Neutron Reflectivity Of Li-6-Ti Multilayer With A Ni Reflector Applied To Ucn Detector

The neutron reflectivity of a Li-6-Ti multilayer mirror with a Ni reflector at the base has been measured using a time-of-flight spectrometer and a reflectometer. The results show that the reflectivities rise to 0.5 at 560 Angstrom, which corresponds to the Ni critical wavelength, decrease to 0.2 with increasing neutron wavelength, and then rise towards unity at about 800 Angstrom. This implies that neutrons in wavelength region between 560 Angstrom and 800 A penetrate through the Li-6-Ti multilayer and are absorbed by Li-6. The application of the Li-6-Ti multilayer to a neutron converter for an ultracold neutron detector is discussed.