Abstract
As a part of a general program to evaluate production routes for Th229, we studied production of Th229 via proton-induced reactions on Th232 targets bombarded with low-energy protons, Ep≤40MeV. The reported excitation functions include those for proton-induced reactions on natural thorium yielding to Pa228,229,230&232 isotopes; Th232(p,xn) reactions, where x=1, 3, 4, and 5, at proton energy ranges of 12-40 MeV. Although the data for Th232(p,n)Pa228, Th232(p,3n)Pa230, and Th232(p,5n)Pa232 reactions were deduced by direct analysis of the thorium foils after irradiation, the data for Th232(p,4n)Pa229 were obtained by radiochemical techniques. The half-life of Pa229 was evaluated and determined to be 1.55 ± 0.01 d. Further, the α-branching ratio, α/(α + EC) of Pa229 was evaluated to be 0.53 ± 0.10% by allowing Pa229 to decay for ∼7d, then chemically extracting and quantifying the Ac225 (t1/2=10.0±0.1d) from Pa229 samples. In addition, we report the effective production cross section of Th229 in a thick Th232 target in the proton energy range of 23-33 MeV. The peak of the excitation function for the Th232(p,4n)Pa229 reaction occurs at 162 ± 14 mb and Ep=29.7±0.5MeV. This is only slightly larger than the effective cross section for the Th232(p,x)Th229 reaction (obtained from a thick target experiment). This data indicates that the Th232(p,4n)Pa229 reaction is the major reaction pathway for the cumulative Th232(p,x)Th229 reaction cross section in this energy range. The measured cross sections were compared with theoretical cross sections using the simulation codes Particle and Heavy Ion Transport code System (PHITS) and Monte Carlo Neutral Particle 6 (MCNP6). At proton energy ranges of 12-33 MeV, the cumulative excitation function predicted by PHITS for the reactions leading to Th229 was in close agreement with the experimental function, whereas the function predicted by MCNP6 was a factor of two higher at the peak of the excitation function.
| Original language | English |
|---|---|
| Article number | 044607 |
| Journal | Physical Review C |
| Volume | 98 |
| Issue number | 4 |
| DOIs | |
| State | Published - Oct 12 2018 |
Funding
This research was supported by the Department of Energy Isotope Program, managed by the Office of Nuclear Physics in the Office of Science. The authors acknowledge the efforts of the Holifield Radioactive Ion Beam Facility staff in delivering the high-quality proton beams that made this study possible. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).
| Funders | Funder number |
|---|---|
| Office of Nuclear Physics | |
| US Department of Energy | |
| U.S. Department of Energy | |
| Office of Science |