Measurement Of Cross Sections For The 232Th (P, 4n) 229Pa Reaction At Low Proton Energies

The alpha-emitters Ac-225 and Bi-213 are of great interest for alpha-radioimmunotherapy which uses radioisotopes attached to cancer-seeking antibodies to efficiently treat various types of cancers. Both radioisotopes are daughters of the long-lived Th-229 (t(1/2) = 7880y). Th-229 can be produced by proton irradiation of Th-232 and Th-230, either directly or through production of isobars that beta-decay into Th-229. To obtain excitation functions, Th-232 and Th-230 have been irradiated at the On-Line Test Facility at the Holifield Radioactive Ion Beam Facility at ORNL. Benchmark tests conducted with Cu and Ni foils show very good agreement with literature results. The experiments with thorium targets were focused on the production of Pa-229 and its daughter Ac-225 from both Th-232 and Th-230. Differential cross-sections for production of Pa-229 and other Pa isotopes have been obtained.