Maximizing Production of Radioisotopes in a Cyclotron

The radioisotopes Mn⁵⁴, I¹²⁵, and I¹³⁰ were produced at higher rates and at lower cost when targets of isotopically enriched Cr⁵⁴, Te¹²⁵, and Te¹³⁰ were bombarded with protons in the ORNL 86-Inch Cyclotron. The product isotopes were carrier-free and also relatively free of undesired radioisotopes. The use of enriched isotopes as cyclotron targets is economically attractive when the target material can be recovered and reused. To obtain the maximum production rate for radioisotopes in a cyclotron, both the usable beam power and the excitation function of the nuclear reaction must be considered; in some cases the maximum rate is achieved at a reduced energy. With the ORNL 86-Inch Cyclotron, (p, n) reaction production rates were increased by a factor of 1.7 by decreasing the proton energy from 22 to 18 Mev and doubling the output current. Methods of reducing the energy below the maximum design value are discussed.