Time-of-flight mass measurements of neutron-rich nuclei

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The masses of neutron-rich nuclei are needed for reliable astrophysical model calculations and have been shown to probe nuclear structure anomalies far from stability and to provide important constraints and tests for nuclear structure models. I propose here to measure the masses of 31 neutron-rich nuclei in the sulfur to cobalt region for the first time, using the well-established time-of-flight (TOF) method. The TOF technique for mass measurements has been proven to be an ideally suited method for mass measurements on very short-lived nuclides at the National Superconducting Cyclotron Laboratory (NSCL) in previous experiments. The results demonstrate that systematic uncertainties of the order of 150 keV (6keV/q) can be achieved with no obvious systematic trends as functions of neutron excess. This newly developed method shall be applied to a broad range of new masses to fully exploit it scientifically. There are a number of scientific questions this measurement will address, ranging from understanding neutron star crust processes and astronomical observations of X-ray transients to changes of nuclear structure far from stability such as new shell closures.