The dault value of the /gps/pos/confine command is NULL. If I execute the command with a specific volume, it works fine. But, it is impossible to annul the command after an execution: "/gps/pos/confine NULL" doesn't work beacuse "no NULL volume is defined".
Thanks for reporting this bug. It will be fixed very soon and the fix will be included in Geant4 version 10.7. Makoto Asai
Thanks once again for reporting this issue. Actually "/gps/pos/confine NULL" properly sets off the confinement option, but with the wrong error message of "Volume does not exist". This is absolutely misleading. This incorrect message is fixed and the fix will be included in the coming release. Meanwhile, please ignore the error message. Kind regards, Makoto