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Review of Scientific Instruments

Issue 12 • Date Dec 1961

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Displaying Results 1 - 25 of 58
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Design of Retarding Field Energy Analyzers

    Page(s): 1283 - 1293
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    Retarding field analyzers of the plane parallel plate, the spherical condenser, the Faraday cage, and the filter lens types are examined in some detail. The often neglected lens effect of the hole in the plane parallel plate through which the beam passes is shown to have significant effect on the energy resolution. The previous analysis of the spherical condenser is extended to the hemispherical case and the effect of the aperture in the inner sphere calculated. It is shown that for certain relations between the sphere sizes and the position of the source very high resolution may be obtained. The general restrictions on the performance of imaging retarding fields are considered and a design procedure based upon empirical knowledge of immersion lenses is given. View full abstract»

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  • Improved Probe Apparatus for Measuring Contact Resistance

    Page(s): 1294 - 1296
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    An apparatus, employing a fine‐wire probe, for the detection of insulating surface films on metal surfaces is described. A chemical cleaning procedure to prepare reliably clean palladium and gold surfaces is reported, and examples of the reproducibility of the method are given. Examples of the use of this apparatus include: the detection of high resistance areas on relay contacts taken from sealed relays, and a study of insulating base metal oxide impurities in commercial relay contacts. In the latter work, a sensitized paper test showed areas of iron and copper deposits on the contacts which could be correlated with areas of high resistance as indicated by the probe. View full abstract»

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  • Automatic Vapor Pressure Measurements at Moderately High Pressures

    Page(s): 1297 - 1302
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    Apparatus has been devised for automatically measuring and recording vapor pressure (1 to 35 atm) and temperature (-40 to +100°C) of pure liquids or solutions. The measurements are performed on a dynamic system wherein P and T are changed at very slow rates. Many P‐T data sets are recorded in a single run, providing the input for a computer program which correlates the two variables. Data for dichlorodifluoromethane are presented and compared with literature values. It is concluded that precise and accurate results are obtained with the automatic apparatus. Furthermore, the data processing program provides valuable information for analyzing the operation of the equipment. View full abstract»

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  • A 300‐Liter Heavy Liquid Bubble Chamber

    Page(s): 1302 - 1307
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    A heavy liquid bubble chamber with a useful volume of 100×50×50 cm operating in a magnetic field of 20 000 gauss is described. Engineering details are given. Lateral illumination of the liquid and scattering of light at 90° is used to photograph the tracks. Different mixtures of Freon (CF3Br) and propane have been used in the chamber allowing a choice of radiation length and stopping power particularly suitable to the experiment performed. View full abstract»

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  • Technique for Studying Piezoelectricity under Transient High Stress Conditions

    Page(s): 1308 - 1313
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    An experimental technique is described which is being successfully used to study the transient high stress piezoelectric behavior of synthetic alpha‐quartz. Short, flat‐faced cylinders of quartz are impacted upon each other at high velocity to produce the desired transient stress in the range from 5–70 kilobar. Precision is maintained in the alignment of the flat impact surfaces so that the Hugoniot conservation of momentum and the relationship governing the impact of flat cylinders may be used to compute the stress imparted to the target cylinders of quartz. Electric charge release data are taken in conjunction with the initial passage of the stress wave produced by impact. View full abstract»

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  • Simple Broad‐Range Magnetic Spectrometer

    Page(s): 1314 - 1316
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    The focusing properties are given for a broad‐range magnetic spectrometer formed by inclined plane pole faces. View full abstract»

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  • A One‐Mev/Nucleon Sloan and Lawrence Heavy‐Ion Linear Accelerator

    Page(s): 1316 - 1326
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    A description is given of a small heavy‐ion linear accelerator based on the use of a twin transmission line as first suggested by Sloan and Lawrence. Ions are accepted if their e/m values are ⅛ or greater (relative to the proton) and are accelerated to a final energy of 1.04 Mev/nucleon. The accelerator has 40 drift tubes fitted with focusing grids, and about 350 kw of pulsed rf are needed for ions of e/m=⅛. The radio frequency is 25 Mc, and the accelerator is pulsed at up to 50 pps with a pulse length of 500 μsec. Injection velocity is 0.007 c, corresponding to a dc acceleration from the ion source through 180 kv for an ion of e/m=⅛. Ions are produced in a pulsed dc arc of the Penning type operating in a magnetic field of 1000 gauss and the dc accelerating voltage is supplied by an electrostatic generator. Typical pulsed meter currents so far obtained are, for He+, input 4 ma, output 150 μa; for N2+, input 3 ma, output 75 μa. The accelerator is the first stage of three which will take the ions to a final energy of 10 Mev/nucleon. The second and third stages, which are under construction, will be cavity resonators of the Alvarez design. View full abstract»

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  • Design and Sensitivity of a Photoconductive Recording System Applied to the Sucksmith Ring Balance

    Page(s): 1327 - 1328
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    This paper describes a photoconductive locator for continuous recording of physical displacement. The system is applied as an example to the optomechanics of the Sucksmith ring balance. It is shown that the sensitivity and accuracy are considerably higher than those obtained with optical instruments such as the traveling telemicroscope. Application to wave modulation is suggested. View full abstract»

