Extraction of the speed distribution function from a time‐of‐flight signal

1975 ◽  
Vol 46 (9) ◽  
pp. 3888-3893 ◽  
Author(s):  
Wen S. Young
Keyword(s):  
Distribution Function ◽  
Time Of Flight ◽  
Speed Distribution

scholarly journals Precise implications for real-space pair distribution function modeling of effects intrinsic to modern time-of-flight neutron diffractometers

2018 ◽  
Vol 74 (4) ◽  
pp. 293-307 ◽  
Author(s):  
Daniel Olds ◽  
Claire N. Saunders ◽  
Megan Peters ◽  
Thomas Proffen ◽  
Joerg Neuefeind ◽  
...  
Keyword(s):  
Distribution Function ◽  
Pair Distribution Function ◽  
Amorphous Materials ◽  
Best Practice ◽  
Time Of Flight ◽  
Real Space ◽  
Mitigation Strategies ◽  
Total Scattering ◽  
Conventional Analysis ◽  
Pdf Analysis

Total scattering and pair distribution function (PDF) methods allow for detailed study of local atomic order and disorder, including materials for which Rietveld refinements are not traditionally possible (amorphous materials, liquids, glasses and nanoparticles). With the advent of modern neutron time-of-flight (TOF) instrumentation, total scattering studies are capable of producing PDFs with ranges upwards of 100–200 Å, covering the correlation length scales of interest for many materials under study. Despite this, the refinement and subsequent analysis of data are often limited by confounding factors that are not rigorously accounted for in conventional analysis programs. While many of these artifacts are known and recognized by experts in the field, their effects and any associated mitigation strategies largely exist as passed-down `tribal' knowledge in the community, and have not been concisely demonstrated and compared in a unified presentation. This article aims to explicitly demonstrate, through reviews of previous literature, simulated analysis and real-world case studies, the effects of resolution, binning, bounds, peak shape, peak asymmetry, inconsistent conversion of TOF to d spacing and merging of multiple banks in neutron TOF data as they directly relate to real-space PDF analysis. Suggestions for best practice in analysis of data from modern neutron TOF total scattering instruments when using conventional analysis programs are made, as well as recommendations for improved analysis methods and future instrument design.

scholarly journals Non-hydrodynamic Contributions to the End Effects in Time of Flight Swarm Experiments

1987 ◽  
Vol 40 (4) ◽  
pp. 519 ◽  
Author(s):  
Russell K Standish
Keyword(s):  
Distribution Function ◽  
Power Series ◽  
Transport Coefficients ◽  
Time Of Flight ◽  
Lithium Ions ◽  
End Effects ◽  
Flight Experiment ◽  
Drift Length ◽  
Order Of Magnitude ◽  
Hydrodynamic Effects

The hydrodynamic part of the distribution function of a swarm is separated from its nonhydrodynamic part using a projection operator, leading to an explicit expression for the timedependent transport coefficients. These are then related to a time of flight experiment. The contribution from non-hydrodynamic effects to the measured drift velocity is shown to be a power series in 11 d, where d is the drift length. A calculation based on an exactly soluble Fokker-Planck model shows that the correction to mobility measurements of lithium ions in helium due to non-hydrodynamic effects is of the same order of magnitude as those observed experimentally.

Determination of pole figure coverage for texture measurements with neutron time-of-flight diffractometers

2018 ◽  
Vol 51 (3) ◽  
pp. 895-900 ◽  
Author(s):  
Shigehiro Takajo ◽  
Sven C. Vogel
Keyword(s):  
Distribution Function ◽  
Pole Figure ◽  
Orientation Distribution Function ◽  
Time Of Flight ◽  
Orientation Distribution ◽  
Neutron Time ◽  
Crucial Parameter

The coverage of a given diffraction instrument as a percentage of the area 2π of a pole figure hemisphere is a crucial parameter of each diffraction instrument used for texture or strain pole figure determination. On the basis of this knowledge, the number of rotations and rotation angles for a full determination of the orientation distribution function can be optimized. However, the determination of this quantity is non-trivial. This paper presents a method that projects a given detector coverage into pole figure space, i.e. outlines the detector areas in a pole figure, and then determines the fraction of the entire 2π pole figure hemisphere around the sample that is covered. The freely available Generic Mapping Tools (GMT) and ImageJ are utilized for this quantification. With this method, it is shown that the empirically determined rotation angles for the HIPPO neutron time-of-flight diffractometer are close to optimal for a set of three rotations.

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