Intense antineutrino source based on a lithium converter. Proposal for a promising experiment for studying oscillations

An intense electron-antineutrino source with a hard spectrum ($E^{\max}_{\tilde \nu{_e}}=13$ MeV and $\langle E_{\tilde\nu{_e}}\rangle=6.5$ MeV) can be created on the basis of the short-lived isotope $^8$Li ($\beta^-$-decay, $T_{1/2}=0.84$ s) formed via the $(n,\gamma)$ activation of $^7$Li. In contrast to a reactor antineutrino spectrum whose uncertainty is large, particularly in the high-energy region $E_{\tilde \nu{_e}}>6$ MeV, which is experimentally relevant, the lithium $\tilde \nu{_e}$ spectrum is accurately determined. The proposed accelerator-driven experimental scheme with a neutron-producing target and a lithium converter as an intense $\tilde \nu{_e}$ source is an alternative to a nuclear reactor. The required amount of high-purity $^7$Li will be reduced in many times by using the suggested heavy-water LiOD solutions. A possible experiment involving the lithium source on search for sterile neutrinos in the mass region $\Delta m^2\ge0.2\,$eV$^2$ with a very high sensitivity to mixing-angle values down to $\sin^2(2\Theta)\approx(7{-}10)\cdot10^{-4}$ at the 95% C.L. has been considered.