Re: Low energy neutron xsec not found for some media

From: Alberto Fasso' (fasso@SLAC.Stanford.EDU)
Date: Sat Apr 30 2005 - 01:12:39 CEST

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    I have looked more carefully at your input. The reason of your error is clear.
    The name "ARGON" is not aligned starting from column 71, and therefore the code
    does not find its cross sections because it has a blank space before the A.

    It is much easier to ensure proper alignment if you write your input like this:
    *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
    MATERIAL 18. 39.948 1.662E-3 26. ARGON
    MATERIAL 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
    *

    Alberto

    On Fri, 29 Apr 2005 adwasil@poczta.onet.pl wrote:

    >
    > 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
    >
    >

    -- 
    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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