ratio showed the maximum at 120-130 ns. Because the separation of two peaks is determined by the peak to valley ratio, we conclude the optimum partial integration time for these combinations of GSOs is around 120-130 ns, relatively longer than the expected value

Time-domain SFG spectroscopy using mid-IR pulse shaping: practical and intrinsic advantages.

Science.gov (United States)

Laaser, Jennifer E; Xiong, Wei; Zanni, Martin T

2011-03-24

Sum-frequency generation (SFG) spectroscopy is a ubiquitous tool in the surface sciences. It provides infrared transition frequencies and line shapes that probe the structure and environment of molecules at interfaces. In this article, we apply techniques learned from the multidimensional spectroscopy community to SFG spectroscopy. We implement balanced heterodyne detection to remove scatter and the local oscillator background. Heterodyning also separates the resonant and nonresonant signals by acquiring both the real and imaginary parts of the spectrum. We utilize mid-IR pulse shaping to control the phase and delay of the mid-IR pump pulse. Pulse shaping allows phase cycling for data collection in the rotating frame and additional background subtraction. We also demonstrate time-domain data collection, which is a Fourier transform technique, and has many advantages in signal throughput, frequency resolution, and line shape accuracy over existing frequency domain methods. To demonstrate time-domain SFG spectroscopy, we study an aryl isocyanide on gold, and find that the system has an inhomogeneous structural distribution, in agreement with computational results, but which was not resolved by previous frequency-domain SFG studies. The ability to rapidly and actively manipulate the mid-IR pulse in an SFG pules sequence makes possible new experiments and more accurate spectra. © 2011 American Chemical Society

The time-dependence of exchange-induced relaxation during modulated radio frequency pulses.

Science.gov (United States)

Sorce, Dennis J; Michaeli, Shalom; Garwood, Michael

2006-03-01

The problem of the relaxation of identical spins 1/2 induced by chemical exchange between spins with different chemical shifts in the presence of time-dependent RF irradiation (in the first rotating frame) is considered for the fast exchange regime. The solution for the time evolution under the chemical exchange Hamiltonian in the tilted doubly rotating frame (TDRF) is presented. Detailed derivation is specified to the case of a two-site chemical exchange system with complete randomization between jumps of the exchanging spins. The derived theory can be applied to describe the modulation of the chemical exchange relaxation rate constants when using a train of adiabatic pulses, such as the hyperbolic secant pulse. Theory presented is valid for quantification of the exchange-induced time-dependent rotating frame longitudinal T1rho,ex and transverse T2rho,ex relaxations in the fast chemical exchange regime.

Pulsed dose rate brachytherapy (PDR): an analysis of the technique at 2 years

Energy Technology Data Exchange (ETDEWEB)

Thienpont, M [Ghent Rijksuniversiteit (Belgium). Kliniek voor Radiotherapie en Kerngeneeskunde; Van Eijkeren, M; Van Hecke, H; Boterberg, T; De Neve, W

1995-12-01

A total of 154 applications was analysed using a pulsed dose brachytherapy technique for 138 patients over a 2 year period with emphasis on technical aspects influencing the overall treatment time. Vaginal ovoids were used in 59 cases, plastic tubes in 52, a Fletcher-type in 18, vaginal cylinders in 14 and a perineal template in 11 cases. Pulses were given at hourly intervals with a median dose rate of 0.6 Gy per pulse (range 0.4 to 3 Gy). The number of pulses per application varied from 3 to 134 (median 32). The number of dwell positions varied from 1 to 542 over 1 to 18 catheters. Patient related problems were few. The room was entered almost every 77 minutes. We noted 561 status codes in 147 applications. Of the 25 different codes, the most frequent one was due to the door left open when a pulse had to be given (35%) or due to constriction of the plastic catheters at the transfer tube junction (26%). However, the median total treatment time was increased by only 5 minutes. With pulsed dose rate brachytherapy at hourly pulses we can treat our patients within the planned time despite frequent room entrance and occurrence of an appreciable number of status codes. This technique seems to fulfill its promise to replace low dose rate brachytherapy.

Time-dependent preparation of gelatin-stabilized silver nanoparticles by pulsed Nd:YAG laser

Science.gov (United States)

Darroudi, Majid; Ahmad, M. B.; Zamiri, Reza; Abdullah, A. H.; Ibrahim, N. A.; Sadrolhosseini, A. R.

2011-03-01

Colloidal silver nanoparticles (Ag-NPs) were successfully prepared using a nanosecond pulsed Nd:YAG laser, λ = 1064 nm, with laser fluence of approximately about 360 mJ/pulse, in an aqueous gelatin solution. In this work, gelatin was used as a stabilizer, and the size and optical absorption properties of samples were studied as a function of the laser ablation times. The results from the UV-vis spectroscopy demonstrated that the mean diameter of Ag-NPs decrease as the laser ablation time increases. The Ag-NPs have mean diameters ranging from approximately 10 nm to 16 nm. Compared with other preparation methods, this work is clean, rapid, and simple to use.

Time-of-flight diffraction at pulsed neutron sources: An introduction to the symposium

International Nuclear Information System (INIS)

Jorgensen, J.D.

1994-01-01

In the 25 years since the first low-power demonstration experiments, pulsed neutron sources have become as productive as reactor sources for many types of diffraction experiments. The pulsed neutron sources presently operating in the United States, England, and Japan offer state of the art instruments for powder and single crystal diffraction, small angle scattering, and such specialized techniques as grazing-incidence neutron reflection, as well as quasielastic and inelastic scattering. In this symposium, speakers review the latest advances in diffraction instrumentation for pulsed neutron sources and give examples of some of the important science presently being done. In this introduction to the symposium, I briefly define the basic principles of pulsed neutron sources, review their development, comment in general terms on the development of time-of-flight diffraction instrumentation for these sources, and project how this field will develop in the next ten years

Development of the pulse transformer for NLC klystron pulse modulator

International Nuclear Information System (INIS)

Akemoto, M.; Gold, S.; Koontz, R.; Krasnykh, A.

1997-05-01

We have studied a conventional pulse transformer for the NLC klystron pulse modulator. The transformer has been analyzed using a simplified lumped circuit model. It is found that a fast rise time requires low leakage inductance and low distributed capacitance and can be realized by reducing the number of secondary turns, but it produces larger pulse droop and core size. After making a tradeoff among these parameters carefully, a conventional pulse transformer with a rise time of 250ns and pulse droop of 3.6% has been designed and built. The transmission characteristics and pulse time-response were measured. The data were compared with the model. The agreement with the model was good when the measured values were used in the model simulation. The results of the high voltage tests are also presented

Digital coherent detection research on Brillouin optical time domain reflectometry with simplex pulse codes

International Nuclear Information System (INIS)

Hao Yun-Qi; Ye Qing; Pan Zheng-Qing; Cai Hai-Wen; Qu Rong-Hui

2014-01-01

The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry (BOTDR), where the simplex pulse codes are applied in the sensing system. The time domain signal of every code sequence is collected by the data acquisition card (DAQ). A shift-averaging technique is applied in the frequency domain for the reason that the local oscillator (LO) in the coherent detection is fix-frequency deviated from the primary source. With the 31-bit simplex code, the signal-to-noise ratio (SNR) has 3.5-dB enhancement with the same single pulse traces, accordant with the theoretical analysis. The frequency fluctuation for simplex codes is 14.01 MHz less than that for a single pulse as to 4-m spatial resolution. The results are believed to be beneficial for the BOTDR performance improvement. (general)

Intrinsic and cosmological signatures in gamma-ray burst time profiles: Time dilation

Energy Technology Data Exchange (ETDEWEB)

Lee, A.

2000-02-08

The time profiles of many gamma-ray bursts consist of distinct pulses, which offers the possibility of characterizing the temporal structure of these bursts using a relatively small set of pulse shape parameters. The authors have used a pulse decomposition procedure to analyze the Time-to-Spill (TTS) data for all bursts observed by BATSE up through trigger number 2000, in all energy channels for which TTS data is available. The authors obtain amplitude, rise and decay timescales, a pulse shape parameter, and the fluencies of individual pulses in all of the bursts. The authors investigate the correlations between brightness measures (amplitude and fluence) and timescale measures (pulse width and separation) which may result from cosmological time dilation of bursts, or from intrinsic properties of burst sources or from selection effects. The effects of selection biases are evaluated through simulations. The correlations between these parameters among pulses within individual bursts give a measure of the intrinsic effects while the correlations among bursts could result both from intrinsic and cosmological effects. The authors find that timescales tend to be shorter in bursts with higher peak fluxes, as expected from cosmological time dilation effects, but also find that there are non-cosmological effects contributing to this inverse correlation. The authors find that timescales tend to be longer in bursts with higher total fluences, contrary to what is expected from cosmological effects. The authors also find that peak fluxes and total fluences of bursts are uncorrelated, indicating that they cannot both be good distance indicators for bursts.

Time-resolved plasma spectroscopy of thin foils heated by a relativistic-intensity short-pulse laser

International Nuclear Information System (INIS)

Audebert, P.; Gauthier, J.-C.; Shepherd, R.; Fournier, K.B.; Price, D.; Lee, R.W.; Springer, P.; Peyrusse, O.; Klein, L.

2002-01-01

Time-resolved K-shell x-ray spectra are recorded from sub-100 nm aluminum foils irradiated by 150-fs laser pulses at relativistic intensities of Iλ 2 =2x10 18 W μm 2 /cm 2 . The thermal penetration depth is greater than the foil thickness in these targets so that uniform heating takes place at constant density before hydrodynamic motion occurs. The high-contrast, high-intensity laser pulse, broad spectral band, and short time resolution utilized in this experiment permit a simplified interpretation of the dynamical evolution of the radiating matter. The observed spectrum displays two distinct phases. At early time, ≤500 fs after detecting target emission, a broad quasicontinuous spectral feature with strong satellite emission from multiply excited levels is seen. At a later time, the He-like resonance line emission is dominant. The time-integrated data is in accord with previous studies with time resolution greater than 1 ps. The early time satellite emission is shown to be a signature of an initial large area, high density, low-temperature plasma created in the foil by fast electrons accelerated by the intense radiation field in the laser spot. We conclude that, because of this early time phenomenon and contrary to previous predictions, a short, high-intensity laser pulse incident on a thin foil does not create a uniform hot and dense plasma. The heating mechanism has been studied as a function of foil thickness, laser pulse length, and intensity. In addition, the spectra are found to be in broad agreement with a hydrodynamic expansion code postprocessed by a collisional-radiative model based on superconfiguration average rates and on the unresolved transition array formalism

Pulse transformer R and D for NLC klystron pulse modulator

International Nuclear Information System (INIS)

Akemoto, M.; Gold, S.; Krasnykh, A.; Koontz, R.

1997-07-01

The authors have studied a conventional pulse transformer for the NLC klystron pulse modulator. The transformer has been analyzed using a simplified lumped circuit model. It is found that a fast rise time requires low leakage inductance and low distributed capacitance and can be realized by reducing the number of secondary turns, but it produces larger pulse droop and requires a larger core size. After making a tradeoff among these parameters carefully, a conventional pulse transformer with a rise time of 250ns and a pulse droop of 3.6% has been designed and built. The transmission characteristics and pulse time-response were measured. The data were compared with the model. The agreement with the model was good when the measured values were used in the model simulation. The results of the high voltage tests using a klystron load are also presented

Fiber Optical Parametric Chirped Pulse Amplification of Sub-Picosecond Pulses

DEFF Research Database (Denmark)

Cristofori, Valentina; Lali-Dastjerdi, Zohreh; Da Ros, Francesco

2013-01-01

We demonstrate experimentally, for the first time to our knowledge, fiber optical parametric chirped pulse amplification of 400-fs pulses. The 400-fs signal is stretched, amplified by 26 dB and compressed back to 500 fs.......We demonstrate experimentally, for the first time to our knowledge, fiber optical parametric chirped pulse amplification of 400-fs pulses. The 400-fs signal is stretched, amplified by 26 dB and compressed back to 500 fs....

Evaluation of real-time digital pulse shapers with various HPGe and silicon radiation detectors

International Nuclear Information System (INIS)

Menaa, N.; D'Agostino, P.; Zakrzewski, B.; Jordanov, V.T.

2011-01-01

Real-time digital pulse shaping techniques allow synthesis of pulse shapes that have been difficult to realize using the traditional analog methods. Using real-time digital shapers, triangular/trapezoidal filters can be synthesized in real time. These filters exhibit digital control on the rise time, fall time, and flat-top of the trapezoidal shape. Thus, the trapezoidal shape can be adjusted for optimum performance at different distributions of the series and parallel noise. The trapezoidal weighting function (WF) represents the optimum time-limited pulse shape when only parallel and series noises are present in the detector system. In the presence of 1/F noise, the optimum WF changes depending on the 1/F noise contribution. In this paper, we report on the results of the evaluation of new filter types for processing signals from CANBERRA high purity germanium (HPGe) and passivated, implanted, planar silicon (PIPS) detectors. The objective of the evaluation is to determine improvements in performance over the current trapezoidal (digital) filter. The evaluation is performed using a customized CANBERRA digital signal processing unit that is fitted with new FPGA designs and any required firmware modifications to support operation of the new filters. The evaluated filters include the Cusp, one-over-F (1/F), and pseudo-Gaussian filters. The results are compared with the CANBERRA trapezoidal shaper.

Pulse frequency in pulsed brachytherapy based on tissue repair kinetics

International Nuclear Information System (INIS)

Sminia, Peter; Schneider, Christoph J.; Koedooder, Kees; Tienhoven, Geertjan van; Blank, Leo E.C.M.; Gonzalez Gonzalez, Dionisio

1998-01-01

Purpose: Investigation of normal tissue sparing in pulsed brachytherapy (PB) relative to continuous low-dose rate irradiation (CLDR) by adjusting pulse frequency based on tissue repair characteristics. Method: Using the linear quadratic model, the relative effectiveness (RE) of a 20 Gy boost was calculated for tissue with an α/β ratio ranging from 2 to 10 Gy and a half-time of sublethal damage repair between 0.1 and 3 h. The boost dose was considered to be delivered either in a number of pulses varying from 2 to 25, or continuously at a dose rate of 0.50, 0.80, or 1.20 Gy/h. Results: The RE of 20 Gy was found to be identical for PB in 25 pulses of 0.80 Gy each h and CLDR delivered at 0.80 Gy/h for any α/β value and for a repair half-time > 0.75 h. When normal tissue repair half-times are assumed to be longer than tumor repair half-times, normal tissue sparing can be obtained, within the restriction of a fixed overall treatment time, with higher dose per pulse and longer period time (time elapsed between start of pulse n and start of pulse n + 1). An optimum relative normal tissue sparing larger than 10% was found with 4 pulses of 5 Gy every 8 h. Hence, a therapeutic gain might be obtained when changing from CLDR to PB by adjusting the physical dose in such a way that the biological dose on the tumor is maintained. The normal tissue-sparing phenomenon can be explained by an increase in RE with longer period time for tissue with high α/β ratio and fast or intermediate repair half-time, and the RE for tissue with low α/β ratio and long repair half-time remains almost constant. Conclusion: Within the benchmark of the LQ model, advantage in normal tissue-sparing is expected when matching the pulse frequency to the repair kinetics of the normal tissue exposed. A period time longer than 1 h may lead to a reduction of late normal tissue complications. This theoretical advantage emphasizes the need for better knowledge of human tissue-repair kinetics

The Dynamic Method for Time-of-Flight Measurement of Thermal Neutron Spectra from Pulsed Sources

International Nuclear Information System (INIS)

Pepelyshev, Yu.N.; Tulaev, A.B.; Bobrakov, V.F.

1994-01-01

The time-of-flight method for a measurement of thermal neutron spectra in the pulsed neutron sources with high efficiency of neutron registration, more than 10 5 times higher in comparison with traditional one, is described. The main problems connected with the electric current technique for time-of-flight spectra measurement are examined. The methodical errors, problems of a special neutron detector design and other questions are discussed. Some experimental results, spectra from surfaces of the water and solid methane moderators, obtained in the pulsed reactor IBR-2 (Dubna, Russia) are presented. 4 refs., 5 figs

SU-E-T-501: Normal Tissue Toxicities of Pulsed Low Dose Rate Radiotherapy and Conventional Radiotherapy: An in Vivo Total Body Irradiation Study

Energy Technology Data Exchange (ETDEWEB)

Cvetkovic, D; Zhang, P; Wang, B; Chen, L; Ma, C [Fox Chase Cancer Center, Philadelphia, PA (United States)

2014-06-01

Purpose: Pulsed low dose rate radiotherapy (PLDR) is a re-irradiation technique for therapy of recurrent cancers. We have previously shown a significant difference in the weight and survival time between the mice treated with conventional radiotherapy (CRT) and PLDR using total body irradiation (TBI). The purpose of this study was to investigate the in vivo effects of PLDR on normal mouse tissues.Materials and Methods: Twenty two male BALB/c nude mice, 4 months of age, were randomly assigned into a PLDR group (n=10), a CRT group (n=10), and a non-irradiated control group (n=2). The Siemens Artiste accelerator with 6 MV photon beams was used. The mice received a total of 18Gy in 3 fractions with a 20day interval. The CRT group received the 6Gy dose continuously at a dose rate of 300 MU/min. The PLDR group was irradiated with 0.2Gyx20 pulses with a 3min interval between the pulses. The mice were weighed thrice weekly and sacrificed 2 weeks after the last treatment. Brain, heart, lung, liver, spleen, gastrointestinal, urinary and reproductive organs, and sternal bone marrow were removed, formalin-fixed, paraffin-embedded and stained with H and E. Morphological changes were observed under a microscope. Results: Histopathological examination revealed atrophy in several irradiated organs. The degree of atrophy was mild to moderate in the PLDR group, but severe in the CRT group. The most pronounced morphological abnormalities were in the immune and hematopoietic systems, namely spleen and bone marrow. Brain hemorrhage was seen in the CRT group, but not in the PLDR group. Conclusions: Our results showed that PLDR induced less toxicity in the normal mouse tissues than conventional radiotherapy for the same dose and regimen. Considering that PLDR produces equivalent tumor control as conventional radiotherapy, it would be a good modality for treatment of recurrent cancers.

High amplitude ultrasound pulse generation using time-reversal through a multiple scattering medium

OpenAIRE

ARNAL , Bastien; Pernot , Mathieu; Fink , Mathias; Tanter , Mickaël

2012-01-01

International audience; In histotripsy, soft tissues can be fragmented using very high pressure ultrasound pulses. Using time-reversal cavity is a way to generate high pressure pulses with a limited number of acoustic sources. The principle was already demonstrated by Montaldo et al. using a solid metal cavity, but low transmission coefficient was obtained due to the strong impedance mismatch at the metal/water interface. We propose here to use a waveguide filled with water containing a 2D mu...

Level crossings and excess times due to a superposition of uncorrelated exponential pulses

Science.gov (United States)

Theodorsen, A.; Garcia, O. E.

2018-01-01

A well-known stochastic model for intermittent fluctuations in physical systems is investigated. The model is given by a superposition of uncorrelated exponential pulses, and the degree of pulse overlap is interpreted as an intermittency parameter. Expressions for excess time statistics, that is, the rate of level crossings above a given threshold and the average time spent above the threshold, are derived from the joint distribution of the process and its derivative. Limits of both high and low intermittency are investigated and compared to previously known results. In the case of a strongly intermittent process, the distribution of times spent above threshold is obtained analytically. This expression is verified numerically, and the distribution of times above threshold is explored for other intermittency regimes. The numerical simulations compare favorably to known results for the distribution of times above the mean threshold for an Ornstein-Uhlenbeck process. This contribution generalizes the excess time statistics for the stochastic model, which find applications in a wide diversity of natural and technological systems.

Generation of pulsed far-infrared radiation and its application for far-infrared time-resolved spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Kondo, Yasuhiro [Tohoku Univ., Sendai (Japan). Faculty of Engineering

1996-07-01

So-called time-resolved spectroscopy technique has been used from old time as the means for studying the dynamic optical property, light-induced reaction and so on of matters. As an example, there is the method called pump and probe, and here, the wavelength of this probe light is the problem. If the object energy region is limited to about 0.1 eV, fast time-resolved spectroscopy is feasible relatively easily. However, energy region is extended to low energy region, the light source which is available as the pulsed probe light having sufficient intensity is limited. In this paper, the attempt of time-resolved spectroscopy utilizing coherent radiation, which has ended in failure, and the laser pulse-induced far-infrared radiation which can be utilized as new far-infrared probe light are reported. The reason why far-infrared radiation is used is explained. The attempt of time-resolved spectroscopy using NaCl crystals is reported on the equipment, the method of measuring absorption spectra and the results. Laser pulse-induced far-infrared radiation and the method of generating it are described. The multi-channel detector for far-infrared radiation which was made for trial is shown. (K.I.)

Electric field measurements in a dielectric barrier nanosecond pulse discharge with sub-nanosecond time resolution

International Nuclear Information System (INIS)

Goldberg, Benjamin M; Shkurenkov, Ivan; Adamovich, Igor V; Lempert, Walter R; O’Byrne, Sean

2015-01-01

The paper presents the results of time-resolved electric field measurements in a nanosecond discharge between two plane electrodes covered by dielectric plates, using picosecond four-wave mixing diagnostics. For absolute calibration, the IR signal was measured in hydrogen at a pressure of 440 Torr, for electrostatic electric field ranging from 0 to 8 kV cm −1 . The calibration curve (i.e. the square root of IR signal intensity versus electric field) was shown to be linear. By measuring the intensities of the pump, Stokes, and IR signal beam for each laser shot during the time sweep across the high-voltage pulse, temporal evolution of the electric field in the nanosecond pulse discharge was determined with sub-nanosecond time resolution. The results are compared to kinetic modeling predictions, showing good agreement, including non-zero electric field offset before the main high voltage pulse, breakdown moment, and reduction of electric field in the plasma after breakdown. The difference between the experimental results and model predictions is likely due to non-1D structure of the discharge. Comparison with the kinetic modeling predictions shows that electric field in the nanosecond pulse discharge is controlled primarily by electron impact excitation and charge accumulation on the dielectric surfaces. (paper)

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

International Nuclear Information System (INIS)

Bolton, P.R.

1987-06-01

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

Pulse processing routines for neutron time-of-flight data

CERN Document Server

Žugec, P; Guerrero, C; Gunsing, F; Vlachoudis, V; Sabate-Gilarte, M; Stamatopoulos, A; Wright, T; Lerendegui-Marco, J; Mingrone, F; Ryan, J A; Warren, S G; Tsinganis, A; Barbagallo, M

2016-01-01

A pulse shape analysis framework is described, which was developed for n_TOF-Phase3, the third phase in the operation of the n_TOF facility at CERN. The most notable feature of this new framework is the adoption of generic pulse shape analysis routines, characterized by a minimal number of explicit assumptions about the nature of pulses. The aim of these routines is to be applicable to a wide variety of detectors, thus facilitating the introduction of the new detectors or types of detectors into the analysis framework. The operational details of the routines are suited to the specific requirements of particular detectors by adjusting the set of external input parameters. Pulse recognition, baseline calculation and the pulse shape fitting procedure are described. Special emphasis is put on their computational efficiency, since the most basic implementations of these conceptually simple methods are often computationally inefficient.

Evaluation of bipolar pulse generator for high-purity pulsed ion beam

International Nuclear Information System (INIS)

Ito, H.; Kitamura, I.; Masugata, K.

2008-01-01

A new type of pulsed ion beam accelerator named 'bipolar pulse accelerator (BPA)' has been proposed in order to improve the purity of intense pulsed ion beams. To confirm the principle of the BPA, we developed a bipolar pulse generator, which consists of a Marx generator and a pulse forming line (PFL) with a rail gap switch on its end. In this article, we report the experimental results of the bipolar pulse and evaluate the electrical characteristics of the bipolar pulse generator. When the bipolar pulse generator was operated at 70% of the full charge condition of the PEL, the bipolar pulse with the first (-138 kV, 72 ns) and the second pulse (+130 kV, 70 ns) was successfully obtained. The evaluation of the electrical characteristics indicates that the developed generator can produce the bipolar pulse with fast rise time and sharp reversing time. At present the bipolar pulse generator is installed in the B y type magnetically insulated ion diode and we carry out the experiment on the production of an intense pulsed ion beam by the bipolar pulse accelerator. (author)

Pulsed neutron generator for use with pulsed neutron activation techniques

International Nuclear Information System (INIS)

Rochau, G.E.

1980-01-01

A high-output, transportable, pulsed neutron generator has been developed by Sandia National Laboratories for use with Pulsed Neutron Activation (PNA) techniques. The PNA neutron generator generates > 10 10 14 MeV D-T neutrons in a 1.2 millisecond pulse. Each operation of the unit will produce a nominal total neutron output of 1.2 x 10 10 neutrons. The generator has been designed to be easily repaired and modified. The unit requires no additional equipment for operation or measurement of output

Time resolved studies of H{sub 2}{sup +} dissociation with phase-stabilized laser pulses

Energy Technology Data Exchange (ETDEWEB)

Fischer, Bettina

2010-06-23

In the course of this thesis, experimental studies on the dissociation of H{sub 2}{sup +}(H{sub 2}{sup +}{yields}p+H) in ultrashort laser pulses with a stabilized carrier-envelope phase (CEP) were carried out. In single-pulse measurements, the ability to control the emission direction of low energetic protons, i.e. the localization of the bound electron at one of the nuclei after dissociation, by the CEP was demonstrated. The coincident detection of the emitted protons and electrons and the measurement of their three-dimensional momentum vectors with a reaction microscope allowed to clarify the localization mechanism. Further control was achieved by a pump-control scheme with two timedelayed CEP-stabilized laser pulses. Here the neutral H{sub 2} molecule was ionized in the first pulse and dissociation was induced by the second pulse. Electron localization was shown to depend on the properties of the bound nuclear wave packet in H{sub 2}{sup +} at the time the control pulse is applied, demonstrating the ability to use the shape and dynamics of the nuclear wave packet as control parameters. Wave packet simulations were performed reproducing qualitatively the experimental results of the single and the two-pulse measurements. For both control schemes, intuitive models are presented, which qualitatively explain the main features of the obtained results. (orig.)

Time-domain simulation and waveform reconstruction for shielding effectiveness of materials against electromagnetic pulse

International Nuclear Information System (INIS)

Hu, Xiao-feng; Chen, Xiang; Wei, Ming

2013-01-01

Shielding effectiveness (SE) of materials of current testing standards is often carried out by using continuous-wave measurement and amplitude-frequency characteristics curve is used to characterize the results. However, with in-depth study of high-power electromagnetic pulse (EMP) interference, it was discovered that only by frequency-domain SE of materials cannot be completely characterized by shielding performance of time-domain pulsed-field. And there is no uniform testing methods and standards of SE of materials against EMP. In this paper, the method of minimum phase transfer function is used to reconstruct shielded time-domain waveform based on the analysis of the waveform reconstruction method. Pulse of plane waves through an infinite planar material is simulated by using CST simulation software. The reconstructed waveform and simulation waveform is compared. The results show that the waveform reconstruction method based on the minimum phase can be well estimated EMP waveform through the infinite planar materials.

Time dependence of X-ray polarizability of a crystal induced by an intense femtosecond X-ray pulse

Directory of Open Access Journals (Sweden)

A. Leonov

2014-11-01

Full Text Available The time evolution of the electron density and the resulting time dependence of Fourier components of the X-ray polarizability of a crystal irradiated by highly intense femtosecond pulses of an X-ray free-electron laser (XFEL is investigated theoretically on the basis of rate equations for bound electrons and the Boltzmann equation for the kinetics of the unbound electron gas. The photoionization, Auger process, electron-impact ionization, electron–electron scattering and three-body recombination have been implemented in the system of rate equations. An algorithm for the numerical solution of the rate equations was simplified by incorporating analytical expressions for the cross sections of all the electron configurations in ions within the framework of the effective charge model. Using this approach, the time dependence of the inner shell populations during the time of XFEL pulse propagation through the crystal was evaluated for photon energies between 4 and 12 keV and a pulse width of 40 fs considering a flux of 1012 photons pulse−1 (focusing on a spot size of ∼1 µm. This flux corresponds to a fluence ranging between 0.8 and 2.4 mJ µm−2. The time evolution of the X-ray polarizability caused by the change of the atomic scattering factor during the pulse propagation is numerically analyzed for the case of a silicon crystal. The time-integrated polarizability drops dramatically if the fluence of the X-ray pulse exceeds 1.6 mJ µm−2.

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

International Nuclear Information System (INIS)

Huang Ziping; Wang Huacen; Deng Jianjun

2002-01-01

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

Formation of low time-bandwidth product, single-sided exponential optical pulses in free-electron laser oscillators

NARCIS (Netherlands)

MacLeod, A. M.; Yan, X.; Gillespie, W. A.; Knippels, G.M.H.; Oepts, D.; van der Meer, A. F. G.; Rella, C. W.; Smith, T. J.; Schwettman, H. A.

2000-01-01

The detailed shape of picosecond optical pulses from a free-electron laser (FEL) oscillator has been studied for various cavity detunings. For large values of the cavity detuning the optical pulse develops an exponential leading edge, with a time constant proportional to the applied cavity detuning

Electromagnetic pulse-driven spin-dependent currents in semiconductor quantum rings.

Science.gov (United States)

Zhu, Zhen-Gang; Berakdar, Jamal

2009-04-08

We investigate the non-equilibrium charge and spin-dependent currents in a quantum ring with a Rashba spin-orbit interaction (SOI) driven by two asymmetric picosecond electromagnetic pulses. The equilibrium persistent charge and persistent spin-dependent currents are investigated as well. It is shown that the dynamical charge and the dynamical spin-dependent currents vary smoothly with a static external magnetic flux and the SOI provides a SU(2) effective flux that changes the phases of the dynamic charge and the dynamic spin-dependent currents. The period of the oscillation of the total charge current with the delay time between the pulses is larger in a quantum ring with a larger radius. The parameters of the pulse fields control to a certain extent the total charge and the total spin-dependent currents. The calculations are applicable to nanometre rings fabricated in heterojunctions of III-V and II-VI semiconductors containing several hundreds of electrons.

Contrast Enhancement in TOF cerebral angiography at 7 T using Saturation and MT pulses under SAR constraints: impact of VERSE and sparse pulses

Science.gov (United States)

Schmitter, Sebastian; Bock, Michael; Johst, Sören; Auerbach, Edward J.; Uğurbil, Kâmil; Van de Moortele, Pierre-François

2011-01-01

Cerebral 3D time of flight (TOF) angiography significantly benefits from ultra high fields, mainly due to higher SNR and to longer T1 relaxation time of static brain tissues, however, SAR significantly increases with B0. Thus, additional RF pulses commonly used at lower field strengths to improve TOF contrast such as saturation of venous signal and improved background suppression by magnetization transfer typically cannot be used at higher fields. In this work we aimed at reducing SAR for each RF pulse category in a TOF sequence. We use the VERSE principle for the slab selective TOF excitation as well as the venous saturation RF pulses. Additionally, MT pulses are implemented by sparsely applying the pulses only during acquisition of the central k-space lines to limit their SAR contribution. Image quality, angiographic contrast and SAR reduction were investigated as a function of VERSE parameters and of the total number of MT pulses applied. Based on these results, a TOF protocol was generated that increases the angiographic contrast by more than 50% and reduces subcutaneous fat signal while keeping the resulting SAR within regulatory limits. PMID:22139829

An ion source for radiofrequency-pulsed glow discharge time-of-flight mass spectrometry

International Nuclear Information System (INIS)

González Gago, C.; Lobo, L.; Pisonero, J.; Bordel, N.; Pereiro, R.; Sanz-Medel, A.

