Showing papers in "Review of Scientific Instruments in 1956"
TL;DR: Scitation as mentioned in this paper is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies (AIP member societies) from the 1990s and 2000s.
Abstract: Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies
310 citations
260 citations
TL;DR: In this paper, a high sensitivity mass spectrometer for noble gas analysis is described, which is of considerable advantage in analyzing argon and lighter rare gases, such as rare gases.
Abstract: A high‐sensitivity mass spectrometer for noble gas analysis is described in detail. Ultra‐high vacuum techniques have been used throughout so that small rare gas samples can be closed off within the spectrometer envelope and analyzed statically. This procedure is of considerable advantage in analyzing argon and lighter rare gases. The background spectrum when the spectrometer pressure is 5×1010 mm Hg is described. Sensitivity data are presented. The detectability of the instrument for xenon atoms (any isotope) is 0.5×106 atoms; for A36, the detectability is 14×106 atoms.
186 citations
TL;DR: In this paper, the operation of various high-field magnets in the pulse range 50 to 10, 000 μsec is discussed, and some techniques for associated solid state experiments are given.
Abstract: Experiments involving pulsed magnetic fields of a half‐megagauss and more are shown to be practical. Some basic concepts are developed regarding the construction of impact resistant solenoids and the selection of the appropriate power supply. Operation of various high‐field magnets in the pulse range 50 to 10 000 μsec is discussed, and some techniques for associated solid state experiments are given. Magnetoresistance measurements up to 600 000 gauss have been made for germanium. Operation of a 175 000 gauss Helmholtz‐type magnet for nuclear track plate work with the 95‐Mev Harvard synchrocyclotron is described.
137 citations
TL;DR: A broad range magnetic spectrograph for precise measurement of the energies and intensities of charged particles from nuclear reactions is described in this paper, where a uniform magnetic field with a circular boundary focuses particles from a source outside the field along a hyperbolic focal surface.
Abstract: A broad‐range magnetic spectrograph for precise measurement of the energies and intensities of charged particles from nuclear reactions is described. A uniform magnetic field with a circular boundary focuses particles from a source outside the field along a hyperbolic focal surface. Particles with energies varying by as much as a factor of 2.5 may be simultaneously recorded on nuclear‐track plates. Under routine operating conditions, an energy resolution of better than 1000 is obtained over the length of the focal surface. The design, construction, testing, and operation of the spectrograph are described, and plots of dispersion, magnification, aberration, and calibration are given.
130 citations
TL;DR: In this article, a study of the response of the sodium iodide scintillation counter to photons in the energy range from 10 to 1500 kev has shown the presence of a significant nonlinearity.
Abstract: A study of the response of the sodium iodide scintillation counter to photons in the energy range from 10 to 1500 kev has shown the presence of a significant nonlinearity. Response curves are given for a number of crystals of different dimensions.
101 citations
TL;DR: In this paper, a closed-circuit system consisting of two chambers and utilizing a gas-dilution principle was proposed to measure the volume of the whole human body using the subject in one chamber and helium in another.
Abstract: A means for measuring the density or the volume of the whole body is essential to reliable estimates of fat in humans. Although Archimedes' principle has often been employed to determine density directly, a method that is less demanding on the subject has been developed for measuring body volume. The apparatus is a closed‐circuit system consisting of two chambers and utilizing a gas‐dilution principle. With the subject in one chamber and helium in the other, the gases in the system are mixed. The helium concentration, measured by thermal conductivity, is related to the tissue volume displacement of the subject. The standard deviation in volume determination is estimated as ±0.12 liter.
99 citations
TL;DR: Two Faraday-cup electron collectors have been developed which are capable of measuring the absolute integrated beam current of the Stanford linear accelerators to better than 0.5% at electron energies ranging from 4 to 300 Mev as mentioned in this paper.
Abstract: Two Faraday‐cup electron collectors have been developed which are capable of measuring the absolute integrated beam current of the Stanford linear accelerators to better than 0.5% at electron energies ranging from 4 to 300 Mev. A description of these instruments is given and complete design criteria are offered which allow the extension of the range to Bev energies.
99 citations
TL;DR: The vibrating-coil magnetometer as mentioned in this paper measures the magnetization of a small sample of magnetic material placed in an external magnetizing field by converting the dipole field of the sample into an ac electrical signal.
Abstract: The vibrating‐coil magnetometer measures the magnetization of a small sample of magnetic material placed in an external magnetizing field by converting the dipole field of the sample into an ac electrical signal. To allow space for temperature‐ or pressure‐generating apparatus around the sample, the measurement is made at distances up to 2 cm from the sample. The measurement is continuous and can be recorded on a chart as a function of time, temperature, crystallographic orientation, or magnetizing field. The present stable sensitivity is such as to provide one percent accuracy for a dipole moment of 8.56×10−4 amp‐m2 (the saturation moment at room temperature of a nickel sphere 1.5 mm in diameter).
