Speaker
Description
The European Spallation Source (ESS), which is currently under construction in Lund, Sweden, will be the most powerful pulsed neutron source in the world. A design study project named HighNESS is dedicated to develop a second neutron source at ESS that compared to the first source, located above the spallation target and designed for high cold and thermal brightness, provides higher intensity cold neutrons, very cold neutrons (VCN) and ultra cold neutrons (UCN) [1]. This work carried out within the HighNESS project presents the Monte-Carlo simulations of cold neutron transmission measurements of clathrate hydrates as potential moderator candidates [2] and graphite compounds as reflector materials. The Monte-Carlo simulations are performed by using the neutron transport codes OpenMC [3] and McStas [4], with the neutron scattering kernels prepared by the toolkit NCrystal [5, 6, 7] developed in the project. The scattering kernels of clathrate hydrates and graphite compounds are generated thanks to the phonon density of states obtained by density functional theory (DFT) calculations. The simulated results including neutron scattering cross sections, scattering kernels and diffraction patterns are further validated by comparing with the transmission measurements performed at Institut Laue-Langevin (ILL) and Paul Scherrer Institute (PSI).
References
[1] V Santoro, KH Andersen, M Bernasconi, M Bertelsen, Y Beßler, D Campi, V Czamler, DD Di Julio, E Diane, K Dunne, et al. Development of a high intensity neutron source at the european spallation source: The highness project. arXiv preprint arXiv:2204.04051, 2022.
[2] Oliver Zimmer. Neutron conversion and cascaded cooling in paramagnetic systems for a high-flux source of very cold neutrons. Phys. Rev. C, 93:035503, Mar 2016.
[3] Paul K. Romano, Nicholas E. Horelik, Bryan R. Herman, Adam G. Nelson, Benoit Forget, and Kord Smith. Openmc: A state-of-the-art monte carlo code for research and development. Annals of Nuclear Energy, 82:90–97, 2015. Joint International Conference on Supercomputing in Nuclear Applications and Monte Carlo 2013, SNA + MC 2013. Pluri- and Trans-disciplinarity, Towards New Modeling and Numerical Simulation Paradigms.
[4] P. K. Willendrup and K. Lefmann. Mcstas (i): Introduction, use, and basic principles for ray-tracing simulations. 2020.
[5] X.-X. Cai, T. Kittelmann, E. Klinkby, and J.I. M ́arquez Dami ́an. Rejection-based sampling of inelastic neutron scattering. Journal of Computational Physics, 380:400–407, 2019.
[6] X.-X. Cai and T. Kittelmann. Ncrystal: A library for thermal neutron transport. Computer Physics Communications, 246:106851, 2020.
[7] T. Kittelmann and X.-X. Cai. Elastic neutron scattering models for ncrystal. Computer Physics Com- munications, 267:108082, 2021.
