This award continues the research program of eight faculty members and their students in Nuclear Structure Physics and Nuclear Astrophysics at the University of Notre Dame. The program focuses on direct measurements of nuclear reaction and decay processes that determine the life of stars and the origin of the elements in the universe. This program addresses key nuclear processes that define the timescales of stellar evolution and explosion processes. Another component is the study of low energy fusion reactions during the last days of a stellar life prior to supernova explosion. The program also explores the nuclear structure effects and weak interaction processes that are guiding large scale nucleosynthesis processes. The research is performed primarily by using the accelerators of the Nuclear Science Laboratory (NSL) at the University of Notre Dame, which are uniquely designed to probe stellar reactions through a number of experimental techniques. The experimental results expand our knowledge of the fundamental structure of the nucleus as a multi-body quantum system; they also provide new insight for the astrophysics community on the origin of the elements and the chemical evolution of the cosmos from the Big Bang to the present. The NSL is uniquely equipped for performing this kind of research in a university environment. The award will support the training of a large number of graduate (approximately 30) and undergraduate students (approximately 20) in experimental and theoretical techniques to be ready to join the nuclear workforce of the nation.
The experimental program is based on the use of two accelerators at the NSL. Intense stable ion beams from the single ended 5U Pelletron are used for the direct study of low-energy capture and fusion reactions. Heavy ion beams are used to investigate such reactions in inverse kinematic technique using the St. GEORGE recoil separator. This separator is unique and serves as blueprint for the design of the SECAR separator at FRIB. The FN tandem accelerator is used as a multi-purpose instrument. It is operated as a driver for the production of radioactive beams at the TwinSol facility, the nationss first instrument for producing low energy radioactive beams. These beams allow direct reaction measurements with and the trapping of light radioactive particles at levels not possible at large national facilities. The FN also serves the accelerator mass spectrometry (AMS) program at the NSL, testing geological and cosmological samples for long-lived radioactivities. A large number of nuclear structure experiments is based on the operation of this machine using a variety of particle and gamma spectroscopy techniques. A smaller fraction of the program relies on the use of other national and international facilities to take advantage of higher energy beams not available at the NSL.
