Showing papers on "Pulse duration published in 1976"

Estimation of cell size from pulse shape in flow cytofluorometry.

Abstract: The fluorescence pulse widths (pulse duration) generated by fluorochromed cells in a flow-through cytofluorometer provide useful information regarding cell (or nuclear) size and possibly other morphologic features. Simple fixed thresholds just above background noise can be used to identify these pulses, but measurements are then strongly affected by random noise and will vary as a result of both pulse amplitude and pulse shape. In this paper, we propose two alternative, amplitude-independent estimates of pulse width. The first is based on a threshold at some fraction of pulse height, or on a pair of thresholds scaled to some fixed central fraction of the total integrated intensity. The second is based on the ratio of pulse area to peak height. The quantitative properties of these width estimators is studied with simulated fluorescence pulses and with experimental specimens of fluorchromed polystyrene spheres, pollen and spores of known different diameters. The results indicated that absolute particle diameters can be measured within a precision of approximately 1 mu using instruments for flow cytofluorometry.

Method of decorating a transparent plastics material article by means of a laser beam

Abstract: A method for the decoration of a transparent plastics material article comprising the steps of providing an article having a transparent plastics material body to be decorated, said article body to be decorated having internal stresses and having characteristic physical properties, and directing a pulsed laser beam having a pulse energy and a pulse duration into the body of said article, said laser beam being successively focussed by an optical focussing system in different regions within the body of said article, said pulse energy and said pulse duration being selected in dependence upon the desired extent of the decorative features.

Analysis of injection locking in pulsed dye laser systems

Abstract: A pulsed dye laser system with a narrow-band signal injected into the cavity is considered. The injection starts prior to the excitation pulse. It is shown that during a transient period, injection locking can be achieved for a much wider range of parameters than under conventional CW conditions. The analysis is based on a set of coupled rate equations for the population densities and photon fluxes at all wavelengths. These are solved numerically with appropriate initial and boundary conditions. Analytical approximations, which are helpful for understanding the behavior of such systems, are presented. Both straight, two-mirror cavities, and ring laser cavities are discussed. The temporal evolution of the spectral components at all wavelengths is described. The range of tunability in this mode of operation and its dependence on various parameters, such as pulse length, cavity dimensions, and injection intensity are discussed.

A theoretical analysis for gigabit/second pulse code modulation of semiconductor lasers

Abstract: Investigation of the rate equations of a semiconductor laser suggests that bit rates of 3-4 Gbit/s can be achieved. Delay, ringing transients, and charge-storage effects can be removed by adjusting the dc-bias current and the peak and width of the current pulse to values prescribed by simple analytical expressions. Also, simple approximate formulas for the light pulse maximum, width, delay, and integrated values are given.

Gigawatt peak-power pulse generation by injection of a single short pulse in a regenerative amplifier above threshold (RAAT)

Abstract: We propose a very simple technique to extract, in a short pulse with good optical quality, all the laser energy in a pulsed system. The method essentially consists of injecting into a high power laser a short and weak pulse at a moment close to the time when the gain is equal to the losses (laser threshold). Subsequently, the spontaneous emission radiation is dominated at all times by the injected pulse. After multipass amplification, all the energy available in the system is extracted by the injected pulse.In this way, pulses of 2 ns have been obtained from a TEA–CO2 laser of 15 J.

Estimates on the ignition of high‐explosives by laser pulses

Abstract: The response of high‐explosive materials to laser pulses is examined using a one‐dimensional theory. Two distinct regimes of laser flux density I and pulse duration τp are identified, one concerned with a thermal initiation process and the other with an impulse or shock initiation process. For the thermal problem the competition between laser‐induced ablation and thermal runaway is explored, and analytical formulas are found for an ignition time t* and maximum useful laser flux density I*. When I is below I* thermal initiation by the laser pulse is predicted to occur after an exposure time t* (I), but the rapid removal of material by laser‐induced ablation can preclude this type of initiation when I exceeds I*. Values of I* are found to vary from 20 kW/cm2 for PETN to 0.05 kW/cm2 for TNT. The corresponding t* values are about 4 μs for PETN and 0.3 s for TNT. For decreasing flux densities I0 below I*, the ignition time t* increases approximately as I−1.80. For the impulse problem a self‐regulating‐ablation...

