6LiF:ZnS(Ag) Mixture Optimization for a Highly Efficient Ultrathin Cold Neutron Detector

We report the optimization of
⁶
LiF:ZnS(Ag) scintillator mixtures for an ultrathin (<;2 mm), highly efficient cold neutron detector. Preliminary results with early prototypes demonstrated excellent absorption for 3.62-meV (4.75-Å wavelength) neutrons but mediocre neutron sensitivity (≈ 30%). Our optimization took the form of exploring the weight ratios of neutron converter, phosphor, and binder to promote high neutron capture probability and light transport within the medium. We characterized a series of
⁶
LiF:ZnS(Ag):binder mixtures for neutron absorption, light yield, and light transmission properties. In the process, we determined the optimal configuration for our requirements of millimeter thickness and cold neutron energy. Optimized prototypes exhibit excellent absorption and demonstrate neutron sensitivities of above 85% for 3.27-meV neutrons and gamma ray rejection ratios approaching 10
^-7
.