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An experimental investigation was made of the passive mode-locking of a uv-preionized CO2 laser operating in an unstable wavelength-selective resonator using SF6, BCl3 and N2F4 as bleachable gases. Stable repetitive pulse trains with individual pulses having energies as high as 2J and 2 ns duration have been obtained on a large number of P and R transitions of the 00° 1–10°0 band at 10.6 μm. Use of the selectively absorbing gas C2H5OH in the resonator has enabled the production of clean, mode-locked pulses by the saturation of N2F4 without the need of an optical dispersive element.

Measurement of the thermomechanical response of a porous carbon induced by a pulsed electron beam and the associated relief‐wave velocities for the stress pulse unloading are described. These measurements are sufficient to determine an effective Gruneisen coefficient for energy inputs to 500 cal/g. The measurements are accomplished with a new side gauging technique which does not require wave propagation out of the heated region of the sample. A laser interferometer system is used to detect the lateral displacement of a target free surface vs time for the microsecond time duration immediately following deposition. The displacement‐time measurement also permits detection of the unloading wave velocity in the heated material. Through use of a porous‐solid collapse model (the P‐α model), comparisons of the present results to computer calculations of the displacement‐time profile show significant differences from the observed wave profiles.

The flow-charts for an SCR logic variable S(j) and the phase angle θ for use in digital computation of the output voltage harmonic components in a three-pulse cyclo-convertor circuit are discussed. A simple mathematical expression for the digital computation of the components is derived in terms of Fourier series and computed results are presented.

The exact solution is provided for the probability distribution (PD) function of the modulo 2\pi phase of a sine wave in narrow-band normal noise by means of several infinite series. Closed-form exact results are reported at \pi/4 and 3\pi/4 .

Observations of pulsars at low radio frequencies ( ca . 100 MHz) show that the pulses received are broadened in time presumably because of multipath propagation in the interstellar medium. Uscinski’s recent analysis of this effect, by means of a diffraction theory, is here reworked into a form which is readily compared with the results of a stochastic ray-path theory, and the two approaches are found to agree exactly. The reasons for this are investigated. The ray approach suggests a Monte Carlo method of calculating the pulse shape at points deeper into the scattering medium than is possible by the method Uscinski used. Pulse shapes are calculated in this way both for the configuration discussed by Uscinski, and also for the case in which a statistically uniform medium extends along the whole length of the line of sight. Deep inside the medium the pulse shapes calculated agree well with the asymptotic solutions derived previously by the present author. The general problem for a non-uniform medium is also discussed.

A simple model is proposed to account for the peculiar space-charge-free transients observed under pulse excitation in non-crystalline solids in which only one carrier is mobile. In this model, the recombination centres formed by the immobile carriers are regarded as sources of delayed generation. Ein einfaches Modell wird zur Erklarung des besonderen, raumladungsfreien Stromverlaufs, den man in nicht-kristallinen Festkorpern mit nur einer freien Tragerart bei Impulsanregung beobachtet, vorgeschlagen. In diesem Modell werden die aus unbeweglichen Ladungstragern gebildeten Rekombinationszentren als verzogerte Tragerquellen betrachtet.

A series of experiments have been performed designed to confirm recently published calculations of the Fresnel corrected interfrequency correlation function of the time varying rough surface scatter channel. The experiments were performed in a physical model facility using a wind driven water surface. Preemphasized pulse probing was used to extract instantaneous transfer functions over a domain of 200 kHz-1.3 MHz. The results indicate good agreement with theory especially for large surface roughness and frequency domains higher than the cutoff of the coherent transfer function of the channel.

A systematic method, an extension of the average Hamiltonian formalism, is presented for calculating the effects of pulse errors and imperfections in the multiple pulse nuclear magnetic resonance experiments. Application of this method to account for effects of pulse nonidealities such as phase errors, phase transient effects, pulse size errors, and rf inhomogeneity is found to agree with experimental observation, and the results furnish a basis for understanding the complex couplings between the pulse errors and other interactions such as the dipolar and the chemical shift Hamiltonians.

