Method for assembling an electron exit window and an electron exit window assembly

Abstract

A method for assembling an electron exit window of an electron beam generating device comprises arranging a foil support plate on a housing of the electron beam generating device, bonding a window foil to a frame along at least one continuous bonding line, thus creating an exit window sub-assembly, and attaching the exit window sub-assembly onto the housing.

Claims

1. A method for assembling an electron exit window of an electron beam generating device, comprising: arranging a foil support plate on a housing of the electron beam generating device, the foil support plate comprising an indentation and the housing comprising an indentation; bonding a metal window foil to a frame along at least one continuous bonding line, thus creating an exit window sub-assembly; and attaching the exit window sub-assembly onto the housing by positioning the frame of the exit window sub-assembly in both the indentation of the foil support plate and the indentation of the housing.

2. The method according to claim 1, comprising attaching said exit window sub-assembly to the housing in such a way that it forms a protection for the foil support plate ensuring that the foil support plate is not exposed to an environment outside of the electron beam generating device.

3. The method according to claim 1, comprising diffusion bonding said window foil to the frame.

4. The method according to claim 1, comprising providing the window foil with a coating before attaching the exit window sub-assembly onto the housing.

5. The method according to claim 4, comprising providing said coating on a side of the window foil which will face an inside of the electron beam generating device once assembled.

6. The method according to claim 1, wherein attaching of the exit window sub-assembly comprises welding of the frame onto the housing.

7. A method for assembling an electron exit window of an electron beam generating device, comprising: bonding a window foil made of metal to a frame along at least one endless bonding line to create an exit window sub-assembly in which the window foil is bonded to the frame, the frame surrounding an open region and the window foil extending across the entire open region; securing a foil support plate to an edge of an opening in a flange of a housing of the electron beam generating device so that the foil plate spans the entire opening, the foil support plate comprising an indentation and the flange of the housing comprising an indentation that directly communicates with the indentation of the foil support plate so that the indentation of the foil support plate and the indentation of the flange form a continuous indentation; and attaching the exit window sub-assembly onto the housing in covering relation to the foil support plate so that no part of the foil support plate is exposed to outside atmosphere by arranging the frame of the exit window sub-assembly in the continuous indentation collectively formed by the foil support plate and the flange of the housing.

8. The method according to claim 7, wherein the window foil is bonded to the frame either before or after the securing of the foil support plate to the edge of the opening in the flange.

9. The method according to claim 7, wherein the bonding of the window foil to the frame comprises diffusion bonding the window foil to the frame.

10. The method according to claim 7, wherein the window foil comprises a coating thus being a coated window foil, the bonding of the window foil to the frame comprising bonding the coated window foil to the frame.

11. A method for assembling an electron exit window of an electron beam generating device, comprising: arranging a foil support plate on a housing of the electron beam generating device, the foil support plate and the housing each comprising an indentation, bonding a window foil made of metal to a frame along at least one continuous bonding line to create an exit window sub-assembly, and attaching the exit window sub-assembly onto the housing, the attaching of the exit window sub-assembly comprising positioning the frame of the exit window sub-assembly in the indentation of the foil support plate and in the indentation of the housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, an exemplary embodiment of the invention will be described in greater detail, with reference to the enclosed drawings, in which:

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

(3) FIG. 2 is a schematic partial cross section of the device of FIG. 1, shown as an exploded view,

(4) FIG. 3 is a schematic partial cross section of a device according to a first embodiment of the invention, for comparison with the cross section of FIG. 2, as shown as an exploded view,

(5) FIG. 4 is a schematic partial cross section similar to FIG. 3, but shown in an assembled state, and

(6) FIG. 5 is a partial cross section of a foil provided with a coating according to an embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

(7) FIGS. 1 and 2, comprising a prior art solution, have already been described. In an exemplary embodiment of the present invention, as shown in FIGS. 3 and 4, a foil support plate 208 is arranged on the housing of an electron beam generating device. The foil support plate 208 is preferably made of copper and is bonded to a flange 204 of the housing. One possible bonding technique is brazing. The foil support plate 208 is bonded to an edge 210 of an opening 212 in the flange 204.

