Physicists at Japan`s KEK Wako Nuclear Science Center discovered a previously unknown isotope of uranium. with atomic number 92 and mass number 241, i.e. uranium-241.
In pursuit of finding next magic number nuclei after lead-82, the researchers accelerated Uranium-238 nuclei into Plutonim-198 nuclei at KEK isotope separation system. The resulting fragments contained different isotopes. This is how they identified U-241 and measured the mass of its nucleus.
Numbers such as 2,8,20,28,50,82,126 are recognized as “magic numbers “by physicists. As such numbers of protons and neutrons in a full shell forms highly stable nuclei.
Read more on how particles are accelerated at Large hadron collider