Sterilization device for sterilizing open packaging containers with electron beams, said sterilization device comprising a first chamber comprising at least one first electron beam emitter adapted for sterilization of at least the interior of the packaging container through an opening of the packaging container at least one second electron beam emitter adapted for sterilization of at least a portion of the exterior surface of said packaging container, the second electron beam emitter comprises a tubular body, which has an elongate shape along the longitudinal centre axis ( b), an electron exit window which provides an outlet for electrons from the vacuum inside the tubular body and a cathode, wherein an cloud (II;III) emitted from the at least one second electron beam emitter has a substantially circular cross section in a plane perpendicular to the longitudinal axis ( b) and a somewhat rectangular or rounded cross section in a plane parallel to the electron exit window, wherein said first chamber having an entry region towards a second chamber, through which entry region a packaging container portion, comprising said opening, is adapted to be passed for entrance into the second chamber, said at least one second electron beam emitter being arranged such that its electron exit window is at least substantially facing said entry region, said second electron beam emitter thereby being adapted to sterilize at least any exterior surface of the packaging container portion being passed through the entry region, and said at least one first electron beam emitter being arranged to sterilize the interior surface before or at the same time as said packaging container portion is entered into the second chamber, wherein the at least one second electron beam emitter is positioned such that the electron cloud (II; III) emitted from the at least one second electron beam emitter, during operation of the sterilization device, is adapted to form an irradiation barrier at least covering the entry region, and wherein an electron cloud emitted from the first electron beam emitter is adapted to temporarily meet and partly overlap the electron cloud (II; III) emitted from the at least one second electron beam emitter, said electron clouds together forming a combined electron cloud, and wherein the opening of the packaging container portion is at least temporarily positioned within the combined cloud. a first chamber comprising at least one first electron beam emitter adapted for sterilization of at least the interior of the packaging container through an opening of the packaging container at least one second electron beam emitter adapted for sterilization of at least a portion of the exterior surface of said packaging container, the second electron beam emitter comprises a tubular body, which has an elongate shape along the longitudinal centre axis ( b), an electron exit window which provides an outlet for electrons from the vacuum inside the tubular body and a cathode, wherein an cloud (II;III) emitted from the at least one second electron beam emitter has a substantially circular cross section in a plane perpendicular to the longitudinal axis ( b) and a somewhat rectangular or rounded cross section in a plane parallel to the electron exit window, wherein said first chamber having an entry region towards a second chamber, through which entry region a packaging container portion, comprising said opening, is adapted to be passed for entrance into the second chamber, said at least one second electron beam emitter being arranged such that its electron exit window is at least substantially facing said entry region, said second electron beam emitter thereby being adapted to sterilize at least any exterior surface of the packaging container portion being passed through the entry region, and said at least one first electron beam emitter being arranged to sterilize the interior surface before or at the same time as said packaging container portion is entered into the second chamber, wherein the at least one second electron beam emitter is positioned such that the electron cloud (II; III) emitted from the at least one second electron beam emitter, during operation of the sterilization device, is adapted to form an irradiation barrier at least covering the entry region, and wherein an electron cloud emitted from the first electron beam emitter is adapted to temporarily meet and partly overlap the electron cloud (II; III) emitted from the at least one second electron beam emitter, said electron clouds together forming a combined electron cloud, and wherein the opening of the packaging container portion is at least temporarily positioned within the combined cloud.