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Dec 1963

Volume 34, Issue 12, pp. 1307-1456

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Combined Fluorometer and Double‐Beam Spectrophotometer for Reflectance Measurements

Britton Chance, Victor Legallais, and Brigitte Schoener

Rev. Sci. Instrum. 34, 1307 (1963); http://dx.doi.org/10.1063/1.1718224 (5 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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An apparatus suitable for recordings of extracellular oxygen tension in terms of the degree of hemoglobin dissociation and intracellular oxidation‐reduction state in terms of the fluorescence level of mitochondrial and cytoplasmic reduced pyridine nucleotide has been constructed. A time sharing sequence permitting light and dark intervals for reflectance fluorometry and two flashes of different wavelengths for reflectance spectrophotometry operates at a repetition frequency of 60 cps. Fixed filters are used in fluorometry for excitation and emission and continuously variable interference filters are used in spectrophotometry.

Multiplication and Logarithmic Conversion by Operational Amplifier‐Transistor Circuits

William L. Paterson

Rev. Sci. Instrum. 34, 1311 (1963); http://dx.doi.org/10.1063/1.1718225 (6 pages) | Cited 19 times

Online Publication Date: 29 December 2004

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Multiplier and log converter circuits in the literature which are based on junction diodes have in common the requirement that the junction employed have a constant slope of the log I vs V characteristic. When current components of the Cutler‐Bath and Sah‐Noyce‐Shockley types are considered, it is found that the range over which any one component becomes dominant, permitting application of the junction for logarithmic conversion, is narrow. The transfer conductance yFB of silicon diffused transistors is shown to exhibit the desired logarithmic characteristic over many decades. The use of an operational amplifier to impose the required bias conditions is discussed, together with performance limitations imposed by the amplifier. Circuits are given illustrating the application of the technique to vacuum gauges, transistor testing, and to an analog multiplier having a dynamic output range of five decades. A commercial electrometer is converted to logarithmic indication by the addition of only two components.

Automated Contact Resistance Probe

Morton Antler, L. V. Auletta, and J. Conley

Rev. Sci. Instrum. 34, 1317 (1963); http://dx.doi.org/10.1063/1.1718226 (6 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A probe is described that will determine (a) contact resistance with continuously increasing pressure from 0–1000 g, (b) contact resistance as a function of wipe distance at fixed normal load, and (c) the current‐voltage properties of films from 0–200 V. In pressure and voltage modes, specimen positioning is entirely automatic and programmable. The probe locates the test surface on an X‐Y plane, goes through the selected mode, and then automatically repositions and repeats the measurement according to test schedule. The wipe mode is performed manually. Resistance, current, voltage, load, wipe distance, and location of the specimen are read out on an oscillographic recorder. Contact resistance is measured by the four‐point technique from 10−4 to 103 Ω. The resistance span is divided into six ranges which change automatically, from high to low, when the resistance decreases to a preset percentage of the scale. The open circuit dc voltage of the resistance measuring circuit is 10−2 or 5×10−2 V, depending on resistance range.

Choice of Betatron Oscillation Frequencies in a Spiral Sector FFAG Accelerator

G. Parzen and P. Morton

Rev. Sci. Instrum. 34, 1323 (1963); http://dx.doi.org/10.1063/1.1718227 (5 pages)

Online Publication Date: 29 December 2004

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In a fixed‐field alternating gradient (FFAG) accelerator, the stability limits and the stability of the machine against field perturbations are very much affected by the choice of the betatron oscillation frequencies, νr and νz. A general criterion for the stability of the accelerator is proposed and, using this criterion, a computer study was carried out on the dependence of the stability on νr and νz. The results of this stability survey seem to indicate a a relatively unique choice of νr and νz to obtain the desired beam intensity.

Integrating Video Microdensitometer

G. Will, H. W. Nolden, and V. F. Dickey

Rev. Sci. Instrum. 34, 1328 (1963); http://dx.doi.org/10.1063/1.1718228 (5 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A sensitive integrating microdensitometer for evaluation of diffraction films is reported. The instrument is simple in construction and requires no critical alignment. Contrary to general designs the scanning is done with the receiver by a Vidicon television pickup tube serving both as light sensitive element and scanning device. Circuits for processing the video signal are described.

