Interaction of Neutrons withHe3

Abstract

Spectra of the w+He 3 reactions were obtained for monoenergetic neutron fluxes of 0. 95, 2.67, 5.00, 8.07, and 17.5 Mev using a He 3 -filled proportional counter. Analysis of these spectra yielded the ratios to the total cross section of the total elastic, the He 3 (w,^)H 3 , and the He 3 (w,d)D reaction cross sections. Absolute cross sections were obtained by normalization to the known total cross section. Differential elastic-scattering cross sections for neutrons on He 3 were obtained through the relationship between the scattering angle of the neutron and the observed energy of the He 3 recoil in the counter filling. These angular distributions are compared with the theoretical angular distributions as calculated by Bransden, Robertson, and Swan. The present experiment was intended to discriminate between their assumed two special cases for the potential interaction, the symmetrical exchange force and the Serber exchange force. The experimental results favor the Serber exchange force. This experiment also was intended to make possible the analysis of more complex neutron spectra by providing knowledge of w+He 3 reaction cross sections and the spectra obtained when only monoenergetic neutrons are present. A comparison is made of the results of this experiment with cross sections calculated from inverse reactions and direct measurements of other investigators, where such data are available.

Total cross section of the3H(p,n)3Hereaction from th

“…The 3 He(n, p) 3 H cross section at thermal energies has been determined with high precision by the total cross section of Als-Nielsen and Dietrich [13]. Measurements at higher neutron energies have been reported by Coon [14], Batchelor, Aves, and Skyrme [15], Sayres, Jones, and Wu [16], Costello, Friesenhahn, and Lopez [17], and Borzakov et al [18]. Ratios of the 3 He(n, p) 3 H cross section to the 6 Li(n, α) and 10 B(n, α) cross sections have been measured by Bergman and Shapiro [19] (E n ≤ 30 keV) and Bowman et al [20] (E n ≤ 25 keV), respectively.…”

“…[48,49] mentioned in the previous paragraph and also from Refs. [16,17] which measured the ratio of the 3 He(n, p) 3 H cross section to the n − 3 He total cross section. (3) Some reported measurements have been superseded by or included in subsequent data sets, and should be considered accordingly.…”

Empirical Neutron Cross Section Formulae for (n, p) and (n, d) Reactions of He-3 Target

“…Cross sections for (n, p) reactions of He-3 by thermal neutrons have been determined in [20], while cross sections for (n, p) reactions of He-3 by epithermal neutrons have been measured in [21]. Different monoenergetic neutrons between and He3-filled proportional counter were used to obtain the cross sections of both (n, p) and (n, d) reactions of the target He-3 [22]. Indeed, the cross section of (n, d) reaction of He-3 target with 14.4 MeV incident neutron energy has been measured using a counter telescope [23].…”

Fast-neutron spectrometry using a 3He ionization chamber and digital pulse shape analysis

“…[33] In some cases neutron spectrometry may be used to 13 identify the alpha-emitting radioisotope; for example, different actinides emit different energy alpha particles and in 14 beryllium there is a neutron spectrum dependence on the energy of the incident alpha particles. [34] Neutron 15 spectrometry may also be capable of providing forensic-level evidence concerning the mean particle size of the 16 subcomponents in 9 Be(D,n) type neutron sources. [35,36] For safeguards applications fast-neutron spectrometry has 17 the potential to be used as a tool for discriminating between metallic and oxide forms of plutonium, as either a direct 18 method or a supporting method in conjunction with gamma-ray spectrometry.…”