Abstract
In this research project, we measured and analyzed the spatial distribution of neutron beam Bragg diffracted from the front- and back-faces of thin Si single crystal undergoing on ultrasound excitation. For the perfect crystal, it is shown that when the acoustic wave amplitude is increased, the front-face peak position remains unchanged and its value grows linearly. The values of ultrasound wave amplitude were determined. The back-face peak becomes asymmetric and tends to disappear. New types of Pendellosung fringes in the center of the diffraction profiles were observed at the first time. It is supposed that in the perfect crystal this effect may be due to the appearance of the new “sonic” extinction length, depending on the amplitude of the ultrasonic wave. Thus, it leads to the new interference interactions between neutron wave and ultrasonic phonons. It is established that within the framework of the dynamical theory of the neutron scattering, some asymptotic models valid for the case of Laue geometry as well as Kato’s quasi-classical approximation can be applied in the case of Bragg geometry also. Good agreement between experimental data and the theory has been obtained.
Highlights
Experiments that confirmed the correctness of theoretical considerations based on the dynamical theory of waveHow to cite this paper: Raitman, E., Gavrilov, V., Mjasischev, D., Ekmanis, Ju., Hoser, A. and Hoffmann, T. (2015) Neutron Back- and Front-Face Bragg Diffraction on a Thin Si Single Crystal Excited by Ultrasound
The purpose of this paper is to present new experimental data of the study and the neutron interactions with acoustic waves (AW) of rather small amplitude observed using the Bragg’s diffraction method from perfect thin Si single crystal
The common situation becomes more complicated for the thin crystal if we analyze the effect of ultrasound on the spatial diffraction intensity distribution between the FFS and the BFS reflection peaks shown on the Figure 2(a), Figure 2(b)
Summary
Experiments that confirmed the correctness of theoretical considerations based on the dynamical theory of waveHow to cite this paper: Raitman, E., Gavrilov, V., Mjasischev, D., Ekmanis, Ju., Hoser, A. and Hoffmann, T. (2015) Neutron Back- and Front-Face Bragg Diffraction on a Thin Si Single Crystal Excited by Ultrasound. In [4] [5] studying neutron wave front-face, back-face and end-face scattering in a thick perfect Si and Ge crystals, Bragg reflections profiles were measured by scanning with a very narrow analyzing slit across the diffracted beam In these experiments, the sample was not moved while the slit was scanned across the outgoing beam. The interference effects from the wave fields causing the almost zero intensity diffraction disappear very quickly if the translation symmetry in a perfect crystal is violated due to any disturbance, such as static deformation strain or the ultrasonic waves. In the both cases Bragg-reflected intensity increases. In [9] [10] it was shown that back-face Bragg diffraction is very sensitive to the ultrasmall static deformation strain
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call