Re: identifying the source of neutrons

From: Alberto Fasso <>
Date: Tue, 13 Oct 2009 23:55:39 +0200 (CEST)

Dear Lawrence,

you can tag the neutrons by one or more of the FLUKA user flags.
> From the manual:
 13.2.20} stupre.f SeT User PRoperties for EMF particles
          stuprf.f SeT User PRoperties for FLUKA particles

 These two functions are used to assign a value to one or more stack
 user variables when the corresponding particle is loaded into one of
 the stacks (FLKSTK for hadrons/muons, EMFSTK for electrons/photons,
 OPPHST for optical photons).
 In each of these stacks the user has access to one integer variable,
 one integer array and one double precision array. Each of them is
 copied to a correspondent variable or array in COMMON TRACKR at the
 beginning of transport:

          Correspondence: FLKSTK EMFSTK OPPHST TRACKR
          -------------- ----- ------ ------ ------
             integer variable: LOUSE LOUEMF LOUOPP --> LLOUSE
             integer array: ISPARK IESPAK ISPORK --> ISPUSR
             double precision array: SPAREK ESPARK SPAROK --> SPAUSR

 The user can access and modify the TRACKR variables via subroutine
 MGDRAW and its entries ENDRAW, SODRAW and especially USDRAW (see
 description above). STUPRF and STUPRE can be used to do the reverse,
 namely to copy TRACKR user variables to those of the relevant stack
 (see USDRAW above).
The default version of STUPRF copies to stack the user flags of the parent.
If you want to use as a flag only the region number where the neutrons
are produced, you need only one integer flag, LOUSE. If you want to flag
the birth coordinates, use 3 of the SPAREK floating-point flags.
The calling list of stuprf.f is IJ, MREG, XX, YY, ZZ, NPSECN, NPPRMR.
Edit it, for instance:
      IF ( IJ .EQ. 8 ) LOUSE = MREG
      IF ( IJ .EQ. 8 ) THEN
         SPAREK(1) = XX
         SPAREK(2) = YY
         SPAREK(3) = ZZ
      END IF
Then, when the neutron is transported or scored, you can find its region of
origin (or its coordinates of origin) in the TRACKR variable LLOUSE (or


On Tue, 13 Oct 2009, Lawrence Mhatiwa wrote:

> Dear Fluka Users
> I am scoring neutron spectrum in air in a sphere situated at the isocenter
> of a Linac.Is there a way in Fluka of identifying where these neutrons are
> coming from.I mean a way of tagging neutrons where they are produced.This is
> because i want to identify the relative contributions of all treatment
> head components towards the total photoneutrons scored at the isocenter.
> Please help
> Lawrence Mhatiwa
> Medical Physics Department
> University Of Free State
> South Africa
Received on Tue Oct 20 2009 - 19:01:02 CEST

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