Simulations

The Neutron Optics (NOP) group’s activities include a wide range of numerical work, in the form of computer simulations.

A big part of NOP's work includes the use of two Monte-Carlo codes (McStas and MCNP) to perform calculations on a variety of different topics. The ray-tracing code McStas is used for: i) design and optimization of neutron lenses for various instruments and experimental set-ups. ii) Development of components (‘plugins’) for the McStas software itself, such as components for neutron lenses’ simulations, gravity component for neutron guides, etc. iii) Performing virtual experiments to accommodate the designing and operational needs of existing and upcoming experimental set-ups at PSI.

The neutron transport code MCNPX has been extensively used for shielding calculations related to the ESS project, and PSI beamlines and instruments. MCNP has also been used to simulate the behavior of certain materials (sapphire, silicon) as neutron filters. Furthermore, a coupled version of the two software (on whose development NOP has contributed extensively), has been used to perform simulations on the effectiveness of sapphire crystals as fast neutron filters.

An effort to couple SINQ's instrument control system with simulation environments has lead to the development of the Virtual McStas DMC Diffractometer

Focusing Neutron Lens Animation: Animation of simulated intensity distribution at increasing distance (0.2-0.6m) from a focusing supermirror lens. The still image above represents the intensity distribution at the focal point, located at 0.4m from the lens's exit. The simulations were performed with the monte carlo ray-tracing software McStas.
Focus-Defocus Neutron Lens System Animation Animation of simulated intensity distribution at increasing distance (0.3-2.0m) from a focus/defocus two-lens system. The still image represents the intensity distribution at 0.3m after the second (defocusing) lens's exit. The simulations were performed with the monte carlo ray-tracing software McStas.
Shielding calculations for the triple axis spectrometer EIGER at SINQ. The simulations were performed with the monte carlo software MCNP.
Calculations of SINQ's thermal flux distribution. The simulations were performed with the monte carlo software MCNP.
Simulations of a coupled 2-lens neutron focusing system for the DMC powder diffractometer at SINQ. The image on the left shows a schematic of the DMC instrument components from monochromator to detector. The image on the right shows a zoom-in on the 20lens system. The simulations were performed with the monte carlo ray-tracing software McStas.