Search

We present results from time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory that are relevant for neutron star crust models. The masses of 16 neutron-rich nuclei in the scandium-nickel range were determined simultaneously, with the masses of 61V, 63Cr, 66Mn, and 74Ni measured for the first time with mass excesses of -30.510(890)MeV, -35.280(650)MeV, -36.900(790) MeV, and -49.210(990)MeV, respectively. With these results the locations of the dominant electron capture heat sources in the outer crust of accreting neutron stars that exhibit super bursts are now experimentally constrained. We find the experimental Q value for the 66Fe→ 66Mn electron capture to be 2.1 MeV (2.δ) smaller than predicted, resulting in the transition occurring significantly closer to the neutron star surface. [ABSTRACT FROM AUTHOR]

Abstract: The neutron long counter NERO was built at the National Superconducting Cyclotron Laboratory (NSCL), Michigan State University, for measuring neutron-emission probabilities. The detector was designed to work in conjunction with a implantation station, so that decays and neutrons emitted from implanted nuclei can be measured simultaneously. The high efficiency of about 40%, for the range of energies of interest, along with the small background, are crucial for measuring neutron emission branchings for neutron-rich r-process nuclei produced as low intensity fragmentation beams in in-flight separator facilities. [Copyright &y& Elsevier]