Generation of static charge by friction, discharges in the course of separation from a backing metallic plate, and discharges to an approaching sphere or wire electrodes after such a separation were investigated for various cloths. In the separation procedure, a large proportion of charge was lost through discharges to the backing plate, giving a maximum charge density of about 15 μC/m2 after separation. Oscilloscopic observations of discharges in the approaching procedure revealed that charge is lost through a large number of regular Trichel pulses in the negative corona, while in the positive corona, charge is lost through pulseless glow when fine electrodes are applied; the glow gives way to large pulses as the diameter of the electrode increases. While the amount of lost charge agreed well with the total charge of the pulses and pulseless glow observed by oscilloscope in the approaching procedure, these charges did not agree in the separation procedure. This disagreement was ascribed to the small ratio of the stray capacity to the capacity between the cloth and the backing plate. However, discharges in the separation procedure were found to be similar to those in the approaching procedure by analysing the charge distribution patterns.

The visible luminescence in BCl3 in the field of a high-power short-pulse CO2 laser is studied. It is shown that there are two time regions for the luminescence: the instantaneous, which arises simultaneously with the laser pulse, and a delayed luminescence, which is pressure dependent. Possible mechanisms which cause both types of luminescence are discussed.

Two pulse generators have been developed that are suitable for testing and calibrating high-accuracy analog signal processors as well as high-resolution analog-to-digital converters. One of them has 20 ppm integral non-linearity, 10 ppm/°C thermal drift and 100 ns risetime. The other unit, which features 100 ppm non-linearity and 15 ppm/°C drift, has a risetime lower than 10 ns. It was exhaustively proved that both generators enable the designers and the users of pulse instruments to measure their linearity, stability and resolution in a very reliable way.

One-dimensional models for porous catalysts and laminar flow tubular reactors with first-order reactions at the walls are developed. The method which is used replaces the transport equations containing the local concentrations with equations, similar to those used in the dispersion theory, for the concentrations averaged over the cross section. The main assumption is the approximation of the coefficients in the dispersion equations by those valid for a pulse of concentration introduced at time zero at the mouth of the pore or at the inlet of the tube. The effectiveness factor depends not only on the Thiele modulus but also on the length-to-radius ratio of the catalyst pore. The one-dimensional model for the catalytic tubular reactor provides a good approximation to the area-mean concentration for β ( k s R / D ) up to 1·0. The comparison is made with an exact orthogonal expansion solution developed also in the paper. For larger values of β, say β ≈ 100, the discrepancies between the exact solution and the one-dimensional model may be as high as 50 per cent. Therefore, a generalized dispersion solution is presented to obtain more accurate predictions for β > 1·0.

Traditionally, in the field of lighting and lighting support equipment, the author feels that the most important parameter has been starting. His purpose is to provide an analysis of the performance of several basic pulsing circuits used to start high pressure sodium (HPS) lamps.

Experiments were conducted to measure the arrival time and the power density spectra of wide-band ultrasonic pulses as scattered by a circular, cylindrical, solid inclusion in a matrix of aluminium. Cavities of 3.18 and 6.35 mm diameter were alternately filled with four different solids possessing a wide range of acoustic properties. Results show that the time history and the spectral analysis of the scattered pulses can be used to determine the size of the cavity or the wave velocity in the solid inclusion.

Pulse rise time and energy resolution of a planar Ge(Li) detector were investigated in the temperature range from 77 to 200 K and in transverse magnetic fields up to 4 T. For temperatures below ≈ 150 K the experimental results confirm the decreasing influence of magnetic fields on the spectrometer properties predicted by calculations of the drift mobilities in strong magnetic fields 1 ). Above this temperature a continous increase of pulse rise times is observed, whereas the energy resolution deteriorates abrubtly at ≈ 160 K and improves again at higher temperatures. The optimum performance in strong magnetic fields is obtained at 140 K.

Two superconducting dipole magnet modules have been operated successfully at BNL since October 1973 to bend 30 GeV/c protons from the AGS by 8° in the new North Area beam to the 7-ft. Bubble Chamber. The magnets have been energized for over 1000 hours, and, of that time, have been traversed by the proton beam with beam intensities up to 5 × 1012protons per pulse, for about 750 hours. Operation of these series connected magnet units, each 2 meters long at 35kG has been routine even when they were intermittently subjected to beam heating of several hundred joules per pulse due to other operational beam difficulties. Experiments were also performed where copper blocks were inserted 2 meters upstream, resulting in very large interaction rates in the beam tube inside the units. A magnet quench occurred with target thicknesses such that energy approaching 1kJ per pulse was being absorbed in the system. These are the first superconducting magnets in operation in a primary beam on which extensive radiation heating tests have been performed.

