Quenching factor measurements of sodium nuclear recoils in NaI:Tl determined by spectrum fitting

We have performed measurements of sodium nuclear recoils in NaI:Tl crystals, following scattering by neutrons produced a $^{7}$Li(p,n)$^{7}$Be reaction. Understanding the light output from such recoils, which is reduced relative to electrons equivalent energy quenching factor, critical interpret dark matter experiments that search for interactions. developed spectrum-fitting methodology extract factor our measurements, and report factors recoil energies between 36 401 keV. Our results agree with other recent use quasi-monoenergetic neutron sources. The new method will be applied future crystals used SABRE experiment.