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Review of Scientific Instruments

Issue 12 • Date Dec 1978

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Displaying Results 1 - 25 of 41
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Internal calibration to absolute values in flowthrough particle size analysis

    Page(s): 1617 - 1621
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    Using a double‐beam technique, a laser flowthrough microphotometer is described that allows internal calibrated size measurements of particles and suspension without the need of reference measurements. Nonspherical particles are oriented in a single file and their longest axes are measured by light absorption analysis. Additional information may be derived from light scattering. The size range is limited only by the flow system, and spans from 2 to 300 μm within a single measurement at the present design. Particle and cell analysis can exceed the rate of 100 000/s. Latex microspheres were analyzed and the data compared to that from microscopic examination. An example of the cell classification obtainable is given for stored human blood. View full abstract»

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  • Low‐dissipation tunable rf preamplifier for low temperature NMR applications

    Page(s): 1622 - 1624
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    We describe a simple circuit which can be used as an impedance matching device to improve the S/N ratio when lossy cables must be used in low‐temperature NMR experiments. The total dissipation is less than 2 mW and the circuit operates satisfactorily down to 1.5 K. The only tuned circuit is the nuclear resonance circuit which incorporates GaAs (P) diodes which can be tuned remotely. View full abstract»

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  • Continuously recording refractive index spectrograph for transparent and opaque insulators and semiconductors

    Page(s): 1625 - 1628
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    An apparatus is described which enables the user to measure continuous refractive index spectra of opaque and transparent optically flat samples. The method of measurement is based on finding the Brewster’s angle βB of the sample. By modulating the angle of light incidence, the output signal of a lock‐in amplifier, tuned to the modulation frequency, changes sign abruptly at βB. The lock‐in signal is applied to a dc motor which drives a goniometer in that way that the sample is continually held at βB. Provided that the sample extinction coefficient k≲0.5, the accuracy of the refractive index measurements is better than 1%, or even 0.1% where k≈0. View full abstract»

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  • Coupled Marx–Tesla circuit for production of intense relativistic electron beams

    Page(s): 1629 - 1630
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    A two‐stage Marx circuit was built and is used to multiply the input energy of our Tesla resonant transformer accelerator without missing resonance conditions. The present output characteristics of our coupled Marx–Tesla circuit are compared to those of the previous Tesla transformer. With the same input voltage and cathode to anode distance, we succeeded in doubling output voltage and current of the beam. View full abstract»

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  • High‐power, high‐repetition rate pulser for photo‐impulse ionized lasers

    Page(s): 1631 - 1636
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    The design and operational parameters of a high‐power pulser suitable for a photo‐impulse ionized laser are presented. The relatively compact device utilizes a ceramic thyratron in a triggered resonant charging circuit. Efficient operation at repetition rates up to 40 kHz, with pulsed powers in excess of 2 MW and average powers of several kilowats has been achieved. View full abstract»

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  • Nanosecond gating of an optical multichannel analyzer

    Page(s): 1637 - 1641
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    An optical gating pulse of 30 ns width combined with an electronic gating pulse of 50 ns width has been found to give a near perfect performance of a gated silicon intensified vidicon detector. The magnification as well as the focusing properties are found to be close to the real‐time behavior and the small changes that do occur in the gated mode can be corrected for in the data analysis. View full abstract»

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  • Grazing incidence spectrograph–monochromator for xuv spectroscopy in the 5–900 Å region

    Page(s): 1642 - 1646
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    A combination grazing incidence spectrograph for photographic recording and scanning monochromator has been realized. The instrument is of a modular concept and all the internal components like the grating, the plateholder, and the scanning exit slit are easily removable. The radius of curvature of the Rowland cylinder can also be easily changed. The entrance beam is always kept fixed in position and direction, allowing the instrument to be permanently aligned with fixed light sources. The vacuum case is mechanically independent from the optical components. View full abstract»

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  • Parts‐per‐million water vapor generating system used to simulate moisture in small integrated circuit packages

    Page(s): 1647 - 1649
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    A simple, portable system has been developed and tested for generating a known water–vapor content is selected permanent gases or gas mixtures. Parts‐per‐million values ranging from 250 to 20 000 are generated in a continuous flowing stream at flowrates ranging from 50 to 200 cm3/min. A known volume of the flowing gas can be selected to simulate the internal free volume and internal pressure of hermetically sealed packages as small as 0.04 cm3. By using a variety of available connectors, the selected volume of gas may be transferred into the inlet system of a mass spectrometer for water–vapor calibration. Generator stabilizing time and upper flowrate limits are given along with test results when compared to a Transfer Humidity Standard. View full abstract»

