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Apr 1940

Volume 11, Issue 4, pp. 111-134

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Concave Spherical Crystals of Barium‐Copper‐Stearate for Use in Long Wave‐Length X‐Ray Spectrometers

C. Luther Andrews

Rev. Sci. Instrum. 11, 111 (1940); http://dx.doi.org/10.1063/1.1751662 (4 pages) | Cited 2 times

Online Publication Date: 27 December 2004

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To perform the double function of diffracting and focusing a monochromatic beam of x‐rays, multiple monomolecular layers of barium‐copper‐stearate were deposited upon an accurately ground concave spherical surface of glass. With a spherical crystal of radius of 218 cm, grating space of about 50.5A, preliminary photographs of the Al Kα,β region, component lines not resolved, were obtained in 30 minutes at 3 kv and 15 ma. It is believed that the intensity and resolving power from such a spherical grating are adequate for measurements with an ionization chamber of absorption coefficients at wave‐lengths above 8A.

A New Method for Measuring Young's Modulus

Allen King

Rev. Sci. Instrum. 11, 114 (1940); http://dx.doi.org/10.1063/1.1751663 (3 pages) | Cited 2 times

Online Publication Date: 27 December 2004

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The specimen, in the form of a circular loop of wire, is fastened at one point to a rigid support. At the diametrically opposite point a magnetic field is applied. The frequency of an alternating current in the loop is adjusted until flexural vibrations occur in the plane of the loop. Then the resonance frequency f, the radius of the loop r, the linear density m, and the radius of the wire a are related to Young's modulus by the equation E=18.395 mf2(r/a)4(1−g) in which (1−g) is a gap correction factor.

A Design for an Electromagnet and Performance of a Small Model

Simon Freed

Rev. Sci. Instrum. 11, 117 (1940); http://dx.doi.org/10.1063/1.1751664 (3 pages)

Online Publication Date: 27 December 2004

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The windings of the magnet are made of continuous lengths of copper tubing with cross section shown in Fig. 1. Water at high pressure is sent through the hollow center for cooling. The conductor is wound about the core in such a way that the resistance to the flow of the water is reduced to about half what would prevail in a magnet of conventional design. These features make possible a high effective current density. The disposition of the coils and the shape of the iron core were based on the experiences with the big magnets in Upsala and in Paris. A model gave the results indicated in Fig. 5. When the pole faces 2.5 cm in diameter were separated by 7 mm the field obtained was 33,200 gauss using 16 kw. The model was constructed to employ water at considerably higher pressures than were actually tried. A higher current density would then be permitted without risk of serious electrolytic corrosion.

A Sensitive Automatic Pressure Control Device

Richard A. Smith

Rev. Sci. Instrum. 11, 120 (1940); http://dx.doi.org/10.1063/1.1751665 (3 pages)

Online Publication Date: 27 December 2004

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A Method and Instrument for the Measurement of Very Small Amounts of Heat and Very Small Changes of Temperature

S. Zamenhof

Rev. Sci. Instrum. 11, 123 (1940); http://dx.doi.org/10.1063/1.1751666 (3 pages)

Online Publication Date: 27 December 2004

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A thermometer is described which detects temperature changes of the order of 10−4 °C and quantities of heat of the order of 10−4g cal. It is essentially a gas or vapor thermometer in which the shift of the top of the meniscus of an indicating liquid is observed through a microscope. The shift is due to changes of the shape of the meniscus while the circumference remains stationary. Hence the sensitivity depends upon the surface tension of the indicating liquid but not on the friction between the liquid and the glass.

An Apparatus for the Determination of the Electric Moment of Molecules

Marcus E. Hobbs, J. W. Jacokes, and Paul M. Gross

Rev. Sci. Instrum. 11, 126 (1940); http://dx.doi.org/10.1063/1.1751667 (8 pages) | Cited 2 times

Online Publication Date: 27 December 2004

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More About Vacuum Leak Testing

E. J. Lawton

Rev. Sci. Instrum. 11, 134 (1940); http://dx.doi.org/10.1063/1.1751668 (1 page) | Cited 6 times

Online Publication Date: 27 December 2004

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Closing the Compression Capillary of a McLeod Gauge

W. F. C. Ferguson

Rev. Sci. Instrum. 11, 134 (1940); http://dx.doi.org/10.1063/1.1751669 (1 page)

Online Publication Date: 27 December 2004

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