Hope College Department of Physics and Engineering
Research Experiences for Undergraduates
Summer 2004
Project Summary
Research Experiences for Undergraduates
Summer 2004
Project Summary
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Hope College Department of Physics and Engineering Research Experiences for Undergraduates Summer 2004 Project Summary |
Title : Investigating 6He Decay modes in the Reaction of 6He+209Bi near the Coulomb Barrier.
Name: Patrick J. Mears
Home Institution: Hope College
Research Advisor(s): Dr. P. A. DeYoung, Dr. G. F. Peaslee
Source of Support: NSF-RUI
The reaction of 6He+209Bi near the Coulomb barrier was studied to learn more about the properties of 6He, a rare Borromean nucleus. Recent studies found that the alpha- particle cross section in this reaction is higher than expected . The goal of this experiment was to gain insight into the significance of the three possible breakup modes of 6He; one-neutron transfer, two-neutron transfer and direct breakup. Previous work done by Hope student Joe Bychowski indicated that 20% of the total alpha cross section was due to one-neutron transfer.
A 23 MeV beam of 6He was created at Notre Dame's Nuclear Structure Lab, and then directed towards a thin 209Bi target, utilizing the TwinSol system. Neutrons created in the reaction were detected at angles ranging from 32-57 degrees relative to the 6He beam. Alpha particles were detected at +-90 and 120 degrees. Data was collected and analyzed using an Interactive Data Language program that was written by Hope College student Ben Hilldore.
Twice as many n-alpha coincidences were detected when neutrons and alphas at 90 degrees were on the same side as compared to alphas on the opposite side from the neutrons. A similar number of coincidence events were measured when alphas were detected at 120 degrees on the opposite side from the neutrons. These results indicate that two-neutron transfer is significant, since coincidence events on opposite sides must come from two-neutron transfer. They also indicate that breakup is significant because there are clearly more neutrons on the same side as the alphas. Current calculations indicate that 2-n transfer is responsible for 55 + 12% of the total alpha cross section at the “grazing peak.” More work is being done to understand what is happening at the forward angles.