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May 1959

Volume 30, Issue 5, pp. 315-378

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Simple Pulsed Neutron Source Based on Crossed‐Field Trapping

James D. Gow and Lawrence Ruby

Rev. Sci. Instrum. 30, 315 (1959); http://dx.doi.org/10.1063/1.1716611 (3 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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A simple pulsed neutron source has been constructed which consists of an anode formed by a cylindrical‐shell permanent magnet and of two disk cathodes. One of the cathodes forms the neutron‐producing target and the device is exhausted adjacent to the other. In operation, the anode is pulsed positive at 140 kv for 1 μsec at up to 200 pulses per sec. Continuous operation has also been achieved in a slightly different configuration. Ions are produced adjacent to the anode in a toroidal trapping region which exists as a result of the crossed electric and magnetic fields. The ionization is enhanced by the action of electrons reflecting through the inside of the magnetic shell. As a consequence of this trapping, large fluxes of soft x‐rays are created which may be injurious to personnel.

Rotating‐Disk Function Generator for Analog Computers

Mary Ellen Young, W. Merle Alexander, and Herbert D. Schwetman

Rev. Sci. Instrum. 30, 318 (1959); http://dx.doi.org/10.1063/1.1716612 (5 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A simple device for the production of varying potentials which represent four functions of the form f(t) = at, f(t)+at+b sinωt, f(t) = at2+b, and f(t) = a for (50 msec≤t≤100 msec) and a rate of operation of 5 cps is described. It makes use of a rotating disk of variable radius to control the light incident upon the cathode of a photomultiplier tube. The accuracy of the functions is about 4%, with the exception that near points of discontinuity, maximum errors of 4 to 10% were observed. The method of preparing the disk, use of the functions in the solution of linear, ordinary differential equations, and an analysis of the error are presented.

The Video Differential Planimeter

Michael Tobin

Rev. Sci. Instrum. 30, 323 (1959); http://dx.doi.org/10.1063/1.1716613 (5 pages)

Online Publication Date: 29 December 2004

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The video differential planimeter is an instrument which measures variations in the projected area of any remote object with the aid of a flying spot scanner or television camera system. The composite video signal, caused by the scanning of the object and its contrasting background, is shaped to yield a sequence of constant amplitude rectangular pulses that are negative going during a scan of the object, and positive going at all other times. The average of this sequence of pulses is obtained from a point on a bleeder resistance returned to the negative supply, and is fed into an integrator. The net integration voltage is read off and the integrator is returned to zero at the end of each field. If the object's projected area remains fixed, the sum of the positive and negative pulse areas entering the integrator will be constant. Hence, the change in integration voltage from field to field will be zero. If the object's projected area varies, the sum of the positive and negative pulses entering the integrator will change, and the readout voltage of the integrator will vary proportionately. The V.D.P. is applied here to the measurement of the vibration of a speaker cone, and to the measurement of the human respiration and plethysmogram.

Use of Operational Amplifiers in Precision Current Regulators

Karl Eklund

Rev. Sci. Instrum. 30, 328 (1959); http://dx.doi.org/10.1063/1.1716614 (4 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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The design and construction of precision current regulators is simplified by the use of commercially available operational amplifiers. Their method of use is described and an example is given of a regulator used with an electron spectrometer, where the regulation obtained was 0.01%. It is felt that the use of operational amplifiers offers a great convenience to the physics laboratory.

Use of Operational Amplifiers in Accelerator Beam Control Systems

Karl Eklund

Rev. Sci. Instrum. 30, 331 (1959); http://dx.doi.org/10.1063/1.1716615 (2 pages)

Online Publication Date: 29 December 2004

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A method of using operational amplifiers in beam control systems is described. A basic preamplifier is used with various output stages to control beam energy and position by magnetic and electrostatic means. The use of commercially available operational amplifiers provides great advantages in simplifying design, construction, and maintenance.

Redundant Circuitry for Reliability in Low‐Level Counting

W. H. Burke

Rev. Sci. Instrum. 30, 333 (1959); http://dx.doi.org/10.1063/1.1716616 (3 pages)

Online Publication Date: 29 December 2004

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This paper describes a system of redundant counting circuitry which has been used for about two years in carbon‐14 dating. The use of this circuitry enables the operator to know when a measured counting rate is unreliable because of electronic trouble, either steady or intermittent. It also enables him to continue taking reliable data despite most intermittent troubles and aids in locating them.

