High-precision spontaneous fission branching-ratio measurements for 240,242Pu and 252Cf isotopes

We report here very precise measurements of the spontaneous fission branching ratio for the $^{240,242}\mathrm{Pu}$ and $^{252}\mathrm{Cf}$ isotopes, performed with a new kind of active scintillating target. It is shown that the method itself leads to unprecedentedly small uncertainties, and that these uncertainties are negligible compared to uncertainties on the isotopic content of the sample. Besides this capability we discuss the possibility to use this kind of detector for the systematic study of charged particle radioactivity, i.e., spontaneous fission, \ensuremath{\alpha} decay, and heavy-ion radioactivity.