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Aug 1966

Volume 37, Issue 8, pp. 991-1102

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Anticoincidence Shielded Gamma‐Ray Spectrometer for Nuclear Reaction Studies

Albert E. Evans, Bernard Brown, and Jerry B. Marion

Rev. Sci. Instrum. 37, 991 (1966); http://dx.doi.org/10.1063/1.1720435 (9 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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A scintillation spectrometer has been built utilizing a modular liquid scintillation anticoincidence shield for a 12.7 cm diameter by 25.4 cm long NaI(Tl) detector crystal. The effectiveness of the anticoincidence shield is enhanced by storing in one‐half of a multichannel analyzer memory those pulses from the NaI(Tl) crystal which are coincident with shield pulses. A fraction of this coincident spectrum is then subtracted from the anticoincident spectrum as a correction for shield inefficiency. A computer system is used for data handling. Spectral response for gamma radiation from 0.35 to 17.6 MeV has been measured.

Apparatus for Determining Creep Behavior Under Conditions of Ultrahigh Vacuum

R. W. Buckman and J. S. Hetherington

Rev. Sci. Instrum. 37, 999 (1966); http://dx.doi.org/10.1063/1.1720436 (5 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A system for determining the creep behavior of refractory metals at temperatures up to 1900°C and at environmental test pressures of less than 1×10−8 Torr are described. Results are presented which show that contamination of a tantalum alloy test specimen is inhibited when tested at 1370°C and 1×10−8 Torr.

Stereoscopic Viewer for Measuring Positions and Angles in Three Dimensions

E. W. Cowan

Rev. Sci. Instrum. 37, 1004 (1966); http://dx.doi.org/10.1063/1.1720391 (3 pages)

Online Publication Date: 29 December 2004

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An optical device is described that is used for the measurement of the positions and angular coordinates of lines viewed in stereoscopic photographs, such as the photographs of particle tracks in a cloud chamber or bubble chamber. In addition to the absolute angular coordinates of a line in three dimensional space, the viewer furnishes the relative angular coordinates of a second intersecting line and the three rectangular coordinates of the point of intersection. All coordinates are read directly on linear scales. Applications include the measurement of scattering angles, the angles of secondary particles in an interaction or decay with respect to each other and the primary particle, and the angle of traversal of a particle through an absorber.

Precision Technique for Measuring Asymmetric Distortions in Optical Lenses

Jack Hohenstein

Rev. Sci. Instrum. 37, 1007 (1966); http://dx.doi.org/10.1063/1.1720392 (4 pages)

Online Publication Date: 29 December 2004

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Apparatus and techniques were developed for accurately measuring asymmetric distortion in camera lenses. Great care was taken in fabricating the camera, which was made cylindrical so that the lens could be rotated. The experimental setup included a collimating telescope, the cylindrical camera containing the lens to be tested, and the test pattern. By rotation of the cylindrical camera, the same portion of the test pattern could be used for checking asymmetric distortion in different sectors of the lens. The distortion was recorded on film plates, which were then measured with a linear micrometer. Results were obtained to an accuracy of 1 part in 105. Causes for distortion were investigated but not quantitatively.

Improved Precision Ice Calorimeter

Jack Opdycke, Charles Gay, and Hartland H. Schmidt

Rev. Sci. Instrum. 37, 1010 (1966); http://dx.doi.org/10.1063/1.1720393 (4 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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An improved Bunsen ice calorimeter has been constructed and calibrated for use in measuring critical region heat capacities. A novel method for continuously monitoring the weight of the mercury displaced by using a flexible capillary between the calorimeter and an analytical balance makes possible greater precision, easier operation, and wider applicability of the ice calorimetric method. An improvement in the method of thermostating the calorimeter allows higher precision over long period heat measurements. The measured electrical calibration factor of 270.45±0.03 J∕g Hg agrees satisfactorily with previous very careful calibrations and the observed precision of ±0.011 J∕g Hg is easily attainable during electrical calibrations. Relatively simple improvements in other aspects of the calorimeter are suggested for increasing both the precision and accuracy significantly.

