Cryopump
The use of NEG elements in cryopumps addresses the contamination and replacement issues of activated carbon, enhancing pumping performance and reliability by up to 100 times at low temperatures, ensuring efficient and reliable operation.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- EDWARDS LTD
- Filing Date
- 2024-03-27
- Publication Date
- 2026-04-23
AI Technical Summary
Conventional cryopumps face issues with activated carbon contamination by hydrocarbons, leading to costly and complicated replacements, and potential contamination from epoxy resins, resulting in unreliable operation and reduced pumping performance.
The cryopump employs non-evaporative getter (NEG) elements instead of activated carbon, which are reactivatable and operate at low temperatures to enhance pumping performance, and are directly coated or mechanically coupled to cold panels without adhesives, ensuring reliable operation and improved performance.
NEG elements provide high pumping performance, are resistant to hydrocarbon contamination, and can be reactivated, offering improved reliability and extended operation without the need for replacement, with performance enhancement by up to 100 times at low temperatures compared to room temperature operation.
Smart Images
Figure 2026513363000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a cryopump, i.e., a cryogenic pump, which captures gases and vapors by condensation on a cold surface and generates a vacuum.
Background Art
[0002] Conventional cryopumps include a cold head that extends within the housing of the cryopump. The housing has an inlet, and the inlet of the cryopump is connected to a vacuum chamber or a vacuum device. Usually, the cold head is cooled by liquid helium or liquid nitrogen. To increase the surface area of the cold head with respect to the cryocondensation pumping process, a cold panel is coupled to the cold head. The cold head cools the cold panel typically to a temperature of 20 K or less to pump N2, Ar, O2 (other gases such as Xe, Kr, CO are pumped at a temperature of 55 K or less on the cold panel, and H2O vapor, CO2 are usually pumped at around 65 K).
[0003] Conventional cryopumps are usually combined with adsorption pumps. Generally, activated carbon (AC) is used as the adsorbent and is coated on the cold panel located inside the pump, which is cooled by the cold head. Gases such as H2, He, Ne are cryo-adsorbed on the cooled AC.
[0004] AC (activated carbon) can be easily and irreversibly contaminated by hydrocarbons including methane. Contaminated AC cannot be cleaned or reactivated and needs to be replaced. The replacement of AC is very complicated and expensive, and since the pump needs to be returned to the manufacturer, it results in a long-term operation stop. In addition, usually, activated carbon is adhered to the cold panel with an epoxy resin. However, the epoxy resin can be deteriorated by radioactive substances such as tritium. Furthermore, common epoxy resins may contaminate the pump environment. Replacing the epoxy resin commonly used to fix AC can be costly. [Overview of the project] [Problems that the invention aims to solve]
[0005] The objective of the present invention is to provide a cryopump with high pumping performance and reliable operation. [Means for solving the problem]
[0006] This problem is solved by the cryopump described in claim 1.
[0007] The cryopump according to the present invention comprises a housing having an inlet connectable to a vacuum chamber. A cold head is located inside the housing. Preferably, the cold head is positioned to generate a temperature low enough for gas or vapor to condense on it. At least one cold panel is coupled to the cold head. Non-evaporative getter elements (NEG elements) are coupled to the above or to each cold panel.
[0008] Accordingly, according to the present invention, activated carbon (AC) used in the prior art is replaced with an NEG element. The NEG element has the advantage of not being irreversibly contaminated with hydrocarbons. The NEG element can be reactivated by heating. Therefore, more reliable and stable operation of the cryopump is possible. At the same time, it has been shown that NEG elements operating at low temperatures can have high pumping performance. Therefore, the low temperature generated by the cold head can improve the pumping performance of the above or each NEG element, and as a result, the performance of the cryopump can be improved. In particular, compared to when the NEG element is operated at room temperature, the pumping capacity can be improved by 10 times or more, preferably 100 times or more, depending on the operating temperature.
[0009] Preferably, the cryopump comprises multiple cold panels, with two or more NEG elements coupled to two or more cold panels, preferably each cold panel. Thus, providing multiple NEG elements provides a sufficient surface area of NEG material for efficient gas pumping.