A normalized Poynting vector impulse response approximation evaluated computationally at selected points within and near an ice sphere is used to show that the actual physical processes in diffraction of plane waves are consistent with high frequency analogs proposed previously. Failure of the low frequency pulse components to satisfy Snell's law of refraction leads to differences in a detailed description of scattering by an ice sphere.

T he influence of second-order effects on the propagation of a weak dilatational stress pulse in a heat-conducting elastic material is investigated. As a first approximation, the problem is studied using the linear theory of thermoelasticity. It is found that thermal diffusion dominates the wave motion, and a time is reached when second-order terms must be considered. The wave motion is then found to be isentropic and the shock structure is governed by Burgers's equation. Solutions to this equation are obtained and the influence of heat-conduction on pulse propagation in elastic materials is discussed, with some numerical results being presented for copper. Also, previous work in linear thermoelasticity theory is clarified and related to known results in linear and nonlinear elastodynamics.

Summary A value for the radius of the inner core is computed from differential PKiKP (PKiKP minus PcP) arrival time data and current Earth models. The data support an inner core radius of 1220-1230 km, the exact value depending on the model P velocity near the inner core boundary. For a model incorporating a decrease in the velocity gradient just above the boundary, in the transition zone of the core, the best value for the inner core radius is 1227.4+0.6 km. Comparison of pulse shapes and pulse durations for P, PcP, and PKiKP phases suggest that the core boundaries are sharp discontinuities relative to 1-s period waves. Complexity in explosion-related PKiKP signals is attributed to source effects.

This paper deals with the response of a curved bridge deck to sonic boom loading. The curved panel is considered as an annular sector plate with the two radial edges simply supported and the circular edges free. The method is equally applicable to other edge conditions. The normal mode method of analysis is used. The response to various durations of boom period as well as different pulse shapes has been determined and presented in the paper.

Digital signal transmission in electronic communication links provides the possibility of periodic reshaping of the electronic pulses by so-called regenerative repeaters, thereby keeping the signal above the noise level. This concept of noise minimization is applied to the optical transmission of pulse-coded images. Optical elements are described which correspond to the regenerative repeaters used in electronic transmission systems. They are based on holographic as well as incoherent methods. Examples illustrating the basic idea are provided.

The measurement of the kinetics of intermediates formed during the pulse of electrons is discussed, using Cerenkov emission as monitoring light for fast spectrophotometric analysis. The emission, diminished by self-absorption due to intermediate products, is derived as a function of optical density for the simplest kinetics—zero-order build-up during the pulse. Test for deviation from zero order are developed.

It is proposed that amplified spontaneous emission in the soft-x-ray region can be obtained using inner-shell population inversions arising from the Auger effect. For Na+, it is shown that with present-day technology it appears possible to generate a pulse of 10-5 to 10-7 J in less than a nanosecond at 410 A. The possible effect of interatomic Auger processes in the solid is discussed but high-electron-density effects are not accounted for.

This paper contains an account of various experiments associated with the propagation of a pressure pulse up a vertical column of liquid. When such a pulse reaches the upper free surface of the liquid it is reflected downwards as a pulse of tension. This method therefore provides a means of subjecting the liquid to tension under dynamic conditions of stressing. If the value of the tension at any depth exceeds a certain critical value the liquid will cavitate. Values of this critical tension T were measured for liquids of varying viscosities η and it was found that the empirical relation T=kη0.1 holds. Secondly, pulse propagation across the interface between two immiscible liquids was studied, and it was found that the maximum tension which could be sustained by an interface separating silicone oil and water is less than the tension which produces cavitation in either of these two liquids. Thirdly, it has been found that the cavitation produced shows several cycles of growth and collapse, a phenomenon which has been observed photographically by previous workers.

