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Forum: Geometry
Re: None NIST Material vs G4Material (Jérôme Roccaz)
Re: None Re: NIST Material vs G4Material (michel maire)
Date: 23 Apr, 2012
From: Jérôme Roccaz <Jérôme Roccaz>

On Mon, 23 Apr 2012 16:39:13 GMT, michel maire wrote:
> On Mon, 23 Apr 2012 11:42:46 GMT, J&#65533;r&#65533;me Roccaz wrote:
> > Hi everyone,
> > 
> > I'm using the defined NIST G4_POLYETHYLENE as neutron moderator
> > material. As I want to modify this material, I've first tested building
> > my own polyethylene with G4Element and using data in Geant4 User's guide
> > like this :
> > 
> > density = 0.94*g/cm3; G4Material* PEHDtest = new
> > G4Material(name="PEHDtest", density, ncomponents=2);
> > PEHDtest->AddElement(elH, fractionmass=0.143711);
> > PEHDtest->AddElement(elC, fractionmass=0.856289);
> > PEHDtest->GetIonisation()->SetMeanExcitationEnergy(57.4*eV);
> > 
> > When I compare results with both material definitions, they are slightly
> > different. Do I miss something in my own definition?
> > 
>   Which differences are you speaking about ?

I've buit a PEHD ball in the center of which I have a neutron point source. I print out neutron and gamma spectra in order to calculate dose rate. Dose rate result is different, depending on PEHD definition

> 
>  By default, Nist construtor build isotopes composition, AddElement not (until 9.5)
>  For hadronic interaction, it could make differences. Not for EM interactions.
> 

I use hadronic interaction so ... As a conclusion, I should use NIST constructor. As I want to add other element, like boron to my PEHD, I should use both NIST definition for PEHD and Boron and then build the material, right?

By the way, for a gaz mixture like Ar + N2 in ionization chamber, better is to use NIST or G4Element so to have "more realistic" ionization results?

best regards,

Jerome

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1 None: Re: NIST Material vs G4Material   (michel maire - 24 Apr, 2012)
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