Showing papers in "Review of Scientific Instruments in 1949"
TL;DR: A microwave spectrograph is described in which the absorption of the gas being studied is modulated by the application of a periodic Stark‐effect field so that the output of the crystal detector contains a radiofrequency component which can be amplified with a narrow‐band amplifier.
Abstract: A microwave spectrograph is described in which the absorption of the gas being studied is modulated by the application of a periodic Stark‐effect field so that the output of the crystal detector contains a radiofrequency component which can be amplified with a narrow‐band amplifier. By using a very narrow band‐width, achieved by employing phase‐sensitive detection, high sensitivity is obtained. The klystron is swept mechanically over the frequency range. Details of the components are given.
101 citations
TL;DR: The absolute sensitivity of a pneumatic detector is calculated for the case of an infinitely extended flat heat cell and the calculated r.n.m.i.e.s. is seen to be in good agreement with the experimental results.
Abstract: Following an introductory sketch of the application of the pneumatic infra‐red detector to spectrometry, the absolute sensitivity of a pneumatic detector is calculated for the case of an infinitely extended flat heat cell. The calculated r.m.s.e.n.i. is seen to be in good agreement with the experimental results.
87 citations
TL;DR: In this article, a qualitative description of the theory of the operation of a shock tube is given together with a discussion of its design, as well as some auxiliary equipment needed in its operation.
Abstract: A qualitative description of the theory of the operation of a shock tube is given together with a discussion of its design. The construction of a particular tube 4 in.×18 in.×38 ft. is described as well as certain auxiliary equipment needed in its operation. The technique of operating the device and comparisons of its performance with expectations are discussed. This tube has been used to study certain properties of shock waves and to obtain a flow field of marked uniformity and freedom from turbulence. The Mach number of this flow may be adjusted at will from zero to the supersonic range without difficulty. An interferometer makes it possible to obtain an instantaneous picture of the density field so that the apparatus may be used as a very efficient transonic wind tunnel.
87 citations
TL;DR: The gradient calorimeter with its rapid response (time lag 42 seconds) is specifically designed for studies of reflex mechanisms involved in temperature control and is suggested to encourage wider application of direct calorimetry in experimental and clinical studies.
Abstract: A rapidly responding calorimeter for continuous recording of biological heat exchange has been described. The method is based on the enclosure of the subject in a shell completely lined with a uniform heat flow metering layer (``gradient layer'') while ventilatory and respiratory heat losses are determined in heat exchange meters based on the same technic. The measurement comprises in one thermoelectric potential the sum of all components of heat loss (radiant, convective, conductive, and evaporative fractions). Partitioning measurements of respiratory and evaporative heat losses are readily obtained. Environmental conditions can be closely controlled, and widely varied.The gradient calorimeter with its rapid response (time lag 42 seconds) is specifically designed for studies of reflex mechanisms involved in temperature control. It is, however, suggested that the characteristics described will, in general, encourage wider application of direct calorimetry in experimental and clinical studies.
79 citations
TL;DR: In this paper, the authors describe a bridge for reasonably accurate measurement by direct balance of capacitance and conductance in the frequency range 50 c/sec. to 5 cm/sec., and over most of this range is essentially direct reading in the two admission components with negligible unbalance from lead effects or guard circuits of the unknown.
Abstract: The bridge described has been developed for reasonably accurate measurement by direct balance of capacitance and conductance in the frequency range 50 c/sec. to 5 mc/sec., and over most of this range is essentially direct reading in the two admittance components with negligible unbalance from lead effects or guard circuits of the unknown. These properties are realized by using two circuits developed from the work of others. The first employs inductively coupled ratio arms to minimize residual impedance effects and unbalance by guard circuits, the second, a conductance shifter wye network with good high frequency properties and an essentially linear conductance reading. Design considerations and limitations of these circuits are discussed, as are suitable test cells and auxiliary equipment.
72 citations
TL;DR: A brief description of an apparatus, together with a few representative curves, suitable for measuring the composition of very small amounts of any gas having at least one near infra‐red absorption band or, if measured in the presence of other gases, at least two unique absorption bands.
Abstract: A brief description of an apparatus, together with a few representative curves, is presented, suitable for measuring the composition of very small amounts of any gas having at least one near infra‐red absorption band or, if measured in the presence of other gases, at least one unique absorption band. With the bolometers used, 90 percent full scale response is obtained in 0.15 seconds on a 0.5 cc sample, permitting a 0.4 cm optical path and a very nearly linear response over the range usually found in physiological concentrations and anesthesia.
60 citations
TL;DR: A simple, portable instrument is described which employs the nuclear absorption method and the known value of the proton magnetic moment to determine magnetic field strength.
