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Review of Scientific Instruments

Issue 5 • Date May 1972

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Displaying Results 1 - 25 of 51
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • A Frequency Swept Injection Locked Nuclear Induction Spectrometer with Signal Averaging

    Page(s): 723 - 726
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    A frequency sweep injection locking technique, suitable for signal averaging and fast passage studies, has been developed for use with a nuclear induction spectrometer. View full abstract»

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  • Tubular Fast Flow Reactor for High Temperature Gas Kinetic Studies

    Page(s): 726 - 730
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    A fast flow reactor suitable for gas kinetic studies at temperatures up to ≈2000 K is described. The reactor has been used in studies of the reactions of atomic Fe and Na with O2, for which performance data are given. View full abstract»

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  • Refinements to a Standard LEED‐Auger System for the Analysis of Electron Emission at Low Primary Beam Energies

    Page(s): 731 - 734
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    Refinements to a basic three‐grid LEED‐Auger system are described which permit a more detailed analysis to be made of the electron emission from solids at low primary beam energies. This is accomplished by (i) cross modulation of electron gun and analyzer grids for suppression of unwanted signal, (ii) improving the collector efficiency for low energy electrons, and (iii) recording the second derivative of the energy distribution curve. View full abstract»

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  • A Photon Counting Apparatus for Kinetic and Spectral Measurements

    Page(s): 734 - 737
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    An apparatus is described for spectral and time response measurements in luminescent materials using photon counting techniques. The system's most novel feature is its ability to switch rapidly between spectral and kinetic modes. Using the delayed coincidence method, with its excellent sensitivity, the kinetic measurements can be made easily with bandpasses as small as 0.5 meV. The system uses laser excitation pulsed by an acousto‐optic modulator (3 nsec 1/e time) and for very fast measurements, mode locked pulses are used (0.25 nsec wide). Luminescent time decays from 1 nsec to 80 μsec can be obtained. The delayed coincident technique has been adapted to provide time resolved spectra with small time windows (≪10 nsec) in the same range. View full abstract»

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  • A High Pressure Optical Cell for Study of Biochemical Solutions

    Page(s): 738 - 739
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    This paper will describe the construction and use of an optical cell for spectrographic studies of biochemical solutions under pressures up to 4080 atm. Data from such studies of myoglobin will also be presented. The optical cell described incorporates the following design features: It is a monoblock configuration comprising both a pressure intensifier and an optical portion; the sample contacts only glass and paraffin; the cell interfaces easily with spectrophotometric equipment commonly used in biochemistry; it is relatively easy to operate and survives repeated use; it is constructed of a material not previously used for this application. View full abstract»

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  • An Optical Thickness Monitor for Thin Film Vacuum Deposition Control

    Page(s): 740 - 743
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    An optical thickness monitoring device is described which utilizes simple mechanical construction and integrated circuit electronics to achieve a system which is easy to align, accurate, and highly reliable. View full abstract»

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  • A Dilatometer for Volume‐Temperature Determinations of Liquids

    Page(s): 743 - 745
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    An instrument is described for the continuous volume measurement of small (3.7 ml) samples of liquids as a function of temperature. The sample is sealed in a stainless steel bellows chamber. Volume changes are measured with a linear variable differential transformer while temperature is measured by means of a thermistor and associated circuitry. Volume changes of sample can be determined to better than 1.0×10-4 ml over a temperature range of 10–60°C. The maximum sample volume change is 7%. View full abstract»

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  • A Method for Studying Distribution Function Evolution during Wave‐Particle Interactions

    Page(s): 746 - 748
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    A gated electrostatic trap has been developed that enables experimental observation of the time evolution of particle distribution functions for a wide range of wave‐particle interactions. The technique entails trapping of an electron beam in a region where arbitrary wave fields are set up and the analysis of the perturbed distribution function after an arbitrary interaction time. View full abstract»

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  • A Uniaxial Stress Apparatus

    Page(s): 749 - 753
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    A detailed description is given of the design and construction of a new type of uniaxial stress apparatus that is based on the use of a rotating cam to transmit the stress to the sample. The apparatus can be used at low temperatures and in large magnetic fields. Some preliminary data (for stress values up to ∼7.6 kilobar, the highest value yet reported for InSb) on the effect of stress on the frequency of magnetophonon oscillations in n‐InSb at 77 K are presented. View full abstract»

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  • A 1/H Drive for Use with Superconducting Solenoids

