Development of a horizontally and vertically focused neutron monochromator using stacked elastically bent Si single crystals

A horizontally and vertically focused monochromator has been developed for the 4-axis neutron diffractometer applied for a single crystal structure analysis. Silicon perfect single crystals are bent elastically in order to focus monochromatic neutrons horizontally. The monochromatic beam can also be focused vertically by stacking the horizontally bent crystals. Tilting motion of each stacked bent crystal is controlled independently by stepping pulse motors for optimizing and reproducing perfectly the vertical focusing at the sample position. The intensity of neutrons with a 1.57 إ wavelength monochromatized by the new monochromator increases remarkably, and is comparable to that of pyrolytic graphite monochromator with a 2.44 إ wavelength. The high tunability of the doubly focusing system established in the present study can be adopted easily when obtaining the shorter wavelength of neutrons.