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Mar 1955

Volume 26, Issue 3, pp. 257-306


Precision Measurement of Detonation and Strong Shock Velocity in Gases

Herbert T. Knight and Russell E. Duff

Rev. Sci. Instrum. 26, 257 (1955); http://dx.doi.org/10.1063/1.1771269 (4 pages) | Cited 22 times

Online Publication Date: 29 December 2004

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A simple system is described for determining the velocity of detonation or strong shock waves, with temperatures above 3000°K, by using the conductivity behind the wave. Wave contact is made by two 36‐mil wires set 0.1 inch apart in a Teflon plug mounted in the experimental tube. When a wave passes, signals are produced across a 30‐K resistor in series with these wires and a 0.001 μf capacitor charged to 300 v. Any number of circuits may be paralleled across a single signal resistor if a diode is added to each circuit to prevent signal deterioration. The arrival time of a wave at a pin can be determined with an accuracy of almost 10−8 sec from an oscilloscope record of the signals. The principal advantages of this system are excellent space resolution and very simple basic circuitry. An amplifier is described which can be used with an individual pin circuit to fire a thyratron and extend the range of applicability of this system to waves with temperatures as low as 1000°K.

Range of 208±4‐Mev Protons in G5 Nuclear Emulsion

Hervasio G. De Carvalho and Jerome I. Friedman

Rev. Sci. Instrum. 26, 261 (1955); http://dx.doi.org/10.1063/1.1771270 (3 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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A range curve of the external beam of the University of Chicago synchrocyclotron was taken in G5 stripped nuclear emulsion. The range of this beam in copper was also measured in order to determine its energy. Having a mean range of 41.1±0.1 g∕cm2 of copper, the beam had an energy of 208±4 Mev according to Aron's tables. The mean range of the same beam in G5 nuclear emulsion at 47 percent relative humidity was 41.3±0.2 g∕cm2 which is about 1.2 percent longer than that from Heinz's measurements and about 1.3 percent shorter than that calculated by Vigneron. At 47 percent relative humidity the average density of the emulsion was measured to be 3.85±0.01 g∕cm3, in good agreement with the calculations of Wilkins.

Isothermal Processing of Thick Nuclear Emulsions

Herman Yagoda

Rev. Sci. Instrum. 26, 263 (1955); http://dx.doi.org/10.1063/1.1771271 (4 pages) | Cited 5 times

Online Publication Date: 29 December 2004

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A method for the processing of thick nuclear emulsions is outlined which develops the tracks of singly charged particles at the minimum of ionization without resort to a hot stage. The developing agent is introduced into the thick layer by means of a series of solutions varying in pH from 4.7 to 7.2 and of increasing reducing power. Uniform depth development is secured by allowing the last solution to diffuse out of the emulsion into water at 5°C. The processes of fixation and washing are designed to avoid resolution of surface silver grains, and to keep lateral swelling at a minimum. Turbidity resulting from residual silver iodide is reduced by means of a buffered thiourea solution. Thick unsupported emulsions can be restored to approximately their original size by leaching the electrolytes from the gelatin with a series of graded alcohols. The isothermal cold processing reduces distortion and facilitates the microscopic study of preparations up to 2 mm thickness by minimizing danger of overdevelopment and production of excessive fog.

New Technique for Compressing Surface Films

Irving H. Sher and J. D. Chanley

Rev. Sci. Instrum. 26, 266 (1955); http://dx.doi.org/10.1063/1.1771272 (3 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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A new method of applying continuous mechanical pressure to monomolecular films is presented. The advantages of the method include: simple and inexpensive apparatus, ability to produce continuously any desired pressure without adjustments, freedom from piston‐oil contaminations and streaks, ease and speed of cleaning surface for next film, and full spreading of successive films.

