MRI Collaborative: Development of the LSU/FSU Split-Pole Spectrograph System at the FSU Accelerator Laboratory

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This Major Research Instrumentation award will enable the installation of a large acceptance, high-resolution magnetic spectrograph at the John D. Fox Accelerator Laboratory of Florida State University (FSU) and the development of a suite of state-of-the-art auxiliary detectors around it. This instrument will allow precision measurements of certain nuclear properties, which determine the energy release and time scale of stellar explosions and studies of the physics of unbound atomic nuclei in general. This instrument reclaims the capability to perform such precision measurements in the USA. This collaborative MRI award will fund the installation of a large-acceptance, high-resolution Enge split-pole spectrograph (SPS) at the accelerator laboratory at FSU with the purpose of studying the physics of resonant nuclear states that impact nuclear astrophysics and nuclear structure. The SPS became available upon the cessation of operations at the Wright Nuclear Structure Laboratory at Yale University. This project will install the 32-tonne instrument at FSU and augment its research capabilities by upgrading its focal plane detectors and developing a new Silicon detector array, in parallel at Louisiana State University (LSU), for efficient spectroscopy of unbound resonances.The properties of un-bound nuclear states, or resonances, have become a focal point of present day nuclear science as they present the doorway through which stars and stellar explosions build up the elements and release energy. The LSU/FSU collaboration previously developed the Array for Nuclear Astrophysics and Structure with Exotic Beams (ANASEN) for high-efficiency studies of such reactions using beams of radioactive nuclei. A new opportunity for advancing our understanding of nuclear reactions with astrophysical importance stems from the unique combination of high-precision spectroscopy performed with the SPS with the existing program of high-sensitivity studies with radioactive beams currently being performed with ANASEN. The proposed SPS system also creates an important discovery potential for the physics of exotic nuclear states, studied through a systematic investigation of particle orbitals beyond the binding limit. The interaction of nuclear orbits across shell closures is of importance to the physics of exotic nuclei at the limits of binding. The modification of nuclear properties through the presence of extended wavefunctions will be studied through a detailed spectroscopy of un-bound resonances, studying the presence of the Super-radiance mechanism in the presence of competing particle-decay channels. Again, the research at the SPS is not only complementary, but important to current and future studies with radioactive beams at FSU and the future Facility for Rare isotope Beams (FRIB). The proposed program around the SPS is a complementary effort and aims to address a lack of experimental opportunities with stable nuclear beams within the U.S. scientific program. Operated by a collaboration of two vibrant research groups, the SPS has the potential to become a national resource in the education of the next generation of scientists.