[neutron-mc] Integrated Flux - Discrepancies between McStas and MCNP

[George Apostolopoulos]

Dear all,

Being a new user of McStas, but with some experience in Monte-Carlo with
MCNP, 
one of the first things that I tried to understand was how the
normalization is handled 
in McStas. After running some test problems the normalization became
clear but 
I noticed some discrepancies between McStas and MCNP which I cannot
understand.

Specifically, consider the following simple example: 
Particles emitted by a square (d x d) surface source are counted by a
square 
monitor, with the same area (d x d), positioned at a distance D.

I run this problem both in McStas and MCNP and the results I get agree
very well when 
D>>d but differ by up to 20% when D~d. 
A plain numerical integration agrees with MCNP, but this requires
discussion.

You will find a detailed report in the attached document.

Best regards

******************************************************
Dr. Georgios Apostolopoulos
Institute of Nuclear Technology & Radiation Protection
National Center for Scientific Research "Demokritos"
15310 Agia Paraskevi Attikis, Greece

tel +30-210-650-3731 
fax +30-210-653-3431
email: gapost at ipta.demokritos.gr
******************************************************
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