VACUUM CHAMBER SEAL

Abstract

A seal for a vacuum chamber is formed from two outer insulation blocks, an intermediate insulation block, some interior insulation sheets and some exterior insulation sheets. A first outer insulation block seals between a first wall of the vacuum chamber and a first power transmission plate. A second outer insulation block seals between a second wall of the vacuum chamber and a second power transmission plate. The intermediate insulation block seals between the first and second power transmission plates. The interior insulation sheets are arranged in slots in a first side of the intermediate insulation block. The exterior insulation sheets are arranged in the slots in a second side of the intermediate insulation block.

Claims

1. A seal for a vacuum chamber, wherein the vacuum chamber comprises a first wall and a second wall, the seal comprising: a first outer insulation block for sealing between the first wall of the vacuum chamber and a first power transmission plate that extends from the interior of the vacuum chamber to the exterior of the vacuum chamber between the first and second walls of the vacuum chamber; a second outer insulation block for sealing between the second wall of the vacuum chamber and a second power transmission plate that extends from the interior of the vacuum chamber to the exterior of the vacuum chamber between the first and second walls of the vacuum chamber; an intermediate insulation block for sealing between the first and second power transmission plates, wherein the intermediate insulation block comprises one or more slots formed in a first side of the intermediate insulation block for facing the interior of the vacuum chamber and one or more slots formed in a second side of the intermediate insulation block for facing the exterior of the vacuum chamber; one or more interior insulation sheets for extending between the first and second power transmission plates on the interior of the vacuum chamber, wherein the one or more interior insulation sheets are arranged in the one or more slots in the first side of the intermediate insulation block; and one or more exterior insulation sheets for extending between the first and second power transmission plates on the exterior of the vacuum chamber, wherein the one or more exterior insulation sheets are arranged in the one or more slots in the second side of the intermediate insulation block.

2. The seal as claimed in claim 1, wherein the first and second power transmission plates are arranged to deliver a high voltage and/or a high current to a load in the vacuum chamber.

3. The seal as claimed in claim 1, wherein the first outer insulation block comprises mating surfaces for sealing against the first wall of the vacuum chamber and the first power transmission plate, wherein the second outer insulation block comprises mating surfaces for sealing against the second wall of the vacuum chamber and the second power transmission plate, and wherein the intermediate insulation block comprises mating surfaces for sealing against the first and second power transmission plates.

4. The seal as claimed in claim 3, wherein the mating surfaces of each of the insulation blocks comprises one or more grooves, wherein a compressible material is arranged in each of the grooves, wherein the grooves in the mating surfaces are offset from each other.

5. (canceled)

6. The seal as claimed in claim 3, wherein the mating surfaces of the intermediate insulation block have a dimension in a direction across the walls of the vacuum chamber that is substantially equal to the dimension in a direction across the walls of the vacuum chamber of the mating surface of the adjacent outer insulation block.

7. (canceled)

8. The seal as claimed in claim 1, wherein the dimension of the first and second outer insulation blocks, and the intermediate insulation block, in a direction across the walls of the vacuum chamber, is greater than or equal to the dimension of the first and second walls of the vacuum chamber in a direction across the walls of the vacuum chamber.

9. The seal as claimed in claim 1, wherein the dimension of the intermediate insulation block in a direction between the first and second walls of the vacuum chamber is greater than the ratio of the voltage across the power transmission plates to the dielectric strength of the intermediate insulation block.

10. The seal as claimed in claim 1, wherein the first and second outer insulation blocks are shaped to extend up the sides of the first and second walls of the vacuum chamber respectively.

11. The seal as claimed in claim 1, wherein the intermediate insulation block comprises at least two slots formed in the first side of the intermediate insulation block, and wherein the intermediate insulation block comprises at least two slots formed in the second side of the intermediate insulation block.

12. The seal as claimed in claim 1, wherein the intermediate insulation block comprises one or more slots formed in one or more edges of the first side adjacent to the first power transmission plate and/or one or more slots formed in one or more edges of the second side adjacent to the second power transmission plate.

13. The seal as claimed in claim 12, wherein the one or more edge slots are formed as a step or taper in the intermediate insulation block.

14. The seal as claimed in claim 1, wherein the intermediate insulation block comprises one or more slots formed away from the edges of the first side and/or the second side of the intermediate insulation block.

15. The seal as claimed in claim 1, wherein the intermediate insulation block comprises a plurality of sub-blocks, wherein at least one of the one or more slots are formed between the plurality of sub-blocks.

