Grant: Subatomic Physics Envelope - Project

Precision measurements of the atomic masses of nuclides far from stability provide information on the energy released in the decay and nuclear reactions involving these exotic, short-lived, nuclei. The results are an important ingredient in predicting the rates and pathways of nuclear reactions that power explosive astrophysical events thought to be responsible for the nucleosynthesis of the heavier elements (through the rp-, nu-p- and r-processes). The data also provides a view of nuclear structure in regions where the nuclei have extreme neutron to proton ratios and, provide an opportunity for the study of fundamental symmetries in particle physics theories. Currently, The Canadian Penning Trap Mass Spectrometer (CPT) is being used to measure the masses of very neutron-rich isotopes that lie on or near the expected reaction path for the astrophysical r-process, a region that lies near the edge of nuclear stability called the ""neutron dip line"". The nuclei of interest are provided by the CARIBU (Californium Radioactive Ion Beam Upgrade) facility at the Argonne Tandem Linear Accelerator System (ATLAS) at the Argonne National Laboratory. The exotic, neutron-rich, atoms are produced by spontaneous fission, in a 1.7 Ci, 252 Cf fission source and delivered (with a few keV of energy) to the CPT for a precise measurement of their mass. Alternately, the ions can also be transferred to a radio-frequency quadrupole ion trap (RFQ) where they are suspended in helium gas. Such a cloud of exotic nuclei, nearly at rest, provides a unique opportunity to study the correlations between the beta particles, the neutrinos and other particles emitted in their decay and test symmetries in particle physics theories. The amount requested will cover the operation and maintenance costs of the Canadian Penning Trap mass spectrometer (which is entirely Canadian owned), 3 graduate student stipends , the salary for a post-doctoral fellow and, travel costs to and from the facility. This work is carried out in collaboration with J. Clark and G. Savard, Physics Division, Argonne National Laboratory, Ralph Segel, Northwestern University, Nicholas Scielzo, Lawrence Livermore National Laboratory and Ani Aprahamian from Notre Dame University, all from the USA.