Studies on a Polarized Proton Target for Reactions with Radioactive Ion Beams

Author

Juan Pablo Urrego-Blanco, University of Tennessee - Knoxville

Date of Award

8-2009

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Physics

Major Professor

Carroll R. Bingham

Committee Members

Alfredo Galindo-Uribarri, Yuri Efremenko, Witold Nazarewicz, Lawrence W. Townsend

Abstract

Over the last few years, much progress has been made towards the understanding of basic properties of nuclei with extreme neutron to proton ratios. However, the study of phenomena involving spin polarized nuclei near the drip lines remains practically unexplored. The importance of such studies lies in the fact that the most complete knowledge of the scattering matrix is obtained in reactions with polarized particles. The purpose of this dissertation was to explore the feasibility of using polarized probes in reactions with exotic nuclei. We identified areas where reactions between Radioactive Ion Beams (RIBs) and light polarized targets open a new window of opportunity to study the behavior of those nuclei. These include nuclear structure studies using elastic scattering, the investigation of isolated resonances in nuclei of interest for astrophysics, the study of weakly bound nuclei, one nucleon transfer reactions, and reaction mechanisms. Motivated by these potential applications, we developed a polarized proton target with unique capabilities to operate in reactions with heavy ions at low and intermediate energies. Protons in a plastic foil are polarized using the dynamic nuclear polarization method, which requires low temperature operation (~200 mK) and intense magnetic fields (2.5 T). The foils can be prepared using the spin coating technique, resulting in thicknesses between 100 μg/cm² and 20 mg/cm². We have demonstrated operation of the target in frozen spin mode (low magnetic field, e.g., 0.8 T), required for experiments at low energies. For experiments with fast beams the target can be operated in dynamic mode reaching polarizations of up to 30% (B=2.5 T, continuous microwave irradiation). The operational limits of the target have been explored at the Paul Scherrer Institute and at the Holifield Radioactive Ion Beam Facility using the thick target technique with ¹²C beams at 38 MeV and intensities up to 10⁷ pps, corresponding to the most intense RIBs available. The dissertation concludes with a series of recommendations for future improvements on the target systems and suggesting the use of the target to further investigate weakly bound systems.

Recommended Citation

Urrego-Blanco, Juan Pablo, "Studies on a Polarized Proton Target for Reactions with Radioactive Ion Beams. " PhD diss., University of Tennessee, 2009.
https://trace.tennessee.edu/utk_graddiss/70