Electron exit window foil

#The present invention refers to an electron exit window foil. More particularly, the present invention relates to an electron exit window foil for use in a corrosive environment and operating at a high performance.

#Electron beam devices may be used to irradiate objects with electrons, e.g. for surface treatment. Such devices are commonly used within the food packaging industry, where electron beams are providing efficient sterilization of packages, e.g. plastic bottles or packaging material to be later converted into a package.

#A main advantage with electron beam sterilization is that wet chemistry, using e.g. H2O2, may be avoided thus reducing the high number of components and equipment required for such wet environments.

#In the following, exemplary embodiments of the invention will be described in greater detail, with reference to the enclosed drawings, in which:

#FIG. 1 is a schematic cross sectional isometric view of an electron beam device according to prior art,

#FIG. 2 is a schematic cross sectional perspective view of an electron exit window foil and a foil support plate, and

#With reference to FIG. 1 an electron beam device is shown. The electron beam device 100 comprises two parts; a tube body 102 housing and protecting an assembly 103 generating and shaping the electron beam, and a supportive flange 104 carrying components relating to the output of the electron beam, such as a window foil 106 and a foil support plate 108 preventing the window foil 106 from collapsing as vacuum is established inside the device 100. Further, during operation of the electron beam device the foil 106 is subject to excessive heat. Thereby, the foil support plate 108 also serves the important purpose of conducting heat generated in the foil 106 during use away from the foil 106 of the device. By keeping the foil temperature moderate a sufficiently long lifetime of the foil 106 may be obtained.

#With reference to FIG. 2, an electron exit window is shown comprising the foil 106 and the foil support 108. The support 108 is arranged inside the electron beam device such that vacuum is maintained on the inside of the exit window. This is indicated by P1 and P2 in FIG. 2, where P1 denotes atmospheric pressure outside the exit window and P2 represents vacuum on the inside.

#During manufacturing, the foil support plate 108, being of copper, is preferably attached to the flange 104 forming a part of the tube body 102. The flange 104 is generally made of stainless steel. The window foil 106 is then bonded onto a separate frame thus forming a foil-frame sub assembly. The foil 106 is subsequently coated, in order to improve its properties regarding for instance heat transfer. The foil-frame subassembly is subsequently attached to the tube body 102 to form a sealed housing.