Hi Tao,
What you say is not fully correct.
When you use NITROGEN this points out to the predefined material (unless redefined with the same name in your input) default Nitrogen with density of 0.00117.
This is treated as a gas for all relevant physical processes.
If your gas is at different conditions then you have to redefine it with your own density keeping in mind that if its density is higher than 0.01 then you have to use an additional MAT-PROP card in order for FLUKA to consider it as gas.
FLUKA does not distinguish between N2 molecule and Nitrogen atom. It only cares if it is considered a gas or not.
When you define a compound by volume then the density of the material you are using is taking into consideration to calculate the atomic densities (fractions).
Otherwise if you define it by ATOM then you define yourself the atomic composition.
The density of the final compound will determine if it will be treated as a gas or not (unless you are using an extra MAT-PROP card).
Kind regards
Lefteris
-----------------------
Eleftherios Skordis
Dep. EN/STI, CERN
CH-1211 GENEVA 23
SWITZERLAND
OFFICE: +41-22-7679541<tel:%2B41-22-7675461>
________________________________
From: YANG Tao [yangt_at_ihep.ac.cn]
Sent: 21 July 2017 18:40
To: Eleftherios Skordis
Cc: fluka-discuss_at_fluka.org
Subject: Re: RE: [fluka-discuss]: problems of the COMPOUND card
Dear Eleftherios,
Thanks for your reply. So in your opinion, when the type of fraction I selected in the COMPOUND card is volume ratio, the "NITROGEN" is pointed to the N2 gas or N2 molecule, otherwise, the "NITROGEN" is pointed to the NITROGEN atom or element if I select the the ATOM or MASS option in the COMPOUND card.
Do I have an exact understanding?
Best regards!
Tao Yang
CAS
-----原始邮件-----
发件人: "Eleftherios Skordis" <eleftherios.skordis_at_cern.ch>
发送时间: 2017年7月22日 星期六
收件人: "YANG Tao" <yangt_at_ihep.ac.cn>, "fluka-discuss_at_fluka.org" <fluka-discuss_at_fluka.org>
抄送:
主题: RE: [fluka-discuss]: problems of the COMPOUND card
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<mailto:owner-fluka-discuss_at_mi.infn.it> [owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it>] on behalf of YANG Tao [yangt_at_ihep.ac.cn<mailto:yangt_at_ihep.ac.cn>]
Sent: 21 July 2017 06:11
To: fluka-discuss_at_fluka.org<mailto: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:21390dd0$1$15d6605d145$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:28b9e3ba$2$15d6605d145$Coremail$yangt$ihep.ac.cn]
Any help is appreciated!
Tao Yang
CAS
__________________________________________________________________________
You can manage unsubscription from this mailing list at
https://www.fluka.org/fluka.php?id=acc_info
- image/bmp attachment: 1.bmp
- image/bmp attachment: 2.bmp
Received on Sat Jul 22 2017 - 00:11:15 CEST
