Practical Aspects of Neutron Scattering

2020 ◽  
pp. 343-404
Author(s):  
Andrew T. Boothroyd
Keyword(s):  
Inelastic Scattering ◽  
Neutron Scattering ◽  
Multiple Scattering ◽  
Time Of Flight ◽  
Scattering Data ◽  
Data Normalization ◽  
Polarization Analysis ◽  
Ewald Sphere ◽  
Anisotropic Displacement Parameters ◽  
Counting Statistics

In this chapter, aspects of the planning and optimization of a neutron scattering experiment are covered, including attenuation, multiple scattering, data normalization, counting statistics, resolution, corrections for polarization analysis, and spurions. Practical aspects of diffraction experiments are described, including instrumentation, Rietveld refinement, anisotropic displacement parameters, the Ewald sphere construction, Lorentz factors, extinction and multiple scattering. Practical aspects of spectroscopy are also described, including triple-axis, time-of-flight and backscattering spectrometers, direct and indirect geometry, and some specific points arising in time-of flight inelastic scattering.

Characterization of alumina powder using multiple small-angle neutron scattering. I. Theory

1985 ◽  
Vol 18 (6) ◽  
pp. 467-472 ◽  
Author(s):  
N. F. Berk ◽  
K. A. Hardman-Rhyne
Keyword(s):  
Particle Size ◽  
Phase Shift ◽  
Neutron Scattering ◽  
Multiple Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Volume Fraction ◽  
Scattering Data ◽  
Alumina Powder ◽  
Beam Broadening

Microstructural parameters of high-purity alumina powder are determined quantitatively throughout the bulk of the material using small-angle neutron scattering techniques. A unified theoretical and experimental approach for analyzing multiple scattering data is developed to obtain values for particle size, volume fraction and surface area. It is shown how particle size and volume fraction can be measured in a practical way from SANS data totally dominated by incoherent multiple scattering (`beam broadening'). The general phase-shift dependence of single-particle scattering is incorporated into the multiple scattering formalism, and it is also shown that the diffractive limit (small phase shift) applies even for phase shifts as large as unity (particle radii of order 1 μm). The stability of the Porod law against multiple scattering and the phase-shift scale are described, a useful empirical formula for analysis of beam broadening data is exhibited, and the applicability of the formulations to polydispersed systems is discussed.

Inelastic scattering of slow positrons by helium, neon, and argon atoms

1982 ◽  
Vol 60 (4) ◽  
pp. 584-590 ◽  
Author(s):  
P. G. Coleman ◽  
J. T. Hutton ◽  
D. R. Cook ◽  
C. A. Chandler
Keyword(s):  
Energy Loss ◽  
Inelastic Scattering ◽  
Multiple Scattering ◽  
Time Of Flight ◽  
Angular Distributions ◽  
Atomic Excitation ◽  
Helium Neon

Measurements of the excitation and ionization of helium, neon, and argon by positrons of energies between threshold and 50 eV, utilising time-of-flight energy loss spectrometry, are reported. Scattering into forward angles up to 60° is observed and the measurements suggest that sharp forward lobes exist in the angular distributions of positrons scattered following atomic excitation. Multiple scattering corrections to the measurements are described. Comparison is made with the inelastic scattering of electrons by the same atoms, and connections drawn between the present results and those of the recent complementary studies of Griffith et al. and Charlton et al.