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  • Electronic micropositioning with ferroelastic–ferroelectrics

    Page(s): 1650 - 1652
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    The change in crystal shape which accompanies domain wall motion in a coupled ferroelastic–ferroelectric crystal such as β‐gadolinium molybdate can be utilized for precise micropositioning under electronic control. The displacement available from such a crystal is 10 to 100 times greater than a piezoelectric element of similar dimensions can provide. View full abstract»

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  • Mass/thickness detector employing inexpensive integrated circuits

    Page(s): 1653 - 1657
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    Modern integrated circuits have made possible the construction of a simple and inexpensive quartz crystal mass/thickness monitor having high sensitivity and good resolution. We have constructed such a thickness monitor having a resolution of 0.1 nm for evaporated lead films. This same device can also be readily made to function as a microbalance capable of resolving mass changes as small as 1 ng. View full abstract»

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  • Development of a laboratory EXAFS facility

    Page(s): 1658 - 1666
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    The EXAFS technique is a powerful new structural tool, particularly useful for studies of disordered or otherwise complex materials for which x‐ray diffraction techniques are difficult or unfeasible. At the present time, most EXAFS experiments are carried out at a synchrotron facility because of the larger fluxes available. We have developed an in‐laboratory apparatus utilizing a focusing crystal technique which increases available fluxes two to three orders of magnitude over previous laboratory facilities, so that EXAFS measurements can be carried out quickly and accurately in the laboratory. We will discuss the principles of the focusing monochromator and we will also illustrate the experimental method with examples, including studies of chemical solutions, defect crystalline solids, and high‐temperature superconductors. View full abstract»

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  • X‐ray reflectometer for optical efficiency and scatter measurements

    Page(s): 1667 - 1669
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    An instrument has been developed to determine the reflection efficiency and scatter characteristics of optical samples at x‐ray wavelengths from 1.5 to 113 Å. The reflectometer operates in an oil‐free vacuum chamber and measures the reflection efficiency and scatter characteristics as a function of the angle of incidence. The reflection efficiency is given for λ=8.34 Å incident on a fused silica sample finished to a flatness of λ/10. The experimental reflection efficiency is compared to the theoretical data. The scatter curves are given for the direct x‐ray beam and for the beam reflected from the fused silica sample at ϑ=50 arc minutes. The full‐width‐at‐half‐maximum (FWHM) resolution of the instrument is approximately 13 arc seconds as determined by a least‐squares smoothing of the experimental data. View full abstract»

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  • Continuous radon concentration monitoring

    Page(s): 1670 - 1674
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    The use of ionization chambers to continuously monitor the concentration of radon dissolved in ground water is described. In one case, air is bubbled through the water sample to strip the radon into the chamber. In a second operating mode, the sample water itself is flowed through the chamber. Support electronics systems are described for remote and urban applications. View full abstract»

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  • Simple cell for the measurement of the radio frequency electrical properties of earth materials

    Page(s): 1675 - 1679
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    The design of a simple cell for determining the radio frequency electrical properties of earth materials is described. Basically, the cell consists of a coaxial sample holder fitted with electric and magnetic field probes. When excited as a section of transmission line the induced probe voltages are related in a straightforward manner to the electrical properties of the sample. The device is intended for use with a vector voltmeter which permits the direct and simultaneous measurement of the relative amplitudes and phases of these probe voltages. The cell permits the accurate and rapid determination of the conductivity and dielectric constant of earth materials over the frequency range 1 MHz–1 GHz, without the tedious and time consuming procedures associated with the bridge and slotted line techniques commonly used in this frequency range. View full abstract»

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  • Modified apparatus for low temperature/high pressure Mössbauer absorber studies

    Page(s): 1680 - 1681
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    A method is described in which a system designed to study Mössbauer sources as a function of pressure and temperature is modified to include absorbers as well. This is accomplished by coupling the Mössbauer source, mounted inside a cryostat, to an external transducer by means of a bellows. In addition, a simple modification has converted an existing helium Dewar to a dynamic gas flow cryostat. Temperature can be continuously varied from 300 to 20 K at pressures up to 200 kilobars. View full abstract»

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  • Prism beamswitch for radio telescopes

    Page(s): 1682 - 1683
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    A dielectric prism and switching mechanism have been constructed for beamswitching a Cassegrain radio telescope. Spatially extended radio sources may be mapped without significant confusion utilizing the sensitivity and stability inherent in the conventional Dicke radiometer. View full abstract»

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  • Temperature‐compensated induction extensometer

