High-precision branching-ratio measurement for the superallowed Fermi $\beta^+$ emitter 18Ne

Abstract : Through obseravation of the spectra of $\beta$-delayed $\gamma$-rays, the branching ratio of the superllowed Fermi transition has be determined to be (7.70(21)%) ± 2.7% precision. In this work we will determine this branching ratio for at the level of 0.2%, and significantly improve the precision on the half-life to 0.03% to establish the 18Ne ft value at a comparable level of precision to the 13 wellknown cases. This result will assess the relative accuracy of the ISB shell-structure enhancement near the N = 8 shell closure and provide important information on the validity and accuracy of recent ISB calculations.