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Showing papers in "Review of Scientific Instruments in 1977"


Journal ArticleDOI
TL;DR: Four different low‐pass filter design procedures are described, each with its own particular smoothing properties, and the basic concepts of low‐ pass filters are discussed and the uses of the filters are illustrated.
Abstract: With the increasing use of computer‐controlled data acquisition systems which record data in digital form, there has developed a need for techniques which perform a general smoothing process on digitized experimental data. This processing enables the experimentalist to eliminate or greatly reduce the amount of high‐frequency noise in order to obtain as accurate and clean representation of the true phenomenon as is consistent with his measurement accuracies. This filtering or smoothing process should be as simple and efficient (least amount of arithmetic per data sample) as is consistent with the experimental situation. The basic concepts of low‐pass filters are discussed and four different low‐pass filter design procedures are described, each with its own particular smoothing properties. These design procedures give directly the coefficients of a symmetrical weighting sequence having the desired passband width and the desired high‐frequency noise rejection. The uses of the filters are illustrated with examples and the fortran code for implementing each of the design procedures is given in an Appendix.

221 citations


Journal ArticleDOI
TL;DR: In this paper, a position sensitive proportional counter is described which shows some novel features in the method of position encoding compared with previous systems, such as inductance capacity (L•C) line connected to cathode strips, rather than by resistance capacity encoding (high resistance) using the anode wire.
Abstract: A position sensitive proportional counter is described which shows some novel features in the method of position encoding compared with previous systems. The encoding is done by an inductance‐capacity (L‐C) line connected to cathode strips, rather than by resistance‐capacity encoding (high resistance) using the anode wire. The spatial resolution for a counter length of 8 cm is 0.2 mm (which corresponds to 0.01° for the geometry used here). Counting can be at high rates for indefinite periods.

213 citations


Journal ArticleDOI
TL;DR: In this article, a non-destructive technique is described which provides information about the distribution of charges in nonpolar electrets, and the total electret charge and its mean position are obtained directly with this technique.
Abstract: A new nondestructive technique is described which provides information about the distribution of charges in nonpolar electrets. Changes in the equivalent electret voltage are measured during and after the absorption of a short pulse of heat on one side of an otherwise well thermally isolated electret. The total electret charge and its mean position are obtained directly with this technique. The main features of the charge distribution can also be resolved using a deconvolution technique, although it is not yet possible to determine fine details uniquely.

129 citations


Journal ArticleDOI
TL;DR: In this article, the radial distribution of pressure between the diamond anvils for samples of fayalite (Fe2SiO4) was measured using the ruby fluorescence technique.
Abstract: High‐pressure cells, using opposed diamond anvils, have become an increasingly sophisticated tool for high‐pressure research as the high‐pressure environment within th cell becomes more quantitatively established. We have used the ruby fluorescence technique for measuring pressure to obtain the radial distribution of pressure between the diamond anvils for samples of fayalite (Fe2SiO4). Precompacted specimens appeared to be in a conditon of extrusion, limited by the plastic strength of the fayalite aggregate formed. Specimens which were not precompacted were too thin to show this condition.

119 citations


Journal ArticleDOI
TL;DR: In this paper, a single-layer detection system for superconducting magnetic systems is presented. But the sensitivity and range of application of the single layer detection system is evaluated and the theoretical sensitivity considerations are compared with practical measurements.
Abstract: Superconducting magnetic systems permit increasing observing frequencies for NMR experiments. The sensitivity and range of application of the single‐layer detection system is evaluated. High measuring frequencies demand new detection systems because the conventional detection systems lose their good features above about 100 MHz. In this paper a new detection system is presented. The slotted tube resonator (STR) is suitable for all intensities of magnetic field which will be produced in the near future. The characteristic parameters of the STR are calculated and the construction is described in detail. Theoretical sensitivity considerations are compared with practical measurements.

112 citations


Journal ArticleDOI
TL;DR: In this paper, a compilation of yields and cross sections for several nuclear reactions is given, including the measurement of prompt radiation such as γ rays and neutrons from ion-induced reactions.
Abstract: Diagnostic methods pertinent to the probing of intense pulsed ion beams are described. Special emphasis is given to the measurement of delayed radioactivity from nuclear reactions induced in a target by the ions. This nuclear activation analysis provides the most precise, unambiguous means of determining the number of ions per pulse that is presently available. A compilation of yields and cross sections for several nuclear reactions is given. Included among the nuclear techniques is the measurement of prompt radiation such as γ rays and neutrons from ion‐induced reactions. In addition, a scintillator–photodiode detector is described which has proven to be useful for the measurement of time of flight and which may be used to observe the relative pulse shape. Biased ion collectors and difficulties associated with their use are also discussed.