2012-01-01

A Grimm-type glow discharge (GD) has been designed and constructed as an ion source for pulsed radiofrequency GD spectrometry when coupled to an orthogonal time of flight mass spectrometer. Pulse shapes of argon species and analytes were studied as a function of the discharge conditions using a new in-house ion source (UNIOVI GD) and results have been compared with a previous design (PROTOTYPE GD). Different behavior and shapes of the pulse profiles have been observed for the two sources evaluated, particularly for the plasma gas ionic species detected. In the more analytically relevant region (afterglow), signals for 40 Ar + with this new design were negligible, while maximum intensity was reached earlier in time for 41 (ArH) + than when using the PROTOTYPE GD. Moreover, while maximum 40 Ar + signals measured along the pulse period were similar in both sources, 41 (ArH) + and 80 (Ar 2 ) + signals tend to be noticeable higher using the PROTOTYPE chamber. The UNIOVI GD design was shown to be adequate for sensitive direct analysis of solid samples, offering linear calibration graphs and good crater shapes. Limits of detection (LODs) are in the same order of magnitude for both sources, although the UNIOVI source provides slightly better LODs for those analytes with masses slightly higher than 41 (ArH) + . - Highlights: ► A new RF-pulsed GD ion source (UNIOVI GD) coupled to TOFMS has been characterized. ► Linear calibration graphs and LODs in the low ppm range are achieved. ► Craters with flat bottoms and vertical walls are obtained. ► UNIOVI source can be easily cleaned as it does not require flow tube. ► UNIOVI GD has a simple design and thus its manufacture is easy and cheap.

Study of time-domain digital pulse shaping algorithms for nuclear signals

International Nuclear Information System (INIS)

Zhou Jianbin; Tuo Xianguo; Zhu Xing; Liu Yi; Zhou Wei; Lei Jiarong

2012-01-01

With the development on high-speed integrated circuit, fast high resolution sampling ADC and digital signal processors are replacing analog shaping amplifier circuit. This paper firstly presents the numerical analysis and simulation on R-C shaping circuit model and C-R shaping circuit model. Mathematic models are established based on 1 st order digital differential method and Kirchhoff Current Law in time domain, and a simulation and error evaluation experiment on an ideal digital signal are carried out with Excel VBA. A digital shaping test for a semiconductor X-ray detector in real time is also presented. Then a numerical analysis for Sallen-Key(S-K) low-pass filter circuit model is implemented based on the analysis of digital R-C and digital C-R shaping methods. By applying the 2 nd order non-homogeneous differential equation,the authors implement a digital Gaussian filter model for a standard exponential-decaying signal and a nuclear pulse signal. Finally, computer simulations and experimental tests are carried out and the results show the possibility of the digital pulse processing algorithms. (authors)

Pulse Rise Time Characterization of a High Pressure Xenon Gamma Detector for use in Resolution Enhancement

CERN Document Server

Troyer, G L

2000-01-01

High pressure xenon ionization chamber detectors are possible alternatives to traditional thallium doped sodium iodide (NaI(Tl)) and hyperpure germanium as gamma spectrometers in certain applications. Xenon detectors incorporating a Frisch grid exhibit energy resolutions comparable to cadmium/zinc/telluride (CZT) (e.g. 2% (at) 662keV) but with far greater sensitive volumes. The Frisch grid reduces the position dependence of the anode pulse risetimes, but it also increases the detector vibration sensitivity, anode capacitance, voltage requirements and mechanical complexity. We have been investigating the possibility of eliminating the grid electrode in high-pressure xenon detectors and preserving the high energy resolution using electronic risetime compensation methods. A two-electrode cylindrical high pressure xenon gamma detector coupled to time-to-amplitude conversion electronics was used to characterize the pulse rise time of deposited gamma photons. Time discrimination was used to characterize the pulse r...

Pulse Shape Tuning in Neutrino Detector Scintillator Systems

Energy Technology Data Exchange (ETDEWEB)

Aberle, Ch.; Buck, Ch.; Hartmann, F.X.; Schoenert, St. [Max Planck Institute for Nuclear Physics, Heidelberg (Germany); Hartmann, F.X. [Hartmann Scientific, City of Virginia Beach, Virginia (United States)

2009-07-01

Full text of publication follows: A new light yield model based on energy transfer pathways in codoped organic liquid scintillator systems is created and used to determine experimentally non-radiative energy transfer rate constants from which time dependent light pulse shapes and total light yields are predicted for multi-component liquids. Such constants determine effective Forster-Dexter critical concentrations. A surprising discovery regarding the critical concentration in n-dodecane permits tuning the pulse shape for different regions in the Double Chooz neutrino detector. (authors)

Time-resolved investigations of the fragmentation dynamic of H2 (D2) in and with ultra-short laser pulses

International Nuclear Information System (INIS)

Ergler, T.

2006-01-01

In course of this work pump-probe experiments aimed to study ultrafast nuclear motion in H 2 (D 2 ) fragmentation by intense 6-25 fs laser pulses have been carried out. In order to perform time-resolved measurements, a Mach-Zehnder interferometer providing two identical synchronized laser pulses with the time-delay variable from 0 to 3000 fs with 300 as accuracy and long-term stability has been built. The laser pulses at the intensities of up to 10 15 W/cm 2 were focused onto a H 2 (D 2 ) molecular beam leading to the ionization or dissociation of the molecules, and the momenta of all charged reactions fragments were measured with a reaction microscope. With 6-7 fs pulses it was possible to probe the time evolution of the bound H + 2 (D + 2 ) nuclear wave packet created by the first (pump) laser pulse, fragmenting the molecule with the second (probe) pulse. A fast delocalization, or ''collapse'', and subsequent ''revival'' of the vibrational wave packet have been observed. In addition, the signatures of the ground state vibrational excitation in neutral D 2 molecule have been found, and the dominance of a new, purely quantum mechanical wave packet preparation mechanism (the so-called ''Lochfrass'') has been proved. In the experiments with 25 fs pulses the theoretically predicted enhancement of the ionization probability for the dissociating H + 2 molecular ion at large internuclear distances has been detected for the first time. (orig.)

Laser-pulsed relativistic electron gun

International Nuclear Information System (INIS)

Sherman, N.K.

1986-01-01

A relativistic (β ≅ 0.8) electron gun with good emittance and subnanosecond pulse duration which can be synchronized to picosecond laser pulses is being developed at NRC for use in studies of particle acceleration by lasers. Bursts of electron pulses exceeding 280 keV in energy have been extracted into air form a laser-driven vacuum photodiode. Trains of 5 ps pulses of ultraviolet UV light illuminate a magnesium cathode. Photoelectrons emitted from the cathode are accelerated in a graded electrostatic potential set up by a 360 kV Marx-generator. The UV pulses are obtained by doubling the frequency of a 606 nm dye laser modelocked at 160 MHz. Electron energies were measured by residual range in an echelon of Al foils. Total charge per burst was measured by picoammeter. Time structure of the bursts has been examined with plastic scintillator and a fast photomultiplier. Tests on a low voltage photodiode achieved a current density of 180 A/cm/sup 2/ from an Mg cathode, with quantum efficiency of 2.4 x 10/sup -6/ electron per UV photon. The brevity and intensity of the laser pulses cause the electric charge collected per pulse to increase linearly with bias voltage rather than according to the Langmuir-Child law. Gun emittance is about 150 mm-msr and beam brightness is about 1A/cm/sup 2/-sr. Estimated duration of individual electron pulses of a burst is about 400 ps with instantaneous current of about 0.1 mA. Energy spread within one pulse is expected to be about 15%. This gun has the potential to be a useful source of relativistic electrons for laser acceleration studies

Time-dependent H-like and He-like Al lines produced by ultra-short pulse laser

Energy Technology Data Exchange (ETDEWEB)

Kato, Takako; Kato, Masatoshi [National Inst. for Fusion Science, Nagoya (Japan); Shepherd, R; Young, B; More, R; Osterheld, Al

1998-03-01

We have performed numerical modeling of time-resolved x-ray spectra from thin foil targets heated by the LLNL Ultra-short pulse (USP) laser. The targets were aluminum foils of thickness ranging from 250 A to 1250 A, heated with 120 fsec pulses of 400 nm light from the USP laser. The laser energy was approximately 0.2 Joules, focused to a 3 micron spot size for a peak intensity near 2 x 10{sup 19} W/cm{sup 2}. Ly{alpha} and He{alpha} lines were recorded using a 900 fsec x-ray streak camera. We calculate the effective ionization, recombination and emission rate coefficients including density effects for H-like and He-like aluminum ions using a collisional radiative model. We calculate time-dependent ion abundances using these effective ionization and recombination rate coefficients. The time-dependent electron temperature and density used in the calculation are based on an analytical model for the hydrodynamic expansion of the target foils. During the laser pulse the target is ionized. After the laser heating stops, the plasma begins to recombine. Using the calculated time dependent ion abundances and the effective emission rate coefficients, we calculate the time dependent Ly{alpha} and He{alpha} lines. The calculations reproduce the main qualitative features of the experimental spectra. (author)

Time Delayed Stage-Structured Predator-Prey Model with Birth Pulse and Pest Control Tactics

Directory of Open Access Journals (Sweden)

Mei Yan

2014-01-01

Full Text Available Normally, chemical pesticides kill not only pests but also their natural enemies. In order to better control the pests, two-time delayed stage-structured predator-prey models with birth pulse and pest control tactics are proposed and analyzed by using impulsive differential equations in present work. The stability threshold conditions for the mature prey-eradication periodic solutions of two models are derived, respectively. The effects of key parameters including killing efficiency rate, pulse period, the maximum birth effort per unit of time of natural enemy, and maturation time of prey on the threshold values are discussed in more detail. By comparing the two threshold values of mature prey-extinction, we provide the fact that the second control tactic is more effective than the first control method.

Magnetic pulse compression circuits for plasma devices

Energy Technology Data Exchange (ETDEWEB)

Georgescu, N; Zoita, V; Presura, R [Inst. of Physics and Technology of Radiation Devices, Bucharest (Romania)

1997-12-31

Two magnetic pulse compression circuits (MPCC), for two different plasma devices, are presented. The first is a 20 J/pulse, 3-stage circuit designed to trigger a low pressure discharge. The circuit has 16-18 kV working voltage, and 200 nF in each stage. The saturable inductors are realized with toroidal 25 {mu}m strip-wound cores, made of a Fe-Ni alloy, with 1.5 T saturation induction. The total magnetic volume is around 290 cm{sup 3}. By using a 25 kV/1 A thyratron as a primary switch, the time compression is from 3.5 {mu}s to 450 ns, in a short-circuit load. The second magnetic pulser is a 200 J/pulse circuit, designed to drive a high average power plasma focus soft X-ray source, for X-ray microlithography as the main application. The 3-stage pulser should supply a maximum load current of 100 kA with a rise-time of 250 - 300 ns. The maximum pulse voltage applied on the plasma discharge chamber is around 20 - 25 kV. The three saturable inductors in the circuit are made of toroidal strip-wound cores with METGLAS 2605 CO amorphous alloy as the magnetic material. The total, optimized mass of the magnetic material is 34 kg. The maximum repetition rate is limited at 100 Hz by the thyratron used in the first stage of the circuit, the driver supplying to the load about 20 kW average power. (author). 1 tab., 3 figs., 3 refs.

Interleaved wide and narrow pulses for the KAON factory 1 MHz chopper

International Nuclear Information System (INIS)

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

1993-01-01

A beam chopper is required in the transfer line between the 1 GeV/c TRIUMF cyclotron and the Accumulator ring of the proposed 30 GeV/c KAON Factory synchrotron. The beam chopper must generate pulses with a magnitude of at least 9.5 kV with rise and fall times of less than 38 ns (corresponds to kick rise/fall time of less than 39 ns) at a repetition rate of 10 6 pulses per second at a 100% duty cycle. The pulse pattern must be synchronized to the 23 MHz RF system for the TRIUMF cyclotron. Two different pulse widths are required to deflect a total of 5 beam bursts out of every 45 beam bursts that are extracted from the cyclotron. The inter-leaved pulses will have flattop durations of more than 48 ns and 92 ns. Results of measurements on a prototype chopper are presented where pulses of two different widths are synchronized to an RF synthesizer and stored in a low loss delay cable. Rise and fall times of 20 ns to 40 ns have been achieved with 12 kV to 15 kV wide and narrow pulses at 1.9 x 10 6 pulses per second continuous operation

A 16-channel real-time digital processor for pulse-shape discrimination in multiplicity assay

International Nuclear Information System (INIS)

Joyce, Malcolm J.; Aspinall, M.D.; Cave, F.D.; Lavietes, A.

2013-06-01

In recent years, real-time neutron/γ-ray pulse-shape discrimination has become feasible for use with scintillator-based detectors that respond extremely quickly, on the order of 25 ns in terms of pulse width, and their application to a variety of nuclear material assays has been reported. For the in-situ analysis of nuclear materials, measurements are often based on the multiplicity assessment of spontaneous fission events. An example of this is the 240 Pu eff assessment stemming from long-established techniques developed for 3 He-based neutron coincidence counters when 3 He was abundant and cheap. However, such measurements when using scintillator detectors can be plagued by low detection efficiencies and low orders of coincidence (often limited to triples) if the number of detectors in use is similarly limited to 3-4 detectors. Conversely, an array of >10 detector modules arranged to optimize efficiency and multiplicity sensitivity, shifts the emphasis in terms of performance requirement to the real-time digital analyzer and, critically, to the scope remaining in the temporal processing window of these systems. In this paper we report on the design, development and commissioning of a bespoke, 16-channel real-time pulse-shape discrimination analyzer specified for the materials assay challenge summarized above. The analyzer incorporates 16 dedicated and independent high-voltage supplies along with 16 independent digital processing channels offering pulse-shape discrimination at a rate of 3 x 10 6 events per second. These functions are configured from a dedicated graphical user interface, and all settings can be adjusted on-the-fly with the analyzer effectively configured one-time-only (where desired) for subsequent plug-and-play connection, for example to a fuel bundle organic scintillation detector array. (authors)

Total neutron cross section for 181Ta

Directory of Open Access Journals (Sweden)

Schilling K.-D.

2010-10-01

Full Text Available The neutron time of flight facility nELBE, produces fast neutrons in the energy range from 0.1 MeV to 10 MeV by impinging a pulsed relativistic electron beam on a liquid lead circuit [1]. The short beam pulses (∼10 ps and a small radiator volume give an energy resolution better than 1% at 1 MeV using a short flight path of about 6 m, for neutron TOF measurements. The present neutron source provides 2 ⋅ 104  n/cm2s at the target position using an electron charge of 77 pC and 100 kHz pulse repetition rate. This neutron intensity enables to measure neutron total cross section with a 2%–5% statistical uncertainty within a few days. In February 2008, neutron radiator, plastic detector [2] and data acquisition system were tested by measurements of the neutron total cross section for 181Ta and 27Al. Measurement of 181Ta was chosen because lack of high quality data in an anergy region below 700 keV. The total neutron cross – section for 27Al was measured as a control target, since there exists data for 27Al with high resolution and low statistical error [3].

PULSTRI-1 computer program for mixed core pulse calculation

International Nuclear Information System (INIS)

Ravnik, M.; Mele, I.; Dimic, V.

1990-01-01

PUISTRI-1 is a computer code designed for calculations of the pulse parameters of TRIGA Mark II reactor with mixed core. The code is provided with data for four types of fuel elements: standard 8.5 and 12 w/o, LEU and FLIP. The pulse parameters, such as maximum power, prompt pulse energy and average fuel temperatures are calculated in adiabatic point kinetics, approximation, modified by taking into account temperature dependence of fuel temperature reactivity coefficient and thermal capacity factor averaged over all elements in the core. Maximal fuel temperature at power peaking location is calculated from total released energy using total power peaking factor and heat capacity of the element at the location of the power peaking. Results of the code were compared to data found in references (mainly General Atomics safety analysis reports) showing good agreement for all main pulse parameters. The most important parameters, average and maximal fuel temperature, are found to be systematically slightly overpredicted (20 C and 50 C, respectively). Other parameters (energy, peak power, width) agree within ± 10 % to the reference values. The code is written in FORTRAN for IBM PC computer. The input is user friendly. running time of IBM PC AT is a few seconds. It is designed for practical applications in pulse experiments as an analytical tool for predicting pulse parameters. (orig.)

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

Science.gov (United States)

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

2014-11-14

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

Generation of an incident focused light pulse in FDTD.

Science.gov (United States)

Capoğlu, Ilker R; Taflove, Allen; Backman, Vadim

2008-11-10

A straightforward procedure is described for accurately creating an incident focused light pulse in the 3-D finite-difference time-domain (FDTD) electromagnetic simulation of the image space of an aplanatic converging lens. In this procedure, the focused light pulse is approximated by a finite sum of plane waves, and each plane wave is introduced into the FDTD simulation grid using the total-field/scattered-field (TF/SF) approach. The accuracy of our results is demonstrated by comparison with exact theoretical formulas.

Noncontact sphygmomanometer based on pulse-wave transit time between the face and hand

Science.gov (United States)

Nakano, Kazuya; Ohnishi, Takashi; Nishidate, Izumi; Haneishi, Hideaki

2018-02-01

Systolic blood pressure (SBP) is highly sensitive to various factors such as psychological stress, and hence its continuous monitoring is essential to evaluate different health conditions. However, conventional sphygmomanometers cannot continuously measure SBP given the time-consuming setup based on a pressure cuff. Moreover, continuous biological signal monitoring is more comfortable when no sensors are attached. A solution for continuous SBP estimation is based on pulse transit time (PTT), which determines the time difference between two pulse waves at different body parts. In previous studies, we successfully measured the PTT using a contactless setup composed by two digital color cameras recording the face and hand of subjects. Then, the acquired images were transformed into blood volume by combining multiple regression analysis and a Monte Carlo method. As a result, the delay among images allowed to determine the PPT from pulse waves. In this study, we simultaneously measured SBP and PTT by using a sphygmomanometer and the two cameras, respectively. We evaluated SBP increases (i.e., stressful situations) and the corresponding PPT by asking participants to either grasp a handgrip or momentarily interrupting breath. We also determined the SBP and PTT without asking for such exercises. Comparison results show that the mean PTT under stress was significantly lower than that without stress, which is consistent with an increased SBP. Finally, we related the SBP and PTT by a nonlinear formula with a coefficient of determination of 0.59, thus confirming the effectiveness of the proposed system.

A new possibility for production of sub-picosecond x-ray pulses using a time dependent radio frequency orbit deflection

Energy Technology Data Exchange (ETDEWEB)

Zholents, A.

2015-10-21

It is shown that two radio frequency deflecting cavities with slightly different frequencies can be used to produce time-dependent orbit deflection to a few special electron bunches circulating in a synchrotron without affecting the majority of the electron bunches. These special bunches produce an x-ray pulse in which transverse position or angle, or both, are correlated with time. The x-ray pulse is then shortened, either with an asymmetrically cut crystal that acts as a pulse compressor, or with an angular aperture such as a narrow slit positioned downstream. The implementation of this technique creates a highly flexible environment for synchrotrons in which users of most beamlines will be able to easily select between the x-rays originated by the standard electron bunches and the short x-ray pulses originated by the special electron bunches carrying a time-dependent transverse correlation.

A New Possibility for Production of Sub-picosecond X-ray Pulses using a Time Dependent Radio Frequency Orbit Deflection

Energy Technology Data Exchange (ETDEWEB)

Zholents, A. A. [Argonne National Lab. (ANL), Argonne, IL (United States)

2015-05-01

It is shown that two radio frequency deflecting cavities with slightly different frequencies can be used to produce time-dependent orbit deflection to a few special electron bunches while keeping the majority of the electron bunches unaffected. These special bunches produce an x-ray pulse in which transverse position or angle, or both, are correlated with time. The x-ray pulses are then shortened, either with an asymmetrically cut crystal that acts as a pulse compressor, or with an angular aperture such as a narrow slit positioned downstream. The implementation of this technique creates a highly flexible environment for synchrotrons in which users of most beamlines will be able to easily select between the x-rays originated by the standard electron bunches and the short x-ray pulses originated by the special electron bunches carrying a time-dependent transverse correlation.

Effect of heat-induced pain stimuli on pulse transit time and pulse wave amplitude in healthy volunteers.

Science.gov (United States)

van Velzen, Marit H N; Loeve, Arjo J; Kortekaas, Minke C; Niehof, Sjoerd P; Mik, Egbert G; Stolker, Robert J

2016-01-01

Pain is commonly assessed subjectively by interpretations of patient behaviour and/or reports from patients. When this is impossible the availability of a quantitative objective pain assessment tool based on objective physiological parameters would greatly benefit clinical practice and research beside the standard self-report tests. Vasoconstriction is one of the physiological responses to pain. The aim of this study was to investigate whether pulse transit time (PTT) and pulse wave amplitude (PWA) decrease in response to this vasoconstriction when caused by heat-induced pain. The PTT and PWA were measured in healthy volunteers, on both index fingers using photoplethysmography and electrocardiography. Each subject received 3 heat-induced pain stimuli using a Temperature-Sensory Analyzer thermode block to apply a controlled, increasing temperature from 32.0 °C to 50.0 °C to the skin. After reaching 50.0 °C, the thermode was immediately cooled down to 32.0 °C. The study population was divided into 2 groups with a time-interval between the stimuli 20s or 60s. The results showed a significant (p  Heat-induced pain causes a decrease of PTT and PWA. Consequently, it is expected that, in the future, PTT and PWA may be applied as objective indicators of pain, either beside the standard self-report test, or when self-report testing is impossible.

The concept of biologically motivated time-pulse information processing for design and construction of multifunctional devices of neural logic

Science.gov (United States)

Krasilenko, Vladimir G.; Nikolsky, Alexander I.; Lazarev, Alexander A.; Sholohov, V. I.

2004-04-01

On the basis of the analysis of advanced approaches and optoelectronic systems for realization of various logics: two-valued, multi-valued, neural, continuous and others the biologically motivated time-pulse conception for building of multifunctional reconfigurable universal elements with programmable tuning for neurobiologic is grounded. The concept consists in usage of preliminary conversion of multi-level or continuous optic 2D signals into durations of time intervals (the conversion to a temporal area) and further use of time-pulse two-level digital signals that allows to ensure fast tuning to a required function of two-valued, multi-valued and other logics. It is shown that optoelectronic pulse-phase and pulse-width modulators (PPM and PWM) are the base elements for that. Time-pulse coding universal elements for matrix two-valued and multi-valued logics and structural-functional design of universal time-pulse coding elements for neural (continuous) logic are considered in the article. PPMs realized on 1.5μm technology CMOS transistors are considered. The PPMs have parameters: the input photocurrent range is 10nA...10μA the conversion period is 10μs...1ms the conversion relative error is 0.1...1%; the conversion law is ramp; the supply voltage is 3V and the power consumption is 83μW. The small power consumption of such PPMs enables successfully their integration in 2Darray with size of 128x128 elements and more and productivity equals 1...10 Giga continuous logic operations per sec.

The Study for Shortening the Process Time at Soy Food Production by using the Pulsed Electric Field

Science.gov (United States)

Saito, Tsukasa; Jinushi, Makoto; Minamitani, Yasushi

We investigated method to osmose water and seasoner to dried soybeans fast by pulsed electric field, in order to make soybeans a processed food fast. By applying the pulsed electric field to the dried soybeans in water, osmosis time of water to the soybean became approximately half. Then the emission of the discharge was observed on dried soybean. The color of coffee permeated more into the soybean treated than no-treated by the pulsed electric field.

Advanced pulse oximeter signal processing technology compared to simple averaging. II. Effect on frequency of alarms in the postanesthesia care unit.

Science.gov (United States)

Rheineck-Leyssius, A T; Kalkman, C J

1999-05-01

To determine the effect of a new pulse oximeter (Nellcor Symphony N-3000, Pleasanton, CA) with signal processing technique (Oxismart) on the incidence of false alarms in the postanesthesia care unit (PACU). Prospective study. Nonuniversity hospital. 603 consecutive ASA physical status I, II, and III patients recovering from general or regional anesthesia in the PACU. We compared the number of alarms produced by a recently developed "third"-generation pulse oximeter (Nellcor Symphony N-3000) with Oxismart signal processing technique and a conventional pulse oximeter (Criticare 504, Waukesha, WI). Patients were randomly assigned to either a Nellcor pulse oximeter or a Criticare with the signal averaging time set at either 12 or 21 seconds. For each patient the number of false (artifact) alarms was counted. The Nellcor generated one false alarm in 199 patients and 36 (in 31 patients) "loss of pulse" alarms. The conventional pulse oximeter with the averaging time set at 12 seconds generated a total of 32 false alarms in 17 of 197 patients [compared with the Nellcor, relative risk (RR) 0.06, confidence interval (CI) 0.01 to 0.25] and a total of 172 "loss of pulse" alarms in 79 patients (RR 0.39, CI 0.28 to 0.55). The conventional pulse oximeter with the averaging time set at 21 seconds generated 12 false alarms in 11 of 207 patients (compared with the Nellcor, RR 0.09, CI 0.02 to 0.48) and a total of 204 "loss of pulse" alarms in 81 patients (RR 0.40, CI 0.28 to 0.56). The lower incidence of false alarms of the conventional pulse oximeter with the longest averaging time compared with the shorter averaging time did not reach statistical significance (false alarms RR 0.62, CI 0.3 to 1.27; "loss of pulse" alarms RR 0.98, CI 0.77 to 1.3). To date, this is the first report of a pulse oximeter that produced almost no false alarms in the PACU.

Reduced timing Sensitivity in all-optical switching using flat-top control pulses obtained by the optical fourier transform technique

DEFF Research Database (Denmark)

Oxenløwe, Leif Katsuo; Galili, Michael; Mulvad, Hans Christian Hansen

2006-01-01

into the time domain, referred to as the optical Fourier transform technique. A 3 ps flat-top pulse derived from a 3 nm wide square filter is obtained, and used to gate an all-optical OTDM demultiplexer, yielding an error-free timing jitter tolerance of 3 ps for 80 Gb/s and 160 Gb/s data signals.......For high-speed serial data, timing tolerance is crucial for switching and regeneration. We propose a novel scheme to generate flat-top pulses, for use as gating control pulses. The scheme relies on spectral shaping by a square-shaped filter, followed by a linear transformation of the spectral shape...

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

Directory of Open Access Journals (Sweden)

Xin Liu

2016-04-01

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

Random pulse generator

International Nuclear Information System (INIS)

Guo Ya'nan; Jin Dapeng; Zhao Dixin; Liu Zhen'an; Qiao Qiao; Chinese Academy of Sciences, Beijing

2007-01-01

Due to the randomness of radioactive decay and nuclear reaction, the signals from detectors are random in time. But normal pulse generator generates periodical pulses. To measure the performances of nuclear electronic devices under random inputs, a random generator is necessary. Types of random pulse generator are reviewed, 2 digital random pulse generators are introduced. (authors)

CAMAC differential pulse discriminator-counter

International Nuclear Information System (INIS)

Tselikov, N.V.

1987-01-01

Differential pulse discriminator-counter for Moessbauer spectrometer is described. Input pulse setting into the channel is performed according to the following algorithm: the pulse is transmitted to the channel depending on the fact whether the preceding pulse has got to the discrimination window or not. The circuit does not contain delay lines, taking into account the delay of a signal from the upper level discriminator in relation to the lower level discriminator signal, which is connected with input pulse rise finite time, which in turn allows one to reduce the discriminator dead time up to the operation time of threshold circuits. The pulse counting rate is 150 MHz, input signal amplitude is ±3 V, dead time is 6 ns, delay time from input to output is 14 ns. The unit is made in CAMAC system

Behavioral changes induced by single and multiple electron beam pulses

International Nuclear Information System (INIS)

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

1985-01-01

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

Time-resolved measurement of emission profiles in pulsed radiofrequency glow discharge optical emission spectroscopy: Investigation of the pre-peak

International Nuclear Information System (INIS)

Alberts, D.; Horvath, P.; Nelis, Th.; Pereiro, R.; Bordel, N.; Michler, J.; Sanz-Medel, A.

2010-01-01

Radiofrequency glow discharge coupled to optical emission spectroscopy has been used in pulsed mode in order to perform a detailed study of the measured temporal emission profiles for a wide range of copper transitions. Special attention has been paid to the early emission peak (or so-called pre-peak), observed at the beginning of the emission pulse profile. The effects of the important pulse parameters such as frequency, duty cycle, pulse width and power-off time, have been studied upon the Cu pulse emission profiles. The influence of discharge parameters, such as pressure and power, was studied as well. Results have shown that the intensity observed in the pre-peak can be 10 times as large as the plateau value for resonant lines and up to 5 times in case of transitions to the metastable levels. Increasing pressure or power increased the pre-peak intensity while its appearance in time changed. The pre-peak decreased when the discharge off-time was shorter than 100 μs. According to such results, the presence of the pre-peak could be probably due to the lack of self-absorption during the first 50 μs, and not to the ignition of the plasma. Under the selected operation conditions, the use of the pre-peak emission as analytical signals increases the linearity of calibration curves for resonant lines subjected to self-absorption at high concentrations.

Time-resolved measurement of emission profiles in pulsed radiofrequency glow discharge optical emission spectroscopy: Investigation of the pre-peak

Energy Technology Data Exchange (ETDEWEB)

Alberts, D. [Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julian Claveria 8, 33006 Oviedo (Spain); Horvath, P. [Swiss Federal Laboratories for Materials Testing and Research (EMPA), Feuerwerkerstrasse 39, 3602 Thun (Switzerland); Nelis, Th. [LAPLACE, Universite Paul Sabatier, 118 rte de Narbonne, Bat3R2, 31062 Toulouse Cedex (France); CU Jean Francois Champollion, Place de Verdun 81012 Albi Cedex 9 (France); Pereiro, R. [Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julian Claveria 8, 33006 Oviedo (Spain); Bordel, N. [Department of Physics, Faculty of Science, University of Oviedo, Calvo Sotelo, 33007 Oviedo (Spain); Michler, J. [Swiss Federal Laboratories for Materials Testing and Research (EMPA), Feuerwerkerstrasse 39, 3602 Thun (Switzerland); Sanz-Medel, A., E-mail: asm@uniovi.e [Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julian Claveria 8, 33006 Oviedo (Spain)

2010-07-15

Radiofrequency glow discharge coupled to optical emission spectroscopy has been used in pulsed mode in order to perform a detailed study of the measured temporal emission profiles for a wide range of copper transitions. Special attention has been paid to the early emission peak (or so-called pre-peak), observed at the beginning of the emission pulse profile. The effects of the important pulse parameters such as frequency, duty cycle, pulse width and power-off time, have been studied upon the Cu pulse emission profiles. The influence of discharge parameters, such as pressure and power, was studied as well. Results have shown that the intensity observed in the pre-peak can be 10 times as large as the plateau value for resonant lines and up to 5 times in case of transitions to the metastable levels. Increasing pressure or power increased the pre-peak intensity while its appearance in time changed. The pre-peak decreased when the discharge off-time was shorter than 100 {mu}s. According to such results, the presence of the pre-peak could be probably due to the lack of self-absorption during the first 50 {mu}s, and not to the ignition of the plasma. Under the selected operation conditions, the use of the pre-peak emission as analytical signals increases the linearity of calibration curves for resonant lines subjected to self-absorption at high concentrations.

Correlations between muons and low energy pulses at LSD of the Mont Blanc laboratory near the time of SN1987A explosion

International Nuclear Information System (INIS)

Dadykin, V.L.; Khalchukov, F.F.; Korchagin, P.V.; Korolkova, E.V.; Kudryavtsev, V.A.; Mal'gin, A.S.; Ryasny, V.G.; Ryazhskaya, O.G.; Yakushev, V.F.; Zatsepin, G.T.; Aglietta, M.; Badino, G.; Bologna, G.; Castagnoli, C.; Castellina, A.; Fulgione, W.; Galeotti, P.; Saavedra, O.; Trinchero, G.; Vernetto, S.; Turin Univ.

