In some embodiments, the neutron source has a source activity of at least 1E15 Bq. In some embodiments, the neutron source has a source activity of at least 14 MeV. In some embodiments, the neutron source is Californium-252. In some embodiments, the neutron target comprises nickel and has a thickness of 0.01-0.06 mm. In some embodiments, the proton target comprises RaCl₂ and has a thickness of 4.5-5.5 mm.

Another aspect of the disclosure provides a method of producing Actinium-225, comprising bombarding a neutron target with neutrons from a neutron source to produce a proton beam, wherein the neutron target comprises nickel, manganese, or iron; and bombarding a proton target with the proton beam, wherein the proton target comprises radium-226. In some embodiments, a proton energy of the proton beam is 10 MeV or higher.