104 citations


Journal ArticleDOI
TL;DR: In this article, a diamond anvil device is described which allows for x-ray diffraction intensity measurements on single crystals up to hydrostatic pressures of about 100 kilobar, which can be used for atomic position parameters and pressures with standard deviations of ± 0.002 and ±0.7 kilobar.
Abstract: A new high‐pressure diamond anvil device is described which allows for x‐ray diffraction intensity measurements on single crystals up to hydrostatic pressures of about 100 kilobar. The present device fits into commercial x‐ray diffractometers such as precession cameras and four‐circle diffractometers. The pressure is determined by measuring the ruby R1‐line shift with a Fabry–Perot interferometer which is coupled to a microscope system. First measurements on Se carried out on a precession camera indicate that atomic position parameters and pressures can be determined with standard deviations of ±0.002 and ±0.7 kilobar.

102 citations


Journal ArticleDOI
TL;DR: In this paper, a fluorescence lifetime apparatus using a mode-locked argon ion laser as excitation source and single photon counting detection is described, and the standard deviations of the Fourier transforms of the deconvolved decay curves are discussed.
Abstract: A fluorescence lifetime apparatus using a mode‐locked argon ion laser as excitation source and single photon counting detection is described. The high repetition rate and intensity of the excitation source allows twofold discrimination in the stop channel, giving excellent time resolution. The data analysis is based on statistical concepts. The standard deviations of the Fourier transforms of the deconvolved decay curves are discussed and the advantages of performing a curve fit in the Fourier space are outlined.

99 citations


Journal ArticleDOI
TL;DR: In this paper, a two-dimensional quadrupole field has been calculated to second order in input position, angle, and energy, and the use of this field as an energy analyzer and as an achromatic deflector is described.
Abstract: The deflecting properties of a two‐dimensional quadrupole field have been calculated to second order in input position, angle, and energy The use of this field as an energy analyzer and as an achromatic deflector are described The calculated dispersion, which is 845% that of of a 127° analyzer of equal angular aberration, has been confirmed by measurement on a deflector designed and built for merging an ion beam with a laser beam This deflector can bend a 3‐kV ion beam of 2‐mm diameter, ±2‐mrad angular spread, and 1‐eV FWHM energy spread by 90° without causing a detectable increase in the diameter or angular spread of the beam

87 citations


Journal ArticleDOI
TL;DR: In this article, a method for photo-acoustic spectroscopy of solids is presented, and some applications of this new technique are discussed, as well as criteria for the light sources, sample chambers, and data acquisition systems.
Abstract: A method is presented by which photo‐acoustic spectroscopy of solids may be performed. Criteria for the light sources, sample chambers, and data acquisition systems are discussed. The dependence of the photo‐acoustic signal on various experimental parameters is explored, and some of the applications of this new technique are discussed.

83 citations


Journal ArticleDOI
TL;DR: In this article, a torsional pendulum allowing the measurement of internal friction as a function of frequency on a wide frequency range is described, and both high and low values of Q−1 may be simply obtained by phase lag measurements, at any frequency between 10−5 and 10 Hz.
Abstract: A new torsional pendulum allowing the measurement of internal friction as a function of frequency on a wide frequency range is described. It is shown that both high and low values of Q−1 may be simply obtained by phase lag measurements, at any frequency between 10−5 and 10 Hz. Some experimental spectra, obtained at different temperatures, are shown to illustrate the accuracy of the method.

Journal ArticleDOI
TL;DR: In this paper, a new method is introduced for correcting the biased statistics of measurements with laser-Doppler velocimeters operating in the individual realization mode and using counters for signal processing.
Abstract: A new method is introduced for correcting the biased statistics of measurements with laser‐Doppler velocimeters operating in the individual realization mode and using counters for signal processing. Two variations of the new correction method are proposed. One is suitable for all uniformly seeded flows; prior to averaging, the individual velocity measurements are weighted with the corresponding residence time of the seed particles in the probe volume. The other variation is suitable for flows with nonuniform seeding in which the average particle separation time is small compared with the time scale of the turbulent fluctuations, and in this method the particle separation time is used to weight the individual measurements. In both cases, a large number of samples is required. An experimental setup for realizing the new biasing correction method is described for each variation. The residence‐time weighting method is applied to mean‐velocity measurements in a uniformly seeded round jet. The results are compared with uncorrected measurements and with results using the McLaughlin–Tiederman correction. The uncorrected results show biasing errors of up to 25%, and the McLaughlin–Tiederman correction works only in the center portion of the jet where the instantaneous flow direction is nearly constant. The McLaughlin–Tiederman correction is restricted conceptually to this flow situation and to uniformly seeded flows. In contrast, the new correction method is not restricted to any particular flow situation. It supplements the new burst‐gating counter system described in a parallel paper to form an especially accurate and versatile LDV‐signal processor.

