Targeted Alpha Therapy (TAT) offers a promising approach to treat cancer, particularly micrometastases, by utilizing the short range and high linear energy transfer of alpha particles emitted by radionuclides. 211At (half-life 7.2h) is one of the promising alpha emitters (only one alpha emitted during decay) that has been identified for nuclear medicine applications. It belongs to the halogen family and shares chemical properties with iodine, an element used for imaging (123I, 124I and 131I) and also widely used to treat thyroid cancer (131I). This chemical similarity enables the use of Iodine as an analogue for biodistribution and dosimetry studies while using 211At for treatment in a theranostic approach. In this study, an alpha beam accelerated by SPIRAL2, was used to produce 211At via the reaction 209Bi(α, 2n)211At on the NFS beam line. The production cross section of 211At increases with increasing alpha energy up to 31 MeV. However, above 28.6 MeV, the production of 210At occurs via the 209Bi(α, 3n)210At reaction. 210At decays to 210Po, a highly toxic alpha-emitting radionuclide with a half-life of 138.3 days which cannot be separated chemically. Therefore, it is crucial to have a thorough understanding of the rise in 210At production to optimize the generation of 211At while minimizing the production of 210At To achieve this, 209Bi targets were irradiated at various alpha beam energies between 28 to 31 MeV with high precision thanks to the characteristics of SPIRAL2 accelerator and 210,211At cross sections were measured by using γ-ray spectroscopy. The incident particle flux was monitored using an instrumented Faraday cup. This flux measurement combined with the number of detected γ-rays allowed to determine the production cross sections of 210,211At as a function of energy. The results are in good agreement with experimental values recommended by the International Atomic Energy Agency (IAEA) for 211At and provide supplemental data for 210At between 28.6 and 31 MeV. The data collected in this study will help optimize the energy range of interest for the production of 211At and give 211At its rightful place as a radionuclide for TAT.

GANIL Grand Accélérateur National d'Ions Lourds CEA DSM CNRS IN2P3 Boulevard H Becquerel Caen 14076 France

Nuclear Physics Institute CAS Řež 25068 Czech Republic

SUBATECH Nantes Université IMT Atlantique CNRS IN2P3 3 Rue Alfred Kastler Nantes 44300 France

SUBATECH Nantes Université IMT Atlantique CNRS IN2P3 3 Rue Alfred Kastler Nantes 44300 France; GIP ARRONAX 1 rue Aronnax Saint Herblain 44817 France

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