FLUKA: missing energy

[Gregor Wagner <gwagner@mail.desy.de>]

Dear Fluka-users, 

I am using a beam of neutrons as primary particles. For every run I get a
large value of 'missing' energy in the run statistics table for deposited
energy per beam particle:

e.g.: for a beam of 140 MeV neutrons 33.5% of the deposited energy is
'missing'

Neutron beams of lower energies cause even a negative value of
'missing' energy. In this case, the energy deposited by EM-cascades and
by low energy neutrons is much larger than the energy of the primary beam
particle:

for example:
4.200E-05 GEV (100.%) DEPOSITED PER BEAM PARTICLE  OUT OF WHICH
1.488E-04 GEV (****%) BY EM-CASCADE,
2.464E-11 GEV ( 0.0%) BY PARTICLES BELOW THRESHOLD,
4.837E-05 GEV (****%) BY LOW ENERGY NEUTRONS,
-1.552E-04 GEV (****%) MISSING.
all other entries are zero

if the beam energy is further decreased (1E-8 to 1E-6 GeV), the energy
deposited by EM-cascades stays in the range from 1.E-4 to 2.E-4 GeV.

Does anybody know, where these 'missing' energy values could come from?
And what is the reason, that the energy deposited by electromagnetic
cascades is larger than the beam energy?

Regards,
Gregor