1989-01-01

We have analysed the data of LSD from February 10, 1987, to March 7, 1987, in order to search for autocorrelations between all pulses detected by LSD with energy higher than 5 MeV like those occurred at ∼ 3:00 UT on February 23, 1987, between the pulses detected by 3 neutrino telescopes and 2 gravitational wave antennae. We have found 9 pairs of correlated pulses (muon + low energy pulse) from 5:42 UT to 10:13 UT on February 23, 1987. The time differences of pulses in the pairs are less than 2 s, the first pulse in the pair being either muon or low energy pulse. The frequency of such random poissonian fluctuations is ∼1/(10 years). There are no correlations outside statistics between low energy, low energy pulses and muon, muon pulses detected by LSD during the whole time period

Device for Writing the Time Tail from Spallation Neutron Pulses

International Nuclear Information System (INIS)

Langan, P.; Schoenborn, Benno P.; Daemen, L.L.

2001-01-01

Recent work at Los Alamos Neutron Science Center (LANSCE), has shown that there are large gains in neutron beam intensity to be made by using coupled moderators at spallation neutron sources. Most of these gains result from broadening the pulse-width in time. However the accompanying longer exponential tail at large emission times can be a problem in that it introduces relatively large beam-related backgrounds at high resolutions. We have designed a device that can reshape the moderated neutron beam by cutting the time-tail so that a sharp time resolution can be re-established without a significant loss in intensity. In this work the basic principles behind the tail-cutter and some initial results of Monte Carlo simulations are described. Unwanted neutrons in the long time-tail are diffracted out of the transmitted neutron beam by a nested stack of aperiodic multi-layers, rocking at the same frequency as the source. Nested aperiodic multi-layers have recently been used at X-ray sources and as band-pass filters in quasi-Laue neutron experiments at reactor neutron sources. Optical devices that rock in synchronization with a pulsed neutron beam are relatively new but are already under construction at LANSCE. The tail-cutter described here is a novel concept that uses existing multi-layer technology in a new way for spallation neutrons. Coupled moderators in combination with beam shaping devices offer the means of increasing flux whilst maintaining a sharp time distribution. A prototype device is being constructed for the protein crystallography station at LANSCE. The protein crystallography station incorporates a water moderator that has been judiciously coupled in order to increase the flux over neutron energies that are important to structural biology (3-80meV). This development in moderator design is particularly important because protein crystallography is flux limited and because conventional ambient water and cold hydrogen moderators do not provide relatively

Effects of pulse duration on magnetostimulation thresholds

International Nuclear Information System (INIS)

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

2015-01-01

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

Time evolution of plasma potential in pulsed operation of ECRIS

International Nuclear Information System (INIS)

Tarvainen, O.; Koivisto, H.; Ropponen, T.; Toivanen, V.; Higurashi, Y.; Nakagawa, T.

2012-01-01

The time evolution of plasma potential has been measured with a retarding field analyzer in pulsed operation mode with electron cyclotron resonance ion sources at JYFL and RIKEN. Three different ion sources with microwave frequencies ranging from 6.4 to 18 GHz were employed for the experiments. The plasma potential was observed to increase 10-75 % during the Pre-glow and 10-30 % during the afterglow compared to steady state. The paper is followed by the slides of the presentation. (authors)

Pulsed time-of-flight refractometry measurements of the electron density in the T-11M tokamak

International Nuclear Information System (INIS)

Petrov, A.A.; Petrov, V.G.; Malyshev, A.Yu.; Markov, V.K.; Babarykin, A.V.

2002-01-01

A new method for measuring the plasma density in magnetic confinement systems - pulsed time-of-flight refractometry - is developed and tested experimentally in the T-11M tokamak. The method is based on the measurements of the time delay of short (with a duration of several nanoseconds) microwave pulses propagating through the plasma. When the probing frequency is much higher than the plasma frequency, the measured delay in the propagation time is proportional to the line-averaged electron density regardless of the density profile. A key problem in such measurements is the short time delay of the pulse in the plasma (∼1 ns or less for small devices) and, consequently, low accuracy of the measurements of the average density. Various methods for improving the accuracy of such measurements are proposed and implemented in the T-11M experiments. The measurements of the line-averaged density in the T-11M tokamak in the low-density plasma regime are performed. The results obtained agree satisfactorily with interferometric data. The measurement errors are analyzed, and the possibility of using this technique to measure the electron density profile and the position of the plasma column is discussed

An analyzer for pulse-interval times to study high-order effects in the processing of nuclear detector signals

International Nuclear Information System (INIS)

Denecke, B.; Jonge, S. de

1998-01-01

An electronic device to measure interval time density distributions of subsequent pulses in nuclear detectors and their electronics is described. The device has a pair-pulse resolution of 10 ns and 25 ns for 3 subsequent input signals. The conversion range is 4096 channels and the lowest channel width is 10 ns. Counter dead times, single and in series were studied and compared with the statistical model. True count rates were obtained from an exponential fit through the interval-time distribution

Time-based distribution of Staphylococcus saprophyticus pulsed field gel-electrophoresis clusters in community-acquired urinary tract infections

Directory of Open Access Journals (Sweden)

Viviane Santos de Sousa

2013-02-01

Full Text Available The epidemiology of urinary tract infections (UTI by Staphylococcus saprophyticus has not been fully characterised and strain typing methods have not been validated for this agent. To evaluate whether epidemiological relationships exist between clusters of pulsed field gel-electrophoresis (PFGE genotypes of S. saprophyticus from community-acquired UTI, a cross-sectional surveillance study was conducted in the city of Rio de Janeiro, Brazil. In total, 32 (16% female patients attending two walk-in clinics were culture-positive for S. saprophyticus. Five PFGE clusters were defined and evaluated against epidemiological data. The PFGE clusters were grouped in time, suggesting the existence of community point sources of S. saprophyticus. From these point sources, S. saprophyticus strains may spread among individuals.

Time resolved optical emission spectroscopy of cross-beam pulsed laser ablation on graphite targets

International Nuclear Information System (INIS)

Sangines, R.; Sanchez Ake, C.; Sobral, H.; Villagran-Muniz, M.

2007-01-01

Cross-beam pulsed laser ablation with two delayed lasers is performed on two perpendicular graphite targets. The time delay between lasers is varied by up to 5 μs, and physical changes on the second plasma, due to the interaction with the first generated one, are determined by time resolved optical emission spectroscopy

Effects of pulse duration on magnetostimulation thresholds

Energy Technology Data Exchange (ETDEWEB)

Saritas, Emine U., E-mail: saritas@ee.bilkent.edu.tr [Department of Bioengineering, University of California, Berkeley, Berkeley, California 94720-1762 (United States); Department of Electrical and Electronics Engineering, Bilkent University, Bilkent, Ankara 06800 (Turkey); National Magnetic Resonance Research Center (UMRAM), Bilkent University, Bilkent, Ankara 06800 (Turkey); Goodwill, Patrick W. [Department of Bioengineering, University of California, Berkeley, Berkeley, California 94720-1762 (United States); Conolly, Steven M. [Department of Bioengineering, University of California, Berkeley, Berkeley, California 94720-1762 (United States); Department of EECS, University of California, Berkeley, California 94720-1762 (United States)

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

Intra-Cavity Total Reflection For High Sensitivity Measurement Of Optical Properties

Science.gov (United States)

Pipino, Andrew Charles Rule

1999-11-16

An optical cavity resonator device is provided for conducting sensitive murement of optical absorption by matter in any state with diffraction-limited spatial resolution through utilization of total internal reflection within a high-Q (high quality, low loss) optical cavity. Intracavity total reflection generates an evanescent wave that decays exponentially in space at a point external to the cavity, thereby providing a localized region where absorbing materials can be sensitively probed through alteration of the Q-factor of the otherwise isolated cavity. When a laser pulse is injected into the cavity and passes through the evanescent state, an amplitude loss resulting from absorption is incurred that reduces the lifetime of the pulse in the cavity. By monitoring the decay of the injected pulse, the absorption coefficient of manner within the evanescent wave region is accurately obtained from the decay time measurement.

On scattering diagnostics with periodically pulsed lasers to follow the continuous evolution of time dependent plasma parameters

International Nuclear Information System (INIS)

Hellermann, M. von; Hirsch, K.; Doeble, H.F.

1977-04-01

The possibilities to use periodically pulsed lasers for plasma scattering diagnostics are discussed. An experiment with succesful application of a periodically pulsed frequency-doubled Nd:YAG laser is described and results are given. Application of the method to monitor continuously, with millisecond time resolution, parameters of Tokamak type plasmas, is considered. (orig.) [de

Multi-pulse chaotic motions of a rotor-active magnetic bearing system with time-varying stiffness

International Nuclear Information System (INIS)

Zhang, W.; Yao, M.H.; Zhan, X.P.

2006-01-01

In this paper, we investigate the Shilnikov type multi-pulse chaotic dynamics for a rotor-active magnetic bearings (AMB) system with 8-pole legs and the time-varying stiffness. The stiffness in the AMB is considered as the time-varying in a periodic form. The dimensionless equation of motion for the rotor-AMB system with the time-varying stiffness in the horizontal and vertical directions is a two-degree-of-freedom nonlinear system with quadratic and cubic nonlinearities and parametric excitation. The asymptotic perturbation method is used to obtain the averaged equations in the case of primary parametric resonance and 1/2 subharmonic resonance. It is found from the numerical results that there are the phenomena of the Shilnikov type multi-pulse chaotic motions for the rotor-AMB system. A new jumping phenomenon is discovered in the rotor-AMB system with the time-varying stiffness

An Improved Clutter Suppression Method for Weather Radars Using Multiple Pulse Repetition Time Technique

Directory of Open Access Journals (Sweden)

Yingjie Yu

2017-01-01

Full Text Available This paper describes the implementation of an improved clutter suppression method for the multiple pulse repetition time (PRT technique based on simulated radar data. The suppression method is constructed using maximum likelihood methodology in time domain and is called parametric time domain method (PTDM. The procedure relies on the assumption that precipitation and clutter signal spectra follow a Gaussian functional form. The multiple interleaved pulse repetition frequencies (PRFs that are used in this work are set to four PRFs (952, 833, 667, and 513 Hz. Based on radar simulation, it is shown that the new method can provide accurate retrieval of Doppler velocity even in the case of strong clutter contamination. The obtained velocity is nearly unbiased for all the range of Nyquist velocity interval. Also, the performance of the method is illustrated on simulated radar data for plan position indicator (PPI scan. Compared with staggered 2-PRT transmission schemes with PTDM, the proposed method presents better estimation accuracy under certain clutter situations.

Femtosecond time-resolved impulsive stimulated Raman spectroscopy using sub-7-fs pulses: Apparatus and applications

Energy Technology Data Exchange (ETDEWEB)

Kuramochi, Hikaru [Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198 (Japan); Takeuchi, Satoshi; Tahara, Tahei, E-mail: tahei@riken.jp [Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198 (Japan); Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), 2-1 Hirosawa, Wako 351-0198 (Japan)

2016-04-15

We describe details of the setup for time-resolved impulsive stimulated Raman spectroscopy (TR-ISRS). In this method, snapshot molecular vibrational spectra of the photoreaction transients are captured via time-domain Raman probing using ultrashort pulses. Our instrument features transform-limited sub-7-fs pulses to impulsively excite and probe coherent nuclear wavepacket motions, allowing us to observe vibrational fingerprints of transient species from the terahertz to 3000-cm{sup −1} region with high sensitivity. Key optical components for the best spectroscopic performance are discussed. The TR-ISRS measurements for the excited states of diphenylacetylene in cyclohexane are demonstrated, highlighting the capability of our setup to track femtosecond dynamics of all the Raman-active fundamental molecular vibrations.

A method to reduce the suppression of relevant pulses in pulse weight discriminators

International Nuclear Information System (INIS)

Schwartz, P.

1975-01-01

The pulse height analyzer is used, for instance, with proportional counters. Pulses are broken down into amplitude ranges in accordance with their maximum amplitudes. In pulse height analyzers with real time analog-digital conversion only one deadtime is needed for the respective range selected. For this purpose, all discriminator thresholds of the amplitude stores connected parallel are actuated as an input pulse arrives. The leading edges of the discriminator signals set the amplitude range flip-flop. Only the flip-flop circuit of the maximum amplitude range reached remains set whilst all the others are erased. The trailing edge of the discriminator signals actuates the evaluation of the information stored by the flip-flop circuit selected. It triggers a pulse extender and resets the flip-flop selected. Therefore, only the amplitude range selected needs a deadtime. The pulse extender in addition reduces the processing time of the analyzer by the output pulse length. The characteristic used for the trailing edge is the backward count of the real time analog-digital converter. (DG/RF) [de

Smart time-pulse coding photoconverters as basic components 2D-array logic devices for advanced neural networks and optical computers

Science.gov (United States)

Krasilenko, Vladimir G.; Nikolsky, Alexander I.; Lazarev, Alexander A.; Michalnichenko, Nikolay N.

2004-04-01

The article deals with a conception of building arithmetic-logic devices (ALD) with a 2D-structure and optical 2D-array inputs-outputs as advanced high-productivity parallel basic operational training modules for realization of basic operation of continuous, neuro-fuzzy, multilevel, threshold and others logics and vector-matrix, vector-tensor procedures in neural networks, that consists in use of time-pulse coding (TPC) architecture and 2D-array smart optoelectronic pulse-width (or pulse-phase) modulators (PWM or PPM) for transformation of input pictures. The input grayscale image is transformed into a group of corresponding short optical pulses or time positions of optical two-level signal swing. We consider optoelectronic implementations of universal (quasi-universal) picture element of two-valued ALD, multi-valued ALD, analog-to-digital converters, multilevel threshold discriminators and we show that 2D-array time-pulse photoconverters are the base elements for these devices. We show simulation results of the time-pulse photoconverters as base components. Considered devices have technical parameters: input optical signals power is 200nW_200μW (if photodiode responsivity is 0.5A/W), conversion time is from tens of microseconds to a millisecond, supply voltage is 1.5_15V, consumption power is from tens of microwatts to a milliwatt, conversion nonlinearity is less than 1%. One cell consists of 2-3 photodiodes and about ten CMOS transistors. This simplicity of the cells allows to carry out their integration in arrays of 32x32, 64x64 elements and more.

Time-Frequency (Wigner Analysis of Linear and Nonlinear Pulse Propagation in Optical Fibers

Directory of Open Access Journals (Sweden)

José Azaña

2005-06-01

Full Text Available Time-frequency analysis, and, in particular, Wigner analysis, is applied to the study of picosecond pulse propagation through optical fibers in both the linear and nonlinear regimes. The effects of first- and second-order group velocity dispersion (GVD and self-phase modulation (SPM are first analyzed separately. The phenomena resulting from the interplay between GVD and SPM in fibers (e.g., soliton formation or optical wave breaking are also investigated in detail. Wigner analysis is demonstrated to be an extremely powerful tool for investigating pulse propagation dynamics in nonlinear dispersive systems (e.g., optical fibers, providing a clearer and deeper insight into the physical phenomena that determine the behavior of these systems.

The conversion of a pulse height analyzer to a time analyzer

International Nuclear Information System (INIS)

Adib, M.; Salama, M.; Abdel-Kawy, A.; Faragalla, S.; Sayed, E.M.; Hamouda, I.

1975-01-01

A transistorized time unit circuit has been designed to convert a 400-channel amplitude analyser (RIDL model 34-12B) to a 400 channel time analyser. The obtained time analyser has channel widths of 24.4 μs, 48.8 μs, 97.6 μs. Experimental determination of the stability of the obtained time analyser was carried out by measuring statistically distributed pulses at constant rate. The stability of the time analyser for long time operation was found to be not less than 0.14%. The linearity of the time scale calibration was checked by measuring the transmission of neutrons through a polycrystalline powder of nickel. This method was found to give a more precise calibration of the time scale than the method based on using the transmission of the elements with well known resonances. From the experimental values obtained for Bragg's cut-off positions for nickel, the non linearity was calculated and found not to exceed 0.3%

Digital pulse-timing technique for the neutron detector array NEDA

Energy Technology Data Exchange (ETDEWEB)

Modamio, V., E-mail: victor.modamio@lnl.infn.it [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, I-35020 Legnaro (Italy); Valiente-Dobón, J.J. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, I-35020 Legnaro (Italy); Jaworski, G. [Faculty of Physics, Warsaw University of Technology, 00-662 Warszawa (Poland); Heavy Ion Laboratory, University of Warsaw, 02-093 Warszawa (Poland); Hüyük, T. [Instituto de Física Corpuscular, CSIC-Universitat de València, E-46980 Valencia (Spain); Triossi, A. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, I-35020 Legnaro (Italy); Egea, J. [Instituto de Física Corpuscular, CSIC-Universitat de València, E-46980 Valencia (Spain); Department of Electronic Engineering, Universitat de València, E-46100 Burjassot (Spain); Di Nitto, A. [Johannes Gutenberg-Universität Mainz, D-55099 Mainz (Germany); Söderström, P.-A. [RIKEN Nishina Center, 2-1 Hirosawa, Wako-shi, 351-0198 Saitama (Japan); Agramunt Ros, J. [Instituto de Física Corpuscular, CSIC-Universitat de València, E-46980 Valencia (Spain); Angelis, G. de [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, I-35020 Legnaro (Italy); France, G. de [GANIL, CEA/DSAM and CNRS/IN2P3, F-14076 Caen (France); Erduran, M.N. [Faculty of Engineering and Natural Sciences, Istanbul Sabahattin Zaim University, 34303 Istanbul (Turkey); and others

2015-03-01

A new digital pulse-timing algorithm, to be used with the future neutron detector array NEDA, has been developed and tested. The time resolution of four 5 in. diameter photomultiplier tubes (XP4512, R4144, R11833-100, and ET9390-kb), coupled to a cylindrical 5 in. by 5 in. BC501A liquid scintillator detector was measured by employing digital sampling electronics and a constant fraction discriminator (CFD) algorithm. The zero crossing of the CFD algorithm was obtained with a cubic spline interpolation, which was continuous up to the second derivative. The performance of the algorithm was studied at sampling rates of 500 MS/s and 200 MS/s. The time resolution obtained with the digital electronics was compared to the values acquired with a standard analog CFD. The result of this comparison shows that the time resolution from the analog and the digital measurements at 500 MS/s and at 200 MS/s are within 15% for all the tested photomultiplier tubes.

Measurements of Electron Transport in Foils Irradiated with a Picosecond Time Scale Laser Pulse

International Nuclear Information System (INIS)

Brown, C. R. D.; Hoarty, D. J.; James, S. F.; Swatton, D.; Hughes, S. J.; Morton, J. W.; Guymer, T. M.; Hill, M. P.; Chapman, D. A.; Andrew, J. E.; Comley, A. J.; Shepherd, R.; Dunn, J.; Chen, H.; Schneider, M.; Brown, G.; Beiersdorfer, P.; Emig, J.

2011-01-01

The heating of solid foils by a picosecond time scale laser pulse has been studied by using x-ray emission spectroscopy. The target material was plastic foil with a buried layer of a spectroscopic tracer material. The laser pulse length was either 0.5 or 2 ps, which resulted in a laser irradiance that varied over the range 10 16 -10 19 W/cm 2 . Time-resolved measurements of the buried layer emission spectra using an ultrafast x-ray streak camera were used to infer the density and temperature conditions as a function of laser parameters and depth of the buried layer. Comparison of the data to different models of electron transport showed that they are consistent with a model of electron transport that predicts the bulk of the target heating is due to return currents.

Determination of pseudo multi-pulse production rate in GM counters by correlation analysis between signal pulses

International Nuclear Information System (INIS)

Hashimoto, Kengo; Ueda, Taizou

1996-01-01

A technique, based on the correlation analysis of signal pulses in time sequence, is proposed to determine the production rate of the pseudo multi-pulse in Geiger-Mueller (GM) counter. With a multi-channel scaler initiated by a signal pulse, subsequent pulses are recorded in sequence. The production of the multi-pulse increases the counting probability immediately after the initiation. By examining the deviation of the measured probability from the ideal counting probability, the production rate and the average lag time to produce the multi-pulse can be determined. By the use of the present technique, the production rate and the average lag time were obtained for the various GM tubes. These results indicate that the consumption of the quench gas results in a significant increase in the production rate but little variation in the lag time, and that the lag time strongly depends on the tube diameter. (author)

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

International Nuclear Information System (INIS)

Ighigeanu, D.; Martin, D.; Oproiu, C.; Cirstea, E.; Craciun, G.

2002-01-01

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

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

Science.gov (United States)

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

2014-01-01

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

Powerful nanosecond pulse train generator

International Nuclear Information System (INIS)

Isakov, I.F.; Logachev, E.I.; Opekunov, M.S.; Pechenkin, S.A.; Remnev, G.E.; Usov, Yu.P.

1987-01-01

A generator permitting to shape on the load pulsed with the repetition frequency of 10 3 -10 6 Hz and more is described. The amplitude of shaped voltage pulses is up to 150 kV at pulse duration equal to 50 ns. The generator comprises connected in-series with the load two shaping and two transmission lines realized on the base of the KVI-300 low-ohmic cable. The shaping lines are supplied from two independently connected pulse voltage generators for obtaining time interval between pulses > 10 -6 s; they may be also supplied from one generator for obtaining time interval -6 s. At the expense of reducing losses in the discharge circuit the amplitude of the second pulse grows with increase of time interval between pulses up to 300 ns, further on the curve flat-topping exists. The described generator is used in high-current accelerators, in which the primary negative pulse results in generation of explosive-emission plasma, and the second positive pulse provides ion beam shaping including ions of heavy metal used for production of a potential electrode. The generator multipulse mode is used for successive ion acceleration in the transport system

Tests on a digital neutron-gamma pulse shape discriminator with NE213

International Nuclear Information System (INIS)

Bell, Z.W.

1981-01-01

A technique using charge sensitive analog-to-digital converters to do neutron-gamma pulse shape discrimination is reported. The converters are gated by short (135 ns) pulses so as to reduce pile-up and the timing is such that the slow and total light output from the scintillator are measured. Preliminary tests indicate that the system performs reasonably well but poorer than some reported analog systems employing gated integrators or cross-over techniques. (orig.)

An injection seeded single frequency Nd:YAG Q-switched laser with precisely controllable laser pulse firing time

Science.gov (United States)

Wu, Frank F.; Khizhnyak, Anatoliy; Markov, Vladimir

2010-02-01

We have realized a single frequency Q-switched Nd:YAG laser with precisely controllable lasing time and thus enabled synchronization of multi-laser systems. The use of injection seeding to the slave ring oscillator results in unidirectional Q-switched laser oscillation with suppression of bidirectional Q-switched oscillation that otherwise would be initiated from spontaneous emission if the seeding laser is not present. Under normal condition, the cavity is high in loss during the pumping period; then a Pockels cell opens the cavity to form the pulse build up, with a second Pockels cell to perform cavity dumping, generating the Q-switched pulse output with optimized characteristics. The two Pockels cells can be replaced by a single unit if an adjustable gated electrical pulse is applied to the Pockels cell in which the pulse front is used to open the cavity and the falling edge to dump the laser pulse. Proper selection of the pump parameters and Pockels-cell gating enables operation of the system in a mode in which the Q-switched pulse can be formed only under the seeding condition. The advantage of the realized regime is in stable laser operation with no need in adjustment of the seeded light wavelength and the mode of the cavity. It is found that the frequency of the Q-switched laser radiation matches well to the injected seeded laser mode. By using two-stage amplifiers, an output energy better than 300 mJ has been achieved in MOPA configuration without active control of the cavity length and with pulse width adjustability from several nanoseconds to 20 ns. The Q-switched oscillator operates not only at precisely controlled firing time but also can be tuned over wide range. This will enable multi-laser systems synchronization and frequency locking down each other if necessary.

Optimal pulse fishing policy in stage-structured models with birth pulses

International Nuclear Information System (INIS)

Gao Shujing; Chen Lansun; Sun Lihua

2005-01-01

In this paper, we propose exploited models with stage structure for the dynamics in a fish population for which periodic birth pulse and pulse fishing occur at different fixed time. Using the stroboscopic map, we obtain an exact cycle of system, and obtain the threshold conditions for its stability. Bifurcation diagrams are constructed with the birth rate (or pulse fishing time or harvesting effort) as the bifurcation parameter, and these are observed to display complex dynamic behaviors, including chaotic bands with period windows, period-doubling, multi-period-halving and incomplete period-doubling bifurcation, pitch-fork and tangent bifurcation, non-unique dynamics (meaning that several attractors or attractor and chaos coexist) and attractor crisis. This suggests that birth pulse and pulse fishing provide a natural period or cyclicity that make the dynamical behaviors more complex. Moreover, we show that the pulse fishing has a strong impact on the persistence of the fish population, on the volume of mature fish stock and on the maximum annual-sustainable yield. An interesting result is obtained that, after the birth pulse, the population can sustain much higher harvesting effort if the mature fish is removed as early as possible

Time resolved 2-D optical imaging of a pulsed unbalanced magnetron plasma

International Nuclear Information System (INIS)

Bradley, J W; Clarke, G C B; Braithwaite, N St J; Bryant, P M; Kelly, P J

2006-01-01

Using wavelength filtered two dimensional (2-D) optical imaging, the temporal and spatial evolution of selected excited species in a pulsed magnetron discharge has been studied. A titanium target was sputtered at a pulse frequency of 100 kHz, in an argon atmosphere, at an operating pressure of 0.27 Pa. The radial information of the emissivity was determined using the Abel inversion technique. The results show strong excitation of the observed species above the racetrack in the on-time, and the possible development of an ion-acoustic wave, initiated after the off-on transition. The on-off transition is accompanied by a burst of light from the plasma bulk consistent with the transient plasma potential reaching about +200 V. During this phase, we argue that there is a release of secondary electrons from the grounded substrate and walls due to ion bombardment, as well as an increased confinement of energetic plasma electrons. The characteristic decay times of the selected transitions at 750.4, 751.5, 810.4 and 811.5 nm (ArI), present within the bandpass width of our filters, is briefly discussed in terms of the production of fast electrons in the system

Subcycle interference dynamics of time-resolved photoelectron holography with midinfrared laser pulses

International Nuclear Information System (INIS)

Bian Xuebin; Yuan, Kai-Jun; Bandrauk, Andre D.; Huismans, Y.; Smirnova, O.; Vrakking, M. J. J.

2011-01-01

Time-resolved photoelectron holography from atoms using midinfrared laser pulses is investigated by solving the corresponding time-dependent Schroedinger equation (TDSE) and a classical model, respectively. The numerical simulation of the photoelectron angular distribution of Xe irradiated with a low-frequency free-electron laser source agrees well with the experimental results. Different types of subcycle interferometric structures are predicted by the classical model. Furthermore with the TDSE model it is demonstrated that the holographic pattern is sensitive to the shape of the atomic orbitals. This is a step toward imaging by means of photoelectron holography.

Picoseconds pulse generation and pulse width determination processes of a distributed feedback dye laser

International Nuclear Information System (INIS)

Abdul Ghani, B.; Hammadi, M.

2004-08-01

A mathematical model has been developed to describe the dynamic emission of Nd-glass, distributed feedback dye laser (DFDL), and periodical grating temperature. The suggested model allows the investigation of the time behavior of Nd-glass laser and DFDL pulsed. Moreover, it allows studying the effect of the laser input parameters of Nd-glass laser on the spectral characteristics of the output DFDL pulses such as pulse width, delay time, and time separation

Determination of residual oil saturation from time-lapse pulsed neutron capture logs in a large sandstone reservoir

International Nuclear Information System (INIS)

Syed, E.V.; Salaita, G.N.; McCaffery, F.G.

1991-01-01

Cased hole logging with pulsed neutron tools finds extensive use for identifying zones of water breakthrough and monitoring oil-water contacts in oil reservoirs being depleted by waterflooding or natural water drive. Results of such surveys then find direct use for planning recompletions and water shutoff treatments. Pulsed neutron capture (PNC) logs are useful for estimating water saturation changes behind casing in the presence of a constant, high-salinity environment. PNC log surveys run at different times, i.e., in a time-lapse mode, are particularly amenable to quantitative analysis. The combined use of the original open hole and PNC time-lapse log information can then provide information on remaining or residual oil saturations in a reservoir. This paper reports analyses of historical pulsed neutron capture log data to assess residual oil saturation in naturally water-swept zones for selected wells from a large sandstone reservoir in the Middle East. Quantitative determination of oil saturations was aided by PNC log information obtained from a series of tests conducted in a new well in the same field

GINGER simulations of short-pulse effects in the LEUTL FEL

International Nuclear Information System (INIS)

Huang, Z.; Fawley, W.M.

2001-01-01

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

System for increasing laser pulse rate

International Nuclear Information System (INIS)

1980-01-01

A technique of static elements is disclosed for combining a plurality of laser beams having time sequenced, pulsed radiation to achieve an augmented pulse rate. The technique may also be applied in a system for combining both time sequenced pulses and frequency distinct pulses for use in a system for isotope enrichment. (author)

The Space-, Time-, and Energy-distribution of Neutrons from a Pulsed Plane Source

Energy Technology Data Exchange (ETDEWEB)

Claesson, Arne

1962-05-15

The space-, time- and energy-distribution of neutrons from a pulsed, plane, high energy source in an infinite medium is determined in a diffusion approximation. For simplicity the moderator is first assumed to be hydrogen gas but it is also shown that the method can be used for a moderator of arbitrary mass.

A high pulsed power supply system designed for pulsed high magnetic field

International Nuclear Information System (INIS)

Liu Kefu; Wang Shaorong; Zhong Heqing; Xu Yan; Pan Yuan

2008-01-01

This paper introduces the design of high pulsed power supply system for producing pulsed high magnetic field up to 70 T. This system consists of 58 sets of 55 μF of capacitor bank which provides 1.0 MJ energy storage. A set of vacuum closing switch is chosen as main switch for energy discharge into magnetic coil. A crowbar circuit with high power diodes in series with resistor is used to absorb the redundant energy and adjust pulse width. The resistance of magnetic coil changing with current is deduced by energy balance equations. A capacitor-charging power supply using a series-resonant, constant on-time variable frequency control, and zero-current switching charges the capacitor bank in one minute time with high efficiency. The pulsed power supply provides adjustable current and pulse width with 30 kA peak and 30 ms maximum. The primary experiments demonstrate the system reliability. This work provides an engineering guidance for future development of pulsed high magnetic field. (authors)

A study of the real-time deconvolution of digitized waveforms with pulse pile up for digital radiation spectroscopy

International Nuclear Information System (INIS)

Guo Weijun; Gardner, Robin P.; Mayo, Charles W.

2005-01-01

Two new real-time approaches have been developed and compared to the least-squares fit approach for the deconvolution of experimental waveforms with pile-up pulses. The single pulse shape chosen is typical for scintillators such as LSO and NaI(Tl). Simulated waveforms with pulse pile up were also generated and deconvolved to compare these three different approaches under cases where the single pulse component has a constant shape and the digitization error dominates. The effects of temporal separation and amplitude ratio between pile-up component pulses were also investigated and statistical tests were applied to quantify the consistency of deconvolution results for each case. Monte Carlo simulation demonstrated that applications of these pile-up deconvolution techniques to radiation spectroscopy are effective in extending the counting-rate range while preserving energy resolution for scintillation detectors

Parallel processing method for high-speed real time digital pulse processing for gamma-ray spectroscopy

International Nuclear Information System (INIS)

Fernandes, A.M.; Pereira, R.C.; Sousa, J.; Neto, A.; Carvalho, P.; Batista, A.J.N.; Carvalho, B.B.; Varandas, C.A.F.; Tardocchi, M.; Gorini, G.

