⁷⁹Se(d,p)⁸⁰Se reaction as a surrogate for (n,g) reaction of the long-lived fission product of ⁷⁹Se

⁷⁹Se is one of the long-lived fission products (LLFPs) of the nuclear waste. The half-life is as long as 3.3x10⁵ years. Though the LLFPs are considered to be stored in the deep geological repository, the site has not been determined in the most of countries in the world. Seeking for a way to transmute  such nuclei is expected for our descendants. Considering that the mean free path and the cross sections, the neutron induced reactions, such as (n,g) reaction, are promising for the transmutation. ⁷⁹Se is also important astrophysically because it is located on the path of s-process nucleosynthesis. This nucleus plays as a role of a cosmo chronometer. However the neutron capture reaction on the nucleus has not been experimentally evaluated partly because the selenium is toxic and the ⁷⁹Se is radioactive.  

   ^77,79Se(d,p)78,80Se reactions were measured in inverse kinematics as surrogate reactions of  ^77,79Se(n,g)^78,80Se, respectively. There is the experimental data of ⁷⁷Se(n,g)⁷⁸Se at 550 keV. The evaluated cross section of ⁷⁷Se(n,g)⁷⁸Se reaction from (d,p) reaction was used to verify the technique.  

  The experiment was carried out at the new energy degrading beam line name OEDO in RIBF. The ^77,79Se beams of about 20 MeV/nucleon were focused by OEDO on a secondary target of 4 mg/cm² thick CD₂ target. The excitation energy of the final state was determined by measuring the scattering angles and the energy of the recoiled proton by 6 telescopes of SSDs and CsI(Tl) placed in the backward angle. The residual nuclei were identified by the spectrometer which enabled us to determine the gamma emission channel without measuring the gamma rays.

   In this talk, the detailed experimental setup and the result of the evaluated cross section of ^77,79Se(d,p)^78,80Se reactions will be presented.