Gas capture element

Abstract

A gas capture element for capturing gas within a non-evaporable getter pump, said gas capture element comprising a surface structure comprising a plurality of structure elements formed from NEG material as pillars or microvilli gener- ated by additive manufacturing.

Description

[0001]GAS CAPTURE ELEMENT The present invention relates to a gas capture element for capturing gas within a non-evaporable getter (NEG) pump. Further the present invention relates to a method of manufacturing a gas capture element, and to an NEG pump. NEG pumps are commonly used as ultra-high vacuum (UHV) pumps in which layers of sintered disks of NEG material are heated and activated inside the device. NEG coated hardware is also used in some UHV applications both to reduce the effect of surface outgassing in pipework but also to act as an addi- tional pumping mechanism. It is known that the pumping speed of a NEG pump is directly proportional to its active surface area. Most current sintered disks have deliberately high po- rosity to achieve this. However, hardware such as pipes or other vacuum components are coated with an NEG material usually by sputtering which provides a smooth and compact surface. Thus, the active surface of the NEG coated hardware is determined by the surface area of the component itself which tends to have insufficient pump activity. It is an object of the present invention to provide a gas capture element with enhanced pump activity. The problem is solved by a gas capture element according to claim 1 and a method according to claim 11. A gas capture element according to the present invention for capturing gas with- ing a non-evaporable getter pump comprises a surface structure. The surface structure comprises a plurality of structure elements of NEG material generated by additive manufacturing. Additive manufacturing is a well-known technique to manufacture small but precise structures even from metals by adding material in a determined way at predefined positions to create those structure elements. Additive manufacturing has developed in the past and thus also very small struc- tures down to a microscale are feasible with this technique. Also, different kinds of metals can be used for additive manufacturing that can provide a pumping effect as NEG material when activated. Thus, additive manufacturing provides a versatile and reliable technique to create the surface structure of the gas cap- ture element. Hence though the use of additive manufacturing structure ele- ments are added to the surface, thereby increasing the active surface which leads to an improved pump performance, i.e., pumping speed, of the gas cap- ture element. The structure elements are built as pillars or microvilli. By these structures the surface can be increased. In particular, pillars or microvilli are suitable in order to increase the surface-to-area ratio of the gas capture element. This ratio de- termines the active surface of the gas capture element over a specific area. In the prior art the surface-to-area ratio is equal to 1 when sputtering is used to coat hardware. When is above 1, it is indicating that the active surface is in- creased for the same area. Alternatively, the increase of the active surface by the present invention can be also quantified by a surface-to-volume ratio, wherein the surface is the active surface providing a pumping effect and the volume is the volume of the getter material. Increasing the surface-to-volume ratio results in an increased active surface for a constant amount of getter ma- terial. Thus, both the surface-to-area ratio and the surface-to-volume ratio can be used to determine the increased active surface provided by the present in- vention. Preferably, the surface-to-area ratio is larger than 10 and preferably larger than 100 and most preferably larger than 1000. Thus, by the present invention suf- ficient increase of pumping speed by the increased surface of the NEG material is achieved. Preferably, the structure elements have a ratio of height to width above 10, preferably above 20. Thus, by narrow and tall structure elements sufficient sur- face increase of the NEG material is achieved. Preferably, the structure elements have a height of between 5μm and 1000μm, preferably between 50μm and 500μm. Thus, depending on the abilities of the additive manufacturing technique sufficient high structure elements can be pro- vided on the surface structure of the gas capture element in order to increase the active surface of the gas capture element. Preferably, the structure elements have a width of between 1μm and 100μm, preferably between 10μm and 100μm. Thus, the structure elements can be made sufficiently small in order to be placed close together such that a large number of structure elements can be placed within an area to increase the active surface of the gas capture element. Preferably, the distance between two adjacent structure elements is smaller than 50μm, preferably smaller than 20μm and most preferably smaller than 10μm. Thus, adjacent structure elements can be placed in close proximity to each other. Thereby the number of structure elements per area can be in- creased, increasing the active surface of the gas capture element. Preferably, the periodicity of the structure elements, denoting a distance from a center point of one structure element to the center point of neighboring struc- ture element, is smaller than 100μm, preferably smaller than 50μm and most preferably smaller than 20μm. Thus, by a small periodicity of the structure ele- ments, a high density of structure elements within an area can be achieved, increasing the active surface of the gas capture element. Preferably, the surface structure is regularly patterned. Since additive manufac- turing provides a choice about where to place the structure elements, a regularly patterned surface structure can be achieved. Preferably, the surface structure has a structure element density of more than 10 / cm², more preferably more than 100 / cm² and most preferably more than 1000 / cm². Thus, a sufficient large number of structure elements can be placed within one area in order to increase the active surface of the gas capture ele- ment. Preferably, the structure elements are substantially identical or different. As used herein, “substantial” means identical within the accuracy of the additive manufacturing process. Preferably, the structure elements are made from an NEG material such as Zir- conium (Zr), Vanadium (Va), Titanium (Ti), Tantalum (Ta), Hafnium (Hf), Iron (Fe), Aluminum (Al) or an alloy of one or more of these elements. In another aspect of the present invention a method of manufacturing a gas capture element for capturing gas within a non-evaporable getter pump is pro- vided comprising the step of depositing an NEG material by additive manufac- turing on to a surface to create a surface structure. Preferably, the method is built along the features of the gas capture element described before. In a further aspect, the present invention provides an NEG pump comprising a gas capture element as aforementioned or manufactured as aforementioned. Features described above in relation to one aspect of the invention are equally applicable to each of the other aspects of the invention. In the following the present invention is described in more detail with reference to the accompanying figures. The figures show: Figure 1 a schematic representation of a gas capture element in a sec- tional view and Figure 2 a schematic representation of the gas capture element of figure 1 in a top view. A gas capture element 10 comprises a surface 14. The surface 14 may be the surface of a vacuum hardware such as a pipe or other type of vacuum compo- nent. On to surface 14 the structure elements 12 are generated by additive manufacturing. The structure elements 12 are built from any NEG material such as Zr, Ti, Ta or an alloy of one or more of these elements. The structure elements are built as pillars or microvilli. The structure elements 12 may have different shapes. In addition the present invention is also not lim- ited to the specific number of structure elements shown in the figures and usu- ally the gas capture element 10 of the present invention comprises a large num- ber of structure elements generated onto the surface 14 by additive manufac- turing. Further, in the example of the figures all structure elements are indicated to be similar or even identical. However, the present invention is not limited to this configuration and different structure elements may have different shapes or dimensions all employed in one gas capture element. Further, in the example of the figures it is show that the structure elements are regularly patterned over the surface area of the hardware. This is in particular feasible due to using ad- ditive manufacturing as a technique for creating the structure elements and differs to random processes such as sputtering, growths or any other conven- tional deposition method. The structure elements 12 may have a height H, a width W, a distance between adjacent structure elements D and a periodicity of Δ. The height H of the struc- ture elements may be between 5μm and 1000μm, preferably between 50μm and 500μm. The width W of the structure elements 12 may be between 1μm and 100μm, preferably between 10μm and 100μm. The distance D between two adjacent structure elements 12 may be smaller than 50μm, more preferably smaller than 20μm and most preferably smaller than 10μm. The periodicity Δ may be smaller than 100μm, preferably smaller than 50μm and most preferably smaller than 20μm. In particular the ratio H / W of height H to width W of the structure elements is preferably above 10 and more preferably above 20. Thus, by the configuration of the structure elements and their dimensions, a high den- sity of structure elements can be achieved. In particular the structure element density may be more than 10 / cm2, preferably more than 100 / cm2and more preferably more than 1000 / cm². Thus, a high number of structure elements 12 can be placed within an area in order to increase a surface-to-area ratio. The surface-to-area ratio determines the active surface provided by the structure elements divided by the area of the surface 14 in which the structure elements 12 are arranged. Preferably, the surface-to-area ratio is larger than 10, prefer- ably larger than 100 and more preferably larger than 1000. Thus, a substantial increase of the active surface can be achieved by using ad- ditive manufacturing technique when creating structure elements to increase the active NEG coated surface. Thereby pump performance and in particular pumping speed of the NEG material can be increased. Reference list: Gas capture element 10 Structure element 12 Surface 14

