Re: question about photonuclear interaction

From: Alberto Fasso' (Alberto.Fasso@cern.ch)
Date: Mon Feb 24 2003 - 14:13:53 CET


Dear Zhen Wu,

when asking for a neutron spectrum with options USRBDX, USRTRACK and
USRCOLL, it is necessary to set the upper energy limit LARGER than 0.0196 GeV.
You have set it EQUAL to 0.0196 GeV, and that is why you get an error.
We apologize, because the manual is not clear on this point (we will correct it
soon).

Some other remarks about your input, unrelated with the above problem:
1) WHAT(4) in the PHOTONUC card must be the material index, not the atomic
   number (in your case, 23 and not 74)
2) On option LOW-DOWN, the manual contains the following warning:
   "Very powerful but also very dangerous, can lead to errors of orders of
   magnitude if not used by experts"
   It is true that in your input LOW-DOWN is given with WHAT(1) = 0.0,
   therefore it will do nothing. But in case you plan to switch it on, please
   make sure that you know well what you are doing. It is not a command
   recommended for a beginner!
3) In option LOW-MAT, WHAT(1) is the material index, not the atomic number
   (same error as in PHOTONUC above, so it must be 23, not 74). But there is no
   need at all to have a LOW-MAT card here, since the defaults are exactly
   what you want. The manual says: "Option LOW-MAT should be avoided if it is
   not really necessary (experience has shown that it is often misinterpreted
   by beginner users)".
4) Also LOW-NEUT is redundant here, since its parameters coincide with the
   defaults.

Best regards,

   Alberto

On Sun, 23 Feb 2003, wuzhen wrote:

> Dear Fluka users,
> As you know, when the energy of the electron beam above about 10Mev, if
> it hits the tungsten target, the photonuclear interactions will occur between
> the electrons (or the produced photons) with and the target nucleus.
> Photoneutron will be produced. I want to get the fluence distribution of
> photon in the distance of 1 cm. The following is my input file and result. Can
> anyone tell me where does the errors occur? Why linear energy binning is from
> 1.9600E-02 to 1.9600E-02 GeV, although I have defined the linear energy is
> from 0 to 1.9600E-02 Gev in the card of "USRBDX"? And in the standard output
> file, i find the cut-off kinetic energy for NEUTRON transport is 1.960E-02
> GeV. Where can i change it? Any help will be appreciated!
>
> Best wishes!
>
> Zhen Wu
>
> 02/23/2003
>
> Input file:
>
> TITLE
> Testing fluka: Beam of electron through tungstEn target
> DEFAULTS NEW-DEFA
> *---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----*
> BEAM -1.5E-2 0.0 0.0 0.0 0.0 1.0ELECTRON
> BEAMPOS 0.0 0.0 -1.0
> GEOBEGIN 0.0 COMBINAT
> outer sphere and tungsten target
> *---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----*
> RPP 1 -10.0 10.0 -10.0 10.0 -10.0 10.0
> SPH 2 0.0 0.0 0.0 1.0
> RCC 3 0.0 0.0 -0.06 0.0 0.0 0.12
> 0.5
> END
> *---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----*
> BL1 4 +1 -2
> VA2 7 +2 -3
> TU3 7 +3
> END
> GEOEND
> *---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----*
> MATERIAL 74.0 184.0 19.3 23.0 0.0 0.0TUNGSTEN
> LOW-MAT 74.0 74.0 -2.0 293.0 TUNGSTEN
> *---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----*
> ASSIGNMA 1.0 1.0
> ASSIGNMA 2.0 2.0
> ASSIGNMA 23.0 3.0
> *---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----*
> PHOTONUC 1111. 74.0
> *---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----*
> LOW-NEUT 72.0 22.0 1.96E-2 0.0 1.0 0.0
> LOW-BIAS 0.0 72.0 0.85 1.0 3.0 1.0
> LOW-DOWN 0.0 1.5 1.0 3.0 1.0
> *---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----*
> OUTLEVEL 1.0 7.0
> *---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----*
> USRBDX 1.0 8.0 48.0 2.0 1.0 1.0Neutrons
> USRBDX 1.96E-2 0.0 72.0 &
> RANDOMIZ 1.0
> START 10000.0 9999999.
> STOP
>
>
>
> Result:
> ***** Testing fluka: Beam of electron through tungstEn target *****
>
> DATE: 2/23/ 3, TIME: 19:58:10
>
> Total number of particles followed 10000, for a total weight of 1.0000E+04
>
> 1
>
> Bdrx n. 1 "Neutrons " , generalized particle n. 8, from region n. 2 to region n. 1
> detector area: 1.0000E+00 cm**2
> low energy neutrons scored from group 1 to group 72
> this is a one way only estimator
> this is a current like estimator
> linear energy binning from 1.9600E-02 to 1.9600E-02 GeV, 0 bins ( 1.5503E-03 GeV wide)
> linear angular binning from 0.0000E+00 to 6.2832E+00 sr , 1 bins ( 6.2832E+00 sr wide )
> Data follow in a matrix A(ie,ia), format (1(5x,1p,10(1x,e11.4)))
>
>
>
>
> Low energy neutron data from group 1 to group 72 follow in a matrix A(ig,ia), format (1(5x,1p,10(1x,e11.4)))
>
> 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00
> 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00
> 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00
> 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00
> 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00
> 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00
> 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00
> 0.0000E+00 0.0000E+00
>
>
>

-- 
Alberto FassÚ
CERN-EP/AIP, CH-1211 Geneve 23 (Switzerland)
Phone: (41 22) 767 2398    Fax: (41 22) 767 9480   Alberto.Fasso@cern.ch


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