[0010] Preferably, the cold panel is formed as a baffle or plate. Preferably, the NEG element is coupled to the surface of the baffle facing outward from the inlet. Thus, the NEG element is protected by the shape of the baffle and is prevented from being obstructed by condensed gas on the opposite surface of the baffle facing the inlet.
[0011] Preferably, the NEG element is cooled to a temperature below 20K, and more preferably below 10K. At these temperatures, cryo-condensation is possible within the cryopump. At the same time, the pumping performance of the NEG element is improved by more than 100 times compared to operation at room temperature.
[0012] Preferably, the above or each NEG element includes one of Zr, V, Ti, Fe, Al, and Ta, or a combination thereof.
[0013] Preferably, the cryopump includes activated carbon bonded to one of the cold panels. Therefore, the cryopump may include a combination of AC and NEG elements to combine their advantages. Alternatively, the cryopump may not include activated carbon.
[0014] Preferably, the above or each cold panel includes a coating of NEG material. Therefore, since the NEG element is directly coated onto the cold panel, no additional adhesive or bonding element is required. Contamination of the NEG material by adhesive or degradation of the adhesive is prevented. Since the NEG element can be reactivated, replacement is unnecessary, and permanent coating of the NEG element on the cold panel is achievable.
[0015] Alternatively, at least one NEG element, more preferably two or more NEG elements, most preferably all NEG elements, are bonded to their respective corresponding cold panels, preferably with a radiation-resistant epoxy resin.
[0016] Alternatively, at least one NEG element, more preferably two or more NEG elements, and most preferably all NEG elements, are mechanically coupled to their respective cold panels. This allows each NEG element to be manufactured as an independent component and mechanically coupled to the cold panel by clamping or other means. Thus, the NEG elements can be replaced as needed.
[0017] Preferably, the NEG element is 300 cm² in length, depending on the size of the cryopump in which the NEG element is installed. 2 More preferably 500cm 2 The most preferred value is 600 cm. 2 The total surface area is as described above. Therefore, the total surface area of all NEG elements is large enough to provide sufficient pumping speed and capacity.
[0018] Preferably, for a cryopump with a nominal N2 pumping speed of 1500 l / s, the pumping capacity of the NEG element for H2 is greater than 1000 l / sec at room temperature. The H2 pumping speed of NEG materials below 20K is improved by at least 10 times. The combined effect of a large surface area and low temperature improves the pumping performance of the NEG element, enabling the achievement of high pumping speeds.
[0019] Preferably, a common heating element is provided within the cryopump to reactivate the cold panel and the NEG element. The heating element can be coupled to the cold head. The heating element can raise the temperature of the cold panel and the NEG element. This allows for the evaporation and removal of condensed gas on the cold panel and simultaneously reactivates the NEG element. Preferably, the heating element is configured to heat the NEG element to a temperature above 100°C, preferably above 150°C, and most preferably above 250°C, at a pressure of preferably less than 1E-5mbar, in order to reactivate the NEG element. Therefore, the use of an auxiliary, preferably removable, pump such as a turbomolecular pump may be required for NEG regeneration / reactivation.
[0020] The present invention will be described in detail below with reference to the attached drawings. [Brief explanation of the drawing]
[0021] [Figure 1] A schematic cryopump according to the present invention is shown. [Modes for carrying out the invention]
[0022] The cryopump 10 comprises a housing 12 defining a pump chamber 14 and an inlet 16. The inlet 16 is connected to the vacuum chamber 18 for removing gas from the vacuum chamber 18 using the cryopump 10. The cryopump 10 comprises a cold head 20, which can be, for example, a two-stage Gifford-McMahon refrigerator. In this respect, the cold head 20 comprises a first stage 22 and a second stage 24. The cold head 20 can be cooled by liquid helium. In this respect, during use, the temperature of the first stage 22 can be about 80 Kelvin (K), and the temperature of the second stage 24 can be less than 20 Kelvin, preferably less than 10 Kelvin. In detail, during operation, the temperature of the second stage can be between 7K and 9K.
