Re: Low-mat option

From: Alberto Fasso' <fasso_at_SLAC.Stanford.EDU>
Date: Thu, 1 Aug 2013 05:14:56 -0700 (PDT)

No, Chenyuan, I am sorry: you don't understand what I am saying.

If a material is a low-energy neutron material, there is no need of LOW-MAT.
Read carefully in the Manual the Notes to command LOW-MAT:
           2) Option LOW-MAT should be avoided if it is not really necessary
              (experience has shown that it is often misinterpreted by beginner
              users). The option is NOT REQUIRED if the following 3 conditions
              are all true:
               i) the low-energy neutron material desired is unique or is
                  listed before any other material with the same name in
                  list 10}
                                        and
              ii) that name is the same as one in the FLUKA list (see 5}) or as
                  given by a MATERIAL option
                                        and
             iii) there is only one FLUKA material associated with that
                  low-energy neutron material

In your input file, both CARBON and ALUMINUM are low-energy neutron materials,
and both are used at room temperature.
Look in 10.4.1.2}:
   C Free gas natural Carbon 296K ENDF/B-VIIR0 Y CARBON 6 -2 296 Y
   C Free gas natural Carbon 87K ENDF/B-VIIR0 Y CARBON 6 -2 87 Y
   C Free gas natural Carbon 4K ENDF/B-VIIR0 Y CARBON 6 -2 4 Y
   C Free gas natural Carbon 430K ENDF/B-VIIR0 Y CARBON 6 -2 430 Y
   C Graphite bound nat. Carbon 296K ENDF/B-VIIR0 Y CARBON 6 -3 296 Y
................................................................................
27Al Aluminium 27 296K ENDF/B-VIIR0 Y ALUMINUM 13 27 296 Y
27Al Aluminium 27 87K ENDF/B-VIIR0 Y ALUMINUM 13 27 87 Y
27Al Aluminium 27 4K ENDF/B-VIIR0 Y ALUMINUM 13 27 4 Y
27Al Aluminium 27 430K ENDF/B-VIIR0 Y ALUMINUM 13 27 430 Y
27Al Aluminium 27 SelfShielded 296K ENDF/B-VIIR0 Y ALUMINUM 13 1027 296 Y
27Al Aluminium 27 SelfShielded 87K ENDF/B-VIIR0 Y ALUMINUM 13 1027 87 Y
27Al Aluminium 27 SelfShielded 4K ENDF/B-VIIR0 Y ALUMINUM 13 1027 4 Y
27Al Aluminium 27 SelfShielded 430K ENDF/B-VIIR0 Y ALUMINUM 13 1027 430 Y

The first material listed with the name CARBON is:
   C Free gas natural Carbon 296K ENDF/B-VIIR0 Y CARBON 6 -2 296 Y

and the first with the name ALUMINUM is:
27Al Aluminium 27 296K ENDF/B-VIIR0 Y ALUMINUM 13 27 296 Y

If these are the materials you want, LOW-MAT is not needed. It is not an
error to have a LOW-MAT, but because it is not necessary, it is easy to make a
mistake (see te warning in Note 2) above!)

It is needed, instead, if you need one of those who are not first.

So, in your input there was not a need for LOW-MAT. You put it there, however,
and you made a mistake!
LOW-MAT CARBON 13. 27. 296. ALUMINUM
which would mean: "Use for Carbon the cross sections of Aluminum"!!!!!!!!!
which is obviously meaningless.

Alberto


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

> Good morning,
>
> Indeed,I understand what you said,Alberto.
>
> In this input file,There are two materials.Both of them are Fluka materials and low-mat neutron materials.
>
> When two materials are both Fluka materials and low-mat neutron materials,in the low-mat option,
>
> which should be assigned the Fluka material,which should be assigned the low-mat neutron material.
>
> At last,Is there any problem in my input file?
>
> Best wishes,
>
> Chenyuan
Received on Thu Aug 01 2013 - 15:05:35 CEST