Pulse Half-width Research Articles

Pulsed single-photon Bessel beams propagation in non-Kolmogorov turbulent atmosphere

The analytic expressions are derived for the turbulent broadening, the long-term temporal broadening, the acquisition probability of single-pulse and the transmittance probability density of a pulsed space-time Bessel photon-beam propagating along a slant path in weak non-Kolmogorov atmospheric turbulence, based on the assumption of a pulsed Bessel beam with the initial Gaussian temporal shape of pulse and diffraction-free spatial distribution. It is shown that the turbulent broadening and the long-term temporal broadening are the nolinear-increase functions of the index of non-Kolmogorov turbulence and the effect of non-Kolmogorov index on the acquisition probability of single-pulse can be approximatively described by a Gaussian function with a peak value at non-Kolmogorov index close to 3.7 for the case of the input half-pulse width greater than picosecond (ps). The transmittance of probability density is decreasing as the increasing of the structure constant of the index of refraction, the zenith angle of communication channel, the propagation path and the pulse broadening. There is turbulent diffraction for Bessel beam propagation in turbulent atmosphere, but its free-space diffraction-free characteristic is reservation.

Investigation on competition between the input signal and noise in a Brillouin amplifier

We theoretically and experimentally investigate the competition mechanism between the input signal and noise in a Brillouin amplifier, and the influence of the delay time of the pump pulse relative to the signal pulse on this competition. Results show that as the input signal intensity increases, the amplified Brillouin scattering (ABS) noise gradually weakens, while the signal amplification predominates. When the ratio of the input signal to the pump intensity is greater than 10−4, the ABS noise will be almost completely suppressed. The delay time should be controlled as the pump pulse half-width to achieve high signal-noise-ratio and high amplification.

A dividing ratio changeable digital PLL based on phase state memory and double clock‐edge detection

AbstractIn this paper, we propose a dividing ratio changeable digital phase‐locked loop (PLL) based on phase state memory and double clock‐edge detection that satisfies the three characteristics of low jitter, wide lock‐in range, and fast pull‐in at the same time. The counter for the double edge detection of the base clock reduces the circuit scale by using a selector. In the steady state, the output jitter of the proposed digital PLL is always a half pulse width of the base clock regardless of the frequency fluctuation of the base clock. Also, the upper bound frequency of the lock‐in range becomes six times that of the conventional dividing ratio changeable PLL, when the permissible output jitter is identical. Furthermore, the fast pull‐in is finished in one cycle of the input signal and the pulse width of the multiplication output signal becomes almost constant. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(9): 19–26, 2010; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10251

Contact Reading/Writing of Continuous Media and Patterned Media with a Static-tester

We measured perpendicular magnetic recording media with a static tester to analyze the read-write characteristics (SN ratio, ATE, and recording margin) of future bit patterned media (BPM). We clarified that the measured current of a granular-type perpendicular magnetic recording medium's reproduction waveform at half pulse width, T50, and the magnetization transfer parameters, were small. The read-write resolving power is thought to improve and reproduce a steep magnetization transition through contact recording. Furthermore, we measured the BPM samples and ascertained that the actual measured values conformed to those calculated qualitatively. In addition, we found the dot pitch from a reproduction wave did not depend on the dot size, and it was almost the designed value, and we confirmed that the standard deviation was around 6% of the dot pitch at dot lengths longer than 40 nm.

