Jason Clark

Physics Division, Argonne National Laboratory


How were all the elements in the universe created? Scientists across many disciplines have been trying to answer this question for decades. Much progress in our understanding of nucleosyn- thesis has been made, but the origin of half the elements heavier than iron is still unknown. Supernovae are possible sources of heavy-element production, whereby elements are produced through a rapid series of nuclear reactions on neutron-rich nuclei in a process termed the astro- physical ‘r’ process. In an attempt to reproduce the observed distribution of element abundances in the universe, models are generated which inherently rely upon many nuclear physics inputs, including the masses of the nuclides involved and their beta-decay properties. However, the uncertainties in these nuclide properties are often too large and limit our understanding of heavy-element nucleosynthesis.

Ion traps have revolutionized mass spectroscopy and have the potential to do the same for beta-decay spectroscopy as well. Precise mass measurements of radioactive nuclides are now routinely performed around the world, but nuclides involved in the astrophysical r process are often too challenging to produce for study at accelerator facilities. The newly commissioned CARIBU facility, an upgrade to Argonne National Laboratory’s ATLAS facility, provides copi- ous amounts of these previously elusive neutron-rich nuclei. A program of mass measurements at CARIBU is underway, where the Canadian Penning trap mass spectrometer has already been used to determine the masses of more than 100 of these nuclides to a mass precision of 100 parts per billion or better. In addition, a specially designed ion trap is currently being developed to facilitate a new program of beta-decay spectroscopy using nuclides produced by CARIBU. Results from a recent set of measurements have indicated this new technique of using ion traps to perform beta-decay studies could significantly advance the field. Indeed, ion traps for astro- physics are going where no trap has gone before.