From: Alberto Fasso' (fasso@SLAC.Stanford.EDU)
Date: Sat Apr 30 2005 - 00:57:08 CEST
I don't know if this is related to the problem you have, but it could be.
In your input there are several numbers written in exponential form
(for instance 1.662E-3) which are not aligned to the right of their
field. For other numbers (such as 1.848) it does not matter, but
standard fortran reads the above number as 1.662E-300, because there are two
blanks on its right side. This can produce very unexpected results.
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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