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Some calculations on the diffusion of slow neutrons in hydrogenous media

Published online by Cambridge University Press:  24 October 2008

C. H. Westcott
C. H. Westcott
Affiliation:
Queens' College
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Extract

The paper describes calculations on the distribution in space of slow neutrons based on the application of diffusion laws to their motions. The effects of using spheres of different sizes, and of changing the composition of the hydrogenous slowing-down medium, are discussed. Curves are given which can be compared with the results of the experiments on the slowing down in different media carried out by the author in collaboration with Mr T. Bjerge, and a revision of the calculations based on these experiments leads to a value of 6 × 10−25 cm.2 for the total absorption cross-section of the water molecule, and indicates that most of this absorption must be attributed to the hydrogen atoms.

The author desires to acknowledge the receipt of a Senior Research Award from the Department of Scientific and Industrial Research.

Type
Research Article
Information
Mathematical Proceedings of the Cambridge Philosophical Society , Volume 33 , Issue 1 , March 1937 , pp. 122 - 136
Copyright
Copyright © Cambridge Philosophical Society 1937

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References

* Bjerge, and Westcott, , Proc. Roy. Soc. A, 150 (1935), 709,CrossRefGoogle Scholar hereinafter cited as B-W.

† Usually, for convenience, cylinders were used instead of spheres: the effect of this change can be seen from B-W, Fig. 14. In some preliminary experiments (Westcott, and Bjerge, , Proc. Camb. Phil. Soc. 31 (1935), 145,CrossRefGoogle Scholar hereinafter cited as W-B) the number of slow neutrons at different distances from the source in a large vessel of water was also measured.

‡ Cf. Moon, , Proc. Phys. Soc. 48 (1936), 648;CrossRefGoogle ScholarFermi, , Ric. Sci. 7 (ii) (1936), 13;Google ScholarBethe, , Phys. Rev. 47 (1935), 747;CrossRefGoogle ScholarPerrin, and Elsasser, , J. Phys. 6 (1935), 194;Google ScholarBreit, and Wigner, , Phys. Rev. 49 (1936), 519.CrossRefGoogle Scholar

* Amaldi, , d'Agostino, , Fermi, , Pontecorvo, , and Segrè, , Ric. Sci. 6 (i) (1935), 581;Google ScholarMoon, and Tillman, , Proc. Roy. Soc. A, 153 (1936), 476;CrossRefGoogle ScholarWestcott, and Niewodniczański, , Proc. Camb. Phil. Soc. 31 (1935), 617;CrossRefGoogle ScholarDunning, , Pegram, , Fink, , and Mitchell, , Phys. Rev. 48 (1935), 265 and 704, and 49 (1936), 103;CrossRefGoogle ScholarAmaldi, and Fermi, , Ric. Sci. 7 (i) (1936), 454;Google ScholarPhys. Rev. 50 (1936), 899.Google Scholar

† Loc. cit.; also Ric. Sci. 6 (ii) (1935), 344 and 443.Google Scholar

‡ See, for example, Jeans, , Dynamical theory of gases, 3rd ed. (Cambridge, 1921), 310.Google Scholar To allow for a persistence of velocity p (say), λ′ = λ (1 + p + p 2 + …) = λ/(1 − p) has been written for λ; λ′ is the quantity directly obtained from Fig. 7 of B-W.

* Loc. cit.; cf. also the treatment of Fermi, , Ric. Sci. 7 (ii) (1936), 13.Google Scholar

† Chadwick, , Proc. Roy. Soc. A, 142 (1933), 1;CrossRefGoogle Scholar Fermi, loc. cit.; cf. Goldhaber, , Nature, 137 (1936), 824;CrossRefGoogle ScholarTuve, and Hafstad, , Phys. Rev. 50 (1936), 490.CrossRefGoogle Scholar

* Figs. 5A and 5B of B-W. See also following paper for measurements of effect due to group C neutrons alone.

* See the following paper.

* Proc. Camb. Phil. Soc. 31 (1935), 617.Google Scholar

* Arsenjewa-Heil, Heil, and Westcott, unpublished.