Proportional Counting of Carbon Dioxide for Radiocarbon Dating

H. R. Brannon, M. S. Taggart, and M. Williams

Rev. Sci. Instrum. 26, 269 (1955); http://dx.doi.org/10.1063/1.1771273 (5 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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Determinations of naturally occurring radiocarbon have been made with proportional counters filled with carbon dioxide at pressures up to 10 atmospheres. After chemical and radiochemical purification, the sample is converted into carbon dioxide for the counter filling. Extreme purity is required of the counter filling gas to prevent electron electron attachment by impurities. Procedures are described for producing carbon dioxide of sufficient purity to provide consistent and reproducible results. A counting efficiency of 100 percent is obtained for carbon‐14 betas contained in the active volume of the counter, giving a sample counting rate for the counter used of 45 cpm for contemporary material at a filling gas pressure of 10 atmospheres. With the present background of 13.5 cpm and a counting time limit of two days, dating may be extended to a maximum age limit of 42 000 years.

Electron Accelerator and High Resolution Analyzer

A. W. Blackstock, R. D. Birkhoff, and M. Slater

Rev. Sci. Instrum. 26, 274 (1955); http://dx.doi.org/10.1063/1.1771275 (2 pages) | Cited 14 times

Online Publication Date: 29 December 2004

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The principle of energy measurement by stopping potential has been extended to high‐energy electrons, using conventional accelerating tubes. Defocusing effects which occur during deceleration are minimized by employing a low energy cylindrical electrostatic analyzer to measure the energy remaining in the beam after deceleration has been almost complete. The width of the line profile obtained by this technique appears to be largely independent of the primary energy of the electrons, the percent resolution thus improving as the primary energy is increased. Resolution up to 20 parts per million at 100 kev is obtainable by this method.

Apparatus for Measuring the Thermal Conductivity of Metals in Vacuum at High Temperatures

Marvin Moss

Rev. Sci. Instrum. 26, 276 (1955); http://dx.doi.org/10.1063/1.1771276 (5 pages) | Cited 3 times

Online Publication Date: 29 December 2004

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The method of determining the thermal conductivity of a metal with this apparatus consists, essentially, of measuring both the axial temperature gradient and the transfer of heat under steady state conditions in a thermally shielded cylindrical rod of the metal which is heated at one end and cooled at the other. The objective was to make precise determinations of conductivity without reliance on previously established data for standard metals. In certain respects the apparatus embodies simplification of, and improvement over, other equipment of this type. A calorimetric measurement of heat flow constitutes a distinct advantage of the instrument both as to its simplicity and the fact that it supplies the data necessary for a direct rather than a comparative evaluation of thermal conductivity. Other features include vacuum operation and special instrumentation to facilitate the measurement of temperature differences. Tests have been made on nickel, zirconium, and a zirconium‐3‐percent‐tin alloy from room temperature up to the range between 500 and 700°C. Where comparison is possible the results are in close agreement with some of the most accurate published data of this type.

Miniature Bomb Calorimeter for the Determination of Heats of Combustion of Samples of the Order of 50 mg Mass

William S. McEwan and Carl M. Anderson

Rev. Sci. Instrum. 26, 280 (1955); http://dx.doi.org/10.1063/1.1771277 (5 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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A new bomb calorimeter for the combustion of very small quantities of organic materials has been constructed. The use of a small sample size is particularly important when dealing with explosive materials which when used in larger quantities, may detonate enough to spatter material from the crucible or when using substances which are difficult to prepare and purify in larger amounts. This calorimeter has several unique design features including a light weight bomb, coaxial stirrer, and flame holding sample holder.

Direct Reading Analyzer for Short Time Intervals

G. K. O'Neill

Rev. Sci. Instrum. 26, 285 (1955); http://dx.doi.org/10.1063/1.1771278 (6 pages) | Cited 8 times

Online Publication Date: 29 December 2004

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A time‐analyzer with nine 4.6 mμsec channels has been developed. It is based on the chronotron principle, but presents data directly on mechanical registers. The device is compact, stable, and easy to adjust. Variation of channel boundaries is less than 5×10−10 sec over long periods. Construction is such that changes in the time scale can be made, and even narrower channel widths should be possible. The principle is applicable to analyzers of more than nine channels.

