Recent progress in the development of concave Fresnel lenses for neutrons

The performance of a Fresnel-type compound refractive lens for focusing cold neutrons was evaluated. The lens consists of 44 pieces of compound Fresnel-type refractive lenses made of MgF₂ single crystals. The intensity profile of the diffracted neutrons measured over the wavelengths of 9-14 Å was compared with the results of numerical simulations. Good neutron transmission of 0.85 for 9 Å neutrons and a focal length of 3.4 m for 16 Å neutrons were achieved.