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Jul 1966

Volume 37, Issue 7, pp. 819-977

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Techniques for Using Liquid Helium in Very Low Temperature Apparatus

O. E. Vilches and J. C. Wheatley

Rev. Sci. Instrum. 37, 819 (1966); http://dx.doi.org/10.1063/1.1720340 (13 pages) | Cited 21 times

Online Publication Date: 29 December 2004

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A discussion of what is known experimentally about the thermal contact problem at very low temperatures is given. Liquid 4He is a particularly promising contact agent. Methods of using liquid 4He, thermometry using cerium magnesium nitrate, and solutions to the filling and isolation problems using an open capillary are discussed. The techniques are applied to an apparatus suitable for heat capacity measurements to below 0.02°K and to an apparatus for measurement of superconductive properties at temperatures substantially below 0.01°K. The performance of the apparatus for heat capacity and superconductivity measurements is discussed.

Contour Plotting System with High Speed Symbol Head

D. R. Skuce

Rev. Sci. Instrum. 37, 832 (1966); http://dx.doi.org/10.1063/1.1720341 (4 pages)

Online Publication Date: 29 December 2004

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An instrument for producing contour diagrams using a conventional X‐Y plotter is described. It consists of a specially designed pulsed current plotting head controlled by gating circuits which use commercial analog and digital modules. The X‐Y plotter scans the head over electrosensitive paper and symbols consisting of dot patterns are plotted with no mechanical delay. The gating circuits may be adjusted to any desired set of contour intervals.

Use of Rotating Cryostat for Infrared Studies

G. Mamantov, W. H. Fletcher, S. S. Cristy, C. T. Edwards, and R. E. Morton

Rev. Sci. Instrum. 37, 836 (1966); http://dx.doi.org/10.1063/1.1720342 (3 pages)

Online Publication Date: 29 December 2004

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A modified rotating cryostat and its use for in situ infrared studies are described. An improvement in sensitivity over present low temperature infrared cells and much shorter deposition times have been obtained.

Linearizer for Constant Temperature Hot Wire Anemometer

Francis H. Champagne and John L. Lundberg

Rev. Sci. Instrum. 37, 838 (1966); http://dx.doi.org/10.1063/1.1720343 (6 pages) | Cited 8 times

Online Publication Date: 29 December 2004

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Experiments to determine the heat transfer from hot wires with length‐to‐diameter ratios on the order of 102, which are commonly used in hot wire anemometry, were performed. The Reynolds numbers used were less than 10, the overheat ratio was kept at 0.80, and the fluid was air. The results indicate that the exponent n in the relationship Eb2 = A+BUn, where Eb is the bridge voltage and U the fluid velocity, was equal to 0.45 for wires operated at constant temperature. A linearization circuit which provides an accurate means of recovering the velocity from the above relationship for values of n of 0.45 and 0.50 is described. The main component of the circuit is a temperature compensated, ten segment silicon diode function generator manufactured by Philbrick Researches, Inc. The frequency response of the linearizer is from dc to 36 kc or from dc to 180 kc depending on the operational amplifiers used in the circuit.

Low Shear, High Sensitivity Electromagnetic Viscometer

F. S. Gaeta

Rev. Sci. Instrum. 37, 844 (1966); http://dx.doi.org/10.1063/1.1720344 (6 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A new type of viscometer operated by electromagnetic force is described. Two versions of such an apparatus are presented, one involving the measurement of mechanical entities only, the other based upon the measurement of ionic current density and of a magnetic field. These viscometers are both closely related to ordinary flow viscometers since the force setting the liquid into motion acts directly on the liquid itself, with no mechanical moving part interposed. The force is much less intense than gravity and is easily adjusted at will down to very small values. For this reason and because of a better design of the channel in which the liquid flows, very low values of shear stress can be obtained; thus making the apparatus described ideal for use with non‐Newtonian liquids, like high polymeric solutions or suspensions of DNA. The fact that the liquid must be subjected to electrolysis is a serious drawback, which can be circumvented by resorting to relative measurements. Improvement of the apparatus is under study.

Measurement of Currents Flowing through Electrode in Contact with Plasma

M. Haegi

Rev. Sci. Instrum. 37, 850 (1966); http://dx.doi.org/10.1063/1.1720345 (2 pages)

Online Publication Date: 29 December 2004

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Currents flowing through an electrode, in contact with a plasma, can be measured by inserting Rogowsky coils in the electrode itself. In order to avoid uncontrollable shunting of the current and damage of the coil owing to the plasma, a thin metallic foil is inserted between the coil and the plasma. The effects of such a screen on the measurements are calculated and compared with experimental results.