16. The seal as claimed in claim 15, wherein one or more of the sub-blocks comprise one or more slots formed in one or more edges of the first side of the sub-blocks and/or one or more slots formed in one or more edges of the second side of the sub-blocks.

17. The seal as claimed in claim 15, wherein the sub-blocks comprise mating surfaces for sealing against another of the sub-blocks, wherein one or more of the mating surfaces of the sub-blocks comprise one or more grooves, wherein a compressible material is arranged in the grooves.

18. The seal as claimed in claim 1, wherein the seal comprises a plurality of insulation sheets in each of the one or more slots of the intermediate insulation block.

19. The seal as claimed in claim 1, wherein the seal comprises a plurality of overlapping insulation sheets arranged in the one or more slots, wherein each of the insulation sheets of the plurality of overlapping insulation sheets extends around less than the perimeter of the vacuum chamber and at least one of the plurality of overlapping insulation sheets extends around a portion of the perimeter that is common with at least another of the plurality of overlapping insulation sheets.

20. (canceled)

21. (canceled)

22. A vacuum chamber comprising: a first wall and a second wall defining the outer surface of the vacuum chamber; a load within the vacuum chamber; a first power transmission plate that extends from the interior of the vacuum chamber to the exterior of the vacuum chamber between the first and second walls of the vacuum chamber; a second power transmission plate that extends from the interior of the vacuum chamber to the exterior of the vacuum chamber between the first and second walls of the vacuum chamber, wherein the first and second power transmission plates are arranged to deliver a voltage to the load; and a seal for sealing between the first and second walls, and between the first and second power transmission plates; wherein the seal comprises: a first outer insulation block sealing between the first wall of the vacuum chamber and the first power transmission plate; a second outer insulation block sealing between the second wall of the vacuum chamber and the second power transmission plate; an intermediate insulation block sealing between the first and second power transmission plates, wherein the intermediate insulation block comprises one or more slots formed in a first side of the intermediate insulation block facing the interior of the vacuum chamber and one or more slots formed in a second side of the intermediate insulation block facing the exterior of the vacuum chamber; one or more interior insulation sheets extending between the first and second power transmission plates on the interior of the vacuum chamber, wherein the one or more interior insulation sheets are arranged in the one or more slots in the first side of the intermediate insulation block; and one or more exterior insulation sheets extending between the first and second power transmission plates on the exterior of the vacuum chamber, wherein the one or more exterior insulation sheets are arranged in the one or more slots in the second side of the intermediate insulation block.

23. An electric power feed apparatus for delivering a voltage to a load within a vacuum chamber, wherein the vacuum chamber comprises a first wall and a second wall, the electric power feed apparatus comprising: a first power transmission plate for extending from the interior of the vacuum chamber to the exterior of the vacuum chamber between the first and second walls of the vacuum chamber; a second power transmission plate for extending from the interior of the vacuum chamber to the exterior of the vacuum chamber between the first and second walls of the vacuum chamber, wherein the first and second power transmission plates are arranged to deliver a voltage to the load; and a seal for sealing between the first and second walls, and between the first and second power transmission plates, wherein the seal comprises: a first outer insulation block for sealing between the first wall of the vacuum chamber and the first power transmission plate; a second outer insulation block for sealing between the second wall of the vacuum chamber and the second power transmission plate; an intermediate insulation block sealing between the first and second power transmission plates, wherein the intermediate insulation block comprises one or more slots formed in a first side of the intermediate insulation block for facing the interior of the vacuum chamber and one or more slots formed in a second side of the intermediate insulation block for facing the exterior of the vacuum chamber; one or more interior insulation sheets extending between the first and second power transmission plates on the interior of the vacuum chamber, wherein the one or more interior insulation sheets are arranged in the one or more slots in the first side of the intermediate insulation block; and one or more exterior insulation sheets extending between the first and second power transmission plates on the exterior of the vacuum chamber, wherein the one or more exterior insulation sheets are arranged in the one or more slots in the second side of the intermediate insulation block.

