GRASP Integrated 3D Plotter: GRIP.

In research on mesoscale structure and correlations, small-angle neutron scattering (SANS) is increasingly being employed to map fully three-dimensional distributions of scattered intensity at low momentum transfer. While traditionally SANS experiments and data analysis methods are designed to prioritize the determination of salient information in only one or two dimensions, the trend towards volumetric intensity mapping experiments calls for new software tools to assist with analyzing the resulting datasets. In this paper, we describe the development of a new software module, the GRASP Integrated 3D Plotter (GRIP). GRIP adds numerous features to GRASP, a widely used SANS analysis program that was written in MATLAB and developed at the Institut Laue-Langevin, France. The GRIP module provides multiple methods of three-dimensional SANS data visualization and new abilities to perform 1D and 2D cuts in various momentum-space coordinate systems, including reciprocal lattice units relevant for single-crystal studies. GRIP also includes the ability to fit diffraction peaks to a fully three-dimensional ellipsoidal Gaussian function to extract peak parameters including peak intensity, location and width, as well as a built-in calculator for estimating the resolution-deconvolved 3D coherence lengths in a sample. GRIP thus represents a significant addition to GRASP which extends the utility and application of SANS. Valuable advantages are provided, in particular, for 'small-angle neutron diffraction' studies of mesoscale correlations in single crystals, such as those due to incommensurate magnetic spin textures like spirals and topological skyrmion lattices.