Nickel-backed Bi targets for the production of 211At

Abstract

To support clinical trials for cancer therapy with radiotherapeutic isotopes in the United States reliable sources of adequate quantities of several such isotopes, especially of alpha emitters such as 211At, are a high priority of the DOE Isotopes Program. We have recently tested an alternative reaction, 209Bi(6Li, 4n)211Rn (which decays to 211At) with a 42 MeV 6Li beam from the ATLAS superconducting linac. This latter reaction has the advantage that radon gas is easy to extract and the 14.6-h 211Rn half-life allows more time for transport to the therapy facility. The Bi targets were prepared on a Ni backing as these elements have similar coefficients of thermal expansion, minimizing the chance of target delamination. Helium gas flowed between a thin window and the target to transport the 211Rn it to a charcoal trap. The goal was to develop a method for continuous production and collection of 211At that does not require dissolving the target following each production run. Details of the Bi target production and performance is presented as well as some initial experimental results.