Design and Performance of a Hot Cathode Magnetically Collimated Arc Discharge Ion Source

Manlio Abele and Wolfgang Meckbach

Rev. Sci. Instrum. 30, 335 (1959); http://dx.doi.org/10.1063/1.1716617 (4 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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A hot cathode arc discharge type ion source is described. The discharge is collimated in an axial magnetic field and the ion beam is extracted axially. The maximum total ion current of the source, tested with hydrogen, is 42 ma. The extraction system allows focusing of almost 100% of this current. The limiting factor of the maximum ion current is analyzed. Although strong arc discharges could allow the extraction of higher ion currents, space charge spreading causes the ion beam to hit the front surface of the extracting electrode. Secondary electrons, released there, are focused back into the arc chamber producing instabilities of the source. A convenient means of regulation or modulation of the beam current is described. A magnetic analysis of the extracted beam shows about 34% atomic ion current.

Use of a Direct Current Amplifier and Recorder to Balance a Mueller Resistance Bridge

George T. Armstrong, P. K. Wong, and L. A. Krieger

Rev. Sci. Instrum. 30, 339 (1959); http://dx.doi.org/10.1063/1.1716618 (5 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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By taking corrective action for electrical noise resulting from alternating current pickup and induced electrostatic charges, it has been possible to use a commercially available high gain dc amplifier and a recorder to balance a G‐3 Mueller resistance bridge. Noise levels below 0.01 μv peak to peak were observed with a response time of approximately five seconds. Using a 25‐ohm platinum resistance thermometer and 1‐ma thermometer current, a precision of 0.0001°C was obtained in temperature measurement. The permanent and continuous record provided offers advantages over the ordinary optical galvanometer for the observation of time‐dependent phenomena and the study of sources of error.

X‐Ray Absorption Coefficients and Geometrical Collimation of the Beam

L. G. Parratt, J. O. Porteus, H. W. Schnopper, and T. Watanabe

Rev. Sci. Instrum. 30, 344 (1959); http://dx.doi.org/10.1063/1.1716619 (4 pages) | Cited 11 times

Online Publication Date: 29 December 2004

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In recent years, in order to achieve high angular collimation of an intense x‐ray beam in a measurement of an absorption coefficient, most investigators have used the action of a high‐resolving‐power monochromator to provide the collimation. In this case, if the absorber exhibits small‐angle scattering (including multiple scattering) of significant intensity in a scattering cone as large as a few seconds of arc, the value of the coefficient depends upon the absorber position with respect to the monochromator. A few measurements are reported with a two‐crystal spectrometer to illustrate the points discussed.

Recording Microwave Hygrometer

Jack Sargent

Rev. Sci. Instrum. 30, 348 (1959); http://dx.doi.org/10.1063/1.1716620 (8 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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A description is given of a microwave refractometer designed to measure and record the water vapor pressure in a moving air stream, particularly at very low vapor pressures. The instrument has a sensitivity of 0.004 mm Hg with a four decade range extending to 71.3 mm Hg vapor pressure. By means of microwave techniques the difference in refractive index between dry and humid air is determined and then converted to vapor pressure by an empirical formula. The instrument can be readily calibrated by the use of pure gases whose dielectric constants are precisely known. Because of the automatic null‐balancing technique used, the instrument has excellent calibration stability. Test results involving the measurement of known vapor pressures in the ranges of 0 to 0.15 mm Hg and 0 to 15 mm Hg are described. Possible applications of this instrument for the measurement of refractive index variation and its use for quality control are briefly discussed.

Permanent Magnet for Atomic Beam Focusing

R. L. Christensen and D. R. Hamilton

Rev. Sci. Instrum. 30, 356 (1959); http://dx.doi.org/10.1063/1.1716621 (3 pages) | Cited 11 times

Online Publication Date: 29 December 2004

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A compact six‐pole permanent magnet useful for focusing of atomic beams is described, together with the equations of motion of atoms in its field as used in its design. The method of construction, magnetization, and measurement of its field are discussed.

Rapid‐Opening Mechanical Gate Valve

B. P. Denardo and A. C. Charters

Rev. Sci. Instrum. 30, 359 (1959); http://dx.doi.org/10.1063/1.1716622 (2 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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The design of a rapid‐opening mechanical gate valve is revealed. Its operation and construction details are discussed, along with results of operational tests. In use, a port whose diameter is 1¼ in. can be completely opened in about 0.6 msec from the time a signal is fed to the valve unit.

