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Mar 1964

Volume 35, Issue 3, pp. 263-415

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Synchrocyclotron 200‐Meter Flight Path Neutron Velocity Spectrometer

J. Rainwater, W. W. Havens, and J. B. Garg

Rev. Sci. Instrum. 35, 263 (1964); http://dx.doi.org/10.1063/1.1718804 (13 pages) | Cited 11 times

Online Publication Date: 29 December 2004

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Our synchrocyclotron neutron time‐of‐flight spectrometer now uses a 200‐m flight path and two 2000‐channel analyzers. The many important modifications and improvements described in this paper have been made as a result of operating experience. The present operation uses ∼20 nsec bursts at an instantaneous intensity ∼5×1018 evaporation neutrons per second and a 60‐cps repetition rate. The resolution for energies above 1 keV is now limited by the time analyzers which have 100‐nsec detection channel widths, giving a resolution of 0.5 nsec∕m in the keV region.

Apparatus for Obtaining Homogeneous Ingots

Frank Houzvicka, Sidney G. Parker, and Oran Wilson

Rev. Sci. Instrum. 35, 276 (1964); http://dx.doi.org/10.1063/1.1718805 (3 pages)

Online Publication Date: 29 December 2004

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An apparatus was built for casting several homogeneous, indium antimonide ingots of identical composition. The resulting ingots enabled one to study zone refining parameters.

Effect of Extended Fringing Fields on Ion‐Focusing Properties of Deflecting Magnets

Harald A. Enge

Rev. Sci. Instrum. 35, 278 (1964); http://dx.doi.org/10.1063/1.1718806 (10 pages) | Cited 24 times

Online Publication Date: 29 December 2004

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This paper presents the result of calculations on ion deflection and focusing in magnets that have realistic, extended fringing fields rather than sharply cutoff fringing fields. The most important effects of the change from sharp cutoff to extended fringing fields are (a) displacements of the beam center line at entrance and exit (a ``zeroth‐order'' effect), and (b) reduction of first‐order z‐direction (``vertical'') focusing. When the pole boundaries are curved or an effective curvature is caused by the proximity of pole‐piece corners, there are further first‐order effects on the trajectories. These effects can be minimized, and in practice made negligible, by correct centering of the beam relative to the pole‐piece corners at entrance and exit.

Pressure Gauge with One‐Tenth Microsecond Risetime for Shock Reflection Studies

D. Baganoff

Rev. Sci. Instrum. 35, 288 (1964); http://dx.doi.org/10.1063/1.1718807 (8 pages) | Cited 17 times

Online Publication Date: 29 December 2004

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A pressure gauge having a risetime of 0.1 μsec, no overshoot, a dwell time of 5 μsec, and capable of sensing a pressure jump of 10 mm Hg is described. Pressure‐time traces obtained with the gauge on the end wall of the 17‐in.‐diam low pressure shock tube at the Graduate Aeronautical Laboratories, California Institute of Technology, are presented showing details of the pressure profiles on the end wall for reflecting shock waves.

Flashing‐Light Spectrophotometer for Studying the Fast Reactions Occurring during Photosynthesis

Bacon Ke, R. W. Treharne, and C. McKibben

Rev. Sci. Instrum. 35, 296 (1964); http://dx.doi.org/10.1063/1.1718808 (5 pages) | Cited 17 times

Online Publication Date: 29 December 2004

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Details on the construction of a spectrophotometer for measuring fast absorption changes occurring during photo‐synthesis are described. Repetitive, intense light flashes with 20‐μsec duration were used to initiate the reaction. The pulse generator is capable of producing two flashes, either simultaneously or with variable time separation. The monochromatic monitoring light was split into the sample beam and the reference balancing beam. The photo‐multiplier outputs were fed to a differential circuit so that net absorption changes could be measured. Besides a wideband oscilloscope, a computer of average transients was also used to extract small signals from a high noise background. Thus, transient optical density changes as small as 0.0001 could readily be measured. The performance of the apparatus, especially in conjunction with the CAT computer, was illustrated with the absorption change at 515 mμ in Chlorella and spinach chloroplasts.

