Speaker
Description
For exotic nuclei, theoretical predictions of the $ \gamma $-ray strength function ($ \gamma $SF) exhibit large variations, which represent the dominant uncertainty in Hauser Feshbach calculations of neutron capture reaction rates. In particular, constraining the $ ^{146} $La(n,$ \gamma $)$ ^{147} $La and $ ^{147} $La(n,$ \gamma $)$ ^{148} $La reactions through experimentally determined nuclear level densities (NLDs) and $ \gamma $SFs will improve neutron reaction network calculations in the $ A = 147 $ mass region under neutron rich conditions. At Argonne National Laboratory using nuCARIBU at ATLAS, total absorption spectra and $ \gamma $-ray spectra for these La isotopes will be measured to constrain the NLDs and $ \gamma $SFs and, in turn, provide experimentally anchored neutron capture cross sections that are important for U.S. stockpile stewardship applications and for understanding the nucleosynthesis of heavy elements in the cosmos.
For La isotopes near stability, Oslo style measurements of $ ^{138,139,140} $La at the Oslo Cyclotron Laboratory indicate either a modest low energy enhancement (LEE) or a plateau like behavior at low $ \gamma $-ray energies. For Mo and Nd isotopes, the LEE decreases with increasing neutron number. This work will investigate whether a similar trend emerges for more neutron rich La isotopes. The high efficiency Summing NaI (SuN) detector, in combination with the SuN Tape system for Active Nuclei (SuNTAN), will be employed in an upcoming experiment that uses the $ \beta $ decay of $ ^{147,148} $Ba beams to populate excited states in $ ^{147,148} $La. The experimental plan for this campaign at nuCARIBU, along with anticipated analysis challenges, will be presented using a synthetic data set and the $ \beta $-Oslo method to assess the sensitivity to the NLD and $ \gamma $SF in this region.
| Contribution category | Experiment |
|---|---|
| Presenter status | Faculty/Staff |