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Review of Scientific Instruments

Issue 10 • Date Oct 1982

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Displaying Results 1 - 25 of 34
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • High‐power neutral deuterium beam species measurement by neutralizer fusion product analysis

    Page(s): 1513 - 1516
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    Energy spectra of charged fusion products produced by 105‐keV deuterium ions in a deuterium gas target are measured and used to infer the proportions of full, half, and one‐third energy deuterons extracted from the accelerator. View full abstract»

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  • Electron flow through transverse magnetic fields in magnetic multipole arc discharges

    Page(s): 1517 - 1522
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    Magnetic multipole sources have been shown to produce very quiescent plasmas. As a result, the experimental measurements of the diffusion of electrons across transverse magnetic fields in the source show that it obeys the scaling laws generated by collisions of the long‐range coulomb type. The absolute flux of electrons is compared with the theoretical value derived from a model of cross‐field diffusion arising from coulomb collisions. View full abstract»

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  • Electron cooling in magnetic multipole arc discharges

    Page(s): 1523 - 1526
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    Internal magnetic structures or filters, which enhance the proton yield in magnetic multipole sources, also modify the electron temperature near the ion extraction electrodes. Results are presented for an electromagnetic filter which reduces the electron temperature by up to a factor of four. These measurements are in close agreement with a theoretical model based on the classical diffusion of particles and energy through the magnetic field of the filter. View full abstract»

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  • Bolometer for measurements on high‐temperature plasmas

    Page(s): 1527 - 1534
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    A bolometer has been developed based on a thin, die‐cut platinum grid. It can survive high temperatures and the neutron and gamma radiation expected in the Toroidal Fusion Test Reactor (TFTR). The platinum resistance is measured with a square‐wave carrier system to minimize sensitivity to ambient electromagnetic interference. Electrical power fed back to the sensor holds its temperature constant and provides an output directly proportional to absorbed radiation power. With a bandwidth of 50 Hz the noise is equivalent to 100 μW/cm2. Methods are described for dealing with the background effects expected to contribute to bolometer heating. View full abstract»

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  • Multimixer far‐infrared laser Thomson scattering apparatus

    Page(s): 1535 - 1540
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    A detailed description of the design and calibration of a multimixer far‐infrared scattering system for the study of collective plasma density fluctuations is presented. The apparatus permits either the determination of single‐shot wave dispersion data or angularly resolved scattering data at multispatial locations during a single plasma discharge. Typical scattering data from spontaneously occurring low‐frequency microturbulence as well as from kinetic Alfven waves (generated during ICRF heating) in the UCLA Microtor tokamak are presented. View full abstract»

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  • High‐impedance capacitive divider probe for potential measurements in plasmas

    Page(s): 1541 - 1543
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    It is often desirable, though difficult, to measure electric potential changes within a plasma, including variations due to waves and fluctuations. For a broad range of plasma parameters ac floating potential measurements may be made using the high input impedance probe described in this paper. A capacitive divider with an active buffer circuit is incorporated, such that a 50‐Ω line can be driven with a 60‐dB dynamic range and 100‐MHz bandwidth. Details of the electronic circuit, mechanical construction, and calibration of the probe are given, together with a discussion of the parameter range over which successful measurements may be made. View full abstract»

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  • Waveguide laser using a curved grating

    Page(s): 1544 - 1546
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    A curved grating was introduced into the cavity of a glass tube waveguide laser. This replaces the commonly used lens–flat grating configuration and facilitates the operation of the laser system. Several positions of the grating are possible and allow the design of a more compact cavity. The performance is comparable to that of conventional cavities. View full abstract»

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  • Generation of synchronous, continuously tunable high‐power picosecond pulses

    Page(s): 1547 - 1549
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    A system of synchronously pumped dye lasers is described that can produce 2 MW, nearly transform limited pulses of 15 ps duration. The two lasers are independently tunable between 550 and 710 nm with a bandwidth of 2 cm-1. View full abstract»

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  • High‐resolution ν1 spectrum of propyne: Application of a microcomputer‐controlled infrared‐acoustic color center laser spectrometer

    Page(s): 1550 - 1551
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    Development of a microcomputer‐controlled infrared‐acoustic color center laser spectrometer capable of scanning in 100 cm-1 sections over the wavelength range 2.2–3.3 μm with a resolution of 0.01 cm-1 (300 MHz) is reported. Application of the spectrometer to investigation of the ν1 spectrum of propyne is demonstrated. View full abstract»

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  • Infrared laser microwave double‐resonance spectrometer with a high‐precision multipass stark cell

    Page(s): 1552 - 1557
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    A spectrometer for infrared microwave double resonance with an intense Stark field is described that is useful for accurate determination of dipole moments and other electric properties of molecules. High precision and sensitivity are attained by the use of gold‐coated glass optical‐flat Stark plates, a white‐type multiple reflection optical path, and microwave frequency stabilization. The spectrometer was tested by observing double resonances in H2CO with a CO laser as an infrared light source, and was shown to be adequate for measurement of dipole moments to better than ±10-4D. View full abstract»

