EVALUATION OF A MULTILAYER MIRROR AS AN OPTICAL-ELEMENT OF AN INTERFEROMETER USING A DOUBLE DIFFRACTOMETER WITH CHANNEL-CUT PERFECT CRYSTALS

The large lattice spacing of multilayer mirrors (d > 50 Angstrom) enab les us to construct interferometers for long wavelengths and good beam separation. We measured the spread in angular divergence of the Bragg reflected beam from the Ni/Ti multilayer mirror evaporated on a speci ally well-polished Si substrate using a double diffractometer with cha nnel-cut Si perfect crystal for cold neutrons (lambda = 4.7 Angstrom). The angular divergence of the reflected beam is less than 5 mu rad. T his multilayer satisfies the requirement for the neutron optical eleme nts in such interferometers.