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  • Elastic Modulus Measurements at High Audio Frequencies Using a Vibrating Reed

    Page(s): 1329 - 1331
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    High audio frequency elastic modulus measurements are possible using the vibrating reed if one can measure overtone frequencies. An electromagnetic detector is described which facilitates the measurement of these overtones, thereby extending the range of the vibrating reed to at least 10 kc. View full abstract»

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  • Development of a 100‐ma Proton Source and Lens System for the Bevatron Mark‐II Injector

    Page(s): 1331 - 1336
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    A Von Ardenne‐type ion source and lens system has been developed for use as a preinjector to the 18‐Mev strong‐focusing linear accelerator. Proton beams of 120 ma at an ion production efficiency of 83% have been obtained. A magnetic beam‐confining system has been built, and a beam of 85 ma has been transported 82 in. The beam energy was 370 kev, and its emittance was 100 mrad‐mm. The beam diameter was 1 cm. This is within the linear accelerator's calculated acceptance of 179 mrad‐mm. View full abstract»

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  • Improved Gravimetric Vapor‐Sorption Apparatus

    Page(s): 1337 - 1340
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    This improved gravimetric vapor‐sorption apparatus was designed for vapor‐sorption measurements at 20–50°C with condensable vapors, e.g., water and organic vapors on inorganic and organic adsorbents, such as minerals and resins. The apparatus can be readily adapted to low‐temperature adsorption of noncondensable gases, e.g., N2, Kr, and Ar. The system consisted of a helical spring (quartz or tungsten) sorption balance. A Pirani gauge and a mercury manometer permitted the measurement of vapor pressures from several microns to more than 100 mm. Important considerations relevant to the design of helical springs (quartz or metal) were summarized, and a comparative evaluation was made of the advantages and limitations of tungsten and quartz helices. A practical high‐vacuum Teflon seal for use in place of greases and waxes on ground glass joints was developed. This seal was designed for use with organic vapors. The aqueous vapor pressures at 20°C were measured for a wide range of concentrations of aqueous sulfuric acid solutions. These data were in excellent agreement (of the order of 1%) with the published data down to pressures of 1 mm of mercury, and they provided a reliable indication of the accuracy of the vapor pressures measured with this apparatus. View full abstract»

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  • Continuous Casting of Thermoelectric Materials

    Page(s): 1341 - 1343
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    A continuous casting apparatus has been developed that will produce thermoelectric material rapidly, reliably, and in large quantities with a minimum amount of labor. Bismuth telluride and alloys of Bi2Te3, Sb2Te3, and Bi2Se3 were cast in rods up to 70 in. in length. The deviation of the thermoelectric properties throughout the length of the rods was less than 5%. View full abstract»

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  • Scanning Microscope for Photoelectric Data Evaluation

    Page(s): 1343 - 1346
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    This paper describes a mechanical scanning device for evaluation of microscopic data over a large area and an electronic system for collecting and sorting information about the size of light and dark patches on a plate. Preliminary experiments for measuring the size distribution of the islets of Langerhans in histologic sections of the pancreas are described. View full abstract»

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  • Nonobstructive Low Energy Electron Beam Monitor

    Page(s): 1347 - 1348
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    A modified type of secondary electron monitor useful for the monitoring of low energy electron beams during irradiation is described. Using the window foil at the end of the accelerator as a part of the detector, it is designed to have minimum disturbance on the primary beam. The monitor output is independent of the primary beam energy and proportional to the primary beam current in the range over which the monitor was tested (1.0–1.7 Mev and up to 120 μa). View full abstract»

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  • Apparatus for the Measurement of Stress in Vacuum Evaporated Films

    Page(s): 1349 - 1351
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    An apparatus suitable for the measurement, in vacuum, of the residual stress in evaporated metal or dielectric films has been built and tested. The substrate on which the film is deposited is clamped at one end to form a cantilevered beam. When the substrate is bent as a result of the film stress, the force required to restore the beam to its initial position is measured. The stress is then calculated from a knowledge of the restoring force, the beam dimensions, and the film thickness. A stress of 5×107 d/cm2 can be easily detected and measured with this apparatus. View full abstract»

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  • Generator for Producing High Concentrations of Small Ions

    Page(s): 1351 - 1355
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    An arrangement of a needle and a sonic orifice has been developed which is capable of converting the corona current into free small ions with 100% efficiency. Positive and negative ion concentrations of 1011 ions/cm3 in the sonic jet and total ion outputs of 1014/sec have been achieved using 2.5 cfm of free air at 30 psig through a116-in. orifice. Theoretical and experimental studies of the ion decay rate in the jet show that the concentrations drop off approximately as the square of the distance from the ionizer. View full abstract»

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  • High Intensity Low Noise Rubidium Light Source

    Page(s): 1356 - 1358
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    A 40‐w electrodeless rubidium light source is described which emits a total of 13 w in the two D lines. The intensity is a factor of 50 larger than that of a previously reported electrodeless rubidium source. In addition, high stability, long life, minimum noise, and the absence of self‐reversal make it attractive for optical pumping studies of alkali metal vapors. View full abstract»

