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Apr 1952

Volume 23, Issue 4, pp. 149-198


An Airborne Microwave Refractometer

C. M. Crain and A. P. Deam

Rev. Sci. Instrum. 23, 149 (1952); http://dx.doi.org/10.1063/1.1746211 (3 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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A device for measuring directly tropospheric index of refraction fluctuations and profiles is described. The change in resonant frequency of a cavity resonator exposed to atmospheric air is recorded continuously —thus giving a continuous recording of atmospheric index of refraction relative to an arbitrary reference. The method used for sampling the air and the measured errors involved are described. A typical segment of recorded data is shown.

Determination of Air Velocity by Ion Transit‐Time Measurements

William C. Cooley and H. Guyford Stever

Rev. Sci. Instrum. 23, 151 (1952); http://dx.doi.org/10.1063/1.1746212 (4 pages) | Cited 10 times

Online Publication Date: 29 December 2004

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A method is described for measuring the velocity of an air stream by producing positive ions at one point in the flow and measuring the time required for the ions to be carried to an induction‐type detector located a known distance (0.5 to 2.0 inches) downstream. Positive ions are produced intermittently near the tip of a positive corona point by burst discharges which are initiated by stray ions in the air stream or by irradiating the air in the neighborhood of the positive corona point with polonium alpha‐particles. The ion transit‐time is measured by observing the induced pulses from the detector on a cathode‐ray oscillograph sweep which is triggered by the burst discharges of the corona point. The accuracy of velocity measurement using a measuring length of one inch with a free‐stream air velocity of 1730 feet per second (based on pressure and temperature measurements) was better than two percent. It is shown that the direction of streamlines in a supersonic flow can be determined approximately by aligning the corona point and the induction detector probe to give the maximum amplitude of induced pulses. It is believed that this method may be applied to map velocity fields in supersonic wind tunnel experiments.

Measurement of Neutron Flux with Lithium Borate Loaded Emulsions

Nathan Kaplan and Herman Yagoda

Rev. Sci. Instrum. 23, 155 (1952); http://dx.doi.org/10.1063/1.1746213 (7 pages) | Cited 5 times

Online Publication Date: 29 December 2004

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Methods for the incorporation of lithium borate in nonelectron sensitive nuclear emulsions have been investigated from the viewpoint of emulsion stability and high B10 and Li6 pick‐up for use in the estimation of low neutron flux. Ilford C‐2 plates loaded by absorption from 10 percent lithium borate solution buffered with lithium carbonate and containing 3 percent by volume of glycerine or diethylene glycol pick‐up an equilibrium concentration of 34 mg per cc of boron and 12 mg per cc of lithium ions, respectively. Isothermal absorption curves indicate that the borate and lithium ions migrate into the gelatin—AgBr mixture at different rates. Higher concentrations of B‐ and Li‐ nuclei in the emulsion can be introduced by the method of evaporation loading.
Methods for evaluating the boron and lithium concentration in the emulsion are described. Quantitative recording of tracks from the B10(n,α)Li7 and the Li6(n,α)H3 reactions can be maintained for periods of about 3 months; which provides a convenient means of estimating low slow‐neutron flux for purposes of health monitoring, or investigations of spontaneous fission processes, and for the evaluation of the cosmic radiation neutron background. The flux at sea level arising from cosmic radiation is of the order of 230 slow neutrons per cm2 per day, (ranging from 160 to 300 with change of exposure conditions). At an elevation of 3500 m, the flux shows a 10‐fold increase.

Initial Adjustment of the Mach‐Zehnder Interferometer

E. W. Price

Rev. Sci. Instrum. 23, 162 (1952); http://dx.doi.org/10.1063/1.1746214 (1 page) | Cited 8 times

Online Publication Date: 29 December 2004

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A relatively simple method is described for adjustment of a Mach‐Zehnder interferometer for parallel image planes and for white light fringes. Auxiliary apparatus required consists of one plane mirror and one pinhole, which may be incorporated as permanent parts of the interferometer.

A New Method of Converting Platinum Resistance Values to Degrees Centigrade

Frank D. Werner and Alson C. Frazer

Rev. Sci. Instrum. 23, 163 (1952); http://dx.doi.org/10.1063/1.1746215 (7 pages) | Cited 4 times

Online Publication Date: 29 December 2004

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Values of temperature in degrees C are conveniently derived from values of resistance of a platinum resistance thermometer by means of a table of temperature vs resistance. Since each thermometer has its own fundamental constants, it becomes laborious to prepare separate tables for different thermometers. This labor may be avoided by the method outlined. The method is to interpolate from a single ``standard'' table, applying corrections which have been worked out in a reasonably compact form to use the constants of each particular thermometer. A standard table and its correction table are given and were calculated by a rapid method which is outlined. A graph is the most convenient form for the corrections to this standard table. The procedure for making these corrections is discussed. In addition a graphical means of conversion is discussed, which is accurate to 0.01°C and is very convenient and rapid where this accuracy is adequate.

