AN ELECTRON BEAM IRRADIATOR IRRADIATES A PLASTIC CONTAINER (2) WITH AN ELECTRON BEAM EMITTED FROM AN ELECTRON BEAM IRRADIATING DEVICE (16) TO STERILIZE THE PLASTIC CONTAINER WHILE THE PLASTIC CONTAINER IS BEING SUPPORTED AND FED BY A CONTAINER GRIPPER (28) OF A CONTAINER FEEDER (20). AN ELECTRON TRAPPING MEMBER (60) IS INSERTED INTO THE PLASTIC CONTAINER THROUGH A MOUTH THEREOF. WITH THE ELECTRON TRAPPING MEMBER BEING PLACED IN THE PLASTIC CONTAINER, A CURRENT MEASURING UNIT (76) MEASURES A CURRENT FLOWING THROUGH THE ELECTRON TRAPPING MEMBER WHILE THE PLASTIC CONTAINER IS BEING IRRADIATED WITH THE ELECTRON BEAM, THEREBY MEASURING A DOSE OF ELECTRONS FROM THE ELECTRON BEAM WHICH HAS ENTERED THE PLASTIC CONTAINER TO ASCERTAIN WHETHER THE PLASTIC CONTAINER IS APPROPRIATELY STERILIZED OR NOT. FIG. 2
