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Forum: Geometry
Re: Question overwrite density using NIST database (Leila Moghadasi)
Date: 19 Jul, 2012
From: Youming Yang <Youming Yang>

In reverse order:

To access the NIST database, section 2.3.5 of the Geant4 Application Developer's manual states:

2.3.5. Define a Material from the Geant4 Material Database

In the example below, air and water are accessed via the Geant4 material database.

Example 2.9. Defining air and water from the internal Geant4 database.

  G4NistManager* man = G4NistManager::Instance();

  G4Material* H2O  = man->FindOrBuildMaterial("G4_WATER");
  G4Material* Air  = man->FindOrBuildMaterial("G4_AIR");

Probably the most straightforward way to build an inflated lung from deflated composition with only a density change, from the Geant4 manual (ch2 section 3, 2.3.6):

2.3.6. Define a Material from the Base Material

It is possible to build new material on base of an existing "base" material. This feature is useful for electromagnetic physics allowing to peak up for the derived material all correction data and precomputed tables of stopping powers and cross sections of the base material. In the example below, two methods how to create water with unusual density are shown.

Example 2.10. Defining water with user defined density on base of G4_WATER.

  G4double density;

  density = 1.05*mg/cm3;
  G4Material* water1 = new G4Material("Water_1.05",density,"G4_WATER");

  density = 1.03*mg/cm3;
  G4NistManager* man = G4NistManager::Instance();
  G4Material* water2 = man->BuildMaterialWithNewDensity("Water_1.03","G4_WATER",density);

On Fri, 20 Jul 2012 03:55:51 GMT, Leila Moghadasi wrote:

> Hi Geant4 users I am trying to declare lung tissue using NIST database.
> I checked the density of G4_LUNG_ICRP (=1.05 gr/cm^3) which is not what
> I want. I appreciate if anyone could tell me if there is a way that I
> could declare G4_LUNG_ICRP with density of 0.2gr/cm^3 or I should go for
> manual definition of lung through G4Material? Moreover, how I can access
> the NIST database, if at all possible?
> Many thanks 

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1 Ok: Re: overwrite density using NIST database   (Leila Moghadasi - 20 Jul, 2012)
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