Range Of Pulse Widths Research Articles

Energy balance in pulse discharges in inert gases

The total evolution of heat in the bulb, electrodes, and leads was determined for pulse discharges in Xe, Kr, Ar, and Ne using a water calorimeter. The investigation was carried out in the specific power range 0.06–1.0 MW/cm2 for discharges lasting from 70 to 2000 μsec. In all the gases there was a wide range of pulse durations (at least from 250 to 2000 μsec) in which the specific power input was a reliable characteristic of the energy balance.

Short-pulse multiline and multiband energy extraction in high-pressure CO<inf>2</inf>-laser amplifiers

The ability of a nanosecond or shorter CO 2 -laser pulse consisting of a single vibrational-rotational transition to extract energy from an atmospheric-pressure CO 2 amplifier is limited owing to the finite rotational thermalization time in CO 2 and the larger number of rotational states which share the stored energy. Theoretical studies are reported which indicate that utilizing an incident pulse consisting of several vibrational-rotational lines within the 10.6-μ band substantial improvements can be obtained over single-line extraction. Even more dramatic improvements are possible if the pulse contains vibrational-rotational transitions at both the 10.6- and 9.6-μ bands. Quantitative energy-extraction results are presented for an input Gaussian pulse consisting of 1-5 10.6-\mu transitions, and for a pulse containing one line at 9.6 μ and one at 10.6 μ, traversing a 1-m amplifier, for a wide range of input energies, pulsewidths, and gas pressures. Possibilities of using multiband techniques for pulse shaping are also discussed.

Avalanche Ionization and the Limiting Diameter of Filaments Induced by Light Pulses in Transparent Media

A limiting intensity is shown to exist for light propagation in transparent liquids and solids. In pure bulk materials it is determined by avalanche ionization over a wide range of pulse durations, wavelengths, and band gaps. The ionization rate per unit time is deduced from the thickness dependence of the dc breakdown. The negative real part of the index of refraction of the carriers stabilizes the size of self-focused filaments.

An electronic wattmeter for nonsinusoidal low power factor power measurements

The development of an electronic wattmeter for use in power circuits with very low power factors and nonsinusoidal waveforms is reported. The wattmeter is constructed of commercially available components which include a high-accuracy electronic multiplier and appropriate amplifying, averaging, and compensating circuitry. It is a portable laboratory instrument with provisions for direct reading of both instantaneous and average power. A thermal standard has been used to calibrate the wattmeter over a wide range of current pulse magnitudes and pulsewidths and at power factors down to 0.01. Several applications of power measurements in typical solid-state power controller circuits are discussed.

Limit imposed by atmospheric dispersion on the minimum laser pulsewidth that can be transmitted undistorted

The dispersive effects of the atmosphere due to index of retraction variations with the frequency will permit one to transmit vertically through the whole atmosphere under clear weather conditions pulses having widths ranging from about 40 ps to about 1.0 ps with distortions varying from correspondingly small to large over this range of pulsewidths. However, even for a pulsewidth of 1.3 ps the half-voltage pulsewidth is only increased by about 10 percent.

Relation between absolute thresholdand duration-of-tone pulses in the bottlenosed porpoise.

Results of a study of absolute threshold and duration-of-tone pulses in the bottlenosed porpoise indicated that the animal, in detecting pure-tone stimuli, integrated the acoustic energy in essentially the same way as humans. Pure-tone thresholds were determined at 0.25, 1, 4, 20, 45, and 100 kHz for a wide range of pulse durations. Least-squares fits to the data yielded time constants that were in general agreement with those obtained in experiments with humans. The data for very short pulses at 20 and 40 kHz indicated the presence of critical-frequency bands, for which rough estimates were obtained.

A linear gate and integrator

A linear gate, one of whose outputs is proportional to the time integral of the input pulse, is described. The circuit is direct coupled throughout in order to eliminate the effects of count rate. The gate and analogue input circuit have a rise-time of about 2 nsec and can be used over a very wide range of input pulse widths.

