National Superconducting
Cyclotron Laboratory

Brad  Sherrill
Brad Sherrill
NSCL Laboratory Director, University Distinguished Professor of Physics
Experimental Nuclear Physics
PhD, Physics, Michigan State University 1985
Joined NSCL in January 1981
Phone (517) 908-7718
Fax (517) 353-5967
Office 2303
sherrill@frib.msu.edu

Brad Sherrill

Approximately 270 isotopes are found naturally. However, many more isotopes, nearly 7,000 in total, can be produced by particle accelerators or in nuclear reactors. These isotopes are radioactive and spontaneously decay to more stable forms, and I work to produce and separate the new and interesting ones.

There are several reasons why a demand exists within the scientific community for new, rare isotopes. One is that the properties of particular isotopes often hold the key to understanding some aspect of  nuclear  science. Another is that the rate of certain nuclear reactions involving rare isotopes can be important for modeling astronomical objects, such as supernovae. Yet another is that the properties of atomic nuclei can be used to test nature’s fundamental symmetries by searches for deviations from known symmetry laws. Finally, the production of isotopes benefits many branches of science and medicine as the isotopes can be used as sensitive probes of biological or physical processes.

The tools for production and separation of rare isotopes gives scientists access to designer nuclei with characteristics that can be adjusted to the research need. For example, super-heavy isotopes of light elements, such as lithium, have a size nearly five times the size of a normal lithium nucleus. The existence of such nuclei allows researchers   to study the interaction of neutrons in nearly pure neutron matter, similar to what exists in neutron stars.

For production of new isotopes, the approach that I have helped develop is called in-flight separation; where a heavy ion, such as a uranium nucleus, is broken up at high energy. This produces a cocktail beam of fragments that are filtered by a downstream system of magnets called a fragment

separator. Our current research is focused on preparing for experiments at FRIB where we hope to discover nearly 1,000 new isotopes. Simultaneously, we will study the nuclear reactions that produce new isotopes and work to better understand the best ways to produce any given isotope. We use and work to improve the modeling code LISE++, which involves interesting problems in computational science.

Research in this area includes study and design of magnetic ion optical devices. learning the various nuclear production mechanisms and improving models to describe them. This background allows one to contribute to science by making new isotopes, but also prepares one for a broad range of careers in academia, government (e.g. national security), and industry.

 Magic numbers

The rich variety of nuclei is indicated by the depiction of three isotopes 4He, 11Li, and 220Ra overlaid on the chart of nuclides where black squares indicate the combination of neutrons and protons that result in stable isotopes, yellow those produced so far, and green those that might exist.

Selected Publications

NSCL and FRIB at Michigan State University: Nuclear science at the limits of stability; A. Gade and B.M. Sherrill, Physica Scripta Volume: 91 (2016) 053003

Location of the Neutron Dripline at Fluorine and Neon; D.S. Ahn,  et al., Physical Review Letters 123 (2019)

Discovery of Ca-60 and Implications for the Stability of Ca-70; O.B. Tarasov, et. al., Physical Review Letters 121 (2018)

From isotopes to the stars, M. Thoennessen, B.M. Sherrill, Nature 473 (2011) 25.