Continuous Analysis of Ortho‐Parahydrogen Mixtures

D. H. Weitzel and L. E. White

Rev. Sci. Instrum. 26, 290 (1955); http://dx.doi.org/10.1063/1.1771279 (3 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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A Gow‐Mac thermal conductivity unit has been utilized in the construction of a continuous flow analyzer for ortho‐parahydrogen mixtures. No pump or vacuum system is required. The unit possesses adequate sensitivity for operation at room temperature, thus eliminating the need for low temperature baths. Parameters which influence reproducibility have been investigated and simple techniques for their control are suggested.

Measurement of Electronic Susceptibilities by Means of Nuclear Resonance Absorption

G. Feher and W. D. Knight

Rev. Sci. Instrum. 26, 293 (1955); http://dx.doi.org/10.1063/1.1771280 (2 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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The proton nuclear magnetic resonance is observed in two crossed capillary tubes embedded in a paramagnetic material in a constant external field. The resonance frequencies from the two capillaries depend on the respective demagnetizing factors. For Mn2O3 the two resonance lines are separated by 13.0 kc at 22.3 Mc, giving a mass susceptibility of 65×10−6 cgs, in agreement with values obtained by other methods. For a magnetic field homogeneity of about one part in 107 over the sample, the ultimate sensitivity of the method would be 10−7 to 10−8 susceptibility unit. Measurements can be made at low temperatures.

Resolution of Alpha‐Particle Spectra by Ionization Pulse Analysis of Collimated Samples

D. W. Engelkemeir and L. B. Magnusson

Rev. Sci. Instrum. 26, 295 (1955); http://dx.doi.org/10.1063/1.1771281 (8 pages) | Cited 9 times

Online Publication Date: 29 December 2004

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A high‐resolution ion pulse analyzer has been developed for the study of alpha‐decay fine structure. Alpha‐particle spectra are distorted in conventional high geometry measurements by addition of ionization from excited‐state radiations of the daughter atom. Covering the sample foil with electroformed nickel mesh of a few mils thickness proved to be an effective technique for collimating the alpha particles and absorbing coincident excited‐state radiations. The resolution of the instrument was tested with samples of Bi212, Th230, and Pu238. The measured intensities and particle energies are in satisfactory agreement with magnetic deflection data. Alpha peak standard deviations of 12–13 kev were obtained at a detection efficiency of 0.04 count per disintegration. The standard deviation due to amplifier noise alone amounted to 10 kev.
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Cage Zone Refining

P. H. Brace, A. W. Cochardt, and G. Comenetz

Rev. Sci. Instrum. 26, 303 (1955); http://dx.doi.org/10.1063/1.1771282 (1 page) | Cited 2 times

Online Publication Date: 29 December 2004

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Erratum: Glass Ball Valve

C. W. McCutchen

Rev. Sci. Instrum. 26, 303 (1955); http://dx.doi.org/10.1063/1.1771283 (1 page)

Online Publication Date: 29 December 2004

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Erratum: The Theory of the Fixed Frequency Cyclotron

Bernard L. Cohen

Rev. Sci. Instrum. 26, 303 (1955); http://dx.doi.org/10.1063/1.1771284 (1 page)

Online Publication Date: 29 December 2004

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High‐Vacuum Jet System for Condensation Pumps

J. S. George

Rev. Sci. Instrum. 26, 303 (1955); http://dx.doi.org/10.1063/1.1771285 (2 pages)

Online Publication Date: 29 December 2004

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Abstract Unavailable

X‐Ray Beam Measurement of Distortion in a Magnet Cloud Chamber

Robert Mowbray Walker

Rev. Sci. Instrum. 26, 304 (1955); http://dx.doi.org/10.1063/1.1771286 (2 pages)

Online Publication Date: 29 December 2004

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Liquid Nitrogen Cold Traps

C. R. Meissner

Rev. Sci. Instrum. 26, 305 (1955); http://dx.doi.org/10.1063/1.1771287 (1 page) | Cited 14 times

Online Publication Date: 29 December 2004

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Nickel Diffusion Leak for Hydrogen

E. R. Harrison and L. C. W. Hobbis

Rev. Sci. Instrum. 26, 305 (1955); http://dx.doi.org/10.1063/1.1771288 (2 pages) | Cited 7 times

Online Publication Date: 29 December 2004

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