A new internal target system for production of (211)At on the cyclotron U-120M.

The alpha emitter (211)At is a radionuclide with good potential for use in the therapy of smaller tumours and metastases. However, limited availability of this radionuclide hinders development of this application and the research of astatine chemistry in general. In this general context we have designed and tested a new internal target system. A thin bismuth layer (3-5 microm) was evaporated onto a light target backing (7.5 g) and irradiated at 0.5-1.5 degrees angles with 29.5 MeV alpha particles beam of intensity up to 30 microA. The backing was then released from the target holder and used directly for astatine separation via dry distillation. Astatine condensed on the Teflon capillary walls was then eluted into 150-250 microl of methanol. The saturation yield was found to be ca. 400 MBq/microA, and the radionuclidic purity of (211)At acceptable for medical applications (activity ratio (210)At/(211)At<10(-3) at EOB). The overall separation yield was 65-75%.