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Apr 1971

Volume 42, Issue 4, pp. 411-548

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A High Resolution Electron Spectrometer for Use in Transmission Scanning Electron Microscopy

A. V. Crewe, M. Isaacson, and D. Johnson

Rev. Sci. Instrum. 42, 411 (1971); http://dx.doi.org/10.1063/1.1685116 (10 pages) | Cited 56 times

Online Publication Date: 4 November 2003

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The design and construction of a double focusing uniform field magnetic electron spectrometer are described. The pole pieces of the magnet are curved in an effort to correct all median plane aberrations and thereby increase the collecting power. The spectrometer has been installed on a scanning microscope which uses a field emission gun to produce a 100 Å probe. Energy analysis of the transmitted electrons as well as filtered diffraction patterns can be obtained from areas as small as 100 Å in diameter. In addition, the area under study can be observed directly in the scanning transmission mode, using electrons of any selected energy loss. A resolution of the spectrometer of 2 ppm at an electron energy of 20 keV is shown and the measured second order aberration coefficient is <5% of that of an equivalent straight edge sector magnet. Also, the solid angle for collection of electrons is about an order of magnitude greater than that of the equivalent straight edge magnet at any given resolution. Experimental results in all modes of operation are presented.

A Discussion of the Region of Linear Operation of Photomultipliers

Peter L. Land

Rev. Sci. Instrum. 42, 420 (1971); http://dx.doi.org/10.1063/1.1685117 (6 pages) | Cited 10 times

Online Publication Date: 4 November 2003

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A theoretical analysis shows factors which affect the onset of nonlinear response of the anode current of a photomultiplier to the light intensity incident on the photocathode, when the dynode voltages are provided by a linear resistor chain. The percent deviation from linearity of the anode current is shown to be independent of the number of dynodes and the gain per stage. The conditions do depend on the form of the gain per stage which is assumed to depend on parameters g=p+q. The parameter g is shown to have approximately the same value for a number of photomultipliers, so that any significant differences in the initial deviation from linearity would be attributed to the ratio p∕q. This ratio has not been measured, but a method of doing so is described. Some measurements of the deviation from linearity are discussed in terms of the analysis, and the indications from that limited sampling are that one can expect deviations to be less than 3% for all photomultipliers when the anode current is less than 0.1 the current in the final resistor of a linear bleeder chain.

Piezoelectric Determination of Crystal Axes

H. Engan

Rev. Sci. Instrum. 42, 426 (1971); http://dx.doi.org/10.1063/1.1685118 (3 pages)

Online Publication Date: 4 November 2003

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Two different methods of orienting piezoelectric crystals are described. One method depends upon the symmetry of the phase velocity of elastic surface waves as a function of propagation direction in a crystal face. The other method utilizes the symmetry of the piezoelectric coupling strength. Measurements in the Z planes of α‐quartz and LiNbO3 reveal accuracies better than 10′ for the determination of the nonoptic axes.

An Apparatus for Shearing Bulk Materials at High Temperature, High Pressure, and Various Strain Rates

A. E. Abey, L. L. Dibley, E. D. Joslyn, and H. D. Stromberg

Rev. Sci. Instrum. 42, 429 (1971); http://dx.doi.org/10.1063/1.1685119 (3 pages) | Cited 1 time

Online Publication Date: 4 November 2003

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An apparatus is described which measures the shear strength of bulk materials in the temperature range from 25 to 350°C, in the pressure range from 20–80 kilobars. The strain rate in this pressure and temperature range can be varied between 3.5×10−7 and 3.7×10−1 sec−1. Some data on OFHC copper are given to indicate the type of results obtained from this apparatus.

Capacitively and Inductively Foreshortened Cavities for Magnetic Resonance Spectroscopy

B. D. Guenther, C. R. Christensen, R. A. Jensen, and A. C. Daniel

Rev. Sci. Instrum. 42, 431 (1971); http://dx.doi.org/10.1063/1.1685120 (4 pages) | Cited 5 times

Online Publication Date: 4 November 2003

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Two types of cylindrical reentrant cavities are described for magnetic resonance and ultrasonic applications in the 0.1–‐1.0 GHz frequency region. The physical size of these cavities is reduced by introducing large capacitive and inductive elements into the cavity. Tuning, rf coupling, and temperature control techniques are described for operation at low temperatures.

