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Jun 1954

Volume 25, Issue 6, pp. 537-616


The Radio‐Frequency Fine Structure of the Photon Beam from the Berkeley Synchrotron

Richard Madey, Kenneth C. Bandtel, and Wilson J. Frank

Rev. Sci. Instrum. 25, 537 (1954); http://dx.doi.org/10.1063/1.1771126 (4 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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The full energy spread‐out bremsstrahlung beam of the Berkeley synchrotron was shown to be emitted in sharp bursts with the 47.7‐Mc∕sec frequency of the electrons in the doughnut. A two‐counter telescope, located about 20 inches away from a one‐fourth inch thick lead target and about 20 degrees from the photon beam direction, was used to measure an accidental coincidence counting rate as a function of the length of delay line in one input to the coincidence circuit. When the length of delay cable was chosen equal to integral multiples of the period of the radio‐frequency oscillator, the coincidence counting rate was of the order of 100 counts per unit of integrated beam; on the other hand, when the length of delay line was chosen to be equal to one‐half of odd integral multiples of the period of the radio‐frequency oscillator, the coincidence counting rate was less than about two counts per unit of integrated beam.
An estimate of the width of a single pulse of photons can be obtained from the measurement by unfolding a Gaussian resolution function of the coincidence circuit. If the time variation of the intensity of the photon beam is assumed to be a Gaussian function, then the rms value of that Gaussian is found to be less than 1.5×10−9 second.
A calculation by Lloyd Smith indicates that the measured radio‐frequency fine structure should provide a rather accurate picture of the phase‐stable bunch of electrons at the end of the acceleration period.

An Adiabatic Apparatus for the Study of Self‐Heating of Poorly Conducting Materials

Walter H. Raskin and Alexander F. Robertson

Rev. Sci. Instrum. 25, 541 (1954); http://dx.doi.org/10.1063/1.1771127 (4 pages) | Cited 5 times

Online Publication Date: 29 December 2004

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A small automatic furnace has been designed for the study of the thermal decomposition of wood and other combustible materials. After a sample has been brought nearly to thermal equilibrium at any desired temperature, the furnace temperature control system is automatically changed to allow the sample to self‐heat up to a temperature of 500°C with small external heat loss or gain. Weight changes of the specimen during the test are continuously monitored and recorded. The control system is designed to stop the operation automatically after the specimen temperature has increased to some previously selected level.

Mechanical Analog Computer for Reading Electron Diffraction Patterns

W. R. McMillan

Rev. Sci. Instrum. 25, 545 (1954); http://dx.doi.org/10.1063/1.1771128 (3 pages)

Online Publication Date: 29 December 2004

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An instrument, employing the principle of a slide multiplier, has been constructed for reading electron diffraction patterns and computing the corresponding crystal lattice spacings. The constant of the electron diffraction camera can have a value of from zero to 5.000 A cm, and the instrument can record ``dhkl'' spacings from 0.600 to 7.000 A. These spacings are printed, together with estimated line intensities, on adding machine paper. The instrument decreases the possibility of accidental error in copying numbers, and also eliminates considerable fatigue when many patterns have to be read.

Some Practical Aspects of Diffusion Cloud Chamber Operation

Margaret H. Alston, A. V. Crewe, and W. H. Evans

Rev. Sci. Instrum. 25, 547 (1954); http://dx.doi.org/10.1063/1.1771129 (5 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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Experimental problems which arise in the operation of diffusion cloud chambers are discussed. Particular attention is paid to methods of cooling the base of the chamber and design features of this type of chamber. Some of the limitations of the instrument are mentioned, and there is a discussion of symptoms which can arise when the conditions of operation are defective.

High‐Intensity Ion Source for Cyclotrons

Robert S. Livingston and Royce J. Jones

Rev. Sci. Instrum. 25, 552 (1954); http://dx.doi.org/10.1063/1.1771130 (6 pages) | Cited 12 times

Online Publication Date: 29 December 2004

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The mechanical design features and operating characteristics of a hot‐cathode arc‐discharge type ion source are described. Proton currents of 500 milliamperes have been obtained under dc test conditions. A maximum current of 3 milliamperes of 22‐Mev protons has been obtained with the source installed in the ORNL 86‐inch cyclotron. Distinguishing features of the ion source are its arc chamber of carbon, its heavy tantalum filament heated with dc, and its use of a specially shaped accelerating electrode.

