Re: Re: Low-mat option

From: Alberto Fasso' <fasso_at_slac.stanford.edu>
Date: Wed, 31 Jul 2013 04:45:38 -0700 (PDT)

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Dear Chen yuan,

please keep the discussion on the fluka-discuss list. Don't send me questions
privately.

I thought that your own input file and my previous answer were clear:
we need the LOW-MAT option for one or more of the reasons explained in
Note 3 of the Manual to LOW-MAT:

        3) ...the option IS REQUIRED in any one of the following cases:
            i) there is more than one low-energy neutron material with
               that name (this can happen because of data sets coming
               from different sources, or corresponding to different
               neutron temperatures, or concerning different isotopes, or
               weighted on different spectra, etc), and the one desired
               is not coming first in the list. In this case it is
               sufficient to provide just as many identifiers as required
               to remove ambiguity
                                     or
           ii) The FLUKA name is different from the name of the
               low-energy neutron material
                                     or
          iii) There is more than one FLUKA material associated with the
               given low-energy neutron material. This can happen for
               instance when the same material is present with different
               densities in different regions. In reality this is a
               special case of 2) above, since to distinguish between the
               different densities, different names must be used and one
               at least will not be equal to the name of the
               low-energy neutron material. [THIS WAS YOUR CASE]

Alberto


On Wed, 31 Jul 2013, yyc2011_at_mail.ustc.edu.cn wrote:

> Dear Alberto,
>
> Thanks for your reply and your suggestions.
>
> In fact,I don't know the function of the low-mat option.In other words,Why do
> we need the low-mat option?
>
> Best wishes,
>
> Chen yuan
>
>
>
>
>> -----Original E-mail-----
>> From: "Alberto Fasso'" <fasso_at_slac.stanford.edu>
>> Sent Time: 2013-7-31 17:36:40
>> To: "fluka-discuss_at_fluka.org" <fluka-discuss_at_fluka.org>
>> Cc: "yyc2011_at_mail.ustc.edu.cn" <yyc2011_at_mail.ustc.edu.cn>
>> Subject: Re: Low-mat option
>>
>> Dear Chen yuan,
>>
>> it looks to me that you have perfectly understood the the low-mat option.
>> In your input file, you have two materials: CARBON and GRAPHITE.
>> CARBON is a Fluka material (pre-defined) and also a low-energy neutron material
>> (as you can see in Chapter 10 of the Manual). On the other hand, GRAPHITE
>> is also a Fluka material (defined by you with a MATERIAL card), but it is not a
>> low-energy neutron material (there is no material called GRAPHITE in the list
>> of Chapter 10). Therefore, you must tell the program to use for GRAPHITE the
>> CARBON low-energy neutron material. And you did it correctly with the LOW-MAT
>> command.
>>
>> I take this opportunity to suggest to you two things. In command MATERIAL:
>> 1) leave WHAT(2) blank, or equal to 0.0. This is because FLUKA has its own
>> table of atomic weights and you better not change them
>> 2) leave WHAT(4) blank, or equal to 0.0. Since you are using a name-based
>> input, FLUKA takes care of assigning the proper number to materials.
>> Your input is correct, but leaving the material number blank you can avoid
>> possible problems.
>>
>> Best regards,
>>
>> Alberto
>>
>> On Tue, 30 Jul 2013, yyc2011_at_mail.ustc.edu.cn wrote:
>>
>>> Good morning,
>>>
>>> I am a beginner user of fluka. I can't fully understand low-mat option.
>>> In the low-mat option, How to distinguish Fluka material and
>>> corresponding low-energy neutron material? Could you give me a detailed
>>> explain? Or could you give me a simple example to help me understand low-mat
>>> option? The attachment is my input file.Is there any problem?
>>>
>>> Best wishes,
>>> Yours,
>>> Chen yuan
>
>

-- 
Alberto Fasso`
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Phone: (1 650) 926 4762   Fax: (1 650) 926 3569
fasso_at_slac.stanford.edu
Received on Wed Jul 31 2013 - 15:25:24 CEST

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