Abstract: A simple, portable instrument is described which employs the nuclear absorption method and the known value of the proton magnetic moment to determine magnetic field strength. No known fields and no geometrical calculations are required for calibration. The range covered by the present instrument is approximately 3000 to 19,000 gauss. No upper limit is inherent in the method. Homogeneity is required over a small cylindrical volume. Absolute accuracy of better than ±0.2 percent is obtainable, depending only on precise measurement of frequency. Higher accuracy is possible in comparing fields and in measuring field changes.
49 citations
TL;DR: A null device for determining the ratio of two absolute temperatures with an accuracy of 0.1 percent is described, which balances the mean‐square fluctuations in voltage across the terminals of two resistors arising from thermal agitation at the temperatures to be compared.
Abstract: A null device for determining the ratio of two absolute temperatures with an accuracy of 0.1 percent is described. This device balances the mean‐square fluctuations in voltage across the terminals of two resistors arising from thermal agitation at the temperatures to be compared. The ratio of the resistances, when the noise voltages from the two resistors are equal, determines the ratio of their absolute temperatures. The limitation on the ultimate accuracy of the ratio of temperatures so determined is imposed by the relative value of the first and second moments of the voltage fluctuations observed, which in turn depends on the length of time utilized in averaging the fluctuations. With the apparatus described below, an observation time of two minutes is adequate to guarantee the accuracy claimed above for high temperatures, provided certain elementary precautions in constructing the noise thermometer are observed. Numerous tests have been conducted in the neighborhood of 1000°K which substantiate these claims. Extrapolation of the performance obtained at such temperatures indicates that material improvements in the accuracy of the absolute temperature scale above 2000°K may be obtained. The calibration of the thermometer is independent of the chemical composition and past physical history of the material from which it is constructed, in addition to being independent of the absolute pressure.
47 citations
TL;DR: The capabilities and limitations of several impulse generators and voltage dividers, and a micro‐oscillograph sweep circuit for dealing with kilovolt impulses in the millimicrosecond range, are described.
Abstract: The capabilities and limitations of several impulse generators and voltage dividers, and a micro‐oscillograph sweep circuit for dealing with kilovolt impulses in the millimicrosecond range, are described. The most successful combination produces and measures an impulse of a rise time equal to 4×10−10 sec.
47 citations
TL;DR: The counter characteristics of a discharge tube using plane‐parallel electrodes have been investigated, particularly with regard to the short time lags inherent in the streamer type of spark which occur with such a geometry at near‐atmospheric pressure.
Abstract: The counter characteristics of a discharge tube using plane‐parallel electrodes have been investigated, particularly with regard to the short time lags inherent in the streamer type of spark which occur with such a geometry at near‐atmospheric pressure. Construction details for parallel‐plate counters with good counter characteristics are given. Spurious counts were minimized by an argonxylene filling mixture and the use of a univibrator quench circuit. The uncertainty in the reaction time of the counters is ±5×10−9 sec.
41 citations
TL;DR: A single lens convergent light apparatus is described with which diffusion in liquids may be studied by an interference method and results indicate that the apparatus is capable of 0.1 percent precision.
Abstract: A single lens convergent light apparatus is described with which diffusion in liquids may be studied by an interference method. Details of the optical elements and their mounting and alignment are given as well as the design of a temperature control regulating near 0°C to within 0.01°C. A modified Polson sharpening technique has been used successfully in forming diffusion boundaries in a Tiselius cell. A modification of the Rayleigh interferometer has been employed as an aid in the measurement of the refractive index increment parameter, jm, which is required for the evaluation of the diffusion coefficient. During diffusion a reference slit image obtained by the employment of special cell and plate masks permits more accurate measurements of the undeviated slit image position than have been obtained from the interference diffusion fringe picture. Results indicate that the apparatus is capable of 0.1 percent precision.
TL;DR: An instrument for recording continuously the relative abundance of gases in a three component mixture is described and high accuracy of analysis has been sacrificed in favor of high speed response.
Abstract: An instrument for recording continuously the relative abundance of gases in a three component mixture is described. High accuracy of analysis has been sacrificed in favor of high speed response since the instrument was designed primarily for use in the investigation of respiratory problems. An instantaneous change in gas composition will appear on the record with a lag of less than 0.2 second and will require approximately 0.1 second to settle on this new value.
TL;DR: In this article, the theory of the proton synchrotron was developed with particular reference to the problems of injection and stability in the initial acceleration period, and the theory was used to set up criteria relating the dimensions of a Proton Synchroformer to the conditions for stability and to the beam intensities obtainable.
Abstract: The theory of the electron synchrotron has been amply covered elsewhere, but the proton synchrotron exhibits a number of distinct but important differences particularly at low energies. In the present paper the theory for this latter accelerator is developed with particular reference to the problems of injection and stability in the initial acceleration period. This theory is used to set up criteria relating the dimensions of a proton synchrotron to the conditions for stability and to the beam intensities obtainable.