(8) In a separate step, or in the same manufacturing step, said flange 204 is plasma welded to the tube body 202 forming said housing of the electron beam generating device. In another embodiment, not shown, the tube body 202 and the flange 204 is made in one piece.

(9) In a separate step the window foil 206 is bonded onto a frame 214 to form an exit window sub-assembly 216. The word frame should here be interpreted as an element having a central hole configuration. The foil 206 is preferably made of titanium and said frame 214 is preferably made of stainless steel. Possible bonding techniques may be for example laser welding, electron beam welding, brazing, ultrasonic welding, diffusion bonding and gluing. In the exemplary embodiment the foil 206 is diffusion bonded onto the frame 214 along a continuous bonding line 218 partly shown in FIG. 4. The bonding line 218 is continuous to be able to maintain vacuum inside the electron beam device. The word continuous is used to define that the line is endless or closed. Further, it should be defined that the bonding line 218 extends along the hole configuration of the frame 214 but within the perimeter of the frame 214. Preferably, the bonding line 218 extends at a distance from the perimeter of the frame 214. Furthermore, at least one bonding line 218 is made. Thus, two or more bonding lines may be made. For example, an inner and an outer bonding line may be made on the frame 214, and the two lines may, for instance, be concentric with each other.

(10) At this stage the foil 206 may optionally be coated and in the coating process only the exit window assembly 216 needs to be processed. According to this embodiment the foil 206 may be coated on both sides, but preferably on the inside, i.e. the side of the foil 206 which will face the inside of the electron beam generating device once assembled.

(11) In FIG. 5 the foil 206 is shown with a coating denoted 206C.

(12) The coating 206C serves the purpose of increasing thermal conductivity in order to increase the lifetime of the foil 206.

(13) As mentioned an advantage with the present invention is the possibility of being able to provide the coating 206C to the inside of the foil 206. Plasma, which is being built up outside of the electron exit window during operation of the electron beam device, can wear down the coating of an electron exit window. However, on the inside of the foil 206 the coating 206C will be protected from the effects of plasma. Hence, there is an opportunity, with the present invention, to choose among several heat conductive coating materials, for example DLC (Diamond-like-carbon), copper, aluminium, graphite, silver and gold.

(14) Subsequently, the frame 214, and thereby the exit window sub-assembly 216 may be attached to the flange 204 portion of the housing.

(15) The step of attaching the exit window sub-assembly 216 to the housing is made in such a way that it forms a protection for the foil support plate 208 ensuring that the foil support plate 208 is not exposed to the environment outside of the electron beam generating device. As may be seen from FIG. 3 and FIG. 4 the frame 214 is arranged in an indentation 220 partly formed by the flange 204 of the housing and partly formed by the foil support plate 208. In an alternative embodiment, not shown, the indentation for receiving the frame may be formed in the housing only.

(16) The frame 214 of the exit window sub-assembly 216 is preferably welded onto the housing.

(17) It can be seen from FIG. 4 that after attachment of the exit window sub-assembly 216 onto the housing no portion of the foil support plate 208 is exposed to the outside atmosphere, and thereby corrosion of the copper foil support plate 208 is prevented.

(18) Further to the advantages, the exit window sub-assembly 216 may be tested separately, such that the hermetic sealing in the bond, along bonding line 218, between the foil 206 and the frame 214 is confirmed before the exit window sub-assembly 216 is welded to the flange 204. Should the seal be defective the exit window sub-assembly 216 may simply be discarded without affecting the cost or production time to any great extent. The frame 214 has in this exemplary embodiment a thickness of 3 mm, and is made of stainless steel.

(19) With the inventive solution there is an additional advantage in that the window foil 206 will be exposed to few processing steps. It should be understood that, with regard to the thinness of the foil 206, any processing work on or near the foil 206 may jeopardize the integrity of the foil 206.