Curie‐Chéneveau Magnetic Balance Employing Photocompensation

Riku Nakagome and D. H. Whitmore

Rev. Sci. Instrum. 37, 852 (1966); http://dx.doi.org/10.1063/1.1720346 (5 pages)

Online Publication Date: 29 December 2004

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The design of a balance for measurement over the range from 4.2 to 300°K of the static magnetic susceptibility of weakly magnetic substances is described. The balance is a Curie‐Chéneveau type torsion balance which incorporates photocompensation to achieve a null measuring instrument. The maximum sensitivity of the balance is approximately 10−3 dyne and performance with less than 1% error is possible for magnetic susceptibility values in the range from 10−5 to 10−8 emu∕g (cgs units). Some typical susceptibility data obtained with the aid of this balance are presented.

Electron Bombardment Molecular Beam Detector

Gilbert O. Brink

Rev. Sci. Instrum. 37, 857 (1966); http://dx.doi.org/10.1063/1.1720347 (4 pages) | Cited 76 times

Online Publication Date: 29 December 2004

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Show Abstract
A molecular beam electron bombardment detector is described and operational data are presented. The detector makes use of a Paul mass filter to increase its versatility. The detector is calibrated by the use of molecular beams of neon, argon, and krypton. Respective detection efficiencies are 1 atom in 2400, 320, and 80.

30 keV Ion Bombardment Apparatus for Study of Interaction of Light Ions with Surfaces

G. M. McCracken, J. H. C. Maple, and H. H. H. Watson

Rev. Sci. Instrum. 37, 860 (1966); http://dx.doi.org/10.1063/1.1720348 (7 pages) | Cited 14 times

Online Publication Date: 29 December 2004

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An ultrahigh vacuum system is described which was designed to study particles emitted from surfaces under bombardment by hydrogen ions. Stress has been laid on obtaining pressures ∼10−9 Torr in the presence of the ion beam. The beam is mass analyzed and its energy is variable from 5 to 30 keV. A maximum current of 300 μA over 0.1 cm2 is obtainable at the target, so that a beam∕neutral gas bombardment ratio of better than 1000∕1 can be achieved. A target mounting turntable is described which allows up to six targets to be bombarded in turn. A quadrupole mass filter is incorporated in the target chamber as a residual gas analyzer and as a means of identifying gas species resulting from the bombardment of surfaces.

Reliable Submicron Pressure Readings with Capacitance Manometer

Nyle G. Utterback and Thomas Griffith

Rev. Sci. Instrum. 37, 866 (1966); http://dx.doi.org/10.1063/1.1720349 (5 pages) | Cited 60 times

Online Publication Date: 29 December 2004

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A cold trapped McLeod gauge, a capacitance manometer, and an ion gauge have been used simultaneously to measure gas pressure in the range 10−4 to 3×10−3 Torr. Data were obtained for He, Ne, Ar, Kr, Xe, N2, O2, CH4, CO, H2, and CO2. The capacitance manometer and pressure chamber were maintained at a constant room temperature to avoid thermal transpiration corrections. Comparison of data among gases clearly showed the systematic McLeod gauge error attributed to mercury streaming to the cold trap. The capacitance manometer and McLeod gauge readings agreed within 2% at 10−3 Torr for He, while the McLeod reading was 15% low for Xe at the same pressure. The errors for the other gases were intermediate. Spurious mercury capillary wetting effects, leading to serious errors in the McLeod gauge reading, were also noted for some of the molecular gases. The capacitance manometer was clearly superior to the McLeod gauge as a universal pressure sensor, and appears capable of reliable readings accurate to a few per cent at 10−4 Torr.

Miniature Diamond Ultrahigh Pressure Cell Adapted for In‐reactor Irradiation Studies

Gerald L. Kulcinski, Charles W. Maynard, and Robert C. Walsh

Rev. Sci. Instrum. 37, 871 (1966); http://dx.doi.org/10.1063/1.1720350 (3 pages)

Online Publication Date: 29 December 2004

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A special Bridgman opposed diamond anvil apparatus was constructed to generate useful static pressure to 50 kbar at ambient temperatures. It was designed to function in the environment of a nuclear reactor and to occupy 65 cc. A method of bombarding materials under pressure with fission fragments is described.

Production of Fine Holes in Metals and Semiconductors

J. Longfellow

Rev. Sci. Instrum. 37, 874 (1966); http://dx.doi.org/10.1063/1.1720351 (2 pages)

Online Publication Date: 29 December 2004

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Whiskers of iron, copper, tin, and silicon were obtained and used as microelectrodes in a spark erosion process. Silicon slices, thin metal sheets, whiskers, and thin films were successfully machined. Holes with diameters as small as 1 μ were produced through thin films of tantalum.

