Current research

Exploring the changing shell structure of nuclei

Prof. S. J. Freeman

The single-particle character and the associated shell structure of nuclei is the foundation of much of our understanding of nuclear physics. The introduction of the spin-orbit interaction by Goepper-Maier and Jensen led to an understanding of the observed shell gaps and magic numbers in near-stable nuclei. The appearance of these ideas in undergraduate textbooks gives the impression of solidity and permanence to the well-known sequence of magic numbers. Recent observations, however, have challenged this basic assumption by suggesting that the sequence of single-particle states observed near stability is actually quite fragile; studies of nuclei far from the line of beta stability have begun to indicate that the familiar shell gaps do not persist in exotic systems. Instead, shifts in the sequence of single-particle levels conspire to give gaps which change with changing nucleon number, fundamentally reshaping the basis of nuclear structure and producing new and unexpected phenomena. The reasons for these fundamental alterations to one of the basic tenets of nuclear physics are currently being debated and are of paramount interest in the development of the understanding of atomic nuclei. Performing measurements on the neutron-rich side of stability is difficult, but the use of binary reactions such as transfer and deep-inelastic collisions provide a route to populating the nuclei of interest. We are using a large array of germanium detectors in combination with a large acceptance, braid range spectrometer at Legnaro Laboratory in Italy, to select and study exotic neutron-rich nuclei. This combination known as CLARA and PRISMA are shown in the photo below.

Find out more about exploring the changing shell structure of nuclei.

The measurement of the lifetimes of unbound and isomeric nuclear states and improving SPECT images and dosimetry for cancer therapy The Christie hospital

Dr D. M. Cullen

Understanding Long-Lived or Isomeric nuclear states.

An isomer is an excited nuclear state which is long-lived because its decay is inhibited by nuclear structure effects. Several isomers are known with lifetimes ranging from several years (178Hf) to longer than 10^15 years. These isomers represent very stable nuclear states and often survive longer than the nuclear ground state. They have clearly influenced the structure of our Universe because they provide additional waiting points in rapid-neutron capture reactions which occur in supernovae explosions, and are responsible for the isotopic abundances of the elements in our Universe. Techniques have been and are being developed to enhance the ability to study these nuclei at the proton drip line. The main research experiments take place in Finland and the USA. As a result of these experiments, a better understanding of the main reasons for isomerism in this mass region have been established. The isomer decay hindrance in the Fermi-Golden rule comes from a difference in nuclear shape between the isomeric state and the state to which it decays. A recent development to our techniques has been the development of a Differential Plunger which allows the lifetimes of Unbound Nuclear States (DPUNS) to be determined beyond the proton drip line for the first time. As part of this research, a new isotope 140Dy was established along with its ground state rotational band.

Improving the accuracy of dosimetry and image quality with medical SPECT scanners.

This work is a new development from our existing STFC IPS collaboration with the Nuclear Medicine department at The Christie NHS Foundation Trust, which focuses on the interactions of the gamma and beta radiation used in Targeted Radionuclide Therapy (TRT) for specific cancers. Over the last four years, we have developed techniques based on Monte Carlo simulation of the GE Infinia Hawkeye 4 Single Photon Emission Computed Tomography (SPECT) scanner which have been shown to significantly improve the dosimetry accuracy for TRT with 177Lu. This work is currently being developed to provide a verifiable improvement in whole organ dosimetry for patients receiving treatment with 177Lu Dotatate for metastatic neuroendocrine cancer at The Christie Hospital. Therapy with 90Y has increased significantly in the last 3 years and currently accounts for a significant proportion of the 10,000 TRT therapies performed annually in the UK.

Both of these programmes are always looking for PhD students.

To find out more about these projects follow this link. .