Modeling Cosmic Nucleosynthesis

First measurements of isotopes produced by Argonne’s new CARIBU facility provide insight into the creation of the elements in the universe.

Image courtesy of Argonne National Laboratory

The Science

Today, scientists believe that most of the heavy elements present in the universe are the products of complex reactions in supernovae. These reactions may involve thousands of different isotopes, all within a few seconds. To gain a deeper understanding of the elemental abundances resulting from supernovae requires sophisticated computer models, which themselves require a vast number of physics inputs, the masses of the short-lived rare isotopes being one of the key parameters. Scientists have used the Penning trap mass spectrometer at the new Californium Rare Ion Breeder Upgrade (CARIBU) facility at Argonne National Laboratory to make exquisitely accurate measurements of the masses of rare isotopes.

The Impact

Simulations using these new mass measurements are opening new insights into the nuclear processes that occur in the violent conditions of supernovae, and may someday provide clearer explanations of the production of the elements in the universe.

Summary

Most of the light elements are produced in the cores of stars by fusion reactions. Scientists believe that large stars can produce a slew of heavier elements when they explode as supernovae. Thus, supernovae are thought to be a possible source of many of the heavy elements on Earth, such as silver, gold, and uranium. These elements are created through reactions involving thousands of different isotopes, all within a few seconds. An understanding of the elemental abundances resulting from supernovae requires sophisticated computer models, which themselves require a vast number of physics inputs, the masses of the short-lived isotopes being one of the key parameters. Although stars easily create these isotopes, they are challenging to produce here on Earth for study. At Argonne National Laboratory a new facility, the Californium Rare Ion Breeder Upgrade (CARIBU), now provides such isotopes. Furthermore, this facility is instrumented with a device capable of high-precision mass measurements: the Penning trap mass spectrometer. Mass measurements with a precision of 10-100 parts per billion have been carried out on 33 neutron-rich nuclei provided by CARIBU. First-ever simulations with direct mass information from the new CARIBU measurements indicate that the synthesis of elements heavier than tin in supernovae may be significantly delayed compared with similar simulations using theoretical masses instead. If further delays are found, supernovae may be determined not to be the main source of element production.

Contact

Dr. Guy Savard
Argonne National Laboratory and University of Chicago
[email protected]

Funding

DOE, Office of Science, Office of Nuclear Physics (NP)

Publications

J. Van Schelt et al., “First Results from the CARIBU Facility: Mass Measurements on the r-Process Path.” Phys. Rev. Lett. 111, 061102 (2013). [DOI: 10.1103/PhysRevLett.111.061102]