Two Versions of a Sliding Bar Vacuum Lock

A. J. H. Boerboom, A. P. De Jongh, and J. Kistemaker

Rev. Sci. Instrum. 35, 301 (1964); http://dx.doi.org/10.1063/1.1718809 (2 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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Two versions are described of a sliding bar vacuum lock for the introduction of solid samples into the ion source of a mass spectrometer. Sealing is obtained by three stage differential pumping without the use of gaskets. The first version, having a bar diameter of 25 mm, can be used up to 2‐kV accelerating voltage. The second one, having a 50‐mm diameter, is double acting and can be used up to 15 kV.

Effective Thickness of Two Birefringent Crystals for the Study of Natural Birefringence

M. Ziauddin and T. S. Narasimhamurty

Rev. Sci. Instrum. 35, 303 (1964); http://dx.doi.org/10.1063/1.1718810 (3 pages)

Online Publication Date: 29 December 2004

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A new optical technique using a birefringent compensator has been developed to study the natural birefringence of calcite and ADP. Experimental results are compared with those obtained by the usual banded spectrum technique. Application of this method for very highly birefringent substances is indicated.

Sliding Photometer Head for the Microspectrophotometer

William L. Evans

Rev. Sci. Instrum. 35, 305 (1964); http://dx.doi.org/10.1063/1.1718811 (2 pages)

Online Publication Date: 29 December 2004

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A sliding photometer head for a microspectrophotometer is described and illustrated in detail. This apparatus consists of a stationary table, a sliding photocell mount, and an adapter ring for the measuring ocular. The photocell mount is easily separated from the supporting stationary table which attaches to a photomicrographic bellows extension. Adjustable screws permit critical alignment. The relative simplicity, durability, ease of alignment, and ease of removal of the head from the microspectrophotometer constitute advantages of this apparatus.

Dynamic Adiabatic Calorimeter: An Improved Calorimetric Apparatus

Cyril Solomons and John P. Cummings

Rev. Sci. Instrum. 35, 307 (1964); http://dx.doi.org/10.1063/1.1718812 (4 pages)

Online Publication Date: 29 December 2004

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An apparatus and technique for the simple but rapid determination of specific and latent heat data are described. The apparatus records automatically the energy‐temperature plot for the sample on a conventional emf vs time strip‐chart recorder; most of the components required are commercially available. The calorimetric assembly embodies the major advantages of adiabatic, heat‐flow, differential‐thermal‐analysis, and thermal‐analysis calorimeters. An accuracy of ±2% can be readily attained; with some care, errors can be reduced greatly in many cases.

Torsion Pendulum Photometer

M. Stimler, Z. I. Slawsky, and R. E. Grantham

Rev. Sci. Instrum. 35, 311 (1964); http://dx.doi.org/10.1063/1.1718813 (3 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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An instrument is described for making fundamental measurements of high energies of pulsed laser beams. The principle of operation is the transfer of beam‐photon momentum to angular momentum of a double‐reflecting ballistic torsional pendulum. The operating pressure is below 5×10−5 mm Hg. The sensitivity is 2.55±0.04 cm∕J, and damping of initial oscillations before making a measurement is not required. In addition to providing the capability of simultaneous energy measurement and use of a laser beam, the measurements made with this instrument appear to be more accurate than with a commercial calorimeter used for comparison.

Apparatus for Stress‐Rupture Testing of Filaments in a Controlled Environment

R. W. Jech, R. H. Springborn, and D. L. McDanels

Rev. Sci. Instrum. 35, 314 (1964); http://dx.doi.org/10.1063/1.1718814 (2 pages)

Online Publication Date: 29 December 2004

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A stress‐rupture apparatus was designed and built for testing filaments and wires having a diameter of 20 mils or less in a controlled atmosphere to prevent oxidation. Four tests may be run simultaneously at different stresses and temperatures (to 1427°C), and the stress‐rupture life of each filament can be measured independently and automatically.

Pulsed Nuclear Resonance Apparatus

W. Gilbert Clark

Rev. Sci. Instrum. 35, 316 (1964); http://dx.doi.org/10.1063/1.1718815 (18 pages) | Cited 197 times

Online Publication Date: 29 December 2004

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The description of a complete pulsed nuclear resonance spectrometer suitable for experiments in solids is given. Its major features are the ability to operate at any frequency between 2 and 30 Mc, an rf pulse output power of 5 kW over most of this range, a receiving system recovery time of 5–10 μsec at 10 Mc, a sensitivity usually limited by thermal noise in the receiver coil, use of phase coherent detection, the availability of a wide variety of pulse sequences, and good long and short term stability of the entire system. Brief instructions for operating the apparatus are included. A method of using the ``boxcar'' integrator to record directly the steady‐state absorption (χ″) or dispersion (χ′) is explained.

