26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Investigation of excitation energy dependence of fission modes in actinides through transfer-induced fission

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral AIP | Nuclear and Particle Physics (NUPP)

Description

Nuclear fission, wherein one nucleus splits into two fragments, is one of the most complex processes in nuclear physics.
The fissioning nucleus can be visualised as a series of nuclear shape evolution following a trajectory on the topography of the potential energy surface.
Various fission outcomes arise starting from the same compact configuration, due to features on the multidimensional potential energy surface.
These bifurcation of fission paths manifest as different structures on the fission fragment mass distribution, giving complex dependencies as a function of fissioning nuclei species and excitation energy.
The fission of actinides and the competition between different fission modes in this region of the nuclear chart are well studied, however the nature and moment along the fission path where different fission outcomes are determined are currently under debate.
To understand the nature of bifurcations and the underlying shell effects in fission, we developed a technique to investigate how the fission mass distributions vary with excitation energy of the fissioning system.
Transfer-induced fission in (d,p) reactions with $^{232}$Th, $^{235}$U, $^{238}$U, $^{244}$Pu, $^{243}$Am, $^{248}$Cm targets have been measured at the Heavy Ion Accelerator Facility at the Australian National University.
In these reactions, the incident deuteron transfers a neutron to the target nucleus, inducing fission at a range of excitation energies beginning just above the fission barrier.
Measurement of the coincident proton energies that triggered fission allows precise reconstruction of the excitation energy of the fissioning system.
This was achieved by merging two existing detector systems: multi-wire proportional counters that detect binary fission fragments and $\Delta$E-E silicon detectors that detect and characterise the outgoing proton.
In this talk, I introduce the analysis methods developed to extract fission modes by integrating data from two detector arrays and present the excitation energy dependence of shell-driven fission modes and angular anisotropies, across the actinides.