DREB Conference 2024

The $^{85}$Kr(d,p$\gamma$)$^{86}$Kr reaction has been carried out at 10 MeV/u in inverse kinematics at Argonne's ATLAS facility using the HELIOS spectrometer and the Apollo array. The neutron capture cross section on the radioisotope $^{85}$Kr (T$_{1/2}$ = 10.7 yr), an s-process branching point nucleus, carries a significant uncertainty due to the challenges of direct measurements. However, $^{85}$Kr can be accelerated as a pure beam, and the (d,p$\gamma$) reaction has been demonstrated to be a reliable indirect probe of the (n,$\gamma$)-reaction cross section. Neutron excitations from around 2-14 MeV in $^{86}$Kr were populated, where S$_n$=9.86 MeV, with a Q-value resolution of about 150 keV. The $\gamma$-ray emission probabilities as a function of excitation energy [P$_{p\gamma}$(E$_{ex}$)] were determined. The $2^+ \to 0^+$ and $4^+ \to 2^+$ $\gamma$-rays are clearly observed, showing the characteristic constant value of P$_{p\gamma}$ below S$_n$ and a decrease above S$_n$. These data are used to extract the cross sections for $^{85}$Kr(n,$\gamma$) reaction, complementing recent direct, high-precision measurements on the stable Kr isotopes. The technique has significant potential for future indirect (n,$\gamma$)-reaction studies.

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract No. DE-AC02- 06CH11357. This research used resources of ANL’s ATLAS facility, which is a DOE Office of Science User Facility.