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  • Dual polarization quasi‐optical beam divider and its application to a millimeter wave diplexer

    Page(s): 1558 - 1560
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    A dual‐polarization wire grid beam divider has been developed. This beam divider features simultaneous uniaxial dual‐polarization operation, broad instantaneous coupling bandwidth, beam wave front preservation, and ease of fabrication. This paper describes a beam divider for 95 GHz, gives construction details, and presents a dual‐polarization local oscillator injection diplexer as a typical example of a beam divider application. View full abstract»

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  • Mosfet high‐power pulsed rf emitter—a design for nuclear‐magnetic‐resonance imaging

    Page(s): 1561 - 1565
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    We present a 350‐Wrms pulsed emitter based on a single Mosfet device working with square‐wave driven Class C. By tuning one single resonant circuit in the drain load, its operating frequency may be placed anywhere up to 15 MHz. With currently available Mosfet devices, the output power may be upgraded to several kW. This emitter also features sharp rf pulse edges, extremely high noise immunity, and provision for pulse envelope modulation. It is well suited for applications such as broadband nuclear magnetic resonance, especially if medical imaging is considered. View full abstract»

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  • Unified approach to photographic methods for obtaining the angles of incidence in low‐energy electron diffraction

    Page(s): 1566 - 1572
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    An equation is developed to describe the geometrical relationships between the electron gun, the crystal surface, and the phosphorescent display screen in back‐reflection, post‐acceleration LEED experiments. Photographic methods for determining the polar and azimuthal angles of incidence in LEED experiments can be derived starting from this equation. In particular, two published procedures appear here as special cases. New methods are described for cases where the existing techniques do not apply. It is shown that the alignment of the electron gun and the positioning of the crystal can be checked using a photographic technique. An example illustrates that the angles of incidence can be measured with precisions of ±0.2° by recording data on several photographs taken over a wide range in electron energy. View full abstract»

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  • Improved spectrometer for cathodoluminescence studies in scanning electron microscopy

    Page(s): 1573 - 1576
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    Some problems raised by studying defects in direct band‐gap semiconductors can be solved with the help of spectral cathodoluminescence in scanning electron microscopy. This led us to build a spectrometer fitted to a SEM. A fully catadioptric optical system maintains achromatism over the whole spectral range and four blazed gratings allow wavelength dispersion between 0.2 and 3.0 μm with a wavelength resolution of the order of 5 nm. The detection unit, depending on the emitted radiations, is quite easily interchangeable. View full abstract»

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  • Magnetically focused line source electron gun

    Page(s): 1577 - 1580
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    A magnetically focused line source electron gun for selective heat treatment of surfaces is described. A model calculation consisting of an electric field computation routine and a trajectory tracing procedure was performed. An electron gun, corresponding to the model, was built and tested and its characteristics measured. The gun delivered 10 kw/cm2 on a strip of 80×2 mm, which could be scanned over a range of 100 mm in a direction perpendicular to the long dimension of the strip, so that an area of 80×100 mm could be heat treated in a short time of the order of milliseconds. The magnetic focusing provides for uniform electron energy and beam density throughout the scanned area. View full abstract»

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  • Alpha particle collimator for micron‐sized beam

    Page(s): 1581 - 1585
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    A collimated alpha source is constructed from a drawn glass microcapillary and a plated polonium wire source. The shape of the capillary is approximately Gaussian, allowing an analytical model for the collimated flux intensity. The very gradual taper results in a nearly monochromatic beam. Two models are presented characterizing the particle flux intensity and its profile on a surface below the collimator tip. These models are experimentally verified using spectroscopy and isolated node mapping. Collimators having tip radii ranging from 5 to 25 μ have been successfully drawn and tested. View full abstract»

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  • Characterization of shock and reaction fronts in detonations

    Page(s): 1586 - 1591
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    An instrumental technique has been developed which allows the concomitant measurement of the arrival times of both shock and reaction (flame) fronts in propagating detonations. A combination of fiber‐optic probes and light detectors is used to monitor the arrival of the reaction front, whereas piezoelectric pressure gauges monitor the arrival of the pressure pulse from the preceding shock wave. Both signals provide the measurement of the detonation velocity; variance between shock and reaction front velocities implies nonstable detonation (growing or dying detonation) which can be attributed to variation in density, concentration, or homogeneity of the detonating media. This technique is straightforward in the case of pressed or cast formulations but presents difficulties when gas‐phase or two‐phase detonations are involved. The detonation of near‐stoichiometric ethylene–air mixtures in a detonation‐tube facility was used to refine the technique and calibrate the instrumentation. The technique was then used to characterize the detonation of two‐phase aluminum powder–air mixtures of various concentrations. Compared to the 3‐μs induction time between the shock and reaction fronts in the case of ethylene–air mixtures, the induction times for aluminum powder–air mixtures varied from about 1 to over 100 μs. The variation in induction time was attributed to several factors: extended heating time to ignition of the particles due to inhomogeneity of the two‐phase mixtures; variation in particle size; and variable aluminum‐oxide surface coating thickness. The concentration of aluminum powder in the air was monitored dynamically using instrumentation that related the concentration of aluminum to the attenuation of a laser beam through the mixture. A mean, or overall, value was also estimated by determining the mass flow rate and overall discharge time using ph- otographic coverage. In the former case, in order to obtain meaningful signals for these high‐concentration two‐phase systems it was necessary to reduce the pathlength of the laser beam through the mixture to a small fraction of the total width of the tube. Hence, the observed concentration measurements did not necessarily reflect good homogeneity across the width of the tube. Nevertheless, with some modifications this technique can be exceptionally useful for this most difficult measurement. View full abstract»

