Simulation of the collimator of the residual stress instrument

In order to understand the detailed influence from the collimator system to the main index of the Residual Stress Nertron Diffractometer (RSND) such as the flux at sample position, and the resolution of the spectrometer, the MCStas simulation software is used to build the proper Model of the Collimator system to complete the calculation and simulation. During the simulation, the authors setup the divergence and length of each collimator to check if it had big effect to the whole system. Based on the simulation, the authors obtained an optimized result: When the α1=α2=30', the horizontal flux at the sample position can be 2.3 x 106 n·cm-2·s-1, the vertical flux can be 3.5 x 106 n·cm-2·s-1, and when the α1=α2=10' the best resolution of the spectrometer can be 0.2 degree. This is a valuable result for the RDND. (authors)