  We demonstrate a three phase-grating neutron interferometer as a robust
candidate for large area interferometry applications and characterization of
materials. This novel far-field moire technique allows for broad wavelength
acceptance and relaxed requirements related to fabrication and alignment,
circumventing the main obstacles associated with perfect crystal neutron
interferometry. Interference fringes were observed with a total interferometer
length of four meters, and the effects of an aluminum 6061 alloy sample on the
coherence of the system was examined. Experiments to measure the
autocorrelation length of samples and the universal gravitational constant are
proposed and discussed.
