MONOCHROMATION AND APODIZATION WITH TI-B4C MULTILAYERS IN NEUTRON OPTICS

The apodization within B4C-Ti multilayered monochromators in the Kagan -Afanas'ev-Bormann geometry is checked experimentally. By using the ab sorption and transparency of B4C and Ti layers, respectively, this apo dization manifests itself by narrow and intense first Bragg order coup led with a very low surrounding reflectivity over a large momentum ran ge. Three ion beam sputtering multilayered monochromators, constituted by 9, 25 and 50 (20 angstrom B4C-120 angstrom Ti) bilayers, are teste d. The first Bragg order reflectivity is about 12.4%, 60.6% and 73.5%, respectively, with a corresponding bandwidth DELTAK(B)/K(B) of 10.5%, 5.6% and 4.1%, respectively, with a surrounding reflectivity smaller than 1% (left) and 1% (right). Compared to the classical Ni-Ti multila yered system, the B4C-Ti multilayered system in the Kagan-Afanas'ev-Bo rmann geometry is better from the monochromation and apodization point of view.