Speaker
Description
The oscillations in the excitation function of $^{12}$C+$^{12}$C, from energies above the Coulomb barrier down to the astrophysical region, is believed to be associated to molecular states in the compound nucleus [1], or linked to the fusion dynamics. Cluster states has been identified for example in $^{24}$Mg near subsystems breakup threshold, as $^{12}$C+$^{12}$C and $^{16}$O+$2\alpha$/$^{8}$Be with substantial $\alpha$ decay as 0$^{+}$ states [2], and the impact on carbon fusion needs to be evaluated.
The STELLA apparatus is designed to identify the evaporated charged particles of the $^{12}$C($^{12}$C,$\alpha$)$^{20}$Ne$^{(*)}$ and $^{12}$C($^{12}$C,p)$^{23}$Na$^{(*)}$ reactions. It combines a array of high granularity silicon detectors for charged particle detection in coincidence with the corresponding recoils' de-sexcitations $\gamma$ rays with LaBr$_{3}$ scintillators [3]. This technique enables a clear identification of populated excitation channels over a wide angular coverage.
New measurements of the excitation function arround the barrier have recently been performed at the Felsenkeller Underground Laboratory in Dresden, Germany, with fine energy steps. These new measurements allow for investigating the angular distributions of p and $\alpha$, associated to ground and excited states of the respective evaporation residues. This allows J$^{\pi}$ assignments and to calculate the respective exclusive cross sections. This upgraded STELLA configuration will be presented.
[1] David Jenkins and Sandrine Courtin. Weighing the evidence for clustering in nuclei. Journal of Physics G: Nuclear and Particle Physics, 42(3):034010, feb 2015.
[2] P. Adsley, et al. Extending the hoyle-state paradigm to $^{12}$C+$^{12}$C fusion. Phys. Rev. Lett., 129:102701, Sep 2022.
[3] M. Heine et al. The STELLA apparatus for particle-gamma coincidence fusion measurements with nanosecond timing. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 903:1–7, 2018.