18.10} Multiple Coulomb scattering

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 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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