Systematic study on the performance of elliptic focusing neutron guides
2016 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 808, 101-108 p.Article in journal (Refereed) PublishedText
In neutron scattering experiments there is an increasing trend towards the study of smaller volume samples, which make the use of focusing optics more important. Focusing guide geometries based on conic-sections, such as those with parabolic and elliptic shapes, have been extensively used in both recently built neutron instruments and upgrades of existing hardware. A large fraction of proposed instruments at the European Spallation Source feature the requirement of good performance when measuring on small samples. The optimised design of a focusing system comes after time consuming Monte-Carlo (MC) simulations. Therefore, in order to help reduce the time needed to design such focusing systems, it is necessary to study systematically the performance of focusing guides. In the present work, we perform a theoretical analysis of the focusing properties of neutron beams, and validate them using a combination of Monte-Carlo simulations and Particle Swarm Optimisations (PS0s), where there is a close correspondence between the maximum divergence of the beam and the shape of the guide. The analytical results show that two limits can be considered, which bound a range of conic section shapes that provide optimum performance. Finally, we analyse a more realistic guide example and we give an assessment of the importance of the contribution from multiple reflections in different systems.
Place, publisher, year, edition, pages
2016. Vol. 808, 101-108 p.
Neutron guides, Focusing optics, Monte-Carlo simulations, Numerical optimisation
Accelerator Physics and Instrumentation
IdentifiersURN: urn:nbn:se:uu:diva-274414DOI: 10.1016/j.nima.2015.11.057ISI: 000367095600013OAI: oai:DiVA.org:uu-274414DiVA: diva2:897560