A versatile potentiostat system with a digital logic function generator is described. The signal generator features a quartz oscillator which provides pulses of highly constant frequency (1MHz). The pulses of frequency selected by three frequency dividers are counted by three decimal counters and at the same time drive a D/A converter. The potential ramps are thus obtained as successions of small potential steps. All of the most common potential waveforms (triangle, ramp, trapezoid, pulse) are available. A very wide range of potential scan rates (0.01mV.s−1 to 2.104V.s−1) is provided, either in repetitive or in single-shot operation mode. Great accuracy of the rise, hold and fall times are the main advantages of this instrument.

A computer algorithm is presented for the optimum selection of a series of train of force pulses for application to a continuous system. The optimized pulse train generates oscillations in a system to match within specified error bounds the responses which would be produced by a continous loading of arbitrary nature such as earthquake excitation. This computationally efficient algorithm is applied to several examples including a model of a physical system. It is shown that it is feasible to adequately simulate the motion of a complicated system by using appropriate force pulse trains. (Author)

We report a pulse sequence measurement of T1 in the J=0 → J=1 rotational transition in OCS in the pure gas, OCS–He mixtures, and OCS–CH3F mixtures at low pressures. This pulse sequence method is similar to the π, τ, π/2 pulse sequence used in nuclear magnetic resonance to measure T1. The pulse method of measuring T1 in rotational systems has several advantages over the analysis of transient absorption (transient nutation) results or the analysis of power broadened steady state absorption lines. We find T1=T2 for the J=0 → J=1 OCS transitions in pure OCS, OCS–He mixtures, and OCS–CH3F mixtures.

A decade ago, two of the authors presented a paper reporting on diffraction and interaural delay of a progressive wave caused by the human head [J. Acoust. Soc. Am. 36, 1993(A) (1964)]. Six live subjects were used in those experiments. The publication was delayed pending measurements on artificial heads then being planned. In this paper, two series of data obtained with the aid of the Acoustical Manikin [J. Acoust. Soc. Am. 42, 204–207 (1967)] are compared with the earlier experiments: (a) Data based on phase measurements; (b) Data obtained using a bandwidth‐limited delta pulse. All three methods provide useful information about interaural diffraction and delay, albeit the third method appears to be the most reliable.

The experimental requirements for pulse FT NMR measurements of spin-lattice relaxation times ( T 1 's) are quite demanding. This paper treats many of the critical experimental parameters in T, experiments; the data and discussions rely on previous literature as well as an extensive set of new measurements. It is shown that variables such as sample geometry and state, transmitter rf pulse power, computer and data processing characteristics, and instrumental gain stability and magnetic field homogeneity must all be optimized or closely controlled in order to obtain accurate data. The choice of a specific pulse sequence [inversion-recovery (IRFT), saturation-recovery (SRFT), progressive saturation (PSFT) or other variations] depends on a number of factors. The SRFT and PSFT sequences are faster and somewhat more convenient than the IRFT method. However, the pulsing requirements in the PSFT method are most stringent and large errors may easily be introduced in these T, measurements. The effect on determined T 1 's of mis-set pulse lengths and variable spectral offsets was studied for the three pulse sequences. The PSFT sequence can give substantially (25% or more) incorrect T 1 's while systematic errors in the IRFT and SRFT experiments are under 10–15% except under extreme conditions. The SRFT sequence is approximately twice as fast as the IRFT scheme for determination of T 1 's longer than a few seconds. Because of their relative insensitivity to instrumental and other experimental deficiencies the IRFT or SRFT pulse sequences will be preferred for T, measurements in the great majority of laboratories. Because homospoil pulses are utilized in the SRFT sequence, it is the preferred method only for measurement of T 1 's longer than about 5 seconds.

Relationships between photobleaching recovery times and excited state lifetimes for mode-locking dyes are treated. It is shown that under appropriate excitation conditions the recovery time may be substantially shorter than the lifetime of the excited state, in agreement with results which have been reported for DODCI. The existence of a two component decay is consistent with a self-dumping mechanism operative at high power densities. Proposed production of a DODCI photoisomer is examined with respect to nonlinear effects present during intense pulse excitation.

Synchronously pumped dye lasers are studied. The ultrashort pulse evolution is numerically investigated for a large number of round-trips. A stationary pulse is found.