Claims

CLAIMS 1. A gas capture element for capturing gas within a non-evaporable getter pump, said gas capture element comprising a surface structure compris- ing a plurality of structure elements in the form of pillars or microvilli of NEG material generated by additive manufacturing.

2. The gas capture element according to claim 1, wherein a surface-to-area ratio of the gas capture element is larger than 10, preferably larger than 100 and more preferably larger than 1000.

3. The gas capture element according to any of claims 1 to 2, wherein the structure elements have a ratio of height to width above 10, preferably above 20.

4. The gas capture element according to any of claims 1 to 3, wherein the structure elements have a height of between 5μm and 1000μm, prefera- bly between 50μm and 500μm.

5. The gas capture element according to any of claims 1 to 4, wherein the structure elements have a width of between 1μm and 100μm, preferably between 10μm and 100μm.

6. The gas capture element according to any of claims 1 to 5, wherein the distance between two adjacent structure elements is smaller than 50μm, preferably smaller than 20μm and most preferably smaller than 10μm.

7. The gas capture element according to any of claims 1 to 6, wherein the surface structure is regularly patterned.

8. The gas capture element according to any of claims 1 to 7, wherein the surface structure has a structure element density of more than 10 / cm², preferably more than 100 / cm² and most preferably more than 1000 / cm².

9. The gas capture element according to any of claims 1 to 8, wherein the structure elements are substantially identical. 10.The gas capture element according to any of claims 1 to 9, wherein the structure elements are made from Zr, Ti, Ta, Hf, Fe, Va, Al or an alloy of one or more of these elements. 11.Method of manufacturing a gas capture element for capturing gas within a non-evaporable getter pump, comprising depositing by additive manu- facturing an NEG material on to a surface to create a surface structure of pillars or microvilli. 12.Method according to claim 11, wherein the surface structure is built ac- cording to the gas capture element of any of claims 1 to 10. 13.NEG pump comprising at least one gas capture element according to any of claims 1 to 10 or manufactured according to claim 11 or claim 12.

Images