Neutron Yields from Photo-Disintegration by Gamma-Rays from Lithium

Abstract

STEARNSThe relative neutron yield of 33 elements has been studied using the gamma-ray spectrum which arises from proton bombardment of Li. The samples which were to be irradiated were placed in a block of paraffin. The neutrons were detected using four boron trifluoride proportional counters. Absolute gamma-ray and neutron intensity measurements yielded the value (0.055±0.012) barn for the (y,n) cross section of copper. Rough indications were also obtained concerning the relative neutron energy distribution from the samples.

The absolute photo-neutron yield from copper for the lithium gamma-rays

“…This result is considerably higher than that obtained by McDaniel, Walker and Stearns (1950) being in better agreement with the deternfination made by the Saskatoon group.…”

“…In view of the large discrepancy between the photo-neutron yield measurement of McDaniel, Walker and Stearns (1950) and the various activation measurements (excepting that of Gl~ttli, Seippel and Stoll 1952), it was decided to repeat the neutron yield measurement using different techniques for the neutron and gamma-ray intensity determinations.…”

“…McDaniel, Walker and Stearns (1950) used a ' long ' BF a neutron counter to measure the absolute photo-neutron yield from copper under the action of the 14.8 and 17.6 ~ev gamma-rays from the VLi (p, ;~) reaction ; they quote a cross section of (55±12)× 10 27 em 2, the calibration being made by means of a standard Ra-Be neutron source. Other absolute measurements of the cross section for the lithium gamma-Iays have been obtained by activation techniques.…”

Зависимость Поперечного Сечения Фотозахвата От Заряда Ядра

“…Ниже излагается содержа-ние двух работ 1 · 2 , посвященных это-му вопросу. Авторы первой работы, используя экспериментальные дан-ные по (7п)-реакциям, вызванным γ-лучами Li (ργ) 3 , рассчитывают σ (γ) для 1) лёгких ядер с Ζ между 8 и 20; 2) ядер среднего веса Си и Ni и 3) одноизотопных тяжёлых ядер J, Та, Bi и U. Для расчёта необхо-димо знание энергии связи вылета-ющих частиц, плотности уровней воз-буждённых ядер и поперечного се-чения проникновения сквозь потен-циальный барьер. При рассматривае-мом возбуждении возможен вылет одной или двух частиц (протона или нейтрона) в различной последова-тельности.…”

Giant dipole resonance and evolution of concepts of nuclear dynamics

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