Abstract
Due to their large coherent scattering cross section, diamond nanoparticles (DNPs) are considered as a promising candidate material for a new neutron reflector. For investigation of scattering cross sections of packed samples, we have developed a technique for mechanical compression of DNP powder. Application of 220 MPa allowed us to increase the bulk density from 0.40 g/cm3 to 1.1 g/cm3. The differential cross sections of uncompressed and packed samples were measured using the high-intensity total diffractometer instrument NOVA at J-PARC, covering transfer wavenumbers (q) from 0.6 to 100 nm−1. The q dependence for the compressed sample agreed with the theoretical expectation derived from the Born approximation applied to homogeneous spheres with inclusion of a hard-sphere model to account for the inter-particle structure, whereas the results obtained from the powder sample disagreed. This implies that the theoretical description does not well represent the mesoscopic structure of the DNP powder sample.
Highlights
Owing to their unique properties, neutrons are widely employed as a probe for material sciences, imaging, fundamental physics and other applications
Large-angle diffusive scattering by diamond nanoparticles (DNPs) is rather inefficient for neutron velocities larger than 100 m/s, fluxes of higher-energy neutrons from a moderator can possibly be increased due to diffusive scattering under small angles
DNPs can be expected to become employed for a new neutron reflector because of their large coherent scattering cross section
Summary
Owing to their unique properties, neutrons are widely employed as a probe for material sciences, imaging, fundamental physics and other applications. Steyerl and Trustedt observed that the inhomogeneous structure of electro-graphite leads to a strong coherent enhancement of the neutron scattering cross section. They mentioned that this phenomenon lends itself for application as a neutron reflector for very slow neutrons [4]. Diamond nanoparticles (DNPs) scatter neutrons strongly due to the bulk inhomogeneity induced by the particle form factor [5,6,7,8,9]. As input for design work on neutron reflectors, we measured the differential cross sections of the powder and the compressed samples using the high-intensity total diffractometer instrument NOVA of the Material and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC) [10]
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