Alpha Particle Energy Resolution in a Liquid Scintillator

Donald L. Horrocks

Rev. Sci. Instrum. 35, 334 (1964); http://dx.doi.org/10.1063/1.1718816 (7 pages) | Cited 16 times

Online Publication Date: 29 December 2004

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The resolution of alpha particles of different energies with a liquid scintillator system has been studied for alpha particle energies of 4–7 MeV. In this work the best obtained value of the energy spread, the full width at half‐maximum, of the pulse height distributions was 0.058 times the energy of the exciting alpha particle. The pulse height‐energy relation for alpha particles between 4 and 7 MeV was shown to be essentially linear but not directly proportional. The quenching effects of ethyl alcohol and di(2‐ethylhexyl) phosphoric acid were measured. The linewidth and relative pulse height response of the liquid scintillator system for alpha particle excitation were studied as a function of the height and cross sectional area of the sample.

Current Regulator for a 10 000‐A dc 7.5‐MW Magnet Power Supply

B. H. Smith, J. R. Atwood, and D. N. Lyon

Rev. Sci. Instrum. 35, 340 (1964); http://dx.doi.org/10.1063/1.1718817 (13 pages) | Cited 14 times

Online Publication Date: 29 December 2004

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Design and construction details are discussed for a dc current control system capable of a short term stability of a few parts in 106 and a long term stability of ∼2 parts in 105 when used in conjunction with conventional rotating dc generators powering loads with time constants of approximately 200 msec at levels up to 7.5 MW. Actual performance of the system at various power levels is discussed.

Nonlinear Twin‐T Network for Capacitive Transducers

Kurt S. Lion

Rev. Sci. Instrum. 35, 353 (1964); http://dx.doi.org/10.1063/1.1718818 (4 pages) | Cited 8 times

Online Publication Date: 29 December 2004

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A circuit is described which converts the capacitance variation of a capacitive transducer into analogous voltage and current signals. Direct current output voltages of the order of 10 V and dc currents in the milliampere range are obtained for a variation of capacitance of 10 pF. At maximum sensitivity, the output is practically independent of variations of the source frequency. Sensitivities of the order of 1000 V∕in. can be obtained when used with transducers for the measurement of small displacements.

Tensile Machine for Small Specimens

R. K. MacCrone, P. H. Thornton, and D. Kuhlmann‐Wilsdorf

Rev. Sci. Instrum. 35, 356 (1964); http://dx.doi.org/10.1063/1.1718819 (4 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A very sensitive and accurate tensile machine suitable for straining small single crystal specimens in the form of foils and wires is described. A load elongation curve of a gold foil is presented to show the performance achieved.

High Resolution Differential Čerenkov Counter

R. M. O'Donnell, D. H. Frisch, and S. R. Smith

Rev. Sci. Instrum. 35, 360 (1964); http://dx.doi.org/10.1063/1.1718820 (6 pages)

Online Publication Date: 29 December 2004

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A particularly simple high resolution differential Čerenkov counter has been constructed and tested in beams of positive particles of 3.75 and 6 BeV∕c momentum. The π meson, K meson, and proton peaks were well separated, and had full widths at half‐height of about 10−3 in Δβ. The total efficiency of the counter was 63%. The K peak to K‐π valley ratio was 200 to 1 at 3.75 BeV∕c and 375 to 1 at 6.0 BeV∕c. The limitations of the counter for use at higher momenta are discussed briefly.

Digital Technique for Rapid Measurement of Time Lags

D. F. Binns, R. J. Hood, and C. L. Dargan

Rev. Sci. Instrum. 35, 365 (1964); http://dx.doi.org/10.1063/1.1718821 (3 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A commercial 10‐Mc digital chronometer has been used to measure time lags to breakdown in SF6∕air mixtures. This method is much quicker than taking measurements from oscillograms and gives greater accuracy when a very wide range of time lags occurs for the same experimental condition. Precautionary measures against pickup from high voltage circuits are described, together with a method of producing pulses suitable for starting and stopping the chronometer.

