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Review of Scientific Instruments

Issue 1 • Date Jan 1981

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Displaying Results 1 - 25 of 37
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Measurement of impurities in a long‐pulse, multiampere hydrogen beam

    Page(s): 1 - 7
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    Impurity concentration in intense neutral beams extracted from both a 75 keV/6 A/10 s duoPIGatron ion source and a magnetic multipole line cusp ion source has been measured by magnetic deflection mass analyzer. After passage of 90% equilibrium neutralizer cell, the ion beam contains 1%–2% light impurities (such as C+, O+, H2O) and 0.02%–0.15% heavy impurities (such as Cu+, W+, Ag+). Taking into account the neutralization efficiency, the neutral beam is estimated to contain 3%–6% light impurities and 0.04%–0.3% heavy impurities. The impurities related to oxygen decrease with time during a 10 s pulse, while those related to carbon, copper, and tungsten increase slightly with time. The origin of these impurities is discussed and the source operation mode to reduce the impurity level is proposed for neutral beam injection. View full abstract»

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  • Pulsed molecular beam source

    Page(s): 8 - 11
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    A pulsed molecular beam source has been developed using a conventional car fuel injector and an especially designed vacuum chamber. Beam pulses of about 150 μs duration (FWHM) and peak intensity better than 1020 mol sr-1 s-1 have been achieved for nitrogen. A simple model explaining the behavior and features of this source is proposed and a comparison with experimental data is presented. View full abstract»

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  • Plasma density measurements using FM–CW millimeter wave radar techniques

    Page(s): 12 - 15
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    Modified FM–CW radar techniques using swept millimeter–wave oscillators are useful for determining when a particular density has been reached in a plasma. Narrowband measurements on the Princeton Large Torus (PLT) demonstrate the suitability of these techniques for controlling high‐power auxiliary plasma heating systems. Broadband measurements using these same techniques are proposed, by which the density profile could be determined. View full abstract»

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  • Photoionization quantometer for absolute intensity measurements of vacuum ultraviolet and soft x‐ray radiation from laser plasma

    Page(s): 16 - 20
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    Design and parameters of the photoionization quantometer are given. It is a combination of photoionization chamber with time‐of‐flight mass spectrometer. The quantometer is an absolute detector of radiation in the wavelength interval (100–0.1 nm) due to the fact that photoionization and electron‐impact ionization cross sections of gases are used for absolute measurements. The quantometer is suitable for measurements of the number of photons in radiation pulses. The minimum number of photons detectable for a single pulse increases from 106 cm-2 puls-1 at 100 nm up to 1011 cm-2 puls-1 for 0.1 nm. The quantometer has been used for vacuum ultraviolet and soft x‐ray radiation measurements in the laser plasma experiment. An improved variant of the quantometer is presented which provides the absolute measurements of soft x‐ray radiation for laser plasma having continuous spectrum. The inaccuracy of measurements does not exceed 25% for soft x ray. View full abstract»

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  • Design of a hyperbolic microwave metallic lens

    Page(s): 21 - 23
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    Due to problems caused by multiple reflections in the cavity walls of the EBT fusion research device, the use of a horn becomes important for the directivity of waves in the millimetric range. An ordinary dielectric lens cannot be used because of plasma–wall interactions. Microwave metallic lenses, designed to focus the energy into a plane wave, can improve the directivity considerably. By implementing a 70‐GHz standard‐gain horn with a delay‐type hyperbolic lens, which consists of a solid metallic disk with a number of equal size small holes, a gain of 15 dB over the no lens case was realized. View full abstract»

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  • Design and calibration of a Thomson ion analyzer for plasma focus studies

    Page(s): 24 - 26
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    The construction of a mass and energy analyzer applicable for studies of ion streams generated by plasma focus facilities is presented. An appropriate ion extractor (skimmer) system is described. A simple calibration method of the device is also given. View full abstract»

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  • Simple apparatus for testing the line optical thinness in a free burning arc

    Page(s): 27 - 32
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    An optical system has been developed which allows measurement of light absorption at a given wavelength in the column of a free burning electric arc by comparison of the direct and back reflected light intensities. The difficulties arising from arc movements are avoided by using a corner cube reflector. View full abstract»

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  • Fabry–Perot cavity pulsed Fourier transform microwave spectrometer with a pulsed nozzle particle source

    Page(s): 33 - 45
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    We describe the design, construction, and operation of a new type of microwave spectrograph which allows the measurement of the resonant transitions of transient or otherwise short‐lived species. The spectrograph is composed of three parts: a Fabry–Perot cavity, a pulsed supersonic nozzle as a source for the sample, and the pulsed microwave Fourier transform method. Following a detailed discussion of the three above components in the spectrograph, the operation of the entire system is described and several examples are given. View full abstract»

