METHOD OF DETERMINING RELATIVE CHANGE IN INTERPLANAR DISTANCE OF PERFECT MONOCRYSTALS Russian patent published in 2010 - IPC G01N23/20 

FIELD: physics.

SUBSTANCE: collimated beam of neutrons is directed at Bragg angle onto a system of two monocrystals: the first with interplanar distance d₀ is standard and the second with interplanar distance d is the analysed monocrystal. Change in intensity of neutrons reflected from the standard crystal at Bragg angle 90° is determined using a detecting crystal with reflection coefficient of 50%. The beam is then directed into the analysed monocrystal and simultaneous fulfillment of Bragg condition is achieved at diffraction angle of 90° for the beam of neutrons reflected from the crystal in graphical planes of the standard and analysed crystals. Minimum reflection intensity from this crystal is then achieved by changing temperature of the standard crystal. The value of temperature difference between the standard and analysed crystals ΔT is determined at the minimum of the reflection curve which corresponds to change in interplanar distance of these crystals by a value Δd and, considering that angular dispersion at θ_d=90° is close to zero, relative change in interplanar distance of the analysed crystal is calculated using formula , where ξ is thermal coefficient of expansion of the standard crystal, ΔT is temperature difference between the standard and analysed crystals.

EFFECT: more accurate determination of relative change in interplanar distance of perfect monocrystals with fewer requirements for the technology of preparing specimens.

3 dwg, 1 ex