Pulse Shape Measurements Research Articles

Pulse stretching and spectroscopy of subnanosecond optical pulses using a Fabry-Perot interferometer

A Fabry-Perot interferometer has been used to produce optical pulses of variable width from a short gaussian input pulse. Pulse stretching of two to five or more times the original pulse width is possible provided a longer tail on the output pulse is acceptable. Calculations and measurements of pulse shape and interferometer finesse are presented, along with a discussion of short-pulse spectroscopy using a Fabry-Perot interferometer.

Measurements of picosecond laser pulses from mode-locked Nd:YAG laser

This paper deals with measurements of picosecond laser pulse parameters such as temporal and spatial profile, and power. Pulseshape measurements were conducted by using the combined streak camera and optical multichannel analyzer system. The precision of measurements are discussed.

Multiple interaction processes in Ge(Li) detector pulse formation

The contribution of multiple interaction processes to pulse shape generation in coaxial Ge(Li) detectors is calculated using a Monte Carlo technique. The results are compared with point interaction calculations and experimental pulse shape measurements. Multiple interaction processes are found to be significant, and their inclusion leads to good agreement with experimental information.

Studies on the Coulter Counter Part II. Investigations into the Effect of Flow Direction and Angle of Entry of a Particle on both Particle Volume and Pulse Shape

In this paper the effect of the geometry and alignment of the flow straightener in the IITRI modification to the Coulter Counter are reported. For particle size analysis, the diameter of the flow straightener hole is shown to have no significant effect on the size distribution for diameters as low as 250 μm, but the alignment is highly significant when cylindrical orifices are used. The channel number of the mode and the broadness of the size distribution are shown to increase with increasing angle, the effect being more significant with a corresponding increase in current. When the size distribution measurement is perfomred using a constant total count for each angular measurement, the height of the mode decreases linearly with angle, the particles moving to higher voltage channels. This means that particles entering a sharp-edged orifice at wide angles are detected as particles of larger size. Pulse shape measurements confirmed the presence of sharp voltage spikes superimposed on conventional particle pulses from these particles, suggesting that pulse distortion had occurred. With the contoured orifice, there is no change in either the mode position or the breadth of the distribution with angle, and the height of the mode does not decrease. Pulse shape observations also show the absence of sharp spiked pulses from particles entering a contoured orifice, irrespective of the angle. In consequence, it is concluded that the distortion in the pulse shape and the resulting error in sizing is an orifice edge effect, and for the most accurate size analysis the use of a flow-directional collar aligned at 0° rotation to a contoured orifice is recommended. As a final section to the paper, the IITRI work is related to other recent work in the field, and the significance of this total work to particle size analysis is discussed.

Improved performance of an electrically initiated HF laser

Some methods for improving the efficiency of electrically initiated HF lasers are discussed. Measurement of the laser pulse shape produced by 30-ns discharges in SF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> :C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> at several mixtures and pressures is reported. These pulse shapes are compared to the laser and current pulses produced by a two-stage Marx bank that gives laser pulses of 1.4 J with 3.1-percent electrical efficiency from an active volume of 0.331. A second bank is described, which gives pulses up to 3.5 J with 1.8-percent efficiency, with a peak power of 35 MW.

Photomultipliers output pulse shape

The shape of photomultiplier output pulses has been studied for two operating conditions: single-electron response (SER), and the case when the photomultiplier is associated with a scintillator. An accurate measurement of the SER mean pulse shape has been performed. The comparison of output pulse shapes when the PM is placed in a setup that is typical for most nuclear physics experiments showed a dependence of the pulse shape on the pulse amplitude.

Measurement of picosecond pulse shape by three-photon fluorescence

Measurement of picosecond pulse shape by three-photon fluorescence

Scintillation pulse shape measurement with the linear gate and integrator (2144)

A system is described for the determination of scintillation pulse shapes with decay times in the range 10 ns to 100 μs. The current pulse from a photomultiplier tube is gated by electronic circuitry and a summing system has been devised so that the amplitude of pulse at different times may be derived derictly from digital voltmeter readings. A detailed comparison is made with the more generally used single photon time interval analysis method. With slight modification this system could be employed for the measurement of current pulses from other sources such a semiconductor radiation detectors.

Linear Polarization and Spectrum of PSR 0833?45 and the Effects of Scattering

Linear polarization characteristics as well as pulse shape have been measured at Parkes for the average of many pulses from PSR 0833?45 at several frequencies between 300 and 1410 MHz. These confirm a previous conclusion, which was based on pulse shape measurements alone, that the change of pulse character with decreasing frequency can be explained in terms of interstellar scattering. The inferred effect of the scattering medium is explained on the assumption that it comprises many layers of weak uncorrelated density inhomogeneities. Also, some evidence is found for a weak "precursor" pulse, and the possible implications are discussed.

Averaged Pulse-Shape Measurements of Radar Sea Return at near-Vertical Incidence

Some average pulse-shape measurements of radar sea returns at near-vertical incidence are presented. The measurements were made at a 75-cm wavelength, from light aircrafts flying at altitudes of 2 to 2.3 km over various water surfaces. Greater knowledge of the return shapes could help the design of high-accuracy radar altimeters. It could also contribute to several areas of remote sensing. Both specular and scattered reflections were observed in all the returns, with clear distinction between the two components. Dominance by either the specular or the scattered component was observed, the first one being the more frequent. Real-time averaging was obtained by utilizing a sampling technique. This enabled a reduction of the system bandwidth to several hertz, allowing the use of low peak-power RF pulses (1 W), and low-speed chart recorders. Twenty-one recorded average returns are given, along with an interpretation of the recordings and a description of the measuring system.