TL;DR: In this paper, the design and performance of an accurate flow system utilizing critical velocity orifices is described, and an absolute accuracy of three parts in a thousand is realized over a flow range of 0.002 to 2 cubic feet per minute.
Abstract: The design and performance of an accurate flow system utilizing critical velocity orifices is described. Results indicate that an absolute accuracy of three parts in a thousand is realized over a flow range of 0.002 to 2 cubic feet per minute. Calibration of the flow system was accomplished by means of a specially modified and carefully standardized wet test gas meter. Descriptions of the components of the flow system and of subsidiary calibrating equipment are presented.Critical flow orifice discharge coefficients are found to be independent of the type of gas; however, because of gas impurities, prediction of relative rates of flow of various gases through an orifice by use of theoretical relationships is uncertain, and experimental data are given to illustrate this.
TL;DR: A general theory of geometric magnetic focusing of charged particles is developed in this paper, where some special cases are discussed and the type of focusing used in general use is discussed; another, equally simple, eliminates second-order aberrations.
Abstract: A general theory of geometric magnetic focusing of charged particles is developed. Some special cases are discussed. One proves to be the type of focusing in general use; another, equally simple, eliminates second‐order aberrations.
TL;DR: A methane flow beta-proportional counter has been designed to detect the high and low energy solid beta-emitters used in tracer experiments as mentioned in this paper, which greatly simplifies the analytical technique involved in such experiments.
Abstract: A methane flow beta‐proportional counter has been designed to detect the high and low energy solid beta‐emitters used in tracer experiments. At present, both C14 and P32 are being counted. The use of a sintered‐glass Gooch crucible, both as a filter and sample holder, greatly simplifies the analytical technique involved in such experiments. The instrument is stable and the results are reproducible over long time periods.
TL;DR: A low temperature x‐ray diffraction technique, especially suitable to single crystal work, is described, which prevents moisture condensation and permits rotation and oscillation of the specimen while it is being cooled.
Abstract: A low temperature x‐ray diffraction technique, especially suitable to single crystal work, is described. Crystals are grown in glass capillaries on the x‐ray camera. Position and orientation are determined with the aid of a polarizing microscope on the apparatus. A special specimen holder is used which prevents moisture condensation and permits rotation and oscillation of the specimen while it is being cooled.
TL;DR: In this article, an annular resolving slit should be provided at a determined radial and axial location relative to the source in a β-ray spectrometer with axial homogeneous magnetic field.
Abstract: In a β‐ray spectrometer with axial homogeneous magnetic field, it is shown that optimum energy resolution and luminosity are obtained when the trajectories make an angle close to 45° with the field and that an annular resolving slit should be provided at a determined radial and axial location relative to the source The combined effect of three independent sources of instrumental energy line width is analyzed for the optimum condition Formulas are given for the optimum dimensions, the energy resolution and the luminosity
TL;DR: In this article, it was found that the approximate formulas of Drude which express as a function of the film thickness the ratio and phase difference of the components vibrating in the plane of incidence and perpendicular to it are valid for thin films.
Abstract: Measurements of ellipticity of light reflected from a film‐coated metal surface have been made for films varying in thickness from 25 to 40,000A. It was found that the approximate formulas of Drude which express as a function of the film thickness the ratio and phase difference of the components vibrating in the plane of incidence and perpendicular to it are valid for thin films. The general formula of Drude expressing the phase shift as a function of the film thickness represents with a fair approximation the experimental results obtained with metallic slides coated with films of Ba stearate whose thickness is up to the order of the wave‐length of light. Thus, for the first time, Drude's theoretical formulation has been verified experimentally. For films whose thickness is many times the wave‐length of the light used, there is a progressive divergence from Drude's general formula, the cause of which can possibly be due to the birefringence of the films which has been neglected in this work.
TL;DR: In this article, single crystals of nickel, cobalt, and various alloys are grown by slow cooling of the melt, and they are oriented by optical means and by x-rays, and ground to the desired shape using the technique described.
Abstract: Single crystals of nickel, cobalt, and various alloys are grown by slow cooling of the melt. They are oriented by optical means and by x‐rays, and ground to the desired shape using the technique described.
TL;DR: A theory of the magnetic lens beta‐ray spectrometer utilizing the uniform field of a long solenoid is developed and it is found that for a given intensity there is an optimum source diameter and an optimum emission angle.
Abstract: A theory of the magnetic lens beta‐ray spectrometer utilizing the uniform field of a long solenoid is developed. First the case of a point source is considered, and it is found that the resolving power, for a given solid angle, is maximum when the emission angle α (average angle between the rays leaving the source and the axis) is 45° 37′. Then the theory is extended to the case of a disk source, and it is found that for a given intensity (product of the source area by the solid angle) there is an optimum source diameter and an optimum emission angle, ranging in practical cases between 36° and 40°. The problem of optimum conditions when the quantity of copper in the solenoid and the electric power available are limited by economical considerations is also studied, and it is found that the optimum α‐value is in this case about 21°.
