Advancing Nuclear Science via Theory and Experiment

Led by Wilton Clifford at the University of Surrey, this Science and Technology Facilities Council (STFC)-funded project brings an international community of researchers and facilities together in order to gain experimental information about nuclei with unusual numbers of neutrons relative to protons so that theoretical ideas can be tested.

For a hundred years, atomic nuclei have been probed more or less exclusively by studying collisions between stable beams and stable targets. This restricted the nuclei that could be studied to just a just a small fraction of those that are thought to exist.

Most of the nuclei important to making all of the elements (in various stellar processes) have, for example, been inaccessible to experiment. The major thrust in nuclear physics worldwide, and a key priority in the UK's programme, is to reach out and study these exotic nuclei by using beams produced from short-lived radioactive isotopes.

This in turn reveals that nuclear structure is not always like it seems to be for the stable nuclei, and nuclei are found to have surprising trends in stability and to have different shapes that will affect reaction rates inside stars and supernovae.

Our science goals are aligned with current STFC strategy for nuclear physics, as expressed in detail through the Nuclear Physics Advisory Panel's road map. We wish to understand the boundaries of nuclear existence, i.e. the limiting conditions that enable neutrons and protons to bind together to form nuclei.

Under such conditions, the nuclear system is in a delicate state and shows unusual phenomena. It is very sensitive to the properties of the nuclear force. It is unknown whether, and to what extent, the neutrons and protons can show different collective behaviour or even how many neutrons can bind to a given number of protons. It is features such as these that determine how stars explode.

To tackle these problems, we need a more sophisticated understanding of the nuclear force and we need experimental information about nuclei with unusual numbers of neutrons relative to protons so that we can test our theoretical ideas.

At the University of Brighton we take the UK priorities and the new opportunities very much to heart, and we seek out and lead programmes at the world's best facilities for making radioactive beams. To make the beams is difficult and the facilities - as well as the research effort - are international in scale.

This grant funds innovative experiments, led by the University of Brighton, at the Radioactive Ion Beam Facility (RIBF) in Japan and at the GSI/FAIR facility in Germany.