Time Resolution of Plasma Potential Using Gridded Electrostatic Analyzers

J. E. Robinson and J. F. Clarke

Rev. Sci. Instrum. 42, 434 (1971); http://dx.doi.org/10.1063/1.1685121 (4 pages) | Cited 2 times

Online Publication Date: 4 November 2003

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A system is presented for the time resolution of plasma potential using gridded electrostatic analyzers. The novelty of this method is the separation of consecutive current‐energy characteristic curves and their display on a CRT. Using a 20 kHz bias signal, 30–50 consecutive 25 μsec sweeps are displayed on a CRT in a 1 msec time interval. This is sufficient for the study of low frequency plasma fluctuations in transient confinement experiments. Application to the DCX‐2 mirror machine is discussed.

Driven Equilibrium Methods for Enhancement of Nuclear Transients

Peter Waldstein and William E. Wallace

Rev. Sci. Instrum. 42, 437 (1971); http://dx.doi.org/10.1063/1.1685122 (4 pages) | Cited 15 times

Online Publication Date: 4 November 2003

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Several pulsed NMR experiments using rapidly repeating pulse sequences are described. Theoretical results for magnetization as a function of pulse spacing τ are given for cases where the Bloch equations apply, and compared with experiments. These results suggest a simple method of rapid signal accumulation when T2*<T2,T1, that is, when resolution is limited by magnet inhomogeneity.

A Secondary Reference Voltage Source Stable to 1 ppm

J. Raamot

Rev. Sci. Instrum. 42, 440 (1971); http://dx.doi.org/10.1063/1.1685123 (2 pages)

Online Publication Date: 4 November 2003

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The design of a simple parallel current regulation circuit has the following bandwidths: 10 MHz for voltage regulation, 0.2 Hz for the primary reference voltage circuit, and 20 Hz for amplifier noise. These characteristics compare very favorably to other voltage regulation circuits which are used in design of secondary reference voltage sources.

Accommodation Coefficient Measurements with a Sensitive Torsion Balance

C. Schmidt and H. I. Schiff

Rev. Sci. Instrum. 42, 442 (1971); http://dx.doi.org/10.1063/1.1685124 (2 pages) | Cited 2 times

Online Publication Date: 4 November 2003

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The normal impulse accommodation coefficient is measured with a torsion balance. Data for Ar, N2, O2, H2, N2O, CO2, stainless steel, and glass are given. The absolute error of the relative method used is Δσ′=0.05. The measurements occur at room temperature.

An Optical Magnetometer for Superconductivity Measurements

David J. Griffiths

Rev. Sci. Instrum. 42, 444 (1971); http://dx.doi.org/10.1063/1.1685125 (4 pages) | Cited 1 time

Online Publication Date: 4 November 2003

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The magneto‐optical Faraday effect associated with certain paramagnetic ions has been utilized to construct an optical magnetometer suitable for studying the magnetic properties of hollow cylinder superconductors. As an instantaneous field detector, the response of the system in general is limited only by the spin‐bath relaxation time of the paramagnetic ion‐host crystal system being used. The magnetometer has the advantage of requiring no moving parts and also avoids the necessity of having to extract a low level voltage signal from the low temperature environment. Also, since the detector is an insulator, there are no undesirable time derivative of field signals generated in its use. The operating field range is limited by the sensitivity desired in a given experiment. For fields up to 13.5 kOe at a temperature of 2.15 K, the sensitivity for the analyzer oriented at 45° with respect to the plane of polarization of the emergent light is at worst ±9.3 Oe. The text lists the sensitivity at various other fields and temperatures in tabular form. Initial results on superconducting hollow cylinder niobium are also presented.

An Amplifier Controlled Adiabatic Calorimeter

George J. Filatovs and Alfred E. Schwaneke

Rev. Sci. Instrum. 42, 447 (1971); http://dx.doi.org/10.1063/1.1685126 (4 pages) | Cited 2 times

Online Publication Date: 4 November 2003

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An automatic adiabatic differential calorimeter has been constructed to record the release spectrum of stored energy of deformation of metals from −196 to 500°C. A cold worked and an annealed specimen contain internal heaters which are powered by amplifiers, the signal inputs to which are specimen‐to‐calorimeter wall differential thermocouples. Control circuits attempt to maintain conditions as adiabatic as possible, and the power difference to the specimen heaters necessary to do this is taken as the stored energy of deformation.

A Bleed‐Type Pressure Transducer for In‐Stream Measurement of Static Pressure Fluctuations

B. W. Spencer and B. G. Jones

Rev. Sci. Instrum. 42, 450 (1971); http://dx.doi.org/10.1063/1.1685127 (5 pages) | Cited 4 times

Online Publication Date: 4 November 2003

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The theory, design, and operation of a bleed‐type pressure transducer for measurement of static pressure fluctuations in turbulent incompressible air flow are described. The transducer features miniature size (0.89 mm diam orifice), good sensitivity (3.0 mV∕cm of water), minimal yaw sensitivity, and approximately uniform amplitude response from dc to 8 kHz using helium as the bleed fluid. Static and dynamic methods of calibration are described as well as an experimental arrangement for wind tunnel measurements.

