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Oct 1966

Volume 37, Issue 10, pp. 1291-1426

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Low Temperature System for Thermal Conductivity Measurements

Miles V. Klein and R. F. Caldwell

Rev. Sci. Instrum. 37, 1291 (1966); http://dx.doi.org/10.1063/1.1719962 (7 pages) | Cited 15 times

Online Publication Date: 29 December 2004

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Germanium and platinum resistance thermometers are used with two metal Dewars over the temperature range from 1.2 to 300°K. A variable conductance helium exchange gas switch is employed together with automatic heating to maintain any desired temperature within this range. Two coupled potentiometric dc measuring circuits are used—one to measure and control the sample temperature, and the other to measure the temperature gradient. The performance of the system is discussed.

Accurate Resistance Measurement with Smith Bridge

H. Dekker and C. Mosselman

Rev. Sci. Instrum. 37, 1297 (1966); http://dx.doi.org/10.1063/1.1719963 (4 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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A commercial 6 decade Smith bridge has been improved by elimination of several types of disturbances. It is now possible to differentiate between temperatures which are less than 1.5×10−5°C apart.

Diffused Semiconductor Low Temperature Thermometers

T. H. Herder, R. O. Olson, and J. S. Blakemore

Rev. Sci. Instrum. 37, 1301 (1966); http://dx.doi.org/10.1063/1.1719964 (5 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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It is known that thermometers of good sensitivity and excellent reproducibility for low temperatures can be based on the temperature dependence of extrinsic electrical conductivity in a semiconductor. Uniformly doped germanium single crystals are customarily used for this purpose; however, the present paper reports on the performance of experimental semiconductor thermometers made by diffusion techniques. Thermometer elements were made both by diffusion of arsenic into germanium, and by diffusion of boron into silicon. For both of these systems, the conductance‐temperature characteristic of a diffused layer was qualitatively similar to the conductivity‐temperature characteristic of a uniformly doped thermometer bar. However, diffused thermometers suffered appreciable changes of resistance on thermal cycling, to an extent corresponding with temperature errors as large as 0.1° at 4.2°K. This compares unfavorably with the submillidegree reproducibility attainable with uniformly doped bridge shaped bars. Attempts to improve the stability of diffused layers are discussed.

Automatic Double Probe Method of Obtaining Electron Temperatures

R. H. Hines

Rev. Sci. Instrum. 37, 1305 (1966); http://dx.doi.org/10.1063/1.1719965 (3 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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An instrument used for continuously determining electron temperature in an ion engine exhaust is described. The ratio of measured currents at specified regions of the double probe characteristic is computed to yield a good approximation of electron temperature for conditions in which the ion sheath buildup is small.

Determination of Plasma Potentials and Ion Energies by Ion Extraction and Energy Analysis

C. W. Erickson

Rev. Sci. Instrum. 37, 1308 (1966); http://dx.doi.org/10.1063/1.1719966 (3 pages) | Cited 10 times

Online Publication Date: 29 December 2004

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This paper describes the theory and operation of a new diagnostic tool for the extraction of ions from the main body of a confined plasma. The device, a magnetically shielding tube used in conjunction with an electrostatic energy analyzer and secondary electron detector, can be used for measuring ion energy distributions, plasma potential, and energy dependence of plasma ion lifetimes. Shielding properties and limitations of the device are also discussed.

Versatile High Pressure Mössbauer Apparatus

P. Debrunner, R. W. Vaughan, A. R. Champion, J. Cohen, J. Moyzis, and H. G. Drickamer

Rev. Sci. Instrum. 37, 1310 (1966); http://dx.doi.org/10.1063/1.1719967 (6 pages) | Cited 35 times

Online Publication Date: 29 December 2004

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An apparatus has been developed which permits high pressure Mössbauer resonance studies to 300 kbar. It can be operated with either the source or the absorber under pressure. The pressures are established by x‐ray diffraction measurements, and calibration curves are presented for both the supported taper and Bridgman anvils cells. A motion device involving magnets and phosphor bronze springs, with an adjustable mount, is described. Circuits necessary to control the motion, and to distribute the signals from two devices operating in parallel, are outlined.

Digital Recording of Spectra. Conversion of Perkin‐Elmer Model 521 Infrared Spectrometer

Norman C. Peterson, Robert P. Bauman, and Irving W. Price

Rev. Sci. Instrum. 37, 1316 (1966); http://dx.doi.org/10.1063/1.1719968 (2 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A double beam, optical null infrared spectrometer has been adapted for digital recording without interfering with the normal operating modes of the instrument. A photoelectric dial reader operates a solid state switching circuit at each calibration mark of the wave number dial to cause a digital voltmeter to read the voltage across the linear transmittance slidewire of the spectrometer, while the spectrometer operates in the absorbance recording mode. The digital voltmeter operates a paper tape punch, permitting computer processing of the spectra.

