Focusing and reflectivity properties of a parallel double bent crystal (+n,-m) setting

International Workshop on Neutron Optics and Detectors

Mikula, P.^1 ; Vrána, M.^1 ; Pilch, J.^1 ; Šaroun, J.^1 ; Seong, B.S.^2 ; Woo, C.^2 ; Em, V.^3

Nuclear Physics Institute ASCR, V.v.i., 25068 Rez, Czech Republic^1

Neutron Science Division, Korea Atomic Energy Research Institute, 1045 Daedok daero, Yuseong-gu, 305-353, Daejeon, Korea, Republic of^2

National Research Centre, Kurchatov Institute, Moscow, 123182, Russia^3

关键词: Bent perfect crystals;    Experimental test;    High-efficiency;    Monochromatic beam;    Monochromatic neutrons;    Neutron wavelengths;    Reflection probability;    Scattering angles;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/528/1/012003/pdf
DOI  :  10.1088/1742-6596/528/1/012003

来源: IOP

【 摘 要 】

After preliminary results obtained and published recently [1], in our contribution focusing and reflectivity properties of the dispersive double bent-crystal arrangement are presented in much more detail. It has been found that two different bent perfect crystals in (+n,-m) setting can be good candidates for high efficiency neutron microfocusing as well as high-resolution monochromatisation. Due to the (+n,-m) setting of two different bent perfect crystals, a high resolution is expected in both Δ(2θ (2θ is the scattering angle) as well as Δλ/λ(λ is the neutron wavelength). Experimental tests were carried out with the setting employing the bent Si(111) slab and Si(220)-sandwich, which contained either one, or two or four 1.3 mm thin simply stacked slabs. Thanks to a high reflection probability of both bent elements and an easy manipulation with the curvature of the Si(220)-sandwich, an excellently focused intensive monochromatic beam of the width from one to several millimetres was obtained. The properties of the double bent-crystal setting were studied in Rez at the neutron optics diffractometer for the neutron wavelength of 0.162 nm and for various thicknesses and curvatures of the Si(220)-sandwich. It has been also found that besides an excellent focusing and reflectivity properties of the dispersive double bent-crystal setting the obtained monochromatic neutron current is sufficiently high for standard high-resolution diffraction experiments even at the medium power research reactor.