Ultra-small-angle neutron scattering from dense micrometre-sized colloidal systems: data evaluation and comparison with static light scattering

2006 ◽  
Vol 39 (2) ◽  
pp. 202-208 ◽  
Author(s):  
Josef Innerlohinger ◽  
Mario Villa ◽  
Matthias Baron ◽  
Otto Glatter
Keyword(s):  
Light Scattering ◽  
Neutron Scattering ◽  
Multiple Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Static Light Scattering ◽  
The Other ◽  
Data Evaluation ◽  
Scattering Data ◽  
Other Hand

Ultra-small-angle neutron scattering (USANS) probes the sameqregime as static light scattering (LS), making USANS an additional tool for the study of structures between 100 nm and 10 µm. Dense oil-in-water emulsions, which have already been characterized intensively by light scattering, are investigated in this study as a model system using USANS. The two basic problems of such scattering studies are the following: on the one hand, one has to use different scattering theories for USANS and LS, and on the other hand, in both cases one has to deal not only with particle interactions but also with multiple-scattering effects. For neutron scattering it is always possible to use the simpler Rayleigh–Debye–Gans (RDG) theory instead of the Lorenz–Mie theory, which generally describes light scattering from micrometre-sized globular objects. The samples have different contrasts in neutron and light scattering, such that only low-contrast (close to index match) LS data can be interpreted by the RDG theory. The data evaluation is performed by means of the generalized indirect Fourier transformation (GIFT) method, which enables the simultaneous calculation of the form and structure factors. The results are discussed and compared with those from light scattering experiments, taking into account the advantages of both methods. The effect of multiple scattering and its influence on data evaluation is also examined. Data evaluation by applying the GIFT method works well for both neutron and light scattering data, with results of comparable quality. The advantages of light scattering are the fast data acquisition and the large number of data points. USANS, on the other hand, covers a widerqrange and the problem of multiple scattering is not as severe as for light scattering, but still must not be neglected.

Spurious peaks arising from multiple scattering events involving the sample environment in inelastic neutron scattering

2014 ◽  
Vol 47 (4) ◽  
pp. 1472-1476 ◽  
Author(s):  
Lothar Pintschovius ◽  
Dmitry Reznik ◽  
Frank Weber ◽  
Philippe Bourges ◽  
D. Parshall ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Single Crystals ◽  
Multiple Scattering ◽  
High Intensity ◽  
Inelastic Neutron Scattering ◽  
Time Of Flight ◽  
Inelastic Neutron ◽  
Small Samples ◽  
Sample Environment ◽  
Scattering Events

Well defined peaks with energies of about 18 meV have been observed in a variety of inelastic neutron scattering experiments on both single crystals and powders, using either the triple-axis or the time-of-flight technique. They can easily be mistaken for signatures of real excitations. It has been found that they are due to multiple scattering events involving primarily the walls of the sample environment. Hence, they are particularly troublesome in experiments using very small samples, as have been used with recently developed high-intensity neutron spectrometers. Measures required to reduce the unwanted scattering to a minimum are also discussed.

A Method for Interpreting Small Angle Neutron Scattering Data from Quasi-Spherical Objects

1994 ◽  
Vol 376 ◽  
Author(s):  
T.M. Sabine ◽  
W.K. Bertram ◽  
L.P. Aldridge
Keyword(s):  
Neutron Scattering ◽  
Multiple Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Small Angle Scattering ◽  
Scattering Data ◽  
Type Function ◽  
Scattering Pattern ◽  
Angle Scattering

ABSTRACTSmall angle scattering data are traditionally interpreted in terms of scattering patterns at the Porod and the Guinier limits. It is difficult to fit the entire scattering pattern to account for scattering from spheres because Rayleigh's formula contains oscillatory terms which are smeared out in practice by perturbations in the sizes of the scattering agents.It is proposed that a Lorenztian type function be used instead of Rayleigh's function. By using this equation it is possible to fit the entire small angle scattering pattern and obtain the correct forms of the Guinier and Porod limits.The effects of correlation and multiple scattering are also explored.