24. A pulsed power apparatus comprising: a vacuum chamber, the vacuum chamber comprising: a first wall and a second wall defining the outer surface of the vacuum chamber; and a load within the vacuum chamber; the pulsed power apparatus further comprising: a first power transmission plate that extends from the interior of the vacuum chamber to the exterior of the vacuum chamber between the first and second walls of the vacuum chamber; a second power transmission plate that extends from the interior of the vacuum chamber to the exterior of the vacuum chamber between the first and second walls of the vacuum chamber, wherein the first and second power transmission plates are arranged to deliver a voltage to the load; a voltage generation system for applying a voltage between the first and second power transmission plates; and a seal for sealing between the first and second walls, and between the first and second power transmission plates; wherein the seal comprises: a first outer insulation block sealing between the first wall of the vacuum chamber and the first power transmission plate; a second outer insulation block sealing between the second wall of the vacuum chamber and the second power transmission plate; an intermediate insulation block sealing between the first and second power transmission plates, wherein the intermediate insulation block comprises one or more slots formed in a first side of the intermediate insulation block facing the interior of the vacuum chamber and one or more slots formed in a second side of the intermediate insulation block facing the exterior of the vacuum chamber; one or more interior insulation sheets extending between the first and second power transmission plates on the interior of the vacuum chamber, wherein the one or more interior insulation sheets are arranged in the one or more slots in the first side of the intermediate insulation block; and one or more exterior insulation sheets extending between the first and second power transmission plates on the exterior of the vacuum chamber, wherein the one or more exterior insulation sheets are arranged in the one or more slots in the second side of the intermediate insulation block.

Description

[0102] A preferred embodiment for the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0103] FIG. 1 shows schematically a pulsed power apparatus according to an embodiment of the present invention;

[0104] FIG. 2 shows a cross section of an electric power feed apparatus according to an embodiment of the present invention; and

[0105] FIG. 3 shows a set of insulation sheets, in accordance with an embodiment of the present invention, for use in the electric power feed apparatus shown in FIG. 2.

[0106] An embodiment of the invention, which provides a vacuum chamber for use in a pulsed power (e.g. high energy density physics) apparatus will now be described. Such a pulsed power apparatus requires a high voltage power supply to be fed into a vacuum chamber, for delivering a high voltage pulse to a load in the vacuum chamber. In order to maintain an effective vacuum in the vacuum chamber, a good seal around where the power supply enters the vacuum chamber needs to be provided. An effective vacuum helps to reduce the risk of electrical breakdown in the vacuum chamber. As will be described, the seal according to an embodiment of the present invention helps to minimise the inductance that results from the insulation of the seal between the power transmission plates of the power supply.

[0107] FIG. 1 shows a pulsed power apparatus 201 according to an embodiment of the present invention. The pulsed power apparatus 201 includes a voltage generation system 202 that is arranged to apply a voltage, V, between a pair of power transmission plates 203, 204. The power transmission plates 203, 204 are arranged to deliver the voltage to a load 205 in a vacuum chamber 206. The vacuum chamber 206 has a seal 207 where the power transmission plates 203, 204 pass through the walls of the vacuum chamber 206.

[0108] FIG. 2 shows an electric power feed apparatus 1 for a vacuum chamber according to an embodiment of the present invention, e.g. for use in the pulsed power apparatus 201 shown in FIG. 1. FIG. 2 shows a cross section through the walls 2, 4 of a vacuum chamber, which, with the electric power feed apparatus 1, extend around the perimeter of the vacuum chamber. The walls 2, 4 of the vacuum chamber thus define the boundary between the interior 6 and the exterior 8 of the vacuum chamber.

[0109] The electric power feed apparatus 1 includes a seal for sealing the gap between the walls 2, 4 of the vacuum chamber, through which a pair of electric power transmission plates 10, 12 passes. The power transmission plates 10, 12 are arranged to deliver a high voltage to a load inside the vacuum chamber.

[0110] The electric power feed apparatus 1 includes two U-shaped outer insulation blocks 14, 16 that fit around the edges of the walls 2, 4 of the vacuum chamber. The outer insulation blocks 14, 16 each have a planar mating surface 18, 20 that seals against the respective edge of the walls 2, 4 of the vacuum chamber. The outer insulation blocks 14, 16 also each have a planar mating surface 22, 24 that seals against the respective power transmission plates 10, 12. A groove 26, 28 is defined in each of the planar mating surfaces 22, 24 that face the power transmission plates 10, 12 and an O-ring 30, 32 is located in each groove 26, 28.

