Refinement of the First r-process Abundance Peak Via High-Precision Mass Measurements

Abstract: Since the 1960's a general understanding of the creation of the chemical elements in the universe has existed. However, in recent decades this understanding has undergone refinement in describing the exact astrophysical mechanisms which result in the synthesis of isotopes, particularly those heavier (i.e. more protons) than iron.

After the first detection of a binary neutron star merger and it's subsequent kilonova in 2017, efforts into understanding the rapid neutron capture process (r-process) were redoubled in the form of both experimental and theoretical work. In particular, work has been performed investigating nuclei at the so-called waiting points of the r-process which result in the formation of the r-process abundance peaks. To this end, the underlying nuclear properties of the involved isotopes, specifically high-precision mass measurements of these nuclei are crucial in understanding the competition between neutron capture, photodissociation, and beta decay. At TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN), the Multiple-Reflection Time-of-Flight Mass Spectrometer (MR-TOF-MS) provides experimental access to this property for short lived radioactive isotopes with low production rates in an environment with high backgrounds. A novel technique used at TITAN's MR-TOF-MS for reducing background contamination, mass-selective re-trapping, was established. Mass measurement results using the TITAN MR-TOF-MS and their subsequent effect on the formation of the first r-process peak is presented. Additionally, the technique of mass-selective re-trapping is investigated in detail, and recent upgrades to the technique are discussed.