The Canadian Penning Trap (CPT) mass spectrometer at the Argonne National Laboratory makes precise mass measurements of both stable and unstable nuclides. To date, more than 60 radioactive isotopes having half-lives as short as one second have been measured with the CPT with a mass precision approaching 10 ppb. This thesis will present measurements made of nuclides along the rp-process path, which describes a process resulting from a series of rapid proton-capture reactions in an astrophysical environment. One possible site for the rp-process mechanism is an x-ray burst which results from the rapid accretion of hydrogen and helium from one star onto the surface of its neutron star binary companion. Mass measurements are required as key inputs to network calculations used to describe the rp-process in terms of the abundances of the nuclides produced, the light-curve profile of the x-ray bursts, and the energy produced. This thesis will describe the CPT apparatus, explain the method used to make precise mass measurements, and present the masses of the "waiting-point" nuclides ⁶⁸Se and ⁶⁴Ge. The mass measurement results, when used in x-ray burst models, confirm both ⁶⁸Se and ⁶⁴Ge as waiting-point nuclides which delay the rp-process by approximately 30 s and 7 s respectively. / October 2005

The Canadian Penning Trap (CPT) mass spectrometer at the Argonne National Laboratory makes precise mass measurements of both stable and unstable nuclides. To date, more than 60 radioactive isotopes having half-lives as short as one second have been measured with the CPT with a mass precision approaching 10 ppb. This thesis will present measurements made of nuclides along the rp-process path, which describes a process resulting from a series of rapid proton-capture reactions in an astrophysical environment. One possible site for the rp-process mechanism is an x-ray burst which results from the rapid accretion of hydrogen and helium from one star onto the surface of its neutron star binary companion. Mass measurements are required as key inputs to network calculations used to describe the rp-process in terms of the abundances of the nuclides produced, the light-curve profile of the x-ray bursts, and the energy produced. This thesis will describe the CPT apparatus, explain the method used to make precise mass measurements, and present the masses of the "waiting-point" nuclides ⁶⁸Se and ⁶⁴Ge. The mass measurement results, when used in x-ray burst models, confirm both ⁶⁸Se and ⁶⁴Ge as waiting-point nuclides which delay the rp-process by approximately 30 s and 7 s respectively.

The Canadian Penning Trap (CPT) mass spectrometer at the Argonne National Laboratory makes precise mass measurements of both stable and unstable nuclides. To date, more than 60 radioactive isotopes having half-lives as short as one second have been measured with the CPT with a mass precision approaching 10 ppb. This thesis will present measurements made of nuclides along the rp-process path, which describes a process resulting from a series of rapid proton-capture reactions in an astrophysical environment. One possible site for the rp-process mechanism is an x-ray burst which results from the rapid accretion of hydrogen and helium from one star onto the surface of its neutron star binary companion. Mass measurements are required as key inputs to network calculations used to describe the rp-process in terms of the abundances of the nuclides produced, the light-curve profile of the x-ray bursts, and the energy produced. This thesis will describe the CPT apparatus, explain the method used to make precise mass measurements, and present the masses of the "waiting-point" nuclides ⁶⁸Se and ⁶⁴Ge. The mass measurement results, when used in x-ray burst models, confirm both ⁶⁸Se and ⁶⁴Ge as waiting-point nuclides which delay the rp-process by approximately 30 s and 7 s respectively.

The Canadian Penning Trap mass spectrometer located at Argonne National Laboratory has been built for the purpose of studying the masses of both stable and unstable nuclides. For this thesis 18 proton-rich unstable nuclides of elements Nb, Mo, Tc, Ru and Rh have been measured with this apparatus to an average precision of 7.8 x10^−8. The masses of 6 of these nuclides had not been measured when this thesis was undertaken, and 4 more were not known to the precisions required for use in astrophysical nucleosynthesis models. The masses of these nuclides were of particular interest as the reaction paths of two proposed nucleosynthetic processes, the rp and νp processes, pass through this region. The rp process is thought to occur in X-ray bursts and directly affects the X-ray luminosity which is emitted from these objects. The νp process is thought to occur in the inner regions of the material ejected during a core-collapse supernova explosion and is of particular interest as it may answer some outstanding questions about the origins of the chemical elements in the Universe. The Canadian Penning Trap and associated apparatus were used to determine the masses of 18 nuclides, some for the first time ever. Our measurements improve the precision on all of the masses, by a factor of 70 in some cases. Our results are necessary to determine the proton-separation energies for these nuclides which are critical for determining the paths and reaction rates of the rp and νp processes. In particular, the effect of our measurements of 92Ru and 93Rh on the expected production ratio of 92Mo to 94Mo in the νp process, and the effect of our measurement of 87Mo on the path of this process will be discussed.

The Canadian Penning Trap mass spectrometer located at Argonne National Laboratory has been built for the purpose of studying the masses of both stable and unstable nuclides. For this thesis 18 proton-rich unstable nuclides of elements Nb, Mo, Tc, Ru and Rh have been measured with this apparatus to an average precision of 7.8 x10^−8. The masses of 6 of these nuclides had not been measured when this thesis was undertaken, and 4 more were not known to the precisions required for use in astrophysical nucleosynthesis models. The masses of these nuclides were of particular interest as the reaction paths of two proposed nucleosynthetic processes, the rp and νp processes, pass through this region. The rp process is thought to occur in X-ray bursts and directly affects the X-ray luminosity which is emitted from these objects. The νp process is thought to occur in the inner regions of the material ejected during a core-collapse supernova explosion and is of particular interest as it may answer some outstanding questions about the origins of the chemical elements in the Universe. The Canadian Penning Trap and associated apparatus were used to determine the masses of 18 nuclides, some for the first time ever. Our measurements improve the precision on all of the masses, by a factor of 70 in some cases. Our results are necessary to determine the proton-separation energies for these nuclides which are critical for determining the paths and reaction rates of the rp and νp processes. In particular, the effect of our measurements of 92Ru and 93Rh on the expected production ratio of 92Mo to 94Mo in the νp process, and the effect of our measurement of 87Mo on the path of this process will be discussed.