Weak Magnetic Field Measurement Using Permalloy‐Film uhf Resonance

C. E. Frank

Rev. Sci. Instrum. 37, 875 (1966); http://dx.doi.org/10.1063/1.1720352 (6 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A system is described for using uhf dipole resonance in uniaxially anisotropic permalloy films to detect and measure weak magnetic fields. The dipoles are pulled to a position at right angles to the easy axis where they approach a condition of infinite permeability. Dispersion of the anisotropy over the film causes a severe degradation of the permeability but is largely overcome by low level modulation of the field with a low frequency signal. The net movement of the dipoles in response to the weak field being tested is measured both in magnitude and direction using simple uhf dipole resonance, the detected output being phase detected in turn with the low frequency source acting as the reference. Experimental results, which closely approach the theoretically predicted results, have been obtained down to 10−9 Wb∕m2 sensitivity in 1 cps bandwidth in ordinary laboratory environments and using a 35 dB noise figure receiver. Means for greatly improving both the sensitivity and bandwidth are discussed.

Growth of Cobalt Crystals

Hugh T. Hudson

Rev. Sci. Instrum. 37, 881 (1966); http://dx.doi.org/10.1063/1.1720353 (2 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A method of growing cobalt crystals by the Bridgeman technique is given. Crystals are grown in vacuum utilizing induction heating as the power source. Cobalt crystals in the hexagonal phase have been obtained 0.95 cm diameter by 6.26 cm long.

Megampere Pulse Transformer for Coaxial Load

William H. Clark and John E. Myrberg

Rev. Sci. Instrum. 37, 883 (1966); http://dx.doi.org/10.1063/1.1720354 (3 pages)

Online Publication Date: 29 December 2004

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A transformer is described which delivers 2 MA into a low impedance load through a coaxial output line of about 6.35 mm inner conductor diameter and 12.7 mm cavity diameter. The transformer primary is connected to a 20 μF, 50 kV capacitor bank by forty‐eight flexible coaxial cables. The ringing frequency of the system with the secondary shorted is 70 kc.

Four Point Sheet Resistivity Techniques

Donald R. Zrudsky, Harry D. Bush, and John R. Fassett

Rev. Sci. Instrum. 37, 885 (1966); http://dx.doi.org/10.1063/1.1720355 (6 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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A technique of averaging two resistivity measurements, each made using a different pair of current probes of a square array on an infinite sheet, has been developed. It is shown in theory and practice that when one probe is common to each of the two measurements, an average eliminates all first order errors due to misalignment of the array. An electronic averaging circuit which provides a continuous single meter measurement of sheet resistivity is presented. Data taken with 1.27 mm infinite sheet probe assembly are shown to have a repeatability of ±0.33% (3σ) on a 145 Ω per square sample. This particular system has a useful range of 0.1 to 10 000 Ω per square. The circuity developed for the infinite sheet method is also shown to be applicable to the bounded sheet method (Van der Pauw technique). A novel infinite sheet probe assembly design is illustrated.

Signal and Noise Characteristics of Robinson Nuclear Absorption Circuit

D. H. Howling

Rev. Sci. Instrum. 37, 891 (1966); http://dx.doi.org/10.1063/1.1720356 (2 pages) | Cited 5 times

Online Publication Date: 29 December 2004

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A previous study of the signal and noise characteristics of the Pound‐Knight‐Watkins (PKW) marginal oscillator circuit has been extended to the Robinson NMR circuit. It is shown that although the signal and noise characteristics of the Robinson circuit are markedly different from the PKW oscillator, the signal‐to‐noise ratios are similar.

Quenching Furnace for Elevated Temperature Tensile Test

William G. Holley and Thomas F. Talbot

Rev. Sci. Instrum. 37, 893 (1966); http://dx.doi.org/10.1063/1.1720357 (2 pages)

Online Publication Date: 29 December 2004

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A method of quenching a specimen subjected to a tensile stress at elevated temperatures has been developed. Tensile tests with stress, time, and temperature as variables are possible. The cooling rate of specimens in the 600°C range can be controlled from ¼ to 25°C∕sec.

Simple Procedure for Measurement of Hg Vapor Pressure of Amalgams

Joseph M. Margolis

Rev. Sci. Instrum. 37, 895 (1966); http://dx.doi.org/10.1063/1.1720358 (2 pages)

Online Publication Date: 29 December 2004

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A simple, relatively accurate method for determining the Hg vapor pressure of amalgams at elevated temperatures is described. The transmission of 2537 Å radiation through an evacuated quartz optical cell containing the amalgam is compared with that of a similar cell containing only Hg, using a spectroradiometer. After plotting log transmission vs 1∕T °K for each of the cells, the Hg vapor pressure of the amalgam is found by determining the temperature at which the Hg cell shows the same transmission as the amalgam, and reference to a table of Hg vapor pressure vs temperature.

