EMFCUT, basic understanding check

From: Bertrand H. Biritz <beb2015_at_med.cornell.edu>
Date: Thu, 07 Apr 2011 22:08:52 -0400

Dear FLUKA users,

After re-reading the manual, googling through the threads and also
reading the latest presentations from the Heidelberg course I wanted to
verify that I am using the EMFCUT card for my simulation correctly.

The basic geometry is a 4 MeV electron beam goes through a bore in a
tungsten cube with a target inside, the tungsten being the shielding. I
am interested in scoring the DOSE-EQ in air outside of this target to
see how much radiation a person would receive when standing a certain
distance away from the target.
Via the EMFCUT card I set the production threshold in air to 1keV but
for tungsten I set it to 100keV (the default, if I am not mistaken). The
reason I increasing it in tungsten is I am not really interested in what
happens inside of the shielding, rather how many particles escape it.

If I understood slide 5 ("Production Thresholds" ) of the EM lecture
correctly, then the amount of energy lost per step by a primary particle
is the same regardless of the specified threshold. With the EMFCUT card
one just specifies if this energy is used to create delta rays, by
setting the threshold accordingly.
Is this correct? Will the spectrum of particles which make it past the
shielding be nearly unaffected by what the production threshold is set
to inside of the shielding?
I say "nearly" as a delta ray produced near the exiting surface of the
shielding will be able to make it out and the higher the threshold the
more energetic the delta rays (although I would imagine the probability
is also less for producing these).

Am I completely misunderstanding this?


P.S. In the manual for EMFCUT it says the FUDGEM parameter must be set
to 1 if the cutoff is larger than 100keV, yet on slide 6 the Heidelberg
EM presentation (and also that of 2009 and 2008) it says 10keV. Which
one is correct?
Received on Fri Apr 08 2011 - 07:40:19 CEST

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