    Page(s): 1684 - 1687
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    A linear displacement transducer, or extensometer, has been designed and constructed to measure displacements over a range of 0–150 mm. The transducer works by electromagnetic induction and consists of a bifilar coil coaxial with two conducting cylinders, one inside and the other outside the coil. The induction extensometer has been designed to eliminate errors caused by temperature changes from 0° to 1000°C. Experimental measurements show an error of 1 mm over the 150‐mm displacement range for a temperature change of 500°C, and the error should not be larger over the full 1000°C temperature range. The displacement range can be varied from 2.5 to 250 mm by scaling the entire experiment up or down, and the temperature compensation can be made for any temperature range that is compatible with the constructional materials. View full abstract»

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  • Improved resolution in fixed‐wavelength photoelectron–photoion coincidence spectroscopy

    Page(s): 1688 - 1690
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    The paper describes a technique of extraction‐field pulsing, whereby the energy resolution in fixed‐wavelength photoelectron–photoion coincidence spectroscopy can be substantially improved and extended light sources can be used. View full abstract»

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  • Multichannel audio monitor for detecting electrical signals

    Page(s): 1691 - 1693
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    The multichannel audio monitor (MUCAM) permits the simultaneous auditory monitoring of concurrent trains of electrical signals generated by as many as eight different sources. The basic working principle of this device is the modulation of the amplitude of a given pure tone by the incoming signals of each input channel. The MUCAM thus converts a complex, multchannel, temporal signal sequence into a musical melody suitable for instant, subliminal pattern analysis by the human ear. Neurophysiological experiments requiring multi‐electrode recordings have provided one useful application of the MUCAM. View full abstract»

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  • Microprocessor assisted real‐time harmonic analysis by minicomputer

    Page(s): 1694 - 1697
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    A real‐time signal averaging and harmonic analysis technique for low audio frequency waveforms is described that, although based on based on earlier software emulations of lock‐in detection instruments, eliminates problems inherent in the earlier systems. Parallel processing is employed between a data acquisition minicomputer (HP‐2116B) and a microcomputer (Z‐80) to (1) replace an earlier chopper‐type lock‐in algorithm with a coherent Fourier transform, (2) digitally produce a pure (0.01% THD) modulation sine wave, (3) simplify system tune‐up, and (4) produce a high‐quality, flicker‐free, real‐time display of the averaged waveform and its harmonic content. View full abstract»

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  • Electrical noise measurements using a microprocessor‐based system

    Page(s): 1698 - 1701
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    A microprocessor‐based system for measuring low‐frequency (less than 100 Hz) electrical noise power spectra is described. The main function of the microprocessor was to determine the noise autocorrelation function using simple ’’one bit’’ autocorrelation arithmetic, subsequent Fourier transformation to find the power spectra being done on a larger computer. Given that such larger computing facilities already exist, this system is much less expensive than more conventional analogue techniques. We illustrate the way in which this system was implemented to measure current noise in insulating polymers. View full abstract»

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  • Real‐time phase microscopy using a phase‐lock interferometer

    Page(s): 1702 - 1705
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    A phase‐lock interference microscope (PLIM) has been designed and constructed. The instrument measures optical phase in real time with analog output voltages proportional to phase and position. The PLIM has been used to measure gradient index profiles in optical fibers, wall thicknesses of microballoons for laser induced fusion, the phase of biological specimens, and the surface finish of optical surfaces. The peak‐to‐peak noise of the instrument is λ/50. View full abstract»

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  • Two‐way ESR cavity for magnetic‐ and electric‐dipole transitions

    Page(s): 1706 - 1708
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    A two‐way ESR cavity for magnetic dipole transition (MDT) and electric dipole transition (EDT) was manufactured. There are two openings to fit the sample cell for MDT or EDT in the cylindrical TE011 mode. One opening is located on the axis of the cavity and the other is located away from the axis. The ESR spectra of the mixture of oxygen and nitrogen oxide obtained when the sample cell was inserted in each of the openings showed the selective transition of the MDT or of the EDT of the species. View full abstract»

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  • Compact sensitive instrument for direct ultrasonic visualization of defects

    Page(s): 1709 - 1711
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    A simple ultrasonic imaging cell based on the confocal combination of a plano‐concave lens and a concave spherical mirror is described. When used in conjuction with a stroboscopic schlieren visualization system, it has the main attributes of a practical nondestructive testing instrument: it is compact, relatively inexpensive, and simple to operate; its sensitivity is fair, resolution and fidelity are good; it has a fairly large field of view and a test piece can be readily scanned. The scope of its applicability is described and discussed. 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