Bi-spectral beam extraction in combination with a focusing feeder

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Vol. 704; pp. 68 - 75
• Main Authors: Zendler, C., Lieutenant, K., Nekrassov, D., Cussen, L.D., Strobl, M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 11.03.2013
• Subjects: Beams (radiation); Bi-spectral beam extraction; Design engineering; European Spallation Source; Extraction; Feeders; Focusing; Moderators; Multi-spectral beam extraction; Neutron instrumentation; Particle physics; Supermirror; VITESS; Wavelengths; European Spallation Source; VITESS; Multi-spectral beam extraction; Neutron instrumentation; Bi-spectral beam extraction; Supermirror
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2012.11.180

Bi-spectral beam extraction combines neutrons from two different kinds of moderators into one beamline, expanding the spectral range and thereby the utilization of an instrument. This idea can be realized by a mirror that reflects long wavelength neutrons from an off-axis colder moderator into a neutron guide aligned with another moderator emitting neutrons with shorter wavelengths which will be transmitted through the mirror. The mirror used in such systems is typically several meters long, which is a severe disadvantage because it reduces the possible length of a focusing device in design concepts requiring a narrow beam at a short distance from the source, as used in many instruments under development for the planned European Spallation Source (ESS). We propose a shortened extraction system consisting of several mirrors and show that such an extraction system is better suited for combination with a feeder in an eye of the needle design, illustrated here in the context of a possible ESS imaging beamline.