"Vacuum" is chosen as default material for each volume geometry but is not defined anywhere in GATE

[ThomasDeschler]

It is a real problem when the simulation contains only NIST materials and no external Material Database is used.

Causing this error: GateMaterialDatabase.cc (l.131): GateMaterialDatabase: could not find the definition for material 'Vacuum' in material

To solve this issue I propose to replace all the SetMaterialName("Vacuum") by SetMaterialName("G4_Galactic") defined in NIST materials.

[dsarrut]

Hi Tom, as we discuss : maybe rather check if Vacum does not exist, and replace by G4_Galactic in that case.

thanks, David

[dsarrut]

See #453