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Some Experiments on the Slowing Down of Neutrons by Collisions with Hydrogen Nuclei

Published online by Cambridge University Press:  24 October 2008

C. H. Westcott  and
T. Bjerge
C. H. Westcott
Affiliation:
Queens' College
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Extract

The discovery of Fermi and his collaborators, that neutrons are much more readily captured by various atoms, e.g. silver, when their kinetic energies, originally of the order of 106 e.v., have been reduced by collisions with hydrogen nuclei, has been confirmed.

The process of slowing down of the neutrons has been studied in some detail, and the nuclear cross-section for collisions with hydrogen nuclei has been determined for the primary neutrons and for the slow neutrons which are readily captured by silver atoms.

The nature of the “gas” of slow neutrons was also discussed, but it was not found possible to reach a definite conclusion as to the energy of the neutrons concerned.

Type
Research Article
Information
Mathematical Proceedings of the Cambridge Philosophical Society , Volume 31 , Issue 1 , January 1935 , pp. 145 - 152
Copyright
Copyright © Cambridge Philosophical Society 1935

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References

* La Ricerca Scientifica, (5), 2 (1934), 282, 380 and 467.Google Scholar

† For information on the whole subject, see Fermi, Amaldi, d'Agostino, Rasetti, and Segrè, , Proc. Roy. Soc. A, 146 (1934), 483.CrossRefGoogle Scholar

‡ It was proved that it is not due to γ-rays from the neutron source, and that surrounding with substances not containing hydrogen gave very little increase.

§ The periods of the activities induced in silver are 22 sec. and 150 sec. We find that under the above conditions the longer period is contributing about 10% to the result.

* But compare § VII below.

* Compare the results of Dunning (Phys. Rev. 45 (1934), 586)Google Scholar, who measured the attenuation due to both slowing down and scattering without loss of energy.

† Note added in proof. Later experiments with paraffin oil instead of water have given a curve almost identical with the one in Fig. 2.

* Fermi, etc., La Ricerca Scientifica, loc. cit.

* If any of the fast neutrons are absorbed instead of being slowed down, this figure will be increased.

† Auger, and Monod-Herzen, , Comptes Rendus, 196 (1933), 1102Google Scholar; Meitner, and Philipp, , Zeits. f. Phys. 87 (1934), 484CrossRefGoogle Scholar. Compare, however, Kurie, , Phys. Rev. 44 (1933), 463CrossRefGoogle Scholar.