Reported herein are a theoretical treatment and an experimental investigation that deal with the interpretation of data from a pulse propagation test on a frequency‐dependent clay soil. A transfer function, which considers the superposition of an instantaneous response and the various modes of vibration, is obtained to relate the stress at the fixed end of a specimen to that at the input end, and the modulus of elasticity and viscosity are deduced from analyses of the fundamental resonant frequency of the specimen. Experimental data from shock tube tests on a clay soil provide a means for comparing the analytical predictions with the actual response. It is shown that use of the intuitively defined arrival time of a pulse yields values far too high for the modulus of elasticity, and higher values of damping and shorter lengths of specimen both contribute to making the results more unpredictable. Both the modulus of elasticity and the viscosity of the clay are found to be strongly dependent on frequency, the former increasing and the latter decreasing with increasing frequency.

An investigation was made of the energy balance of a free-oscillation iodine amplifier pumped with light generated by a high-current discharge in the active gas. Some of the pump energy was absorbed in a shock wave traveling ahead of an expanding discharge plasma. Optical inhomogeneities in the amplifying layer were investigated. A transverse gradient of the refractive index in this layer could reach 106 cm–1. The magnetic field of the discharge influences strongly the laser emission spectrum, shifting it by 0.2 cm–1 during a pulse and broadening it to 0.3 cm–1. When the discharge current passed through zero, the stimulated emission was due to the unperturbed F = 3 → F' = 4 transition in the hyperfine structure of the iodine atom. Thus, a short pulse could be amplified at the moment the current passed through zero.

Applying the parabolic approximation, the equations for two-frequency symmetric and antisymmetric mutual intensity functions for waves propagating through a random medium are derived, including the multiple scattering effects. These functions are applied to derive the general formulas for the covariance functions of narrowband pulses. They are used to compute the signal intensities for pulse trains passing through an ionospheric irregularity slab.

A 128-channel time-to-digital converter with a resolution from 0.5 μs up to 0.45 s per channel is described. The time base is taken from a crystal oscillator, which can be replaced by an RC-oscillator increasing the time width per channel up to 1000 s. The instrument is primarily designed for measurements of nuclear lifetimes longer than a few μs. The converter contains a read-out buffer which permits several time intervals to be measured with one common start pulse. A digital delay and a sampling function are incorporated in the instrument. Description and figures of merits are given. The measurement of a half-life in 180 W, produced in the pulsed beam from a cyclotron, is used as an illustration of the performance.

Pulse irrigation is suggested as an irrigation technique achieving a relatively low application rate while using an irrigation device with a higher application rate. A complete pulse irrigation is composed of a series of irrigation time cycles where each cycle includes two phases: the operating phase followed by the resting or nonoperative phase. The variables of the pulse pattern, the real irrigation time, the resting time, and the total time of a single pulse are defined as a function of the irrigation parameters and the number of cycles in the irrigation. A method is suggested to determine the number of cycles in one pulse irrigation which in general will be in the range of 5-10 cycles. According to the suggested principles and procedure, the required steps for pulse irrigation design are given. Numerical examples are included.

The formation of sonic pulses in the nearfield region of a pulsed piston radiator has been investigated by simulation on a digital computer. The results give insight into the sonic radiation process, showing the formation of pulses that replicate the piston motion, with trailing disturbances which originate from the rim. A comparison is made between pulsed and CW beam profiles, showing that there is little difference for moderate pulse lengths.

A simple computational model is developed for incorporating the effect of elastic-plastic deformation of piping on pressure transient propagation in a fluid system. A computer program (PLWV) is described which incorporates this structural interaction model into a one-dimensional method-of-characteristics procedure for fluid hammer analysis. Computed results are shown to be in good agreement with available experimental data. The most significant effect of plastic deformation is to limit the peak pressure of a pulse leaving a pipe to approximately the yield pressure of the pipe, if the pipe is sufficiently long.