Pulse duration modulated signal transducer

Abstract: A transducer for producing a pulse duration modulated signal in accord with the value of a parameter. A reference capacitor-resistance circuit is provided having a predetermined rate of capacitor discharge and a second capacitor-resistance circuit is provided having a capacitor and a resistor, one of which is varied in accordance with the parameter to define a rate of capacitor discharge determined by the parameter. Each of the capacitors is periodically charged in unison to a predetermined voltage. Respective level detectors monitor the capacitor voltage charges and generate respective digital signals when the voltage charge monitored is greater than a predetermined reference below which each capacitor discharges during the time interval between charges. A logic circuit monitors the digital signals and produces a series of pulses having durations determined by the value of the parameter.

Pacer with automatically variable A-V interval

Abstract: PACER WITH AUTOMATICALLY VARIABLE A-V INTERVAL Abstract of the Disclosure An improved atrial synchronous heart pacer includes means for generating an atrio-ventricular (A-V) interval control signal of automatically variable duration, which duration is a function of the sensed atrial heart rate (i.e.P-wave rate). A timing circuit establishes a basic timing interval for the generation of ventricular stimulation pulses, which interval may be modified by the control of the A-V interval signal. The A-V interval control signal preferably comprises the output of a P-wave triggered monostable multivibrator. The time constants of the multivibrator's timing circuits are scaled such that operation within the heart-rate range of 55-150 beats per minute prevents full recovery of the multivibrator following each sensed atrial beat and generation of an A-Voutput pulse, resulting in an A-V output pulse whose duration is a function of the time since the preceding trigger (i.e. rate) By appropriately coupling the variable duration A-Vinterval pulse to the ventricular stimulation pulse timing circuitry, it is possible to adjust the threshold voltage of a relaxation oscillator such that the ventricular stimulation pulse is generated at the end of an A-V delay following a sensed P-wave, the interval of the A-V delay being variable and dependent on the P-wave rate.

Narrow bandwidth dye laser suitable for pumping by a short pulse duration N 2 laser

Abstract: The design criteria and performance characteristics are reported of a tunable, narrow bandwidth dye laser that is suitable for pumping by a short pulse duration high power N(2) laser. The dye laser system is characterized by a relatively short over-all length of 15 cm. Bandwidths of from 0.015 nm to 0.05 nm are obtained along with conversion efficiencies in the neighborhood of 10% using a 4-5 nsec pulse duration N(2) pump. Bandwidths of 0.001 nm are observed with an intracavity etalon in the system. More important, however, it is shown that the conversion efficiency of an intracavity etalon dye laser system can be greatly improved if the temporal distribution of the N(2) pump pulse is adjusted so a single dye cell in a dye laser system is used first as an oscillator and then as an amplifier. Finally, using the above technique of processing the N(2) pump pulse, a 5-nsec N(2) laser is used to pump an intracavity etalon dye laser, which is followed by a large gap external etalon and then by an amplifier; the resulting bandwidth is 0.0005 nm at 480 nm with a conversion efficiency of 4.5%.

