Effects of ground movements on realistic guide models for the European Spallation Source

Abstract

We model the effect of ground movement, based on empirical experience, on the transport properties of long neutron guides by ray-tracing simulations. For a simple model, our results reproduce the large losses found by an earlier study, while for a more realistic engineering model of guide mounting, we find the losses to be significantly smaller. A detailed study of the guide for the cold neutron spectrometer BIFROST at the European Spallation Source shows that a realistic loss value is 7.0(5)% for wavelengths of 2.3-4.0 Å, the typical operational wavelength range of the instrument. This amount of loss does not call for mitigation by overillumination as suggested in the previous work. Our work serves to quantify the robustness of the transport properties of long neutron guides, in construction or planning at neutron facilities worldwide.

Monte Carlo simulations of the S-shaped neutron guides with asymmetric concave and convex surface coatings

“…In this sense, large vertical deformations are foreseen with a potential to interfere even in neutron guides of near-source instruments. Thus, our model analysis can be applied to guide systems present in Figure 4 of Husgard work, for instance [23]. Besides, cold neutron transportation is positively affected by the wavelength cutoff of most energetic neutrons in small-angle neutron scattering, e.g., at instrument LoKI [21].…”

“…According to Zendler and Bentley, a considerable part of the 22 designed instruments is between 75 and 100 m away from the source [22]. In this scenario, neutron guide systems, which are composed of many guide sections, might exhibit a transport efficiency decrease due to misaligning sections [23,22]. In addition, it is expected that the ESS basement foundation presents a gradual sink with time, which could systematically misalign system guide axes.…”