A Fast Neutron‐Scintillation Spectrometer

J. E. Draper

Rev. Sci. Instrum. 25, 558 (1954); http://dx.doi.org/10.1063/1.1771131 (5 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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A fast neutron‐scintillation spectrometer employing two organic crystals in coincidence has been investigated experimentally. Considerations are made of some factors involved in the efficiency, resolution, neutron energy range, and background effects. The role of the carbon in the scintillation crystal is considered not to be important except in its increase of the plural scattering in the analyzing crystal. The D(d,n), T(d,n), and Li(d,n) spectra as taken with this instrument are presented.

Two Ion Sources for the Production of Multiply Charged Nitrogen Ions

Royce J. Jones and Alexander Zucker

Rev. Sci. Instrum. 25, 562 (1954); http://dx.doi.org/10.1063/1.1771132 (5 pages) | Cited 9 times

Online Publication Date: 29 December 2004

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Two ion sources have been developed for the production of milliamperes of N+, N2+, N3+, and N4+ ions. Under good operating conditions, 28 ma of N3+ and 10 ma of N4+ are produced. Details of source construction are given and a method for analyzing the source output is presented. Characteristics of both sources as a function of arc current and arc voltage are investigated.

Stereoscopic Reprojection and Radius of Curvature Measurements of Cloud‐Chamber Tracks

C. R. Emigh

Rev. Sci. Instrum. 25, 567 (1954); http://dx.doi.org/10.1063/1.1771133 (3 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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A means of accurately and rapidly measuring the radii of curvature of many cloud‐chamber tracks is described. The apparatus includes a photographing‐reprojecting system and a curvature‐measuring device. This device is capable of measuring radii of reprojected tracks in the range from 0.5 cm to 100 cm with the poorest accuracy of the order of 3 percent occurring at 100 cm.

A High Precision Electron‐Diffraction Unit for Gases

L. O. Brockway and L. S. Bartell

Rev. Sci. Instrum. 25, 569 (1954); http://dx.doi.org/10.1063/1.1771134 (7 pages) | Cited 23 times

Online Publication Date: 29 December 2004

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An electron‐diffraction unit incorporating a rotating sector has been developed which makes possible the accurate and objective measurement of the intensity of electrons diffracted by free atoms and molecules. The diffraction data afforded are sufficiently precise to permit the calculation of the distribution of electrons in atoms and the amplitude of vibration of atoms in molecules, as well as interatomic distances that are comparable in accuracy in suitable cases to those obtained by microwave spectroscopy. A description of the essential components of the unit is given together with some data on performance and discussion of the use of the apparatus.

A New Apparatus for the Partitioning of Expired Air of Small Animals

Paul E. Palm, Kenneth M. Cook, Jack H. U. Brown, and Theodore Hatch

Rev. Sci. Instrum. 25, 576 (1954); http://dx.doi.org/10.1063/1.1771135 (4 pages)

Online Publication Date: 29 December 2004

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A mechanical respirator with synchronized respiratory partitioning valve for guinea pigs is described. This apparatus is used for the separate determination of dust retention in the upper respiratory tract and deep lung spaces. The partitioning valve separates the exhaled air into three fractions beginning with the earliest portion of upper respiratory air and continuing to the terminal fraction of deep lung air. The same volumetric fractions from successive exhalations are collected over a test period of any practical duration. In principle, the apparatus is similar to one previously described (Rev. Sci. Instr. 22, 81, 1951) for the study of dust retention in human lungs.

A Stable Wide‐Range DC Amplifier

Franklin F. Offner

Rev. Sci. Instrum. 25, 579 (1954); http://dx.doi.org/10.1063/1.1771136 (8 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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A versatile high‐gain dc amplifier for biological applications is described. Its features include differential push‐pull operation with a rejection ratio greater than 1000; response from zero to beyond 30 kc with a maximum gain of about 2.5×106; optional control of high‐ and low‐frequency cutoff (the dc gain can be reduced to 1 percent of the mid‐band gain). For applications requiring exceptional stability, an automatic rebalancing circuit is provided which resets the zero of the amplifier at intervals of about 5 seconds. The equipment is ac‐operated.

Regenerative Deflection as a Parametrically Excited Resonance Phenomenon

S. E. Barden

Rev. Sci. Instrum. 25, 587 (1954); http://dx.doi.org/10.1063/1.1771137 (7 pages)

Online Publication Date: 29 December 2004

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The phenomenon termed regenerative deflection is treated as a resonance mechanism forming only one of a larger class of similar mechanisms. Conditions of optimum coupling to promote the growth of radial oscillations are described, and the results of some numerical calculations are given. The causes of the axial spreading of the beam during the extraction period are analyzed, and methods of reducing such spreading are discussed. An electrodynamic system for creating the coupling inhomogeneities is also described.

