Quenching and Channeling of Nuclear Recoils in NaI[Tl]: Implications for Dark Matter Searches

摘要

A new experimental evaluation of the quenching factor for nuclear recoils inNaI[Tl] is described. Systematics affecting previous measurements are addressedby careful characterization of the emission spectrum of the neutron source, useof a small scintillator coupled to an ultra-bialkali high quantum efficiencyphotomultiplier, and evaluation of non-linearities in the electron recoilresponse via Compton scattering. A trend towards a rapidly diminishingquenching factor with decreasing sodium recoil energy is revealed.Additionally, no evidence for crystal lattice channeling of low-energyrecoiling ions is found in a scintillator of known crystallographicorientation. A discussion on how these findings affect dark matter searchesemploying NaI[Tl] (e.g., DAMA/LIBRA) is offered.