Implementation of amorphous and crystalline powder X-ray diffractive scattering in the EGS code - 084

The EGS4 and EGSnrc codes are widely used for modeling Xray and electron transport. Coherent or Rayleigh scattering is modelled using the independent atom approximation (IAA). The IAA ignores material structure above the atomic scale and hence fails to model diffraction effects occurring in amorphous and crystalline materials. We have extended the EGSnrc code to allow the user to modify both the coherent scattering form-factor and coherent cross-section. We have developed a computer program to calculate the appropriate form-factor and cross-section information for arbitrary mixtures of amorphous and powdered crystalline materials. The extended EGSnrc code has been used to assist in the design and optimisation of an energy-dispersive X-ray analyser suitable for on-stream measurement of mineral slurries. We are developing an energy-dispersive X-ray diffraction spectrometer suitable for direct, on-stream measurement of slurries of mineral species mixed with water passing through a pipeline. The spectrometer uses a 150 kV X-ray tube and a high-resolution detector to measure the energy spectrum of X-rays diffracted through small angles by mineral samples. We have used our modified EGSnrc code to model the proposed experimental arrangement. Simulation results will be presented for a range of mineral materials