Alberto Cereser, [email protected]

Technical University of Denmark, 15 February 2016

In this repository you can find the files I used to simulate a time-of-flight 3D Neutron Diffraction (ToF 3DND) experiment with a polycrystalline sample at beamline BL18, J-PARC, using McStas. The BL18 setup is described by BL18_pxtal_BOTH.instr; to speed up the computational time, the simulation can be performed with only the near- or the far-field detectors mounted (relative instrument files: BL18_pxtal_MCP.instr and BL18_pxtal_FF.instr). The description of the far-field detectors is in a separate file, detector_arms.instr.

The J-PARC source is described by source_BL18.txt.

As a sample, we consider an Iron cylinder consisting of 20 regions with random orientation. default.map_101x101_rectified is a voxellized map of the sample, with the voxel orientations defined by default.orts. The reflections for Iron are listed in Fe.lau, generated using Crystallographica.

To save the output data using the same format of the detetcors at J-PARC, E. Knudsen developed the new modules FITS_monitor.comp and HDB_monitor.comp.

The approach presented above, where a polycrystalline sample is used, was developed to cross-check the algorithms developed analysing data collected at BL18, J-PARC, using ToF 3DND. A simpler setup, with a sample consisting of three iron single crystals, was used for preliminary feasibility tests. Instr file: BL18_three_crystals.instr.