Journal ArticleDOI
TL;DR: In this paper, a magnetic susceptometer of very high sensitivity and precision has been developed using superconducting technology, which has a volume susceptibility sensitivity (in SI units) of Δκ=±9×10−12, and a precision of 0.0001% of the diamagnetism of a typical substance such as water.
Abstract: A magnetic susceptometer of very high sensitivity and precision has been developed using superconducting technology. Measurements show this instrument has a volume susceptibility sensitivity (in SI units) of Δκ=±9×10−12, and a precision of 0.0001% of the diamagnetism of a typical substance such as water. The capability of measuring magnetic changes during fast reactions in solution has also been demonstrated. System design and measurement techniques are described. The magnitudes and frequency spectra of the noise sources in this type of instrument are analyzed and compared with measured performance.

Journal ArticleDOI
TL;DR: In this article, a transverse quadrupole electric field arrangement is used to deflect the ion beam into and out of the laser beam axis, and a high-resolution 180° electrostatic analyzer is used for photofragment energy analysis.
Abstract: An apparatus has been constructed to provide laser excitation of ion beams in both coaxial and crossed configurations. The coaxial geometry provides very high sensitivity and nearly Doppler‐free wavelength resolution for spectroscopic measurements, and allows the use of the Doppler shift to ’’tune’’ the wavelength. A novel transverse quadrupole electric field arrangement is used to deflect the ion beam into and out of the laser beam axis. The ion beam is highly collimated and a high‐resolution 180° electrostatic analyzer is used for photofragment energy analysis. The apparatus has demonstrated a resolution of better than 10 meV for normal photofragment spectroscopy and 0.001 meV for coaxial beams photofragment spectroscopy using a single‐mode laser. While providing these high resolutions the apparatus has an overall sensitivity several orders of magnitude greater than conventional ones.

Journal ArticleDOI
TL;DR: In this article, a new method of single-photon timing and its application to measuring fast fluorescence decays is discussed, using a mode-locked, pulse-picked argon ion laser as an excitation source.
Abstract: A new method of single‐photon timing and its application to measuring fast fluorescence decays is discussed. The detector‐signal processor, having a transient response of 0.77 nsec FWHM, is designed around an inexpensive, two‐channel sampling oscilloscope. Using a mode‐locked, pulse‐picked argon ion laser as an excitation source, the system performance in measuring fast fluorescence decays was evaluated. An uncertainty for lifetimes measured in the range of 4 nsec to 50 psec was found to be ±6% or ±10 psec, whichever is greater.

Journal ArticleDOI
TL;DR: In this article, a membrane barrier is used to separate longer-lived radioactive isotopes of elements from a mixture of isotopes in passing from one volume to a second by the use of an appropriate intervening barrier so that the shorter-lived isotopes decay before reaching the detector.
Abstract: Longer‐lived radioactive isotopes of elements can be separated from a mixture of isotopes in passing from one volume to a second by the use of an appropriate intervening barrier so that the shorter‐lived isotopes decay before reaching the detector. The separation can most effectively be created by use of a membrane; a purely diffusional barrier is also effective. The techniques are demonstrated in experiments with 3.8‐day 222Rn and 56‐s 220Rn.

Journal ArticleDOI
TL;DR: In this paper, the authors describe and analyze a transmission experiment developed for measuring total scattering cross sections for low-energy poistrons colliding with gases in a region containing a curved, axial magnetic field.
Abstract: We describe and analyze a transmission experiment developed for measuring total scattering cross sections for low‐energy poistrons (0.3–250 eV) colliding with gases in a region containing a curved, axial magnetic field. It is determined that spiralling does not appreciably increase the beam path length through the curved, axial magnetic field in the gas scattering region. An overall test of the experimental apparatus and technique is made by measuring total cross sections for electrons colliding with helium and argon atoms in the energy range from 1.5 to 30 eV, where it is found that the present measurements are within 15% of the most reliable prior measurements.