2010-01-01

A new data acquisition (DAQ) system was developed to fulfil the requirements of the gamma-ray spectrometer (GRS) JET-EP2 (joint European Torus enhancement project 2), providing high-resolution spectroscopy at very high-count rate (up to few MHz). The system is based on the Advanced Telecommunications Computing Architecture TM (ATCA TM ) and includes a transient record (TR) module with 8 channels of 14 bits resolution at 400 MSamples/s (MSPS) sampling rate, 4 GB of local memory, and 2 field programmable gate array (FPGA) able to perform real time algorithms for data reduction and digital pulse processing. Although at 400 MSPS only fast programmable devices such as FPGAs can be used either for data processing and data transfer, FPGA resources also present speed limitation at some specific tasks, leading to an unavoidable data lost when demanding algorithms are applied. To overcome this problem and foreseeing an increase of the algorithm complexity, a new digital parallel filter was developed, aiming to perform real time pulse processing in the FPGAs of the TR module at the presented sampling rate. The filter is based on the conventional digital time-invariant trapezoidal shaper operating with parallelized data while performing pulse height analysis (PHA) and pile up rejection (PUR). The incoming sampled data is successively parallelized and fed into the processing algorithm block at one fourth of the sampling rate. The following data processing and data transfer is also performed at one fourth of the sampling rate. The algorithm based on data parallelization technique was implemented and tested at JET facilities, where a spectrum was obtained. Attending to the observed results, the PHA algorithm will be improved by implementing the pulse pile up discrimination.

Proposal for a fast, zero suppressing circuit for the digitization of analog pulses over long memory times

International Nuclear Information System (INIS)

Bourgeois, F.

1984-01-01

This report describes the design principles of a fast (100 MHz) time and pulse height digitizer that can record up to 15 analog pulses over 10-80 μs memory times. Unlike other triggered circuits prepulse samples are recorded without the help of an analog delay line. The low power requirements of the circuit as well as its fast read-out characteristics make it very attractive for detectors with many digitizing channels. Conventional circuits are described as a reference for the evaluation of this new design. An ECL 10 K implementation of the circuit is presented in the third section. (orig.)

DynPeak: An Algorithm for Pulse Detection and Frequency Analysis in Hormonal Time Series

Science.gov (United States)

Vidal, Alexandre; Zhang, Qinghua; Médigue, Claire; Fabre, Stéphane; Clément, Frédérique

2012-01-01

The endocrine control of the reproductive function is often studied from the analysis of luteinizing hormone (LH) pulsatile secretion by the pituitary gland. Whereas measurements in the cavernous sinus cumulate anatomical and technical difficulties, LH levels can be easily assessed from jugular blood. However, plasma levels result from a convolution process due to clearance effects when LH enters the general circulation. Simultaneous measurements comparing LH levels in the cavernous sinus and jugular blood have revealed clear differences in the pulse shape, the amplitude and the baseline. Besides, experimental sampling occurs at a relatively low frequency (typically every 10 min) with respect to LH highest frequency release (one pulse per hour) and the resulting LH measurements are noised by both experimental and assay errors. As a result, the pattern of plasma LH may be not so clearly pulsatile. Yet, reliable information on the InterPulse Intervals (IPI) is a prerequisite to study precisely the steroid feedback exerted on the pituitary level. Hence, there is a real need for robust IPI detection algorithms. In this article, we present an algorithm for the monitoring of LH pulse frequency, basing ourselves both on the available endocrinological knowledge on LH pulse (shape and duration with respect to the frequency regime) and synthetic LH data generated by a simple model. We make use of synthetic data to make clear some basic notions underlying our algorithmic choices. We focus on explaining how the process of sampling affects drastically the original pattern of secretion, and especially the amplitude of the detectable pulses. We then describe the algorithm in details and perform it on different sets of both synthetic and experimental LH time series. We further comment on how to diagnose possible outliers from the series of IPIs which is the main output of the algorithm. PMID:22802933

The use of diffusion theory to compute invasion effects for the pulsed neutron thermal decay time log

International Nuclear Information System (INIS)

Tittle, C.W.

1992-01-01

Diffusion theory has been successfully used to model the effect of fluid invasion into the formation for neutron porosity logs and for the gamma-gamma density log. The purpose of this paper is to present results of computations using a five-group time-dependent diffusion code on invasion effects for the pulsed neutron thermal decay time log. Previous invasion studies by the author involved the use of a three-dimensional three-group steady-state diffusion theory to model the dual-detector thermal neutron porosity log and the gamma-gamma density log. The five-group time-dependent code MGNDE (Multi-Group Neutron Diffusion Equation) used in this work was written by Ferguson. It has been successfully used to compute the intrinsic formation life-time correction for pulsed neutron thermal decay time logs. This application involves the effect of fluid invasion into the formation

Measurements of the plasma density in the FTU tokamak by a pulsed time-of-flight X-wave refractometer

International Nuclear Information System (INIS)

Petrov, V. G.; Petrov, A. A.; Malyshev, A. Yu.; De Benedetti, M.; Tudisco, O.

2008-01-01

On-line control over the plasma density in tokamaks (especially, in long-term discharges) requires reliable measurements of the averaged plasma density. For this purpose, a new method of density measurements-a pulsed time-of-flight plasma refractometry-was developed and tested in the T-11M tokamak. This method allows one to determine the averaged density from the measured time delay of nanosecond microwave pulses propagating through the plasma. For an O-wave, the measured time delay is proportional to the line-averaged density and is independent of the density profile (f>>f p ) τ o ∼ k o 1/f 2 ∫ l N(x)dx. Here, f is the frequency of the probing wave, f p is the plasma frequency, l= 4 a is the path length for two-pass probing in the equatorial plane, a is the plasma minor radius, k O and k X are numerical factors, f c is the electron-cyclotron frequency at the axis of the plasma column, and f p >>f c , f. Measurements of the time delay provide the same information as plasma interferometry, though they do no employ the effect of interference. When the conditions f p >>f c , f are not satisfied, the measured time delay depends on the shape of the density profile. In this case, in order to determine the average density regardless of the density profile, it is necessary to perform simultaneous measurements at several probing frequencies in order to determine the average density. In ITER (Bt ∼ 5T), a spectral window between the lower and upper cutoff frequencies in the range of 50-100 GHz can be used for pulsed time-of-flight X-wave refractometry. This appreciably simplifies the diagnostics and eliminates the problem of the first mirror. In this paper, the first results obtained in the FTU tokamak with a prototype of the ITER pulsed time-of-flight refractometer are presented. The geometry and layout of experiments similar to the planned ITER experiments are described. The density measured by pulsed time-of-flight refractometry is shown to agree well with the

Maximum Likelihood Time-of-Arrival Estimation of Optical Pulses via Photon-Counting Photodetectors

Science.gov (United States)

Erkmen, Baris I.; Moision, Bruce E.

2010-01-01

Many optical imaging, ranging, and communications systems rely on the estimation of the arrival time of an optical pulse. Recently, such systems have been increasingly employing photon-counting photodetector technology, which changes the statistics of the observed photocurrent. This requires time-of-arrival estimators to be developed and their performances characterized. The statistics of the output of an ideal photodetector, which are well modeled as a Poisson point process, were considered. An analytical model was developed for the mean-square error of the maximum likelihood (ML) estimator, demonstrating two phenomena that cause deviations from the minimum achievable error at low signal power. An approximation was derived to the threshold at which the ML estimator essentially fails to provide better than a random guess of the pulse arrival time. Comparing the analytic model performance predictions to those obtained via simulations, it was verified that the model accurately predicts the ML performance over all regimes considered. There is little prior art that attempts to understand the fundamental limitations to time-of-arrival estimation from Poisson statistics. This work establishes both a simple mathematical description of the error behavior, and the associated physical processes that yield this behavior. Previous work on mean-square error characterization for ML estimators has predominantly focused on additive Gaussian noise. This work demonstrates that the discrete nature of the Poisson noise process leads to a distinctly different error behavior.

CAMAC-compatible differential pulse discriminator-counter

International Nuclear Information System (INIS)

Tselikov, I.V.

1988-01-01

A differential pulse discriminator-counter for a Moessbauer spectrometer is described. Input pulses are collected according to the following algorithm; a pulse is admitted into the channel depending on whether or not the preceding pulse fell into the discrimination window. The circuit does not contain delay lines to allow for the delay lines to allow for the delay of the signal from the upper-level discriminator with respect to the signal from the lower-level discriminator due to the finite rise time of the input pulses, which makes it possible to reduce the dead time of the discriminator to the actuation time of the threshold circuits. The pulse count rate is 150 MHz, the input amplitude is +/-3 V, the dead time is 6 nsec, and the delay from input to output is 14 nsec. The unit is CAMAC-compatible

Pulsed laser dewetting of nickel catalyst for carbon nanofiber growth

International Nuclear Information System (INIS)

Guan, Y F; Pearce, R C; Simpson, M L; Rack, P D; Melechko, A V; Hensley, D K

2008-01-01

We present a pulsed laser dewetting technique that produces single nickel catalyst particles from lithographically patterned disks for subsequent carbon nanofiber growth through plasma enhanced chemical vapor deposition. Unlike the case for standard heat treated Ni catalyst disks, for which multiple nickel particles and consequently multiple carbon nanofibers (CNFs) are observed, single vertically aligned CNFs could be obtained from the laser dewetted catalyst. Different laser dewetting parameters were tested in this study, such as the laser energy density and the laser processing time measured by the total number of laser pulses. Various nickel disk radii and thicknesses were attempted and the resultant number of carbon nanofibers was found to be a function of the initial disk dimension and the number of laser pulses

Analog measurement of delayed antiproton annihilation time spectra in a high intensity pulsed antiproton beam

International Nuclear Information System (INIS)

Niestroj, A.; Hayano, R.S.; Ishikawa, T.; Tamura, H.; Torii, H.A.; Morita, N.; Yamazaki, T.; Sugai, I.; Nakayoshi, K.; Horvath, D.; Eades, J.; Widmann, E.

1996-01-01

An analog detection system has been developed to measure delayed antiproton annihilation time spectra for laser resonance spectroscopy of metastable antiprotonic helium atoms using the high-intensity pulsed beam of antiprotons from LEAR at CERN. (orig.)

Pulsed feedback defers cellular differentiation.

Directory of Open Access Journals (Sweden)

Joe H Levine

2012-01-01

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

Detection of time of arrival of ultrasonic pulses

International Nuclear Information System (INIS)

Latino, Carl D; Andersen, Niels Lervad; Voss, Frands

2006-01-01

Applications exist that employ transit-time measurements to determine distances to scattering objects. These include blood-flow measurements, fluid-level detection, nondestructive testing of materials, image processing of geometrical bodies etc. Many of these require extreme accuracy in measuring transit time through a medium. The system typically consists of a transmitter, a medium and a receiver. The signal sent must operate within the limitations imposed by this overall system. Under ideal conditions a finite duration pulse consisting of a sinusoidal signal is sent and received. If the transmitted signal contains an integer number of complete cycles of a single frequency, performing a correlation between transmitted and received signals can accurately recover the transit time information. The method has difficulties especially in the presence of noise. The problem is compounded if the desired accuracy is a small fraction of a single sinusoid period. Noise could cause the correlation results to be off by a complete cycle. For a one MHz signal, one cycle error corresponds to a one microsecond error. For applications requiring nanosecond accuracy, this is not acceptable. Varying the frequency content of the signal reduces the error but requires that the transmitter, receiver and medium all have a broader band spectrum. The improvements we propose here work within a narrow band while enhancing the chance of recovering the signal accurately

Scattering of electromagnetic pulses by metal nanospheres in the vicinity of a Fano-like resonance

International Nuclear Information System (INIS)

Astapenko, V.A.; Svita, S.Yu.

2015-01-01

In the work, radiation scattering by metal nanospheres in a dielectric matrix in case of ultrashort and long electromagnetic pulses is studied theoretically. Spectral efficiencies of backward and forward scattering by silver nanospheres in glass are calculated with the use of experimental data on the dielectric permittivity of silver. The presence of Fano-like resonances in spectral dependences of scattering efficiency caused by interference of dipole and quadrupole scatterings is shown. Backward and forward scattering of ultrashort pulses is calculated and analyzed. The obtained dependences of the total probability of scattering (during all time of the action of a pulse) on pulse duration demonstrate an essential distinction between an ultrashort case and a long pulse limit

Supercoherent phenomena in pulsed power

International Nuclear Information System (INIS)

O'Rourke, R.C.

1983-01-01

This chapter proposes the formulation of programs of basic physics research to transform Pulsed Power Technology (PPT) to Pulsed Power Science and Technology (PPS and T) by formulating the laws of the quantized microscopic electromagnetic field; applying the microscopic electromagnetic field theory to the generation, propagation and deposition of pulses in nonlinear networks; learning more about the basic super coherent ''micro-structure'' in space and time of the many-photon states of pulsed laser beams; learning more about the basic super coherent ''micro-structure'' in space and time of the many-electronstates of pulsed electron and ion laser beams; and learning everything about the ''micro-picture'' of so-called ''dielectric breakdown'' and the associated absolute time delays. Promotes the idea that laser, electron and ion beams are similar kinds of pulses in the microscopic electromagnetic field. Presents expression for the microscopic electromagnetic field in order to show the role of supercoherence in PPS and T

GAMMASPHERE: Elimination of ballistic deficit by using a quasi-trapezoidal pulse shaper

International Nuclear Information System (INIS)

Goulding, F.S.; Landis, D.A.; Madden, N.; Maier, M.; Yaver, H.

1993-10-01

Gammasphere uses an spherical array of very large (7.2cm dia.) germanium detectors and only high-multiplicity events are studied. To achieve a reasonable coincidence rate, the individual detector channels must handle high rates with minimum pile-up losses. Ten microseconds was chosen as the total processing time for a signal which means that the shaped signal peaks in about 4us. The combination of short pulse shaping and the fluctuating long charge collection times (up to 400ns) in the detectors exaggerates the energy resolution degradation due to ballistic deficit effects. We describe a method of producing a flat-topped pulse with a simple time-invariant network that satisfies GAMMASPHERE requirements and eliminates ballistic deficit effects

Investigation on stresses of superconductors under pulsed magnetic fields based on multiphysics model

International Nuclear Information System (INIS)

Yang, Xiaobin; Li, Xiuhong; He, Yafeng; Wang, Xiaojun; Xu, Bo

2017-01-01

Highlights: • The differential equation including temperature and magnetic field was derived for a long cylindrical superconductor. • Thermal stress and electromagnetic stress were studied at the same time under pulse field magnetizing. • The distributions of the magnetic field, the temperature and stresses are studied and compared for two pulse fields of the different duration. • The Role thermal stress and electromagnetic stress play in the process of pulse field magnetizing is discussed. - Abstract: A multiphysics model for the numerical computation of stresses, trapped field and temperature distribution of a infinite long superconducting cylinder is proposed, based on which the stresses, including the thermal stresses and mechanical stresses due to Lorentz force, and trapped fields in the superconductor subjected to pulsed magnetic fields are analyzed. By comparing the results under pulsed magnetic fields with different pulse durations, it is found that the both the mechanical stress due to the electromagnetic force and the thermal stress due to temperature gradient contribute to the total stress level in the superconductor. For pulsed magnetic field with short durations, the thermal stress is the dominant contribution to the total stress, because the heat generated by AC-loss builds up significant temperature gradient in such short durations. However, for a pulsed field with a long duration the gradient of temperature and flux, as well as the maximal tensile stress, are much smaller. And the results of this paper is meaningful for the design and manufacture of superconducting permanent magnets.

Investigation on stresses of superconductors under pulsed magnetic fields based on multiphysics model

Energy Technology Data Exchange (ETDEWEB)

Yang, Xiaobin, E-mail: yangxb@lzu.edu.cn; Li, Xiuhong; He, Yafeng; Wang, Xiaojun; Xu, Bo

2017-04-15

Highlights: • The differential equation including temperature and magnetic field was derived for a long cylindrical superconductor. • Thermal stress and electromagnetic stress were studied at the same time under pulse field magnetizing. • The distributions of the magnetic field, the temperature and stresses are studied and compared for two pulse fields of the different duration. • The Role thermal stress and electromagnetic stress play in the process of pulse field magnetizing is discussed. - Abstract: A multiphysics model for the numerical computation of stresses, trapped field and temperature distribution of a infinite long superconducting cylinder is proposed, based on which the stresses, including the thermal stresses and mechanical stresses due to Lorentz force, and trapped fields in the superconductor subjected to pulsed magnetic fields are analyzed. By comparing the results under pulsed magnetic fields with different pulse durations, it is found that the both the mechanical stress due to the electromagnetic force and the thermal stress due to temperature gradient contribute to the total stress level in the superconductor. For pulsed magnetic field with short durations, the thermal stress is the dominant contribution to the total stress, because the heat generated by AC-loss builds up significant temperature gradient in such short durations. However, for a pulsed field with a long duration the gradient of temperature and flux, as well as the maximal tensile stress, are much smaller. And the results of this paper is meaningful for the design and manufacture of superconducting permanent magnets.

Determination and identification of naturally occurring decay series using milli-second order pulse time interval analysis (TIA)

International Nuclear Information System (INIS)

Hashimoto, T.; Sanada, Y.; Uezu, Y.

2003-01-01

A delayed coincidence method, called a time interval analysis (TIA) method, has been successfully applied to selective determination of the correlated α-α decay events in millisecond order life-time. A main decay process applicable to TIA-treatment is 220 Rn → 216 Po(T 1/2 :145ms) → {Th-series}. The TIA is fundamentally based on the difference of time interval distribution between non-correlated decay events and other events such as background or random events when they were compiled the time interval data within a fixed time (for example, a tenth of concerned half lives). The sensitivity of the TIA-analysis due to correlated α-α decay events could be subsequently improved in respect of background elimination using the pulse shape discrimination technique (PSD with PERALS counter) to reject β/γ-pulses, purging of nitrogen gas into extra scintillator, and applying solvent extraction of Ra. (author)

Pulse-to-pulse variations in accreting X-ray pulsars

Directory of Open Access Journals (Sweden)

Kretschmar Peter

2014-01-01

Full Text Available In most accreting X-ray pulsars, the periodic signal is very clear and easily shows up as soon as data covering sufficient pulse periods (a few ten are available. The mean pulse profile is often quite typical for a given source and with minor variations repeated and recognisable across observations done years or even decades apart. At the time scale of individual pulses, significant pulse-to-pulse variations are commonly observed. While at low energies some of these variations might be explained by absorption, in the hard X-rays they will reflect changes in the accretion and subsequent emission. The amount of these variations appears to be quite different between sources and contains information about the surrounding material as well ass possibly interactions at the magnetosphere. We investigate such variations for a sample of well-known sources.

Effect of time walk in the use of single channel analyzer/discriminator for saturated pulses in the 4πβ–γ coincidence experiments

International Nuclear Information System (INIS)

Kawada, Yasushi; Yunoki, Akira; Yamada, Takahiro; Hino, Yoshio

2016-01-01

Using the TAC technique, the timing properties of a 4πβ–γ coincidence counting system were experimentally studied with an emphasis on saturated pulses. Experiments were performed for several discriminators (integral mode of TSCA) each with different kinds of timing techniques. Timing spectra were measured at various applied voltage to the 4π proportional detector covering the entire region of the plateau. Most of timing discriminators show good timing property when the pulses remain the linear region, but suddenly deteriorate after the pulses was saturated, and the timing spectra expands seriously up to a few μs in some types of timing discriminator. To overcome this problem, two techniques were proposed. - Highlights: • Timing properties of several kinds of SCA/Discriminators were studied, including trailing edge CFT. • Focus of study on saturated pulses, using a 4πβ–γ coincidence counting system and TAC. • Validity of two novel techniques to overcome this problem was shown.

A time-dependent B-spline R-matrix approach to double ionization of atoms by XUV laser pulses

Energy Technology Data Exchange (ETDEWEB)

Guan Xiaoxu; Zatsarinny, O; Noble, C J; Bartschat, K [Department of Physics and Astronomy, Drake University, Des Moines, IA 50311 (United States); Schneider, B I [Physics Division, National Science Foundation, Arlington, Virgina 22230 (United States)], E-mail: xiaoxu.guan@drake.edu, E-mail: oleg.zatsarinny@drake.edu, E-mail: cjn@maxnet.co.nz, E-mail: klaus.bartschat@drake.edu, E-mail: bschneid@nsf.gov

2009-07-14

We present an ab initio and non-perturbative time-dependent approach to the problem of double ionization of a general atom driven by intense XUV laser pulses. After using a highly flexible B-spline R-matrix method to generate field-free Hamiltonian and electric dipole matrices, the initial state is propagated in time using an efficient Arnoldi-Lanczos scheme. Test calculations for double ionization of He by a single laser pulse yield good agreement with benchmark results obtained with other methods. The method is then applied to two-colour pump-probe processes, for which momentum and energy distributions of the two outgoing electrons are presented.

analysis of large electromagnetic pulse simulators using the electric field integral equation method in time domain

International Nuclear Information System (INIS)

Jamali, J.; Aghajafari, R.; Moini, R.; Sadeghi, H.

2002-01-01

A time-domain approach is presented to calculate electromagnetic fields inside a large Electromagnetic Pulse (EMP) simulator. This type of EMP simulator is used for studying the effect of electromagnetic pulses on electrical apparatus in various structures such as vehicles, a reoplanes, etc. The simulator consists of three planar transmission lines. To solve the problem, we first model the metallic structure of the simulator as a grid of conducting wires. The numerical solution of the governing electric field integral equation is then obtained using the method of moments in time domain. To demonstrate the accuracy of the model, we consider a typical EMP simulator. The comparison of our results with those obtained experimentally in the literature validates the model introduced in this paper

Simulation of neutrons and gamma pulse signal and research on the pulse shape discrimination technology

International Nuclear Information System (INIS)

Zuo Guangxia; He Bin; Xu Peng; Qiu Xiaolin; Ma Wenyan; Li Sufen

2012-01-01

In neutrons detection, it is important to discriminate the neutron signals from the gamma-ray background. In this article, simulation of neutrons and gamma pulse signals is developed based on the LabVIEW platform. Two digital algorithms of the charge comparison method and the pulse duration time method are realized using 10000 simulation signals. Experimental results show that neutron and gamma pulse signals can be discriminated by the two methods, and the pulse duration time method is better than the charge comparison method. (authors)

Rapid thermal pulse annealing

International Nuclear Information System (INIS)

Miller, M.G.; Koehn, B.W.; Chaplin, R.L.

1976-01-01

Characteristics of recovery processes have been investigated for cases of heating a sample to successively higher temperatures by means of isochronal annealing or by using a rapid pulse annealing. A recovery spectra shows the same features independent of which annealing procedure is used. In order to determine which technique provides the best resolution, a study was made of how two independent first-order processes are separated for different heating rates and time increments of the annealing pulses. It is shown that the pulse anneal method offers definite advantages over isochronal annealing when annealing for short time increments. Experimental data by means of the pulse anneal techniques are given for the various substages of stage I of aluminium. (author)

Continuous pulse oximetry in the general surgical ward: Nellcor N-200 versus Nellcor N-3000

DEFF Research Database (Denmark)

Christensen, M; Lie, C; Rosenberg, J

1999-01-01

of drop-outs (loss of signal) was 13 (range 1-46) with the N-200 compared with nine (2-41) with the N-3000 (p = 0.06). The N-200 registered saturation values of 85% or below for 23% of the observation time compared with 6% of the observation time with the N-3000 pulse oximeter (p ... Symphony N-3000 with the Nellcor N-200 pulse oximeter, when monitoring patients in the general surgical ward. Twenty-two patients were monitored during unrestricted ward activities for a total of 275 h with a N-3000 and a N-200 pulse oximeter simultaneously. Data were analysed for lack of concordance...... between the two pulse oximeters with respect to frequency of registered hypoxaemic episodes and thus the amount of time spent in the alarm state. The median number of desaturation episodes with the N-200 was 18 (range 0-511) compared with four (range 0-476) with the N-3000 (p

Parametric performance predictions for high-power pulsed electric CO lasers

International Nuclear Information System (INIS)

Center, R.E.; Caledonia, G.E.

1975-01-01

A kinetic model of the pulsed electrical CO laser is used to survey the time-dependent laser performance on parameters such as gas mixture, initial translational temperature, and discharge pulse length for both multiline and selected-line operation. Predictions are presented for the total output efficiency, spectral distributions of the stimulated transitions, energy partitioning in the vibrational and translational modes, and the translational temperature history in CO-N 2 mixtures. A brief description of the kinetic model is included. Simple scaling relationships are presented which can be used to scale the results to other densities in the pressure-broadened regime

Effects of pulse-to-pulse residual species on discharges in repetitively pulsed discharges through packed bed reactors

Science.gov (United States)

Kruszelnicki, Juliusz; Engeling, Kenneth W.; Foster, John E.; Kushner, Mark J.

2016-09-01

Atmospheric pressure dielectric barrier discharges (DBDs) sustained in packed bed reactors (PBRs) are being investigated for conversion of toxic and waste gases, and CO2 removal. These discharges are repetitively pulsed having varying flow rates and internal geometries, which results in species from the prior pulse still being in the discharge zone at the time the following discharge pulse occurs. A non-negligible residual plasma density remains, which effectively acts as preionization. This residual charge changes the discharge properties of subsequent pulses, and may impact important PBR properties such as chemical selectivity. Similarly, the residual neutral reactive species produced during earlier pulses will impact the reaction rates on subsequent pulses. We report on results of a computational investigation of a 2D PBR using the plasma hydrodynamics simulator nonPDPSIM. Results will be discussed for air flowing though an array of dielectric rods at atmospheric pressure. The effects of inter-pulse residual species on PBR discharges will be quantified. Means of controlling the presence of residual species in the reactor through gas flow rate, pulse repetition, pulse width and geometry will be described. Comparisons will be made to experiments. Work supported by US DOE Office of Fusion Energy Science and the National Science Foundation.

Arbitrarily accurate twin composite π -pulse sequences

Science.gov (United States)

Torosov, Boyan T.; Vitanov, Nikolay V.

2018-04-01

We present three classes of symmetric broadband composite pulse sequences. The composite phases are given by analytic formulas (rational fractions of π ) valid for any number of constituent pulses. The transition probability is expressed by simple analytic formulas and the order of pulse area error compensation grows linearly with the number of pulses. Therefore, any desired compensation order can be produced by an appropriate composite sequence; in this sense, they are arbitrarily accurate. These composite pulses perform equally well as or better than previously published ones. Moreover, the current sequences are more flexible as they allow total pulse areas of arbitrary integer multiples of π .

Analysis of chromatic dispersion compensation by measuring time domain optical spectrum distribution of light pulse; Hikari pulse chu no hacho jikan bunpu sokutei ni yoru bunsan hosho gijutsu no hyokaho

Energy Technology Data Exchange (ETDEWEB)

Saito, M.; Kurono, M. [Central Research Institute of Electric Power Industry, Tokyo (Japan)

1997-05-01

A large number of single mode fibers (SMF) for 1.3 {mu}m light are installed in electric power communication facilities. On the other hand, light of 1.5 {mu}m band is being used more in the capacity increasing technology to minimize transmission loss. If this is applied to the current SMF, waveform distortion is generated due to wavelength dispersion, thus the transmission speed and distance are limited. In order to evaluate quantitatively the effects of a wavelength dispersion compensating technology, a method was developed to derive time change in each wavelength component in light pulse. No sufficient wavelength separation is possible if permeation bandwidth of a wavelength filter is wider than the wavelength width of the light pulse. Therefore, a method was developed to derive time change in the wavelength components in the light pulse from small difference in the measured light waveforms after transmission when the central wavelength of a wavelength variable filter is varied. It was possible from comparing the method to derive the wavelength dispersion amount and the dispersion compensation amount. Since the method reveals simultaneously the distribution of strength against wavelength and time contained in light pulse, the method is advantageous in elucidating compensation limit and causes for compensation errors. The effectiveness of the method was verified by a 1.5-{mu}m light transmission test. 14 refs., 26 figs., 2 tabs.

Portable double-sided pulsed laser heating system for time-resolved geoscience and materials science applications.

Science.gov (United States)

Aprilis, G; Strohm, C; Kupenko, I; Linhardt, S; Laskin, A; Vasiukov, D M; Cerantola, V; Koemets, E G; McCammon, C; Kurnosov, A; Chumakov, A I; Rüffer, R; Dubrovinskaia, N; Dubrovinsky, L

2017-08-01

A portable double-sided pulsed laser heating system for diamond anvil cells has been developed that is able to stably produce laser pulses as short as a few microseconds with repetition frequencies up to 100 kHz. In situ temperature determination is possible by collecting and fitting the thermal radiation spectrum for a specific wavelength range (particularly, between 650 nm and 850 nm) to the Planck radiation function. Surface temperature information can also be time-resolved by using a gated detector that is synchronized with the laser pulse modulation and space-resolved with the implementation of a multi-point thermal radiation collection technique. The system can be easily coupled with equipment at synchrotron facilities, particularly for nuclear resonance spectroscopy experiments. Examples of applications include investigations of high-pressure high-temperature behavior of iron oxides, both in house and at the European Synchrotron Radiation Facility using the synchrotron Mössbauer source and nuclear inelastic scattering.

Verification of the Time Accuracy of a Magnometer by Using a GPS Pulse Generator

Directory of Open Access Journals (Sweden)

Yasuhiro Minamoto

2011-05-01

Full Text Available The time accuracy of geomagnetic data is an important specification for one-second data distributions. We tested a procedure to verify the time accuracy of a fluxgate magnetometer by using a GPS pulse generator. The magnetometer was equipped with a high time resolution (100 Hz output, so the data delay could be checked directly. The delay detected from one-second data by a statistical method was larger than those from 0.1-s- and 0.01-s-resolution data. The test of the time accuracy revealed the larger delay and was useful for verifying the quality of the data.

Fast neutron flux analyzer with real-time digital pulse shape discrimination

Energy Technology Data Exchange (ETDEWEB)

Ivanova, A.A., E-mail: a.a.ivanova@inp.nsk.su [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk (Russian Federation); Zubarev, P.V. [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State Technical University, 630092 Novosibirsk (Russian Federation); Ivanenko, S.V. [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk (Russian Federation); Khilchenko, A.D. [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State Technical University, 630092 Novosibirsk (Russian Federation); Kotelnikov, A.I. [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk (Russian Federation); Polosatkin, S.V. [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State Technical University, 630092 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Puryga, E.A.; Shvyrev, V.G. [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State Technical University, 630092 Novosibirsk (Russian Federation); Sulyaev, Yu.S. [Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation)

2016-08-11

Investigation of subthermonuclear plasma confinement and heating in magnetic fusion devices such as GOL–3 and GDT at the Budker Institute (Novosibirsk, Russia) requires sophisticated equipment for neutron-, gamma- diagnostics and upgrading data acquisition systems with online data processing. Measurement of fast neutron flux with stilbene scintillation detectors raised the problem of discrimination of the neutrons (n) from background cosmic particles (muons) and neutron-induced gamma rays (γ). This paper describes a fast neutron flux analyzer with real-time digital pulse-shape discrimination (DPSD) algorithm FPGA-implemented for the GOL–3 and GDT devices. This analyzer was tested and calibrated with the help of {sup 137}Cs and {sup 252}Cf radiation sources. The Figures of Merit (FOM) calculated for different energy cuts are presented. - Highlights: • Electronic equipment for measurement of fast neutron flux with stilbene scintillator is presented. • FPGA-implemented digital pulse-shape discrimination algorithm by charge comparison method is shown. • Calibration of analyzer was carried out with {sup 137}Cs and {sup 252}Cf. • Figures of Merit (FOM) values for energy cuts from 1/8 Cs to 2 Cs are from 1.264 to 2.34 respectively.

