How to calculate fragmentation cross-section]

Dear FLUKA experts,

I would like to calculate the energy dependent fragmentation
cross-section with FLUKA, particularly of Fe-56(C,x)X reactions (X is
projectile fragments heavier than C). I would appreciate if someone
could tell me if the following scheme is correct.

1, Run FLUKA with dumping projectile kinetic energy GeV/u
(etrack-am(jtrack))/(am(jtrack)/ AMUGEV)
 and its statistical weight (wtrack) every time when a projectile
fragment of interest is produced.
In the simulation, thick carbon target is simply bombarded by 500 MeV/u
Fe ions.
The mgdraw routine linked to FLUKA "mgdraw_exci.f" is attached. The
input file is also attached as "frag_exc.inp"

2, The fragmentation cross-section (e.g. Fe-56(C,x)Mn-54 at Energy = 300
MeV/u +-5 MeV/u ) is obtained as

sigma = s/(# of history)/(total track length of primary ion beam between
300-5 MeV/u and 300+5 MeV/u)/(atomic density of target)

where s is the sum of the output statistical weights of the cases
primary ion energy is from 300-5 MeV/u to 300+5 MeV/u and produced
fragment is Mn-54.

The obtained cross-section seems a little bit low (Please see the
attached "plot.jpg" Fe-56(C,x)Mn-54 cross-section. The drop at 100 MeV/u
is because FLUKA-2008 was used). Any suggestions are appreciated.

Many thanks in advance,
Tatsuhiko

-- 
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 Department of Nuclear Engineering and Management
        Graduate School of Engineering
           The University of Tokyo
              Tatsuhiko Ogawa
   E-mail:  ogawa_at_n.t.u-tokyo.ac.jp, togawa_at_cern.ch
      Tel:   03-5841-2905  (+81-3-5841-2905)
Facsimile:   03-5841-2922  (+81-3-5841-2922)
  Address: 2-11-16, Dept. Nucl. Eng. Annex R-230
          Yayoi Bunkyo-ku, Tokyo, Japan 113-0032
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