scholarly journals Energy separation of neutrons scattered at small angles from silicon using time-of-flight techniques

2006 ◽  
Vol 39 (1) ◽  
pp. 46-52 ◽  
Author(s):  
J. Y. Cheung ◽  
R. J. Stewart ◽  
R. P. May
Keyword(s):  
Quantitative Analysis ◽  
Small Angle Neutron Scattering ◽  
Phonon Dispersion ◽  
Time Of Flight ◽  
Energy Separation ◽  
Temperature Dependent ◽  
Neutron Spectrometer ◽  
Phonon Dispersion Curves ◽  
Gain Energy ◽  
Scattered Neutrons

The time-of-flight technique is used on a small-angle neutron scattering instrument to separate the energies of the scattered neutrons, in order to determine the origin of the temperature-dependent scattering observed from silicon atQ> ∼0.1 Å−1. A quantitative analysis of the results in comparison with the phonon dispersion curves, determined by Dolling using a triple-axis neutron spectrometer, shows that the temperature-dependent scattering can be understood in terms of Umklapp processes whereby neutrons gain energy from phonons.

Temperature-dependent X-ray dynamical diffraction: Darwin theory simulations

1999 ◽  
Vol 55 (1) ◽  
pp. 14-19 ◽  
Author(s):  
Jin-Seok Chung ◽  
Stephen M. Durbin
Keyword(s):  
Phonon Dispersion ◽  
Lattice Vibrations ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Phonon Dispersion Curves ◽  
Dynamical Diffraction ◽  
X Ray ◽  
Ergodic Hypothesis ◽  
Thermal Vibrations ◽  
Good Agreement

Thermal vibrations destroy the perfect crystalline periodicity generally assumed by dynamical diffraction theories. This can lead to some difficulty in deriving the temperature dependence of X-ray reflectivity from otherwise perfect crystals. This difficulty is overcome here in numerical simulations based on the extended Darwin theory, which does not require periodicity. Using Si and Ge as model materials, it is shown how to map the lattice vibrations derived from measured phonon dispersion curves onto a suitable Darwin model. Good agreement is observed with the usual Debye–Waller behavior predicted by standard theories, except at high temperatures for high-order reflections. These deviations are discussed in terms of a possible breakdown of the ergodic hypothesis for X-ray diffraction.

Simulations of scattered neutrons for the time-of-flight enhanced diagnostics (TOFED) neutron spectrometer on EAST

2020 ◽  
Vol 22 (8) ◽  
pp. 084004
Author(s):  
Jiaqi SUN ◽  
Zhimeng HU ◽  
Lijian GE ◽  
Yimo ZHANG ◽  
Tengfei DU ◽  
...  
Keyword(s):  
Time Of Flight ◽  
Neutron Spectrometer ◽  
Scattered Neutrons

scholarly journals Separation of the inelastic and elastic scattering in time-of-flight mode on the pinhole small-angle neutron scattering diffractometer KWS-2

2021 ◽  
Vol 54 (4) ◽  
Author(s):  
Livia Balacescu ◽  
Georg Brandl ◽  
Aurel Radulescu
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Significant Contribution ◽  
Time Of Flight ◽  
Standard Samples ◽  
Reduction Procedure ◽  
Flight Mode ◽  
And Control ◽  
Scattered Neutrons

To study and control the incoherent inelastic background in small-angle neutron scattering, which makes a significant contribution to the detected scattering from hydrocarbon systems, the KWS-2 small-angle neutron scattering diffractometer operated by the Jülich Centre for Neutron Science (JCNS) at Heinz-Maier Leibnitz Zentrum (MLZ), Garching, Germany, was equipped with a secondary single-disc chopper that is placed in front of the sample stage. This makes it possible to record in time-of-flight mode the scattered neutrons in the high-Q regime of the instrument (i.e. short incoming wavelengths and detection distances) and to discard the inelastic component from the measured data. Examples of measurements on different materials routinely used as standard samples, sample containers and solvents in the experiments at KWS-2 are presented. When only the elastic region of the spectrum is used in the data-reduction procedure, a decrease of up to two times in the incoherent background of the experimentally measured scattering cross section may be obtained. The proof of principle is demonstrated on a solution of bovine serum albumin in D2O.

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