Multilayer Neutron Monochromator And Polarizer Of Double Mirror Type

Abstract

A multilayer neutron monochromator and polarizer of double mirror type have been developed using a successive double reflection by two multilayer mirror deposited on a Si substrate. The multilayer mirrors have a supermirror-type thickness distribution of bilayers. The monochromator (polarizer) plays simultaneously the roles of a monochromator (polarizer), a collimator and a beam bender through a successive double reflection by the two mirrors. The double reflection brings a low contamination of higher order Bragg reflections. For the monochromator several multilayer mirrors deposited on Si substrates are assembled in the shape of Soller slit to cover a wide neutron beam. The multilayer mirrors for the monochromator are fabricated by depositing Ni and Ti. The bilayer thickness distribution is supermirror-type with the mean thickness of 150 Å and the width of the distribution of 20%. The monochromator provides a monochromatic beam of 5 Å with wavelength resolution of 20%, divergent angle of 1/300 rad and bent angle of 1/15 rad. Peak reflectivity of the monochromator is observed to be 40% for a incident beam with a divergence of 1/240 rad. Available beam size is about 5 cm x 1 cm in a Soller-slit type with 12 sheets of the multilayer mirrors. FeCo-Ti multilayer polarizer and FeCo -V multilayer analyzer have the similar characteristics with the Ni-Ti multilayer monochromator. The polarizing efficiency is about 90%.