[Halld-offline] [EXTERNAL] Re: Question concerning one material definition in hdgeant

[Richard T. Jones]

Eugene,

Yes it is strange. Looking back through the logs, I see that this material
CarbonFiberEpoxy was introduced by me back in May, 2007, and it had this
redundant CarbonFiber component from the start. With this apparent
duplication of the carbon fiber component, here is what the material
description looks like in G4:

Idle> /material/g4/printMaterial CarbonFiberEpoxy
 Material: CarbonFiberEpoxy    density:  1.910 g/cm3   RadL:  22.245 cm
Nucl.Int.Length:  41.172 cm
                       Imean:  77.577 eV   temperature: 293.15 K  pressure:
  1.00 atm

   --->  Element: Carbon (C)   Z =  6.0   N =    12   A = 12.011 g/mole
         --->  Isotope:   C12   Z =  6   N =  12   A =  12.00 g/mole
abundance: 98.930 %
         --->  Isotope:   C13   Z =  6   N =  13   A =  13.00 g/mole
abundance:  1.070 %
          ElmMassFraction:  94.01 %  ElmAbundance  79.47 %

   --->  Element: Hydrogen (H)   Z =  1.0   N =     1   A =  1.008 g/mole
         --->  Isotope:    H1   Z =  1   N =   1   A =   1.01 g/mole
abundance: 99.989 %
         --->  Isotope:    H2   Z =  1   N =   2   A =   2.01 g/mole
abundance:  0.011 %
          ElmMassFraction:   1.77 %  ElmAbundance  17.85 %

   --->  Element: Oxygen (O)   Z =  8.0   N =    16   A = 15.999 g/mole
         --->  Isotope:   O16   Z =  8   N =  16   A =  15.99 g/mole
abundance: 99.757 %
         --->  Isotope:   O17   Z =  8   N =  17   A =  17.00 g/mole
abundance:  0.038 %
         --->  Isotope:   O18   Z =  8   N =  18   A =  18.00 g/mole
abundance:  0.205 %
          ElmMassFraction:   4.22 %  ElmAbundance   2.68 %

Here is what it produces if I remove the redundant CarbonFiber entry:

Idle> /material/g4/printMaterial CarbonFiberEpoxy
 Material: CarbonFiberEpoxy    density:  1.746 g/cm3   RadL:  24.266 cm
Nucl.Int.Length:  44.540 cm
                       Imean:  75.646 eV   temperature: 293.15 K  pressure:
  1.00 atm

   --->  Element: Carbon (C)   Z =  6.0   N =    12   A = 12.011 g/mole
         --->  Isotope:   C12   Z =  6   N =  12   A =  12.00 g/mole
abundance: 98.930 %
         --->  Isotope:   C13   Z =  6   N =  13   A =  13.00 g/mole
abundance:  1.070 %
          ElmMassFraction:  90.41 %  ElmAbundance  69.94 %

   --->  Element: Hydrogen (H)   Z =  1.0   N =     1   A =  1.008 g/mole
         --->  Isotope:    H1   Z =  1   N =   1   A =   1.01 g/mole
abundance: 99.989 %
         --->  Isotope:    H2   Z =  1   N =   2   A =   2.01 g/mole
abundance:  0.011 %
          ElmMassFraction:   2.84 %  ElmAbundance  26.14 %

   --->  Element: Oxygen (O)   Z =  8.0   N =    16   A = 15.999 g/mole
         --->  Isotope:   O16   Z =  8   N =  16   A =  15.99 g/mole
abundance: 99.757 %
         --->  Isotope:   O17   Z =  8   N =  17   A =  17.00 g/mole
abundance:  0.038 %
         --->  Isotope:   O18   Z =  8   N =  18   A =  18.00 g/mole
abundance:  0.205 %
          ElmMassFraction:   6.75 %  ElmAbundance   3.92 %

Idle>

So it seems like the duplicate entry increases the absorption by about 10%,
which may be significant for some reactions. That does not mean either one
is correct in terms of the description of the actual downstream endpolate.
All of these properties should be reviewed, and some may need updating.

-Richard Jones

On Thu, Mar 26, 2026 at 10:51 AM Eugene Chudakov <gen at jlab.org> wrote:

> *External sender: This message was not sent through the UConn email
> system. It might be safe, but use caution before interacting with links,
> attachments, or requests.*
>
> Hi Richard,
>
> For the CDC endplate a material definition in  Material_HDDS.xml is:
>
>  <composite name="CarbonFiberEpoxy">
>         <addmaterial material="CarbonFiber">
>                 <fractionmass   fraction="0.60" />
>         </addmaterial>
>         <addmaterial material="EpoxyResin">
>                 <fractionmass   fraction="0.40" />
>         </addmaterial>
>         <addmaterial material="CarbonFiber">
>                 <fractionmass   fraction="0.60" />
>         </addmaterial>
>   </composite>
>
> I asked Simon about the duplication and he found it strange. What mixture
> does it define?
>
> Thanks,
> Eugene
>
>
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