Research Experiences for Undergraduates
Summer 2003
Project Summary
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Research Experiences for Undergraduates Summer 2003 Project Summary |
Project Title: Investigating Radioactive Nuclei Beam Reactions with
a Large Area Neutron Detector
Student Name: Patrick J. Mears
Student’s home institution: Hope College
Research Advisor(s): Dr. P. A. DeYoung, Dr. G. F. Peaslee
Source of Support: NSF-RUI
In 2002 the Hope college nuclear group completed a large area neutron detector (Neutron Wall) for use at Notre Dame's Nuclear Structure Laboratory. The neutron wall consists of eight 60" x 6" x 2", position sensitive, plastic scintillators. In 2003, two experiments were conducted in which the neutron wall was used to detected neutrons in coincidence with other reaction products. In one experiment, a 26MeV 6He beam impacted a CH2 target to form 7Li*. The purpose was to investigate the structure of 7He. Rather than attempting to make 7He, the goal of this experiment was to populate the T=3/2 excited 7Li isobaric analog states of 7He. 7Li* was used because 7He has a 3x10^-21 second lifetime and is extremely difficult to obtain and use in experiments. The other experiment studied the 6He + 209Bi reaction at a beam energy of 23MeV. The halo nucleus of 6He consists of an alpha core with a two neutron "skin" that is much more loosely bond than the rest of the nucleus. In a previous experiment1 with 6He + 209Bi a large alpha cross section was observed. This experiment was done to further investigate 6He reactions with a focus on projectile breakup. When breakup occurs both neutrons are released from the alpha core. Because the alpha particle is charged its trajectory is affected by the Coulomb repulsion from the 209Bi nuclei. The trajectory of the neutrons, however, will be straight once they are released from the alpha core. The alpha particles were detected using two E-DE Si detectors and the neutrons were detecting using the neutron wall. After the experiment, events in which neutrons and alphas were detected in coincidence were identified. Neutron position and energy calibrations have been done. The next step is to look at the angular distribution of neutrons in the wall in an attempt to determine the cross section of 6He breakup in this experiment. Work with data from both experiments is being continued. 1E.F. Aguilera, et al. Phys. Rev. Lett. 84, 5058 (2000).
Slide show of Patrick Mear's work (Requires Microsoft PowerPoint or a PowerPoint viewer.)