Re: Low energy neutron xsec not found for some media

From: Alberto Fasso' (fasso@SLAC.Stanford.EDU)
Date: Thu Apr 28 2005 - 20:10:58 CEST

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    FLUKA neutron cross sections are for single elements or isotopes, not for
    compounds and mixtures. The error message is due to the fact that no cross
    section with a name AIR* can be found in the neutron library.
    But this just one of many reasons why pre-defined compound materials
    (those with a * in their name) should NEVER be used. They are there for
    historical reasons, but their use can give problems, or at least
    inaccurate results. I hope that they will disappear in the next FLUKA release.

    Alberto

    On Thu, 28 Apr 2005 adwasil@poczta.onet.pl wrote:

    >
    > I try to find a difference in neutron transport in vacuum and air. that While
    > I'm using vacuum instead of air everything is OK, but wile I'm using fluka
    > material 24 I obtain an error massage **** Low energy neutron xsec not found
    > for some media 1 2 ****.
    > What am I doing wrong?
    > Best regards
    > Adam
    >
    > file.inp:
    > TITLE
    > Electron to photon to neutron on tungsten
    > DEFAULTS PRECISIO
    > *23456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
    > BEAM -0.007 ELECTRON
    > BEAMPOS 0. 0. -30. 0. 0.
    > EVENTYPE 2. DPMJET
    > GEOBEGIN COMBINAT
    > geometry definition
    > SPH 1 0. 0. 0. +9000000.
    > RPP 2-1000000. +1000000. -1000000. +1000000. -1000000. +1000000.
    > SPH 3 0. 0. 0. +100.
    > RCC 4 0. 0. -3.5 0. 0. 7.
    > 10.
    > RPP 5 -20. +20. -20. +20. +100.1 +100.2
    > END
    > * black hole region
    > 1 5 +1 -2
    > * vacuum around (outer)
    > 2 5 +2 -3 -5
    > * air around (inner)
    > 3 5 +3 -4
    > * tungsten target region (7cm thick, 10cm radius)
    > 4 5 +4
    > * forward detector region
    > 5 5 +5
    > END
    > GEOEND
    > *23456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
    > * Z Mass Dens[g/cm3] Index Not.used Name
    > *MATERIAL 74. 184. 19.3 23. TUNGSTEN
    > *MATERIAL 4. 9.0122 1.848 5. BERYLLIU
    > *MATERIAL 7.2 14.4 0.00129 24. AIR*
    > *
    > *23456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
    > *
    > *ASSIGNMAT (material==>region)
    > * tungsten target
    > ASSIGNMAT 23. 4.
    > * forward detector region
    > ASSIGNMAT 24. 5.
    > * Outer vacuum
    > ASSIGNMAT 2. 2.
    > * Inner air
    > ASSIGNMAT 24. 3.
    > * External Black Hole
    > ASSIGNMAT 1. 1.
    > PHOTONUC 1. 0. 0. 4. 24. 1.
    > LAM-BIAS 0. 0.00005 0. 7.
    > *23456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789
    > *---o---- ----1---- ----2---- ----3---- ----4---- ----5---- ----6---- ----7----
    > *EMF EMF-OFF
    > * **** Scoring ****
    >
    > USRBDX +1. 7. -31. 3. 2. PHOTON
    > USRBDX +0.02 300. 1. &
    > USRBDX +1. 3. -32. 3. 2. ELECTRON
    > USRBDX +0.02 300. 1. &
    > USRBDX +1. 8. -33. 3. 2. NEUTRON
    > USRBDX +0.02 +1.E-5 300. 1. &
    > *---o---- ----1---- ----2---- ----3---- ----4---- ----5---- ----6---- ----7----
    > USRBDX +1. 7. -41. 5. 2. PHOTON
    > USRBDX +0.02 300. 1. &
    > USRBDX +1. 3. -42. 5. 2. ELECTRON
    > USRBDX +0.02 300. 1. &
    > USRBDX +1. 8. -43. 5. 2. NEUTRON
    > USRBDX +0.02 +1.E-5 300. 1. &
    > RANDOMIZE 1.
    > *---o---- ----1---- ----2---- ----3---- ----4---- ----5---- ----6---- ----7----
    > START 50. 1.0
    > STOP
    >
    > 

    -- 
Alberto Fassò
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Phone: (1 650) 926 4762   Fax: (1 650) 926 3569
fasso@slac.stanford.edu
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