    Page(s): 753 - 755
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    A circuit is presented that can be used with nearly all superconducting solenoid magnet systems to sweep the magnetic field such that equal intervals in the inverse of the field are progressed in each instant of time. The circuit produces a programming voltage that controls the total power supply current. The ideal situation of the resistanceless solenoid shunted by the virtually inductanceless persistent mode switch causes the programming voltage to assume a particularly simple form. View full abstract»

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  • Use of Fiber Optics in the Study of Chemiluminescent Reactions

    Page(s): 756 - 758
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    The use of stationary light pipes and a stationary detector to measure light decay along a tube in a steady state flow system is described. This method exhibits a number of advantages over that of moving the detector. A means of calibrating the transmission of the light pipes in situ by using the properties of the yellow nitrogen afterglow is discussed. The high degree of spatial resolution achievable by this technique should make it especially suitable for studies of small flames and discharges. View full abstract»

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  • Noise Suppression by Time Exposure Oscilloscope Photography

    Page(s): 759 - 760
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    We describe a simple and inexpensive means of enhancing repetitive signals obscured by noise with roughly equal amplitude. The signal and noise are displayed on an oscilloscope, and we perform a time average over many traces by time exposure photography. If the oscilloscope triggering is synchronous with the signal, the result is a significant suppression of the offending noise. View full abstract»

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  • Vibrating Sample Magnetometer for Protein Research

    Page(s): 760 - 762
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    A simple magnetometer for use with weakly paramagnetic frozen solutions is described. It uses the same superconducting coil for generating the field and detecting the vibrating magnetization. A nearly translationally invariant sample holder and low frequency vibration of large amplitude are advantageous. In a sample volume of 0.7 ml, 2×10-7 moles of a species having a single g=2, s=½ spin produces a signal reproducibly different from that of pure water, when the temperature is varied from 77 to 2 K. View full abstract»

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  • A Method for Precise Measurement of the Dielectric Constant of Liquids in a Wide Frequency Range

    Page(s): 763 - 765
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    A rapid precise method for measurement of the dielectric constant of liquids in a wide frequency range is described. Using a micrometer‐controlled electrode in a cell filled with the specimen liquid, the dielectric constant is precisely determined from the micrometer scale to within ±0.2%. Even though the cell is two‐terminal, this method is nearly free of the influence of the stray capacitances and the residual inductances of the electrodes or of the leads. It makes possible an accurate measurement at high frequency. Once the micrometer scale calibration has been done, it takes only a few minutes for the measurement. The measured frequency responses of the dielectric constants of several compounds are also shown in this paper. View full abstract»

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  • Pulsed‐Current Control and Measurement System for Precision Microcalorimetry

    Page(s): 766 - 774
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    Instrumentation for heat measurement in differential microcalorimetry is described in sufficient detail so the electronic apparatus can be built and used reliably with various calorimeters. Theory and calibration techniques are explained for calculating endothermic and exothermic heats from indicated digital data for reaction calorimetry and temperature scan calorimetry (including DTA). The cooler of twin calorimeter cells is heated electrically to counteract thermal effects of the system being measured. This heating is by pulses of current, all identical, whose rate of occurrence is controlled proportionally to the small residual intercell temperature gradient; counting pulses gives heat indication directly as numbers. The heat per pulse is known accurately, and the pulsed (indicated) heat is related to effects of the system under study; the relation is by a constant, near unity factor (such as 1.010) which can be calculated using easily measured calorimeter parameters. The factor is constant because heating is proportional to the residual temperature gradient, and differs from unity because of heat conduction through that gradient. Over‐all accuracy, experimentally confirmed, exceeds 0.1% and depends on well‐standardized electrical measurements, so calorimetric calibrations are not needed with calorimeters of known material capacity. Pulses, 16.666 msec long, occur at rates up to 30/sec and have switch‐selected amplitudes from 0.02 to 640 μcal per pulse (60 Ω heater). Equipment design includes devices for routine tests to detect component deterioration before it has become serious. View full abstract»

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  • Rapid Response Flow Microcalorimeter

    Page(s): 774 - 776
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    A flow microcalorimeter with rapid response (20 sec) and high sensitivity (10-8 μcal/sec detectability) is described. The design of the instrument permits easy construction. The operating temperature is determined by a liquid thermostat bath that can be set as desired. Typical test results are described. View full abstract»

