Differences in Flux and Dose Equivalent Errors in USRTRACK

Dear Experts,

In a recent FLUKA case I have undertaken, I've scored both neutron
fluence and neutron dose equivalent in the same geometry region, using
USRTRACK.

I have used two separate USRTRACK cards with different names. The first
scores neutron fluence. The second scores dose equivalent and applies
AMB74 flux-dose conversion factors for neutrons only through an AUXSCORE
card. I ran the case for 10 cycles, 1.e7 primary particles per cycle.
The sources is a proton beam with a rectangular spectrum, energy range
190-210 MeV.

Upon viewing the results, I noticed that the 2 USRTRACKS had very
different associated standard deviations when I would expect that
neutron fluence and neutron dose equivalent should have the same
standard deviation as the only difference is the application of
fluence-dose equivalent conversion coefficients! Can anyone tell me the
reason why this is the case? I'm suspecting maybe the standard deviation
in the dose equivalent output is in fact for all particles, whereas the
result has been filtered for neutrons only, is =
this the case?

Many thanks,
Lewis MacFarlane.
Received on Thu Apr 21 2011 - 22:25:46 CEST