Method for measuring the PCR proton spectrum in the energy range of > 1016 eV

Criteria for selecting proton events among the total sequence of events from primary nuclei of cosmic rays with zenith angles θ 10 PeV; at lower energies, the average mass composition is almost unchanged. The method used in (3, 4) is based on the correlation of the Cherenkov light (CL) pulse halfwidth at a long distance from the shower axis with the shower maximum position. It is well known that the CL transverse distribution function (TDF) is also sensitive to the primary nucleus mass. However, CL detectors of ground-based installations collect light from only a small fraction of the shower area; therefore, detailed reconstruction of the CL TDF is complicated. In the SPHERE-2 experiment, it is intended to use the shape of CL TDF to determine the PCR composition, since detectors of this installation can survey about half the shower area. The operating principle of this telescope is based on the idea to measure CL produced by extended atmospheric showers (EAS) and reflected from the snow surface (7). The optical scheme of the SPHERE-2 installation represents a Schmidt camera with a mirror 1.5 m in diameter and a mosaic of 109 photomultipliers in the mirror focal surface. Thus, this system allows measurements of the quantity proportional to the total CL amount within the field of view of each detector of the mosaic. In this paper, the criteria allowing separation of a certain known proton fraction from the total number of PCR nuclei are studied using the Monte Carlo method. The Lake Baikal level (H0 = 455 m above sea level) and the detector spatial resolution δr =8 0m corresponding to the SPHERE-2 installation position at a height of 1 km over the snow surface of Lake Baikal are considered. In this case, the diameter

A short-pulse Ka-band instrumentation radar for foliage attenuation measurements

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

位相状態記憶制御とダブルクロックエッジ検出に基づく分周比可変型ディジタルＰＬＬ

In this paper, we propose the dividing ratio changeable digital phase locked loop (PLL) based on phase state memory and double clock-edge detection in which satisfies three characteristics of a low jitter, wide lock-in range, and fast pull-in at the same time. The counter for the double edge detection of the base clock reduces the circuit scale by using the selector. In a steady state, the output jitter of the proposed digital PLL becomes always half pulse width of the base clock regardless of the frequency fluctuation of the base clock. Also, the upper bound frequency of the lock-in range becomes 6 times that of the conventional dividing ratio changeable digital PLL, when the permissible output jitter is identical. Furthermore, the fast pull-in is finishes in one period of the input signal and the pulse width of the multiplication output signal becomes almost constant.

High-gain amplification of weak Stokes signal of stimulated Brillouin scattering in water

The influences of the delay time, the cell length and the pump energy on the gain amplification of weak Stokes signal of stimulated Brillouin scattering (SBS) in water are investigated theoretically and experimentally. In the experiment a frequency-doubled seed injection Nd:YAG laser with a pulse duration of 7.2 ns was used. Results showed that the pump pulse should lag the Stokes signal pulse by an amount equal to pulse half-width to obtain the maximum gain. Depending on the pump energy the signal below 10-5 mJ is linearly amplified. By using CS2 as amplifier medium, a Stokes signal of 1pJ from water is amplified with high gain (7×107) in the regime below the pump's self-SBS threshold.

2.79 μm erbium laser with lead–lanthanum zirconate titanate ceramics electro-optic Q-switching output coupler

Highly refractive and transparent lead–lanthanum zirconate titanate (PLZT) ceramics are used for an output coupler of the erbium yttrium scandium gallium garnet laser (λ=2.79 μm) that simultaneously serves as the laser electro-optic Q switch. The optical aperture of such a dual-function PLZT element was 6×6 mm2 and the thickness was 3 mm. For Q switching, short ≈3 μs negative voltage pulses (1500–1800 V) were applied to the positively direct current biased (≈1400 V) PLZT element. Single-pulse lasing with a pulse half width of 160–170 ns was observed at short and long delays of the Q switch with respect to the pump flash. The highest output energy of 20–22 mJ within 1.5–2.5 μs, consisting of two or three pulses with 130 ns half width was obtained at an intermediate delay of 90–110 μs.

