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Question Water and Vacuum Problem 

Forum: Geometry
Date: 11 Mar, 2010
From: <Dr_Cards>

Hello All,

I am having some problems modifying the microdosimetry example in Geant 4.93.

I have tried changing the standard 1mm x 1mm x 1mm water block to a vacuum environment with a small water block at the center. However, my results indicate that the region surrounding the block is still being ionised as if it is made of water.

I made both regions a vacuum and it shows the alpha particles passing through the two volumes at the right positions. But when I change the water box from vacuum to water suddenly, the vacuum region surrounding the box starts to receive ionisation events from the particle starting point.

Here is my code:

void DetectorConstruction::DefineMaterials() {

  // Water is defined from NIST material database
  G4NistManager * man = G4NistManager::Instance();
  G4Material * H2O = man->FindOrBuildMaterial("G4_WATER");
  G4Material * vacuum = man->FindOrBuildMaterial("G4_Galactic");

  // Default materials in setup.
  waterMaterial = H2O;
	voidmaterial = vacuum;

}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... G4VPhysicalVolume* DetectorConstruction::ConstructDetector() {

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....

  // WORLD VOLUME

  WorldSizeX  = 1*m; 
  WorldSizeY  = 1*m; 
  WorldSizeZ  = 1*m;

  solidWorld = new G4Box("World",				     //its name
			   WorldSizeX/2,WorldSizeY/2,WorldSizeZ/2);  //its size

  logicWorld = new G4LogicalVolume(solidWorld,	        //its solid
				   voidmaterial,	//its material
				   "World");		//its name

  physiWorld = new G4PVPlacement(0,			//no rotation
  				 G4ThreeVector(0*cm,0*cm,0*cm),	//at (0,0,0)
                                 "World",		//its name
                                 logicWorld,		//its logical volume
                                 NULL,			//its mother  volume
                                 false,			//no boolean operation
                                 0);			//copy number
//My Volume	

	SolidBox = new G4Box("Box",				     //its name
						   1*cm/2,1*cm/2,1*cm/2);  //its size

	logicBox = new G4LogicalVolume(SolidBox,	        //its solid
									 waterMaterial,	//its material
									 "Box");		//its name

	physiBox = new G4PVPlacement(0,			//no rotation
								   G4ThreeVector(0*cm,0*cm,0*cm),	//at (0,0,0)
								   logicBox,		//its name
								   "Box",		//its logical volume
								   logicWorld,			//its mother  volume
								   false,			//no boolean operation
								   0);			//copy number

Any advice would be greatly appreciated.

Thanks

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1 None: Re: Water and Vacuum Problem   (Sebastien INCERTI - 11 Mar, 2010)
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