Determination of the Dynamic Shear Modulus of a Composite Solid Propellant

Lionel H. Layton, G. A. Sheppard, and S. John Bennett

Rev. Sci. Instrum. 34, 1333 (1963); http://dx.doi.org/10.1063/1.1718229 (8 pages)

Online Publication Date: 29 December 2004

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Structural analyses of large solid propellant motors subjected to an environment of transportation and handling must include the contribution of the solid propellant. More accurate propellant mechanical properties are needed for this purpose than are presently being obtained. The test method described is for determination of the dynamic shear modulus in the frequency range 0.10 to 1000 cps. The specimen consists of two concentric metal rings carried by a flat plate of propellant. The high frequency data (70–1000 cps) are obtained by applying a known sinusoidal motion to the outer ring and measuring the response at the center. The transducer and center mounting are used as an inertial mass and are included in the analysis of the viscoelastic plate. The low frequency data (0.10–45 cps) are obtained by applying a known sinusoidal motion to the center of the specimen with the outer edge in a clamped position. The applied force and displacement are both measured at the center of the specimen. The theoretical response of a plate with the dimensions of the specimen is determined by using plate theory [J. H. Baltrukonis, W. G. Gottenberg, and R. H. Schreiner, Space Technology Lab. Tech. Rept. STL∕TR‐60–0000–19331 (1960)] and assuming a complex Poisson's ratio of 0.5+i(o). An IBM computer is used to reduce the high frequency data; however, for the low frequency data an approximate solution [A. I. Soler and M. A. Brull, Repts. No. 61–012 and 61‐A‐014 under contract U‐60–11305, Dyna∕Structures, Inc., Springfield, Pennsylvania (1961)] makes possible the reduction of results by a simple hand computation. Typical results for the complex dynamic shear modulus with its real and imaginary parts as well as the loss tangent are given for a composite solid propellant. These data indicate a precision of approximately ±10%.

Zero‐Point Detector for the Dauphinee‐Mooser Circuit

H. H. Soonpaa, C. D. Motchenbacher, and H. Dahl

Rev. Sci. Instrum. 34, 1341 (1963); http://dx.doi.org/10.1063/1.1718230 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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The Dauphinee‐Mooser circuit has been improved by incorporating into it a transistorized null detector. The effective noise level has been cut down to, and possibly below, the chopper noise level by picking only the portion of signal that is observed while the contacts are closed. Pickup of external stray signals has been cut down to the level where they are virtually imperceptible. A complete description of the amplifier circuit is included.

Parafocusing Diffractometry

R. E. Ogilvie

Rev. Sci. Instrum. 34, 1344 (1963); http://dx.doi.org/10.1063/1.1718231 (4 pages)

Online Publication Date: 29 December 2004

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A variable bent diffracting device is described which will fit on the Norelco diffractometer. The object of this device is to provide a coupling to the rotation of the diffracting element about the goniometer axis and to bend the element automatically so that its radius of curvature has a constant value over its surface and in particular the correct value at each diffraction angle. With such a device it has been demonstrated that it is possible to eliminate the major source of error in peak displacement and, in particular, improve the resolution of low angle lines.

Equipment and Techniques for Low Temperature Electron Irradiations

L. F. Lowe, C. Jimenez, and E. A. Burke

Rev. Sci. Instrum. 34, 1348 (1963); http://dx.doi.org/10.1063/1.1718232 (3 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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A system is described for making low temperature electron bombardment studies. A liquid helium Dewar is used in conjunction with a 1.2‐MeV Dynamitron electron accelerator. Cooling is by conduction, and annealing is accomplished by balancing the helium flow rate through the cooling coils with a heater located within the cooling head. Details of the sample mount are given along with the beam positioning and monitoring devices.

Surface Balance for Production of Rapid Changes of Surface Area with Continuous Measurement of Surface Tension

R. M. Mendenhall and A. L. Mendenhall

Rev. Sci. Instrum. 34, 1350 (1963); http://dx.doi.org/10.1063/1.1718233 (3 pages) | Cited 14 times

Online Publication Date: 29 December 2004

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A surface balance is described for production of dynamic changes of area of films adsorbed at a gas‐liquid interface. It has been used to demonstrate reduction of surface tension to nearly zero by surface active agents derived from mammalian lungs.

Some Interactions between Vacuum Gauges

Francis T. Worrell

Rev. Sci. Instrum. 34, 1352 (1963); http://dx.doi.org/10.1063/1.1718234 (4 pages)

Online Publication Date: 29 December 2004

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Interactions have been found between a magnetron gauge and ionization gauges, and between two ionization gauges in close proximity. Evidence is presented to show that the first resulted from positive ions coming from the magnetron gauge. The second interaction was caused by some electrons emitted by one gauge migrating to the other.

Fast‐Neutron Detector with Discrimination against Background Radiation

R. B. Mendell and S. A. Korff

Rev. Sci. Instrum. 34, 1356 (1963); http://dx.doi.org/10.1063/1.1718235 (5 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A detector that measures neutrons between 1 and 10 MeV in a mixed background of charged and neutral radiation was developed for use in cosmic‐ray studies. The detector consists of liquid scintillator NE213 surrounded by a thin shield of plastic phosphor NE102 for charged particle rejection. Both scintillators are viewed by a single photomultiplier, in an adaptation of the pulse‐shape discrimination technique.