Atmospheric-pressure plasma treatment of ultrahigh molecular weight polyethylene fibers

The performance properties of composite materials reinforced by ultrahigh molecular weight polyethylene (UHMW-PE) fibres depend critically on the fiber/matrix interfacial characteristics. The chemical inertness and very low surface energy of UHMWPE fibers, however, results in a fiber/matrix interfacial strength much less than ideal for such applications [1]. Several teams made remarkable achievements in the surface modification of UHMW-PE by low-pressure plasma treatment at pressures below one Torr (130 Pa) [2–6]. However, these low-pressure plasma treatments require vacuum systems and do not lend themselves easily to an industrial implementation. In this study UHMW-PE fibers were treated by a nitrogen plasma at atmospheric pressure, where the plasma treatment can potentially be realised with less technical effort. A nitrogen plasma was chosen because of its low degrading effect and high radical density creation [6, 7]. A commercially available UHMW-PE filament bundle of 150 filaments (Dyneema SKX 65, dtex 165) was cleaned with acetone before the treatment. The plasma treatment was performed using a pulsed surface discharge reactor that consisted of two on-axis-arranged electrodes housed in a glass chamber [8]. Nitrogen of a technical purity was introduced into the chamber with a flow rate of 1 cm3 s−1. The ground stainless-steel tubular anode was 1 mm in inner diameter. The cathode was a 15 mm-diam. hemispherically capped brass rod with a 2 mm-diam. hole in its axis. The distance between electrodes was adjusted to 15 mm. The treated filament bundle moved on the axis of the electrode system with a speed of 100 mm s−1. The cathode was connected with a tyratron source of pulsed high voltage with a pulse frequency of 100 Hz, a peak voltage of 25 kV, pulse rise time of 75 ns, and pulse half-width of 400 ns. The discharge power was approximately 10 W. To illustrate the effect of the plasma treatment on fiber surface properties, the fiber/rubber matrix adhesion values measured using the untreated and treated fibers were compared. The samples were prepared by pressing the filament bundle between two slides from a conventional polybutadiene rubber blend. Subsequently, the samples were vulcanised at a temperature of 145 ◦C. Adhesion of the fibers to rubber was characterised in a standard H-peel test by the force required to draw out the filament bundle of a rubber block. The adhesion values (the averages of twenty measurements) for the reference and plasma-treated fibers were 1.7 and 2.5 kN m−1, respectively, i.e. an increase of 44% was obtained by the plasma treatment. As stated by Jacobasch et al. [9], some insight into the adhesion behavior of polymer surfaces can be obtained also by zeta potential measurements with varied electrolyte concentration. Preliminary results of our ζ -potential measurements are shown in Fig. 1. From the results it is evident that anions (Cl− and OH−) present in KCl electrolyte are preferably adsorbed by the treated fiber surface. The observed decrease in negative ζ -potential values due to the plasma treatment (corresponding to a decrease of the electrical double layer thickness [9]) indicates a higher hydrophilicity of the plasma-treated fibers. An increase in the pH corresponding to the zero ζ -potential (isoelectric point) indicates a creation of basic surface groups by the plasma-treatment. This is consistent with the basicity of polyethylene tapes treated by atmospheric pressure nitrogen plasma [10] found on the base of contact angle measurements. Our ζ -potential measurements, in an agreement with the results of Gresseer et al. [11] and Wakida et al. [12], affirm that ζ -potential measurements can be a useful technique in determining of technologically

Correlation between the optical signatures and current wave forms of long sparks: applications in lightning research

Broad-band optical output (500–850 nm) and channel current of 500 mm long sparks were measured. Experiment was conducted for several current rise times. The optical rise time and current rise time show a linear relationship. During the rising portion the optical signal closely follows the current wave shape. There is no detectable variation in the time separation between the starting point of the optical signal and that of the current signal, with varying current rise time or current amplitude. One can apply this result to use the optical signal, which is measurable, to estimate the information regarding the variation of current with altitude of long spark channels. One such case, that will be benefited from the results of this research, is the measurement of peak current along the channel of both artificial and natural lightning. For a 250 mm gap we performed the experiment by increasing the current amplitude between about 0.5 kA and about 3.5 kA, for the same current rise time. The current rise time and optical rise time remain approximately at a steady level with current amplitude, while the former is always slightly less than the latter. Hence, we suggest that the results obtained in this work may be extended to the measurements of the current along lightning channels where the peak currents are in the range of few tens of kiloamperes. For a given current pulse half-width, that of the optical pulse shows a linear variation with current amplitude. We also observed a linear relationship between the current amplitude and the optical amplitude in the range of current amplitudes relevant to this experiment.

