L. Sedláková

Neutron diffraction effects due to the lattice displacement of a vibrating quartz single crystal

The time modulation of neutrons diffracted by a quartz single crystal is investigated. The experimental results agree with the aberration and with the Doppler effect caused during neutron diffraction by vibrations of a single crystal.

Secondary reflexions of neutrons diffracted by a single-crystal bar vibrating at high frequency

Diffraction of neutrons by a longitudinally vibrating quartz single-crystal bar was investigated for thicknesses of 3 and 13 mm. The 1st, 3rd and 5th harmonic frequencies were excited in the bar. The observed increase of the integrated intensity of diffracted neutrons as a function of the vibration amplitude of longitudinal vibrations of the quartz bar is compared with that calculated from an approximate theory considering the possibility of secondary reflexions of neutrons during their flight across the sample.

Applications of methods and results of neutron diffraction by vibrating single crystals

Abstract In this paper possibilities of application of phenomena observed in the course of investigations concerning diffraction of neutrons by vibrating lattices of single crystals are described.

A vibrating perfect crystal assumed to be a real one

A generalized formula for the integrated intensity of neutrons diffracted by a vibrating perfect crystal is derived on the basis of the lamella structure with the symbols of Zachariasens general theory. The formula is introduced together with new experimental data for diffraction from a longitudinally vibrating quartz single crystal.

Some experiments of neutron diffraction by flexurally vibrating and elastically bent Si single crystals

Abstract In this paper the neutron diffraction by lattices of Si single crystals for the sake of monochromator design was investigated and, for this purpose, it was performed on flexurally vibrating Si perfect single crystals and - for comparison - on a statically bent sample of Si. A significant increase of the integrated intensity of diffracted neutrons in the symmetric Bragg reflection condition was observed and measured in case of a vibrating Si crystal in dependence on the periodic elastic stress or displacement, in the case of the elastically bent crystal as a function of the radius of curvature.

Effects of thickness-shear vibrations on neutron diffraction by quartz single crystals

The influence of thickness-shear vibrations on the process of neutron diffraction by the lattice of quartz single crystals is investigated. Qualitative interpretation of the experimental data is carried out on the basis of the dynamical theory of neutron diffraction by vibrating single crystals.

Bent silicon as a short-wavelength monochromator

Abstract The reflectivity of an elastically bent perfect Si crystal was tested at shorter wavelengths (λ A ) . Using a TOF method the investigations were performed for Si(311) and Si(331) reflections at the wavelengths 0.60 and 0.45A, respectively. Good agreement between the experimental and predicted theoretical values makes bent Si crystals an interesting possibility for monochromators for hot neutrons.

Phase shift in the time spectrum of neutrons diffracted by a vibrating single crystal

Abstract In this paper the time modulation of neutrons diffracted by a longitudinally vibrating bar shaped quartz single crystal was investigated. The phase shift of the neutron time spectrum with respect to the absolute value of the sinusoidally varying strain of the vibrating sample was observed.

Neutron interferometry at a pulsed source

Abstract A compact setup providing vibration damping support as well as thermal shielding for a classical LLL interferometer was developed and installed at the IBR-2 pulsed reactor at JINR Dubna. Despite the low incident neutron flux successful experiments were performed with two different LLL-type interferometer crystals and simultaneous observation of the interference patterns on two reflection orders was demonstrated. This first experience leads to the conclusion that routine experiments in the multi-wavelength regime are feasible, but a careful optimization of the setup regarding the opposing demands on TOF resolution, incident flux and background would be desirable to compensate at least partially for the rapid decrease of diffracted intensity at higher reflection orders.

Determination of the neutron scattering length of208Pb

The neutron coherent scattering length bc=9.26(13) fm of the lead isotope208Pb was determined by neutron interferometry.