85 citations
TL;DR: In this paper, a crystal spectrometer for neutron measurements has been developed which has relatively good resolution over an effective energy range from 0.08 to >20 ev. The figure of merit which has been obtained is 0.171 μsec/m with Be (1231) and 0.127 μsec /m with be (2242) monochromator.
Abstract: A crystal spectrometer for neutron measurements has been developed which has relatively good resolution over an effective energy range from 0.08 to >20 ev. The figure of merit which has been obtained is 0.171 μsec/m with Be (1231) and 0.127 μsec/m with Be (2242) monochromator. The good resolution is made possible by a multiple channel collimator (Soller slit) of novel design. The collimator is described in detail and the resolution function for the system is derived and discussed. It is shown that the resolution of the system is essentially independent of the mosaic spread of the crystal. Experimental results are presented which illustrate the performance of the instrument.
74 citations
TL;DR: In this paper, the more important properties of end-window Geiger counters, side-window proportional counters, and NaI(Tl) scintillation counters are reviewed and their performance in the 5 to 50 kvp x-ray analysis region is compared.
Abstract: The more important properties of end‐window Geiger counters, side‐window proportional counters, and NaI(Tl) scintillation counters are reviewed and their performance in the 5 to 50 kvp x‐ray analysis region is compared. Proportional and scintillation counters have resolving times of the order of 0.25 μsec and virtually eliminate the nonlinearity limitation of the Geiger counter. They produce pulse amplitudes proportional to the energy of the x‐ray quanta, and thus simple pulse height discrimination techniques can be used to obtain greatly improved peak‐to‐background ratios with little loss of intensity of the characteristic x‐rays. They are as reliable and nearly as easy to use as Geiger counters. The electronic discrimination method is described and explained with some practical applications. For a given experimental arrangement, the measured intensity is determined by the quantum counting efficiency of the counter tube, and the peak‐to‐background ratio is determined by the spectral response of the detector‐discriminator combination.
TL;DR: An iterative numerical integration procedure has been developed to correct both beta spectra and differential beta-gamma directional correlations for the effects of finite instrument energy resolution including the effect of backscattering from a scintillation detector.
Abstract: An iterative numerical integration procedure has been developed to correct both beta spectra and differential beta‐gamma directional correlations for the effects of finite instrument energy resolution including the effect of backscattering from a scintillation detector.The method has been tested and found to reproduce the true spectral shape in the cases of Re186, Au198, Tl204, and to allow separation of composite beta spectra as in the case of W187. Application of the method is limited to maximum beta energies exceeding 200 kev.
TL;DR: A pulsed, cold-cathode ion source has been developed to produce multiply charged ions for use in a linear accelerator as mentioned in this paper, and mass spectra of the various ionization states produced by the arc are presented.
Abstract: A pulsed, cold‐cathode ion source has been developed to produce multiply charged ions for use in a linear accelerator. Milliampere currents of such ions as He42+, C122+, N143+, O163+, Ne203+, and smaller currents of S325+ and A406+ have been produced in focused beams.Mass spectra of the various ionization states produced by the arc are presented. Constructional details of the source and the associated electronic equipment are given, and operating characteristics of the source and ion extraction are discussed.
TL;DR: In this paper, a circuit was designed to measure the time elapsed between a fast rising signal from a nuclear detector and the next pulse from a steady source of pulses which are evenly spaced in time and occur at an rf rate.
Abstract: A circuit is described which is designed to measure the time elapsed between a fast‐rising signal from a nuclear detector and the next pulse from a steady source of pulses which are evenly spaced in time and occur at an rf rate. This circuit has been found useful for measuring time intervals in the millimicrosecond range as part of a system of fast‐neutron spectrometry which utilizes a pulsed source of neutrons. The conversion of time to pulse height is linear for time intervals from 10 mμsec to a time which is 20 mμsec shorter than the interval between the rf pulses. The resolution obtainable depends on the characteristics of the detector. The precision of time measurement is about 1 mμsec.
TL;DR: In this article, a method for measuring the spectrum of fast neutrons with a series of foil detectors is described, which consists of Au and Au plus Cd for determining thermal flux, Pu239 shielded with B10 for determining the total fast flux, Np237 for determining total flux above 075 Mev, U238 for determining high intensity bursts of neutrons, and S32 for calculating the tissue dose from the measured spectrum.
