RE: [fluka-discuss]: problems of the COMPOUND card

From: Eleftherios Skordis <eleftherios.skordis_at_cern.ch>
Date: Fri, 21 Jul 2017 16:09:34 +0000

Dear Tao,

I hope these parts taken from the FLUKA manual are enough to answer your questions:

         5) If a compound is defined by volume fractions of the components
            (either elements or compounds themselves - see Note 8 below for
            recursive definitions), FLUKA internally calculates the atomic
            densities of each component using the densities indicated in the
            respective MATERIAL cards: in this case, therefore, (and only in
            this case), it is important that these correspond to the actual
            densities.


"Default (option MAT-PROP not given): if the density of the default
            material or that assigned by a MATERIAL card is > 0.01, the
            material is not assumed to be a gas. Otherwise it is a gas
            at a default pressure of 1 atmosphere. If the material is a
            compound, the average ionisation potential is that resulting
            from applying Bragg's rule of additivity to stopping power."

Furthermore as far as the material definition is concerned you should consider these when defining a MATERIAL card:

     WHAT(2) = NOT to be filled.
               It allows to overwrite the default value of atomic weight
               (in g/mole).
               Default: computed according to the natural composition of an
               element with atomic number WHAT(1) or to the identity of its
               isotope specified by WHAT(6).
               Meaningless if coupled to a COMPOUND card.

    WHAT(6) = mass number of the material
               Only integer values (still in real format) make sense.
               Default = 0 i.e. natural isotopic composition of the WHAT(1)
               element (but see Note 8).
               For isotopic composition other than natural or single isotope,
               see COMPOUND

Lastly there is no hard distinction in FLUKA between N2 and N.
In principle you could define a new compound material (N2) that contains Nitrogen with atomic weight 2. However you will not get any different results.

Kind regards

Lefteris


-----------------------

Eleftherios Skordis
Dep. EN/STI, CERN
CH-1211 GENEVA 23
SWITZERLAND

OFFICE: +41-22-7679541<tel:%2B41-22-7675461>
________________________________
From: owner-fluka-discuss_at_mi.infn.it [owner-fluka-discuss_at_mi.infn.it] on behalf of YANG Tao [yangt_at_ihep.ac.cn]
Sent: 21 July 2017 06:11
To: fluka-discuss_at_fluka.org
Subject: [fluka-discuss]: problems of the COMPOUND card


Hello Fluka's users,

I meet some confused problems about the COMPOUND card. When I define a gas mixture consist of 70%Ar gas +30% N2 gas,the ratios are in volume fractions as shown in figure1. I don't know the material"NITROGEN" I selected is nitrogen molecule(N2 and one molecule has two nitrogen atoms) or only nitrogen atom(nitrogen element, only one nitrogen atom). I think this is a common problemfor gas mixture definition. Could anyone explain it?

[cid:1532933f$2$15d63578923$Coremail$yangt$ihep.ac.cn]

Besides, I have another problem, When I define a compound, some elements(not the 25 pre-defined materials) would be defined in a MATERIAL card, as shown figure2, I don't know whether the density in the card is the one of its elementary substance or not, I think the density here may be not necessary, because one element could be de! termined by its Z and A, but density could be varied in some cases.


[cid:2b6117f8$4$15d63578923$Coremail$yangt$ihep.ac.cn]

Any help is appreciated!


Tao Yang

CAS

















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Received on Fri Jul 21 2017 - 21:15:38 CEST