A successful phase space transformation chopper design for neutron backscattering spectroscopy

• DOI: 10.1063/5.0245330
• Publication Date: 2025-04-18T12:45:57Z
• Authors: Bernhard Frick; Tilo Seydel; Lambert van Eijck; Markus Appel; Jean-François Bar...; Richard Ammer; Pierre Courtois; Pascal Lachaume; Franck Lapeyre; David Bazzoli
• Keywords: Chopper; Neutron spectroscopy; Coherent backscattering

Neutron backscattering spectroscopy with sub-μeV energy resolution has profited over recent years from intensity gains enabled by a phase space transformation (PST) chopper, which is fast-moving neutron optical component first proposed Schelten and Alefeld (Internal Report No. Jül1954, KFA Jülich, 1984). Here, we present its principle, the considerations for our technical layout, related challenges, mechanical aspects, tests to graphite mosaic crystals, moving center velocity of 243 m/s in scattering plane perpendicular reciprocal lattice vector reflection. The reported crystal quality are informative other applications. Our mechanically innovative, most compact PST chopper layout proven reliability during user operation spectrometer IN16B, certain aspects design have already been adopted another spectrometer. We report relative gain measured on ILL.