Wide Band Electrostatic Probes for Use in Tenuous Plasmas

J. C. Sprott

Rev. Sci. Instrum. 37, 897 (1966); http://dx.doi.org/10.1063/1.1720359 (4 pages) | Cited 11 times

Online Publication Date: 29 December 2004

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A derivation is given for the resistance of the sheath surrounding a floating probe and the corresponding limitation to the frequency response. The bandwidth is increased by using probes with built‐in attenuators which measure fluctuations in floating potential, electric field, and ion saturation current at frequencies up to 40 MHz with plasma densities as low as 109 cm−3.

Dual Beam Stopped Flow Spectrophotometer Utilizing Modulated Xenon Arcs

R. J. DeSa and Q. H. Gibson

Rev. Sci. Instrum. 37, 900 (1966); http://dx.doi.org/10.1063/1.1720360 (7 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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This paper describes a dual beam stopped flow apparatus for quantitatively observing rapid (up to 250 sec−1) chemical reactions in turbid suspensions. The unit employs two commercial 150 W xenon arc light sources modulated to produce square light pulses at 5000 cps; two wavelengths of light are selected by monochromators, and the light is delivered to the reaction cuvette of a conventional stopped flow apparatus via a fiber optic light guide ``Y.'' Current and light intensity feedback are utilized to control lamp intensity; simple transistor choppers demodulate the measuring photomultiplier output, and a second photomultiplier is utilized in a differencing scheme to reduce effects of residual lamp instability. The instrument has a limit of detectability of 1×10−3 optical density units; crosstalk of signal from one channel into the other channel is 6% of the change being measured. An example of instrument performance is presented; as now constructed, the instrument provides time resolution at least 5 times higher and reagent economy more than 20 times higher than other available dual wavelength spectrophotometers.

Detonation Calorimeter and Results Obtained with Pentaerythritol Tetranitrate (PETN)

Donald L. Ornellas, John H. Carpenter, and Stuart R. Gunn

Rev. Sci. Instrum. 37, 907 (1966); http://dx.doi.org/10.1063/1.1720361 (6 pages) | Cited 10 times

Online Publication Date: 29 December 2004

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A bomb calorimeter for measuring the heat of detonation of 25 g charges of high explosive is described. A complete calorimetric measurement can be made in 1 h with a precision of 0.3%. Calorimetric measurements and analysis for PETN are described. The data are interpreted with the aid of thermodynamic and hydrodynamic computer calculations. For unconfined or lightly confined charges, the released energy is largely retained in the products which are shocked considerably off the Chapman‐Jouguet isentrope by reflections from the bomb wall. For heavily confined charges, the energy is largely converted to kinetic and internal energy of the confining case, and the essentially unshocked products expand along the Chapman‐Jouguet isentrope. The products of detonation are found to freeze out at 1500 to 1800°K. The heat of detonation of PETN at 298°K is 1490±6 cal∕g, H2O(l).

Factors Affecting Resolution of Lead Scintillator Sandwich Shower Counters

J. K. Walker and T. M. Knasel

Rev. Sci. Instrum. 37, 913 (1966); http://dx.doi.org/10.1063/1.1720362 (4 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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Recent results by Crawford and Messel on the development of showers in lead by the Monte Carlo method are used to estimate the energy resolution of total energy absorption scintillation shower counters. It is probable that slight improvements in energy resolution over existing counters can be obtained by using 15 radiation lengths in the direction of the incident particle and sampling the shower after every math radiation length.

Field Ionization Gauge for Molecular Beam Detection

R. O. Woods and J. B. Fenn

Rev. Sci. Instrum. 37, 917 (1966); http://dx.doi.org/10.1063/1.1720363 (2 pages) | Cited 8 times

Online Publication Date: 29 December 2004

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An ionization gauge for molecular beam work has been developed which uses a field ionization tip as an ion source. Data are given regarding signal‐to‐noise ratio and sensitivity. Means of reducing the rate of tip deterioration are discussed and data given showing moderate reduction in signal strength over a 1 h period. Curves are given showing that the sensitive area of the gauge is small when compared to a 0.25 mm wide molecular beam.

Constant Current Source for Instrument Calibration

R. T. Santoro, F. E. Gillespie, and P. M. Aebersold

Rev. Sci. Instrum. 37, 919 (1966); http://dx.doi.org/10.1063/1.1720364 (4 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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Two current sources which give a constant current over a wide range of applied voltage have been built for use in calibrating electrometers having input resistors in the 10+10 to 10+12 Ω range. The sources consist of sealed parallel plate ionization chambers having one electrode coated with 241Am. Calibrations using the rate of charge method spaced over a period of 1 year define the respective current output of the sources as (6.943±0.003)×10−11 and (4.263±0.004)×10−12 A.
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