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

From: Vasilis Vlachoudis <>
Date: Thu, 5 Apr 2012 17:02:59 +0200

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 Thu Apr 05 2012 - 17:37:57 CEST

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