Recoil-beta tagging: A novel technique for studying proton-drip-line nuclei

Tagging with charged particles and γγ-rays at the focal plane of recoil separators has proven, over the last two decades, to be a very powerful tool for the identification of excited states in exotic nuclei produced with very low cross-sections. One of the key areas so far unexplored in terms of the tagging methodology has been performing correlations with ββ-particles at the focal plane of a recoil separator. A new technique entitled Recoil-Beta Tagging (RBT) has been developed, this technique exploits the unusual properties of Fermi super-allowed ββ emitters, which have both a short half-life (∼100ms) and high β+β+-endpoint energy. Correlating with such ββ-particles using a double-sided silicon strip detector and planar germanium detector as an effective ΔE–EΔE–E telescope for high-energy positrons has allowed a proof-of-principle of this technique to be carried out, by cleanly identifying excited states in the proton-drip-line nucleus, 74Rb.