A Rotary Molecular Effusion Source for High Temperature Vaporization Studies

D. W. Muenow and R. T. Grimley

Rev. Sci. Instrum. 42, 455 (1971); http://dx.doi.org/10.1063/1.1685128 (4 pages) | Cited 4 times

Online Publication Date: 4 November 2003

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A high temperature rotary Knudsen cell assembly is described which, operating in conjunction with a mass spectrometer, may be used to determine the spatial distributions of individual species effusing from ideal and nonideal orifices and of species vaporizing from surfaces. This unit rotates about an axis contained within the plane of the face of the orifice or surface and is capable of reproducible angular settings of 0.2° under high temperature, high vacuum conditions. The apparatus is particularly suited to those types of mass spectrometers which are too cumbersome to be used as movable detectors. The angular distribution curves which result from these measurements may be used to determine orifice transmission probabilities and, in certain cases, to determine mass spectrometric parent‐fragment relationships which other techniques have failed to resolve.

Two Theoretical Analyses of the Output Signal from an Eddy Current Sensor

C. Baudelet

Rev. Sci. Instrum. 42, 458 (1971); http://dx.doi.org/10.1063/1.1685129 (4 pages)

Online Publication Date: 4 November 2003

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The theorical output signal of an eddy current sensor has been derived by two techniques. The physical analysis, which requires simplifying assumptions, leads to an expression suitable for numerical evaluation, while the dimensional analysis approach results in a similar formula that can serve as a guide to experiments.

Nuclear Resonance Spectrometers Using Field Effect Transistors

Neil Sullivan

Rev. Sci. Instrum. 42, 462 (1971); http://dx.doi.org/10.1063/1.1685130 (4 pages) | Cited 16 times

Online Publication Date: 4 November 2003

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We describe the use of field effect transistors of both the metal‐oxide‐semiconductor and the n‐channel junction type in marginal oscillator circuits designed respectively for the observation of NMR in the range 2–60 MHz and NQR in the range 3–40 MHz.

The Preparation of Large Plastic Films for Proportional Counter Windows

R. J. Grader, R. W. Hill, C. W. McGoff, D. S. Salmi, and J. P. Stoering

Rev. Sci. Instrum. 42, 465 (1971); http://dx.doi.org/10.1063/1.1685131 (3 pages) | Cited 3 times

Online Publication Date: 4 November 2003

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The preparation of thin and uniform plastic films for rocket‐borne x‐ray proportional counters is described. The technique has produced entrance windows of 60 μg∕cm2 thickness and 700 cm2 in area.

A Self‐Detecting Microwave Marginal Oscillator

W. M. Walsh and L. W. Rupp

Rev. Sci. Instrum. 42, 468 (1971); http://dx.doi.org/10.1063/1.1685132 (3 pages) | Cited 9 times

Online Publication Date: 4 November 2003

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A very simple and compact 12 GHz marginal oscillator employs a commercial Gunn device as both microwave source and detector. The sensitivity to electron spin resonance absorption (3×1012 standard spins) is comparable to that of a conventional homodyne bridge spectrometer. As a heterodyne detector of externally generated microwaves the sensitivity is ∼10−12 W.

Oxidation Apparatus for Determining Rates of Oxygen Absorption of Lubricants

G. O. Dotterer

Rev. Sci. Instrum. 42, 471 (1971); http://dx.doi.org/10.1063/1.1685133 (4 pages) | Cited 3 times

Online Publication Date: 4 November 2003

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An oxidation apparatus is described which continuously records the volume of oxygen absorbed by a sample of oil, in a closed system, maintained at constant temperature and pressure. The apparatus is automated through the use of a specially devised liquid level probe and other ancillary equipment such as recorders, timers, and temperature controllers. The apparatus can be used to compare the relative oxidation stability of various lubricants over a wide range of operating conditions.

A Mass Spectrometer for the Simultaneous Measurement of the Neutral and the Ion Composition of the Upper Atmosphere

H. Balsiger, P. Eberhardt, J. Geiss, and E. Kopp

Rev. Sci. Instrum. 42, 475 (1971); http://dx.doi.org/10.1063/1.1685134 (2 pages) | Cited 3 times

Online Publication Date: 4 November 2003

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A mass spectrometer is described which measures the neutral and the ionized components of the upper atmosphere simultaneously (delay ∼20 msec). Its 1% mass resolution is 60 and its sensitivity is sufficient to measure small ion concentrations in the presence of high neutral gas densities. During rocket flights the shift in the mass scale between the ion peak and the corresponding neutral peak is a measure for the rocket skin potential.