[0111] An intermediate insulation block, formed from two sub-blocks 34, 36, is sandwiched between the two power transmission plates 10, 12. Each sub-block 34, 36 has a planar mating surface 38, 40, 42, 44 on either side, the outer mating surfaces 38, 44 for sealing against the power transmission plates 10, 12, the inner mating surfaces 40, 42 for sealing against each other. A groove 46, 48, 50, 52 is defined in each mating surface 38, 40, 42, 44 and an O-ring 54, 56, 58, 60 is located in each groove 46, 48, 50, 52. As can be seen from FIG. 2, the grooves 26, 28, 46, 48, 50, 52 (and thus the O-rings 30, 32, 54, 56, 58, 60) are offset from each other in the mating surfaces 22, 24, 38, 40, 42, 44 that are adjacent to each other.

[0112] The sub-blocks 34, 36 of the intermediate insulation block extend further out than the outer insulation blocks 14, 16, with the edges of the sub-blocks 34, 36 being tapered. This tapering of the sub-blocks 34, 36 forms three slots 62, 64, 66, 68, 70, 72 on either side of the intermediate insulation block. A set of 20 Mylar® insulation sheets 74, 76, 78, 80, 82, 84 are located in each of the slots 62, 64, 66, 68, 70, 72, such that three sets of insulation sheets 74, 76, 78, extend into the interior 6 of the vacuum chamber and three sets of insulation sheets 80, 82, 84 extend to the exterior 8 of the vacuum chamber between the power transmission plates 10, 12.

[0113] In the interior 6 of the vacuum chamber, the power transmission plates 10, 12 are brought closer together than their spacing at the walls 2, 4 of the vacuum chamber and extend to a load (not shown) at the centre of the vacuum chamber. At the exterior 8 of the vacuum chamber, the power transmission plates 10, 12 are brought closer together than their spacing at the walls 2, 4 of the vacuum chamber and extend to a voltage generation system (e.g. as shown in FIG. 1) for charging the power transmission plates 10, 12 to a high voltage.

[0114] FIG. 3 shows a configuration of a set of insulation sheets, in accordance with an embodiment of the present invention, for use in the electric power feed apparatus 1 shown in FIG. 2. The insulation sheets 101, 102, 103 shown in FIG. 3 may form any one of the sets of insulation sheets 74, 76, 78, 80, 82, 84 in the electric power feed apparatus 1 shown in FIG. 2. Thus, each layer in the sets of insulation sheets 74, 76, 78, 80, 82, 84 (of which there may be twenty layers, for example) may be made up of three insulation sheets 101, 102, 103.

[0115] FIG. 3 shows that the insulation sheets 101, 102, 103 each extend around half of the perimeter of the vacuum chamber. The insulation sheets 101, 102, 103 in the set each overlap the adjacent insulation sheet by approximately 60 degrees.

[0116] In operation, the vacuum chamber and the electric power feed apparatus is assembled as shown in FIGS. 1 and 2. The power transmission plates 10, 12 are charged to a high voltage (e.g. ±100 kV) by a voltage generation system connected to the power transmission plates 10, 12. The seal between the power transmission plates 10, 12 and between the walls 2, 4 of the vacuum chamber act to insulate the power transmission plates 10, 12 from each other and from the walls 2, 4 of the vacuum chamber. This helps to allow the power transmission plates 10, 12 to be charged to the high voltage and to be kept at the high voltage without the risk of electrical breakdown. The high voltage is then discharged to the load in the vacuum chamber, e.g. as part of the pulsed power system shown in FIG. 1.

[0117] It will be seen from the above that, in at least preferred embodiments, the vacuum chamber seal of the present invention provides an effective seal between the walls of the vacuum and the pair of power transmission plates, owing to the solid insulation blocks. The insulation sheets of the seal help to allow the pair of power transmission plates to be brought closer together, thus helping to reduce the inductance between the pair of power transmission plates, while still providing sufficient insulation between them, e.g. to protect against electrical punch through, even when subject to a high electric field gradient. Thus the seal of the present invention exploits the beneficial properties of both the insulation blocks (i.e. a good seal) and the insulation plates (i.e. low inductance).

[0118] The transition between the insulation sheets and the insulation blocks, via the slots, helps to reduce the extent of the insulation blocks, which also helps to reduce the inductance between the pair of power transmission plates, while still allowing a good seal to be provided and insulating the power transmission plates from each other. This helps to allow the power transmission plates to deliver a high voltage and current into the load in the vacuum chamber at a high discharge rate. The slots in the intermediate insulation block also help to increase the path length between the power transmission plates. This helps to reduce the risk of electrical breakdown owing to surface tracking.