· Working Group for Theoretical
calculations
Suggestion
for a working plan – These are “4” years goals.
·
Modelling of scattering by surfaces
and interfaces with correlated or uncorrelated interfaces.
The use of “realistic correlation functions” might be introduced. Very often,
the model is limited to analytical simple functions (gaussian, Lorentzian,
self-affine).
Models of surface roughness closer to reality should be introduced.
Usually the roughness distribution at interfaces does not follow a simple “erf”
or “gaussian” function. More realistic roughness distributions should be introduced.
This modelling should be extended to the modelling of systems with very large
numbers of layers (up to 1000 in the case of neutron mirrors).
·
Multilayer optimisation for x-rays
The absorption
makes the things quite different compared to neutrons.
Make available a code to optimise the ML stacking to be able to produce proper
“band-pass” mirrors for hard/soft x-rays?
·
Magnetism
Does it make sense
to consider magnetism in diffuse x-ray scattering
·
Fitting of diffuse scattering and
inverse problem
Determine what information can be really extracted and the confidence that can
be put into the fit.
Is it possible to determine a specific experiments to extract specific parameters?
How accurate is it possible to get back to the correlation function when
measuring diffuse scattering?
The inverse problem iin diffuse scattering is very complex but may be
considered.
·
Going beyond the DWBA (Distorted
Wave Born Approximation) model
·
Make
a code available for experimentalists :
There are code dealing with diffuse scattering (XOP + IMD for example)
The range of applicability must be made clear for “beginner” users.
·
Problems of beam coherence
·
Define
standard samples and standard measurements to validate and compare different
codes
A type of code “benchmarking” could be set up (in the same way as it has been
set up in the case of micromagnetism)
·
Cross
check of theory and experiment of diffraction grationg efficiencies
·
Make
available user friendly codes for calculating efficiencies of gratings and
Fresnel lenses
·
Provide
codes for VLS (Variable Line Spacing) gratings
·
Beam-line
modelling :
In the netwrok SCANS a big effort has been made to compare the different codes
available for neutron beam line and instrument modelling. Something similar
could be done between a neutron and an x-ray code.
·
Convergence
of x-rays and neutron code
Could neutrons be included in existing x-ray beam line and spectrometer
modelling?
·
For
x-ray optics provide a user friendly code to calculate the distorsion due to
heat loading, and to incorporate this in the modelling.
Contacts
|
Dr.
Marion Bowler Daresbury Laboratory Synchrotron
Radiation Dept CLRC
Daresbury Laboratory Warrington
Wa4 4AD. UK tel 44 (0)1925
603220 |
Dr. Frédéric Ott Laboratoire Léon
Brillouin CEA/CNRS Bat. 563, CE-Saclay 91191 Gif-sur-Yvette Tel 331 69 08 61 21 Fax.: 33 1-69-08-82-61 style='mso-bidi-font-weight:normal'> |
Links
to simulation software
GENERAL
RAY-TRACING
Vitess
: Berlin neutron ray-trace simulation package.
DATABASES
REFLECTION
Publications
People involved
Updated June 18th
2002