Preparation of highly enriched 17O samples for neutron-induced reaction studies

Suitable 17O samples are required for the study of the 17O(n,α)14C reaction with various detectors. The electrospraying of metal oxides enriched in 17O onto an Al substrate yielded negative results: no 17O(nth,α) reactions were observed when irradiating these samples with thermal neutrons. These tests demonstrated the need to minimize the 10B content in sample and backing, since the 10B(nth,α1) reaction causes a strongly disturbing background. Good results were obtained in the reactor experiments using gaseous samples (17O enrichments of 58.2%, 72.1% and 85.5%) with a dedicated experimental setup. The experimental conditions being quite different at accelerators, an alternative method was developed to prepare samples suited for use in ionization chambers. For this purpose, 17O ions were implanted in ultra-pure Al foils. The thickest sample prepared in this way contains 8×1018 atoms of 17O, with a 10B/17O ratio of 10−4.