Simple Technique for Introducing Electrical Leads into a High Pressure Vessel

L. A. Davis, R. B. Gordon, J. K. Tien, and J. R. Vaisnys

Rev. Sci. Instrum. 35, 368 (1964); http://dx.doi.org/10.1063/1.1718822 (3 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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Electrical leads can be easily sealed into a pressure vessel by the use of suitably prepared epoxy cement. This technique produces a high pressure plug capable of withstanding at least 24 000 atm of hydrostatic pressure. The vessel with which the plug is used is described briefly.

Liquid Scintillator Anticoincidence Guard

M. K. Moe, T. L. Jenkins, and F. Reines

Rev. Sci. Instrum. 35, 370 (1964); http://dx.doi.org/10.1063/1.1718823 (4 pages) | Cited 5 times

Online Publication Date: 29 December 2004

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A study was undertaken to determine the reduction in cosmic ray background which can be obtained by anti‐coincidence techniques. A 50‐liter liquid scintillation detector was set to register all cosmic ray events depositing more than 10 MeV. With a minimum shielding over the detector's basement location of 60 g∕cm2, all but one in 103 events were accompanied by a pulse greater than 100 keV in a 1500‐liter liquid scintillator anticoincidence guard. An additional 600 g∕cm2, in the form of 35 tons of concrete block and bags of iron ore over the detector and anti‐coincidence guard, reduced the unaccompanied events to 1 in 104, or 7.7 counts∕h through 0.35‐m2 effective horizontal area.

Fabry‐Perot Dilatometer

Virgil E. Bottom

Rev. Sci. Instrum. 35, 374 (1964); http://dx.doi.org/10.1063/1.1718824 (3 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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A dilatometer based upon the principle of the Fabry‐Perot interferometer is described. The device is capable of measuring displacements as small as 10−7 cm or less. The measurements are made directly in terms of the wavelength of a spectral line such as the green line of 198Hg. No calibration of the apparatus is required, and it is not necessary to know the distance between the mirrors or the focal length of the lens which forms the fringes. Neither is it necessary to know the calibration of the micrometer eyepiece so long as it may be assumed that the screw is regular. The instrument should be useful for measuring magnetostriction, piezoelectric, electrostriction, and thermal expansion coefficients, especially when small samples must be used.

Magnetic Tape Recording and Reproducing of Atmospheric Noise with a Wide Dynamic Range

Earl C. Bolton

Rev. Sci. Instrum. 35, 377 (1964); http://dx.doi.org/10.1063/1.1718825 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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To properly evaluate the performance of radio systems in the presence of atmospheric noise, it is necessary to be able to reproduce atmospheric noise of various known amplitude distributions whenever necessary. However, conventional tape recording techniques cannot be used because of the large dynamic range of atmospheric noise. This paper describes a tape recording and reproducing system which has been developed that can record and reproduce atmospheric noise with a dynamic range of 90 dB. The frequency range is 1 to 25 kc with a one‐half octave bandwidth and, by using frequency conversion, frequencies from 25 to 500 kc may be recorded with a maximum bandwidth of 10 kc.

Windowless X‐Ray Tube Spectrometer for Light Element Analysis

Ralph W. G. Wyckoff and Franklin D. Davidson

Rev. Sci. Instrum. 35, 381 (1964); http://dx.doi.org/10.1063/1.1718826 (3 pages) | Cited 8 times

Online Publication Date: 29 December 2004

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A windowless tube spectrometer is described for the x‐ray ``fluorescent'' analysis of the light elements down through fluorine. The high efficiency of x‐ray excitation makes possible the analysis of elements as light as sodium when present in less than 1% and of fluorine in larger amounts.

Pulse Generator System for Fast‐Reaction Experiments using a Time‐of‐Flight Mass Spectrometer

J. S. Riney and W. C. Gardiner

Rev. Sci. Instrum. 35, 384 (1964); http://dx.doi.org/10.1063/1.1718827 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A transistorized pulse generator system for chemical kinetics experiments with a time‐of‐flight mass spectrometer is described.

Correlation of I–V Characteristic with Noise for Ion Drifted p‐i‐n Junction Particle Detectors

Larry K. Monteith

Rev. Sci. Instrum. 35, 388 (1964); http://dx.doi.org/10.1063/1.1718828 (5 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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This paper describes a technique for achieving minimum noise in a p‐i‐n particle detector. The reverse saturation current of the detector and its relative noise are correlated for different surface treatments. The data show that the reverse current at the detector operating voltage is not a sufficient measure of relative noise. The relative noise can be predicted from the reverse current at two to three times the operating voltage.
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