Production and use of radioactive ion beams for measurements of nuclear reactions.

Abstract

There are pressing needs for data on the properties of short-lived, radioactive nuclei in astrophysics and other fields. We have built a Radioactive Ion Beam (RIB) facility, which includes a primary target chamber, a superconducting magnetic solenoid, a secondary target chamber, and a $\Delta$E-E$\sb{\rm R}$ detector system. The facility is attached to a dedicated beam line from the University of Notre Dame's Van de Graaff accelerator. Radioactive ions are produced by directing a stable beam onto a stable target. The ions are collected and focused by the solenoid to form a radioactive beam. Our RIB facility can generate well focused and energy-resolved beams of ions such as $\sp6$He, $\sp8$Li, and $\sp7$Be. Following the successful production of radioactive beams, we used a 14.4 MeV $\sp8$Li beam to bombard various targets. Nuclear reactions such as elastic and inelastic scattering, and one nucleon transfer have been observed. This thesis presents results for ($\sp8$Li, $\sp7$Li) one neutron transfer reactions on $\sp2$H, $\sp9$Be, $\sp{12}$C, $\sp{13}$C. Our data show that ($\sp8$Li, $\sp7$Li) is the dominant $\sp8$Li-induced reaction and that other nucleon transfer reactions are weaker. Comparison of our measured differential cross sections with FRDWBA calculations suggests that ($\sp8$Li, $\sp7$Li) is essentially a direct reaction. The measured cross section for $\sp2$H($\sp8$Li, $\sp7$Li)$\sp3$H may be large enough to effectively reduce the production rates of isotopes heavier than $\sp{12}$C in the non-standard big bang model. All $\sp8$Li-induced reactions observed have relatively large cross sections, partly due to the large reaction Q-values and high ground state spins and isospins of the radioactive ion beam. My contributions to the thesis project include: (1) building the RIB facility based on an existing solenoid, target chambers, and silicon detectors; (2) calculating and experimentally testing the optical properties of the solenoid; (3) determining the optimal conditions for production of high-purity radioactive beams; (4) making thin C, $\sp{13}$CH$\sb2$, CD$\sb2$, and TiD$\sb2$ foil targets for bombardment with RIBs; (5) collecting and analyzing RIB data to obtain cross sections; (6) analyzing the results with nuclear reaction models.