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  • Čerenkov Radiation Extensive Air Shower Telescope

    Page(s): 1359 - 1362
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    A telescope is described which has been used to determine the directional characteristics of the Čerenkov radiation accompanying extensive cosmic ray air showers. The reflecting telescope has a 12.5‐in. aperture, a 48‐in. focal length and is of an off‐axis design to permit the use of a 19 photomultiplier tube light detection array. Pulse‐height information from each tube is fed to separate, spaced inputs on a delay line which supplies the resulting signal for oscilloscope presentation. The various pulse heights provide the Čerenkov radiation directional information. An average of 75% of the Čerenkov photons arrive at the telescope within a half‐angle of 2.3°. View full abstract»

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  • Method of Measuring the Normal Velocity Distribution of Secondary Electrons at Low Primary Bombarding Energies

    Page(s): 1362 - 1366
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    Experimental apparatus designed to measure the secondary electron emission from solids at low primary electron energies is described. The design permits the determination of the normal velocity distribution of secondary electrons off insulating targets. Some of the usual difficulties associated with measurements of this kind are avoided through the use of an orthicon‐type deflection system to separate primary and secondary beams. Measurements of the secondary emitting properties of molybdenum, some of which are performed under pulse conditions appropriate for insulating targets, are described and serve to demonstrate the performance of the apparatus. View full abstract»

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  • Calibrated Scintillator Probe for Determining Energy Distribution, Density, and Mean Energy of the Electronic Component of a Pyrotron Plasma

    Page(s): 1367 - 1372
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    A method of determining some of the characteristics of a deuterium plasma generated and confined in a magnetic‐mirror machine is described. In this case the electronic component of the plasma is characterized by a mean energy considerably greater than the ionic component. The mirror configuration readily allows detection of the flux of particles which escape through the mirror loss cone from the plasma confined between the mirrors. Scintillator probes placed near a mirror and outside the confinement region do not interfere with the confined plasma. By the use of thin aluminum absorbers placed in front of the scintillator, a determination was made of the energy distribution of the electron flux as a function of time during the decay of the pulsed mirror field. Such measurements were used to infer plasma conditions by consideration of the processes resulting in the leakage of plasma particles through the mirror. In determining the density of the plasma, the correction to be made to the integral of electron flux over time is based on conclusions as to plasma stability and the known decay rate of the pulsed magnetic field. View full abstract»

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  • Vacuum Measurements by Means of Alternating Gas Discharges

    Page(s): 1373 - 1377
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    A pressure gauge for the range from several mm Hg down to the micron region is described. The new gauge, based on the properties of alternating gas discharges, measures pressure in terms of the frequency of a relaxation oscillator incorporating as the nonlinear element a glow discharge between electrodes immersed in the gas, the pressure of which is to be determined. A stability of 1% has been obtained; the robustness and simplicity of the instrument render it particularly suitable for rocket‐borne measurements at high altitude. View full abstract»

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  • Accuracy of Bubble Location in a Bubble Chamber

    Page(s): 1378 - 1380
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    A measurement is reported of individual bubble locations along tracks of high‐energy protons in a very small, short time scale pentane bubble chamber. Track distortions of the usual kind are greatly reduced in this system, so that one is measuring, to a precision of a few microns, the deviation of the true centers of the bubbles from the particle path. The average deviation in bubble position measurement is found from second differences to be 3.8 μ in space, most of which is shown to be accounted for by measurement errors. The average bubble is thus found to be centered on the track to better than 4 μ in hydrocarbons; however, an occasional bubble will be off by many times the average deviation. Arguments are advanced to show that a similar precision should obtain in hydrogen. This result is shown to be in general agreement with the bubble‐chamber theory of Seitz. View full abstract»

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  • Diffuse Reflection Coating for Use with Čerenkov Counters

    Page(s): 1380 - 1382
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    A diffuse, highly reflecting coating for use with Čerenkov counters is described. This coating can be used to advantage inside inorganic‐liquid Čerenkov counters, or can be used externally when bonded to the inside surface of the light‐tight radiator cover. View full abstract»

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  • Radio‐Frequency Spectrometer with Bidirectional Square Wave Frequency Modulation

    Page(s): 1383 - 1386
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    The use of a bidirectional square wave for frequency modulation of a radio‐frequency spectrometer offers certain advantages, the principal one being that the background signal due to incidental amplitude modulation can be effectively eliminated by appropriate adjustment of the relative amplitudes of the positive‐ and negative‐going excursions. A quadrupole resonance spectrometer employing this principle has given excellent sensitivity and faithful line shape presentation. The oscillator, of the regenerative type, is based on a circuit recently published by Knight. The frequency modulation method should be widely applicable to other types of spectrometers. View full abstract»

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Aims & Scope

Review of Scientific Instruments, published by the American Institute of Physics, is devoted to scientific instruments, apparatus, and techniques.

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Editor
Albert T. Macrander
Argonne National Laboratory