TL;DR: One model of this radiofrequency link which was developed for nerve stimulation and which has performed well in the laboratory is described in detail.
Abstract: Voltages of arbitrary wave forms, such as those employed for stimulating biological tissues, are normally obtained from ``grounded'' signal generators. Isolation of such signals from ground can be accomplished by utilizing radiofrequency transmission of energy. The signal generator voltage serves as the source of plate power for a midget radiofrequency oscillator which converts the signal to amplitude‐modulated carrier energy. This radiofrequency energy is then transmitted across a small air gap to a receiving circuit where it is demodulated and filtered. The voltage thus recovered is a faithful reproduction of the original signal but is isolated from the input circuit as well as from ground. One model of this radiofrequency link which was developed for nerve stimulation and which has performed well in the laboratory is described in detail.
TL;DR: In this paper, a method for preparing Ta-H and Zr-H targets for economic use of tritium was described and the use of these targets under deuteron bombardment was discussed.
Abstract: Methods are described for preparing Ta–H and Zr–H targets for economic use of tritium. Ratios of hydrogen isotope to metals of about 1.0 were obtained. The use of these targets under deuteron bombardment is discussed.
TL;DR: A timing circuit is described similar in principle to the Neddermeyer ``chronotron,'' but with the following simplifications and modifications: parallel‐wire polythene‐tape line to eliminate co‐ax ``plumbing,'' germanium crystal detectors, and a delay‐line presentation circuit.
Abstract: A timing circuit is described similar in principle to the Neddermeyer ``chronotron,'' but with the following simplifications and modifications: parallel‐wire polythene‐tape line to eliminate co‐ax ``plumbing,'' germanium crystal detectors, and a delay‐line presentation circuit. This circuit uses a single common amplifier for all pulses, which increases stability, makes adjustment easy, and effects a tenfold saving in the number of tubes. It simultaneously records time intervals in two ranges, e.g., 0–0.1 and 0–5 μsec. The precision is 1×10−9 sec., but may be increased at the expense of the range. Problems connected with coupling the instrument to parallel‐plate counters are discussed.
TL;DR: In this paper, a torsion pendulum was used to measure internal friction at a constant given stress amplitude and a constant frequency of vibration, which can easily be varied over a wide range.
Abstract: A simple torsion apparatus has been developed for measurement of extremely high internal friction by determining the angle by which strain lags behind the stress in forced cyclic vibration. The results of measurement were compared with torsion pendulum measurements using free decay method. The highest internal friction measured with this apparatus was 0.55. This apparatus can be used to measure internal friction at a constant given stress amplitude and at a constant frequency of vibration. The stress amplitude and frequency of vibration can easily be varied over a wide range. There is no theoretical limit to the lowest frequency of vibration that can be used with this apparatus. The feature that measurements can be made while the zero point is changing renders this apparatus very useful in the study of internal friction of freshly cold‐worked metals.
TL;DR: The completed apparatus appears to meet requirements to permit operation at temperatures up to at least 2000°C, in a high vacuum and to permit successive exposures of the specimen held at temperature.
Abstract: A high temperature x‐ray powder diffraction camera has been designed to yield patterns at temperatures in excess of 2500°K. The sample, in form of a wire, compacted rod, or contained (wherever suitable) in a thin walled quartz or ceramic tube, is heated indirectly by conduction and radiation in a thin walled molybdenum, tantalum, or platinum furnace. The furnace is heated by high frequency (0.5 megacycles) eddy currents induced by a small induction coil. The cylindrically shaped furnace and the sample are held coaxially in the induction coil and slowly revolved. The specimen temperature is maintained constant to ±0.2 percent by an especially designed temperature regulator. A water‐cooled copper jacket with slots covered with metal foil to filter the diffracted x‐radiation surrounds the furnace and is used to protect the x‐ray film from heat and light. The temperature of the specimen is measured with a disappearing filament optical pyrometer at temperatures in excess of 1100°K and a platinum, platinum‐rhod...
TL;DR: In this paper, the design and performance of an apparatus for the measurement of magnetic susceptibilities at the temperatures attainable with liquid helium was described, and extensive trials were conducted on small specimens.
Abstract: Data are presented on the design and performance of an apparatus for the measurement of magnetic susceptibilities at the temperatures attainable with liquid helium. After extensive trials, the instrument has proved itself easy and reliable in operation and especially suited to measurements on small specimens.
TL;DR: The operation of the 184‐in.
Abstract: The operation of the 184‐in synchro‐cyclotron is reviewed in terms of the theory as developed by Bohm and Foldy Certain relevant data on the properties of the magnet and rotating condenser are also presented