Neutron Bragg Diffraction on a Bent Silicon Single Crystal Excited by Ultrasound

Neutron Bragg Diffraction on a Bent Silicon Single Crystal Excited by UltrasoundThe 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 amplitudew.The calibration parameters between the generator voltage and acoustic wave amplitude were derived assumingw= (2.3±0.3)·10-2Å/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.

Download Full-text

Acoustooptic Diffraction of Three-Color Radiation on a Single Acoustic Wave

International Journal of Optics ◽

10.1155/2019/4386093 ◽

2019 ◽

Vol 2019 ◽

pp. 1-5

Author(s):

V. M. Kotov ◽

S. V. Averin

Keyword(s):

Acoustic Wave ◽

Single Crystal ◽

Diffraction Efficiency ◽

High Frequency ◽

Acoustic Power ◽

Bragg Diffraction ◽

Acoustic Frequency ◽

Acoustooptic Interaction

Bragg diffraction which provides effective acoustooptic interaction of three-color radiation with a single acoustic wave at a high frequency of sound is proposed and tested in a single crystal of paratellurite at the wavelengths of λ= 0.488, 0.514, and 0.633 μm. Maximal diffraction efficiency of radiation with λ=0.633 μm at acoustic frequency of 150 MHz is 88% and that with λ= 0.488 μm and λ=0.514 μm is 60%. In diffraction efficiency range from 0 to 40% the dependence of all beams on acoustic power is the same.

Download Full-text

Suppression of Surface Effect by Using Bent-Perfect-Crystal Monochromator in Residual Strain Scanning

Materials Science Forum ◽

10.4028/www.scientific.net/msf.490-491.234 ◽

2005 ◽

Vol 490-491 ◽

pp. 234-238 ◽

Cited By ~ 7

Author(s):

Miroslav Vrána ◽

Pavol Mikula

Keyword(s):

Residual Strain ◽

Strong Correlation ◽

Surface Effect ◽

Polycrystalline Sample ◽

Sample Surface ◽

Perfect Crystal ◽

Bragg Diffraction ◽

Bending Radius ◽

Reactor Spectrum ◽

Diffraction Optics

Using our long experience in Bragg diffraction optics we successfully used focusing principles for substantial increasing both luminosity and resolution of the strain scanners with respect to the conventional devices. Monochromatic neutrons are selected by the cylindrically bent monochromator from the reactor spectrum. There is a strong correlation between divergences of incoming and outgoing beams with respect to the polycrystalline sample, which can be easily manipulated by changing the monochromator bending radius. By setting a proper value of the radius, a narrow, quasiparallel and highly luminous output beam can by adjusted. The strong correlation between wavelength and direction of incoming and outgoing beams depending on the monochromator bending radius can be as well used for suppression of surface effect in residual strain scanning. In scanning near a sample surface aberration peak shifts arise due to the fact that the gauge volume defined by input and output slits is partially out of the sample and its value can be of the same order as the residual strain effects. In this work we demonstrate that by changing of the bending radius of monochromator, this surface effect can be suppressed to values smaller then experimental errors in residual strain scanning.

Download Full-text

Ultrasound effect on neutron Bragg diffraction in a perfect and deformed silicon single crystal

Journal of Surface Investigation X-ray Synchrotron and Neutron Techniques ◽

10.1134/s1027451009060093 ◽

2009 ◽

Vol 3 (6) ◽

pp. 902-907 ◽

Cited By ~ 4

Author(s):

E. Raitman ◽

V. Gavrilov ◽

D. Mjasischev ◽

M. Brezgunov

Keyword(s):

Single Crystal ◽

Silicon Single Crystal ◽

Bragg Diffraction ◽

Ultrasound Effect

Download Full-text

Neutron Laue Diffraction in Perfect and Deformed Silicon Single Crystals Under Ultrasound Excitation

Latvian Journal of Physics and Technical Sciences ◽

10.2478/v10047-008-0019-1 ◽

2008 ◽

Vol 45 (4) ◽

pp. 47-56

Author(s):

E. Raitman ◽

V. Gavrilov ◽

M. Brezgunov

Keyword(s):

Single Crystals ◽

Wave Amplitude ◽

Perfect Crystal ◽

Ultrasound Wave ◽

Diffraction Intensity ◽

Laue Diffraction ◽

Theoretical Concepts ◽

New Type ◽

Adiabatic Motion

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.

Download Full-text

Detection of a point defect in a silicon single crystal by high-resolution TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100138701 ◽

1995 ◽

Vol 53 ◽

pp. 466-467

Author(s):

M. Awaji

Keyword(s):

High Resolution ◽

Single Crystal ◽

Point Defect ◽

Point Defects ◽

Noise Level ◽

Dark Field ◽

Silicon Single Crystal ◽

High Resolution Image ◽

Dark Field Imaging ◽

Field Imaging

It is necessary to improve the resolution, brightness and signal-to-noise ratio(s/n) for the detection and identification of point defects in crystals. In order to observe point defects, multi-beam dark-field imaging is one of the useful methods. Though this method can improve resolution and brightness compared with dark-field imaging by diffuse scattering, the problem of s/n still exists. In order to improve the exposure time due to the low intensity of the dark-field image and the low resolution, we discuss in this paper the bright-field high-resolution image and the corresponding subtracted image with reference to a changing noise level, and examine the possibility for in-situ observation, identification and detection of the movement of a point defect produced in the early stage of damage process by high energy electron bombardment.The high-resolution image contrast of a silicon single crystal in the [10] orientation containing a triple divacancy cluster is calculated using the Cowley-Moodie dynamical theory and for a changing gaussian noise level. This divacancy model was deduced from experimental results obtained by electron spin resonance. The calculation condition was for the lMeV Berkeley ARM operated at 800KeV.

Download Full-text