// Define a parameter for later use :P POSZ 5. // Define materials :ELEM Hydrogen H 1. 1. :ELEM Oxygen O 8 16. :ELEM Nitrogen N 7 14. :MIXT Air 1.214E-03 2 Nitrogen 0.75 Oxygen 0.25 // Define rotation matrix :ROTM R00 90. 0. 90. 90. 0. 0. // unit matrix // Define volumes and place them :VOLU world BOX 30. 30. 30. Air :VOLU "my tube" TUBS 0. 10. 20. 0. 360. G4_WATER :PLACE "my tube" 1 world R00 0. 0. $POSZ :VOLU sphere ORB 5. G4_AIR :PLACE sphere 1 "my tube" R00 0. 1. 10.