A novel pyrolytic-graphite-on-silicon device for neutron monochromatization

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Accelerators, spectrometers, detectors and associated equipment, 2023-03, Vol.1048, p.168012, Article 168012
• Main Authors: Freund, Andreas K., Chen, Changyong, Crosby, Mike, Farkas, Gergely, Kozak, Brian, Krencisz, Dawn, Liu, Xiang, Mikula, Pavol
• Format: Article
• Language: English
• Subjects: Bent perfect crystals; Dual focusing systems; Neutron monochromators; Pyrolytic graphite
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2023.168012

In the quest of improving neutron scattering instrumentation a new style of dynamically focusing monochromator is proposed where highly oriented pyrolytic graphite (HOPG) crystals are bonded on bendable single crystal silicon blades. This development followed a study of the elastic limit of HOPG that revealed serious technical difficulties when bending thin blades of this very fragile material to achieve dynamical focusing. The critical breakage thickness was found to be less than 0.1 mm for a radius of curvature of 1.5 m. The novel PG-on-Si (POSI) concept replaces the linear arrays of individually oriented HOPG pieces employed in existing devices. It facilitates the integration of two separate HOPG and Si monochromators into a single device. Mechanical tests, X-ray and neutron diffraction studies of the POSI system confirmed the feasibility of these single and dual monochromator designs that feature high performance and augmented functionality at reduced complexity and cost.