Automatic Area Compensator for Constant Stress Cycling

C. E. Feltner and J. Jackobs

Rev. Sci. Instrum. 34, 1360 (1963); http://dx.doi.org/10.1063/1.1718236 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A device is described which may be added to an Instron tensile testing machine that allows cycling between stress limits rather than load limits. Changes in specimen length are used as an index of area change. Specimen extension, converted to an electrical signal, is used as a feedback signal which continually adjusts the calibration of the load control chart so that the stress limits are maintained constant throughout a test.

Optically Pumped Nuclear Magnetometer

L. D. Schearer, F. D. Colegrove, and G. K. Walters

Rev. Sci. Instrum. 34, 1363 (1963); http://dx.doi.org/10.1063/1.1718237 (4 pages) | Cited 16 times

Online Publication Date: 29 December 2004

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See Also: Erratum

Show Abstract
A continuous recording total earth's field magnetometer has been demonstrated which utilizes optical pumping in He3 and the resultant polarization of the nuclear spins. The device operates as a ``self‐oscillator'' at the Larmor frequency of the ground state atoms. The oscillator has a ``Q'' of 104 in a 0.5‐G field. The sensitivity of the instrument to fluctuations in the magnetic field is presently several microgauss. The characteristics and operating principles of the instrument are described. The application of the device to the measurement of the absolute value of the total external magnetic field is discussed.

Continuous Ion Source for a Time‐of‐Flight Mass Spectrometer

Martin H. Studier

Rev. Sci. Instrum. 34, 1367 (1963); http://dx.doi.org/10.1063/1.1718238 (4 pages) | Cited 11 times

Online Publication Date: 29 December 2004

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With simple modifications improved performance of continuous ion sources in a time of flight mass spectrometer has been obtained. The system was developed for use with heated filament surface ionization sources; however, the advantages of its use with an electron bombardment source seem more significant. With an electron gun operating continuously, a factor of 300 increase in sensitivity over that of the pulsed mode of operation is attained with improved resolution and no increase in the ratio of noise to signal.

Miniature Cryostats: Design and Application to Matrix‐Isolation Studies

David White and D. E. Mann

Rev. Sci. Instrum. 34, 1370 (1963); http://dx.doi.org/10.1063/1.1718239 (5 pages) | Cited 14 times

Online Publication Date: 29 December 2004

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A cryostat of novel design has been constructed and tested for use in matrix‐isolation spectroscopy at low temperatures. The refrigeration is supplied by a built‐in miniature open‐cycle Joule‐Thomson liquefier which operates from tanks of high‐pressure nitrogen and hydrogen. At 15–16°K, the lowest temperature that can be achieved, the device supplies up to 2 W of refrigeration. The temperature of the cold window on which the matrix is deposited can be varied continuously in the range 15–200°K and readily controlled to ±0.3°K or better. The small, compact, and efficient cryostat design that has been achieved permits great flexibility of coupling to spectrometers and other instruments, and offers many interesting possibilities for a variety of other applications.

Low Frequency Ferromagnetic Resonance Spectrometer

P. V. Lenzo

Rev. Sci. Instrum. 34, 1374 (1963); http://dx.doi.org/10.1063/1.1718240 (3 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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During an investigation of the effects of anisotropy on the conditions for ferromagnetic resonance at low frequencies in gallium and aluminum substituted YIG, the need arose for a ferromagnetic resonance spectrometer which would operate from about 100 to 1000 Mc. This memorandum describes a marginal oscillator technique which has proved to be both rapid and accurate. The operation is analogous in many respects to the operation of marginal oscillators for nuclear magnetic resonance. The system is similarly characterized by simplicity of equipment, ease of linewidth calibration, and high sensitivity of detection. Linewidths measured from 250 to 1000 Mc on YIG‐Ga spheres and disks are given to illustrate the technique.

Probe System for Plasma Research

J. M. Chapuk, V. L. Corso, V. S. Foote, W. L. Harries, R. M. Sinclair, J. L. Upham, and S. Yoshikawa

Rev. Sci. Instrum. 34, 1377 (1963); http://dx.doi.org/10.1063/1.1718241 (7 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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A probe system for studying the plasma of a stellarator is described. Such a fully ionized plasma can have a density ∼1013 cm−3 and a temperature ∼50 eV. The probe translator can carry various probes (we take as an example a simple Langmuir electrostatic probe) and forms part of an ultrahigh vacuum system. The associated circuitry for probe biasing, control, position indicating, and data handling and display must meet various requirements of accuracy, bandwidth, and personnel safety. Some experimental results obtained with the system are discussed, and compared with those obtained by other methods.

