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Review of Scientific Instruments

Issue 5 • Date May 1984

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Displaying Results 1 - 25 of 33
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Microminiature refrigeration

    Page(s): 661 - 680
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    We present a review of the recently developed microminiature, Joule–Thomson cryogenic refrigerators. These extremely small devices are finding wide scale use in instrumentation and as coolers for the study of materials. They have recently become available through the development of a novel, low‐cost photolithographic fabrication process. We present the essentials of heat exchanger design, upon which the refrigerators are critically dependent, discuss the fabrication process, and review some of the present applications and limitations of the refrigerators, together with possible future application for cooling SQUID devices. View full abstract»

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  • Extraction of H- beams from a magnetically filtered multicusp source

    Page(s): 681 - 686
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    H- ions produced by volume processes have been extracted from a multicusp source operated with a magnetic filter and accelerated to form a high‐quality beam. It was found that the H- beam current increased almost linearly with the discharge current. An H- ion current density of 38 mA/cm2 was obtained with a discharge current of approximately 350 A. The accelerated beam was mass analyzed and the emittance of the H- component was measured. The electron component and the percentage of ion impurity in the extracted beam were also determined. View full abstract»

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  • Fast chopped neutral beam technique for measurement of central ion temperature and central neutral atom density on the WEGA Tokamak

    Page(s): 687 - 695
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    This paper describes some details and results of an active neutral beam diagnostic mounted on the WEGA Tokamak and used in conjunction with a single‐channel neutral particle energy analyzer. The beam diagnostic permits temporal resolution over a 40‐ms interval of the Tokamak discharge during which lower hybrid heating is applied. The central ion temperature was measured to be 270 eV before heating and 340 eV during 178 kW of heating. In addition, the central neutral atom density was deduced from experimental results to be (1.5±1)×1014 m-3 using this active measurement technique. The relative efficiency of the charge‐exchange analyzer measured using the active beam is in good agreement with independent calibration. View full abstract»

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  • Core‐level electron–electron coincidence spectroscopy

    Page(s): 696 - 711
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    Two electron‐spectrometer systems designed for electron–electron coincidence spectroscopy are described. One, based on two hemispherical analyzers and x‐ray excitation, is especially suited for Auger‐photoelectron coincidence spectroscopy (APECS) of solids and surfaces. The other, using a cylindrical mirror analyzer, a hemispherical analyzer, and electron‐beam excitation is designed for near‐dipole (e, 2e) spectroscopy of gaseous samples. Typical results obtained with these instruments are presented. View full abstract»

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  • Broadband, high‐power, millimeter‐to‐centimeter spectrometer

    Page(s): 712 - 715
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    A simple spectrometer is described for directly measuring both a high electric field (0.1–100 kV/cm) and wavelength over a broadband (0.1–10 cm). The combination of interference and gas breakdown are utilized in measuring the electric field and wavelength. Electron diffusion and the characteristic breakdown relation limit resolution of submillimeter wavelengths by requiring very high electric field (≫100 kV/cm). View full abstract»

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  • Surface fluctuation spectroscopy: A novel technique for characterizing liquid interfaces

    Page(s): 716 - 726
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    Surface fluctuation spectroscopy is a dynamic light scattering technique which involves the detection of thermal fluctuations (capillary waves) that cover every liquid interface. The advantages of this technique over conventional mechanical methods are discussed. The signal resolution and precision are improved by using a grating heterodyne technique coupled with a digital correlator. Detailed calculations showed that, for the measured power spectrum (the Fourier transform of the correlation function) to take the Lorentzian shape, it is necessary that certain optical conditions be met. These conditions are demonstrated with experimental data collected for ethanol at the ambient temperature as a function of the wave number. Once the optical parameters are adjusted correctly, the experimental results show excellent agreement with the literature values. We have also demonstrated that, using microcomputer technology, the entire system can be automated. The instrument is easy to operate and can be used either for research purposes or on a routine basis. The implication of this instrument as a powerful analytical tool for a wide spectrum of liquid interfaces is also discussed. View full abstract»

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  • Surface fluctuation spectroscopy: Comments on experimental technique and capillary ripple theory

    Page(s): 727 - 731
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    We comment on several aspects of the light scattering technology that have been developed in our laboratory. In particular we show that Shih’s [Rev. Sci. Instrum. 55, XXX (1984)] data is consistent once beam propagation is taken into account fully and a small error in the grating constants corrected. The result is that we can make a stronger statement concerning the correspondence between theory and experiment for both the center frequency and width of the spectrum of capillary wave fluctuations at the liquid/vapor interface. We discuss questions of optimal design of the optical system and detection system for these measurements. We collect a set of dimensionless groups that are useful for the design of experiments. View full abstract»

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  • Versatile temperature controller for the investigation of surface phenomena

