I. P. Carter

Reduced quasifission competition in fusion reactions forming neutron-rich heavy elements

This work is supported by the National Science Foundation under Grants No. PHY-1102511 and No. IIA-1341088, by the U.S. Department of Energy under Grant No. DE-FG02- 96ER40975 with Vanderbilt University, and the Australian Research Council Grants No. DP110102858, No. DP140101337, No. FL110100098, No. DP130101569, No. FT120100760, and No. DE140100784. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award No. DE-NA0000979. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357. This research used resources of ANL’s ATLAS facility, which is a DOE Office of Science User Facility.

Competition between Fusion and Quasi-fission in the Formation of Super-heavy Elements

Quasifission is a non-equilibrium dynamical process resulting in rapid separation of the dinuclear system initially formed after capture and sticking of two colliding heavy nuclei. This can inhibit fusion by many orders of magnitude, thus suppressing the cross section for formation of superheavy elements. Measurements with projectiles from C to Ni, made at the Australian National University Heavy Ion Accelerator Facility, have mapped out quasifission characteristics and systematics using mass-angle distributions (MAD) - the fission mass-split as a function of centre-of-mass angle. These provide information on quasifission dynamics in the least model-dependent way. Quasifission time-scale information in the MAD has been compared with TDHF calculations of the collisions, with good agreement being found. Most significantly, the nuclear structure of the two colliding nuclei has a dramatic effect on quasifission probabilities and characteristics in gentle collisions at near-barrier energies. The effect of static deformation alignment, closed shells and N/Z matching can completely change reaction outcomes. The realization of this strong dependence makes modelling quasifission and superheavy element formation a challenging task, but should ultimately allow more reliable prediction of superheavy element formation cross sections.

Applications of a superconducting solenoidal separator in the experimental investigation of nuclear reactions

This paper describes applications of a novel superconducting solenoidal separator, with magnetic fields up to 8 Tesla, for studies of nuclear reactions using the Heavy Ion Accelerator Facility at the Australian National University.

Challenges in describing nuclear reactions outcomes at near-barrier energies

The properties of light nuclei such as 6Li, 7Li, 9Be and 12C, and their reaction outcomes are known to be strongly influenced by their underlying α-cluster structure. Reaction models do not yet exist to allow accurate predictions of outcomes following a collision of these nuclei with another nucleus. As a result, reaction models within GEANT, and nuclear fusion models do not accurately describe measured products or cross sections. Recent measurements at the Australian National University have shown new reaction modes that lead to breakup of 6Li, 7Li into lighter clusters, again presenting a further challenge to current models. The new observations and subsequent model developments will impact on accurate predictions of reaction outcomes of 12C - a three α-cluster nucleus – that is used in heavy ion therapy.