Re: PEMF question

From: Alberto Fasso' (fasso@SLAC.Stanford.EDU)
Date: Wed May 11 2005 - 18:26:31 CEST

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    Giuseppe's answer is correct, but I would like to answer more directly
    the questions asked by Katherine.

    > > In using the EMF option can elements be defined with each element name
    > > also being in the file generated by the PEMF preprocessor and then can
    > > these elements be combined in a COMPOUND card and then linked with a
    > > MATERIAL card?

    No. In the present version of FLUKA, the COMPOUND command is used
    to prepare cross sections for hadrons and muons, but not for electrons and
    photons. (As Giuseppe said, it will be different in the next release).
    For electrons and photons, the "mixing" is done by PEMF via the commands
    COMP or MIXT in the .peg input file. The link to the FLUKA input file
    is done by the material name, which must be the same in in the .peg file
    and in the corresponding MATERIAL card.

    > > Or should one run the preprocessor for a mixture with the same name as
    > > the final MATERIAL card just using the total number of atoms for each
    > > element in the mixture of gasses.

    Yes. It is the user's responsibility to figure out the total number of
    atoms for each element.

    > > Or what is the proper way to use the EMF option with mixtures of gasses
    > > that are both element and compounds.

    For instance, let's suppose that you have a mixture of
    air, CO2 and water vapour, with weight proportions respectively A, B and C.
    You must declare a MIXT where the proportion of Oxygen is the weighted
    sum of that present in the 3 gases:

    A/(A+B+C) in air
    B*2*16/(12+2*16)/(A+B+C) in CO2 (2 Oxygen atoms of atomic weight 16 in a
                             molecule of molecular weight 12+2*16)
    C*16/(2*1+16)/(A+B+C) in H2O (1 Oxygen atom of atomic weight 16 in a molecule
                             of molecular weight 18)

    ==> A/(A+B+C) + B*2*16/(12+2*16)/(A+B+C) + C*16/(2*1+16)/(A+B+C)
        (I hope I did it right :-)

    Even when PEMF will have disappeared, it will be necessary to do the
    above exercise in the FLUKA input with the COMPOUND command. In principle
    it is possible to define a COMPOUND recursively ("compound of compounds"),
    but there are some restrictions in the normalization, and I always
    prefer to calculate the various fractions by hand myself.

    Alberto

    On Wed, 11 May 2005, Giuseppe Battistoni wrote:

    >
    > Dear Katherine,
    > the answer, if I understand correctly your question, is that one needs to
    > prepare PEMF only for the materials that you actually have in reality:
    > that means that if you a region filled, for instance, with AIR
    > (that you define as a gas mixture of N, O and AR) you must prepare the
    > PEMF for the mixture called AIR (giving inside the right parameters for
    > the 3 elements and the proper GASP pressure value). Instead you will not
    > prepare the PEMF for the individual elements N, O and AR.
    >
    > [Notice that his is not exactly parallel to what we do for the hadronic
    > cross section tabulation: in general in the FLUKA input we need to insert
    > the MATERIAL card both for the compound/mixture and card for all
    > individual elements in the compound/mixture]
    >
    > Be happy: the problem of creating PEMF is going to disappear in the next
    > FLUKA release!
    > Giuseppe
    >
    > On Wed, 11 May 2005, Katherine Harine wrote:
    >
    > > Date: Wed, 11 May 2005 08:21:04 -0500
    > > From: Katherine Harine <katherine.harine@msfc.nasa.gov>
    > > To: Alfredo Ferrari <Alfredo.Ferrari@cern.ch>,
    > > Giuseppe Battistoni <Giuseppe.Battistoni@mi.infn.it>,
    > > THOMAS L. WILSON <thomas.l.wilson@nasa.gov>
    > > Cc: fluka-discuss@fluka.org
    > > Subject: PEMF question
    > >
    > > In using the EMF option can elements be defined with each element name
    > > also being in the file generated by the PEMF preprocessor and then can
    > > these elements be combined in a COMPOUND card and then linked with a
    > > MATERIAL card?
    > >
    > > Or should one run the preprocessor for a mixture with the same name as
    > > the final MATERIAL card just using the total number of atoms for each
    > > element in the mixture of gasses.
    > >
    > > Or what is the proper way to use the EMF option with mixtures of gasses
    > > that are both element and compounds.
    > >
    > > If this is not clear, I'll put together an example.
    > >
    > >
    > > - Katherine
    > >
    >
    >

    -- 
    Alberto FassÚ
    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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