Cross section measurements for neutron-induced reactions off C, Al, SiO_2, Si and Au producing relatively short-lived radionuclides at neutron energies between 70 and 160 MeV

摘要

A systematic study was made to measure many cross sections for relevant neutron-induced reactions. This study was motivated by the need to better understand cosmic ray interactions with extraterrestrial materials. The major constituents of meteorites and lunar rocks include oxygen, silicon, and aluminum. The primary aim was to measure cross sections for neutron-induced reactions producing long-lived radionuclides (e.g. ~(14)C) and stable isotopes (e.g. Ne isotopes) but the irradiation conditions allowed cross sections for many reactions producing relatively short-lived radionuclides (e.g. ~(22)Na) to be well measured. Monitor foils used in the irradiations included C, Al, and Au. Quasi-monoenergetic neutron beams were produced by bombarding Be targets with 80, 120 and 160 MeV proton beams at iThe-mba LABS, South Africa. Two identical target stacks were irradiated in beam lines at 0° and 16° to the incident proton beam direction. The yield at an unique neutron energy was obtained by subtracting the yield measured at 16° (after suitable normalization) from that measured at 0°. The cross sections for the following reactions: ~(27)Al(n,x)~(22,24)Na; ~(nat)C(n,x)~7Be; ~(197)Au(n,x)~(194,196)Au; SiO_2(n,x)~(22)Na and ~(nat-) Si(n,x)~(24)Na are reported.