Neutron capture measurements at a RIA-type facility

Abstract

Neutron capture cross sections of unstable isotopes are important for neutron induced nucleosynthesis as well as for technological applications. The Rare Isotope Accelerator (RIA) or comparable facilities will be able to produce radioactive ion beams up to 10 12 particles/s and would therefore be a suitable place for (n,γ) studies on radioactive isotopes with half-lives between days and months. We propose a facility for measurements of (n,γ) cross sections of unstable isotopes in the keV range suited for minimal sample masses down to 10 15 atoms, corresponding to minimum half-lives of only 10 d.

Neutron capture cross section of85Kr

“…The high neutron flux at the sample position will be increased by reducing the neutron flightpath to about 8 cm [11].…”

Opportunities for Nuclear Astrophysics at FRANZ

“…For this particular setup, the gain in neutron flux resulting from the short flight path was partly compensated by the significant loss in γ-ray detection efficiency compared to the BaF 2 array. In principle both ideas -ultra-short flight path and 4π BaF 2 array -could be combined, but then the challenge is the enormous γ-flash immediately after the interaction of the proton pulse with the lithium target (Reifarth et al 2004;Walter et al 2006). Figure 6 shows an example of the time distribution of a possible realization.…”

Realizing the Opportunities of Neutron Cross-Section Measurements at RIA

“…By far the most developed concept for prompt measurements is for the (n,γ) reactions [5]. The technique would use an array of BaF 2 detectors, such as the DANCE detector, to do total gamma-ray calorimetry to detect the neutron captures.…”