Version 2.0, R. Ghosh, March 1999
Precise measurement of scattering from liquids over a large range of momentum transfer, especially using isotope substitution, reveals the pair correlation functions in multi-component liquids and glasses.
All the following programs use a command line syntax and can be run over a telnet connection without need of mouse input. The programs d4get, d4reg, d4opr, d4fou and d4pro have on-line help files. The command line syntax for the other programs is displayed if the program name is given with no further arguments. The Unix environment on d4sgi.ill.fr allows do* command files for executing a series of these programs. All programs use global variables for pathnames, etc, which are set during the login as d4.
d4reg reduces data from the two area detectors used in these
experiments taking account of the current detector efficiencies
to produce a file of intensity(angle). Data may be normalised
either to monitor counts or time.
The sequence of disk searching is serdon/data, then
serdon/data-1 When the uncompress (-u) option is given all
serdon/cycle disks are searched and the data are automatically
uncompressed.
Output: ASCII *.reg file, containing three columns,
2theta, counts, and sigma
*.cmd files exist for adjusting the overlap regions between detector 1 and detector 2, converting the *.reg files to *.q files based on the measured wavelength, zero angles, and for the Placzek inelasticity correction.
d4eff produces the file of detector efficiency normalisations
which can be measured in calibration runs.
Output: ASCII *.eff file containing two columns,
cell#, efficiency
d4opr will operate on two regrouped files, performing arithmetic functions +,-,*,/. The result is another *.reg file including the sigma column. This program is mostly used for subtracting background scans and dividing successive scans for stability checks.
d4get extracts a choice of several parameters from a sequence
of numor files, e.g. time, temperature etc., which may be plotted
using gnuplot.
Output: ASCII *.get files containing the extracted parameters in
columns suitable for plotting programs.
d4nifit fits a (*.reg) file from a nickel powder
sample to determine the neutron wavelength and zero angles.
Output: ASCII *.res result file containing values of the fitted
parameters together with their correlation matrix.
lorgaun fits up to 9 pseudo-voigt functions plus a linear
background. It includes scale transformation between 2theta and Q
and plots results.
Output: ASCII *.res files asd4nifit, and *.wri files containing the
transformed data.
polyfit is available for fitting polynomials of positive and negativ powers.
d4fou performs a (normalisable) sine-integral Fourier
transform of *.q files. Output: ascii *.fou files containing
ghuplot-able columns for:
r, G(r), sigma, G(r)/(4pi*r*N), g(r)=(col4/scale)+1, RDF=N*G(r)*4pi*r**2
where N is the atomic number density, and scale is a normalisation
constant.
d4pro calculates the D4 resolution profile function for a peak at a given scattering angle, 2theta, including the umbrella effect at low-angles. Afterwards a moments calculation program (mome.exe) can be used to calculate the correction coefficients for deconvolution of the S(q) data. Results may be examined using gnuplot, with the aid of script files.
Information from H Fischer, fischer@ill.fr, March 1999