Pulse-shape measurements for the oak ridge electron linear accelerator with gamma-ray detection techniques

A study of the pulse-shape characteristics of the Oak Ridge Electron Linear Accelerator was carried out because the resolution of neutron cross section and neutron spectra measurements are directly dependent upon this pulse shape. Gamma-ray detection with techniques commonly used in the neutron time-of-flight experiments was used in the study because of the fidelity with which the pulse shape could be measured.

Calibration of ultrasonic beams for bio-medical applications

The important parameters of ultrasonic beams used in current medical applications are briefly surveyed. Two designs of radiation balance are described which are suitable for the absolute measurement of acoustic power in diagnostic and therapeutic type beams respectively. The sensitivities of the two instruments are of the order of 0.3 mW and 0.05 w. A description is also given of the construction and use of a small piezoelectric hydrophone probe which is suitable for measurements of beam shape and pulse shapes (spatial and temporal distribution of acoustic energy). The two types of measurement provide complementary information and it is considered that their use in combination provides a good practical approach to the problem of ultrasonic beam calibration.

Scintillation Pulse Shapes of Anthracene Single Crystals in Nanosecond Region. I. Initial Spikes in α-Scintillation Pulse

The accurate measurement of scintillation pulse shapes of anthracene single crystals has been performed by a newly constructed device with the time resolution of nanosecond by means of the sampling method under the pulse height selection and the accumulation of pulse shapes. The distinctive differences between the pulse shapes of luminescence excited by α-, β-particles, γ-ray and UV light pulse were observed. In case of excitation of α-particle, there appeared a characteristic peak which seemed to be superposed on a scintillation peak excited by β- or γ-ray. The dependence of this faster component, that is, the initial spike on the values of d E /d x of α-particle in anthracene crystal has been studied.

Neutron moderator assemblies for pulsed thermal neutron time-of-flight experiments

Time-of-flight experiments using pulsed sources of fast neutrons (either pulsed fast reactors or linacs with suitable targets) require moderators to give thermal neutron pulses. The design of suitable moderators involves a compromise between maximum neutron intensity and good time resolution. The optimum moderator assembly for a particular experiment will depend on the neutron wavelength range of interest, the time and spatial resolutions required etc. This paper describes the measurement of neutron yields and pulse shapes for plane polythene slabs. Work has also been done on the use of homogeneous and heterogeneous poisoning to try to increase the neutron intensity whilst retaining a short duration pulse. The consequences of time focusing by using angled moderators have also been studied. Some comments are included on the theory and use of “figures of merit” for moderators, and the optimum geometries are discussed for three major classes of experiments.

Photomultiplier Reception of Satellite Beacon Flashes

Experiments have been performed on the electrooptical detection of flashes from satellite-borne beacons for the purposes of establishing the time of flash at the observing site, measurement of received pulse shape, and relative measurement of received energy. Initial observations have been made of the beacons carried by the geodetic satellite GEOS-B. Time of flash has been obtained to a precision of 0.1 msec. Pulse shape and energy measurements have been made for various slant ranges and at various voltages on the photomultiplier circuits. Continued testing is directed toward microsecond timing of flash reception.

Frequency Dependent Pulse Widths for CP 1133

MEASUREMENTS of average pulse shape made at the Arecibo Ionospheric Observatory have shown that the duration of an average pulse from the pulsar CP 1133 increases progressively with decreasing radio frequency. The effect results in a pulse duration at 40 MHz roughly twice that at 430 MHz. We give here the observational results for CP 1133. Other Arecibo observations show that CP 0834 behaves in a similar way, and the effect may well be common to all pulsars.

Radio Observations of Five Pulsars

WE have reported1 measurements of the characteristic pulse shapes, dispersions and spectra of the four pulsars, CP 0834, CP 0950, CP 1133 and CP 1919, discovered by Dr Hewish and his group at Cambridge2. The 250 foot telescope at Jodrell Bank has been used to observe the five new pulsars CP 0328, CP 0808, HP 1506, PSR 1749–28 and PSR 2045–16 reported by Cole and Pilkington3, Huguenin et al.4, and Turtle and Vaughan5. We describe here measurements of the positions, periods, dispersions and pulse shapes obtained at frequencies of 151 MHz, 408 MHz and 610 MHz. The observational techniques used have been described before6.

A study of proportional counter mechanisms

In order to examine the operation of proportional counters, as used for 4πß detectors, observations were made on both the electrical pulse and that induced in a photomultiplier which viewed the discharge directly. Measurements on the relative gas gain, the shape of the photon pulse and the electron transit time are described for methane and 90% argon plus 10% methane gas fillings. At high gas amplifications a marked deviation from the expected exponential gas gain curve is ascribed to self induced space charge effects while the general space charge effect is evident at very high counting rates. The optical radiation from the Townsend avalanche is found to give rise to a train of satellite pulses due to the photoelectric effect at the cathode. The photon pulse shape measurements suggest that the development time of a single Townsend avalanche is less than 10 nsec in methane but varies between about 20 to 50 nsec in argon-methane. The mean life time of the excited states associated with the optical radiation is of the order 3 nsec in both gas fillings although in argon-methane there appears to be an additional component having a considerably longer life time. The spacing between successive satellite pulses is a measure of the electron transit time across the counter and under certain conditions in argon-methane this transit time is found to increase as the voltage across the counter is increased.