Pulse radiolysis of liquid water using picosecond electron pulses produced by a table-top terawatt laser system

International Nuclear Information System (INIS)

Saleh, Ned; Flippo, Kirk; Nemoto, Koshichi; Umstadter, Donald; Crowell, Robert A.; Jonah, Charles D.; Trifunac, Alexander D.

2000-01-01

A laser based electron generator is shown, for the first time, to produce sufficient charge to conduct time resolved investigations of radiation induced chemical events. Electron pulses generated by focussing terawatt laser pulses into a supersonic helium gas jet are used to ionize liquid water. The decay of the hydrated electrons produced by the ionizing electron pulses is monitored with 0.3 μs time resolution. Hydrated electron concentrations as high as 22 μM were generated. The results show that terawatt lasers offer both an alternative to linear accelerators and a means to achieve subpicosecond time resolution for pulse radiolysis studies. (c) 2000 American Institute of Physics

Rise time of voltage pulses in NbN superconducting single photon detectors

Energy Technology Data Exchange (ETDEWEB)

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

2016-08-01

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

Photonics at the frontiers. Generation of few-cycle light pulses via NOPCPA and real-time probing of charge transfer in hybrid photovoltaics

Energy Technology Data Exchange (ETDEWEB)

Herrmann, Daniel

2011-11-11

In the first part of this thesis the methodics of the non-collinear, optically parametric amplification of chirped light pulses (NOPCPA) for the generation of few-cycle light pulses in the visible (Vis) and near infrared (NIR) with of 5-8 fs half-width are essential further developed. Fundamental parametric influences, like the existence of a parametrically induced phase and the generation of optically parametric fluorescence (OPF), are studied both by theoretical analyses and numerical simulations and by concrete experiments. Experimentally in the framework of this thesis fwe-cycle light pulses with a pulse width of 7.9 fs, 130 mJ energy, at 805 nm central wavelength and a very high seed-pulse-limited prepulse contrast of 11 and 8 orders of magnitude are reached at 30 ps and approximately 3 ps. One the one hand it has been succeeded to accelerate with the broad-band pulse amplifier quasi-monoenergetic electrons with energies of up to 50 MeV. For this the light pulse is focussed to relativistic intensities of several W/cm{sup 2} in a helium gas jet. On the other hand XUV light was produced up to the 20th harmonic of the generated light pulse from the broad-band pulse amplifier by its sub-cycle interaction with solid surfaces. In the framework of this thesis furthermore new, extended concepts for still broader-band NOPCPA over one octave were developed and characterized, which contain the application of two pump pulses in one NOPCPA stage and the application of two different pump wavelength in two subsequent NOPCPA stages. In the second part of this thesis broad-band white-light spectra and by means of NOPCPA spectrally tunable light pulses are applied in order to realize a transient absorption spectrometer with multichannel detection. This new excitation-query construction combines a very broad-band UV-Vis-NIR query with a high time resolution of 40 fs and high sensitivity for the transient change of the optical density of less than 10{sup -4}. By this it has in

Effect of pulse-wave factors in Middle Aged Women by Mountain Cultivated Ginseng Pharmacopuncture Original Articles

Directory of Open Access Journals (Sweden)

Park Sang Wook

2011-03-01

Full Text Available Objectives: The aim of this experiment is to know about Effect of pulse-wave factors in Middle Aged Women by Mountain Cultivated Ginseng Pharmacopuncture. Methods: First 20 Middle Aged women are diagnosed by pulse diagnosis, and then Mountain Cultivated Ginseng Pharmacopuncture(1 injection 20cc were injected. 30 minutes later, pulse diagnosis again performed. As a result, method of one-group pretest-posttes design were used for evaluation. Results: T(Total pulse cycle time statistically significant increased on both left and right chon, kwan,cheok. T4 time statistically significant increased on both left and right chon, kwan, cheok. T4-T1/T indexs except left cheokmaek, Right cheokmaek observation area decreased significantly in four sites.Wm(indicating high pressure retention time indexs increased significantly in the five sites were observed except right chon maek. Conclusions: Effect of pulse-wave factors in Middle Aged Women by Mountain Cultivated Ginseng Pharmacopuncture increased T, T4, Wm and decreased T4-T1/T indexs. The results of this experiment,Mountain Cultivated Ginseng Pharmacopuncture induced to increase the Pulse-wave's stability and strength.

Standard Test Method for Measuring Dose for Use in Linear Accelerator Pulsed Radiation Effects Tests

CERN Document Server

American Society for Testing and Materials. Philadelphia

2011-01-01

1.1 This test method covers a calorimetric measurement of the total dose delivered in a single pulse of electrons from an electron linear accelerator or a flash X-ray machine (FXR, e-beam mode) used as an ionizing source in radiation-effects testing. The test method is designed for use with pulses of electrons in the energy range from 10 to 50 MeV and is only valid for cases in which both the calorimeter and the test specimen to be irradiated are“thin” compared to the range of these electrons in the materials of which they are constructed. 1.2 The procedure described can be used in those cases in which (1) the dose delivered in a single pulse is 5 Gy (matl) (500 rd (matl)) or greater, or (2) multiple pulses of a lower dose can be delivered in a short time compared to the thermal time constant of the calorimeter. Matl refers to the material of the calorimeter. The minimum dose per pulse that can be acceptably monitored depends on the variables of the particular test, including pulse rate, pulse uniformity...

DogPulse

DEFF Research Database (Denmark)

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

2015-01-01

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

Investigation of the time evolution of plasma parameters in a pulsed magnetron discharge

Czech Academy of Sciences Publication Activity Database

Straňák, V.; Hubička, Zdeněk; Adámek, P.; Blažek, J.; Tichý, M.; Špatenka, P.; Hippler, R.; Wrehde, S.

2006-01-01

Roč. 56, - (2006), s. 1364-1370 ISSN 0011-4626 R&D Projects: GA ČR GA202/05/2242; GA ČR GA202/06/0776 Grant - others:Deutsche Forschungsgemeinschaft(DE) SFB/TR 24 Institutional research plan: CEZ:AV0Z10100522 Keywords : pulsed magnetron * time resolved measurements * Langmuir probe Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.568, year: 2006

The modified pulse-spray method using Urokinase in subacute and chronic thrombotic arterial occlusion

International Nuclear Information System (INIS)

Kim, Youn Kil; Hahn, Seong Tae; Baek, Jee Hee; Kim, Choon Yul; Shinn, Kyung Sub

1996-01-01

To evaluate the effectiveness and safety of the modified pulse-spray method using Urokinase(UK) in subacute and chronic thrombotic arterial occlusion. Modified pulse-spray methods using UK were performed in seven patients with subacute (1 week-1month) to chronic (1month-5years) occlusive symptoms such as limb pain, claudication and impotence. Angiographic examination revealed thrombotic occlusion of the aorta, common iliac arteries, brachial arterio-venous hemodialysis graft and femoro-popliteal bypass graft. The patients underwent thrombolysis using modified pulse-spray and additional constant infusion of UK. In the presence of underlying stenosis or organized clots, balloon angioplasty or stent placement was performed. Complete lysis was obtained in five of seven patients. For initial lysis, the mean dose of UK was 420,000 units, and the mean modified pulse-spray time was 50 minutes. Mean total dose of UK and mean total time for complete lysis were 800,000 units and 161 minutes, respectively. Thrombolysis of the femoro-popliteal bypass graft failed due to severe occlusion of the distal anastomosis. Partial lysis was achieved in one patient with aorto-illac occlusion, but further thrombolysis was stopped due to bleeding at the puncture site. The modified pulse-spray method using UK is effective in treating subacute and chronic arterial thrombotic occlusion. It augments the speed, safety and efficacy of thrombolysis. When underlying stenosis or organized clots remain after thrombolysis, ballon angioplasty or stent placement would be helpful

Magnetic pulse sharpener and delay-line

International Nuclear Information System (INIS)

Li Jin; Dai Guangsen; Xia Liansheng

2002-01-01

This paper describes a method to achieve short rise time pulse which has been delayed with a delay-line and magnetic pulse sharpener. A delay-line and two shock-lines are designed to carry pulsed signal with a maximum voltage magnitude up to 80 kV. A pulse of High voltage with arise time of 48 ns at a level of 0.1%-0.9% were achieved, and the attenuation in the line is very small

Compensation for the distortion in satellite laser range predictions due to varying pulse travel times

Science.gov (United States)

Paunonen, Matti

1993-01-01

A method for compensating for the effect of the varying travel time of a transmitted laser pulse to a satellite is described. The 'observed minus predicted' range differences then appear to be linear, which makes data screening or use in range gating more effective.

Influence of Actively Controlled Heat Release Timing on the Performance and Operational Characteristics of a Rotary Valve, Acoustically Resonant Pulse Combustor

KAUST Repository

Lisanti, Joel; Roberts, William L.

2017-01-01

The influence of heat release timing on the performance and operational characteristics of a rotary valve, acoustically resonant pulse combustor is investigated both experimentally and numerically. Simulation results are obtained by solving the quasi-1D Navier-Stokes equations with forced volumetric heat addition. Experimental efforts modify heat release timing through modulated fuel injection and modification of the fluid dynamic mixing. Results indicate that the heat release timing has a profound effect on the operation and efficiency of the pulse combustor and that this timing can be difficult to control experimentally.

Influence of Actively Controlled Heat Release Timing on the Performance and Operational Characteristics of a Rotary Valve, Acoustically Resonant Pulse Combustor

KAUST Repository

Lisanti, Joel

2017-01-05

The influence of heat release timing on the performance and operational characteristics of a rotary valve, acoustically resonant pulse combustor is investigated both experimentally and numerically. Simulation results are obtained by solving the quasi-1D Navier-Stokes equations with forced volumetric heat addition. Experimental efforts modify heat release timing through modulated fuel injection and modification of the fluid dynamic mixing. Results indicate that the heat release timing has a profound effect on the operation and efficiency of the pulse combustor and that this timing can be difficult to control experimentally.

Breakdown of methylene blue and methyl orange by pulsed corona discharge

Science.gov (United States)

Grabowski, L. R.; van Veldhuizen, E. M.; Pemen, A. J. M.; Rutgers, W. R.

2007-05-01

The recently developed corona above water technique is applied to water containing 10 mg l-1 methylene blue (MB) or methyl orange (MO). The corona discharge pulses are created with a spark gap switched capacitor followed by a transmission line transformer. The pulse amplitude is 40 kV; its duration is 50 ns. At a pulse repetition rate of 10 Hz this leads to an average power of 0.6 W into the discharge. MB and MO are completely decolourized in ~20 min. This corresponds to a yield of ~4.5 gr kW-1h-1, which is much higher than obtained with other discharge techniques or sonoluminescence. The high yield is reflected in the observed temperature increase of only ~1 K. Tests with additional chemicals show that the initial speed of the conversion can be influenced but the total time required for total decolourization is constant. Further, it follows that the main oxidation path of the dyes is by direct ozone attack and the conversion products are strong acids.

Breakdown of methylene blue and methyl orange by pulsed corona discharge

Energy Technology Data Exchange (ETDEWEB)

Grabowski, L R [Department of Applied Physics, Technische Universiteit Eindhoven (Netherlands); Veldhuizen, E M van [Department of Applied Physics, Technische Universiteit Eindhoven (Netherlands); Pemen, A J M [Department of Electrical Engineering, Technische Universiteit Eindhoven (Netherlands); Rutgers, W R [Department of Applied Physics, Technische Universiteit Eindhoven (Netherlands)

2007-05-15

The recently developed corona above water technique is applied to water containing 10 mg l{sup -1} methylene blue (MB) or methyl orange (MO). The corona discharge pulses are created with a spark gap switched capacitor followed by a transmission line transformer. The pulse amplitude is 40 kV; its duration is 50 ns. At a pulse repetition rate of 10 Hz this leads to an average power of 0.6 W into the discharge. MB and MO are completely decolourized in {approx}20 min. This corresponds to a yield of {approx}4.5 gr kW{sup -1}h{sup -1}, which is much higher than obtained with other discharge techniques or sonoluminescence. The high yield is reflected in the observed temperature increase of only {approx}1 K. Tests with additional chemicals show that the initial speed of the conversion can be influenced but the total time required for total decolourization is constant. Further, it follows that the main oxidation path of the dyes is by direct ozone attack and the conversion products are strong acids.

Breakdown of methylene blue and methyl orange by pulsed corona discharge

International Nuclear Information System (INIS)

Grabowski, L R; Veldhuizen, E M van; Pemen, A J M; Rutgers, W R

2007-01-01

The recently developed corona above water technique is applied to water containing 10 mg l -1 methylene blue (MB) or methyl orange (MO). The corona discharge pulses are created with a spark gap switched capacitor followed by a transmission line transformer. The pulse amplitude is 40 kV; its duration is 50 ns. At a pulse repetition rate of 10 Hz this leads to an average power of 0.6 W into the discharge. MB and MO are completely decolourized in ∼20 min. This corresponds to a yield of ∼4.5 gr kW -1 h -1 , which is much higher than obtained with other discharge techniques or sonoluminescence. The high yield is reflected in the observed temperature increase of only ∼1 K. Tests with additional chemicals show that the initial speed of the conversion can be influenced but the total time required for total decolourization is constant. Further, it follows that the main oxidation path of the dyes is by direct ozone attack and the conversion products are strong acids

SEARCH FOR A CORRELATION BETWEEN VERY-HIGH-ENERGY GAMMA RAYS AND GIANT RADIO PULSES IN THE CRAB PULSAR

Energy Technology Data Exchange (ETDEWEB)

Aliu, E. [Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027 (United States); Archambault, S. [Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada); Arlen, T. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Aune, T.; Bouvier, A. [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States); Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R. [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Benbow, W. [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States); Byrum, K. [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 (United States); Cesarini, A.; Connolly, M. P. [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland); Ciupik, L. [Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States); Collins-Hughes, E. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Cui, W. [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Duke, C. [Department of Physics, Grinnell College, Grinnell, IA 50112-1690 (United States); Dumm, J. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Falcone, A. [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); Federici, S., E-mail: schroedter@veritas.sao.arizona.edu, E-mail: mccann@kicp.uchicago.edu, E-mail: nepomuk.otte@gmail.com [DESY, Platanenallee 6, 15738 Zeuthen (Germany); and others

2012-12-01

We present the results of a joint observational campaign between the Green Bank radio telescope and the VERITAS gamma-ray telescope, which searched for a correlation between the emission of very-high-energy (VHE) gamma rays (E {sub {gamma}} > 150 GeV) and giant radio pulses (GRPs) from the Crab pulsar at 8.9 GHz. A total of 15,366 GRPs were recorded during 11.6 hr of simultaneous observations, which were made across four nights in 2008 December and in 2009 November and December. We searched for an enhancement of the pulsed gamma-ray emission within time windows placed around the arrival time of the GRP events. In total, eight different time windows with durations ranging from 0.033 ms to 72 s were positioned at three different locations relative to the GRP to search for enhanced gamma-ray emission which lagged, led, or was concurrent with, the GRP event. Furthermore, we performed separate searches on main pulse GRPs and interpulse GRPs and on the most energetic GRPs in our data sample. No significant enhancement of pulsed VHE emission was found in any of the preformed searches. We set upper limits of 5-10 times the average VHE flux of the Crab pulsar on the flux simultaneous with interpulse GRPs on single-rotation-period timescales. On {approx}8 s timescales around interpulse GRPs, we set an upper limit of 2-3 times the average VHE flux. Within the framework of recent models for pulsed VHE emission from the Crab pulsar, the expected VHE-GRP emission correlations are below the derived limits.

Search for a Correlation Between Very-High-Energy Gamma Rays and Giant Radio Pulses in the Crab Pulsar

Science.gov (United States)

Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Byrum, K.;

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

Science.gov (United States)

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

2010-02-01

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

Development of subpicosecond pulse radiolysis system

International Nuclear Information System (INIS)

Kozawa, T.; Saeki, A.; Okamoto, K.; Numata, Y.; Kaseda, K.; Yamamoto, T.; Suemine, S.; Yoshida, Y.; Tagawa, S.

2000-01-01

Subpicosecond pulse radiolysis system was developed to elucidate the primary processes of radiation chemistry in the time region of femtosecond. The system consists of a femtosecond electron linac as an irradiation source, a femtosecond laser as an analyzing light and a jitter compensation system which was designed to reduce the effect of jitter between an electron pulse and a laser pulse on the time resolution. The time resolution of 800 fs was achieved. (author)

Application of total care time and payment per unit time model for physician reimbursement for common general surgery operations.

Science.gov (United States)

Chatterjee, Abhishek; Holubar, Stefan D; Figy, Sean; Chen, Lilian; Montagne, Shirley A; Rosen, Joseph M; Desimone, Joseph P

2012-06-01

The relative value unit system relies on subjective measures of physician input in the care of patients. A payment per unit time model incorporates surgeon reimbursement to the total care time spent in the operating room, postoperative in-house, and clinic time to define payment per unit time. We aimed to compare common general surgery operations by using the total care time and payment per unit time method in order to demonstrate a more objective measurement for physician reimbursement. Average total physician payment per case was obtained for 5 outpatient operations and 4 inpatient operations in general surgery. Total care time was defined as the sum of operative time, 30 minutes per hospital day, and 30 minutes per office visit for each operation. Payment per unit time was calculated by dividing the physician reimbursement per case by the total care time. Total care time, physician payment per case, and payment per unit time for each type of operation demonstrated that an average payment per time spent for inpatient operations was $455.73 and slightly more at $467.51 for outpatient operations. Partial colectomy with primary anastomosis had the longest total care time (8.98 hours) and the least payment per unit time ($188.52). Laparoscopic gastric bypass had the highest payment per time ($707.30). The total care time and payment per unit time method can be used as an adjunct to compare reimbursement among different operations on an institutional level as well as on a national level. Although many operations have similar payment trends based on time spent by the surgeon, payment differences using this methodology are seen and may be in need of further review. Copyright © 2012 American College of Surgeons. Published by Elsevier Inc. All rights reserved.

Effect of Epidural Block under General Anesthesia on Pulse Transit Time

International Nuclear Information System (INIS)

Choi, Byeong Cheol; Kim, Seong Min; Jung, Dong Keun; Kim, Gi Ryon; Lee, He Jeong; Jeon, Gye Rock

2005-01-01

Epidural block under general anesthesia has been widely used to control postoperative pain. In this anesthetic state many hemodynamic parameters are changed. Moreover pulse transit time is influenced by this memodynamic change. PPT change in the finger and the toe due to relaxation of arterial wall muscle after general anesthesia and epidural block under general anesthesia. This study, in the both general anesthesia and epidural block under general anesthesia, ΔPTT of the toe and of the finger are measured. In addition, ΔPTT(toe-finger) of the epidural block under general anesthesia and of the general anesthesia were compared

Impact of non-white noises in pulse amplitude measurements: a time-domain approach

International Nuclear Information System (INIS)

Pullia, A.

1998-01-01

The contribution of the 1/f-noise to the spectral line broadening in pulse amplitude measurements is derived with a time-domain analysis. The known time-domain relationships which provide the contributions of the series and parallel white noises are generalised for the case of 1/f and other typical non-white noises, by using the fractional derivative of either the system impulse response (time-invariant linear filters) or its weight function folded (time-variant linear filters). It is shown that a time-domain approach is also effective to determine the contribution of Lorentzian noises. A simple rule suitable to derive numerically the fractional derivative is given, which permits to calculate the effect of non-white noises even when the filter impulse response is not known analytically but only in sampled form. (orig.)

Low-timing-jitter, stretched-pulse passively mode-locked fiber laser with tunable repetition rate and high operation stability

International Nuclear Information System (INIS)

Liu, Yuanshan; Zhang, Jian-Guo; Chen, Guofu; Zhao, Wei; Bai, Jing

2010-01-01

We design a low-timing-jitter, repetition-rate-tunable, stretched-pulse passively mode-locked fiber laser by using a nonlinear amplifying loop mirror (NALM), a semiconductor saturable absorber mirror (SESAM), and a tunable optical delay line in the laser configuration. Low-timing-jitter optical pulses are stably produced when a SESAM and a 0.16 m dispersion compensation fiber are employed in the laser cavity. By inserting a tunable optical delay line between NALM and SESAM, the variable repetition-rate operation of a self-starting, passively mode-locked fiber laser is successfully demonstrated over a range from 49.65 to 50.47 MHz. The experimental results show that the newly designed fiber laser can maintain the mode locking at the pumping power of 160 mW to stably generate periodic optical pulses with width less than 170 fs and timing jitter lower than 75 fs in the 1.55 µm wavelength region, when the fundamental repetition rate of the laser is continuously tuned between 49.65 and 50.47 MHz. Moreover, this fiber laser has a feature of turn-key operation with high repeatability of its fundamental repetition rate in practice

[Estimation of the atrioventricular time interval by pulse Doppler in the normal fetal heart].

Science.gov (United States)

Hamela-Olkowska, Anita; Dangel, Joanna

2009-08-01

To assess normative values of the fetal atrioventricular (AV) time interval by pulse-wave Doppler methods on 5-chamber view. Fetal echocardiography exams were performed using Acuson Sequoia 512 in 140 singleton fetuses at 18 to 40 weeks of gestation with sinus rhythm and normal cardiac and extracardiac anatomy. Pulsed Doppler derived AV intervals were measured from left ventricular inflow/outflow view using transabdominal convex 3.5-6 MHz probe. The values of AV time interval ranged from 100 to 150 ms (mean 123 +/- 11.2). The AV interval was negatively correlated with the heart rhythm (page of gestation (p=0.007). However, in the same subgroup of the fetal heart rate there was no relation between AV intervals and gestational age. Therefore, the AV intervals showed only the heart rate dependence. The 95th percentiles of AV intervals according to FHR ranged from 135 to 148 ms. 1. The AV interval duration was negatively correlated with the heart rhythm. 2. Measurement of AV time interval is easy to perform and has a good reproducibility. It may be used for the fetal heart block screening in anti-Ro and anti-La positive pregnancies. 3. Normative values established in the study may help obstetricians in assessing fetal abnormalities of the AV conduction.

The optimization of the time resolution and the sensitivity in the pulsed nuclear resonance

International Nuclear Information System (INIS)

Umathum, R.

1987-01-01

The time resolution of pulsed NMR spectrometer and its spectral sensitivity are closely connected together. An important obstacle in the attempt to increase the resolution represents the dead time of the spectrometer. In the present thesis therefore the different contributions to the system dead time and their causes are analyzed and ways to the reduction respectively complete removement of a part of these contributions are indicated. So a duplexer was developed and constructed on the base of a principle novel for the NMR under application of quadrature hybrids which reduces the residual voltage of the sender pulse to less than 1/10 of the hitherto reached value. In this thesis a concept is extensively discussed which allows to generate at constant quality respectively damping constant of the sample circuit and given sender power a larger high frequency field strength than it is possible in the state of the power fitting. It could be shown than also concerning the noise behaviour by the application of the principle of the defined misfit no compromise must be made but it is even facilitated to approach the ideal of the noise fit of the first receiver stage to the sample circuit. (orig./HSI) [de

A time-pulsed positronium beam and a study of oxides on silicon using positrons

International Nuclear Information System (INIS)

Khatri, R.K.

1993-01-01

The studies on rare gas solid moderators were carried out with a 350 μCi 22 Na radioactive source. The corrected efficiency for neon moderator in conical geometrical configuration was as high as (1.4 ± 0.2)%. The conical configuration moderator performed better by a factor of (2.2 ± 0.2) than the cylindrical configuration. A time pulsed positron beam was built to carry out investigations on the positronium formation processes and positronium beam. This beam has the capability to store low energy e + in a magnetic bottle, with a magnetic bottle at one end and an electrostatic mirror at the other. These stored e + are then bunched to form a pulse with a buncher. The bunched beam had a FWHM of 17 nsec and contained 1 to 2 e + /pulse. A thin carbon foil of 50 angstrom thickness was used for positronium formation by process of charge exchange. Positronium Annihilation Spectroscopy (PAS) was utilized to carry out studies on the activation energy of hydrogen at the interface of oxide and silicon substrate and the effect of irradiation on the oxides in SiO 2 /Si(100) sample. The activation energy of hydrogen at the interface of SiO 2 /Si(100) samples with n- and p-type substrate was measured to be 2.60(6) eV and 2.47(6) eV respectively. The investigations of the samples irradiated with x-ray and γ-ray led to the first time identification of creation of E' centers with PAS

Third-harmonic generation in isotropic media by focused pulses

International Nuclear Information System (INIS)

Tasgal, Richard S.; Band, Y.B.

2004-01-01

For focused pulses of light in isotropic nonlinear media, third-harmonic generation can be strongly affected by group-velocity mismatch between the fundamental and third-harmonic. There is a characteristic time determined by the group-velocity mismatch and the Rayleigh range of the focused pulse. The dynamics depend on two dimensionless quantities, namely the ratio of the characteristic time to the pulse duration and the phase-velocity mismatch times the Rayleigh range. Pulses shorter than the characteristic time have physics described by simple analytic formulas. Pulses near the characteristic time have an intermediate behavior given by an explicit but more complicated formula. Pulses longer than the characteristic time tend to the continuous-wave case

Optical pulse compression

International Nuclear Information System (INIS)

Glass, A.J.

1975-01-01

The interest in using large lasers to achieve a very short and intense pulse for generating fusion plasma has provided a strong impetus to reexamine the possibilities of optical pulse compression at high energy. Pulse compression allows one to generate pulses of long duration (minimizing damage problems) and subsequently compress optical pulses to achieve the short pulse duration required for specific applications. The ideal device for carrying out this program has not been developed. Of the two approaches considered, the Gires--Tournois approach is limited by the fact that the bandwidth and compression are intimately related, so that the group delay dispersion times the square of the bandwidth is about unity for all simple Gires--Tournois interferometers. The Treacy grating pair does not suffer from this limitation, but is inefficient because diffraction generally occurs in several orders and is limited by the problem of optical damage to the grating surfaces themselves. Nonlinear and parametric processes were explored. Some pulse compression was achieved by these techniques; however, they are generally difficult to control and are not very efficient. (U.S.)

The detection and estimation of spurious pulses

International Nuclear Information System (INIS)

1976-01-01

Spurious pulses which may interfere with the counting of particles can sometimes easily be detected by integral counting as a function of amplification or by pulse-height analysis. However, in order to estimate their count rate, more elaborate methods based on their time relationship are needed. Direct techniques (delayed coincidences, use of a multichannel analyser in time mode, time-to-amplitude conversion) and gating techniques (simple subtraction, correlation counting, pulsed sources, modulo counting) are discussed. These techniques are compared to each other and their application to various detectors is studied as well as the influence of a dead time on spurious pulses

Experimental time resolved measurement of fluence and energy spectra of photons emitted by a pulsed X-ray generator in the range 5-300 keV

International Nuclear Information System (INIS)

Vie, M.; Baboulet, J.P.

1989-01-01

We have developed: - A sensor to measure locally X ray fluence rate amplitude and variation versus time during X ray pulses, - A spectrometer based on ROSS method to measure absolute X ray spectrum versus time during X ray pulses. This metrology is used to characterise single shot X ray pulsed sources emitting photons in the range of 5 to 300 keV. Fluence domain is between 10 -9 and 5 10 -4 J. cm -2 with a few nanoseconds time resolution [fr

Total sitting time, leisure time physical activity and risk of hospitalization due to low back pain

DEFF Research Database (Denmark)

Balling, Mie; Holmberg, Teresa; Petersen, Christina B

2018-01-01

AIMS: This study aimed to test the hypotheses that a high total sitting time and vigorous physical activity in leisure time increase the risk of low back pain and herniated lumbar disc disease. METHODS: A total of 76,438 adults answered questions regarding their total sitting time and physical...... activity during leisure time in the Danish Health Examination Survey 2007-2008. Information on low back pain diagnoses up to 10 September 2015 was obtained from The National Patient Register. The mean follow-up time was 7.4 years. Data were analysed using Cox regression analysis with adjustment...... disc disease. However, moderate or vigorous physical activity, as compared to light physical activity, was associated with increased risk of low back pain (HR = 1.16, 95% CI: 1.03-1.30 and HR = 1.45, 95% CI: 1.15-1.83). Moderate, but not vigorous physical activity was associated with increased risk...

Ultrashort X-ray pulse science

Energy Technology Data Exchange (ETDEWEB)

Chin, Alan Hap [Univ. of California, Berkeley, CA (US). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

1998-05-01

A variety of phenomena involves atomic motion on the femtosecond time-scale. These phenomena have been studied using ultrashort optical pulses, which indirectly probe atomic positions through changes in optical properties. Because x-rays can more directly probe atomic positions, ultrashort x-ray pulses are better suited for the study of ultrafast structural dynamics. One approach towards generating ultrashort x-ray pulses is by 90° Thomson scattering between terawatt laser pulses and relativistic electrons. Using this technique, the author generated ~ 300 fs, 30 keV (0.4 Å) x-ray pulses. These x-ray pulses are absolutely synchronized with ultrashort laser pulses, allowing femtosecond optical pump/x-ray probe experiments to be performed. Using the right-angle Thomson scattering x-ray source, the author performed time-resolved x-ray diffraction studies of laser-perturbated InSb. These experiments revealed a delayed onset of lattice expansion. This delay is due to the energy relaxation from a dense electron-hole plasma to the lattice. The dense electron-hole plasma first undergoes Auger recombination, which reduces the carrier concentration while maintaining energy content. Longitudinal-optic (LO) phonon emission then couples energy to the lattice. LO phonon decay into acoustic phonons, and acoustic phonon propagation then causes the growth of a thermally expanded layer. Source characterization is instrumental in utilizing ultrashort x-ray pulses in time-resolved x-ray spectroscopies. By measurement of the electron beam diameter at the generation point, the pulse duration of the Thomson scattered x-rays is determined. Analysis of the Thomson scattered x-ray beam properties also provides a novel means of electron bunch characterization. Although the pulse duration is inferred for the Thomson scattering x-ray source, direct measurement is required for other x-ray pulse sources. A method based on the laser-assisted photoelectric effect (LAPE) has been demonstrated as a

Ultrashort X-ray pulse science

International Nuclear Information System (INIS)

Chin, A.H.; Lawrence Berkeley National Lab., CA

1998-01-01

A variety of phenomena involves atomic motion on the femtosecond time-scale. These phenomena have been studied using ultrashort optical pulses, which indirectly probe atomic positions through changes in optical properties. Because x-rays can more directly probe atomic positions, ultrashort x-ray pulses are better suited for the study of ultrafast structural dynamics. One approach towards generating ultrashort x-ray pulses is by 90 o Thomson scattering between terawatt laser pulses and relativistic electrons. Using this technique, the author generated ∼ 300 fs, 30 keV (0.4 (angstrom)) x-ray pulses. These x-ray pulses are absolutely synchronized with ultrashort laser pulses, allowing femtosecond optical pump/x-ray probe experiments to be performed. Using the right-angle Thomson scattering x-ray source, the author performed time-resolved x-ray diffraction studies of laser-perturbated InSb. These experiments revealed a delayed onset of lattice expansion. This delay is due to the energy relaxation from a dense electron-hole plasma to the lattice. The dense electron-hole plasma first undergoes Auger recombination, which reduces the carrier concentration while maintaining energy content. Longitudinal-optic (LO) phonon emission then couples energy to the lattice. LO phonon decay into acoustic phonons, and acoustic phonon propagation then causes the growth of a thermally expanded layer. Source characterization is instrumental in utilizing ultrashort x-ray pulses in time-resolved x-ray spectroscopies. By measurement of the electron beam diameter at the generation point, the pulse duration of the Thomson scattered x-rays is determined. Analysis of the Thomson scattered x-ray beam properties also provides a novel means of electron bunch characterization. Although the pulse duration is inferred for the Thomson scattering x-ray source, direct measurement is required for other x-ray pulse sources. A method based on the laser-assisted photoelectric effect (LAPE) has been

A compact high-voltage pulse generator based on pulse transformer with closed magnetic core.

