RUI: Experimental Research in Nuclear Astrophysics and Nuclear Structure

Indiana University, Bloomington IN

Investigators

Abstract

The broad picture of how elements are produced by nuclear reactions in stars has been known for decades, but many important details of this process remain to be discovered. This award supports the participation of the PI and undergraduate students at Indiana University South Bend (IUSB) in a series of experiments to study nuclear reactions involving the fusion of a helium nucleus with another, heavier nucleus, which are important for a complete understanding of the helium-burning phase of stellar evolution. The experiments utilize the St. George recoil mass separator, a device recently commissioned at the University of Notre Dame's Nuclear Science Laboratory that allows measurements of the rates of these reactions at very low energies, close to the energies at which the reactions occur inside stars. IUSB students will participate in the collection and offline analysis of data from these experiments; in particular, by contributing to the development of analysis techniques that are specific to this new experimental device. The award also supports the continuing participation of the IUSB group in experiments using the MoNA-LISA neutron detectors for studies of the structure of rare isotopes at the National Superconducting Cyclotron Laboratory (NSCL) and the Facility for Rare Isotope Beams (FRIB) at Michigan State University. The detection system for St. George utilizes measurements of time-of-flight and energy to distinguish between alpha-capture reaction products and residual beam particles (aka background) on the basis of mass. The IUSB group will develop techniques to normalize particle detectors to the integrated beam flux in St. George, participate in data collection and online analysis during, and participate in offline analysis and interpretation of collected data. Work will begin with a commissioning experiment which will be a study of the 14N(alpha,gamma)18F reaction. This reaction is the first step toward the production of Ne-22, which is a neutron source for the s-process via the via the reaction 22Ne(alpha,n)25Mg. St. George is well suited, because of its large angular and energy acceptances, to extend cross section measurements for alpha-capture reactions into new energy ranges and reduce uncertainties in key stellar reaction rates. The award also supports research on the structure of nuclei near the neutron dripline, utilizing the MoNA-LISA neutron detector array at the National Superconducting Cyclotron Laboratory. IUSB is a member institution of the MoNA Collaboration, and the PI and IUSB students will participate in data collection during MoNA experiments at the NSCL and in the shared data analysis that is a hallmark of the MoNA Collaboration. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.