Fuel injection control system

Abstract: A fuel injection control system for controlling the timing and duration of an electrical driving pulse to electromagnetic fuel injection valves thereby controlling the timing and duration of fuel injected into combustion chambers of an engine. The control system utilizes a differential circuit to compare an electrical signal representing one engine parameter such as engine rpm with a synchronous sawtooth signal having a slope representing another engine parameter such as back pressure or to compare a first signal level with a sawtooth signal where at least one of the first signal level or the sawtooth slope is related to an engine operating parameter and to thereby generate the required driving pulses. Since the timing and duration of the driving pulses are determined entirely by comparison of electrical analogs of instantaneous engine parameters, the pulse duration is not critically dependent upon electrical circuit parameters such as RC time constants which often vary with age and/or environment.

uv TEA laser with 760‐Torr N2

Abstract: A simple reliable transversely excited atmospheric (TEA) laser operating with moderate repetition rates at 337 nm using commercial‐grade N2 at 1 atm is described. Preliminary results for a range of operating voltages and channel spacings are presented. The laser’s pulse width is about 1 nsec. Best electrical efficiency to date is 0.039% at 8.8 kV. At 21 kV, 355 μJ/pulse is obtained. Above 16.7 kV, the unfocused output will pump a dye solution to superradiance at a distance of 1.5 m. For supply voltages less than 10 kV, a novel configuration for preionization is described.

Electronic kilowatt-hour-meter with error correction

Abstract: An electronic kilowatt-hour meter having internal error correction is disclosed for metering electrical power and energy consumption in a single phase or polyphase electrical system. A comparator compares an analog signal which is proportional to the voltage in the system with a relatively high frequency triangular waveform. The output of the comparator which is a pulse width modulated signal having a pulse duration proportional to the amplitude of the voltage in the system is multiplied by a signal which is proportional to the current in a system. The output of the multiplier is integrated to thereby provide a signal which is proportional to the energy consumed in the system. The output of the integrator is converted to a pulse train having a frequency which is proportional to the amplitude of the output signal of the integrator, and hence is proportional to the kilowatt hours consumed in the electrical system. In order to provide error correction, the phase of the analog signal which is proportional to the voltage in the system is shifted with respect to the phase of the triangular waveform by reversing the connections of these respective signals to the input terminals of the comparator. This is done each time an output pulse is generated by the analog-to-pulse-rate converter. Thus the integrator alternately integrates up and down to thereby correct any offset errors in the system.

Method and apparatus utilizing time-expanded pulse sequences for distance measurement in a radar

Abstract: Pulse sequences from a radar receiver respectively made up of successive start pulses and of successive echo pulses from one or more targets are expanded in time by multiplication with an auxiliary pulse sequence differing slightly in repetition rate from the start pulse sequence. This enables circuits to be used with a lower degree of time resolution that would otherwise be needed, at the cost of proportionally reducing the number of individual measurements of the target distance, a cost which is of no substantial consequence in an anti-collision radar where the closing rates are small compared to the pulse repetition rate. A time-expanded sequence of reference pulses is similarly produced from the oscillator controlling the repetition of the radar pulses and the auxiliary oscillator in order to make the measurements independent of signal propagation times within these circuits. The time-expanded pulses to be evaluated are differentiated and the null passage instant of the differentiated pulses is used to find the maximum amplitude of the pulses and to determine which pulses should be disregarded on the basis of amplitude discrimination. A range gate controlled with reference to the velocity of the vehicle in which the radar is mounted, in combination with certain other factors, is used to exclude interference from irrevalent targets.

Calculations on output pulse shapes, gain pulse profiles, and gain limitation in the CO2 TEA laser

Abstract: An eight‐equation kinetics model for the CO2‐N2‐He‐CO system has been developed to predict the output power pulse shapes from laser oscillators and the small‐signal gain from laser amplifiers. The model takes into account CO2 dissociation into CO, variation in the ambient temperature, as well as the possibility that the lower laser vibrational level is not in equilibrium with the other vibrational levels of the CO2 symmetric stretch mode. Theoretical predictions are compared with experimental data and show good agreement. Calculations have been carried out to determine the factors underlying the limitation of gain at specific input energies.