Ionization Gauge for Transient Gas Pressure Measurements

E. A. Valsamakis

Rev. Sci. Instrum. 37, 1318 (1966); http://dx.doi.org/10.1063/1.1719969 (3 pages) | Cited 14 times

Online Publication Date: 29 December 2004

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A gauge has been developed that is particularly suited for measuring transient gas pressures (e.g., gas bursts expanding in vacuum). A commercial subminiature pentode has been used in a suitable circuit for this purpose. Calibration curves for helium, nitrogen, neon, argon, krypton, and xenon at room temperature are given in the 1 to 400 μ Hg range. The features of this gauge are its small size, short risetime, and simple construction and installation. The serious disadvantage is its short lifetime, about 3 weeks of continuous use, mainly due to filament failure.

Thin Film Magnetoresistance Magnetometer

R. S. Hebbert and L. J. Schwee

Rev. Sci. Instrum. 37, 1321 (1966); http://dx.doi.org/10.1063/1.1719970 (3 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A thin film alloy of Ni‐Fe‐Co is etched such that it resembles electrically a Wheatstone bridge except that the arms of the bridge are magnetoresistive. The resistance of one arm increases and the other decreases when in the presence of a magnetic field. The primary feature of this magnetometer is its fast response time. Tests have shown that it has a flat response to alternating magnetic fields with frequencies as high as 65 MHz which was the limit of our test equipment. We have reason to believe that our present system will measure pulses with risetimes as fast as 4 nsec with less than 5% error.

Method for Studying Sputtered Particles by Emission Spectroscopy

Erich Sawatzky and Eric Kay

Rev. Sci. Instrum. 37, 1324 (1966); http://dx.doi.org/10.1063/1.1719971 (6 pages) | Cited 8 times

Online Publication Date: 29 December 2004

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An f∕6.8 scanning spectrometer with a photomultiplier output was used to monitor the presence of particles sputtered from a target surface by ion bombardment. The ion source was a conventional duoplasmatron providing a high density, high energy ion beam. The density of sputtered particles available for analysis was of the order of 108 cm−3. A fraction of these particles was electronically excited by a high density, low energy electron beam, and the emission spectra characteristic of the target material were recorded with either an electrometer or a phase sensitive detector. Some intense atomic copper lines were easily observed when a Cu target was bombarded with 5000 eV Ar+ ions. The intensities of these lines have been analyzed to obtain the sputtering yield and some relative excitation functions for copper. A comparison between the conventional mass spectrometric technique and the present scheme is presented.

Use of Conformal Mapping to Improve Field Uniformity of Electromagnet

F. L. Fuller

Rev. Sci. Instrum. 37, 1330 (1966); http://dx.doi.org/10.1063/1.1719972 (3 pages)

Online Publication Date: 29 December 2004

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Conformal mapping is used to determine the cross section of a shim in order to improve the uniformity of the field in the air gap of a magnet. Experimental measurements on a laboratory electromagnet demonstrate the improvement in field uniformity.

Use of Probes to Measure Static Potential in High Vacuum Electron Devices

W. Edward Lear and Richard S. Simpson

Rev. Sci. Instrum. 37, 1332 (1966); http://dx.doi.org/10.1063/1.1719973 (6 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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Design factors are considered for the use of emitting and nonemitting metallic probes for measuring static potential in electron streams. Both unneutralized streams and those neutralized by positive ions in a field free drift space are considered. Experimental results are given for potential measurements in a cylindrical diode and in a beam type tube. Good agreement with theory is found for the radial potential distribution in the diode using either probe. The emitting probe gives best results but is more complex in construction and circuitry. Qualitative agreement with theory is found for axial and radial potential distribution in a neutralized cylindrical electron beam.

High Pressure 3He Gas Scintillation Neutron Detector

R. Lee Aamodt, Leon J. Brown, and Gordon M. Smith

Rev. Sci. Instrum. 37, 1338 (1966); http://dx.doi.org/10.1063/1.1719974 (3 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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Construction details are given for a He gas scintillation neutron detector which operates to 238 atm at room temperature. A bakeable pressure‐vacuum manifold, on which the detector is evacuated and filled, also serves to remove contaminants from the DPS waveshifter. The detector appears stable when permanently sealed off. Curves are given for light output vs pressure, and some effects of impurities on such curves are noted. Measurements were made of relative sensitivity to 60Co gammas and Pu‐Be neutrons. The gamma flux required to induce a current equal to that from 1 neutron∕cm2 sec is 15 MeV∕cm2 sec when the scintillating gas is 4He, and 23 MeV∕cm2 sec when it is 3He.