Instability in the Magnetron Gauge

Francis T. Worrell

Rev. Sci. Instrum. 34, 1384 (1963); http://dx.doi.org/10.1063/1.1718242 (2 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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Chart records of the ion current in a magnetron gauge of the Redhead design show frequent small downward jumps, and occasional jumps into a different mode of operation. Unstable operation, resulting in a noisy trace, has also been seen during pressure surges in the system. Possible interpretations are mentioned.

Thermal Conductivity of Some Amorphous Dielectric Solids Below 1°K

A. C. Anderson, W. Reese, and J. C. Wheatley

Rev. Sci. Instrum. 34, 1386 (1963); http://dx.doi.org/10.1063/1.1718243 (5 pages) | Cited 44 times

Online Publication Date: 29 December 2004

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The thermal conductivities of nylon, Teflon, Kel‐F, hard rubber, Epibond 100A, Epibond 104, and Pyrex have been measured below 1°K, generally in the range 0.8 to 0.1°K. In all cases the thermal conductivity decreases more rapidly than linearly with decreasing temperature. If this temperature dependence is assumed to result from intrinsic structure scattering and a single temperature independent scattering length, the resulting scattering lengths fall in the range 10−3 to 10−4 cm. Several of the materials studied, particularly Teflon, Epibond 104, and nylon, have significantly lower thermal conductivities in the temperature range investigated than does Pyrex, the material most commonly used for thermal isolation in the design of demagnetization cryostats.

High Speed Shutter Mechanism

John O. Clayton

Rev. Sci. Instrum. 34, 1391 (1963); http://dx.doi.org/10.1063/1.1718245 (2 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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An electromechanical shutter for high speed spectroscopic studies is described. The device utilizes the energy of an electrically exploded metal foil to accelerate a movable slit, and propel it across a fixed slit. The minimum delay time is 19±2 μsec. A 20‐μ fixed slit may be opened and closed in 2 μsec by a 20‐μ moving slit. No medium is introduced into the optical path to alter spectral distribution.

Bright Field Photography in a Hydrogen Bubble Chamber

D. R. Firth

Rev. Sci. Instrum. 34, 1393 (1963); http://dx.doi.org/10.1063/1.1718246 (6 pages)

Online Publication Date: 29 December 2004

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The performance of bright and dark field optics in a bubble chamber is analyzed. A modification of the usual bright field scheme is proposed, so that very high contrasts may be achieved even in liquid hydrogen. The new scheme can also be used in a single‐window chamber. Results of tests of the scheme are presented to support this modification. Photography of bubbles smaller than the resolution limit is discussed; in this case a dark field scheme shows a clear advantage.

Nonsaturating Ionization Chamber for High Intensity External Proton Beam

C. E. Swartz, G. S. Levine, and R. L. Carmen

Rev. Sci. Instrum. 34, 1398 (1963); http://dx.doi.org/10.1063/1.1718247 (2 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A low density parallel plate ionization chamber which exhibits a linear response to high intensity pulses of 3‐GeV protons is described.

Instrument for Continuous High Resolution Measurement of Changes in the Velocity of Ultrasound

R. J. Blume

Rev. Sci. Instrum. 34, 1400 (1963); http://dx.doi.org/10.1063/1.1718248 (8 pages) | Cited 25 times

Online Publication Date: 29 December 2004

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The frequency of the ``reference'' oscillator in a coherent pulse echo apparatus is phase‐locked to the spacing in time of the acoustic echoes. A change in echo spacing is thereby converted to the same fractional change of oscillator frequency, which is measured continuously. Echo spacing changes of 2 to 3 parts in 108 have been resolved at 12 Mc. The gated AFC circuit which controls the reference oscillator derives its error voltage from a phase‐detected echo. The error voltage is zero when the echo is in quadrature with the reference. When the echo spacing changes, the AFC shifts the reference frequency to preserve the quadrature condition. The system is largely insensitive to changes of echo amplitude because such changes do not affect the quadrature condition. The attainable accuracy is set mainly by the temperature stability of the sample. There is a detailed discussion of circuitry, performance, and suggested refinements.

Nanosecond Pulse Technique for Multiple Front Studies in Shock Tubes

M. J. Lubin

Rev. Sci. Instrum. 34, 1408 (1963); http://dx.doi.org/10.1063/1.1718249 (2 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A technique for the production of well‐defined, precisely timed nanosecond pulses of X‐band microwave power is described. A system for the investigation of extremely fast electron density fronts in shock tubes is outlined utilizing the transmitted and reflected pulses generated by this technique. The transmitted and reflected pulses are displayed on a 2000‐Mc, rastered oscilloscope.
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