Evidence for long-range fission fragments induced by irradiation with electrons

In search of natural superheavy elements, long-range fission fragments penetrating up to 73 μm of mylar were observed, when thick metallic foils of U, Pb and W, covered with six mylar foils were irradiated with 550 MeV or 1300 MeV electron beams. The cross section is of the order of 10⁻³⁰ cm². The effect is produced in natural U, Pb, W and similarly in mass separated ²⁰⁸Pb and ¹⁸⁶W isotopes — not by fission of a superheavy element.