Design Concept of Fast Spectrum Pulse Reactor with Packed Core of Coated Dilute Fuel Particle.

A fast neutron pulse reactor that can provide high neutron fluence with relatively short pulse half-width is proposed, which has a core constituted of uranium or plutonium nitride diluted with titanium nitride, formed into particles coated with titanium nitride and packed without moderator. Dilution of the fuel kernel is shown to enhance the neutron fluence obtainable within the allowable maximum fuel temperature. Titanium nitride possesses high heat capacity, which also enables large neutron fluence before attainment of the allowable maximum fuel temperature. As fuel, 233U and 239Pu have the advantage over 235U of permitting criticality to be attained with lower fuel enrichment. The maximum fluence obtainable with a fuel composition of 239Pu enriched to 0.6 and diluted to 0.11 (239PuN+238UN)/(239PuN+238UN+TiN) volume is 3x1016 n/cm2, which is 50 times what has been indicated for a conventional fast pulse reactor. The pulse width is significantly longer than that of the above-mentioned conventional reactor, but if necessary it can be shortened down to roughly equal value by adopting non-diluted fuel, at the expense of only reducing by half the obtainable neutron fluence.

A study of nickel electrothermal atomization

The kinetic order of generation of the atomic vapor of Ni is determined as a function of the initial mass of analyte. For masses up to 3.0 ng, a kinetic order equal to 1 is obtained, with atomization energy and pulse half-width independent of the analyte mass. However, for sample mass in the range 4.0–8.0 ng, a kinetic order equal to 2 is determined with a constant atomization energy and a pulse width that increases as the initial mass increases. Accordingly, a first-order kinetic model is employed to describe the atomization profiles of analyte masses up to 3.0 ng. To determine the vapor formation and dissipation rate constants k 1 and k 2, the rate equations for this model were solved using boundary conditions at t y, the time at which the rate of change of absorbance presents a minimum value and the temperature has already reached its maximum value. Employing the kinetic parameters of this model, a good description of the absorbance profiles is achieved and the theoretical behavior of the peak absorbance and the area of the pulse, as a function of the analyte mass, is predicted.

S wave coda Q from 3 to 20 Hz and P wave Q for foreshocks and aftershocks of the Petatlan Earthquake

In order to understand better the variations of mechanical properties close to the source and the failure process in the upper portion of the crust in a geologically very young subduction zone, the seismic S wave coda Qc from 3 to 20 Hz and P wave half pulse width Qp from 6 to 12 Hz were determined for selected foreshocks and aftershocks of the 1979 Petatlan, Mexico, Ms = 7.6 earthquake. To limit the region being sampled, the quality factor of S coda, Qc, was obtained from the first 10 s following the S onset. Qc exhibited a strong spatial, temporal, and frequency dependence, and in the small foreshock portion of the aftershock area, Qc and (to a lesser extent) Qp were significantly lower before the mainshock than afterward. The frequency dependence n, in Qc (ƒ) = Qo ƒn, was practically constant for aftershocks in four different regions (n = 1.32±0.03) and for foreshocks (n = 1.43±0.07). Only in one peripheral region‐station pair did we find a significantly different n (n = 0.97±0.09). Our observations indicate that Qc, and perhaps the frequency dependence n, are sensitive to the physical property changes in the source region and might be useful as predictors of large earthquakes in a shallow subduction zone environment.

Cavity separations and the associated impulsive pressures around a cavitating cylinder. (1st Report, Vortex-type cavitation in the wake and in attached cavitation).

