30   G4Material* Vacuum = 
new G4Material(
"interGalactic", 1., 1.008*
g/mole,1.e-25*
g/cm3, kStateGas,2.73*kelvin, 3.e-18*pascal);
 
   32   G4LogicalVolume* lExpHall = 
new G4LogicalVolume(gExpHall,Vacuum,
"lExpHall",0,0,0);
 
   33   G4VPhysicalVolume* wExpHall  = 
new G4PVPlacement(0,G4ThreeVector(),lExpHall,
"gExpHall",0,
false,0);