LAUSR

While I was an undergraduate student, I was fascinated by the grain boundary segregation in metallic alloys in relation with the formation of unwanted precipitated that reduce their mechanical properties. This quickly led me to perform graduate studies in electron microscopy, especially TEM, to perform such measurements. Then, I found a paper by David Joy et al. [1] that describe the effect of Fast Secondary Electrons [FSE] on x-ray generation. Their simulations showed that they are emitted almost perpendicularly to the incident beam and also that they can generate a significant fraction of the x-rays for energy lines below 1 keV. I already saw the possible degradation of the spatial resolution to measure Oxygen or Carbon segregation at grain boundaries. As a result, I became heavily interested about Monte Carlo simulations of electron trajectories in solids around 1985. Them, I developed my first Monte Carlo programs, from scratch while I was a graduate student at École Polytechnique de Montéal, for the simulation of the effect of FSE on Cliff-Lorimer K factors in the TEM [2] and also of the quantification of spherical inclusions in bulk specimens using x-ray microanalysis in the SEM [3]. I met David Joy the first time at the 1988 EMSA conference of Milwaukee where I asked him questions about the modelling of ionization cross-sections that fails at low overvoltage giving negative values and therefore subtracting the x-ray intensities generated by the FSE. As a result, we started to collaborate and I visited him many times in Knoxville. He gave me his computed values of the Mott elastic cross sections around 1992.This was great because they are difficult to compute but are more accurate than the Rutherford cross sections below 10 keV. With my graduate students at that time, Dominique Drouin and Pierre Hovington, they were used to develop the CASINO program that is well known since its release in 1996 [4]. David Joy help has to be credited in the development of CASINO. Figure [1] shows a classical plot of electron trajectories in Si at 30 keV computed with CASINO.