Grant: Subatomic Physics Envelope - Project

How the elements, from hydrogen to uranium, that make up our universe, were synthesized from the debris of the big bang continues to be a fascinating conundrum. While some success has been achieved in explaining the production of the light isotopes the mechanisms responsible for the production of the bulk of the heavier elements are still not clear. Calculations based on normal, quietly burning stars do not reproduce the observed abundances for these elements. It is thought that at least part of their production took place during explosive astrophysical events (supernovae and x-ray bursts etc.) that are powered by nuclear reactions among short-lived, radioactive nuclides at the limits of nuclear binding. The atomic masses of these nuclei are essential to understanding these processes because they determine the energy released and determine the path of the nuclear reaction chains that take place in these events. We have constructed a unique instrument system, the Canadian Penning Trap mass spectrometer (CPT), to accurately measure the masses of a wide variety of these short lived, exotic nuclei with great accuracy and sensitivity. The CPT operates on line to the Argonne Tandem Linear Accelerator System (ATLAS) at the Argonne National Laboratory (ANL). Recently a new facility, CARIBU, was added to the laboratory to provide beams of very neutron rich nuclei to the experiments. We plan to study the properties of these neutron rich nuclei that define the reaction paths of the astrophysical r-process. We anticipate that our results will address many exciting scientific issues in nuclear astrophysics and shed some light on possible explanations for the synthesis of the heavier elements. Our ion-trap system enables us to capture and hold exotic atoms produced in nuclear reactions nearly at rest in the laboratory. This is an ideal setup to study the correlations between the particles emitted in the radioactive decay of these atoms. We are currently examining the decay of a light isotope of lithium (A=8) to learn about the correlations between the electron and the neutrino emitted during its decay.