NEUTRONS AND GAMMA RAYS FROM Po210–B10(α,n) AND Po210–B11(α,n) SOURCES

Abstract

The neutron energy spectra from Po–B¹⁰(α,n) and Po–B¹¹(α,n) sources have been determined by the nuclear emulsion method and with a proton recoil spectrometer. Gamma spectra have also been measured. The Po–B¹⁰ neutron spectrum extends to an energy of 6.0 Mev and shows two peaks, at 1.0 and 3.0 Mev. The lines in the gamma spectrum are not in coincidence with neutrons but are caused by competing reactions. The Po–B¹¹ neutron spectrum shows one peak at 2.7 Mev; the maximum energy observed is 5.0 Mev. One γ-ray line at 2.32 Mev with an intensity of 5% of the neutron emission rate is detected in the gamma–neutron coincidence measurements. The experimental neutron energy spectra have been compared with calculated spectra and are compatible with the gamma measurements, as well as with published level schemes for the residual N¹³ and N¹⁴ nuclei. In the case of the Po–B¹⁰ source only one-third of the neutrons are produced by the B¹⁰(α,n)N¹³ reaction and the remainder has to be accounted for by the B¹⁰(α,np)C¹² reaction.