Laser‐induced shocks and their capability to produce fracture

Abstract: The fracture potential of pulsed laser light is investigated for brittle and ductile fracture. The occurrence of fracture depends on the power density of the beam, the pulse duration, the target thickness, and a number of material parameters, ranging from the plasma state to the solid state of the target material. An essential part of the fracture analysis is the attenuation of the induced shock, which is rapid for short pulses. Using aluminum as a target material it will be shown that fluence levels of 104 J/cm2 are necessary to break targets of centimeter thickness, assuming that the pulse duration is 10−7 sec. It appears that an optimal situation for the achievement of fracture exists, since the peak pressure is inversely proportional to a power of pulse duration, whereas attenuation is proportional to pulse duration.

Method and apparatus for measuring time interval between two pulse signals

Abstract: The time interval between two consecutive pulse signals, as occurring for instance in nondestructive ultrasonic pulse-echo testing, is measured by measuring with a counting frequency the width of the interval start pulse signal and the width of the interval stop pulse signal at respective base lines, and the time interval between both stated signals. Using either two different counting frequencies having a ratio of two to one, or utilizing summing and dividing means the time interval between the start and the stop pulse signals is determined with negligible error.

Double scattering approximation of the atmospheric laser location equation taking polarization effects into account

Abstract: An equation is obtained for the Stokes vector of radiation twice scattered in the backwards direction, assuming that the transmitter and receiver have small angular apertures, that the pulse length is short, and that the receiver and the transmitter are monostatically placed.

Apparatus for providing time reference signals

Abstract: Apparatus for providing an accurate time reference upon a pulse of high frequency electrical signal oscillations comprises a zero crossover detector which includes an amplitude threshold detector, which signals the next positive going zero-crossover of the signal after the threshold detector has operated. An integrating amplifier provides a measure of the integrated pulse amplitude which indicates whether or not the pulse was of adequate amplitude correctly to operate the zero crossover detector.

Pulse duration correction circuit

Abstract: A pulse duration correcting circuit comprising a comparator and a bipolar averaging circuit for correcting the duration of incoming pulses to a desired standard value is disclosed.

Induction motor load monitor and control apparatus

Abstract: Induction motor load conditions are monitored by sensing the slip speed of the motor which is linear over a large operating range including the 100% load condition. Electronic trigger pulses are derived from motor shaft rotation to operate a one-shot waveform generator having a selected signal pulse time duration set at the 100% motor load condition to produce a 3.5 millisecond difference from the time between two trigger pulses. Thus, as the slip speed varies the signal pulse duration varies and thus becomes a monitor of the load condition. Both analog and digital embodiments are described, and utilization devices may be an analog meter display or an alarm circuit triggered by means of an intervening threshold comparison circuit. The monitoring circuits are used to sense variations of speed and indicate on a meter a scale factor of load or horsepower, etc. as related to various drive means without interconnections other than shaft speed detectors.

Synchronizable actively mode-locked Nd:glass laser

Abstract: With the development of an actively mode‐locked Nd:glass laser incorporating dynamic Q control, a single subnanosecond 1.06‐μ pulse has been synchronized to a 1‐ns‐duration 10.6‐μ CO2 laser pulse to within <400 ps.

The seismic wave system from a surface impact

Abstract: A theory presented in an earlier paper (Mooney, 1974) has been used to compute seismic waveforms produced by a surface impact Surface detectors are assumed which measure displacement, velocity, acceleration, or strain in either vertical or horizontal components A physically plausible source waveform is considered which is unidirectional, symmetrical about a peak, and with zero slopes at beginning and end Theoretical waveforms are presented for models simulating projectile, hammer, and weight‐drop impacts onto granite, concrete, and soil The waveforms show small but clear P arrivals, large Rayleigh pulses, and no recognizable S waves P waves are larger on the horizontal sensors, Rayleigh on the vertical The waveforms differ markedly from one detector type to another and show little resemblance to the source waveform Distinctive pulse length and amplitude pulse paramaters are selected Pulse lenths are shown to be relatively insensitive to detector distance, hence conversion factors can be obtained f