[0023] The cold head 20 is surrounded by a radiation shield 26 to reduce heat transfer by radiation to the cold head 20. The radiation shield 26 is complemented by an inlet baffle 28. In use, the temperature of the baffle 28 and the radiation shield 26 can be about 100 Kelvin. The gaseous compounds with high condensation temperature received from the vacuum chamber 18 will condense on the baffle. Similarly, those compounds will also condense on the inner surface of the radiation shield 26.
[0024] A plurality of cold panels 30 are coupled to the second stage 24 of the cold head 20. Each of the cold panels 30 has a first surface 32 facing the inlet 16 and a second surface 34 facing outward from the inlet 16. Specifically, the cold panel 30 can be in a baffle shape. In use, gas molecules can condense on the first surface 32. Thereby, the first surface 32 will be covered with frozen gas during use. The NEG element 36 is attached to the second surface 34 of the cold panel 30. The attachment of the NEG element 36 to the cold panel 30 can be achieved by coating the second surface 34 with a NEG material. This is possible because replacement of the NEG element 36 is not required. Alternatively, the NEG element 36 can be adhered to or mechanically coupled to the cold panel 30 in another way. Due to the shape of the cold panel 30, the coating of the NEG element 36 by frozen or condensed gaseous compounds is minimized, and the pumping action of the NEG element 36 is maintained over a longer operating period.
[0025] Since the NEG element 36 is coupled to the cold head 20, the NEG element 36 is maintained at the same low temperature as the cold panel 30. Due to this low temperature, surprisingly, it has been shown that the pumping performance of the NEG element 36 is improved by more than 10 times, especially more than 100 times, compared to operation at room temperature. At the same time, there is no contamination of the NEG element by hydrocarbons such as methane compared to the use of conventional activated carbon (AC). Deterioration of any adhesive used in the prior art to attach AC to the cold panel can be avoided by directly coating the NEG element on the second surface 34 of the cold panel 30.
[0026] Since it is known that the pumping performance of the NEG material is improved at low temperatures, the present invention provides a beneficial combination of a cryopump and at least one NEG element, thereby avoiding the disadvantages of using activated carbon in the prior art. Therefore, the cryopump can operate for a longer period with improved pumping performance. Thereafter, reactivation is possible without the need to replace the NEG element 36.
Description of the reference numerals
[0027] 10 Cryopump 12 Housing 14 Pump chamber 16 Inlet 18 Vacuum chamber 20 Cold head 22 First stage 24 Second stage 26 Radiation shield 28 Baffle 30 Cold panel 32 First surface 34 Second surface 36 NEG element
Claims
1. A housing having an inlet that can be connected to a vacuum chamber, A cold head is disposed within the housing, At least one cold panel coupled to the cold head, One or more non-evaporative getter (NEG) elements coupled to at least one cold panel, A cryopump equipped with [a specific feature].
2. The cryopump according to claim 1, comprising a plurality of cold panels, wherein each NEG element is coupled to each of the cold panels.
3. The cryopump according to claim 1 or 2, comprising a common heating element for reactivating the cold panel and the corresponding NEG elements.
4. The cryopump according to any one of claims 1 to 3, wherein the cold panel or each cold panel is in the form of a baffle and has an NEG element coupled to a surface facing outward from the inlet.
5. The cold panel is arranged to cool the NEG elements to a temperature of less than 20K, preferably less than 10K. A cryopump according to any one of claims 1 to 4.
6. The cryopump according to any one of claims 1 to 5, wherein the above or each NEG element includes one of Zr, V, Ti, Fe, Al, Ta, or a combination thereof.
7. The cryopump according to any one of claims 1 to 6, wherein activated carbon is bonded to the above or each cold panel.
8. The cryopump according to any one of claims 1 to 7, wherein at least one of the cold panels is coated with NEG material.
9. The cryopump according to any one of claims 1 to 7, wherein each NEG element is bonded to or mechanically coupled to the respective cold panel.
10. The one or more NEG elements mentioned above have a range of at least 300 cm². 2 Preferably at least 500 cm 2 , more preferably at least 600 cm 2 A cryopump according to any one of claims 1 to 9, having the surface area of [specified area].