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Concerning the scattering of fast electrons and of cosmic-ray particles

1939; Royal Society; Volume: 169; Issue: 939 Linguagem: Inglês

10.1098/rspa.1939.0015

2053-9169

E. J. Williams,

Radiation Therapy and Dosimetry

When a particle, as the result of passing through a thickness of matter, is “scattered” through an angle, a, the scattering may be the result of the accumulated effect of a number of small deflexions produced by different atomic nuclei in the matter traversed, or it may be due to a single deflexion through an angle a produced by some one nucleus. The first type of scattering is spoken of as “multiple” or “plural”, according as the number of contributing collisions is large or small. The second type is referred to as “single” scattering. Which process is mainly operative depends on the nature and velocity of the scattered particle, the matter traversed, and the scattering angle. Under the conditions of single scattering the experimental results may be readily compared with the theory of the scattering by a single nucleus or atom, and they have in that way a direct fundamental significance. The theory of multiple and plural scattering, in addition to the deduction of the single scattering formula, involves a statistical problem. An accurate treatment of the latter is in general not possible, and to the extent that this is so the corresponding experimental results are lacking in fundamental interest.