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.