A High Resolution Spectrometer for the Shorter Millimeter Wavelength Region

C. Huiszoon

Rev. Sci. Instrum. 42, 477 (1971); http://dx.doi.org/10.1063/1.1685135 (5 pages) | Cited 13 times

Online Publication Date: 4 November 2003

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A description is given of a molecular beam apparatus which extends high resolution absorption spectroscopy into the shorter millimeter wavelength region (up to 500 GHz). A parallel‐plate‐type absorption cell, allowing for Stark modulation, is used with the molecular beam passing between the plates. The half‐width of the absorption lines is about 5 kHz at a resonance frequency of about 200 GHz.

Development of a Compton Polarimeter with Solid State Detectors

K. A. Hardy, A. Lumpkin, Y. K. Lee, G. E. Owen, and R. Shnidman

Rev. Sci. Instrum. 42, 482 (1971); http://dx.doi.org/10.1063/1.1685136 (3 pages) | Cited 14 times

Online Publication Date: 4 November 2003

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A two‐section Compton polarimeter has been developed out of a single Ge☒Li detector. This device has nearly the same asymmetry ratio as the three‐section polarimeter described previously, but has the advantage of a high efficiency. The asymmetry ratio of the device is calculated as a function of gamma ray energy. The polarimeter is also calibrated by gamma rays of known polarization from reactions 24Mg(p,p′) and 28Si(p,p′).

An Inexpensive Energy Filter Lens for Large Diameter Electron Beams

H. D. Zeman, K. Jost, and S. Gilad

Rev. Sci. Instrum. 42, 485 (1971); http://dx.doi.org/10.1063/1.1685137 (5 pages) | Cited 26 times

Online Publication Date: 4 November 2003

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The theory behind the use of a rotationally symmetric hyperbolic electrostatic field as an energy filter lens for electrons is discussed. The design of such a lens for use in eliminating inelastically scattered electrons from the output beam in a low energy electron scattering experiment is described. A filter lens designed, built, and tested by the authors is described. It has an entrance aperture of 1.27 cm diameter, an angular acceptance of ±2°, and a measured energy cutoff width of (0.27±0.02)%.

A New Double Beam Optical Lever Refractometer and the Variation of the Refractive Index of NaCl with Temperature

F. N. D. D. Pereira and A. C. Hollis Hallett

Rev. Sci. Instrum. 42, 490 (1971); http://dx.doi.org/10.1063/1.1685138 (4 pages) | Cited 1 time

Online Publication Date: 4 November 2003

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The design and construction of a double beam optical lever are described. Its use is illustrated by describing an experiment to measure changes of the order of 10−5 in the refractive index of NaCl by the method of measuring the change in angle of refraction of a beam of light by a prism of the salt. It is capable of higher sensitivities and has the advantage that it can monitor the motion of the crystal as a whole.

Vacuum Manifold for Rapid Assay of Enzymes Using Radioactive Tracers and Ion Exchange Chromatography

Stanley B. Prusiner, Larry S. Milner, Carl W. Long, and Murrel L. Myers

Rev. Sci. Instrum. 42, 493 (1971); http://dx.doi.org/10.1063/1.1685139 (2 pages)

Online Publication Date: 4 November 2003

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A vacuum manifold apparatus is described which allows rapid ion exchange chromatography of multiple samples. The apparatus is especially applicable to the assay of enzymes by radioisotopic tracer methods.

A Capacitive Gauge for the Accurate Measurement of High Pressures

Carl Andeen, John Fontanella, and Donald Schuele

Rev. Sci. Instrum. 42, 495 (1971); http://dx.doi.org/10.1063/1.1685140 (2 pages) | Cited 5 times

Online Publication Date: 4 November 2003

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A highly accurate and precise pressure gauge, which utilizes the 35°C, 2005 Hz dielectric constant of an ionic crystal CaF2, is presented. The prototype gauge was calibrated at the National Bureau of Standards over the pressure range 0–2.5 kilobars, and the defining equation was found to be
math
,where C0 is the zero pressure capacitance, C is the capacitance at absolute pressure P, and the characteristic constants A and B are
math
and
math
.The gauge is stable and accurate over this range at the 0.01% level, and indications are that this type of gauge may be useful at much higher pressures and refined to even higher accuracies.
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