摘要:

A method is described for examining the soap component of lubricating greases with the electron microscope. The soap component is mounted on Formvar films from a dispersion in ether. The specimen is shadow cast by the method of Williams and Wyckoff. The deduction of the shape of the soap particles is discussed.

ISSN:1923-4287    

DOI:10.1139/cjr47a-013

出版商:NRC Research Press    

年代:1947

数据来源: NRC

摘要:

Two types of magnetometers using high permeability materials are described—first, those using a field leaving the material in an unsaturated condition and giving a second harmonic output, and, second, those using the saturated core method, resulting in a peak signal output. The application of the saturated core type magnetometer to the particular problem of an automatic steering control is described in detail.

ISSN:1923-4287    

DOI:10.1139/cjr47a-014

出版商:NRC Research Press    

年代:1947

数据来源: NRC

摘要:

A continuous flux of thermal neutrons was passed into a large cylindrical tank of heavy water that sat on a graphite column containing a source of photoneutrons. The neutron density in the tank was explored with small indium detectors at selected points along two diameters at right angles in each of three horizontal planes and at 10-cm. intervals along the axis of the tank. The transverse measurements were fitted to Fourier–Bessel series in which the amplitudes of the harmonics were relatively small. The effective radius derived from the transverse analysis was the same in the three planes. The relaxation length of the first component was found from the axial measurements. Corrections were applied for the absorption of neutrons in the axial detector tube, enclosed framework, and indium detectors, and in the light hydrogen in the heavy water. The final value of the diffusion length of thermal neutrons in heavy water (100% D2O) is 171 ± 20 cm. Combining this with the known transport mean free path, the capture cross-section is (0.92 ± 0.22) × 10−27 cm.2per molecule D2O for neutrons of velocity 2200 m. per second.

ISSN:1923-4287    

DOI:10.1139/cjr47a-015

出版商:NRC Research Press    

年代:1947

数据来源: NRC

摘要:

The transport mean free path of thermal neutrons in heavy water is determined from measurements of the neutron density in heavy water (99.4 atoms of deuterium per 100 atoms of hydrogen element) at various distances from a cadmium plate. In the region investigated, the density is found to be a linear function of the distance from the cadmium plate. When this straight line is extrapolated, the density vanishes at a distanced = 1.64 cm. behind the plate. On the basis of transport theory it is known thatd = 0.71 lt, whereltis the transport mean free path in the medium. The final result islt = 2.4 cm. in pure heavy water. The measurements of the neutron density show that it falls below the straight line as the cadmium surface is very closely approached, in agreement with transport theory.

ISSN:1923-4287    

DOI:10.1139/cjr47a-016

出版商:NRC Research Press    

年代:1947

数据来源: NRC

摘要:

The spatial distributions of thermal neutrons (as measured by dysprosium detectors) and of resonance neutrons (indium detectors protected by cadmium) have been investigated in several media, consisting of water and heavy elements in a heterogeneous arrangement, with two different neutron sources (Ra-α-Be and Ra-γ-Be). The experimental results are summarized in tables where the values of the mean square distances from the source of neutrons are given, for the various media, detectors, and sources used. It was found that among all the media investigated, a mixture of water and iron is the most efficient shield for neutron generating machines such as piles and cyclotrons.

ISSN:1923-4287    

DOI:10.1139/cjr47a-017

出版商:NRC Research Press    

年代:1947

数据来源: NRC