Spark Chamber for Gamma‐Ray Astronomy

G. M. Frye, L. H. Smith, A. A. Hruschka, J. R. Goff, and A. D. Zych

Rev. Sci. Instrum. 37, 1340 (1966); http://dx.doi.org/10.1063/1.1719975 (5 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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A spark chamber system is described which is designed to detect γ rays in the cosmic radiation on high altitude balloon flights. It has (1) an acceptance cone of 30° half angle; (2) time resolution of 150 msec; (3) energy resolution from 30 to 500 MeV; and for a 100 MeV γ ray, (4) a conversion efficiency of 12.4%, and (5) angular resolution of 3°. Events are recorded photographically. The system is triggered by a large scintillator above the chamber in anticoincidence with a scintillator‐Čerenkov telescope beneath. Only the chamber and high voltage components are pressurized. A magnetometer direction monitor locates the γ ray direction to ±3° in right ascension and declination. The system has operated successfully on day and night flights and has a total weight of 80 kg.

Apparatus for Thin Sample Ultrasonic Measurements

I. L. Gelles and C. H. Bomhard

Rev. Sci. Instrum. 37, 1345 (1966); http://dx.doi.org/10.1063/1.1719976 (5 pages)

Online Publication Date: 29 December 2004

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A detailed description is given of an apparatus which makes possible the propagation of ultrasonic pulses through very thin solid samples (foils, films, fine wires, whiskers, etc.). The apparatus includes means for mounting the sample, independent transducer supports, and means for bringing sample and transducer into nondestructive contact. Several sample holding devices and micromanipulator adaptations are described. The over‐all measurement system is briefly described together with a few typical results for metal foil and fine wire specimens. Some applications of the apparatus are listed.

Method for Rapidly Reversing Magnetic Field in Shorted Superconducting Coil

John T. Harding

Rev. Sci. Instrum. 37, 1350 (1966); http://dx.doi.org/10.1063/1.1719977 (2 pages)

Online Publication Date: 29 December 2004

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A shorted superconducting coil carrying a persistent current can be made to reverse its field in less than 5 msec by subjecting the coil to an increasing external reverse field. The superconducting coil opposes a change in its interior field until its critical current is exceeded, whereupon rapid extinction of the persistent current occurs thus admitting the external field.

Automatic Unit for Thinning Transmission Electron Microscopy Specimens of Metals

R. D. Schoone and E. A. Fischione

Rev. Sci. Instrum. 37, 1351 (1966); http://dx.doi.org/10.1063/1.1719978 (3 pages) | Cited 24 times

Online Publication Date: 29 December 2004

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A specimen holder and a polishing unit with an automatic shutoff were designed for thinning disks taken from preselected areas of large metallic specimens or from specimens with small cross sectional areas. Since the disk precisely fits the specimen holder of the microscope, a supporting grid is unnecessary and deformation from cutting and handling after thinning is eliminated. The automatic shutoff device greatly improves conditions for transmission by stopping the polishing current at the optimum time.

E×B Energy Analyzer for Electrons

W. L. Barr and W. A. Perkins

Rev. Sci. Instrum. 37, 1354 (1966); http://dx.doi.org/10.1063/1.1719979 (6 pages) | Cited 17 times

Online Publication Date: 29 December 2004

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A simple electron energy analyzer has been used to measure energy distribution functions of the ``hot electron plasma'' produced in a compression mirror machine. The analyzer is located in a region of a steady 1.2 kG field so that electrons which escape from the 23 kG mirror field have most of their transverse energy transformed into the parallel component. This parallel component of energy is determined by the transverse drift in a region of mutually perpendicular electric and magnetic fields; low velocity electrons drift farther as they spend more time in the E×B field region, and vice versa. Electrons are detected by being accelerated onto a plastic scintillator which is viewed through a light pipe by a photomultiplier. Good time resolution is obtained, but since only one narrow energy band can be observed on each shot, the electric field is varied between shots to measure the complete energy spectrum. The magnetic field of the analyzer joins smoothly with the plasma containment magnetic field so that the electrons do not pass through a zero field region. With the 1.2 kG field, the analyzer works well for electron energies up to 20 keV; at higher energies the energy resolution decreases, and at very low energies (<100 eV) secondary electrons cause difficulties.

