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Neutron Laue Diffraction in Perfect and Deformed Silicon Single Crystals Under Ultrasound ExcitationThe effect of ultrasound (US) on neutron Laue's diffraction is studied for perfect and deformed crystals. In a perfect crystal the oscillations of relative diffraction intensity were observed, which depend on the ultrasound wave amplitude. In a deformed crystal the ultrasound distorts the adiabatic motion of the image points along the sheets of dispersive surface. This gives rise to the diffraction intensity behavior which sharply differs from that in the perfect crystal case. The results obtained agree well with theoretical concepts. The described effects can be used for creation of US-controlled new type neutron monochromators or choppers.

The neutron Bragg diffraction on a bent silicon monocrystal excited by ultrasound was investigated. It is shown that for perfect crystal the relative diffraction intensity is proportional to the acoustic wave amplitude w. The calibration parameters between the generator voltage and acoustic wave amplitude were derived assuming w = (2.3±0.3)⋅10-2 Å/V. To explain the results, a modified Penning-Polder-Kato model was applied. In a bent crystal, owing to ultrasound, transitions between the sheets of a dispersion surface take place. This leads to various manifestations of the behaviour of the integral scattering intensity, which drastically differs from the case of a perfect crystal. The observed effects may be used for creating new types of neutron monochromators and choppers governed by the ultrasound wave amplitude as well as by the length and bending radius of the crystal.