Heavy Ion Discussion Group, 6 October 2023, 3:30 p.m.

Title: New paths for the study of heavy nuclei

Speaker: Jonathan Bequet, Université Paris-Saclay

(Host: Marco Siciliano, PHY)
 
Abstract:

Most of the heaviest nuclei synthetized the last decades were obtained using fusion- evaporation reactions. Such a mechanism tends to produce neutron-deficient superheavy nuclei due to the limited choice of beam-target combinations (and neutron evaporation), most of them resulting in small cross-sections (for example, 0.5 pb at most for ²⁹⁴Og) [1]. Thus, Multi- Nucleon Transfer (MNT) reactions are expected to be a complementary mechanism to the fusion-evaporation one. Indeed, it is well suited to produce neutron-rich heavy ions with promising cross-sections for a production at zero degrees according to the theory [2] (up to 100 μb for the reaction used in the experiment described below).

A test experiment has been performed at Argonne National Laboratory in 2019 using a ¹³⁶Xe beam on a ²³⁸U target with detection of the reaction products at zero degree. The setup was made of the Gammasphere germanium array to perform a prompt gamma spectroscopy, the AGFA gas-filled separator (with He gas at 3 Torr) to isolate the MNT products and an implantation-decay spectroscopy station at the focal plane made-up of a DSSD, a PPAC and silicon tunnels with germanium clovers around them. In my talk, results coming from the analysis of this experiment will be shown. I will also describe the improvements made for the final experiment on ¹³⁶Xe + ²³⁸U that will take place this year.

A new facility which will enable cutting-edge studies of heavy and super-heavy nuclei is being built at GANIl (France) within the framework of the SPIRAL2 project. One of the detection setups made for this project is the new focal plane detector SIRIUS which will be used for the decay spectroscopy of heavy and superheavy nuclei. Following a brief description of SPIRAL2 and S3 (Super Separator Spectrometer), I will present you my work for the SIRIUS collaboration, focusing on the results from the beam test experiment done this year.

[1] Yu. Ts. Oganessian, V. K. Utyonkov, Yu. V. Lobanov, F. Sh. Abdullin, A. N. Polyakov, R. N. Sagaidak, I. V. Shirokovsky, Yu. S. Tsyganov, A. A. Voinov, G. G. Gulbekian, S. L. Bogomolov, B. N. Gikal, A. N. Mezentsev, S. Iliev, V. G. Subbotin, A. M. Sukhov, K. Subotic, V. I. Zagrebaev, G. K. Vostokin, M. G. Itkis et al., Synthesis of the isotopes of elements 118 and 116 in the ²⁴⁹Cf and ²⁴⁵Cm + ⁴⁸Ca fusion reactions, Phys. Rev. C 74, 044602 (2006).

[2] V.I. Zagrebaev and W. Greiner. Cross sections for the production of superheavy nuclei. Nuclear Physics A, 944:257–307, 2015. Special Issue on Superheavy Elements.