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  • Construction and testing of a high‐pressure joule‐heating temperature‐jump apparatus

    Page(s): 1592 - 1595
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    This paper describes the construction and testing of a high‐pressure joule‐heating temperature‐jump apparatus for the study of fast reactions in solution at pressures up to 2 kbar. Important features are: a liquid pressurizing medium; a Teflon membrane pressure transmitting device; a constant, pressure independent, electrode distance. The Co(II)‐PADA reaction was used to test the system, and the results are in good agreement with earlier reported data. View full abstract»

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  • Temperature‐jump apparatus with infrared detection for relaxation studies in thin samples

    Page(s): 1596 - 1601
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    A temperature‐jump apparatus with infrared detection is described, which has been developed for investigation of chemical reaction kinetics in electrically nonconducting systems: e.g., lipids, liquid crystals, and organic solutions. The sample (volume 8 μl) is attached on one side of a multireflection germanium‐ATR plate (ATR = attenuated total reflection). The two long edges of the plate are p and n doped in an alloying process and connected to electrodes. The plate can be heated in less than 50 μs by several degrees K with a capacitor discharge of 1.8 kV. The sample is heated by heat conduction. Changes in infrared absorption are detected with a liquid nitrogen cooled HgCdTe photoconductive device. The homogeneity of temperature distribution on the plate surface after the T jump has been verified with a thermographic video camera. Performance tests have been carried out with a liquid crystal by observing its melting process. View full abstract»

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  • Automated spectrometer for pressure measurement using ruby fluorescence

    Page(s): 1602 - 1603
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    A scanning fluorescence spectrophotometer intended for measurement of the ruby R1 lines in a high‐pressure diamond anvil cell is described. A rigid framework supports the electronic and optical components and an XYZ translation stage to hold the pressure cell. Innovations include a digital monochromator scan controller, the automatic placement of tick marks on the recorder output at 0.1 nm intervals, and light detection with a photodiode. The unit is compact, weighs 50 kg, and requires only a chart recorder for operation as an automated high‐pressure measurement station. These features allow easy shipment and reassembly at remote experimental sites. View full abstract»

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  • Direct reading, noise immune resistance comparator for measurement of temperature and pressure

    Page(s): 1604 - 1605
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    Design of a circuit intended for pressure measurement with a manganin cell in the range 0–10 kbar (1 bar = 105 Pa). The output voltage is strictly proportional to the difference between the cell resistance and a reference resistance, changes smaller than 0.1 mΩ in 100 Ω are detectable, and noise is negligible. A similar design may be used in resistance thermometry. View full abstract»

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  • Precision operational‐amplifier mutual inductance bridge for cryogenic thermometry and susceptibility measurements

    Page(s): 1606 - 1608
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    A mutual inductance bridge is described which employs operational amplifiers and a Kelvin–Varley divider in a configuration providing high precision and low noise. The linearity and stability of the bridge are approximately 10 ppm for the reactive part of the unknown mutual inductance in the frequency range 10–300 Hz. The noise is approximately 15 nV/√Hz. The bridge, built from readily available or constructed components, is suitable for cryogenic thermometry and ac susceptibility measurements. View full abstract»

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  • Large‐area, high‐sensitivity heat‐flow sensor

    Page(s): 1609 - 1612
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    A heat‐flow sensor based on ac resistance thermometry and utilizing synchronous detection is described. The sensor design permits large‐area sensors to be constructed economically. Calibration of an initial 0.09 m2 prototype yielded a linear response with a sensitivity of (37.610.01) mV(W/m2)-1. The minimum detectable heat flux is no larger than 0.08 W/m2. View full abstract»

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  • Reliable and simple method to measure relative changes of sound velocity automatically

    Page(s): 1613 - 1614
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    A method is described which allows one to measure, automatically, relative velocity changes as a function of an external parameter. The method utilizes standard electronic equipment and is based on pulse‐echo tracking by a sampling oscilloscope and an integrating amplifier. Its fast response time facilitates monitoring rapid velocity changes as occurring, for example, during the poling process of ferroelectric ceramics or at phase transitions, and relative velocity changes of the order of 10-5 can be detected easily. 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