    Page(s): 732 - 736
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    The design, construction, and performance of a stable temperature controller specifically built for surface studies is described. The controller can be operated either manually as an independent unit or automatically while interfaced to a digital signal analyzer, a computer, or an external programmer. Problems arising from the magnetic field generated by sample heating current are eliminated, allowing detailed studies of surface phenomena by electron spectroscopies over a wide range of temperatures and electron energies. View full abstract»

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  • Processor operated correlator with applications to laser Doppler signals

    Page(s): 737 - 742
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    A 64‐channel correlator is designed with application to the processing of laser Doppler anemometry signals in the range 200 Hz to 250 kHz. The correlator is processor operated to enable the consecutive sampling of 448 correlation functions at a rate up to 500 Hz. Software is described to identify a Doppler frequency from each correlation and the system is especially designed for transient flow signals. Doppler frequencies are determined with an accuracy of about 0.1%. View full abstract»

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  • Design of Faraday rotators and modulators

    Page(s): 743 - 746
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    Equations have been developed which allow the design of coils for Faraday rotators. It is shown that the sensitivity of rotation of the plane of polarization to the ampere turns of the coil is a function of ratios of coil dimensions. Equations and graphs are presented which allow the design to be optimized with respect to the power dissipated in the coil or to the temperature rise of the coil. It is shown that disk‐shaped coils are inefficient as rotators. View full abstract»

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  • Single axis photoelectronic autocollimator

    Page(s): 747 - 750
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    Several single axis, diffraction limited, monolithic autocollimators, capable of resolving less than 10-3 arc s have been designed and built. Their features include small size, lightweight, ruggedness, and ease of operation. Construction features and performance levels are given. View full abstract»

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  • Flexible detection optics for light scattering

    Page(s): 751 - 753
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    We have designed and built a compact, modular apparatus for the collection, viewing, and detection of scattered light for less than $1200, based on a commercially available optical bench. The novelty of our instrument is that it has the flexibility of modular design while allowing the user to see exactly what is happening: both the real image of the sample and the spatial coherence of the scattered light can be examined. There is built‐in control over polarization, filtering, magnification, and other parameters. View full abstract»

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  • Apparatus for measuring Seebeck coefficients of high‐resistance semiconducting films

    Page(s): 754 - 760
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    An apparatus is described for measuring Seebeck coefficients in semiconducting thin‐film samples with resistances as high as 1011 Ω. A temperature gradient ΔT is produced across the sample by means of differential optical heating of the ends of the sample. The Seebeck voltage ΔV is measured using a specially designed amplifier circuit with an input impedance of 1013 Ω. The Seebeck coefficient is obtained from the slope of the plot of ΔV vs ΔT. View full abstract»

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  • Calibration of ac susceptometer for cylindrical specimens

    Page(s): 761 - 764
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    The absolute magnetic susceptibility of cylindrical specimens is obtained with an ac susceptometer whose calibration is based on a calculation of mutual inductance. An axially magnetized cylinder is modeled as a solenoid of the same size. The mutual inductance between such a solenoid and a pickup coil of arbitrary dimensions is computed. The susceptibility is then a function of the mutual inductance, the cylinder length, the magnitude and frequency of the ac magnetizing field, and the voltage induced on the pickup coil. Demagnetization factor and eddy‐current effects are considered, an example is given, and pickup coil compensation is discussed. Other calibration methods are also presented. View full abstract»

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  • Steady‐state gas dissolution flow microcalorimeter for determination of heats of solution of slightly soluble gases in water

    Page(s): 765 - 772
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    A flow calorimeter of the heat conduction type is described, which is capable of measuring the heat effect associated with the process of dissolving slightly soluble gases into water. The calorimeter operates in a steady‐state mode. Gas, fed at constant rate, is dissolved in flowing water within a specially designed microcalorimeter cell and the power is determined for the process. Computer control of the gas flow is used for convenient establishment of steady states. The calorimeter is calibrated electrically with a precision of 0.2% for power levels of 150–450 μW. Reproducibility of successive measurements of heats of solution of oxygen are within 1%. Results are presented for the enthalpy change for the dissolution of oxygen gas into pure water at 25 °C. View full abstract»

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  • Hot‐stage for in situ operation of a battery in a scanning electron microscope

    Page(s): 773 - 777
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    A hot‐stage assembly has been designed, built, and operated inside a scanning electron microscope to observe and study the electrode–electrolyte interface behavior of a sodium–sulfur cell. This device has demonstrated the possibility of direct observation of the sodium evolution process onto the surface of a sodium beta″‐alumina electrolyte. The results illustrated the wetting behavior of liquid sodium with the electrolyte surface and the dynamic behavior of liquid sodium evolution processes. View full abstract»

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  • High‐temperature, cyclic‐loading stage for the scanning electron microscope