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  • Digital inelastic electron tunneling spectrometer

    Page(s): 46 - 51
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    A computerized inelastic electron tunneling spectrometer designed for use in practical analyses is described. Spectra are obtained by measuring the first derivative of current vs voltagg using a first harmonic detection technique and then calculating the second derivative using a linear least squares fit of the first derivative segments. This method provides convenient qualitative and quantitative comparisons with conventional infrared spectra. View full abstract»

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  • Diamond anvil high‐pressure cell for Raman spectroscopy

    Page(s): 52 - 55
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    A design of a diamond anvil cell is described where a single crystal of sapphire is used for the backing of one anvil with the advantage of an enlarged aperture at an extended pressure range. The selection of diamond anvils with low luminescence at excitation with the Argon Ion laser is discussed. Procedures to control the stresses in samples at very high pressures are given and illustrated by Raman spectra of D2O. View full abstract»

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  • Improved technique in electron stimulated desorption ion angular distributions

    Page(s): 56 - 59
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    An improved technique for the measurement of ion angular distributions of electron stimulated desorption (ESDIAD) has been developed. The use of a chopped electron beam in connection with a gated detector system significantly reduces the background in the ESDIAD patterns. A comparison of experimental data obtained with the improved scan and the conventional display technique is presented. The essential advantages of the new method are increased sensitivity, low background, high‐angular resolution and ion energy determination at any desired point of the ESDIAD pattern. View full abstract»

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  • New principle of contactless lifetime determination in semiconductor wafers

    Page(s): 60 - 62
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    The principle of contactless determination of excess carrier lifetime or diffusion length in semiconductor wafers employs the magnetic flux created by the photomagnetoelectric (PME) current. Under certain conditions, the measured signal is nearly proportional to the lifetime according to a simple theory in which one‐dimensional diffusion is considered. Experimental verification of the theory is presented. A sample region of a few square millimeters is sufficient for lifetime determination and lifetime up to 10-7 s or less is measurable by the method. View full abstract»

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  • Apparatus with nanosecond field transition times for field reversal studies of surface processes at high temperatures

    Page(s): 63 - 67
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    A new type of field‐reversal apparatus is described. It is intended for desorption and surface reaction studies in systems with surface ionization. The problems of mechanically modulating the molecular beam are circumvented by instead reversing the electric field outside the surface and thus perturbing the steady‐state desorption conditions. The short field reversal time of ⩽ 10 ns with a 90 V voltage step is reached by using VMOS transistors with optoisolated driving circuits. The ions from the ionizing surface are converted to electrons on a Cu–Be dynode. The electrons give photons in a scintillator, and the photons are detected by a photomultiplier outside the vacuum wall. The apparatus dependent signal rise time is around 40 ns, which means that surface processes with very short characteristic time constants can be measurable. View full abstract»

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  • Externally quenched air counter for low‐energy electron emission measurements

    Page(s): 68 - 70
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    An air‐filled counter with two grids serves to detect and measure low‐energy electrons emitted into air from a solid surface. The grids are provided for quenching of a counter discharge caused by an incident electron, and for protection of a sample from positive ions produced during the discharge. The gridded counter operates well with the aid of electric equipments, e.g., amplifiers, pulse generators, and a scaling circuit. The air‐filled counter was then successfully applied to the measurements of photoelectron emission and exoelectron emission. View full abstract»

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  • Windows for x‐ray diffraction experiments

    Page(s): 71 - 74
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    The scattering properties of a number of substances potentially suitable as windows for x‐ray diffraction studies are measured. The study includes a variety of plastics, epoxies, and metal foils. Measurements are reported for a fixed target configuration such as is used in isotropic liquid studies over a range in scattering angles 2 °⩽Θ⩽75 ° for CuKα radiation. View full abstract»

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  • High‐temperature diamond‐anvil pressure cell for single‐crystal studies

    Page(s): 75 - 79
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    The miniature, single‐crystal, diamond‐anvil pressure cell of Merrill and Bassett [Rev. Sci. Instrum. 45, 290 (1974)] has been adapted for x‐ray crystallographic studies at sustained temperatures and pressures up to 450 °C at 30 kbar. View full abstract»

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  • Characterization of self‐heating effects in a superconducting bolometer with the superfluid helium film

    Page(s): 80 - 84
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    The static and dynamic response characteristics of a thin‐film aluminum superconducting transition‐edge bolometer are presented with particular attention paid to self‐heating effects. Criteria are developed for correct operation of the bolometer for heat‐pulse detection and ’’in situ’’ tests are presented to meet these criteria in a given experimental arrangement. The use of the superfluid helium film near its onset transition and the propagation of Third sound waves within this film are shown to aid greatly the characterization of the bolometer response. The results indicate that in order to guarantee correct bolometer response both heat‐pulse and static resistance measurements must be compared. View full abstract»

