The tTO(n,a)14C reaction was studied in order to clarify discrepancies in the data on the reaction cross-section for the range of 50 keV to 1000 keV and perform a-particles angular distributions corresponding to different resonances measurements. The experiment was carried out using a gridded ionization chamber. The target was niobium oxide enriched in 170.
1. Introduction
Recently, the so-called nonstandard models of the big bang exited great interest. These models consider the nucleosynthesis of heavy elements via a series of neutron captures through nitrogen and oxygen. However the (n,a) reaction on ~70 is a way back to ~4C and affects the rate of nucleosynthesis. So one needs to know the cross-section of this reaction to reduce the uncertainty of the big bang calculations.
There are discrepancies in the cross-section data from direct experiment of different authors as well as the data derived from the inverse reaction. At the same time no data on the angular distribution of a-particles from this reaction, which would give information on the parameters of resonances and the structure of ~80 and allow us to get more correct cross-section data in comparison with non-2~ measurements exist.
So the present work is aimed at solving the above problems, namely: to measure the 170(n,a)~4C reaction cross-section over the range from 50 keV to 1 MeV and the angular distributions of a-particles in the resonances.
2. EXPERIMENTAL SETUP
The reported experiment was performed on the KG-2.5 accelerator of the Institute of Physics and Power Engineering, Obninsk. The ~70 target was specially made in the Ohio University. This was niobium oxide layer with thickness of 109 lag/cm 2 and 26 mm in diameter. The 170(n,a)14C reaction cross-section was measured relative to the 23sU(n,f) cross-section (ENDF/B-V). The uranium target was the uranium tetrafluoride with a thickness of 50 lag/cm 2 and 50 mm in diameter. It was installed in back-to-back