Arc‐Image Stagnation‐Flow Reactor for Measuring Kinetics of Gas‐Solid Reactions from 2000 to 3000°K

Irwin R. Ladd and Harold W. Wilson

Rev. Sci. Instrum. 37, 1359 (1966); http://dx.doi.org/10.1063/1.1719980 (5 pages)

Online Publication Date: 29 December 2004

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An arc‐image stagnation‐flow reactor has been developed to study the rates of gas‐solid reactions between 2000 and 3000°K. Most refractory solids can be heated in this reactor to their melting points in a partial atmosphere of almost any gas except strong oxidizers such as fluorine. The standard deviation of a datum point, in the case of oxidation of tungsten by CO2 at 100 Torr, is 6% at 2500°K, corresponding to a temperature uncertainty of ±9°K.

Simple High Speed Framing Cameras

J. S. Courtney‐Pratt

Rev. Sci. Instrum. 37, 1364 (1966); http://dx.doi.org/10.1063/1.1719981 (3 pages)

Online Publication Date: 29 December 2004

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J. Wadsworth and F. E. Stokes recently described a simple high speed camera. They formed an array of images using crossed rods of glass to form an array of small camera lenses, and each lens of this array formed a separate frame. They exposed successive frames by rotating a Nipkow disk in front of the crossed glass rods. Some years ago, I made some high speed cameras working on similar principles, but using lenticular plates as the array of camera lenses. Sequential operation could be by Nipkow disk or by control of the light sources, which could be an array of sparks, or more simply, the moving spot of a cathode ray tube. Rates of recording were in the range 105 to 106 pictures per second. The cameras are very simple and of low cost. They allow one to record long sequences of pictures. Picture quality was low but there is a reasonable prospect of improvement.

Computer Program to Facilitate Design of Wire Wound, Pulsed Field Coils

Gail P. Segal

Rev. Sci. Instrum. 37, 1367 (1966); http://dx.doi.org/10.1063/1.1719982 (3 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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This paper presents the formulas necessary to design wire wound, pulsed field coils to produce an initial time rate of change of magnetic field, math0 ≡ math (t = 0), the formulas being written in terms of the coil geometry, its wire size, and the applied voltage V. Since so many combinations of these parameters can result in the desired value of H0, the formulas for H and H0 were incorporated into a computer program to facilitate selection of the ``best combination'' of parameters. Economic or experimental constraints are easily handled by the program. The program is able to predict the performance of a pulsed field coil to an accuracy of better than 1%.

Extension of Scherzer's Theorem

Ronald W. Moses

Rev. Sci. Instrum. 37, 1370 (1966); http://dx.doi.org/10.1063/1.1719983 (3 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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A monochromatic, nonrelativistic system with electrostatic and∕or magnetic quadrupole fields having common planes of optical symmetry is treated theoretically. It is proven that certain aperture aberration coefficients are positive definite when there is a real object and image in one or both of the optical symmetry planes. In a purely magnetic system which is doubly focusing and has a real object and image, all aperture aberration coefficients are positive definite. Conditions that imply nonzero aperture aberrations for systems with virtual objects and∕or images are also given.

Generation of Cylindrically Symmetric Implosions

David Bernstein and R. C. Goettelman

Rev. Sci. Instrum. 37, 1373 (1966); http://dx.doi.org/10.1063/1.1719984 (3 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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An explosive configuration has been developed for going from a single initiation point to a cylindrically symmetric, converging detonation front. This technique utilizes the ``mousetrap'' concept but in a cylindrical geometry rather than the usual plane geometry. The mousetrap action results in the simultaneous initiation of the outer surface of an explosive cylinder 15.9 cm in diameter and 5 cm long. The breakout of the detonation front has been monitored as a function of axial position in a cylindrical hole 5 cm in diameter. The azimuthal simultaneity has been studied by monitoring the resultant collapse of a thin walled aluminum tube inside the explosive cylinder. Submicrosecond simultaneity was attained.

Sinusoidal Temperature Wave Generating System

D. A. Rigney

Rev. Sci. Instrum. 37, 1376 (1966); http://dx.doi.org/10.1063/1.1719985 (2 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A method of generating and measuring sinusoidal temperature oscillations of variable amplitude is described, and typical applications are presented.

Mechanical System for Multiple Thin Film Deposition

M. R. Randlett, E. H. Stroberg, and K. L. Chopra

Rev. Sci. Instrum. 37, 1378 (1966); http://dx.doi.org/10.1063/1.1719986 (3 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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A simple and versatile mechanical system, capable of allowing monitored deposition of sequential thin films on any one of the five substrates from any one of the five independent sources, and through any one of the five masks, is described. The vapor sources are moved by rotation. The substrates, masks, and the shutter are moved by sliding racks. All these movements are affected by one push‐pull, rotary, and 60° cone feedthrough. Every component is easily removable for cleaning. The evaporation sources are shielded by removable chimneys. The electrical connection for resistive heating of the source is made by a uniquely designed roller bearing contact.
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