Session 1WCB: Nuclear Fission Turns 80 II

Fission of fermium isotopes using Langevin calculations

Fragment mass distributions in the fission of 246,264Fm at low excitation energies are studied using the three-dimensional Langevin equations with potential energy landscape of the two-centershell model.  After overcoming the 1st saddle point, the large-amplitude shape motion along a specific shape degrees of freedom is found in the 2nd minimum of the potential energy landscape due to the nature of the friction tensor in the Langevin equation. The 2nd-saddle points are found at two positions which links to the compact-symmetric scission and elongated-asymmetric scission, respectively, and they are located at both ends of the shape motion in the 2nd minimum. Height of the mass-symmetric 2nd saddle point relative to the asymmetric saddle point decreases toward heavier Fm isotopes. It was shown that not only the structure of the potential energy landscape but also the wide-range directive uctuation of nuclear shape have a crucial role to understand the mechanism of the sharp transition of mass asymmetry.   

Survey of current US fission experiments

As we approach the 80th anniversary of the discovery of nuclear fission, one might reasonably expect that there is little new information to be learned in this mature field. In reality, however, there is still a strong desire to advance our understanding of fission, which has led to a resurgence in fission experiments over the last decade. This is driven both by scientific curiosity, the role of fission in astrophysical processes, and the need for accurate and precise nuclear data for technology. As theoretical models of fission start to be more predictive and truly incorporate correlations, new experiments are essential for testing and validation purposes.

A new generation of fission experiments are being conducted world-wide, using both well-established and cutting-edge techniques and methodologies. In this presentation I will limit myself to a survey of experiments currently being pursued in the US, and provide a broad overview of the many classes of experiments underway around the country. I will discuss different detector types, irradiation facilities, experimental methods, and the important role that different types of samples play in fission experiments. I will also touch on ongoing efforts to improve fission nuclear data for specific application areas, such as nuclear nonproliferation.