Plastically deformed Ge-crystal wafers as elements for neutron focusing monochromator

Plastically deformed Ge-crystal wafers that have the cylindrical shape with a large curvature were characterized by neutron diffraction. The box-type rocking curve of Bragg reflection with the angular width of Γ_{box ~ 2}° in FWHM, which is observable in the monochromatic neutron diffraction, results in an enhancement in the angle-integrated intensity (I_θ$I_{\theta }$). Besides,I_θ$I_{\theta }$ efficiently increases by stacking such Ge wafers. In the course of white neutron diffraction, the reflected-beam width near the focus point becomes sharper than the initial beam width. Further, the dependence of the horizontal beam width on the distance between the sample and detector is quantitatively explained by taking account of the large Γ_box${\Gamma }_{\mathrm{box}}$, the small mosaic spread of η~0.1°$\mathrm{\eta ~}0.1°$, and the thickness of the wafers. On the basis of these characterizations, use of plastically deformed Ge wafers as elements for high-luminance neutron monochromator is proposed.

Keywords:  Plastically deformed Ge wafer;  Neutron monochromator crystal;  Neutron beam focus

Source: Sciencedirect

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