Except for exact numerical solutions to the point explosion problem[1], there is no simplified technique which is uniformly valid over the Mach number domain extending out to near sonic flows. Recently, however, a technique was proposed by Bach and Lee which has produced surprisingly accurate results for the entire regime of blast wave propagation[2]. The method is based on the assumption that the density profile behind the shock front may be described by a power law in the radius. This assumption, which is generally observed to be very good, enables one to integrate the continuity equation analytically to obtain the velocity which is the only other parameter which appears in that equation. Upon performing the integration, the momentum equation can then be integrated directly for the pressure profile. These analytic results are obtained in terms of the as yet unknown shock trajectory. The shock position-time relationship as expressed through the shock decay coefficient may be found, however, in terms of an integral energy conservation relation. The result is a coupled set of nonlinear ordinary differential equations which when solved in terms of appropriate boundary conditions yield the shock-wave decay coefficient. In the present work, we have extended this method to unsteady shock waves into which energy is deposited in a time-dependent fashion during propagation. The technique is applied to the case of energy addition by pulsed and cw laser radiation. Radiant energy absorption due to inverse bremsstrahlung is included and the nonequilibrium electron cascade process (breakdown) is accounted for in a phenomenological manner. A parametric study is conducted in which the effects of laser pulse shape, pulse duration and pulse power are determined. Laser pulse profiles typical of CO 2 TEA lasers are considered. Our results are compared to laser-driven detonation (LSD) waves observed experimentally in laser-target interaction experiments as described in the literature. In addition, the results are compared to exact numerical computations.

Pulse radiolysis of solutions of alkali metal cations in tetrahydrofuran (THF) demonstrates the formation of solvated electrons es−, alkali metal cation-ion pairs (M+, es−), and alkali metal anions M−. This paper describes the spectra, extinction coefficients, and radiolytic yields of es−, lithium, sodium, potassium, and cesium species in THF. The reaction kinetics are complex but largely involve reactions A and B[Formula: see text]with the concomitant disappearance of all three species by reaction with radiolytically produced radicals. Rate constants and ion-pair dissociation constants for es− and the sodium and potassium species are presented and compared with data established from studies of blue solutions of alkali metals dissolved in THF.

This paper considers an example of the propagation of a finite wave-train in a plasma of relatively simple dispersive properties. In this case, the wave field can be evaluated exactly. The concept of a wave-packet moving at the group speed can therefore be tested rigorously. Various approximations to the field, physically more transparent than the exact solution, are presented and compared with the latter. One of these, relevant in the neighbourhood of the ideal group front, is in fact applicable to a wide range of dispersion laws. The paper demonstrates broadening with time, and eventual disappearance, of the pulse.

A p-n junction diode with an additional n+ island diffused into its anode and shortod to it is shown to exhibit a switching effect in its reverse characteristic if its geometry is chosen correctly. The effect is similar to that encountered in a PIN stop recovery diode and depends on the stored minority charge at the end of the forward conduction period and on the applied voltage frequency and waveform. The device is completely compatible with npn IC technology and can be used for pulse generation. A theoretical analysis of the device operation and the switching effect is made anil compares well with the experimental results.

Pulse magnets were built utilizing tape wound cores in order to lower magnet power requirements at high pulse repetition rates and high gap flux densities. The primary reason this project was undertaken was to bend higher energy beams with existing power supplies. A decrease in the amount of electrical steel from 2720 kg for the original laminated core pulse magnet design to 260 kg and the elimination of the ceramic vacuum chamber resulted in substantial savings. Two new magnets are now operational with the capability of deflecting 40 to 50 GeV/c beams through ± 0.35° (6.13 mrad) at a PRR = 360 pps. The old magnets with the same power supplies could only bend 21 GeV/c beams through the same angle. Principal features of this design, including test data, are presented.

In this paper the H integral equation is investigated for the problem of plane wave diffraction by a rectangular aperture cut into an infinite, perfectly conducting screen. The field distribution in the aperture is calculated by the application of the method of moments with point matching and pulse expansion functions. Various sized apertures are considered and the numerical stability of the solution is discussed.

Summary The composition of the reducible ammonia complex of cadmium and its reduction rate contant were determined. The calculation is based on the assumption that practically only one complex undergoes reduction at the electrode and that the equilibrium between Cd2+ ions, their ammonia complexes and ammonia is perfectly mobile. The form of the current-voltage curves at different rates of potential change confirms the plausibility of these assumptions.