The flow patterns and the fluctuating pressures around a cavitating circular cylinder, especially about the wake and the attached cavity separation, have been systematically studied by high-speed photography and by the wave analysis for several Reynolds numbers for Re=4×105 to 7×105, in the cavitation tunnel at Tokyo Metropolitan Institute of Technology. The impulsive pressure originated in the core of vortex-type cavitation, which occurs frequently in the turbulent wake, is about -70 kPa in amplitude and 4 ms in half-width duration. The attached cavitation occurs intermittently according to the fluctuating pressure cycles of the Karman vortices and its inception point is located within the turbulent transition region where the high-frequency fluctuating pressures of about 7 kHz are occurring. In the attached cavitation, the transitional waves appear at he boundary of the clear and the cloud cavity. From this boundary, a lump of bubbles separates leaving the clear cavity. The impulsive pressures have a violent spike pulse of about 260 kPa in amplitude, 2 ms in period and 500 μs in pulse half width at Re=7.2×105.

Recorded magnetizations and magnetic fields in media derived by computer simulation

The parameters of magnetic media dependences of the half pulse width, PW/sub 50/, and output voltage of isolated pulse, E/sub 0/, were investigated using computer simulation. It was found that the squareness in the x direction (Sx) dependences of PW/sub 50/ and E/sub 0/ are different from the saturation magnetization dependences of PW/sub 50/ and E/sub 0/ and that PW/sub 50/ hardly changes with Sx for high S* (PW/sub 50/ varies as Sx/sup 0.04/), although it is proportional to Sx/sup 0.48/ for low S*. The corresponding magnetization and the total magnetic field are also investigated for high Sx and low Sx media in three steps. These are the reversed write current, removed head, and reproducing process steps. It is confirmed that transition regions are formed mainly during the reversed write step.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Stimulated Raman Scattering and Self-phase Modulation of Ultrashort Light Pulses in Optical Fibres

Stimulated Raman scattering of picosecond pulses in optical fibre is investigated, with account taken of pulse walk-off by group velocity dispersion, pump depletion and chirp production by the intensity-dependent refractive index. An analytical solution of the basic equation is given by which the characteristic parameters of the Stokes and pump pulses, such as pulse half-width, intensity, mid-frequency and chirp, are calculated. It is shown that the chirp of the Stokes pulse does increase faster than that of the pump pulse with increasing fibre length and may surpass it by nearly three times after the pulse walk-off.

Laboratory source of synchrotron radiation: TROLL-2

A laboratory synchrotron radiation (SR) source TROLL-2 is described. Its main parameters are as follows: the energy of the accelerated particles = 24 MeV; the orbit radius = 20 mm; the SR pulse half-width = 2 ms, the maximum spectral radiant power (at λ = 350 nm) = 1.2×10 6 W/m.

Mass spectrometric investigation of gas switching in an InGaAsP MOVPE system

The mass spectra of PH 3, AsH 3 and TMG in H 2 are presented. Measurement of PH 3 and AsH 3 pulse sequences in H 2 and N 2 as a carrier gas in an MOVPE system are reported. The studies are carried out with total gas flows in the range of 3–9 1/min, at atmospheric pressure and low pressure down to 25 mbar. Several gas sampling positions in the reactor are investigated. An effective increase of pulse spectra resolution is obtained using low pressure. Pulse sequences are varied between 2 s pulse duration /30 s pauses and 0.5 s pulse duration /0.5 s pauses. The normalized pulse half-width is independent of the sampling position. Using N 2 as a carrier gas, pulse echos can appear.

Media limitations on achievement of maximum detection window

The recording performance of a digital recording system is primarily dependent upon the isolated half pulse width (T 50 ), signal amplitude, intersymbol interference (ISI), signal to noise ratio (SNR) and the horizontal detection window margin (T m ). These characteristics are related to the thickness and magnetic properties of the media, as well as the head/media interface. This paper addresses the relationship of the media characteristics in longitudinal digital magnetic recording for both particulate and thin film media to the overall recording system performance. The results are shown to proceed from further development of the quasi-optimum time containment filter analysis for media noise dominant and electronic (white) noise dominant recording channels [1], [2].