Coaxial Displacement Dielectric Cell for Liquids Usable to 250 Mc

Stuart E. Lovell and Robert H. Cole

Rev. Sci. Instrum. 30, 361 (1959); http://dx.doi.org/10.1063/1.1716623 (2 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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A dielectric plunger displaces liquid filling a short section of coaxial line, and dielectric constant and loss are determined from changes in measured capacitance and conductance with displacement. Corrections for imperfect plunger fit, lead capacitance, and inductance are small and well defined, and procedures for making them are given. Dielectric constants from 3 to 300 and high losses can be measured from −70 to 100°C with 3 cc or less of sample.

Measurement of Nuclear Isomeric Half‐Lives in the Range from One Microsecond to Ten Milliseconds

I. E. Lindstrom and Bernd Crasemann

Rev. Sci. Instrum. 30, 363 (1959); http://dx.doi.org/10.1063/1.1716624 (4 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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Relatively simple and accurate delayed‐coincidence apparatus for the measurement of isomeric half‐lives in the millisecond range is described. Practical aspects of the statistics of delayed‐coincidence counting are discussed. Half‐life measurements of Ta181m (17.83±0.10 μsec) and Y88m (300.5±5.0 μsec) are described.
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Improved Design for Halogen‐Quenched End‐Window Geiger Counters

K. Van Duuren and J. Hermsen

Rev. Sci. Instrum. 30, 367 (1959); http://dx.doi.org/10.1063/1.1716625 (2 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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Abstract Unavailable

Proposed Geometry for an X‐Ray Camera

Dwight W. Berreman

Rev. Sci. Instrum. 30, 368 (1959); http://dx.doi.org/10.1063/1.1716626 (2 pages)

Online Publication Date: 29 December 2004

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Abstract Unavailable

Brazing Stainless Steel to Copper

Morris Liebson

Rev. Sci. Instrum. 30, 369 (1959); http://dx.doi.org/10.1063/1.1716627 (2 pages)

Online Publication Date: 29 December 2004

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Abstract Unavailable

Low‐Background Tungsten Filaments for Surface Ionization Mass Spectroscopy

J. W. Frazer, R. P. Burns, and G. W. Barton

Rev. Sci. Instrum. 30, 370 (1959); http://dx.doi.org/10.1063/1.1716628 (2 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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Abstract Unavailable

Liquid Nitrogen Liquid Level Controller

Rodger L. Gamblin, Ernest Goldberg, and Dane T. Scag

Rev. Sci. Instrum. 30, 371 (1959); http://dx.doi.org/10.1063/1.1716629 (1 page)

Online Publication Date: 29 December 2004

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Abstract Unavailable

Response of a Counting Rate Meter to an Input Signal A exp(−βt2)

P. M. Fitzpatrick and K. Hazel

Rev. Sci. Instrum. 30, 371 (1959); http://dx.doi.org/10.1063/1.1716630 (2 pages)

Online Publication Date: 29 December 2004

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Abstract Unavailable

Copper Welding for Maximum rf Conductivity

E. F. McLaughlin

Rev. Sci. Instrum. 30, 372 (1959); http://dx.doi.org/10.1063/1.1716631 (2 pages)

Online Publication Date: 29 December 2004

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Abstract Unavailable

Linear Gate of 20‐mμsec Duration

E. L. Garwin

Rev. Sci. Instrum. 30, 373 (1959); http://dx.doi.org/10.1063/1.1716632 (2 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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Abstract Unavailable

Time to Pulse‐Height Converter

John V. Kane

Rev. Sci. Instrum. 30, 374 (1959); http://dx.doi.org/10.1063/1.1716633 (2 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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Abstract Unavailable

Adjustment of X‐Ray Foci and Goniometers

J. Fridrichsons, A.McL. Mathieson, and G. M. Stiff

Rev. Sci. Instrum. 30, 375 (1959); http://dx.doi.org/10.1063/1.1716634 (1 page) | Cited 6 times

Online Publication Date: 29 December 2004

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Abstract Unavailable

Thermocouple Junction for a Hot‐Plate Linear Pyrolysis Apparatus

R. F. Chaiken and D. K. Van de Mark

Rev. Sci. Instrum. 30, 375 (1959); http://dx.doi.org/10.1063/1.1716635 (2 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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Abstract Unavailable
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