Some Properties of Plastics and the Use of Plastic Apparatus at Low Temperatures

W. F. Giauque, T. H. Geballe, D. N. Lyon, and J. J. Fritz

Rev. Sci. Instrum. 23, 169 (1952); http://dx.doi.org/10.1063/1.1746216 (5 pages) | Cited 6 times

Online Publication Date: 29 December 2004

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Some properties of methyl methacrylate plastic have been investigated at low temperatures to supply design data needed for the construction of plastic apparatus. The diffusion rates for air and helium have been measured at temperatures from 260 to 300°K. The diffusion coefficient k (expressed as cm3 (N.T.P.) sec−1(cm Hg−1)) is given roughly by the following relation:
math
and
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The change in length of a 30‐cm rod has been measured at 298.7°, 273.16°, 194.7°, 77.3°, and 20.4°K by comparison with quartz using a depth micrometer gage. The coefficient of expansion is tabulated as a function of temperature, increasing from 0.6×10−5 at 20°K to 8.0×10−5 at 300°K. Hysteresis and geometrical distortion accompanying cooling are shown to be very small. Complex apparatus containing many seals, including various sorts of electrical leads, has been shown to be vacuum tight when tested in liquid helium II. A method of connecting a vacuum line at room temperature and a plastic apparatus at low temperatures by means of a metal tube liner‐diluted rubber cement seal is described. The adsorption of helium gas has been measured at 4.2 and 1.2°K and at pressures from 4×10−4 to 4×10−1 mm.

Application of the W.B.K. Method to the Dynamics of Linear Accelerator

Max Hoyaux

Rev. Sci. Instrum. 23, 173 (1952); http://dx.doi.org/10.1063/1.1746217 (3 pages)

Online Publication Date: 29 December 2004

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The dynamics of ``small motions'' in a linear accelerator is studied in as general conditions as possible. It is concluded that heavy particles cannot be accelerated up to the Bev range by any practical combination of Tm and/or Te traveling and/or stationary waves. Several methods are however possible for electrons.
In the case of heavy particles, charges or currents must be introduced inside the beam. Two methods seem promising, (a) the Berkeley device (foils or grids) in which the beam expands as the power (1/8) of energy, and (b) a coaxial structure with dc bias (≃100 kv) in which the beam radius remains approximately constant.
The focusing by means of a dc current parallel to that of the beam is not practical.

Molecular Weight Determinations by Effusiometry

Paul D. Zemany

Rev. Sci. Instrum. 23, 176 (1952); http://dx.doi.org/10.1063/1.1746218 (2 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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An effusiometer using a thermistor as a pressure gauge is described. Molecular weights can be determined with it with an average error of ±2 percent. Only a few hundredths of a cubic centimeter of gas at N.T.P. is required as a sample, and may be recovered.
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An Instrument for the Measurement of Cardiac Output

S. R. Powers, H. H. Rossi, and E. M. Papper

Rev. Sci. Instrum. 23, 178 (1952); http://dx.doi.org/10.1063/1.1746219 (4 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A modification of the injection technique for the determination of cardiac output is presented in which the injected material is a radioactive isotope (Na24). The measurement is performed with a recording unit which consists of a counting chamber, a counter with conventional amplifier, a count rate circuit with a short RC constant (1 second), and a recording milliammeter. The instrumentation is described and a simple method is given whereby the cardiac output may be determined from the trace of the recorder.
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Erratum : An Induction Flowmeter Design Suitable for Radioactive Liquids

W. G. James

Rev. Sci. Instrum. 23, 181 (1952); http://dx.doi.org/10.1063/1.1746220 (1 page)

Online Publication Date: 29 December 2004

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Backstreaming in Oil Diffusion Pumps

L. G. Parratt and E. L. Jossem

Rev. Sci. Instrum. 23, 188 (1952); http://dx.doi.org/10.1063/1.1746221 (2 pages) | Cited 2 times

Online Publication Date: 29 December 2004

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A Calibrated Stage for the R.C.A. Electron‐Microscope

Joseph L. Leon

Rev. Sci. Instrum. 23, 189 (1952); http://dx.doi.org/10.1063/1.1746222 (2 pages) | Cited 1 time

Online Publication Date: 29 December 2004

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A New Gravitometer

E. F. Linhorst

Rev. Sci. Instrum. 23, 190 (1952); http://dx.doi.org/10.1063/1.1746223 (1 page)

Online Publication Date: 29 December 2004

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New Instruments

W. A. Wildhack

Rev. Sci. Instrum. 23, 191 (1952); http://dx.doi.org/10.1063/1.1746224 (7 pages)

Online Publication Date: 29 December 2004

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New Materials

Forest K. Harris

Rev. Sci. Instrum. 23, 197 (1952); http://dx.doi.org/10.1063/1.1746225 (2 pages)

Online Publication Date: 29 December 2004

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