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  • Low‐shear, small volume viscoelastometer

    Page(s): 85 - 87
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    A simple viscoelastometer is described which can measure dynamic moduli in shear of less than 0.01 dynes/cm2 and requires a sample volume of less than 0.5 ml. The principle of operation is to follow the motion of a probe, generated by the tilting of the table on which it is mounted. The probe is suspended from a knife edge and generates a shear stress in the material. Calibration data using 100% glycerol is presented. View full abstract»

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  • Flow viscometer for solutions that make a glass wall water repellent

    Page(s): 88 - 94
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    A constant‐level viscometer has been designed especially for solutions that make glass water repellent. The lower meniscus remains at a constant level (±0.02 mm) during the flow period. Lower and upper meniscus corrections and the drainage error are discussed. It is shown that the performance of the viscometer is at least as good as that of the suspended‐level type for solutions that completely wet the glass wall, as KCl in water. For tetraethyl and tetrabutylammonium bromide solutions in water, this performance is free of the inaccuracies described in the literature. For Bu4NBr the relative viscosities measured at twelve concentrations in the range 10-4 to 160×10-4 M at 25°C, show a standard deviation of 0.01% about the best fit to the extended Jones–Dole equation. From these data the corresponding A coefficient has been determined, and found to agree with the value from theory. View full abstract»

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  • Ultrahigh vacuum specimen holder with rapid cooling mechanism

    Page(s): 95 - 97
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    A simple mechanism capable of rapidly cooling a specimen in ultrahigh vacuum (from 400°–185°C in a few minutes) is described. Its principle feature is that the specimen holder can conveniently be made to contact and separate from a liquid nitrogen (LN) reservoir. This allows the specimen both to be rotated at cooling temperatures and be heated at low LN boil‐off rates. The measured LN holding time with the specimen under experimental conditions reached about two hours and the temperature of the cooled specimen was kept constant (within a few degrees) even during its rotary movements. The mechanism can easily be combined with most rotary‐ and translational‐motion feedthroughs available commercially. Versatile modifications of the manipulating facilities are possible within the basic design principles. View full abstract»

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  • Fast‐closing vacuum valve for high‐current particle accelerators

    Page(s): 98 - 100
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    A fast‐closing vacuum valve for a high‐current particle accelerator was fabricated and tested. The 51 mm (2 in) ball valve is located in the accelerator beamline and closes within 5 ms if a vacuum loss is detected in the beamline. The valve is activated by a pressure‐rise detector that initiates a capacitor bank to discharge its current through two solenoids. The impulse force closes the valve and activates an air‐powered, cam‐type mechanism. This mechanism forces a diaphragm equipped with an O‐ring housing against the ball valve to produce a high‐vacuum seal in the beamline. The valve functions reliably and is simple to reset after each firing. Only the metal energy absorbers, which are deformed during valve closure, require replacement. Another desirable feature of this valve is that its inner body contour is essentially symmetrical to the beamline. Thus, the magnetic field produced by the large return current is symmetrical and does not deflect the particle beam. View full abstract»

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  • Temperature coefficient of the silica spring balance and estimation of errors in gravimetric adsorption measurements

    Page(s): 101 - 104
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    Silica spring adsorption balances were calibrated and temperature coefficients of the spring sensitivities were determined by a novel method. The method allows direct measurement of the temperature coefficient of torsional modulus of silica, which may depend on the type of silica from which the spring is constructed. By use of a first‐order Taylor series approximation, an approximate expression is derived for the variance of the quantity of vapor adsorbed per weight of solid (x/m). The expression points out certain experimental designs which may be altered to minimize the variance. Limitations in estimating the variance of x/m at low values of x/m are discussed. View full abstract»

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  • Microcomputer‐based gas chromatograph with IEEE‐488 interface

    Page(s): 105 - 109
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    A gas–chromatograph system controlled by a PET microcomputer is described. The system features twelve‐bit resolution, automatic sensitivity selection, and interfaces to a general purpose instrument bus commonly called the IEEE‐488 bus. The hardware of the interface is described in detail and uses only a few common integrated circuits. A sample chromatograph with retention times and peak areas is presented. View full abstract»

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  • On‐line display used with cathode ray tube film measuring device

    Page(s): 110 - 113
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    An improved display has been developed for use on our computer controlled measuring device (RIPPLE). The device features a television image of the film and a digital presentation on the same X, Y display. The television image is formed using a modified left and right raster scan which can cover 50% more area in the same time as the traditional raster. 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