Simultaneous diffraction:<i>Umweganregung</i>peaks in the case of a vibrating single crystal

Mikula, P.; Michalec, R.; Vrána, M.; Va’vra, J.

doi:10.1107/s056773947900214x

Cited by 16 publications

(6 citation statements)

References 12 publications

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“…However, it is only in the case of elastically deformed perfect single crystals that very strong MBR effects, consisting of one or more double-diffraction processes, have been observed. About three decades ago, we observed that MBR effects can be strongly amplified by ultrasonic vibrations and the related intensity can be more than one order of magnitude higher than the intensity related to the allowed reflection of a perfect nondeformed crystal (Mikula et al, 1979(Mikula et al, , 1980Vrá na et al, 1981). Moreover, some possible exploitation of the MBR effects was predicted (Mikula et al, 1982).…”

Section: Introductionmentioning

confidence: 95%

Experimental studies of dispersive double reflections excited in cylindrically bent perfect-crystal slabs at a constant neutron wavelength

et al. 2012

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Multiple Bragg reflections (MBRs), which can be realized in a bent perfect crystal (BPC) slab and are mutually in dispersive diffraction geometry, provide a monochromatic beam of excellent resolution. After identifying many MBR effects in a BPC Si crystal by using the method of θ–2θD scanning, we have turned our attention to the study of selected effects using the method of azimuthal rotation of the crystal lattice around the scattering vector of the primary reflection for a fixed chosen wavelength. In this paper, several azimuthal scans with the intention of possible practical exploitation for very high resolution diffractometry are presented.

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Section: Introductionmentioning

confidence: 95%

Experimental studies of dispersive double reflections excited in cylindrically bent perfect-crystal slabs at a constant neutron wavelength

et al. 2012

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“…The Japan Society of Mechanical Engineers NII-Electronic Library Service ATEM'03, JSME-MMD, Sep. [10][11][12]2003 Next, a similar beam profile test was carried out at 2θ =34 o when using two Si slabs: one with the main face parallel to the planes (111) for symmetric reflection geometry and the other one with (11-1) planes at Ψ=22 o for strongly asymmetric transmission geometry. The obtained results are shown in Figs.…”

Section: Os04w0288mentioning

confidence: 99%

“…For X-rays, the positive umweg-diffraction peaks were first observed by Renninger [8] and Moon and Shull for neutrons in mosaic crystals [9] (many other related references can be found in the book [10]). However, it has been found that strong multiple reflection effects resulting in Umweganregung can be also in elastically deformed perfect crystals [11][12][13][14]. In the simplest case of the umweg-effect, a particular weak or forbidden primary reflection is strengthened by a successive cooperation of the two allowed reflections (secondary and tertiary).…”

Section: Multiple Reflection Umweganregung Monochromatormentioning

confidence: 99%

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OS04W0288 New monochromator performances based on Bragg diffraction optics for high-resolution neutron strain/stress diffractometers

Mikula

Vrána

Wagner

et al. 2003

ATEM

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Two unconventional high-resolution monochromator performances using Bragg diffraction optics and based on cylindrically bent perfect crystals which have been recently tested with the aim of their efficient employment in strain diffractometers are reviewed. It has been found that the optimized diffractometer arrangements employing such monochromators provide good luminosity and a high resolution (FWHM of the instrumental ∆d/d -profile can be about 2.7x10 -3 in the double-crystal case or less than 8x10 -4 in the Umweganregung case) in the vicinity of usually used 2θ S ≈ 90 o . Presented results demonstrate their experimental abilities for powder diffraction, namely for residual strain/stress measurements. Due to the unique resolution and good luminosity achieved, besides the macrostrain scanning, the presented performances also qualified for possible microstrain/stress studies by an analysis of the diffraction profiles.

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“…For X-rays, the positive MBR peaks were first observed by Renninger (1937). However, the situation is quite different in the case of neutron diffraction by elastically deformed perfect crystals (Mikula et al, 1979(Mikula et al, , 1982(Mikula et al, , 2006(Mikula et al, , 2012Vrá na et al, 1981). The first principal theoretical investigation in this field was performed by Ewald (1937).…”

Section: Introductionmentioning

confidence: 99%

Time-of-flight studies of multiple Bragg reflections in cylindrically bent perfect crystals

et al. 2012

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Multiple Bragg reflections (MBRs) realized in a bent perfect crystal (BPC) slab by sets of different lattice planes behave differently from the case of perfect nondeformed or mosaic crystals. Because of elastic bending (homogeneous deformation), individual sets of lattice planes are mutually in dispersive diffraction geometry and the kinematical approach can be applied on this MBR process. The elastic deformation produced by the cylindrical bending can enormously strengthen the MBR effects, which can then be investigated even at small neutron sources. By using neutron diffraction and the time‐of‐flight method, carried out at the 45 MeV linac‐based pulsed cold neutron source at Hokkaido University, it has been demonstrated that when setting the BPC slabs in the symmetric transmission geometry many strong MBRs accompanying forbidden Si(222) or Si(002) reflections can be observed. The advantage of the time‐of‐flight method consists in the fact that it is possible to observe not only primary MBRs related to the basic forbidden reflections but also their higher orders, which could be easily separated in the time‐of‐flight spectra.

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Simultaneous diffraction:Umweganregungpeaks in the case of a vibrating single crystal

Cited by 16 publications

References 12 publications

Experimental studies of dispersive double reflections excited in cylindrically bent perfect-crystal slabs at a constant neutron wavelength

Experimental studies of dispersive double reflections excited in cylindrically bent perfect-crystal slabs at a constant neutron wavelength

OS04W0288 New monochromator performances based on Bragg diffraction optics for high-resolution neutron strain/stress diffractometers

Time-of-flight studies of multiple Bragg reflections in cylindrically bent perfect crystals

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