Low energy neutron xsec not found for some media

From: adwasil@poczta.onet.pl
Date: Fri Apr 29 2005 - 08:49:55 CEST

  • Next message: Giuseppe Battistoni: "Air"

    I've defined AIR material myself. But something is still not correct. I've obtained a massage **** Low energy neutron xsec not found for some media 4 5 ****. I think all used materials such as NITROGEN, OXYGEN, ARGON and CARBON are defined in FLUKA neutron library. Should I switch some option/command on to use cross section of these elements for compound (AIR)?
    What am I still 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
    *---o---- ----1---- ----2---- ----3---- ----4---- ----5---- ----6---- ----7----
    * 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 18. 39.948 1.662E-3 26. ARGON
    MATERIAL 0. 0. 0.0012048 24. AIR
    COMPOUND -9.1E-4 7. 2.79E-4 8. 1.55E-5 26. AIR
    COMPOUND 1.49E-7 6. AIR
    *
    *---o---- ----1---- ----2---- ----3---- ----4---- ----5---- ----6---- ----7----
    *
    *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

    On Thu, 28 Apr 2005, 20:10 Alberto Fasso wrote
    > 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


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