Hi Benjaminas,
I didn't find usimbs.f in the link you provided but that's probably not
necessary anyway. A few basic principles:
- the simplest way to do importance biasing is to assign the importance as
WHAT(3) in the BIASING card, without any user routines;
- whether we do importance biasing via BIASING WHAT(3), usimbs.f or ubsset.f, we
always do a dry run first (eg. with START WHAT(1)=10.) to generate a .out so
that we can inspect 2 tables:
"Particle transport thresholds:" and
"Region Particle importances"
to verify that our intended importance values have been successfully parsed.
- the following confirm that biasing (importance and other techniques) has
indeed been at work:
1) towards the end of .out:
"Total number of inelastic interactions (stars)" should be noticeably larger
than
"Total weight of the inelastic interactions (stars)"
2) also towards the end of .out:
"Total number of elastic interactions" should be noticeably larger than
"Total weight of the elastic interactions:"
3) in mgdraw.f (not necessary to check this under normal circumstances) WTRACK
should sometimes have values <1.
"GeV missing" is no cause for worry. Please refer to:
http://www.fluka.org/fluka.php?id=faq&sub=10
An extra note: "it seems to work and no errors" is not the recommended way to do
Monte Carlo ;)
:) mary
From: Benjaminas Marcinkevicius <b.marcinkevicius_at_gmail.com
<mailto:b.marcinkevicius_at_gmail.com?Subject=Re%3A%20%5Bfluka-discuss%5D%3A%20Usimbs%20routine%20help%20%3F>
>
Date: Tue, 4 Feb 2014 21:36:57 +0200
Hi,
I am new to FLUKA and FORTRAN so my issue might be trivial but still.
1. I'm trying simplified beam dump geometry. I am using usimbs.f routine to
bias neutrons in radial direction. the routine was taken from example i got
and i modified to my problem. It seems to work and no errors that i noticed
are issued, but the neutrons do not penetrate deeper than R=340 cm. I tried
500 and 5000 particle runs and it seems that neutrons do not go further. I
haven't found any mistakes in geometry or material so thought maybe my
modification of routine was wrong.
This is link to nps=5000 run and usimbs.f routine. includes eps file with
comparison of neutron dose rate with 500 nps and 5000 nps.
https://copy.com/TcaxOUnC7EpVQG9l
2. In total energy balance in run summary it is written that 11.9 % of
energy missing, I was wondering what is the reason of this mismatch.
Any help is appreciated.
Sincerely,
Benjaminas Marcinkevičius
Received on Sat Mar 01 2014 - 01:56:32 CET