The use of multiple-scattering data to enhance small-angle neutron scattering experiments

1999 ◽  
Vol 55 (3) ◽  
pp. 500-507 ◽  
Author(s):  
T. M. Sabine ◽  
W. K. Bertram
Keyword(s):  
Neutron Scattering ◽  
Multiple Scattering ◽  
Cross Section ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Scattering Data ◽  
Specimen Thickness ◽  
Neutron Wavelength ◽  
The Cross ◽  
Small Angle Region

Multiple scattering of neutrons by the inhomogeneities responsible for small-angle neutron scattering (SANS) during the passage of the beam through the specimen can be used to provide valuable information about the shape of the objects and the absolute value of the contrast between the scattering particles and the matrix. The neutrons emerging from the specimen are classified into those that have been scattered n times. The index n ranges from zero to infinity. The remnant of the incident beam is the group of neutrons for which n equals zero. Each group contributes separately to the scattering profile. The small-angle scattering cross section is independent of the neutron wavelength for n = 1 only. Thus collection of data as a function of specimen thickness and of neutron wavelength will provide a number of different profiles describing the same physical situation. Simultaneous analysis of these profiles provides absolute values of the cross section for scattering into the small-angle region and of the cross section for removal of neutrons from the small-angle region. So that the method can be used generally, a profile function that is a very good approximation to those in the literature is introduced. The implications for time-of-flight SANS are discussed.

Diffuse neutron scattering in benzil, C14D10O2, using the time-of-flight Laue technique

2003 ◽  
Vol 36 (6) ◽  
pp. 1440-1447 ◽  
Author(s):  
T. R. Welberry ◽  
D. J. Goossens ◽  
W. I. F. David ◽  
M. J. Gutmann ◽  
M. J. Bull ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Good Description ◽  
Large Fraction ◽  
Three Dimensional ◽  
Time Of Flight ◽  
Limited Range ◽  
Scattering Data ◽  
Incident Neutron ◽  
X Ray ◽  
Diffuse Neutron

Diffuse neutron scattering data have been recorded for the molecular crystald-benzil, C14D10O2, using the time-of-flight Laue technique on the SXD and PRISMA instruments at ISIS. Using SXD it was possible to access a large fraction of the total three-dimensional reciprocal space out to aQvalue of 15 Å−1, using only four individual exposures and by making use of the \bar{3}m Laue symmetry of the crystal. By segregating the scattered data according to the incident neutron energy used, patterns were obtained from those neutrons in the range of ∼20 meV to 150 meV, which showed little sign of inelastic effects and so could be compared with previously analysed X-ray data. For neutron energies of <20 meV, interesting inelastic effects were observed, which have been used to obtain an estimate for the energy of phonons associated with a vibrational mode in which an intramolecular mode couples to a low-energy shearing motion of the hydrogen-bonded network linking neighbouring molecules. The estimated value of 8.95 cm−1(1.11 meV) for this mode is less than the lowest energy mode reported from spectroscopic measurements for hydrogenous benzil (∼16 cm−1). A model previously derived from analysis of X-ray data observed over a limited range ofQhas been used to calculate neutron patterns over the fullQrange. Comparison with the present neutron data has shown that while the model gives a good description of the form of the diffuse patterns, the magnitudes of the atomic displacements are underestimated by a factor of ∼2.25.

Analysis of STEM micrographs of thick objects

1978 ◽  
Vol 36 (2) ◽  
pp. 106-107
Author(s):  
S. Golladay
Keyword(s):  
Inelastic Scattering ◽  
Multiple Scattering ◽  
Mass Distribution ◽  
Cross Sections ◽  
Phase Contrast ◽  
Image Point ◽  
Contrast Effects ◽  
Total Cross Sections ◽  
Elastic And Inelastic Scattering

The theory of multiple scattering has been worked out by Groves and comparisons have been made between predicted and observed signals for thick specimens observed in a STEM under conditions where phase contrast effects are unimportant. Independent measurements of the collection efficiencies of the two STEM detectors, calculations of the ratio σe/σi = R, where σe, σi are the total cross sections for elastic and inelastic scattering respectively, and a model of the unknown mass distribution are needed for these comparisons. In this paper an extension of this work will be described which allows the determination of the required efficiencies, R, and the unknown mass distribution from the data without additional measurements or models. Essential to the analysis is the fact that in a STEM two or more signal measurements can be made simultaneously at each image point.

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