Land mine detector with pulse slope, width and amplitude determination channels

Abstract: Circuitry for detecting buried non-metallic and metallic land mines is diosed. A peak detector receives signals from a conventional search head. The output of the peak detector is amplified and this amplified signal is applied to a slope determination channel, to a pulse width determination channel and to a pulse amplitude determination channel. The output pulses from the slope determination channel, the pulse width determination channel and the pulse amplitude determination channel are all applied to different inputs of an AND gate. If pulses are coincidently present on all the inputs of the AND gate, the AND gate provides an output pulse which is applied to a field effect transistor (FET) switch. The FET switch controls the gain of an amplifier such that the gain of the amplifier is measurably increased when the AND gate applies a pulse to the FET switch. When the gain of the amplifier is increased by the FET switch, a signal burst indicating that a mine has been detected is produced on the output of the amplifier. The output from the amplifier is typically coupled to a headset worn by the person conducting the search.

Pulsed uv nitrogen laser: dynamical behavior.

Abstract: Using the time dependent rate equations, the dynamical behavior of a high power pulsed N2 laser radiating at 337.1 nm is derived. The threshold conditions are given. The output peak power and pulse width as a function of length and initial inversion density are shown. The theoretical results derived are compared with experimental data and are found to be in good agreement.

A simple technique for individual picosecond laser pulse duration measurements

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

Reduction of the pulse duration from a Febetron 707

Abstract: This paper describes the use of a deflecting magnetic field to reduce the duration of an electron pulse from a Febetron 707 (normally 90 nsec at the base, Imax=4000 A) to 12 nsec (6–7 nsec half‐width) with Imax =450 A. Under these conditions a dose of about 300 kilorad is delivered in a circular area 2 cm in diameter.

Testing rotary movement-electrical signal transducer system, particularly for vehicle wheel anti-block transducer systems

Abstract: The time duration of output pulses from the transducer, including wave-shaping circuits, if used, is measured and compared with respect to predetermined time limits. Two sequential pulses are measured and stored. If both pulses are shorter than a predetermined time interval, no alarm signal is generated; if the first pulse is longer than a predetermined time interval and the second also longer than a predetermined time interval, an alarm signal generation circuit, otherwise activated by the second, longer signal, is inhibited (since acceleration or deceleration of the wheel is indicated); if, however, the time duration of the second sequential pulse is longer than a predetermined time interval, but the time duration of the preceding pulse is shorter than its time duration threshold value, the malfunction signal is not inhibited, indicative of malfunction, loose contacts, or the like.

Radio-frequency pulse discharge for investigating reactions in electrical discharges

Abstract: A radio-frequency pulse discharge through low-pressure gases has been developed, the pulse duration being variable in the microsecond region. Under the discharge conditions chosen, the degree of ionization in the gas is very low and the major primary processes are molecular excitation and dissociation to radicals. These transient species are detected by their emission spectra for long duration pulses (several hundred mu s), and by their absorption spectra with short duration pulses (down to 10 mu s). For the short duration pulses, the kinetics of radical reactions during and after the pulse can be investigated by the application of kinetic spectroscopy with microsecond time resolution. This pulse discharge technique should make a useful contribution to elucidating radical reaction mechanisms in gaseous electrical discharges which, at present, are not well understood.

Circuit for producing direct voltages from pulses

Abstract: A circuit, for producing direct voltages, for example the tuning voltages for a television or radio receiver, lying within a direct voltage range from pulses fed to an integrating circuit at whose output the direct voltages appear. A plurality of pulses (I) are fed to the integrating circuit, at whose output the direct voltage (UI) appears, within a period duration (T) assigned to the desired direct voltage range, with the period duration (T) being at least of the magnitude T = (Umax - Umin) ·Δτ/ΔUI, where (Umax - Umin) is the desired direct voltage range, Δτ is the shortest time duration of a pulse (I) and ΔUI is the smallest voltage step width associated with the shortest pulse duration Δτ by which two different direct voltages (UI) at least differ from one another.