I've been trying to inject a custom beam into MAUS using the icool003 format. It seems that everything works fine apart from the Json->Cpp conversion of the primaries.

MAUS expects all particles to have a Spin three vector in the json, while Xboa produces primary particles without this property. MAUS then (correctly) throws an exception.

I have fixed this in my development version by changing Spin to be an optional parameter in the Primary conversion class. I'm not sure that this is correct way to fix the issue however.

I have attached an example file that Victoria provided.