--------------------------------- The version of EGS4 which had been linked to FLUKA87 was an early one, which did not include the PRESTA algorithm for the control of the multiple scattering step and was therefore very sensitive to the step length chosen. In 1989, Ferrari and Sala developed and implemented in FLUKA an independent model which had several advantages even with respect to PRESTA: it was accounting for several correlations, it sampled the path length correction accounting for the first and second moment of its distribution, it allowed the introduction of high-energy effects (nuclear form factors) and could be easily integrated within the Combinatorial Geometry package. The algorithm, which included also higher order Born approximations, was very efficient and was taking care also of special high-energy effects, very grazing angles, correlations between angular, lateral and longitudinal displacements, backscattering near a boundary etc. The Ferrari-Sala model, which has proved very robust and has been shown to reproduce with good accuracy even backscattering experiments, was applied to both electrons and heavier charged particles. The final revision and update of the algorithm were made in 1991. In 1995, the Fano correction for multiple scattering of heavy charged particles was introduced.
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