Abstract: A method is described for measuring the spectrum of fast neutrons with a series of foil detectors The detectors consist of Au and Au plus Cd for determining the thermal flux, Pu239 shielded with B10 for determining the total fast flux, Np237 for determining the total flux above 075 Mev, U238 for determining the total flux above 15 Mev, and S32 for determining the total flux above 25 Mev From these data the spectrum of fast neutrons can be constructed reasonably well for spectra similar to that of fission The amount of induced activity in the detecting elements is determined with scintillation counters, which are calibrated by irradiation of suitable foils with thermal neutronsFast neutron tissue dose can be calculated from the measured spectrum Since the foil method of measuring spectra works well for high intensity bursts of neutrons, dosimetry may be accomplished under conditions where other methods, eg, the ionization chamber and proportional counter, would lead to questionable data
TL;DR: In this paper, the increased effectiveness of multiple over single shields is shown and formulas for the computation of the shielding ratio (field outside/field inside) for any number of concentric shells of contemporary high-permeability materials in any combination.
Abstract: The increased effectiveness of multiple over single shields is shown and formulas (including a recursion formula suitable for automatic computation) are given for the computation of the shielding ratio (field outside/field inside) for any number of concentric shells of contemporary high‐permeability materials in any combination. Sample designs are given for shields 2¼, 3⅛, and 5¼ in. i.d. Scaling rules and charts are given for finding other designs without calculation. Graphs are given for the penetration of the field into the open end of the shield. The alternating‐field case is treated and formulas are given for finding the shielding ratio for alternating fields.
TL;DR: In this paper, a simple sputtering apparatus that consistently deposits opaque films of nickel and the noble metals in 3 to 10 min has been made, which is constructed from a standard Pyrex pipe reducer.
Abstract: A simple sputtering apparatus that consistently deposits opaque films of nickel and the noble metals in 3 to 10 min has been made. The chamber is constructed from a standard Pyrex pipe reducer. By use of a large‐diameter aluminum rod as the cathode support and a hemispherical aluminum shell as a shield for the pump orifice and base plate, the glow discharge has been confined primarily to the volume between the cathode and the work stand. The efficiency of the coating unit has thereby been increased. Films of nickel, iridium, ruthenium, and osmium formed on glass or quartz substrates were very adherent and were not readily scratched with a steel scribe.
TL;DR: In this article, a linear amplifier with a 1.2μsec clipping time and a gain of 50 000 suitable for scintillation spectrometry is described, where the unwanted background has a rate in excess of 100 000 cps and has components 40 times more energetic than the desired spectrum.
Abstract: A linear amplifier with a 1.2‐μsec clipping time and a gain of 50 000 suitable for scintillation spectrometry is described. Low‐energy photoelectric peaks can be resolved under conditions in which the unwanted background has a rate in excess of 100 000 cps and has components 40 times more energetic than the desired spectrum. No shift in the energy axis is observed under these conditions.The amplifier consists of a White cathode follower preamplifier, three feedback groups, and a White cathode follower output stage. Each of the three feedback groups contains four stages, three of which are amplifiers. Blocking is eliminated by the use of grid resistors low in value compared to the preceding stage plate load resistors. This feedback group configuration is also more linear by an order of magnitude than the conventional configuration. It is shown how RLC coupling between White cathode follower halves can conserve power supply voltage.It is shown how a cable correctly terminated at the transmitting end rather ...
TL;DR: A 256-channel pulse-height analyzer using a magnetic core memory is used at the Argonne National Laboratory as discussed by the authors, which uses a form of the Wilkinson method of generating numbers in response to input pulses, and correspond to the channel numbers into which the individual counts are to be recorded.
Abstract: A 256‐channel pulse‐height analyzer using a magnetic core memory is now in use at the Argonne National Laboratory. This analyzer uses a form of the Wilkinson method of generating numbers in response to input pulses. These numbers are proportional to the amplitudes of the input pulses, and correspond to the channel numbers into which the individual counts are to be recorded. The digital data processing circuits comprise a simple computer, with an internal memory which can store 256 sixteen digit binary numbers. A cathode‐ray tube display of the data in the form of a plot of counts versus channel number is available during and after operation. Permanent readout is in the form of a similar curve traced by a recording potentiometer. Printed decimal readout is also available. The normal average analyzer dead time is 80 μsec, and pulse rates in excess of 5 million per minute at the input circuit can be tolerated without appreciable data distortion.
TL;DR: In this paper, the authors consider the objectives that should be considered in design and construction of a practical equipment for blood flow recording from intact vessels using the square wave principle for electromagnetic flow recording.
Abstract: The square‐wave principle for electromagnetic flow recording offers several theoretical advantages over the dc or ac systems, particularly for blood flow recording from intact vessels. The degree to which these advantages may be obtained in practice depends upon the extent to which the equipment meets the specific requirements of the principle. This paper considers the objectives that should be considered in design and construction of a practical equipment.
TL;DR: In this article, a mass spectrometer employing a cycloidal focusing mass resolving system is described, which shows good mass resolving power, sensitivity, and analytical accuracy up to about mass 150 amu, and adequate service life.
