Abstract: A target is bombarded with high energy particles to generate a radioisotope, and the radioisotope is preferably extracted by one of the following: combusting the target in oxygen, stopping the bombardment and heating the target, or heating the target by induction. Bombardment may take place through a windowless path, and the radioisotope may be used for PET. The particles used may be deuterons or protons, and .sup.13 N may be generated. .sup.11 C may also be generated from either .sup.11 B or .sup.10 B using protons or deuterons. Combustion may be performed by induction heating and may be controlled by the quantity of oxygen available or the temperature. Combustion may be primarily confined to a surface layer and the target may be reused. The beam energy may be 2.2 MeV or less. Another general aspect includes trapping the oxides of .sup.13 N in a trap. The oxides may be converted into .sup.