RE: Question: How to stop neutron transport below 1 MeV and beyond 20 MeV

From: Vasilis Vlachoudis <>
Date: Tue, 10 Apr 2012 12:10:28 +0000

Dear Mohammad,

please find attached your corrected input, comscw and flair project that compiles
the comscw.f routine
comscw_mod.f: You had alignment problems. Check fortran syntax
input file: Geometry problems corrected, on overlaps of the CR39 dectors,
PHOTONUC, LOW-NEUT, PART-THR on neutrons are not needed.
Last, problem is that the beam as it is defined it doesn't impact on any target
so it goes straight away to the blackhole.

Best Regards
Vasilis Vlachoudis
CH-1211 GENEVA 23

Phone: +41-22 767 9851
GSM: +41-76 487 4378
Fax: +41-22 766 9644

From: [] on behalf of Mohammad Islam []
Sent: 09 April 2012 22:30
To: Vasilis Vlachoudis;;
Subject: Re: Question: How to stop neutron transport below 1 MeV and beyond 20 MeV

Dear Fluka Experts,

Many many thanks to vasilis and andrea for pointing out the the error I made.
I can see it now. Actually I am fairly new to fluka and trying to learn
the acitivity of different CARDS and its associated physics.

Following the suggestion made by Mr. Vasilis, I tried to activate the
USERWEIGht card and incorporated the lines

          (IF ( ISCRNG .EQ. 1 ) THEN
          END IF)

  in the code comscw.f and modified it to comscw_mod.f for the scoring
from 1-20 MeV Neutrons. But I could not get it worked. I also followed chapter
13 in the manual. I could not get fortran code compiled (complier f77,
Fedora 15) in the first place. As I am not familiar with linux or fortran, I
am finding it really hard at this point. Please help me with an example if

I attached here my input and comscw_mod.f card for expert opinion.
Again please help me in solving my problem: Scoring dose equivalent in different
detectors (CR3901, CR3902.....CR3912) only from neutrons of 1-20 MeV.

Looking forward to answer.

PhD student, Oklahoma State University

On Thu, Apr 5, 2012 at 10:02 AM, Vasilis Vlachoudis <<>> wrote:
Hi Mohammad,

indeed as Andrea pointed out there is no point in stopping the transport
above 20MeV,it would be physically wrong (killing neutrons that could
potentially arrive to your detector with less than 20 MeV).
You can stop the transport at 1 MeV BUT if you are sure that your detector
is not efficient for lower energies and you don't have any material
(e.g. fissionable) that could generate higher energy neutrons, or alpha particles.

One possible way would be to activate with the USERWEIGht card the
call to the COMSCW routine and modify the comscw.f routine accept the scoring if
the energy of the particle was in the 1-20MeV limit.

        IF ( ISCRNG .EQ. 1 ) THEN
       END IF

J0TRCK is the original particle 8=3DNEUTRON,
KTRACK is the neutron group with 102~=1MeV (Look the manual Section 10.4).

These lines says for the first USRBIN scoring ignore all particles other than neutrons
or energy >20MeV (KTRACK.EQ.0)
or energy <1MeV neutron group higher than 102
Of course all the above hold with the assumption that your CR39 is not
sensitive to other particles e.g. alphas

Vasilis Vlachoudis

Received on Tue Apr 10 2012 - 15:45:30 CEST

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