Apparatus for Electron Irradiation Studies at Low Temperatures

R. L. Chaplin

Rev. Sci. Instrum. 37, 1014 (1966); http://dx.doi.org/10.1063/1.1720394 (5 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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To pursue accurate quantitative studies of radiation effects in crystals, it is necessary to adopt precise experimental techniques for controlling the bombarding electrons and for cooling specimens to very low temperatures. With regards to the irradiating electron beam, measurements have been made to determine some of the factors which influence the electron flux density over the irradiated area, and a description is given of a system which insures precise alignment of the beam with respect to the specimens. A sample holder is described which provides good thermal contact and good electrical isolation between specimen and specimen holder at low temperatures. The method used for regulating the temperature of the sample holder depends upon adjusting the rate and the amount of helium vapor flow through the holder and data that indicate how these two adjustments govern the resultant temperature are presented.

Electron Densitometer for Irradiation Studies in Electron Microscope

T. P. Sciacca and A. G. Eubanks

Rev. Sci. Instrum. 37, 1019 (1966); http://dx.doi.org/10.1063/1.1720395 (2 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A probe assembly is described which permits the use of an electron microscope to irradiate materials with low energy (50–150 keV) electrons. The electron beam current produced by the microscope can be monitored quickly and accurately with this unit so that the irradiation rate can be closely controlled. Although developed for use in the Hitachi HU‐11 electron microscope, the device can, with but minor modifications, be utilized in other microscopes as well.

Sensitive Low Level Transistorized NMR Spectrometer Employing Frequency Modulation

Fred J. Blankenburg, Roy R. Knispel, and V. Hugo Schmidt

Rev. Sci. Instrum. 37, 1020 (1966); http://dx.doi.org/10.1063/1.1720396 (4 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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A transistorized NMR spectrometer has been developed which affords sensitivity comparable to that of the best vacuum tube spectrometers. This spectrometer has operated with sample coil voltages below 10 mV peak‐to‐peak. Frequency modulation is used to facilitate modulation at frequencies high enough to minimize effects of transistor 1∕f noise.

Alternating Current Losses and Magnetic Field Aberrations Associated with Use of High Field Superconducting Wire in Adiabatic Demagnetization Apparatus

A. C. Anderson, W. R. Roach, and R. E. Sarwinski

Rev. Sci. Instrum. 37, 1024 (1966); http://dx.doi.org/10.1063/1.1720397 (6 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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Experiments were conducted to determine ac losses, principally near 105 cps, in coils and leads fabricated from high field superconducting wires. The samples were placed in an environment similar to what might be experienced in actual use in a low temperature experiment utilizing adiabatic demagnetization. The measurements showed that losses associated with the use of high field superconducting wire could be less than for electrical grade copper wire. Further experiments were then carried out to determine what aberrations of magnetic fields would be caused by the presence of high field superconducting material.

Optimum Current Distribution in Superconducting Coils

J. E. C. Williams

Rev. Sci. Instrum. 37, 1030 (1966); http://dx.doi.org/10.1063/1.1720398 (2 pages)

Online Publication Date: 29 December 2004

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A superconducting winding, sectioned and supplied with currents corresponding to the local field conditions, gives an increased field contribution over that of a single winding. This paper derives the increased field contribution in terms of the number of sections and the characteristics of the superconducting material.

Cranz‐Schardin Multisource Spark Camera Systems

Sabodh K. Garg and Julius Siekmann

Rev. Sci. Instrum. 37, 1032 (1966); http://dx.doi.org/10.1063/1.1720399 (2 pages)

Online Publication Date: 29 December 2004

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A multisource spark camera of the Cranz‐Schardin type is described. Various applications, limitations, and alternatives are discussed.

Transverse Microwave Cavity Technique for Sensitive Measurement of Transient Electron Density Distributions

M. J. Lubin

Rev. Sci. Instrum. 37, 1034 (1966); http://dx.doi.org/10.1063/1.1720400 (5 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A high resolution transverse microwave probing technique is described utilizing radiating slots cut in an oversize waveguide containing the plasma. General expressions for the transmission coefficient of the doubly infinite cavity are derived and applied to the measurement of precursor electron density distributions in an electromagnetic shock tube. The results compared favorably with the results of other independent measurements.

Nuclear Magnetic Resonance Probe for Calibrating Superconducting Solenoids

L. W. Rupp

Rev. Sci. Instrum. 37, 1039 (1966); http://dx.doi.org/10.1063/1.1720401 (3 pages) | Cited 9 times

Online Publication Date: 29 December 2004

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A cesium metal NMR probe, which can be used directly with a Varian fluxmeter at liquid helium temperatures, has been developed. Such a device is generally useful in accurately calibrating magnetic fields to better than 1 G in the range 7600 to 60 000 G typical of currently available superconducting solenoids.