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  • A Versatile Method for Digitizing the Information on Oscilloscope Photographs

    Page(s): 777 - 780
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    A simple and inexpensive technique is presented whereby the analog data on a photograph obtained in standard oscilloscope experiments may be digitized. The automatic system is much faster than manual digitizing when a large number of data points must be analyzed. It is also versatile enough to allow several levels of sophistication, depending on individual requirements of speed, accuracy, and expense. View full abstract»

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  • A Laser Flash Technique for Determining Thermal Diffusivity of Liquid Metals at Elevated Temperatures

    Page(s): 781 - 786
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    The laser flash technique has been frequently employed in many laboratories as a relatively fast and easy technique of modest accuracy for measuring the thermal diffusivity of solids at ordinary and elevated temperatures. We have refined this technique and extended it to measurements of the thermal diffusivities of liquid metals. In both solid and liquid metallic specimens we have found, on both experimental and theoretical grounds, that the accuracy of the results is very sensitive to the degree of uniformity of the laser pulse. By introducing appropriate optics between the laser and the specimen we have been able to obtain a very uniform laser pulse and thus considerably enhance the accuracy of our measurements. In particular in measuring the thermal diffusivity of liquid mercury at temperatures from 13 to 300°C the difference between our values and values derived from published results of steady state measurements was never more than 5%. A cinematographic study of the impact of the laser beam on the surface of the liquid mercury was also carried out. View full abstract»

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  • The Movable‐Junction Stationary‐Lead Thermocouple

    Page(s): 787 - 790
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    The construction and use of two special platinum/platinum‐rhodium thermocouples are described. One type of movable‐junction stationary‐lead thermocouple allows a substantial increase in the accuracy attainable in temperature gradient measurements in both fixed point (0–1100°C) and low gradient (≪1°C) zones over that possible with the conventional standard thermocouple, by circumventing the systematic error arising from the interaction of the variable thermopower of unavoidably inhomogeneous thermoelement wires with the entrance temperature gradient in the throat of a furnace. The second form of the movable‐junction couple permits the accurate determination of the immersion characteristics of each thermoelement of a couple in fixed point environments and therefore provides a ready means of measuring and studying the separate effects of cold‐working, quenching, heat‐treating, gaseous environment, etc., on the thermal emf of both the unit couple and its constituent elements. View full abstract»

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  • Correction of Single Photon or Particle Timing Measurements for Multiparticle Events

    Page(s): 791 - 796
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    In particle time of flight or photon timing measurements, usually only the first event can be timed. An algorithm is derived which uses the measured distribution of first arrivals and a measured or assumed distribution of events per sweep to generate the desired distribution of all arrivals. The theory is shown to work at all values of the average count rate per sweep by comparison with computer simulated experiments. It is found that the optimum recovery of information at long times occurs at an average count rate per sweep of 1. View full abstract»

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  • Rotational Temperature Measurement in Nitrogen Using Raman Spectroscopy

    Page(s): 796 - 799
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    The rotational temperatures at pressures near 1 atm have been successfully measured in pure nitrogen. The precision available, even with unsophisticated instruments, is adequate to allow local temperatures to be measured in a flowing gas with virtually no disturbance of the flowfield. Using a double monochromator and including the flowfield within the laser cavity would increase the signal and decrease scattered light. View full abstract»

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  • Method for Shock Wave Investigation of Magnetic Material

    Page(s): 800 - 804
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    An experimental method developed for investigation of shock induced demagnetization in yttrium iron garnet is reported. The method was found reliable and quite easy to implement. It has the potential of being a useful experimental tool for further investigation of magnetic properties in shock wave studies. View full abstract»

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  • In‐Line High Vacuum Conductance Valve for Shock Tubes

    Page(s): 804 - 805
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    A simple but highly efficient valve for shock tube evacuation is described. It is constructed as part of the shock tube with a diffusion pump attached beneath. When closed, the valve becomes part of the shock tube. When opened, the shock tube is evacuated to the attached pump. Results are presented to show improved pump‐down time and ultimate pressure. View full abstract»

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  • A Simple Recording Thickness Gauge

    Page(s): 806 - 807
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    An account is given of the construction and operation of a device which allows an Instron universal testing machine to produce a continuous autographic record of thickness or contour of specimens and small parts. This device has proven useful in the nondestructive measurement of irregular cross sections. 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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Meet Our Editors

Editor
Albert T. Macrander
Argonne National Laboratory