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18.18} Scoring


 The stress put on built-in generalised scoring options is another
 aspect of FLUKA "philosophy" which differentiates it from many other
 programs where users are supposed to write their own ad-hoc scoring
 routines for each problem.  This characteristics, which was already
 typical of the old Ranft codes, has allowed to develop in the modern
 FLUKA some rather sophisticated scoring algorithms that would have been
 too complex for a generic user to program. For instance the "track-length
 apportioning" technique, introduced in 1990 by Fasso` and Ferrari,
 used in dose and fluence binning, which computes the exact length of
 segment travelled by the particle in each bin of a geometry independent
 grid. This technique ensures fast convergence even when the scoring
 mesh is much smaller than the charged particle step.

 Different kinds of fluence estimators (track-length, collision,
 boundary crossing) were implemented in 1990-1992, replacing the
 corresponding old ones. The dimension limitations (number of
 energy intervals) were removed and replaced by a much larger
 flexibility due to dynamical memory allocation. Scoring as a function
 of angle with respect to the normal to a surface at the point of
 crossing was also introduced. Facilities were made available to score
 event by event energy deposition and coincidences or anti-coincidences
 between energy deposition signals in different regions, and to study
 fluctuations between different particle histories.

 The pre-existent option to write a collision file was completely
 re-written and adapted to the more extended capabilities of the new
 code. In 1991, time gates became applicable to most scoring
 facilities, allowing to ignore delayed radiation components such as
 multiply scattered low energy neutrons.

 In 1994, two new options were added: residual nuclei scoring and
 scoring of particle yields as a function of angle with respect to a
 fixed direction. In the latter case, several new quantities can be
 scored, such as rapidity, various kinematical quantities in the lab
 and in the centre-of-mass frame, Feynman-x etc.

 In 2005, the possibility to follow on-line the radiation from unstable
 residual nuclei has been implemented, together with an exact analytical
 calculation (Bateman equations) of activity evolution during irradiation
 an cooling down. As a consequence, results for production of residuals
 and their effects as a function of time can be performed in the same run.

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