Rapid Photometric Method for Increasing Precision of Layer Thickness Measurement by Angle Lap Technique

R. H. Dudley and T. H. Briggs

Rev. Sci. Instrum. 37, 1041 (1966); http://dx.doi.org/10.1063/1.1720402 (4 pages)

Online Publication Date: 29 December 2004

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A densitometer has been used for location of two beam reflected interference fringes in the measurement of layer thicknesses. Routine measurements of layers of approximately 3000 Å thick were repeatable within less than 350 Å. The precision depends primarily upon the quality of the sample preparation. Two instruments of widely different price and resolution were used, yielding essentially equivalent results. Photographic prints and transparencies were used as densitometer samples with equal success.

Polymer Degradation Dosimeter of Polyisobutylene in Heptane

A. Wendell Carriker

Rev. Sci. Instrum. 37, 1045 (1966); http://dx.doi.org/10.1063/1.1720403 (3 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A radiation dosimeter that utilizes a polymer solution is described. The viscosity of the solution is an inverse function of dose, and the dose range for a given range of viscosity can be adjusted by changing the concentration and molecular weight of the polymer solute. Several small vibrating transducers for measuring the change of viscosity were investigated. Since polyisobutylene in heptane is a non‐Newtonian solution low frequency transducers were most effective.

Construction of Presses for High Pressure Research

R. B. Gordon, L. F. Mike, and J. R. Vaišnys

Rev. Sci. Instrum. 37, 1047 (1966); http://dx.doi.org/10.1063/1.1720404 (2 pages)

Online Publication Date: 29 December 2004

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Large press frames such as are often required in high pressure research apparatus can be constructed from thin plates provided that frictional forces are used to distribute the load uniformly on all the plates. A method of achieving this distribution of load is described. The resulting structure is strong and rigid, cannot fail by fracture, and can be made without the use of heavy machine tools.

System for Observing Small Nonlinearities in Tunnel Junctions

J. G. Adler and J. E. Jackson

Rev. Sci. Instrum. 37, 1049 (1966); http://dx.doi.org/10.1063/1.1720405 (6 pages) | Cited 128 times

Online Publication Date: 29 December 2004

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A system using a combination of harmonic detection and bridge techniques for the measurement of dV∕dI and d2V∕dI2 of superconducting tunnel junctions having resistances ranging from a few ohms to several thousand ohms is described. These quantities are of fundamental interest in the study of the density of electron states and phonon spectra of superconductors. This system is capable of determining σ=(dV∕dI)n∕(dV∕dI)s, the relative dynamic conductance, where dV∕dI is the dynamic resistance of the junction in the normal (n) and superconducting (s) state to within a few parts in 105. This high resolution is achieved using very small modulation levels of 60 μV rms (kT at 1°K=86 μV rms) or less. Finally, circuitry for obtaining dI∕dV in the region near the energy gap using extremely low modulation levels (5 to 10 μV rms) and capable of resolving the negative resistance region is also presented. Typical data obtained with this system are shown.

Versatile High Temperature Furnace

Paul Wagner

Rev. Sci. Instrum. 37, 1054 (1966); http://dx.doi.org/10.1063/1.1720406 (6 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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Past experiences in making a variety of thermal and physical measurements at high temperatures have resulted in a general furnace design which has proved to be quite successful for a variety of measurements. The operating range of the furnace described covers the temperature interval 750–2900°C. General design principles and details of construction for one of the furnaces are discussed. Several modifications of the furnace and some examples of the types of measurements which have been made are described.

Beryllium Pressure Bar Having Submicrosecond Risetime

Ieuan R. Jones

Rev. Sci. Instrum. 37, 1059 (1966); http://dx.doi.org/10.1063/1.1720407 (3 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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A pressure bar gauge was constructed from beryllium. The active element is a PZT polarized ferroelectric disk. The gauge was subjected to step pressure loading; the time taken for the output signal to increase from 10 to 90% of its final steady value is 0.54 μsec which is substantially faster than any other previously reported for a bar gauge.