Science.gov (United States)

Zhang, Yu; Liu, Jinliang; Cheng, Xinbing; Bai, Guoqiang; Zhang, Hongbo; Feng, Jiahuai; Liang, Bo

2010-03-01

A compact high-voltage nanosecond pulse generator, based on a pulse transformer with a closed magnetic core, is presented in this paper. The pulse generator consists of a miniaturized pulse transformer, a curled parallel strip pulse forming line (PFL), a spark gap, and a matched load. The innovative design is characterized by the compact structure of the transformer and the curled strip PFL. A new structure of transformer windings was designed to keep good insulation and decrease distributed capacitance between turns of windings. A three-copper-strip structure was adopted to avoid asymmetric coupling of the curled strip PFL. When the 31 microF primary capacitor is charged to 2 kV, the pulse transformer can charge the PFL to 165 kV, and the 3.5 ohm matched load can deliver a high-voltage pulse with a duration of 9 ns, amplitude of 84 kV, and rise time of 5.1 ns. When the load is changed to 50 ohms, the output peak voltage of the generator can be 165 kV, the full width at half maximum is 68 ns, and the rise time is 6.5 ns.

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Optical pulse multiplication and temporal coding using true time delay achieved by long-period fiber gratings in dispersion compensating fiber.

Science.gov (United States)

Eom, Tae Joong; Kim, Sun-Jong; Kim, Tae-Young; Park, Chang-Soo; Lee, Byeong

2004-12-27

We present an optical pulse multiplication and a temporal coding method for OCDMA systems. The true time delay among the pulses was obtained by utilizing the difference in the propagation speeds of the core and the co-propagating cladding modes coupled by long-period fiber gratings. By cascadin gratings we could get an equally spaced 40 GHz pulse train from a 10 GHz train. Various coding and decoding of a pulse train were possible by controlling the separations among the gratings. The dispersion compensating fiber having an inner cladding structure enabled to have the gratings that were not sensitive to the polymer jacket of the fiber and allowed shortening the device length.

Quality stability and sensory attributes of apple juice processed by thermosonication, pulsed electric field and thermal processing.

Science.gov (United States)

Sulaiman, Alifdalino; Farid, Mohammed; Silva, Filipa Vm

2017-04-01

Worldwide, apple juice is the second most popular juice, after orange juice. It is susceptible to enzymatic browning spoilage by polyphenoloxidase, an endogenous enzyme. In this study, Royal Gala apple juice was treated by thermosonication (TS: 1.3 W/mL, 58 ℃, 10 min), pulsed electric field (PEF: 24.8 kV/cm, 60 pulses, 169 µs treatment time, 53.8 ℃) and heat (75 ℃, 20 min) and stored at 3.0 ℃ and 20.0 ℃ for 30 days. A sensory analysis was carried out after processing. The polyphenoloxidase activity, antioxidant activity and total color difference of the apple juice were determined before and after processing and during storage. The sensory analysis revealed that thermosonication and pulsed electric field juices tasted differently from the thermally treated juice. Apart from the pulsed electric field apple juice stored at room temperature, the processed juice was stable during storage, since the pH and soluble solids remained constant and fermentation was not observed. Polyphenoloxidase did not reactivate during storage. Along storage, the juices' antioxidant activity decreased and total color difference increased (up to 6.8). While the antioxidant activity increased from 86 to 103% with thermosonication and was retained after pulsed electric field, thermal processing reduced it to 67%. The processing increased the total color difference slightly. No differences in the total color difference of the juices processed by the three methods were registered after storage. Thermosonication and pulsed electric field could possibly be a better alternative to thermal preservation of apple juice, but refrigerated storage is recommended for pulsed electric field apple juice.

Linear induction accelerators made from pulse-line cavities with external pulse injection

International Nuclear Information System (INIS)

Smith, I.

1979-01-01

Two types of linear induction accelerator have been reported previously. In one, unidirectional voltage pulses are generated outside the accelerator and injected into the accelerator cavity modules, which contain ferromagnetic material to reduce energy losses in the form of currents induced, in parallel with the beam, in the cavity structure. In the other type, the accelerator cavity modules are themselves pulse-forming lines with energy storage and switches; parallel current losses are made zero by the use of circuits that generate bidirectional acceleration waveforms with a zero voltage-time integral. In a third type of design described here, the cavities are externally driven, and 100% efficient coupling of energy to the beam is obtained by designing the external pulse generators to produce bidirectional voltage waveforms with zero voltage-time integral. A design for such a pulse generator is described that is itself one hundred percent efficient and which is well suited to existing pulse power techniques. Two accelerator cavity designs are described that can couple the pulse from such a generator to the beam; one of these designs provides voltage doubling. Comparison is made between the accelerating gradients that can be obtained with this and the preceding types of induction accelerator

Two-electron time-delay interference in atomic double ionization by attosecond pulses

Energy Technology Data Exchange (ETDEWEB)

Rescigno, Thomas N

2009-10-04

A two-color two-photon atomic double ionization experiment using subfemtosecond UV pulses can be designed such that the sequential two-color process dominates and one electron is ejected by each pulse. Nonetheless, ab initio calculations show that, for sufficiently short pulses, a prominent interference pattern in the joint energy distribution of the sequentially ejected electrons can be observed that is due to their indistinguishability and the exchange symmetry of the wave function.

Two-Electron Time-Delay Interference in Atomic Double Ionization by Attosecond Pulses

International Nuclear Information System (INIS)

Palacios, A.; Rescigno, T. N.; McCurdy, C. W.

2009-01-01

A two-color two-photon atomic double ionization experiment using subfemtosecond uv pulses can be designed such that the sequential two-color process dominates and one electron is ejected by each pulse. Nonetheless, ab initio calculations show that, for sufficiently short pulses, a prominent interference pattern in the joint energy distribution of the sequentially ejected electrons can be observed that is due to their indistinguishability and the exchange symmetry of the wave function.

A Markov Chain approach for deriving the statistics of time-correlated pulses in the presence of non-extendible dead time

International Nuclear Information System (INIS)

Degweker, S.B.

1996-01-01

The problem of deriving the statistics of time-correlated detector pulses in the presence of a non-extendible dead time is studied by constructing a Markov Chain to describe the process. Expressions for the transition matrix are derived for problems in the passive neutron assay of Pu and (zero-power) reactor noise. Perturbative and numerical solutions of the master equations are discussed for a simple problem in the passive neutron assay of Pu. Expressions for the mean count rate and variance in a given interval are derived. (Author)

A compact bipolar pulse-forming network-Marx generator based on pulse transformers.

Science.gov (United States)

Zhang, Huibo; Yang, Jianhua; Lin, Jiajin; Yang, Xiao

2013-11-01

A compact bipolar pulse-forming network (PFN)-Marx generator based on pulse transformers is presented in this paper. The high-voltage generator consisted of two sets of pulse transformers, 6 stages of PFNs with ceramic capacitors, a switch unit, and a matched load. The design is characterized by the bipolar pulse charging scheme and the compact structure of the PFN-Marx. The scheme of bipolar charging by pulse transformers increased the withstand voltage of the ceramic capacitors in the PFNs and decreased the number of the gas gap switches. The compact structure of the PFN-Marx was aimed at reducing the parasitic inductance in the generator. When the charging voltage on the PFNs was 35 kV, the matched resistive load of 48 Ω could deliver a high-voltage pulse with an amplitude of 100 kV. The full width at half maximum of the load pulse was 173 ns, and its rise time was less than 15 ns.

Study on the behaviour of timing photomultipliers at a high counting rate

International Nuclear Information System (INIS)

Gladyshev, D.A.; Li, B.N.; Yunusov, Kh.R.

1978-01-01

Variations in the amplification factor K of a photomultiplier (PMU) with the accuracy of 1% in a pulse mode are studied. Measurements were performed by means of a light pulse generator based on a light diode which generates pulses at the repetition rate of 250-10 5 pulse/s. Relative variations in K were determined by the position of the peak gravity centre from the light diode using a pulse analyzer and a frequency meter. Results of PM testing show that, at a sudden counting rate increase, the amplification increases during the time period less than, the measurement time (less than 1 s) and returns to the stationary value. When the counting rate returns from 10 5 pulse/s to the initial value of 250 pulse/s, the amplification decreases and than increases to stationary value. The total time of K stabilization after counting rate applying constitutes 10-70 min. Restoration of K after counting rate removal occurs to be much slower, during 3 hr. 40 min. K values varied from 1 to 12%

One nanosecond pulsed electron gun systems

International Nuclear Information System (INIS)

Koontz, R.F.

1979-02-01

At SLAC there has been a continuous need for the injection of very short bunches of electrons into the accelerator. Several time-of-flight experiments have used bursts of short pulses during a normal 1.6 micro-second rf acceleration period. Single bunch beam loading experiments made use of a short pulse injection system which included high power transverse beam chopping equipment. Until the equipment described in this paper came on line, the basic grid-controlled gun pulse was limited to a rise time of 7 nanoseconds and a pulse width of 10 nanoseconds. The system described here has a grid-controlled rise time of less than 500 pico-seconds, and a minimum pulse width of less than 1 nanosecond. Pulse burst repetition rate has been demonstrated above 20 MHz during a 1.6 microsecond rf accelerating period. The order-of-magnitude increase in gun grid switching speed comes from a new gun design which minimizes lead inductance and stray capacitance, and also increases gun grid transconductance. These gun improvements coupled with a newly designed fast pulser mounted directly within the gun envelope make possible subnanosecond pulsing of the gun

Real-time lossless data compression techniques for long-pulse operation

International Nuclear Information System (INIS)

Jesus Vega, J.; Sanchez, E.; Portas, A.; Pereira, A.; Ruiz, M.

2006-01-01

Data logging and data distribution will be two main tasks connected with data handling in ITER. Data logging refers to the recovery and ultimate storage of all data, independent on the data source. Control data and physics data distribution is related, on the one hand, to the on-line data broadcasting for immediate data availability for both data analysis and data visualization. On the other hand, delayed analyses require off-line data access. Due to the large data volume expected, data compression will be mandatory in order to save storage and bandwidth. On-line data distribution in a long pulse environment requires the use of a deterministic approach to be able to ensure a proper response time for data availability. However, an essential feature for all the above purposes is to apply compression techniques that ensure the recovery of the initial signals without spectral distortion when compacted data are expanded (lossless techniques). Delta compression methods are independent on the analogue characteristics of waveforms and there exist a variety of implementations that have been applied to the databases of several fusion devices such as Alcator, JET and TJ-II among others. Delta compression techniques are carried out in a two step algorithm. The first step consists of a delta calculation, i.e. the computation of the differences between the digital codes of adjacent signal samples. The resultant deltas are then encoded according to constant- or variable-length bit allocation. Several encoding forms can be considered for the second step and they have to satisfy a prefix code property. However, and in order to meet the requirement of on-line data distribution, the encoding forms have to be defined prior to data capture. This article reviews different lossless data compression techniques based on delta compression. In addition, the concept of cyclic delta transformation is introduced. Furthermore, comparative results concerning compression rates on different

Time resolved study of the emission enhancement mechanisms in orthogonal double-pulse laser-induced breakdown spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Sanginés, R., E-mail: roberto.sangines@ccadet.unam.mx; Sobral, H.

2013-10-01

The evolution of laser induced ablation plume on aluminum targets has been investigated in orthogonal pre-ablation double pulse scheme at atmospheric pressure from the earliest stages of plasma evolution. Time-resolved emission spectra from neutrals, singly- and doubly-ionized species obtained with the double pulse experiment have been compared with those from the single pulse configuration. Signal-to-noise enhancement reaches values of up to 15 depending on the analyzed species; and the lower the charge state the later its maximum signal-to-noise ratio is reached. Ablation plume dynamics was monitored from 10 ns after the plasma onset via shadowgraphy and fast-photography with narrow interference filters to follow the evolution of individual species. Results show that ionic species from the target are located at the plasma core while nitrogen from the background air is found at the plume peripheral. Initially both configurations exhibit similar ablation plume sizes and their expansions were successfully fitted with the strong explosion model for the first 500 ns. At later times a good agreement was obtained by using the drag model, which predicts that the plume expansion eventually stops due to interaction with the background gas particles. The emission enhancement measured in the double pulse scheme is discussed in terms of the models describing the plume dynamics. - Highlights: • Production of 2 + ions at the earliest stages of plasma evolution • The higher the charge state the inner the location within the ablation plume. • The expansion rate of the second (ablation) plume was measured. • Shock and drag models successfully fit the ablation shock front expansion.

Pulsed energy storage antennas for ionospheric modification

Directory of Open Access Journals (Sweden)

R. F. Wuerker

2005-01-01

Full Text Available Interesting, "new", very high peak-power pulsed radio frequency (RF antennas have been assembled at the HIPAS Observatory (Alaska, USA and also at the University of California at Los Angeles (UCLA, USA; namely, a pair of quarter wavelength (λ/4 long cylindrical conductors separated by a high voltage spark gap. Such a combination can radiate multi-megawatt RF pulses whenever the spark gap fires. The antenna at HIPAS is 53m long (λ/2 with a central pressurized SF₆ spark gap. It is mounted 5 meters (λ/21 above a ground plane. It radiates at 2.85MHz. The two antenna halves are charged to ± high voltages by a Tesla coil. Spark gap voltages of 0.4 MV (at the instant of spark gap closure give peak RF currents of ~1200A which correspond to ~14 MW peak total radiated power, or ~56 MW of Effective Radiated Power (ERP. The RF pulse train is initially square, decaying exponentially in time with Qs of ~50. Two similar but smaller 80-MHz antennas were assembled at UCLA to demonstrate their synchronization with a pulsed laser which fired the spark gaps in the two antennas simultanoeously. These experiments show that one can anticipate a pulsed array of laser synchronized antennas having a coherent Effective Radiated Power (ERP>10GW. One can even reconsider a pulse array radiating at 1.43MHz which corresponds to the electron gyrofrequency in the Earth's magnetic field at ~200km altitude. These "new" pulsed high power antennas are hauntingly similar to the ones used originally by Hertz (1857-1894 during his (1886-1889 seminal verifications of Maxwell's (1864 theory of electrodynamics.

Pulsed energy storage antennas for ionospheric modification

Directory of Open Access Journals (Sweden)

R. F. Wuerker

2005-01-01

Full Text Available Interesting, "new", very high peak-power pulsed radio frequency (RF antennas have been assembled at the HIPAS Observatory (Alaska, USA and also at the University of California at Los Angeles (UCLA, USA; namely, a pair of quarter wavelength (λ/4 long cylindrical conductors separated by a high voltage spark gap. Such a combination can radiate multi-megawatt RF pulses whenever the spark gap fires. The antenna at HIPAS is 53m long (λ/2 with a central pressurized SF6 spark gap. It is mounted 5 meters (λ/21 above a ground plane. It radiates at 2.85MHz. The two antenna halves are charged to ± high voltages by a Tesla coil. Spark gap voltages of 0.4 MV (at the instant of spark gap closure give peak RF currents of ~1200A which correspond to ~14 MW peak total radiated power, or ~56 MW of Effective Radiated Power (ERP. The RF pulse train is initially square, decaying exponentially in time with Qs of ~50. Two similar but smaller 80-MHz antennas were assembled at UCLA to demonstrate their synchronization with a pulsed laser which fired the spark gaps in the two antennas simultanoeously. These experiments show that one can anticipate a pulsed array of laser synchronized antennas having a coherent Effective Radiated Power (ERP>10GW. One can even reconsider a pulse array radiating at 1.43MHz which corresponds to the electron gyrofrequency in the Earth's magnetic field at ~200km altitude. These "new" pulsed high power antennas are hauntingly similar to the ones used originally by Hertz (1857-1894 during his (1886-1889 seminal verifications of Maxwell's (1864 theory of electrodynamics.

Pulse radiolysis study of monomer and dimer cations of styrene, 1-methylstyrene and 1,1'-diphenylethylene

International Nuclear Information System (INIS)

Mehnert, R.; Helmstreit, W.; Boes, J.; Brede, O.

1977-01-01

In pulse-irradiated solutions of styrene, 1-methylstyrene and 1,1'-diphenylethylene, the decay kinetics of the olefin monomer cations and the formation kinetics of the corresponding dimer cations have been studied at room temperature. The solutions were irradiated with 15-nsec 15-ampere pulses of 1-MeV electrons from an Elit-type accelerator. The total dose per pulse was approximately 10 krad. The monomer cations were generated with rate constants of about 10 11 M -1 sec -1 . From the time decay of the monomer light absorption and the growth in time of the dimer absorption rate constants for the dimer formation between 0.8x10 10 and 1.2x10 10 M -1 sec -1 have been determined. (T.I.)

NO kinetics in pulsed low-pressure nitrogen plasmas studied by time resolved quantum cascade laser absorption spectroscopy

NARCIS (Netherlands)

Welzel, S.; Guaitella, O.; Lazzaroni, C.; Pintassilgo, C.; Rousseau, A.; Röpcke, J.

2011-01-01

Time-resolved quantum cascade laser absorption spectroscopy at 1897 cm-1 (5.27 µm) has been applied to study the NO(X) kinetics on the micro- and millisecond time scale in pulsed low-pressure N2/NO dc discharges. Experiments have been performed under flowing and static gas conditions to infer the

Pulsed-laser time-resolved thermal mirror technique in low-absorbance homogeneous linear elastic materials.

Science.gov (United States)

Lukasievicz, Gustavo V B; Astrath, Nelson G C; Malacarne, Luis C; Herculano, Leandro S; Zanuto, Vitor S; Baesso, Mauro L; Bialkowski, Stephen E

2013-10-01

A theoretical model for a time-resolved photothermal mirror technique using pulsed-laser excitation was developed for low absorption samples. Analytical solutions to the temperature and thermoelastic deformation equations are found for three characteristic pulse profiles and are compared to finite element analysis methods results for finite samples. An analytical expression for the intensity of the center of a continuous probe laser at the detector plane is derived using the Fresnel diffraction theory, which allows modeling of experimental results. Experiments are performed in optical glasses, and the models are fitted to the data. The parameters of the fit are in good agreement with previous literature data for absorption, thermal diffusion, and thermal expansion of the materials tested. The combined modeling and experimental techniques are shown to be useful for quantitative determination of the physical properties of low absorption homogeneous linear elastic material samples.

Contrast enhancement in an optical time-domain reflectometer via self-phase modulation compensation by chirped probe pulses

International Nuclear Information System (INIS)

Alekseev, A E; Potapov, V T; Vdovenko, V S; Simikin, D E; Gorshkov, B G

2016-01-01

In the present paper we propose a novel method for optical time-domain reflectometer (OTDR)–reflectogram contrast enhancement via compensation of nonlinear distortions of propagating probe pulse, which arise due to the self-phase modulation (SPM) effect in optical fiber. The compensation is performed via preliminary frequency modulation (chirp) of the initial probe pulse according to the specific law. As a result the OTDR contrast at some distant predefined fiber point is fully restored to the value of non-distorted probe pulse at the beginning of the fiber line. As a result, the performance of the phase OTDR increases. The point of full SPM compensation could be shifted to any other point of the fiber line via preliminary frequency modulation index change. The feasibility of the proposed method is theoretically proved and experimentally demonstrated. (paper)

Numerical Analysis of Through Transmission Pulsed Eddy Current Testing and Effects of Pulse Width Variation

International Nuclear Information System (INIS)

Shin, Young Kil; Choi, Dong Myung

2007-01-01

By using numerical analysis methods, through transmission type pulsed eddy current (PEC) testing is modeled and PEC signal responses due to varying material conductivity, permeability, thickness, lift-off and pulse width are investigated. Results show that the peak amplitude of PEC signal gets reduced and the time to reach the peak amplitude is increased as the material conductivity, permeability, and specimen thickness increase. Also, they indicate that the pulse width needs to be shorter when evaluating the material conductivity and the plate thickness using the peak amplitude, and when the pulse width is long, the peak time is found to be more useful. Other results related to lift-off variation are reported as well

Pulse shape discrimination based on fast signals from silicon photomultipliers

Science.gov (United States)

Yu, Junhao; Wei, Zhiyong; Fang, Meihua; Zhang, Zixia; Cheng, Can; Wang, Yi; Su, Huiwen; Ran, Youquan; Zhu, Qingwei; Zhang, He; Duan, Kai; Chen, Ming; Liu, Meng

2018-06-01

Recent developments in organic plastic scintillators capable of pulse shape discrimination (PSD) enable a breakthrough in discrimination between neutrons and gammas. Plastic scintillator detectors coupled with silicon photomultipliers (SiPMs) offer many advantages, such as lower power consumption, smaller volume, and especially insensitivity to magnetic fields, compared with conventional photomultiplier tubes (PMTs). A SensL SiPM has two outputs: a standard output and a fast output. It is known that the charge injected into the fast output electrode is typically approximately 2% of the total charge generated during the avalanche, whereas the charge injected into the standard output electrode is nearly 98% of the total. Fast signals from SiPMs exhibit better performance in terms of timing and time-correlated measurements compared with standard signals. The pulse duration of a standard signal is on the order of hundreds of nanoseconds, whereas the pulse duration of the main monopole waveform of a fast signal is a few tens of nanoseconds. Fast signals are traditionally thought to be suitable for photon counting at very high speeds but unsuitable for PSD due to the partial charge collection. Meanwhile, the standard outputs of SiPMs coupled with discriminating scintillators have yielded nice PSD performances, but there have been no reports on PSD using fast signals. Our analysis shows that fast signals can also provide discrimination if the rate of charge injection into the fast output electrode is fixed for each event, even though only a portion of the charge is collected. In this work, we achieved successful PSD using fast signals; meanwhile, using a coincidence timing window of less 3 nanoseconds between the readouts from both ends of the detector reduced the influence of the high SiPM dark current. We experimentally achieved good timing performance and PSD capability simultaneously.

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

Science.gov (United States)

Wang, Xu; Wada, Naoya

2007-06-11

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

Investigation of the Effect of Finite Pulse Errors on BABA Pulse Sequence Using Floquet-Magnus Expansion Approach.

Science.gov (United States)

Mananga, Eugene S; Reid, Alicia E

This paper presents the study of finite pulse widths for the BABA pulse sequence using the Floquet-Magnus expansion (FME) approach. In the FME scheme, the first order F 1 is identical to its counterparts in average Hamiltonian theory (AHT) and Floquet theory (FT). However, the timing part in the FME approach is introduced via the Λ 1 ( t ) function not present in other schemes. This function provides an easy way for evaluating the spin evolution during "the time in between" through the Magnus expansion of the operator connected to the timing part of the evolution. The evaluation of Λ 1 ( t ) is useful especially for the analysis of the non-stroboscopic evolution. Here, the importance of the boundary conditions, which provides a natural choice of Λ 1 (0) is ignored. This work uses the Λ 1 ( t ) function to compare the efficiency of the BABA pulse sequence with δ - pulses and the BABA pulse sequence with finite pulses. Calculations of Λ 1 ( t ) and F 1 are presented.

Optimization methods of pulse-to-pulse alignment using femtosecond pulse laser based on temporal coherence function for practical distance measurement

Science.gov (United States)

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

2018-02-01

An interferometer technique based on temporal coherence function of femtosecond pulses is demonstrated for practical distance measurement. Here, the pulse-to-pulse alignment is analyzed for large delay distance measurement. Firstly, a temporal coherence function model between two femtosecond pulses is developed in the time domain for the dispersive unbalanced Michelson interferometer. Then, according to this model, the fringes analysis and the envelope extraction process are discussed. Meanwhile, optimization methods of pulse-to-pulse alignment for practical long distance measurement are presented. The order of the curve fitting and the selection of points for envelope extraction are analyzed. Furthermore, an averaging method based on the symmetry of the coherence function is demonstrated. Finally, the performance of the proposed methods is evaluated in the absolute distance measurement of 20 μ m with path length difference of 9 m. The improvement of standard deviation in experimental results shows that these approaches have the potential for practical distance measurement.

Time-dependent flux from pulsed neutrons revealed by superconducting Nb current-biased kinetic inductance detector with "1"0B converter operated at 4 K

International Nuclear Information System (INIS)

Miyajima, Shigeyuki; Narukami, Yoshito; Shishido, Hiroaki; Yoshioka, Naohito; Ishida, Takekazu; Fujimaki, Akira; Hidaka, Mutsuo; Oikawa, Kenichi; Harada, Masahide; Oku, Takayuki; Arai, Masatoshi

2015-01-01

We have demonstrated a new superconducting detector for a neutron based on Nb superconductor meanderline with a "1"0B conversion layer. We use a current-biased kinetic inductance detector (CB-KID), which is composed of a meanderline, for detection of a neutron with high spatial resolution and fast response. The thickness of Nb meanderlines is 40 nm and widths are 3 μm, 1 μm, and 0.6 μm. The CB-KIDs are fabricated at the center of the Si chip of the size 22 mm × 22 mm and the total area of CB-KIDs covers 8 mm × 8 mm. The chip was cooled to a temperature lower than 4 K below the transition temperature of Nb using a Gifford-McMahon (GM) cryocooler. The Nb CB-KIDs with a "1"0B conversion layer output the voltage by irradiating pulsed neutrons at the material life science experimental facility (MLF) of Japan Proton Accelerator Research Complex (J-PARC) center. The response time of CB-KIDs is about a few tens ns. We have also obtained the time dependence of neutron flux generated from pulsed neutrons using a CB-KID. Experimental results were in good agreement with the simulated results. (author)

Software emulator of nuclear pulse generation with different pulse shapes and pile-up

Energy Technology Data Exchange (ETDEWEB)

Pechousek, Jiri, E-mail: jiri.pechousek@upol.cz [Department of Experimental Physics, Faculty of Science, Palacky University, 17. listopadu 1192/12, 771 46 Olomouc (Czech Republic); Konecny, Daniel [Department of Optics, Faculty of Science, Palacky University, 17. listopadu 1192/12, 77 146 Olomouc (Czech Republic); Novak, Petr; Kouril, Lukas; Kohout, Pavel [Department of Experimental Physics, Faculty of Science, Palacky University, 17. listopadu 1192/12, 771 46 Olomouc (Czech Republic); Celiktas, Cuneyt [Department of Physics, Faculty of Science, Ege University, Bornova, Izmir (Turkey); Vujtek, Milan [Department of Experimental Physics, Faculty of Science, Palacky University, 17. listopadu 1192/12, 771 46 Olomouc (Czech Republic)

2016-08-21

The optimal detection of output signals from nuclear counting devices represents one of the key physical factors that govern accuracy and experimental reproducibility. In this context, the fine calibration of the detector under diverse experimental scenarios, although time costly, is necessary. However this process can be rendered easier with the use of systems that work in lieu of emulators. In this report we describe an innovative programmable pulse generator device capable to emulate the scintillation detector signals, in a way to mimic the detector performances under a variety of experimental conditions. The emulator generates a defined number of pulses, with a given shape and amplitude in the form of a sampled detector signal. The emulator output is then used off-line by a spectrometric system in order to set up its optimal performance. Three types of pulse shapes are produced by our device, with the possibility to add noise and pulse pile-up effects into the signal. The efficiency of the pulse detection, pile-up rejection and/or correction, together with the dead-time of the system, are therein analyzed through the use of some specific algorithms for pulse processing, and the results obtained validate the beneficial use of emulators for the accurate calibration process of spectrometric systems.

Performance of the intense pulsed neutron source accelerator system

International Nuclear Information System (INIS)

Potts, C.; Brumwell, F.; Rauchas, A.; Stipp, V.; Volk, G.

1983-01-01

The Intense Pulsed Neutron Source (IPNS) facility has now been operating in a routine way for outside users since November 1, 1981. From that date through December of 1982, the accelerator system was scheduled for neutron science for 4500 hours. During this time the accelerator achieved its short-term goals by delivering about 380,000,000 pulses of beam totaling over 6 x 10 20 protons. The changes in equipment and operating practices that evolved during this period of intense running are described. The intensity related instability threshold was increased by a factor of two and the accelerator beam current has been ion source limited. Plans to increase the accelerator intensity are also described. Initial operating results with a new H - ion source are discussed

Dynamic characterization and amplification of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers

DEFF Research Database (Denmark)

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

2013-01-01

We show a first-time demonstration of amplification of 400 fs pulses in a fiber optical parametric amplifier. The 400 fs signal is stretched in time, amplified by 26 dB and compressed back to 500 fs. A significant broadening of the pulses is experimentally shown due to dispersion and limited gain...

Kinematical vortices in double photoionization of helium by attosecond pulses

Science.gov (United States)

Djiokap, J. M. Ngoko; Meremianin, A. V.; Manakov, N. L.; Hu, S. X.; Madsen, L. B.; Starace, Anthony F.

2017-07-01

Two-armed helical vortex structures are predicted in the two-electron momentum distributions produced in double photoionization (DPI) of the He atom by a pair of time-delayed elliptically polarized attosecond pulses with opposite helicities. These predictions are based upon both a first-order perturbation theory analysis and numerical solutions of the two-electron, time-dependent Schrödinger equation in six spatial dimensions. The helical vortex structures originate from Ramsey interference of a pair of ionized two-electron wave packets, each having a total angular momentum of unity, and appear in the sixfold differential DPI probability distribution for any energy partitioning between the two electrons. The vortex structures are exquisitely sensitive to the time delay between the two pulses, their relative phase, their ellipticity, and their handedness; moreover, they occur in a variety of electron detection geometries. However, the vortex structures only occur when the angular separation β =cos-1(p̂1.p̂2) between the electron momenta p1 and p2 is held fixed. The vortex structures can also be observed in the fourfold differential DPI probability distribution obtained by averaging the sixfold differential probability over the emission angles of one electron. Such kinematical vortices are a general phenomenon that may occur in any ionization process, initiated by two time-delayed short pulses with opposite ellipticities, for particular detection geometries.

High-voltage isolation transformer for sub-nanosecond rise time pulses constructed with annular parallel-strip transmission lines.

Science.gov (United States)

Homma, Akira

2011-07-01

A novel annular parallel-strip transmission line was devised to construct high-voltage high-speed pulse isolation transformers. The transmission lines can easily realize stable high-voltage operation and good impedance matching between primary and secondary circuits. The time constant for the step response of the transformer was calculated by introducing a simple low-frequency equivalent circuit model. Results show that the relation between the time constant and low-cut-off frequency of the transformer conforms to the theory of the general first-order linear time-invariant system. Results also show that the test transformer composed of the new transmission lines can transmit about 600 ps rise time pulses across the dc potential difference of more than 150 kV with insertion loss of -2.5 dB. The measured effective time constant of 12 ns agreed exactly with the theoretically predicted value. For practical applications involving the delivery of synchronized trigger signals to a dc high-voltage electron gun station, the transformer described in this paper exhibited advantages over methods using fiber optic cables for the signal transfer system. This transformer has no jitter or breakdown problems that invariably occur in active circuit components.

Pulsed molecular beams: A lower limit on pulse duration for fully developed supersonic expansions

International Nuclear Information System (INIS)

Saenger, K.L.

1981-01-01

We derive an expression for Δt/sub min/, the mimimum pulse duration (''valve open time'') required if a pulsed nozzle is to produce a supersonic beam comparably ''cold'' to that obtained from a continuous source

Modeling pulse characteristics in Xenon with NEST

International Nuclear Information System (INIS)

Mock, J; Stolp, D; Szydagis, M; Tripathi, M; Uvarov, S; Woods, M; Walsh, N; Barry, N; Kazkaz, K

2014-01-01

A comprehensive model for describing the characteristics of pulsed signals, generated by particle interactions in xenon detectors, is presented. An emphasis is laid on two-phase time projection chambers, but the models presented are also applicable to single phase detectors. In order to simulate the pulse shape due to primary scintillation light, the effects of the ratio of singlet and triplet dimer state populations, as well as their corresponding decay times, and the recombination time are incorporated into the model. In a two phase time projection chamber, when simulating the pulse caused by electroluminescence light, the ionization electron mean free path in gas, the drift velocity, singlet and triplet decay times, diffusion constants, and the electron trapping time, have been implemented. This modeling has been incorporated into a complete software package, which realistically simulates the expected pulse shapes for these types of detectors

Robust motion artefact resistant circuit for calculation of Mean Arterial Pressure from pulse transit time.