Journal ArticleDOI
TL;DR: In this paper, the application of a pulsed magnetic field to a Corbino disk of indium antimonide causes an increase in resistance of about 2 orders of magnitude in a time of 5 μsec.
Abstract: Experiments are described in which the application of a pulsed magnetic field to a Corbino disk of indium antimonide causes an increase in resistance of about 2 orders of magnitude in a time of 5 μsec. The use of this element as a switch for the transfer of energy from an inductive energy store is discussed.

Journal ArticleDOI
TL;DR: In this paper, the performance of microchannel plates in the high-gain chevron configuration has been improved by the addition of an interplate voltage VB, and the output electron distribution FWHM decreased from 166% to 97%.
Abstract: Performance of microchannel plates in the high‐gain chevron configuration has been improved by the addition of an interplate voltage VB. For VB=100 V, and positive ion excitation, the output electron distribution FWHM decreased from 166% to 97%. Using a resistive anode encoder (RAE) readout, and 1216‐A uv excitation, we observed a corresponding spatial resolution improvement of 16%.

Journal ArticleDOI
TL;DR: In this article, an NMR probe is described which is capable of use in combined multiple pulse-magic angle spinning experiments for removal of homonuclear dipolar broadening and chemical shift anisotropies in randomly oriented samples.
Abstract: An NMR probe is described which is capable of use in combined multiple pulse–magic angle spinning experiments for removal of homonuclear dipolar broadening and chemical shift anisotropies in randomly oriented samples. Two examples are included to illustrate the utility of the technique.

Journal ArticleDOI
TL;DR: In this article, a modified Mach-Zehnder interferometer employing a linearly polarized scene beam and a circularly polarized reference beam generates signals proportional to the sine and cosine of the phase shift introduced by the plasma.
Abstract: An interferometer has been developed with which it is possible to make accurate plasma density measurements in the presence of density gradients. A modified Mach–Zehnder interferometer employing a linearly polarized scene beam and a circularly polarized reference beam generates signals proportional to the sine and cosine of the phase shift introduced by the plasma. The differential sensitivity of the phase shift measurements is independent of the instantaneous phase angle, and the phase angle may be unambiguously followed through multifringe excursions of the interferometer. The phase shift measurement is also independent of fringe contrast fluctuations caused by the refractive bending of the scene beam by the plasma.

Journal ArticleDOI
TL;DR: In this article, the authors show that virtually rigid rotation gives way to secondary flows around the drop as spin velocity is decreased, which are attributed to a gravity-induced, internal, hydrodynamic shear layer, to a misalignment-induced Taylor column, to externally excited inertial oscillations, and to mass transfer effects.
Abstract: Depending on operating speed, gyrostatic equilibrium is not approached closely enough for reliable tension measurement. Flow visualization experiments show that virtually rigid rotation gives way to secondary flows around the drop as spin velocity is decreased. Flows are attributable to a gravity‐induced, internal, hydrodynamic shear layer, to a misalignment‐induced Taylor column, to externally excited inertial oscillations, and to mass transfer effects. Bizarre shapes of ultralow tension drops are probably caused by these effects, which should be avoided by design or operation of the instrument. Relevant criteria are given.

Journal ArticleDOI
TL;DR: In this article, an ion accelerator has been used to evaluate three types of Faraday cups commonly used to measure plasma expansion characteristics in laser-produced plasmas, and one type of cup was found to have very low secondary emission and is very suitable for absolute measurement of ion numbers and energies.
Abstract: An ion accelerator has been used to evaluate three types of Faraday cups commonly used to measure plasma expansion characteristics in laser‐produced plasmas. One type of cup was found to have very low secondary emission and is very suitable for absolute measurement of ion numbers and energies.

Journal ArticleDOI
TL;DR: Several different axisymmetric aperture shapes have been studied, experimentally and theoretically, for use in the plasma electrode employed in extracting ions from a plasma, and the minimum half-width-half-maximum divergence obtained for the former class was 0.57° at a beam energy of 27 kV, as compared to 1° obtained for a conventional cylindrical bore aperture as mentioned in this paper.
Abstract: Several different axisymmetric aperture shapes have been studied, experimentally and theoretically, for use in the plasma electrode employed in extracting ions from a plasma. Compared to a cylindrical bore aperture, a class of shapes opening away from the source plasma resulted in smaller beam divergence (due to reduced aberration fields), while a class opening toward the source plasma resulted in higher beam power density at optimum divergence. The minimum half‐width‐half‐maximum divergence obtained for the former class was 0.57° at a beam energy of 27 kV, as compared to 1° obtained for a conventional cylindrical bore aperture.

