Production of α-particle emitting 211At using 45 MeV α-beam

Among the α-particle emitting radionuclides, ²¹¹At is considered to be a promising radionuclide for targeted cancer therapy due to its decay properties. The range of alpha particles produced by the decay of ²¹¹At are less than 70 µm in water with a linear energy transfer between 100 and 130 keV µm^-1, which are about the maximum relative biological effectiveness for heavy ions. It is important to note that at the present time, only a few of cyclotrons routinely produce ²¹¹At. The direct production method is based on the nuclear reactions ²⁰⁹Bi(α,2n)²¹¹At. Production of the radionuclide ²¹¹At was carried out using the MC-50 cyclotron at the Korea Institute of Radiological and Medical Sciences (KIRAMS). To ensure high beam current, the α-beam was extracted with an initial energy of 45 MeV, which was degraded to obtain the appropriate α-beam energy. The calculations of beam energy degradation were performed utilizing the MCNPX. Alumina-baked targets were prepared by heating the bismuth metal powder onto a circular cavity in a furnace. When using an E_{α, av} of 29.17 MeV, the very small contribution of ²¹⁰At confirms the right choice of the irradiation energy to obtain a pure production of ²¹¹At isotope.