Univibrator as a time base element in a medium fast coincidence circuit

In a medium fast coincidence circuit (resolution time variable from 100 ns-11 μs) a univibrator is used as timing element (delay and determination of resolution time). The univibrator is designed to have a constant but adjustable output pulse width. The specifications of the output pulses are: Supply voltage dependence: 0.5% pulse width variation/10% supply voltage variation. Temperature coefficient: 100 ppm pulse width variation/°C (measured in a temperature range 25–35°C). Pulse width range: continuously adjustable by a factor of 11; coarse over several decades if desired. Minimum pulse width: 50 ns. Linearity of pulse width adjustment: better than 0.3% accuracy of pulse width range adjustment, 1% of pulse width. Deadtime: less than 200 ns in the range of 1–11 μs. Rise-time of the output pulse: 15 ns. Theoretical considerations and practical measurements are in good accordance. The univibrator can be used for many applications in nuclear instruments. The described circuits are completely transistorized.

Accelerator Pulsed Fast Assembly

An accelerator pulsed fast reactor has been constructed and placed in operation at General Atomic. A 20 megawatt L-band electron accelerator drives a super-critical U-235 metal reactor. This device has the unique characteristic that peak power and pulse width can be varied independently by adjusting various accelerator and reactor parameters. Pulse widths range from less than 0.1 μsec to 5 μsec and the fast fluxes attainable are in excess of 5 Χ 1015 n/cm2/sec at the surface and about an order of magnitude higher internally. Further improvements are planned to increase these yields by an order of magnitude. In addition to single pulse operation, these devices can be repetitively pulsed up to several pulses per second to provide high intensity fast or thermal fluxes if some means of cooling the fuel is provided.

Detection of Tone Pulse of Various Durations in Noise of Various Bandwidths

Noise-masked hearing-threshold measurements for tone pulses of 800 cps over a wide range of pulse durations and bandwidths of the masking noise show that the slope of the threshold versus bandwidth curve of 3 dB per factor 2 in bandwidth, as predicted by Fletcher [Rev. Mod. Phys. 12, 47 (1940)] occurs only for bandwidths of 10 cps and smaller. This is due to a criterion change for bandwidths between 10 and 100 cps. In this range of bandwidths, the average slope is about half of that expected by Fletcher. In the present experiments, the slope of the threshold versus pulse-duration curve turned out to be 3 dB per factor 2 in time when white-masking noise is used, and often even less when bands of masking noise are used. These measurements indicate the existence of a mechanism that adjusts the width of the critical band in such a way that detection of the stimulus occurs more efficiently than it would in the case of a fixed width of the critical band.

Development of a 10-kw 4-mm magnetron

Under a development contract between Bomac Laboratories, Inc. and the Signal Corps Electronic Laboratories, the BL-221, a 4.3 mm packaged magnetron with pulsed power in excess of 10 kw was designed and fabricated. This tube has been successfully operated at duty cycles up to .0005 over a range of pulse widths from .03 to .3 microseconds, and at pulse repetition rates from 1670 to 16,700 c.p.s. This paper discusses the design in moderate detail, the techniques employed in its fabrication, and test results of typical samples. In achieving this accomplishment, the state of the art has been extended in a number of directions simultaneously. The BL-221 development resulted in a more rugged tube, lighter weight, smaller overall size, and higher power output than any 4 mm magnetron previously produced in this country. This development concentrated on certain inherently desirable features of tube construction which tend to make it more shock and vibration resistant, and contribute to longer life, higher power, and more compactness. Features of construction include: (1) Replacement of all glass members with ceramics, except for the output window. (2) Design of a compact E magnet and improved magnetic circuit. (3) Use of Phillips type emitter. (4) Application of internal getters. (5) Ingenious method of electrical centering of cathode during operation.

An Instantaneous Peak Voltmeter

The article presents an analysis of the function and limitations of the simple diode condenser charging peak voltmeter circuit. It also describes a new circuit which makes possible instantaneous measurements of amplitudes of random pulses over a wide range of pulse width and frequency and regardless of the amplitude of the previous pulse. The circuit presented is used to measure the peak voltage of square pulses from 0.1 to 20 msec duration at frequencies as low as 0.2 sec, used for stimulation of nervous tissues.