Science.gov (United States)

Bhattacharya, Tinish; Gupta, Ankesh; Singh, Salam ThoiThoi; Roy, Sitikantha; Prasad, Anamika

2017-07-01

Cuff-less and non-invasive methods of Blood Pressure (BP) monitoring have faced a lot of challenges like stability, noise, motion artefact and requirement for calibration. These factors are the major reasons why such devices do not get approval from the medical community easily. One such method is calculating Blood Pressure indirectly from pulse transit time (PTT) obtained from electrocardiogram (ECG) and Photoplethysmogram (PPG). In this paper we have proposed two novel analog signal conditioning circuits for ECG and PPG that increase stability, remove motion artefacts, remove the sinusoidal wavering of the ECG baseline due to respiration and provide consistent digital pulses corresponding to blood pulses/heart-beat. We have combined these two systems to obtain the PTT and then correlated it with the Mean Arterial Pressure (MAP). The aim was to perform major part of the processing in analog domain to decrease processing load over microcontroller so as to reduce cost and make it simple and robust. We have found from our experiments that the proposed circuits can calculate the Heart Rate (HR) with a maximum error of ~3.0% and MAP with a maximum error of ~2.4% at rest and ~4.6% in motion.

A digital, constant-frequency pulsed phase-locked-loop instrument for real-time, absolute ultrasonic phase measurements

Science.gov (United States)

Haldren, H. A.; Perey, D. F.; Yost, W. T.; Cramer, K. E.; Gupta, M. C.

2018-05-01

A digitally controlled instrument for conducting single-frequency and swept-frequency ultrasonic phase measurements has been developed based on a constant-frequency pulsed phase-locked-loop (CFPPLL) design. This instrument uses a pair of direct digital synthesizers to generate an ultrasonically transceived tone-burst and an internal reference wave for phase comparison. Real-time, constant-frequency phase tracking in an interrogated specimen is possible with a resolution of 0.000 38 rad (0.022°), and swept-frequency phase measurements can be obtained. Using phase measurements, an absolute thickness in borosilicate glass is presented to show the instrument's efficacy, and these results are compared to conventional ultrasonic pulse-echo time-of-flight (ToF) measurements. The newly developed instrument predicted the thickness with a mean error of -0.04 μm and a standard deviation of error of 1.35 μm. Additionally, the CFPPLL instrument shows a lower measured phase error in the absence of changing temperature and couplant thickness than high-resolution cross-correlation ToF measurements at a similar signal-to-noise ratio. By showing higher accuracy and precision than conventional pulse-echo ToF measurements and lower phase errors than cross-correlation ToF measurements, the new digitally controlled CFPPLL instrument provides high-resolution absolute ultrasonic velocity or path-length measurements in solids or liquids, as well as tracking of material property changes with high sensitivity. The ability to obtain absolute phase measurements allows for many new applications than possible with previous ultrasonic pulsed phase-locked loop instruments. In addition to improved resolution, swept-frequency phase measurements add useful capability in measuring properties of layered structures, such as bonded joints, or materials which exhibit non-linear frequency-dependent behavior, such as dispersive media.

Pulsed TRIGA reactor as substitute for long pulse spallation neutron source

International Nuclear Information System (INIS)

Whittemore, W.L.

1999-01-01

TRIGA reactor cores have been used to demonstrate various pulsing applications. The TRIGA reactor fuel (U-ZrH x ) is very robust especially in pulsing applications. The features required to produce 50 pulses per second have been successfully demonstrated individually, including pulse tests with small diameter fuel rods. A partially optimized core has been evaluated for pulses at 50 Hz with peak pulsed power up to 100 MW and an average power up to 10 MW. Depending on the design, the full width at half power of the individual pulses can range between 2000 μsec to 3000 μsec. Until recently, the relatively long pulses (2000 μsec to 3000 μsec) from a pulsed thermal reactor or a long pulse spallation source (LPSS) have been considered unsuitable for time-of-flight measurements of neutron scattering. More recently considerable attention has been devoted to evaluating the performance of long pulse (1000 to 4000 μs) spallation sources for the same type of neutron measurements originally performed only with short pulses from spallation sources (SPSS). Adequate information is available to permit meaningful comparisons between CW, SPSS, and LPSS neutron sources. Except where extremely high resolution is required (fraction of a percent), which does require short pulses, it is demonstrated that the LPSS source with a 1000 msec or longer pulse length and a repetition rate of 50 to 60 Hz gives results comparable to those from the 60 MW ILL (CW) source. For many of these applications the shorter pulse is not necessarily a disadvantage, but it is not an advantage over the long pulse system. In one study, the conclusion is that a 5 MW 2000 μsec LPSS source improves the capability for structural biology studies of macromolecules by at least a factor of 5 over that achievable with a high flux reactor. Recent studies have identified the advantages and usefulness of long pulse neutron sources. It is evident that the multiple pulse TRIGA reactor can produce pulses comparable to

Pulse-width discriminators

International Nuclear Information System (INIS)

Budyashov, Yu.G.; Grebenyuk, V.M.; Zinov, V.G.

1978-01-01

A pulse duration discriminator is described which is intended for processing signals from multilayer scintillators. The basic elements of the scintillator are: an input gate, a current generator, an integrating capacitor, a Schmidt trigger and an anticoincidence circuit. The basic circuit of the discriminator and its time diagrams explaining its operating are given. The discriminator is based on microcircuits. Pulse duration discrimination threshold changes continuously from 20 to 100 ns, while its amplitude threshold changes within 20 to 100 mV. The temperature instability of discrimination thresholds (both in pulse width and in amplitude) is better than 0.1 per cent/deg C

Effect of laser pulse energies in laser induced breakdown spectroscopy in double-pulse configuration

International Nuclear Information System (INIS)

Benedetti, P.A.; Cristoforetti, G.; Legnaioli, S.; Palleschi, V.; Pardini, L.; Salvetti, A.; Tognoni, E.

2005-01-01

In this paper, the effect of laser pulse energy on double-pulse laser induced breakdown spectroscopy signal is studied. In particular, the energy of the first pulse has been changed, while the second pulse energy is held fixed. A systematic study of the laser induced breakdown spectroscopy signal dependence on the interpulse delay is performed, and the results are compared with the ones obtained with a single laser pulse of energy corresponding to the sum of the two pulses. At the same time, the crater formed at the target surface is studied by video-confocal microscopy, and the variation in crater dimensions is correlated to the enhancement of the laser induced breakdown spectroscopy signal. The results obtained are consistent with the interpretation of the double-pulse laser induced breakdown spectroscopy signal enhancement in terms of the changes in ambient gas pressure produced by the shock wave induced by the first laser pulse

Single machine total completion time minimization scheduling with a time-dependent learning effect and deteriorating jobs

Science.gov (United States)

Wang, Ji-Bo; Wang, Ming-Zheng; Ji, Ping

2012-05-01

In this article, we consider a single machine scheduling problem with a time-dependent learning effect and deteriorating jobs. By the effects of time-dependent learning and deterioration, we mean that the job processing time is defined by a function of its starting time and total normal processing time of jobs in front of it in the sequence. The objective is to determine an optimal schedule so as to minimize the total completion time. This problem remains open for the case of -1 < a < 0, where a denotes the learning index; we show that an optimal schedule of the problem is V-shaped with respect to job normal processing times. Three heuristic algorithms utilising the V-shaped property are proposed, and computational experiments show that the last heuristic algorithm performs effectively and efficiently in obtaining near-optimal solutions.

Modeling of Trichel pulses in negative corona

International Nuclear Information System (INIS)

Napartovich, A.P.; Akishev, Yu. S.; Deryugin, A.A.; Kochetov, I.V.; Pan'kin, M.V.; Trushkin, N.I.

1998-01-01

Results are reported of detailed numerical studies of Trichel pulse formation for dry air in short-gap coronas. Continuity equations for electrons, positive and negative ions, and the Poisson equation averaged over the current cross section were solved numerically with appropriate boundary conditions. The results of numerical simulation make it possible to analyze in detail the trailing edge of the Trichel pulse and the inter-pulse pause determining the period between pulses. In particular, the variations of the total number of negative ions in the corona spacing occurring under typical conditions of a pulsating corona, proved to be quite insignificant. A comparison with experiments demonstrated a reasonable agreement both for the shape of the pulse and for the average characteristics of the negative corona. (J.U.)

Whole blood coagulation time, haematocrit, haemoglobin and total ...

African Journals Online (AJOL)

The study was carried out to determine the values of whole blood coagulation time (WBCT), haematocrit (HM), haemaglobin (HB) and total protein (TP) of one hundred and eighteen apparently healthy turkeys reared under an extensive management system in Zaria. The mean values for WBCT, HM, HB and TP were 1.12 ...

Controlling the high frequency response of H{sub 2} by ultra-short tailored laser pulses: A time-dependent configuration interaction study

Energy Technology Data Exchange (ETDEWEB)

Schönborn, Jan Boyke; Saalfrank, Peter; Klamroth, Tillmann, E-mail: klamroth@uni-potsdam.de [Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam-Golm (Germany)

2016-01-28

We combine the stochastic pulse optimization (SPO) scheme with the time-dependent configuration interaction singles method in order to control the high frequency response of a simple molecular model system to a tailored femtosecond laser pulse. For this purpose, we use H{sub 2} treated in the fixed nuclei approximation. The SPO scheme, as similar genetic algorithms, is especially suited to control highly non-linear processes, which we consider here in the context of high harmonic generation. Here, we will demonstrate that SPO can be used to realize a “non-harmonic” response of H{sub 2} to a laser pulse. Specifically, we will show how adding low intensity side frequencies to the dominant carrier frequency of the laser pulse and stochastically optimizing their contribution can create a high-frequency spectral signal of significant intensity, not harmonic to the carrier frequency. At the same time, it is possible to suppress the harmonic signals in the same spectral region, although the carrier frequency is kept dominant during the optimization.

Time and space domain separation of pulsed X-ray beams diffracted from vibrating crystals

Energy Technology Data Exchange (ETDEWEB)

Nosik, V. L., E-mail: v-nosik@yandex.ru, E-mail: nosik@ns.crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,” (Russian Federation)

2016-11-15

It is known that a set of additional reflections (satellites) may arise on rocking curves in the case of X-ray diffraction in the Bragg geometry from crystals where high-frequency ultrasonic vibrations are excited. It is shown that, under certain conditions, the pulse wave fields of the satellites and main reflection may be intersected in space (playing the role of pump and probe beams) and in time (forming interference superlattices).

SIMULTANEOUS OBSERVATIONS OF GIANT PULSES FROM PULSAR PSR B0031-07 AT 38 AND 74 MHz

Energy Technology Data Exchange (ETDEWEB)

Tsai, Jr-Wei; Simonetti, John H.; Bear, Brandon [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Gough, Jonathan D. [Department of Chemistry, Lehman College, CUNY, Bronx, NY 10468 (United States); Newton, Joseph R. [Department of Chemistry and Physics, Augusta University, Augusta, GA 30912 (United States); Kavic, Michael [Department of Physics, Long Island University, Brooklyn, NY 11201 (United States)

2016-03-15

The first station of the Long Wavelength Array was used to study PSR B0031-07 with simultaneous observations at 38 and 74 MHz. We found that 158 (0.35%) of the observed pulses at 38 MHz and 221 (0.49%) of the observed pulses at 74 MHz qualified as giant pulses (GPs) in a total of 12 hr of observations. GPs are defined as having flux densities of a factor of ≥90 times that of an average pulse (AP) at 38 MHz and ≥80 times that of an AP at 74 MHz. The cumulative distribution of pulse strength follows a power law, with an index of −4.2 at 38 MHz and −4.9 at 74 MHz. This distribution has a much more gradual slope than would be expected if observing the tail of a Gaussian distribution of normal pulses. The dispersion measure (DM) value which resulted in the largest signal to noise for dedispersed pulses was DM = 10.9 pc cm{sup −3}. No other transient pulses were detected in the data in the wide DM range from 1 to 5000 pc cm{sup −3}. There were 12 GPs detected within the same period from both 38 and 74 MHz, meaning that the majority of them are not generated in a wide band.

Simulation and real-time analysis of pulse shapes from segmented HPGe-detectors

Energy Technology Data Exchange (ETDEWEB)

Schlarb, Michael Christian

2009-11-17

The capabilities of future HPGe arrays consisting of highly segmented detectors, like AGATA will depend heavily on the performance of {gamma}-ray tracking. The most crucial component in the whole concept is the pulse shape analysis (PSA). The working principle of PSA is to compare the experimental signal shape with signals available from a basis set with known interaction locations. The efficiency of the tracking algorithm hinges on the ability of the PSA to reconstruct the interaction locations accurately, especially for multiple {gamma}-interactions. Given the size of the arrays the PSA algorithm must be run in a real-time environment. A prerequisite to a successful PSA is an accurate knowledge of the detectors response. Making a full coincidence scan of a single AGATA detector, however takes between two and three months, which is too long to produce an experimental signal basis for all detector elements. A straight forward possibility is to use a precise simulation of the detector and to provide a basis of simulated signals. For this purpose the Java Agata Signal Simulation (JASS) was developed in the course of this thesis. The geometry of the detector is given with numerical precision and models describing the anisotropic mobilities of the charge carriers in germanium were taken from the literature. The pulse shapes of the transient and net-charge signals are calculated using weighting potentials on a finite grid. Special care was taken that the interpolation routine not only reproduces the weighting potentials precisely in the highly varying areas of the segment boundaries but also that its performance is independent of the location within the detector. Finally data from a coincidence scan and a pencil beam experiment were used to verify JASS. The experimental signals are reproduced accurately by the simulation. Pulse Shape Analysis (PSA) reconstructs the positions of the individual interactions and the corresponding energy deposits within the detector. This

Simulation and real-time analysis of pulse shapes from segmented HPGe-detectors

International Nuclear Information System (INIS)

Schlarb, Michael Christian

2009-01-01

The capabilities of future HPGe arrays consisting of highly segmented detectors, like AGATA will depend heavily on the performance of γ-ray tracking. The most crucial component in the whole concept is the pulse shape analysis (PSA). The working principle of PSA is to compare the experimental signal shape with signals available from a basis set with known interaction locations. The efficiency of the tracking algorithm hinges on the ability of the PSA to reconstruct the interaction locations accurately, especially for multiple γ-interactions. Given the size of the arrays the PSA algorithm must be run in a real-time environment. A prerequisite to a successful PSA is an accurate knowledge of the detectors response. Making a full coincidence scan of a single AGATA detector, however takes between two and three months, which is too long to produce an experimental signal basis for all detector elements. A straight forward possibility is to use a precise simulation of the detector and to provide a basis of simulated signals. For this purpose the Java Agata Signal Simulation (JASS) was developed in the course of this thesis. The geometry of the detector is given with numerical precision and models describing the anisotropic mobilities of the charge carriers in germanium were taken from the literature. The pulse shapes of the transient and net-charge signals are calculated using weighting potentials on a finite grid. Special care was taken that the interpolation routine not only reproduces the weighting potentials precisely in the highly varying areas of the segment boundaries but also that its performance is independent of the location within the detector. Finally data from a coincidence scan and a pencil beam experiment were used to verify JASS. The experimental signals are reproduced accurately by the simulation. Pulse Shape Analysis (PSA) reconstructs the positions of the individual interactions and the corresponding energy deposits within the detector. This is

Reduction of protease activity in milk by continuous flow high-intensity pulsed electric field treatments.

Science.gov (United States)

Bendicho, S; Barbosa-Cánovas, G V; Martín, O

2003-03-01

High-intensity pulsed electric field (HIPEF) is a non-thermal food processing technology that is currently being investigated to inactivate microorganisms and certain enzymes, involving a limited increase of food temperature. Promising results have been obtained on the inactivation of microbial enzymes in milk when suspended in simulated milk ultrafiltrate. The aim of this study was to evaluate the effectiveness of continuous HIPEF equipment on inactivating a protease from Bacillus subtilis inoculated in milk. Samples were subjected to HIPEF treatments of up to 866 micros of squared wave pulses at field strengths from 19.7 to 35.5 kV/cm, using a treatment chamber that consisted of eight colinear chambers connected in series. Moreover, the effects of different parameters such as pulse width (4 and 7 micros), pulse repetition rates (67, 89, and 111 Hz), and milk composition (skim and whole milk) were tested. Protease activity decreased with increased treatment time or field strength and pulse repetition rate. Regarding pulse width, no differences were observed between 4 and 7 micros pulses when total treatment time was considered. On the other hand, it was observed that milk composition affected the results since higher inactivation levels were reached in skim than in whole milk. The maximum inactivation (81%) was attained in skim milk after an 866-micros treatment at 35.5 kV/cm and 111 Hz.

Atomic and molecular dynamics triggered by ultrashort light pulses on the atto- to picosecond time scale

Science.gov (United States)

Pabst, Stefan

2013-04-01

Time-resolved investigations of ultrafast electronic and molecular dynamics were not possible until recently. The typical time scale of these processes is in the picosecond to attosecond realm. The tremendous technological progress in recent years made it possible to generate ultrashort pulses, which can be used to trigger, to watch, and to control atomic and molecular motion. This tutorial focuses on experimental and theoretical advances which are used to study the dynamics of electrons and molecules in the presence of ultrashort pulses. In the first part, the rotational dynamics of molecules, which happens on picosecond and femtosecond time scales, is reviewed. Well-aligned molecules are particularly suitable for angle-dependent investigations like x-ray diffraction or strong-field ionization experiments. In the second part, the ionization dynamics of atoms is studied. The characteristic time scale lies, here, in the attosecond to few-femtosecond regime. Although a one-particle picture has been successfully applied to many processes, many-body effects do constantly occur. After a broad overview of the main mechanisms and the most common tools in attosecond physics, examples of many-body dynamics in the attosecond world (e.g., in high-harmonic generation and attosecond transient absorption spectroscopy) are discussed.

Does antegrade JJ stenting affect the total operative time during laparoscopic pyeloplasty?

Science.gov (United States)

Bolat, Mustafa Suat; Çınar, Önder; Akdeniz, Ekrem

2017-12-01

We aimed to show the effect of retrograde JJ stenting and intraoperative antegrade JJ stenting techniques on operative time in patients who underwent laparoscopic pyeloplasty. A total of 34 patients were retrospectively investigated (15 male and 19 female) with ureteropelvic junction obstruction. Of the patients stentized under local anesthesia preoperatively, as a part of surgery, 15 were retrogradely stentized at the beginning of the procedure (Group 1), and 19 were antegradely stentized during the procedure (Group 2). A transperitoneal dismembered pyeloplasty technique was performed in all patients. The two groups were retrospectively compared in terms of complications, the mean total operative time, and the mean stenting times. The mean ages of the patients were 31.5±15.5 and 33.2±15.5 years (p=0.09), and the mean body mass indexes were 25.8±5.6 and 26.2.3±8.4 kg/m 2 in Group 1 and Group 2, respectively. The mean total operative times were 128.9±38.9 min and 112.7±21.9 min (p=0.04); the mean stenting times were 12.6±5.4 min and 3.5±2.4 min (p=0.02); and the mean rates of catheterization-to-total surgery times were 0.1 and 0.03 (p=0.01) in Group 1 and 2, respectively. The mean hospital stays and the mean anastomosis times were similar between the two groups (p>0.05). Antegrade JJ stenting during laparoscopic pyeloplasty significantly decreased the total operative time.

Proposal of a wide-band mirror polarizer of slow neutrons at a pulsed neutron source

International Nuclear Information System (INIS)

Nikitenko, Yu.V.; Ostanevich, Yu.M.

1992-01-01

The new type wide-band mirror-based neutron polarizer to be operated at a pulsed neutron source is suggested. The idea is to use a movable polarizing mirror system, which, be the incoming beam monochromatized by the time-of-flight, would allow one to tune glancing angles in time so, that the total reflection condition is always fulfilled only for one of the two neutron spin eigenstates. Estimates show, that with the pulsed reactor IBR-2 such polarizer allows one to build a small-angle neutron scattering instrument capable to effectively use the wave-length band from 2 to 15 A. 9 refs.; 1 fig

Direct time integration of Maxwell's equations in linear dispersive media with absorption for scattering and propagation of femtosecond electromagnetic pulses

Science.gov (United States)

Joseph, Rose M.; Hagness, Susan C.; Taflove, Allen

1991-01-01

The initial results for femtosecond pulse propagation and scattering interactions for a Lorentz medium obtained by a direct time integration of Maxwell's equations are reported. The computational approach provides reflection coefficients accurate to better than 6 parts in 10,000 over the frequency range of dc to 3 x 10 to the 16th Hz for a single 0.2-fs Gaussian pulse incident upon a Lorentz-medium half-space. New results for Sommerfeld and Brillouin precursors are shown and compared with previous analyses. The present approach is robust and permits 2D and 3D electromagnetic pulse propagation directly from the full-vector Maxwell's equations.

PNG-300 a nanosecond pulsed neutron generator

International Nuclear Information System (INIS)

Sztaricskai, T.; Vasvary, L.; Petoe, G.C.; Devkin, B.V.

1985-01-01

The design and operation of a nanosecond-pulse neutron generator is reported. It was constructed for the measurement of prompt neutron and gamma radiation in experimental studies of fast neutron reactions by time of flight techniques. The acceleration voltage is 300 kV and the total resolution of the generator-neutron spectrometer system is 2 ns. The ion-optical system, the vacuum system and the control of the neutron generator is described in detail. The equipment was used for prompt neutron and gamma radiation induced in construction materials. (R.P.)

Picosecond, single pulse electron linear accelerator

International Nuclear Information System (INIS)

Kikuchi, Riichi; Kawanishi, Masaharu

1979-01-01

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

Effects of laser wavelengths and pulse energy ratio on the emission enhancement in dual pulse LIBS

International Nuclear Information System (INIS)

Ahmed, Rizwan; Iqbal, Javed; Baig, M Aslam

2015-01-01

We present new studies on the effects of laser wavelengths, pulse energy ratio and interpulse delay between two laser pulses in the collinear dual pulse configuration of laser-induced breakdown spectroscopy (LIBS) on an iron sample in air using the fundamental (1064 nm) and the second harmonics (532 nm) of Nd:YAG lasers. In the dual pulse LIBS, an optimum value of interpulse delay with an appropriate combination of laser wavelengths, and laser pulse energy ratio, yields a 30 times signal intensity enhancement in the neutral iron lines as compared with single pulse LIBS. A comparison in the spatial variations of electron temperature along the axis of the plume expansion in single and double pulse LIBS has also been studied. (letter)

Time-resolved pulse propagation in a strongly scattering material

NARCIS (Netherlands)

Johnson, Patrick M.; Imhof, Arnout; Bret, B.P.J.; Gomez Rivas, J.; Gomez Rivas, Jaime; Lagendijk, Aart

2003-01-01

Light transport in macroporous gallium phosphide, perhaps the strongest nonabsorbing scatterer of visible light, is studied using phase-sensitive femtosecond pulse interferometry. Phase statistics are measured at optical wavelengths in both reflection and transmission and compared with theory. The

Space and time dependent properties of the virtual cathode in a reflex-type pulsed ion diode

International Nuclear Information System (INIS)

Matsumoto, Yoshio; Kitamura, Akira; Yano, Syukuro

1981-01-01

Properties of a virtual cathode in a pulsed ion diode composed of and insulator-mesh anode and a metal-mesh cathode were studied experimentally at anode voltages below 35o kV. Potential distribution in the virtual cathode side was measured with an insulated electrostatic potential probe, and ion beam currents in virtual and real cathode sides were measured with biased ion collectors. Experimental results are given for the space and time behaviors of the anode plasma and the virtual cathode which starts to grow first from a region near a periphery of the metal anode frame and extends over the central region near the anode surface. A loss parameter for the electron current accompanied with the ion beam at the virtual cathode was evaluated from the measured electron current values by using relations derived from the one-dimensional Child-Langmuir theory applied to the reflex triode. The ion beam accompanies a considerable amount of electron current, and this influences the stability of the virtual cathode; this perturbation results in variations of ion current with time. Experimental results for space potentials in the emitted ion beam and the total current flowing in the space of the virtual cathode side are also given, suggesting an existence of high energy electrons of several keV accelerated by positive space potential of the ion beam. (author)

Characterisation of historic plastics using terahertz time-domain spectroscopy and pulsed imaging.

Science.gov (United States)

Pastorelli, Gianluca; Trafela, Tanja; Taday, Phillip F; Portieri, Alessia; Lowe, David; Fukunaga, Kaori; Strlič, Matija

2012-05-01

Terahertz (THz) time-domain spectroscopy and 3D THz pulsed imaging have been explored with regard to polymer materials, both commodity and historic polymers. A systematic spectroscopic study of a wide range of different polymer materials showed significant differences in their spectra. Polyolefins and polystyrenes generally exhibit lower absorption than other examined polymers, various cellulose derivates, poly(vinyl chloride), poly(methyl methacrylate), polyamide, hard rubber and phenol formaldehyde resin, the last of these exhibiting the most intense absorption over the entire range, 0.15-4.2 THz. It was also examined how the presence of plasticisers in poly(vinyl chloride), the presence of fillers in polypropylene, and the degree of branching in polyethylene and polystyrene affect the spectra; inorganic fillers in polypropylene affected the absorption most. With 3D THz pulsed imaging, features in polymer objects were explored, appearing either as integral parts of the material (coatings and pores in foams) or as a consequence of physical deterioration (cracks, delamination). All of these features of various complexities can be successfully imaged in 3D. Terahertz technology is thus shown to have significant potential for both chemical and structural characterisation of polymers, which will be of interest to heritage science, but also to the polymer industry and development of analytical technologies in general.

Changes in the bilateral pulse transit time difference with a moving arm.

Science.gov (United States)

Jiang, Xinge; Wei, Shoushui; Zheng, Dingchang; Huang, Peng; Liu, Chengyu

2018-04-20

Changes of pulse transit time (PTT) induced by arm position were studied for unilateral arm. However, consistency of the PTT changes was not validated for both arm sides. We aimed to quantify the PTT changes between horizontal and non-horizontal positions from right arm and left arm in order to explore the consistency of both arms. Twenty-four normal subjects aged between 21 and 50 (14 male and 10 female) years were enrolled. Left and right radial artery pulses were synchronously recorded from 24 healthy subjects with one arm (left or right) at five angles (90∘, 45∘, 0∘, -45∘ and -90∘) and the other arm at the horizontal level (0∘) for reference. The overall mean PTT changes at the five angles (from 90∘ to -90∘) in the left arm (right as reference) were 16.1, 12.3, -0.5, -2.5 and -2.6 ms, respectively, and in the right arm (left as reference) were 18.0, 12.6, 1.6, -1.6 and -2.0 ms, respectively. Obvious differences were not found in the PTT changes between the two arms (left arm moving or right arm moving) under each of the five different positions (all P> 0.05).

Breakup of the H2 molecule by xuv laser pulses: A time-dependent treatment in prolate spheroidal coordinates

International Nuclear Information System (INIS)

Guan Xiaoxu; Bartschat, Klaus; Schneider, Barry I

2012-01-01

We present theoretical predictions for one-photon double-ionization of H 2 by an xuv laser pulse. The results were obtained by solving the time-dependent Schrödinger equation in prolate spheroidal coordinates. Good agreement is obtained with predictions from other time-dependent and time-independent calculations, except for the recent 'exterior complex scaling' treatment by Tao et al. (Phys. Rev. A 82 023423).

Proposal of a wide-band mirror polarizer of slow neutrons at a pulsed neutron source

International Nuclear Information System (INIS)

Nikitenko, Yu.V.; Ostanevich, Yu.M.

1993-01-01

The new type of wide-band mirror-based neutron polarizer, which is to be operated at a pulsed neutron source, is suggested. The idea is to use a movable polarizing mirror system, which, with the incoming beam monochromatized by the time-of-flight, would allow one to tune glancing angles in time so that the total reflection condition is always fulfilled only for one of the two neutron spin eigenstates. Estimates show that with the pulsed reactor IBR-2 such a polarizer allows one to build a small angle neutron scattering instrument capable of effectively using the wavelength band from 2 A with a rather high luminosity (time-averaged flux at sample position being up to 10 7 n/s/cm -2 ). (orig.)

Current pulse shaping of the load current on PTS

Directory of Open Access Journals (Sweden)

Minghe Xia

2016-02-01

Full Text Available The typical rise time of PTS machine is ∼110 ns with about 10 MA peak current under short pulse mode when all 24 modules discharge simultaneously. By distributing the trigger times of 12 laser beams logically and adjusting the statues of the pulse output switches, longer rise-time pulse can be obtained on the PTS facility. Based on the required pulse shape, whole circuit simulations will be used to calculate the trigger times of each laser triggering gas switch and the status of the pulse output switches. The rise time of the current is determined by the time difference between the first and last trigged laser triggering gas switches. In order to trigger the laser triggering gas switch, sufficient laser power is needed to be sent into the gap of the gas switches. The gas pressure and voltage difference on the two electrodes of the gas switches also affect the triggering of the gas switches, and the voltage added on the gas switch is determined by its transition time. Traditionally the trigger time difference should be less than the transition time of the two neighboring modules. A new simulation model of PTS shows one can break this transition time limits. Series of current pulse shaping experiments have been investigated on the PTS (Primary Test Stand. As results, more than 5 MA peak current were successfully achieved on the load with a rise time of 600 ns. This study and experiments of the pulse shaping on PTS demonstrate the adaptable ability of the PTS for offering different waveform of mega ampere current pulse for different research purpose.

Objectively Measured Total and Occupational Sedentary Time in Three Work Settings

Science.gov (United States)

van Dommelen, Paula; Coffeng, Jennifer K.; van der Ploeg, Hidde P.; van der Beek, Allard J.; Boot, Cécile R. L.; Hendriksen, Ingrid J. M.

2016-01-01

Background Sedentary behaviour increases the risk for morbidity. Our primary aim is to determine the proportion and factors associated with objectively measured total and occupational sedentary time in three work settings. Secondary aim is to study the proportion of physical activity and prolonged sedentary bouts. Methods Data were obtained using ActiGraph accelerometers from employees of: 1) a financial service provider (n = 49 men, 31 women), 2) two research institutes (n = 30 men, 57 women), and 3) a construction company (n = 38 men). Total (over the whole day) and occupational sedentary time, physical activity and prolonged sedentary bouts (lasting ≥30 minutes) were calculated by work setting. Linear regression analyses were performed to examine general, health and work-related factors associated with sedentary time. Results The employees of the financial service provider and the research institutes spent 76–80% of their occupational time in sedentary behaviour, 18–20% in light intensity physical activity and 3–5% in moderate-to-vigorous intensity physical activity. Occupational time in prolonged sedentary bouts was 27–30%. Total time was less sedentary (64–70%), and had more light intensity physical activity (26–33%). The employees of the construction company spent 44% of their occupational time in sedentary behaviour, 49% in light, and 7% in moderate intensity physical activity, and spent 7% in sedentary bouts. Total time spent in sedentary behavior was 56%, 40% in light, and 4% in moderate intensity physical behaviour, and 12% in sedentary bouts. For women, low to intermediate education was the only factor that was negatively associated with occupational sedentary time. Conclusions Sedentary behaviour is high among white-collar employees, especially in highly educated women. A relatively small proportion of sedentary time was accrued in sedentary bouts. It is recommended that worksite health promotion efforts should focus on reducing sedentary

Interaction between two stopped light pulses

Energy Technology Data Exchange (ETDEWEB)

Chen, Yi-Hsin, E-mail: yhchen920@gmail.com; Lee, Meng-Jung, E-mail: yhchen920@gmail.com; Hung, Weilun, E-mail: yhchen920@gmail.com; Yu, Ite A., E-mail: yu@phys.nthu.edu.tw [Department of Physics and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chen, Ying-Cheng [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan and Department of Physics and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Chen, Yong-Fan [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China)

2014-03-05

The efficiency of a nonlinear optical process is proportional to the interaction time. We report a scheme of all-optical switching based on two motionless light pulses via the effect of electromagnetically induced transparency. One pulse was stopped as the stationary light pulse (SLP) and the other was stopped as stored light. The time of their interaction via the medium can be prolonged and, hence, the optical nonlinearity is greatly enhanced. Using a large optical density (OD) of 190, we achieved a very long interaction time of 6.9 μs. This can be analogous to the scheme of trapping light pulses by an optical cavity with a Q factor of 8×10{sup 9}. With the approach of using moving light pulses in the best situation, a switch can only be activated at 2 photons per atomic absorption cross section. With the approach of employing a SLP and a stored light pulse, a switch at only 0.56 photons was achieved and the efficiency is significantly improved. Moreover, the simulation results are in good agreement with the experimental data and show that the efficiency can be further improved by increasing the OD of the medium. Our work advances the technology in quantum information manipulation utilizing photons.

