Effect of Particle Sizes on the Efficiency of Fluorinated Nanodiamond Neutron Reflectors

Aleksander Aleksenskii (1) , Marcus Bleuel (2) , Alexei Bosak (3) , Alexandra Chumakova (3) , Artur Dideikin (1) , Marc Dubois (4) , Ekaterina Korobkina (5) , Egor Lychagin (6) , Alexei Muzychka (6) , Grigory Nekhaev (6) , Valery Nesvizhevsky (7) , Alexander Nezvanov (6) , Ralf Schweins (7) , Alexander Shvidchenko (1) , Alexander Strelkov (6) , Kylyshbek Turlybekuly (6) , Alexander Vul’ (1) , Kirill Zhernenkov (6)

1 A.F. Ioffe Physical-Technical Institute
2 NIST - National Institute of Standards and Technology [Gaithersburg]
3 ESRF - European Synchrotron Radiation Facility [Grenoble]
4 ICCF - Institut de Chimie de Clermont-Ferrand
5 NC State - North Carolina State University [Raleigh]
6 FLNP - Frank Laboratory of Neutron Physics [Dubna]
7 ILL - Institut Laue-Langevin

Over a decade ago, it was confirmed that detonation nanodiamond (DND) powders reflect very cold neutrons (VCNs) diffusively at any incidence angle and that they reflect cold neutrons quasi-specularly at small incidence angles. In the present publication, we report the results of a study on the effect of particle sizes on the overall efficiency of neutron reflectors made of DNDs. To perform this study, we separated, by centrifugation, the fraction of finer DND nanoparticles (which are referred to as S-DNDs here) from a broad initial size distribution and experimentally and theoretically compared the performance of such a neutron reflector with that from deagglomerated fluorinated DNDs (DF-DNDs). Typical commercially available DNDs with the size of ~4.3 nm are close to the optimum for VCNs with a typical velocity of ~50 m/s, while smaller and larger DNDs are more efficient for faster and slower VCN velocities, respectively. Simulations show that, for a realistic reflector geometry, the replacement of DF-DNDs (a reflector with the best achieved performance) by S-DNDs (with smaller size DNDs) increases the neutron albedo in the velocity range above ~60 m/s. This increase in the albedo results in an increase in the density of faster VCNs in such a reflector cavity of up to ~25% as well as an increase in the upper boundary of the velocities of efficient VCN reflection.

Domaines: Chimie

Aleksander Aleksenskii, Marcus Bleuel, Alexei Bosak, Alexandra Chumakova, Artur Dideikin, et al.. Effect of Particle Sizes on the Efficiency of Fluorinated Nanodiamond Neutron Reflectors. Nanomaterials, 2021, 11 (11), pp.3067. ⟨10.3390/nano11113067⟩. ⟨hal-03542484⟩