Journal ArticleDOI
TL;DR: In this article, a simple analog subtraction circuit for measuring the Seebeck coefficient of semiconductors as a function of temperature is described, and an X-Y plotter is the only electronics needed to acquire the data.
Abstract: A simple, inexpensive analog subtraction circuit for measuring the Seebeck coefficient of semiconductors as a function of temperature is described. The circuit and an X‐Y plotter are the only electronics needed to acquire the data. An accuracy of better than 1% can be achieved.

Journal ArticleDOI
TL;DR: In this paper, a two-dimensional, frame transfer, charge-coupled device (CCD), modified to allow direct access of x rays to the sensitive silicon, was used to detect patterns of soft x rays (1-8 keV).
Abstract: To determine the feasibility of actively recovering data from x‐ray imaging instruments used in the laser fusion program of Lawrence Livermore Laboratory, we have used a commercial, silicon video sensor to detect patterns of soft x rays (1–8 keV). The sensor is a two‐dimensional, frame transfer, charge‐coupled device (CCD), modified to allow direct access of x rays to the sensitive silicon. We discuss the x‐ray sensitivity, linearity, and dynamic range of the CCD.

Journal ArticleDOI
TL;DR: In this paper, the ac calorimetry technique has been adapted for use at hydrostatic gas pressures up to 3 kilobar, and the theory of this method has been extended to take into account high gas densities and low sample thermal conductivities.
Abstract: The ac calorimetry technique has been adapted for use at hydrostatic gas pressures up to 3 kilobar. The theory of this method has been extended to take into account high gas densities and low sample thermal conductivities, and the resulting equations have been tested on samples of Invar and ammonium chloride. The method is especially attractive for studying heat capacity variations in samples that undergo second‐ or higher order phase transitions at high pressures.

Journal ArticleDOI
TL;DR: In this paper, an interferometric system for continuously measuring specimen velocity is described, where the Doppler shift of a laser beam reflected from the free surface is transformed into a variation of the diameter of Fabry-Perot interference rings, and the evolution of diameter versus time is continuously recorded by a streak camera.
Abstract: An interferometric system for continuously measuring specimen velocity is described. The Doppler shift of a laser beam reflected from the specimen’s free surface is transformed into a variation of the diameter of Fabry–Perot interference rings, and the evolution of the diameter versus time is continuously recorded by a streak camera. Two examples of the use of this system for study of shock waves are given to show the accuracy of this device.

Journal ArticleDOI
TL;DR: In this article, a 15 cm grid diameter version of the PIGatron ion source has been used for high power neutral beam injectors for heating plasmas in CTR devices.
Abstract: The 10 cm (grid diameter) duoPIGatron ion source produces pulsed hydrogen ion beams of 10–15 A beam current in the 20–40 keV energy range for a duration of a few tenths of a second. To fulfill the requirement of the next generation of high‐power neutral beam injectors for heating plasmas in CTR devices, this source has been enlarged to a version 15 cm in grid diameter. In addition, by utilizing a magnetic multipole line cusp field confinement method, the plasma created is characterized over the 15 cm grid diameter by a noise level within ±10% and spatial density variations within ±5% at a density on the order of 1012 cm−3. This larger source has operated reliably and produced a beam current exceeding 30 A of hydrogen at 27 keV. Initial operation of a 20 cm version of this source employing line cusp confinement has produced an extraction current of 60 A at 33 keV.

Journal ArticleDOI
TL;DR: In this article, an instrument employing a laser Doppler velocimeter and a microphone to measure the phase lag of the motion of aerosol particulates relative to the motion within an acoustic field is described.
Abstract: An instrument employing a laser Doppler velocimeter and a microphone to measure the phase lag of the motion of aerosol particulates relative to the motion of the fluid medium within an acoustic field is described. The relaxation times and aerodynamic diameters of the particles or droplets are determined in real time from the measured values of phase lag; thus, the size analysis is independent of the electrostatic charges and refractive indices of the particulates. The instrument is suitable for analyzing the aerodynamic size spectrum of atmospheric particulate pollutants with aerodynamic diameters ranging from 0.1 to 10.0 μm.