Focusing of Cold Neutrons: {{Performance}} of a Laterally Graded and Parabolically Bent Multilayer

We have designed and built a parabolically shaped reflector with a Ni/Ti-multilayer coating, graded along the length of the device. The bilayer thickness follows the varying angle of incidence to match the Bragg condition for a beam parallel to the axis of the parabola. As measurements show, this concept leads to a higher reflectivity for monochromatic neutrons compared to a conventional supermirror coating. With a reflectivity R496% we measured a gain of 5 when focusing a 8.6 mm wide beam of 0:13 divergence down to 1.6 mm. The wavelength band was 4:7 A˚ 75% and the focal point was 250 mm behind the device.     «

We have designed and built a parabolically shaped reflector with a Ni/Ti-multilayer coating, graded along the length of the device. The bilayer thickness follows the varying angle of incidence to match the Bragg condition for a beam parallel to the axis of the parabola. As measurements show, this concept leads to a higher reflectivity for monochromatic neutrons compared to a conventional supermirror coating. With a reflectivity R496% we measured a gain of 5 when focusing a 8.6 mm wide beam of 0:...     »