Application of a total absorption detector to Qβ determination without the knowledge of the decay scheme

For Qβ determination, we have developed a total absorption detector that can detect almost all radiation from the radioactive nuclei. The estimated efficiency is more than two orders of magnitude larger than those of Ge or Si detectors. The Qβ of 151Ce in the fission products of 235U was successfully determined to be 5.27(20) MeV using an on-line mass-separator for the first time. We have proposed the possibility of determining Qβ up to about 10 MeV using a total absorption detector without the knowledge of the decay scheme.