Shorting and Field Corrections in Hall Measurements

W. F. Flanagan, P. A. Flinn, and B. L. Averbach

Rev. Sci. Instrum. 25, 593 (1954); http://dx.doi.org/10.1063/1.1771138 (3 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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See Also: Erratum

Show Abstract
A method is given for correcting the measured Hall voltage for shorting by the current contacts and for inhomogeneities in the applied magnetic field. This method is applied to measurements of the Hall coefficient in gold‐silver alloys.

A Laboratory Arc‐Melting Furnace

Morris L. Nielsen and I. B. Johns

Rev. Sci. Instrum. 25, 596 (1954); http://dx.doi.org/10.1063/1.1771139 (3 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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Using a glass resin kettle as enclosure, and an inverted‐J electrode, a small arc‐melting furnace was designed for conveniently melting metals under an inert atmosphere.

An Analytical Balance for Recording Rapid Changes in Weight

Floyd A. Mauer

Rev. Sci. Instrum. 25, 598 (1954); http://dx.doi.org/10.1063/1.1771140 (5 pages) | Cited 17 times

Online Publication Date: 29 December 2004

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An analytical balance has been modified by adding a solenoid and magnet so that changes in weight can be balanced electrically. The operation is made automatic by reflecting a beam of light from the balance beam into a dual phototube in a bridge circuit and amplifying the output of the bridge to provide current in the solenoid. Recording the voltage drop across a resistor in series with the solenoid gives a linear weight scale which can be made to read directly in milligrams. An electronic damping circuit enables the balance to follow very rapid changes in weight without oscillating and with an accuracy better than 0.5 percent of full scale for ranges of 100 mg and over.

Magnetic Measurement of Torque in a Rotating Shaft

Richard A. Beth and Wilkison W. Meeks

Rev. Sci. Instrum. 25, 603 (1954); http://dx.doi.org/10.1063/1.1771141 (5 pages) | Cited 10 times

Online Publication Date: 29 December 2004

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In a cylindrical shaft under pure torsion the principal stress lines are 45° helices around the axis, one for tension and the other for compression. These are also the directions of maximum and opposite permeability changes for a shaft of magnetostrictive material. Based on these ideas a magnetic torque measuring device has been devised and tested. It consists of an external magnetic yoke carrying a driving coil and pickup coils on each of several branches to detect the permeability changes in flux paths lying in or near the principal stress directions in the shaft. Linear response, good sensitivity and fair stability have been obtained with rotating shafts.

An Efficient Cryostat for Producing Temperatures Between 4° and 80°K: The Production of Liquid Hydrogen Targets Using Liquid Helium

C. A. Swenson and R. H. Stahl

Rev. Sci. Instrum. 25, 608 (1954); http://dx.doi.org/10.1063/1.1771142 (4 pages) | Cited 38 times

Online Publication Date: 29 December 2004

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The cooling of apparatus using liquid helium can be made a much more efficient process if the total heat content of the evaporating gas is used in addition to the latent heat of vaporization of the liquid. Two cryostats for use on very different problems which make use of this principle are described. The first cryostat was used to maintain temperatures between 4° and 80°K in an application with very high heat influxes. The second cryostat, made necessary by restrictions on the manufacture of liquid hydrogen, used liquid helium both to condense a liquid hydrogen cyclotron target, and to maintain the target at temperatures near 20°K.
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Dynamic Heart‐Body Simulator

Ernest Frank

Rev. Sci. Instrum. 25, 611 (1954); http://dx.doi.org/10.1063/1.1771143 (5 pages)

Online Publication Date: 29 December 2004

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A high‐speed electronic analog computer is described which is a useful research tool in the analysis of body‐surface voltages produced by a fixed‐position, variable‐moment heart dipole. The simulator is capable of generating a wide variety of electric signals resembling presently‐accepted estimates of heart‐vector functions, forming body‐surface voltages from these signals using empirically determined coefficients, and manipulating these voltages so as to produce quantities of the type commonly dealt with in electrocardiography. The basic theory underlying the simulator is summarized, and a description of its components is presented. Typical uses are given for the case of studies using a heart dipole immersed in a homogeneous model of the human torso. The advantages and flexibility of this device are discussed along with its possible future application in the analysis of human heart signals.
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A Large‐Diameter Reciprocating‐Action Vacuum Valve

George L. Fox

Rev. Sci. Instrum. 25, 616 (1954); http://dx.doi.org/10.1063/1.1771144 (1 page)

Online Publication Date: 29 December 2004

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