Exotic nuclear systems probed with transfer reactions using solenoid spectrometers

Atomic nuclei consist of protons and neutrons, the numbers of which determine the element and the isotope. How these neutrons and protons interact defines the properties of any individual nucleus, for example its structure, its shape and whether it is stable or radioactive. These properties of atomic nuclei and the processes they undergo, such as nuclear fission, can then determine the abundance of the elements that we observe in nature. These elements are produced in many different ways, in many different astrophysical processes throughout the universe; such as neutron-star mergers, which have recently been observed. We do not yet fully understand the forces between neutrons and protons in nuclei, there is no one theoretical model that can describe every nucleus in the nuclear chart. Similarly our understanding of nuclear fission is limited in scope to systems near stability.

In order to understand the behavior of all nuclei across the nuclear chart, and how they are produced in these astrophysical processes, nuclear physicists have to study nuclei that live for only a very short amount of time, less than a second in many cases. This requires state-of-the-art facilities and techniques. Excitingly for nuclear physics research, a number of upgraded or new facilities that produce radioactive nuclei as beams for study are soon to start operation. These include the upgraded HIE-ISOLDE facility at CERN and the Facility for Rare Isotope Beams in the USA. Coupled to these facilities are the latest technologies for studying nuclear reactions on these beams of short-lived nuclei, based on repurposed magnets from former hospital MRI machines.

The aim of this Fellowship is to use these new devices to study the structure of nuclei using a method known as transfer reactions. In transfer reactions a single neutron or proton can be added to or taken away from a radioactive nuclei of interest, to study how that single particle behaves in different nuclei. I will look at reactions that remove a single proton from a nucleus to investigate how that one proton behaves, and how it interacts with the neutrons in that nucleus, providing information on the fundamental forces between neutrons and protons. I will also use these reactions to induce fission in short-lived systems to study how radioactive nuclei decay via this pathway and measure the distributions of elements and their isotopes that are produced. This will allow the study of fission in more short-lived systems, improving our understanding of this process and predictions of how it occurs in the very exotic nuclei produced in phenomena such as neutrons star mergers.