Nuclear reactions with oriented target nuclei and polarized beams

Abstract

The principal methods of orienting nuclei are reviewed, and a list is given of the nuclei for which a method of orientation has been established, except for those nuclei which have so far been oriented only in infinitesimal concentrations. The factors which affect the degree of orientation which can be attained in practice are discussed, and numerical values of typical cases are given. The methods which are available for producing beams of polarized protons, neutrons and γ-rays are reviewed, and values are given for the fluxes which can be achieved. The problem of the production and dissipation of heat in the target of oriented nuclei is treated at some length, with numerical examples for a typical target and typical beams of thermal neutrons, resonance neutrons, 3 MeV neutrons and 17·6 MeV γ-rays. Values are obtained for the magnitude of the heating effect in each case, and for the number of nuclear reactions which occur in the target for unit heat production.Experiments using oriented target nuclei and polarized or unpolarized beams are suggested and discussed. The following reactions are treated at some length: the change in cross section with orientation for incident neutrons and γ-rays, the angular distribution of γ-rays following slow neutron capture, and the angular distribution of γ-rays following inelastic scattering of 3 MeV neutrons. The method of interpreting the results is indicated, and the value of the results of these experiments is discussed in relation to the present state of knowledge of nuclear structure, and in relation to current problems of theoretical nuclear physics.Tables are given of various reaction cross sections which are likely to be needed for designing experiments of the type discussed.