Interaction between two stopped light pulses

International Nuclear Information System (INIS)

Chen, Yi-Hsin; Lee, Meng-Jung; Hung, Weilun; Yu, Ite A.; Chen, Ying-Cheng; Chen, Yong-Fan

2014-01-01

The efficiency of a nonlinear optical process is proportional to the interaction time. We report a scheme of all-optical switching based on two motionless light pulses via the effect of electromagnetically induced transparency. One pulse was stopped as the stationary light pulse (SLP) and the other was stopped as stored light. The time of their interaction via the medium can be prolonged and, hence, the optical nonlinearity is greatly enhanced. Using a large optical density (OD) of 190, we achieved a very long interaction time of 6.9 μs. This can be analogous to the scheme of trapping light pulses by an optical cavity with a Q factor of 8×10 9 . With the approach of using moving light pulses in the best situation, a switch can only be activated at 2 photons per atomic absorption cross section. With the approach of employing a SLP and a stored light pulse, a switch at only 0.56 photons was achieved and the efficiency is significantly improved. Moreover, the simulation results are in good agreement with the experimental data and show that the efficiency can be further improved by increasing the OD of the medium. Our work advances the technology in quantum information manipulation utilizing photons

Theoretical and Experimental Investigations of Coincidences in Poisson Distributed Pulse Trains and Spectral Distortion Caused by Pulse Pileup.

Science.gov (United States)

Bristow, Quentin

1990-01-01

Part one of this two-part study is concerned with the multiple coincidences in pulse trains from X-ray and gamma radiation detectors which are the cause of pulse pileup. A sequence of pulses with inter-arrival times less than tau, the resolving time of the pulse-height analysis system used to acquire spectra, is called a multiple pulse string. Such strings can be classified on the basis of the number of pulses they contain, or the number of resolving times they cover. The occurrence rates of such strings are derived from theoretical considerations. Logic circuits were devised to make experimental measurements of multiple pulse string occurrence rates in the output from a NaI(Tl) scintillation detector over a wide range of count rates. Markov process theory was used to predict state transition rates in the logic circuits, enabling the experimental data to be checked rigorously for conformity with those predicted for a Poisson distribution. No fundamental discrepancies were observed. Part two of the study is concerned with a theoretical analysis of pulse pileup and the development of a discrete correction algorithm, based on the use of a function to simulate the coincidence spectrum produced by partial sums of pulses. Monte Carlo simulations, incorporating criteria for pulse pileup inherent in the operation of modern ADC's, were used to generate pileup spectra due to coincidences between two pulses, (1st order pileup) and three pulses (2nd order pileup), for different semi-Gaussian pulse shapes. Coincidences between pulses in a single channel produced a basic probability density function spectrum which can be regarded as an impulse response for a particular pulse shape. The use of a flat spectrum (identical count rates in all channels) in the simulations, and in a parallel theoretical analysis, showed the 1st order pileup distorted the spectrum to a linear ramp with a pileup tail. The correction algorithm was successfully applied to correct entire spectra for 1st and

High current transistor pulse generator

International Nuclear Information System (INIS)

Nesterov, V.; Cassel, R.

1991-05-01

A solid state pulse generator capable of delivering high current trapezoidally shaped pulses into an inductive load has been developed at SLAC. Energy stored in the capacitor bank of the pulse generator is switched to the load through a pair of Darlington transistors. A combination of diodes and Darlington transistors is used to obtain trapezoidal or triangular shaped current pulses into an inductive load and to recover the remaining energy in the same capacitor bank without reversing capacitor voltage. The transistors work in the switch mode, and the power losses are low. The rack mounted pulse generators presently used at SLAC contain a 660 microfarad storage capacitor bank and can deliver 400 amps at 800 volts into inductive loads up to 3 mH. The pulse generators are used in several different power systems, including pulse to pulse bipolar power supplies and in application with current pulses distributed into different inductive loads. The current amplitude and discharge time are controlled by the central computer system through a specially developed multichannel controller. Several years of operation with the pulse generators have proven their consistent performance and reliability. 8 figs

Total Work, Gender and Social Norms in EU and US Time Use

OpenAIRE

Burda , Michael C; Hamermesh , Daniel S; Weil , Philippe

2008-01-01

Using time-diary data from 27 countries, we demonstrate a negative relationship between real GDP per capita and the female-male difference in total work time--the sum of work for pay and work at home. We also show that in rich non-Catholic countries on four continents men and women do the same amount of total work on average. Our survey results demonstrate that labor economists, macroeconomists, sociologists and the general public consistently believe that women perform more total work. The f...

Effects of pulse ON and OFF time and electrode types on the material removal rate and tool wear rate of the Ti-6Al-4V Alloy using EDM machining with reverse polarity

Science.gov (United States)

Praveen, L.; Geeta Krishna, P.; Venugopal, L.; Prasad, N. E. C.

2018-03-01

Electrical Discharge Machining (EDM) is an unconventional metal removal process that is extensively used for removing the difficult-to-machine metal such as Ti alloys, super alloys and metal matrix composites. This paper investigates the effects of pulse (ON/OFF) time on EDM machining characteristics of Ti-6Al-4V alloy using copper and graphite as electrodes in reverse polarity condition. Full factorial design method was used to design the experiments. Two variables (Pulse On and OFF) with three levels are considered. The output variables are the tool wear rate and the material removal rate. The important findings from the present work are: (1) the material removal rate (MRR) increases gradually with an increase of the Pulse ON time whereas the change is insignificant with an increase of the Pulse OFF time, (2) Between copper and graphite electrodes, the copper electrode is proved to be good in terms of MRR, (3) a combination of high pulse ON time and OFF time is desirable for high MRR rate in the Cu electrode whereas for the graphite electrode, a combination of high pulse ON time and low pulse OFF time is desirable for high MRR rate, (4) the tool wear rate (TWR) reduces with the Pulse On or OFF time, the rate of TWR is uniform for the graphite electrode in contrast to abrupt decrease from 25 to 50 μs (pulse ON time) in the copper electrode, (5) In order to keep the TWR as minimum possible, it is desirable to have a combination of high pulse ON time and OFF time for both the copper and the graphite electrode.

Applications of Space-Time Duality

Science.gov (United States)

Plansinis, Brent W.

The concept of space-time duality is based on a mathematical analogy between paraxial diffraction and narrowband dispersion, and has led to the development of temporal imaging systems. The first part of this thesis focuses on the development of a temporal imaging system for the Laboratory for Laser Energetics. Using an electro-optic phase modulator as a time lens, a time-to-frequency converter is constructed capable of imaging pulses between 3 and 12 ps. Numerical simulations show how this system can be improved to image the 1-30 ps range used in OMEGA-EP. By adjusting the timing between the pulse and the sinusoidal clock of the phase modulator, the pulse spectrum can be selectively narrowed, broadened, or shifted. An experimental demonstration of this effect achieved spectral narrowing and broadening by a factor of 2. Numerical simulations show narrowing by a factor of 8 is possible with modern phase modulators. The second part of this thesis explores the space-time analog of reflection and refraction from a moving refractive index boundary. From a physics perspective, a temporal boundary breaks translational symmetry in time, requiring the momentum of the photon to remain unchanged while its energy may change. This leads to a shifting and splitting of the pulse spectrum as the boundary is crossed. Equations for the reflected and transmitted frequencies and a condition for total internal reflection are found. Two of these boundaries form a temporal waveguide, which confines the pulse to a narrow temporal window. These waveguides have a finite number of modes, which do not change during propagation. A single-mode waveguide can be created, allowing only a single pulse shape to form within the waveguide. Temporal reflection and refraction produce a frequency dependent phase shift on the incident pulse, leading to interference fringes between the incident light and the reflected light. In a waveguide, this leads to self-imaging, where the pulse shape reforms

Real-time spot size camera for pulsed high-energy radiographic machines

International Nuclear Information System (INIS)

Watson, S.A.

1993-01-01

The focal spot size of an x-ray source is a critical parameter which degrades resolution in a flash radiograph. For best results, a small round focal spot is required. Therefore, a fast and accurate measurement of the spot size is highly desirable to facilitate machine tuning. This paper describes two systems developed for Los Alamos National Laboratory's Pulsed High-Energy Radiographic Machine Emitting X-rays (PHERMEX) facility. The first uses a CCD camera combined with high-brightness floors, while the second utilizes phosphor storage screens. Other techniques typically record only the line spread function on radiographic film, while systems in this paper measure the more general two-dimensional point-spread function and associated modulation transfer function in real time for shot-to-shot comparison

Investigation of the effect of finite pulse errors on the BABA pulse sequence using the Floquet-Magnus expansion approach

Science.gov (United States)

Mananga, Eugene S.; Reid, Alicia E.

2013-01-01

This paper presents a study of finite pulse widths for the BABA pulse sequence using the Floquet-Magnus expansion (FME) approach. In the FME scheme, the first order ? is identical to its counterparts in average Hamiltonian theory (AHT) and Floquet theory (FT). However, the timing part in the FME approach is introduced via the ? function not present in other schemes. This function provides an easy way for evaluating the spin evolution during the time in between' through the Magnus expansion of the operator connected to the timing part of the evolution. The evaluation of ? is particularly useful for the analysis of the non-stroboscopic evolution. Here, the importance of the boundary conditions, which provide a natural choice of ? , is ignored. This work uses the ? function to compare the efficiency of the BABA pulse sequence with ? and the BABA pulse sequence with finite pulses. Calculations of ? and ? are presented.

Optimal timing of pulse onset for language mapping with navigated repetitive transcranial magnetic stimulation.

Science.gov (United States)

Krieg, Sandro M; Tarapore, Phiroz E; Picht, Thomas; Tanigawa, Noriko; Houde, John; Sollmann, Nico; Meyer, Bernhard; Vajkoczy, Peter; Berger, Mitchel S; Ringel, Florian; Nagarajan, Srikantan

2014-10-15

Within the primary motor cortex, navigated transcranial magnetic stimulation (nTMS) has been shown to yield maps strongly correlated with those generated by direct cortical stimulation (DCS). However, the stimulation parameters for repetitive nTMS (rTMS)-based language mapping are still being refined. For this purpose, the present study compares two rTMS protocols, which differ in the timing of pulse train onset relative to picture presentation onset during object naming. Results were the correlated with DCS language mapping during awake surgery. Thirty-two patients with left-sided perisylvian tumors were examined by rTMS prior to awake surgery. Twenty patients underwent rTMS pulse trains starting at 300 ms after picture presentation onset (delayed TMS), whereas another 12 patients received rTMS pulse trains starting at the picture presentation onset (ONSET TMS). These rTMS results were then evaluated for correlation with intraoperative DCS results as gold standard in terms of differential consistencies in receiver operating characteristics (ROC) statistics. Logistic regression analysis by protocols and brain regions were conducted. Within and around Broca's area, there was no difference in sensitivity (onset TMS: 100%, delayed TMS: 100%), negative predictive value (NPV) (onset TMS: 100%, delayed TMS: 100%), and positive predictive value (PPV) (onset TMS: 55%, delayed TMS: 54%) between the two protocols compared to DCS. However, specificity differed significantly (onset TMS: 67%, delayed TMS: 28%). In contrast, for posterior language regions, such as supramarginal gyrus, angular gyrus, and posterior superior temporal gyrus, early pulse train onset stimulation showed greater specificity (onset TMS: 92%, delayed TMS: 20%), NPV (onset TMS: 92%, delayed TMS: 57%) and PPV (onset TMS: 75%, delayed TMS: 30%) with comparable sensitivity (onset TMS: 75%, delayed TMS: 70%). Logistic regression analysis also confirmed the greater fit of the predictions by rTMS that had the

Nonlinear behaviors in a pulsed dielectric barrier discharge at atmospheric pressure

Energy Technology Data Exchange (ETDEWEB)

Zhang Jiao; Wang Yanhui, E-mail: wangyh@dlut.edu.cn; Wang Dezhen

2011-08-01

In this paper, the temporal nonlinear behaviors of pulsed dielectric barrier discharge in atmospheric helium are studied numerically by a one-dimensional fluid model. The results show that the common single-period pulsed discharge with two current pulses per single voltage pulse can take place over a broad parameter range. The rising and falling times of the voltage pulse can affect the discharge characteristics greatly. When the discharge is ignited by a pulse voltage with long rising and falling times, a single-period pulsed discharge with multiple current peaks can be observed. Under appropriate rising and falling times of the voltage pulse, a stable period-two discharge can occur over wide frequency and voltage ranges. Also this period-two discharge can exhibit different current and voltage characteristics with changing the duty cycle. With other parameters fixed, the pulsed DBD could be driven to chaos through period-doubling route by increasing either the falling time or the frequency of voltage pulse.

PROCESS INNOVATION: HOLISTIC SCENARIOS TO REDUCE TOTAL LEAD TIME

Directory of Open Access Journals (Sweden)

Alin POSTEUCĂ

2015-11-01

Full Text Available The globalization of markets requires continuous development of business holistic scenarios to ensure acceptable flexibility to satisfy customers. Continuous improvement of supply chain supposes continuous improvement of materials and products lead time and flow, material stocks and finished products stocks and increasing the number of suppliers close by as possible. The contribution of our study is to present holistic scenarios of total lead time improvement and innovation by implementing supply chain policy.

Digitizing data acquisition and time-of-flight pulse processing for ToF-ERDA

Energy Technology Data Exchange (ETDEWEB)

Julin, Jaakko, E-mail: jaakko.julin@jyu.fi; Sajavaara, Timo

2016-01-01

A versatile system to capture and analyze signals from multi channel plate (MCP) based time-of-flight detectors and ionization based energy detectors such as silicon diodes and gas ionization chambers (GIC) is introduced. The system is based on commercial digitizers and custom software. It forms a part of a ToF-ERDA spectrometer, which has to be able to detect recoil atoms of many different species and energies. Compared to the currently used analogue electronics the digitizing system provides comparable time-of-flight resolution and improved hydrogen detection efficiency, while allowing the operation of the spectrometer be studied and optimized after the measurement. The hardware, data acquisition software and digital pulse processing algorithms to suit this application are described in detail.

Observation of bulk-ion heating in a tokamak plasma by application of positive and negative current pulses in TRIAM-1

Energy Technology Data Exchange (ETDEWEB)

Toi, K; Hiraki, N; Nakamura, K; Mitarai, O; Kawai, Y; Itoh, S [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

1980-09-01

A positive of negative current pulse induced by a pulsed toroidal electric field much higher than the Dreicer field increases the bulk-ion temperature of the plasma centre two to three times, without macroscopic plasma destruction. The decay time of the raised ion temperature agrees well with the prediction from neoclassical transport theory. The magnitude of the positive current pulse is limited by violent current disruption, and that of the negative current by a lack of MHD equilibrium which is due to a marked reduction of the total plasma current. The relevant current-driven instabilities in the turbulent heating of a tokamak plasma, skin heating and inward transfer of the energy deposition in the skin layer are briefly discussed.

Time-of-flight pulsed neutron diffraction of molten salts

Energy Technology Data Exchange (ETDEWEB)

Fukushima, Y; Misawa, M; Suzuki, K [Tohoku Univ., Sendai (Japan). Research Inst. for Iron, Steel and Other Metals

1975-06-01

In this work, the pulsed neutron diffraction of molten alkali metal nitrate and bismuth trihalide was measured by the time-of-flight method. An electron linear accelerator was used as the pulsed neutron source. All the measurements were carried out with the T-O-F neutron diffractometer installed on the 300 MeV electron lineac. Molten NaNO/sub 3/ and RbNO/sub 3/ were adopted as the samples for alkali metal nitrate. The measurement is in progress for KNO/sub 3/ and LiNO/sub 3/. As the first step of the study on bismuth-bismuth trihalide system, the temperature dependence of structure factors was observed for BiCl/sub 3/, BiBr/sub 3/ and BiI/sub 3/ in the liquid state. The structure factors Sm(Q) for molten NaNO/sub 3/ at 340/sup 0/C and RbNO/sub 3/ at 350/sup 0/C were obtained, and the form factor F/sub 1/(Q) for single NO/sub 3//sup -/ radical with equilateral triangle structure was calculated. In case of molten NaNO/sub 3/, the first peak of Sm(Q) is simply smooth and a small hump can be observed in the neighbourhood of the first minimum Q position. The first peak of Sm(Q) for molten RbNO/sub 3/ is divided into two peaks, whereas a hump at the first minimum becomes big, and shifts to the low Q side of the second peak. The size of the NO/sub 3//sup -/ radical in molten NaNO/sub 3/ is a little smaller than that in molten RbNO/sub 3/. The values of the bond length in the NO/sub 3//sup -/ radical are summarized for crystal state and liquid state. The temperature dependence of the structure factor S(Q) was observed for BiCl/sub 3/, BiBr/sub 3/ and BiI/sub 3/, and shown in a figure.

Elemental redistribution in coloured films on SUS304 stainless steel produced by current pulse method

International Nuclear Information System (INIS)

Lin, C.J.; Duh, J.G.

1996-01-01

Coloured films are deposited on an SUS304 substrate by the square wave current pulse method in a 2.5 M CrO 3 + 5 M H 2 SO 4 solution at 75 C. The absolute ratio of anodic to cathodic charge density and the corresponding final value of cathodic potential provide an easy and appropriate approach to the control of colour in the current pulse colouring method. This is proved in this study for a frequency region lower than 1 Hz. The corresponding cathodic potential increases with increasing dwell time in the negative applied current region and is related to the colour tone of the deposited film. The total time required to obtain the same thickness of coloured film is shorter at lower frequency than at higher frequency, which takes more time to charge the double layer. The thickness of the coloured films is determined by both Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS) depth profiling and is of submicron order. The film thickness is proportional to the introduced total charge per unit area in the current pulse colouring process. CrO + and FeO + ions are observed in the coloured films and their concentrations increase as the colouring time is increased. The Fe concentration in the coloured films is lower than that in the substrate and decreases with the colouring time. It is the iron species that first becomes involved in the anodic reaction and the spinel oxide structure of iron and chromium is present in the coloured films. (orig.)

Porcine skin damage thresholds for pulsed nanosecond-scale laser exposure at 1064-nm

Science.gov (United States)

DeLisi, Michael P.; Peterson, Amanda M.; Noojin, Gary D.; Shingledecker, Aurora D.; Tijerina, Amanda J.; Boretsky, Adam R.; Schmidt, Morgan S.; Kumru, Semih S.; Thomas, Robert J.

2018-02-01

Pulsed high-energy lasers operating in the near-infrared (NIR) band are increasingly being used in medical, industrial, and military applications, but there are little available experimental data to characterize their hazardous effects on skin tissue. The current American National Standard for the Safe Use of Lasers (ANSI Z136.1-2014) defines the maximum permissible exposure (MPE) on the skin as either a single-pulse or total exposure time limit. This study determined the minimum visible lesion (MVL) damage thresholds in Yucatan miniature pig skin for the single-pulse case and several multiple-pulse cases over a wide range of pulse repetition frequencies (PRFs) (10, 125, 2,000, and 10,000 Hz) utilizing nanosecond-scale pulses (10 or 60 ns). The thresholds are expressed in terms of the median effective dose (ED50) based on varying individual pulse energy with other laser parameters held constant. The results confirm a decrease in MVL threshold as PRF increases for exposures with a constant number of pulses, while also noting a PRF-dependent change in the threshold as a function of the number of pulses. Furthermore, this study highlights a change in damage mechanism to the skin from melanin-mediated photomechanical events at high irradiance levels and few numbers of pulses to bulk tissue photothermal additivity at lower irradiance levels and greater numbers of pulses. The observed trends exceeded the existing exposure limits by an average factor of 9.1 in the photothermally-damaged cases and 3.6 in the photomechanicallydamaged cases.

Effectiveness of Pulse Oximetry Versus Doppler for Tourniquet Monitoring.

Science.gov (United States)

Wall, Piper L; Buising, Charisse M; Grulke, Lisa; Troester, Alexander; Bianchina, Nicholas; White, Shannon; Freymark, Rosemarie; Hassan, Ali; Hopkins, James W; Renner, Catherine Hackett; Sahr, Sheryl M

Pulse oximeters are common and include arterial pulse detection as part of their methodology. The authors investigated the possible usefulness of pulse oximeters for monitoring extremity tourniquet arterial occlusion. Tactical Ratcheting Medical Tourniquets were tightened to the least Doppler-determined occluding pressure at mid-thigh or mid-arm locations on one limb at a time on all four limbs of 15 volunteers. A randomized block design was used to determine the placement locations of three pulse oximeter sensors on the relevant digits. The times and pressures of pulsatile signal absences and returns were recorded for 200 seconds, with the tourniquet being tightened only when the Doppler ultrasound and all three pulse oximeters had pulsatile signals present (pulsatile waveform traces for the pulse oximeters). From the first Doppler signal absence to tourniquet release, toe-located pulse oximeters missed Doppler signal presence 41% to 50% of the times (discrete 1-second intervals) and missed 39% to 49% of the pressure points (discrete 1mmHg intervals); fingerlocated pulse oximeters had miss rates of 11% to 15% of the times and 13% to 19% of the pressure points. On toes, the pulse oximeter ranges of sensitivity and specificity for Doppler pulse detection were 71% to 90% and 44% to 51%, and on fingers, the respective ranges were 65% to 77% and 78% to 83%. Use of a pulse oximeter to monitor limb tourniquet effectiveness will result in some instances of an undetected weak arterial pulse being present. If a pulse oximeter waveform is obtained from a location distal to a tourniquet, the tourniquet should be tightened. If a pulsatile waveform is not detected, vigilance should be maintained. 2017.

Observation of enhanced field-free molecular alignment by two laser pulses

DEFF Research Database (Denmark)

Bisgaard, Christer; Poulsen, Mikael Dahlerup; Peronne, Emmanuel

2004-01-01

We show experimentally that field-free alignment of iodobenzene molecules, induced by a single, intense, linearly polarized 1.4-ps-long laser pulse, can be strongly enhanced by dividing the pulse into two optimally synchronized pulses of the same duration. For a given total energy of the two...

Few-cycle isolated attosecond pulses

International Nuclear Information System (INIS)

Sansone, G.; Benedetti, E.; Calegari, F.; Stagira, S.; Vozzi, C.; Silvestri De, S.; Nisoli, M.

2006-01-01

Complete test of publication follows. In the last few years the field of attosecond science has shown impressive and rapid progress, mainly due to the introduction of novel experimental methods for the characterization of extreme ultraviolet (XUV) pulses and attosecond electron wave packets. This development has been also triggered by significant improvements in the control of the electric field of the driving infrared pulses. Particularly interesting for the applications is the generation of isolated attosecond XUV pulses using few-cycle driving pulses. In this case significant progresses have been achieved thanks to the stabilization of the carrier-envelope phase (CEP) of amplified light pulses. In this work we demonstrate that the polarization gating (PG) method with few-cycle phase-stabilized driving pulses allows one to generate few-cycle isolated attosecond pulses tunable on a very broad spectral region. The PG method is based on temporal modulation of the ellipticity of a light pulse, which confines the XUV emission in the temporal gate where the polarization is close to linear. The time-dependent polarization of phase-stabilized sub-6-fs pulses, generated by the hollow fiber technique, has been obtained using two birefringent plates. It is possible to create a linear polarization gate, whose position is imposed by the intensity profile of the pulse whilst the emission time is linked to the CEP of the electric field. The pulses have been analyzed by using a flat-field spectrometer. Continuous XUV spectra, corresponding to the production of isolated attosecond pulses, have been generated for particular CEP values. Upon changing the rotation of the first plate it was possible to tune the XUV emission in a broad spectra range. We have then achieved a complete temporal characterization of the generated isolated attosecond pulses using frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG CRAB). The measured parabolic phase

Erbium:ytterbium fiber-laser system delivering watt-level femtosecond pulses using divided pulse amplification

Science.gov (United States)

Herda, Robert; Zach, Armin

2015-03-01

We present an Erbium:Ytterbium codoped fiber-amplifer system based on Divided-Pulses-Amplification (DPA) for ultrashort pulses. The output from a saturable-absorber mode-locked polarization-maintaining (PM) fiber oscillator is amplified in a PM normal-dispersion Erbium-doped fiber. After this stage the pulses are positively chirped and have a duration of 2.0 ps at an average power of 93 mW. A stack of 5 birefringent Yttrium-Vanadate crystals divides these pulses 32 times. We amplify these pulses using a double-clad Erbium:Ytterbium codoped fiber pumped through a multimode fiber combiner. The pulses double pass the amplifier and recombine in the crystals using non-reciprocal polarization 90° rotation by a Faraday rotating mirror. Pulses with a duration of 144 fs are obtained after separation from the input beam using a polarizing beam splitter cube. These pulses have an average power of 1.85 W at a repetition rate of 80 MHz. The generation of femtosecond pulses directly from the amplifier was enabled by a positively chirped seed pulse, normally dispersive Yttrium-Vanadate crystals, and anomalously dispersive amplifier fibers. Efficient frequency doubling to 780 nm with an average power of 725 mW and a pulse duration of 156 fs is demonstrated. In summary we show a DPA setup that enables the generation of femtosecond pulses at watt-level at 1560 nm without the need for further external dechirping and demonstrate a good pulse quality by efficient frequency doubling. Due to the use of PM fiber components and a Faraday rotator the setup is environmentally stable.

Long Silver Nanowires Synthesis by Pulsed Electrodeposition

Directory of Open Access Journals (Sweden)

M.R. Batevandi

2015-09-01

Full Text Available Silver nanowires were pulse electrodeposited into nanopore anodic alumina oxide templates. The effects of continuous and pulse electrodeposition waveform on the microstructure properties of the nanowire arrays were studied. It is seen that the microstructure of nanowire is depend to pulse condition. The off time duration of pulse waveform enables to control the growth direction of Ag nanowires.

A versatile programmable CAMAC random pulse generator

International Nuclear Information System (INIS)

Abdel-Aal, R.E.

1991-01-01

A new technique for generating linear pulses which can be random in both amplitude and time is described. With this technique, desired values for both pulse amplitude and spacing are set for the individual pulses by the software on a pulse-by-pulse basis. The versatility offered by this software programming allows a wide range of distributions to be obtained; with the user having close control on the distribution parameters. A number of such distributions may also be combined into a single output pulse stream. An implementation in a CAMAC module is presented. Both hardware and software aspects are described and typical performance results for amplitude and time distributions of the uniform and Gaussian type are given. Implications of using the pulser in a typical data acquisition environment on both the data acquisition and the pulser performance are considered. Typical applications are discussed together with some of the limitations. (orig.)

Total and domain-specific sitting time among employees in desk-based work settings in Australia.

Science.gov (United States)

Bennie, Jason A; Pedisic, Zeljko; Timperio, Anna; Crawford, David; Dunstan, David; Bauman, Adrian; van Uffelen, Jannique; Salmon, Jo

2015-06-01

To describe the total and domain-specific daily sitting time among a sample of Australian office-based employees. In April 2010, paper-based surveys were provided to desk-based employees (n=801) in Victoria, Australia. Total daily and domain-specific (work, leisure-time and transport-related) sitting time (minutes/day) were assessed by validated questionnaires. Differences in sitting time were examined across socio-demographic (age, sex, occupational status) and lifestyle characteristics (physical activity levels, body mass index [BMI]) using multiple linear regression analyses. The median (95% confidence interval [CI]) of total daily sitting time was 540 (531-557) minutes/day. Insufficiently active adults (median=578 minutes/day, [95%CI: 564-602]), younger adults aged 18-29 years (median=561 minutes/day, [95%CI: 540-577]) reported the highest total daily sitting times. Occupational sitting time accounted for almost 60% of total daily sitting time. In multivariate analyses, total daily sitting time was negatively associated with age (unstandardised regression coefficient [B]=-1.58, pphysical activity (minutes/week) (B=-0.03, pemployees reported that more than half of their total daily sitting time was accrued in the work setting. Given the high contribution of occupational sitting to total daily sitting time among desk-based employees, interventions should focus on the work setting. © 2014 Public Health Association of Australia.

Time-dependent B-spline R-matrix approach to double ionization of atoms by XUV laser pulses

Energy Technology Data Exchange (ETDEWEB)

Guan Xiaoxu; Zatsarinny, Oleg; Bartschat, Klaus [Department of Physics and Astronomy, Drake University, Des Moines, Iowa 50311 (United States); Noble, Clifford J [Computational Science and Engineering Department, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Schneider, Barry I, E-mail: xiaoxu.guan@drake.ed, E-mail: klaus.bartschat@drake.ed, E-mail: bschneid@nsf.go [Physics Division, National Science Foundation, Arlington, Virgina 22230 (United States)

2009-11-01

We present an ab initio and non-perturbative time-dependent approach to the problem of double ionization of a general atom driven by intense XUV laser pulses. After using a highly flexible B-spline R-matrix method to generate field-free Hamiltonian and electric dipole matrices, the initial state is propagated in time using an efficient Arnoldi-Lanczos scheme. Example results for momentum and energy distributions of the two outgoing electrons in two-color pump-probe processes of He are presented.

Increasing accuracy of pulse transit time measurements by automated elimination of distorted photoplethysmography waves.

Science.gov (United States)

van Velzen, Marit H N; Loeve, Arjo J; Niehof, Sjoerd P; Mik, Egbert G

2017-11-01

Photoplethysmography (PPG) is a widely available non-invasive optical technique to visualize pressure pulse waves (PWs). Pulse transit time (PTT) is a physiological parameter that is often derived from calculations on ECG and PPG signals and is based on tightly defined characteristics of the PW shape. PPG signals are sensitive to artefacts. Coughing or movement of the subject can affect PW shapes that much that the PWs become unsuitable for further analysis. The aim of this study was to develop an algorithm that automatically and objectively eliminates unsuitable PWs. In order to develop a proper algorithm for eliminating unsuitable PWs, a literature study was conducted. Next, a '7Step PW-Filter' algorithm was developed that applies seven criteria to determine whether a PW matches the characteristics required to allow PTT calculation. To validate whether the '7Step PW-Filter' eliminates only and all unsuitable PWs, its elimination results were compared to the outcome of manual elimination of unsuitable PWs. The '7Step PW-Filter' had a sensitivity of 96.3% and a specificity of 99.3%. The overall accuracy of the '7Step PW-Filter' for detection of unsuitable PWs was 99.3%. Compared to manual elimination, using the '7Step PW-Filter' reduces PW elimination times from hours to minutes and helps to increase the validity, reliability and reproducibility of PTT data.