QtiKWS: user-friendly program for reduction, visualization, analysis and fit of SA(N)S data
Vitaliy Pipich, 2007
QtiKWS is the cross-compiled program designed for the graphical visualization, reduction, analysis, and fit of data produced by small-angle neutron scattering (SANS) instrument. Originally developed for use with the data from the SANS instruments of the Jülich Centre for Neutron Science (JCNS ) at FRM2 reactor in Garching (Germany), but most of functions could be used for any SANS instrument. QtiKWS is forked from the free software package qtiplot (v.0.8.9). QtiPlot is open source platform independent alternative to proprietary scientific software like Origin, SigmaPlot, Regressi or Igor Pro. The numerical routines have been written in C whereas the menu interface has been written in Qt/C++. GNU-licensed mathematical library GSL is used for the implementation of mathematical algorithms. Tables, matrixes, 2D and 3D graphs could be saved as a single project file and easy accessible by the built project explorer.
Fitting interface “FIT-1d” allows to an user to fit radial averaged datasets taking into account polydispersity of any parameter of a fitting function and/or the instrument resolution. Global fit algorithm has been implemented, which allows to simultaneously fit several scattering curves with a common set of parameters. “Set-by-Set” algorithm allows to start a fitting procedure of hundreds datasets in two mouse clicks. This option is especially important for time resolved measurements, when datasets should be analyzed in the same way. Powerful function simulator simplifies the estimation of initial fitting parameters and the presentation of the obtained fitting curve. Fitting of 2d-datasets has been implemented in “FIT-2d” interface. An advance of the fitting with qtiKWS is the runtime compilation of a fitting function. An user of this program has possibility to check code of the function, change , and recompile it as a new function. The user-friendly interface “FIT-compile” allows to create and compile any complex function. GSL numerical algorithms could be easily used in the function body. The fitting function is written in C, but there are implemented an option of calling of FORTRAN functions. Users simply download and run QtiKWS compiled for Windows and Linux computer platforms.
QtiKWS::DAN: “instrument-free” approach for SANS data treatment
Vitaliy Pipich, 2013
Probably, small angle neutron scattering (SANS) is one of “easiest” neutron-related-method to understand technique and to interpret obtained results for a not experienced user: adjustable pinhole collimator, sample, and 2D-detector. The user could have the same illusion about SANS also after measurement and data reduction: if sample scatters well, instrument works stably, and number of instrument configurations is limited to one… But, in order to measure a sample in the full Q-range at a classical non-TOF SANS instrument, number of instrument configurations should be higher than three. This increases in geometrical progression number of calibration files; and data reduction becomes already really painful.
The aim of SANS data reduction interface “DAN-light” developed within the cross-compiled software package QtiKWS [ www.qtikws.de ] to keep “illusion of simplicity” for a starter and “filling of full control” for a guru of small angle scattering. “Illusion of simplicity” is saved by step-by-step definition of two script tables, namely a table of configurations and sample table. It allows proceeding of all measured datasets within “5 minutes principle”; re-treatment with changed parameters will take only few seconds.
Run-time creation/configuration of data-reduction-algorithm allows to an instrument responsible to optimize data treatment procedure correspondingly to the current status of the instrument or experiment and to control data output at every step. Extraction of needed parameters from files is controlled by universal header-reader tool. The header-reader could read free-format ASCII files with known position of parameters; find parameters by a key sequence; extract data from encoded-data-formats like XML and YAML. It allows integrating most of SANS instruments and data-treatment-procedure looks similar for all of them. “Instrument-free” approach means “independence” from data format; and “dependence” on algorithms of data treatment.
Now, this software package is standard data-reduction-tool for two classical SANS instruments KWS-1 and KWS-2 as well as for very-high resolution focusing SANS diffractometer KWS-3 of the Jülich Centre for Neutron Science (JCNS) at FRM2 reactor in Garching (Germany). Behind current version there are six years of intensive user- and instrument operation as well as source evolution.