:P POSX 8.
:P A_H 1.00797 
:P A_O 15.9994

// Define single elements
:ELEM Hydrogen H 1. $A_H

// Define elements from isotopes
:ISOT N 7 14 14.0031 
:ISOT N_2 7 15 15.0001 
:ELEM_FROM_ISOT Nytrogen N 2
   N 0.99632
   N_2 0.00368

:ISOT O 8 16 15.9949 
:ISOT O_2 8 17 16.9991 
:ISOT O_3 8 18 17.9992 
:ELEM_FROM_ISOT Oxygen O 3
   O 0.99757
   O_2 0.00038
   O_3 0.00205

// Define single material 
:MATE Hydrogen 1 1. 8.37480e-5

// Define material mixtures
// Define material mixture of elements by weight 
:MIXT WaterW_EE 1. 2   // Use Hydrogen element built here and Oxygen element from GEANT4 NIST
   Hydrogen  2.*$A_H/(2.*$A_H+$A_O)
   O      $A_O/(2.*$A_H+$A_O)

// Define material mixture of element and material by weight 
:MIXT WaterW_EM 1. 2 // Use Hydrogen element built here and Oxygen material from GEANT4 NIST
   Hydrogen  2.*$A_H/(2.*$A_H+$A_O)
   G4_O      $A_O/(2.*$A_H+$A_O)

// Define material mixture of elements by number of atoms
:MIXT_BY_NATOMS WaterNA 1 2
   Hydrogen   2
   Oxygen     1

// Define material mixture of material mixtures
:MIXT_BY_NATOMS  CO2  1.8182E-3  2
   C  1 
   O  2

:MIXT_BY_VOLUME H-CO2 (1.214E-03+1.8182E-3)/2. 2 // Use Hydrogen material (MIXT_BY_VOLUME does not use elements)
   Hydrogen 0.5
   CO2 0.5


// Use materials (if a material is not used it will not be created as a Geant4 object)
:ROTM R00 90. 0. 90. 90. 0. 0.

:VOLU world BOX 100. 100. 100. WaterW_EE

:VOLU "my tube" TUBS 0. 10. 20. 0. 360. WaterW_EM
:PLACE "my tube" 1 world R00 0. 0. $POSX

:VOLU sphere ORB 5.  WaterNA
:PLACE sphere 1 "my tube" R00 0. 1. $POSX

:VOLU sphere2 ORB 5.  H-CO2
:PLACE sphere2 1 "my tube" R00 0. 1. -$POSX

// Switch on overlap checking for all volumes
:CHECK_OVERLAPS * ON