    Page(s): 778 - 782
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    A stage for the ETEC Corp. SEM has been designed and constructed, which is capable of cyclicly loading a specimen up to 4000 N at temperatures up to at least 750 °C. The specimen is symmetrically loaded so that it may be observed dynamically under high resolution. Loading frequencies from static up to 4 Hz may be used, with a resolution of about 50 nm on the specimen for static loading and 100 nm for dynamic (TV scan rate) observation in the secondary electron mode. Load is applied with a closed‐loop, servocontrolled hydraulic system. Heating is by resistive elements surrounding the specimen grips. Extensive radiative shielding is used for heat containment, with leakage extracted by liquid cooling of the pull rods and outer shielding. View full abstract»

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  • Gain characteristics of a microchannel plate operated in the reflection mode for low‐energy positive ions

    Page(s): 783 - 785
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    Fundamental gain characteristics of a microchannel plate (MCP) operated in the reflection mode for low‐energy (20–300 eV) positive ions were studied experimentally in detail. When a MCP with zero‐bias angle was used, the gain in the reflection mode increased by about two orders of magnitude compared with that in the conventional transmission mode. Such a remarkable high gain supports the automatic preacceleration effect on incident ions suggested previously and also shows practical usefulness of this operation mode as a simple detector of low‐energy positive ions. The reflection mode gain was also found to be highly sensitive to the ion’s incident angle and collector voltage. This suggests that the reflection mode has two additional functions: that of analyzer of the incoming ion’s direction and discriminator of incident ion energies. These properties can be explained in terms of the penetration depth of incident ions into the microchannels, which is the most important factor in this detection technique. View full abstract»

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  • Electrohydraulic gas sampling valve

    Page(s): 786 - 792
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    An electrohydraulically actuated gas sampling valve is described for use in reciprocating IC engine combustion studies. The design objectives achieved include: short sampling interval, 0.4–1.0 ms; variable valve lift range, 0.01–0.3 mm; and large sealing force capability to retain a gas tight seal when the valve is closed. The present configuration has flush seating geometry of the valve stem to valve seat to permit accurate boundary layer probing without perturbation of the sample region before the time of sampling. When coupled to a gas chromatograph or another measurement device, species concentrations can be measured at various times in the combustion cycle. Use of the valve in engine combustion studies has provided new experimental insight indicating that flame‐wall quenching is not an important contributor to exhaust hydrocarbon emissions as once believed. View full abstract»

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  • Fabrication and leak‐tight furnace brazing of intricate objects

    Page(s): 793 - 795
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    An extremely compact crossflow heat exchanger has been constructed by hydrogen furnace brazing together a stack of hundreds of chemically milled stainless‐steel sheets. The resulting structure is leak tight and very strong, but fluid channels as small as 51 μm are not plugged by excess brazing material. The construction technique is easily adapted to mass production and should be useful for structures of an intricate but repetitive three‐dimensional nature. View full abstract»

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  • Isolation and inversion transformers for nanosecond pulses

    Page(s): 796 - 800
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    In the transmission‐line approach to the design of transformers, a harmful mode of signal propagation that inevitably appears outside the transmission line has to be taken into account. The effect of this mode upon the output signal was studied theoretically and experimentally using a simplified model. With respect to the use of ferrite beads for suppressing the effect of this mode, a simple rule was derived for their effective use. According to the result obtained, isolation and inversion transformers were made for a test. The result of the test is given. View full abstract»

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  • Simple water‐cooled mirror for high‐power lamps

    Page(s): 801 - 802
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    A mirror is described which endures illumination levels approaching 1 MW m-2. It has high reflectivity (≫90%) and does not deteriorate even after several hours exposure to high illumination levels. It is inexpensive and easily replaced in the event of damage. View full abstract»

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  • Note on the design of simple indium O‐ring seals

    Page(s): 803 - 805
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    Various different applications of indium O‐ring seals are briefly reviewed. A critical factor in the construction of any indium pressure‐type seal is the finish of the surface cold welding to the indium. We present the results of some tests on surface finishes achieved by machining and grinding, which indicate certain conditions which ensure the integrity of the seal. Specifically, we find that if the metal surface has to be ground, it should be ground, and then polished to a surface granularity of less than 5  μ. This condition can be obtained using a grinding powder with a mesh size of 3200 or greater. Alternatively, careful surface preparation using a lathe furnishes an equally satisfactory finish, provided no attempt is made to ‘‘improve’’ the surface using emery paper, etc. In the latter case, the fine helical pattern imparted by the lathe is essential for the fabrication of a reliable seal. View full abstract»

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  • Turbine drive sample spinner for x‐ray diffraction

    Page(s): 805 - 806
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    A new sample spinner is described which is driven with a jet of air or other gas. The spinner features ease of mounting, rapid sample changing, and the ability to run at high revolutions per minute. The reproducibility of intensities with successive specimen remounting is better than 1%, and the standard deviation of d spacings measured for the 11 silicon peaks is 0.0005 A. 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