Speaker
Description
The Oslo Method is a powerful tool that allows for detailed studies of the Nuclear Level Density (NLD) and $\gamma$-ray strength function ($\gamma$SF) at energies below the neutron separation energy. In the last decade, several Oslo Method experiments have been performed at iThemba LABS, most notably with inverse-kinematics. Coupling the Oslo Method with inverse kinematics allows for study of nuclei that otherwise would have been inaccessible due to chemical properties or short half-life.
The first ever inverse-Oslo method experiment was performed at iThemba LABS in 2015 where an $^{86}\mathrm{Kr}$ beam impinged on a deuterated polyethylene target [1]. Following the success of this experiment two more inverse-kinematics experiments was performed with $^{84}\mathrm{Kr}$ and $^{132}\mathrm{Xe}$ beams, to study the NLD and $\gamma$SF of $^{85}\mathrm{Kr}$ and $^{133}\mathrm{Xe}$, respectively.
It has been suggested that for very hot plasmas the nucleus should interact with electrons (Nuclear Plasma Interaction/NPI), as the level spacing within the quasi-continuum would be on a similar scale as the electron energies [2]. The strength of the interaction would be strongly affected by the magnitude of the $\gamma$SF at low energy and accurate measurement of the low energy region of the $\gamma$SF is critical to give accurate theoretical estimates for the magnitude of this effect. The effect of NPI has been tested on $^{133}\mathrm{Xe}$ at Lawrence Livermore National Laboratory [2], which is the main motivation for measuring the $\gamma$SF and NLD of $^{133}\mathrm{Xe}$.
The reason for investigating the NLD and $\gamma$SF of $^{85}\mathrm{Kr}$ is due to the significant structural changes that nuclei near magic numbers typically undergo. By examining NLD and $\gamma$SF data for $N=49$ and $N=51$ isotopes of $\mathrm{Kr}$, valuable information about these structural changes can be revealed. Additionally, the mass region around $\mathrm{A}\sim 80$ is important for nucleosynthesis, as $^{85}\mathrm{Kr}$ functions as a branching point nucleus for the s-process, and nuclei within this range can have an impact on the weak r-process. Therefore, the existence of a low energy enhancement in this region could have a significant impact on nucleosynthesis models [3].
In this talk I will present the results of inverse-Oslo experiments performed at iThemba LABS, as well as the NLD and $\gamma$SF of $^{63}\mathrm{Ni}$, which has been measured with the Oslo Method with normal kinematics at iThemba LABS [4].
[1] V. W. Ingeberg et al., EpJ A 56, 68 (2020)
[2] D. L. Bleuel et al., Plasma and Fusion Research 11, 3401075 (2016)
[3] A. C. Larsen and S. Goriely, Phys. Rev. C 82, 14318 (2010)
[4] V. W. Ingeberg et al., Phys. Rev. C 106, 054315 (2022)
| Attendance Type | In-person |
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