Isothermal Drop Calorimeter for Alpha Active, Pyrophoric Materials

Howard Savage

Rev. Sci. Instrum. 37, 1062 (1966); http://dx.doi.org/10.1063/1.1720408 (3 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A copper block drop calorimeter to measure the heat content of intensely alpha active materials has been constructed. The furnace, calorimeter, and aluminum isothermal jacket are contained within an inert atmosphere glovebox. This permits the use of unencapsulated materials without exposing personnel to an alpha contamination hazard. The inert atmosphere also permits measurements to be made on materials which are pyrophoric in air. The apparatus is equipped with a suppressed range recorder to monitor continuously the resistance thermometer signal with a resolution of ±0.4 cal∕μV. Electrical calibration of the calorimeter yielded a precision of ±0.08% in the thermometer and recording system. The heat content of a sample of Calorimetry Conference sapphire obtained from the National Bureau of Standards was measured, and the results deviated from the Bureau's reported data a maximum of 1.0% at 1008°K. The useful range of the apparatus extends from 306 to about 1450°K.

Scyllacita—Compact High Voltage Theta Pinch Machine

E. L. Kemp, E. M. Dolnick, R. S. Dike, G. A. Sawyer, and J. L. Tuck

Rev. Sci. Instrum. 37, 1065 (1966); http://dx.doi.org/10.1063/1.1720409 (4 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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A high voltage theta pinch (Scyllacita) has been developed especially for application to experiments with explosively compressed theta pinches. The system is relatively economical, simple, and compact. Twenty‐four 14 μF, 20 kV, low inductance capacitors (60 kJ) are divided into two banks. Each capacitor has a 3 element spark gap (trigatron) mounted directly on it. Twelve low inductance cables from each capacitor spark gap combination are connected to a mix header which puts the two banks of capacitors in series when the gaps fire. One‐hundred low inductance cables connect the mix header to a collector plate and thus to the 8 cm diam, 24 cm long load coil. The source inductance (coil terminals shorted) is 17 nH. Both mirror coils and straight bore coils have been used. With the straight bore coil, the full period of oscillation is 11.7 μsec and the efficiency of energy transfer to the coil is 59%. In second half‐cycle operation at 100 mTorr filling pressure with the banks charged to 18 kV, over 107 neutrons per discharge are produced in either mirror or straight coil.

Laser Used for Mass Analysis

N. C. Fenner and N. R. Daly

Rev. Sci. Instrum. 37, 1068 (1966); http://dx.doi.org/10.1063/1.1720410 (3 pages) | Cited 15 times

Online Publication Date: 29 December 2004

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The focused beam from a `giant pulse' laser has been used to vaporize and ionize thin samples of solid material and so provide the ion source of a time of flight mass spectrometer. Ions produced in this way have an energy spread of 0–500 V and this has necessitated employing an energy filter to obtain a resolution of about 30. Samples of 10−9 g from metal foils have been successfully analyzed and have shown comparable ionization efficiencies for a large number of metals. When this technique was applied to the analysis of crystals of organic compounds only atomic ions were observed and although the ionization efficiency of the metal atoms is again comparable, the efficiency of the other components depends critically on the power of the laser beam.

Apparatus and Techniques for Retention and X‐Ray Examination of Metastable High Pressure Phases at 4.2°K

T. R. R. McDonald, G. S. Barberich, V. T. Cunicella, and E. Gregory

Rev. Sci. Instrum. 37, 1071 (1966); http://dx.doi.org/10.1063/1.1720411 (6 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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Apparatus and techniques are described for retaining high pressure phases in a metastable state at atmospheric pressure and 4.2°K, and for examining them by x‐ray diffraction at this temperature. The apparatus consists of a press capable of exerting a pressure of about 50 kbar on small quantities of sample material, and a cryostat which permits x‐ray diffraction photographs to be taken of a specimen transferred from the press and immersed in liquid helium. Diffraction data are presented for the halite modification (NaCl type) of AgI retained at 4.2°K and atmospheric pressure, and mention is made of the retention of a metastable high pressure phase of gallium.
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Trigger Signal Generator for Use with Source of Charged Water Drops

W. R. Atkinson and C. E. Abbott

Rev. Sci. Instrum. 37, 1077 (1966); http://dx.doi.org/10.1063/1.1720412 (1 page)

Online Publication Date: 29 December 2004

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Technique for Measuring Dielectric Loss Tangent

Glenn A. Burdick and Travis G. Hickman

Rev. Sci. Instrum. 37, 1077 (1966); http://dx.doi.org/10.1063/1.1720413 (2 pages)

Online Publication Date: 29 December 2004

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