Abstract: A mass spectrometer employing a cycloidal‐focusing mass resolving system is described. The mass analyzer proper, including the magnet and a high‐speed continuous‐flow inlet system, weighs approximately seventy pounds. The resolving system shows good mass resolving power, sensitivity, and analytical accuracy up to about mass 150 amu, and adequate service life. The mass resolving power can be extended substantially in cases where some loss of sensitivity and analytical accuracy is tolerable.
TL;DR: In this paper, the response function of NaI(Tl) scintillation detectors for gamma radiation has been calculated by the Monte Carlo method, and the results of this calculation are presented in terms of the photofraction, i.e., the ratio of the area under the photopeak to the total area of a scINTillation spectrum.
Abstract: The response function of NaI(Tl) scintillation detectors for gamma radiation has been calculated by the Monte Carlo method. Summary results of this calculation are presented in terms of the photofraction, i.e., the ratio of the area under the photopeak to the total area of a scintillation spectrum. Values of the photofraction are given for collimated monoenergetic radiation with energies between 0.279 and 4.45 Mev incident centrally on the endface of cylindrical crystals ranging in size from 0.25 in. (radius)×0.5 in. (length) to 2.5×9 in.
TL;DR: In this article, a fast, high-efficiency detector of heavy particles that results in negligible changes in the velocity and direction of the detected particles has been built, consisting of an electron accelerator and a scintillator that responds to delta particles emitted by the passage of each particle through a thin foil.
Abstract: A fast, high‐efficiency detector of heavy particles that results in negligible changes in the velocity and direction of the detected particles has been built. The detector consists of an electron accelerator and a scintillator that responds to delta particles emitted by the passage of each particle through a thin foil. For fission fragments, time resolutions of 3×10−9 sec, with efficiencies greater than 95%, have been obtained. The fragment velocity loss in traversing the thinnest foils used was less than 1%.
Abstract: The output pulses from scintillation detectors are amplified in conventional feedback amplifiers and transformed into a bipolar wave form, which passes the discrimination level of the following EFP 60 trigger circuit at a given time after inception of the scintillation pulse, independent of its amplitude within a wide range. If these standard pulses are shaped and fed into a fast coincidence circuit, even for NaI(Tl) resolving times of the order of 10−8 sec can be obtained. The main limitation of the method is due to time jitter of the standard pulses caused by statistical fluctuations of the rising edge of the photomultiplier pulses which results in a reduction of coincidence efficiency.
TL;DR: In this paper, a proton-recoil telescope with thin polyethylene radiator was designed for neutron spectroscopy and for neutron detection with known efficiency in the energy region from about 2 to 20 Mev.
Abstract: A proton‐recoil telescope with thin polyethylene radiator has been designed for neutron spectroscopy and for neutron detection with known efficiency in the energy region from about 2 to 20 Mev. Five radiator thicknesses may be chosen over this energy region. Protons recoiling near zero degrees from the radiator pass through two proportional counters and terminate in a NaI(Tl) crystal. Triple coincidences gate an analyzer for observing the spectrum from the crystal. A spectrum of 13.7‐Mev neutrons was observed with a width at half‐maximum of 5.3% and 6% background. The efficiency with this resolution at 13.7 Mev is 3.6×10−6.
TL;DR: In this article, a drop generator is described for the production of streams of drops the equivalent diameters of which are between 0.5 and 20 mm, based on the principle of the interrupted jet described by Lord Rayleigh.
Abstract: Drop generators are described for the production of streams of drops the equivalent diameters of which are between 0.5 and 20 mm. These generators are based on the principle of the interrupted jet described by Lord Rayleigh. An assessment is made of the advantages and disadvantages of drop production based on this principle, and data given showing a high degree of uniformity of drop size. Accurate size control and determination are discussed relative to the execution of experiments designed to measure the physical properties of drops during free fall. In order to study the instability and breakup of large drops, reasonably well‐formed drops are produced with equivalent diameters that are extremely difficult to produce by any other method. The behavior of large drops during free fall is concerned with theories of drop size distribution in natural rain.
TL;DR: In this article, an absolute anemometer based on a sinusoidally heated fine wire as tracer is described. But it is not suitable for measurements in gases under a wide variety of conditions.
Abstract: An absolute anemometer suitable for measurements in gases under a wide variety of conditions is described. The instrument, based on an idea first used by Kovasznay, utilizes the temperature fluctuations in the wake of a sinusoidally heated fine wire as tracer. A second hot‐wire detects the fluctuations, and the phase change between two successive positions of this wire can be used to determine the free stream velocity. The technique is shown to have good spatial resolution and an accuracy better than 2% in the velocity range 40–400 cm/sec. Sources of error and various experimental conditions are discussed in detail.