Vacuum module, vacuum device, and method for regenerating volume getter vacuum pump

Abstract

A method for regenerating a volume getter pump (NEG) in a vacuum system including an NEG and an ion getter pump, the method comprising the steps of: reducing the operating voltage of the ion getter pump; recording a current through the ion getter pump to determine a pressure within the vacuum system; and controlling a heating element of the NEG as a function of the current of the ion getter pump to heat NEG material.

Description

[Technical field]

[0001] The present invention relates to a vacuum module equipped with a volume getter vacuum pump and an ion getter pump, a vacuum device equipped with a volume getter vacuum pump and an ion getter pump, and a method for regenerating a volume getter vacuum pump. [Background technology]

[0002] Many industrial and scientific instruments and systems use -7 Ultra-high vacuums of less than 10 ... -1 from under mbar to 10 -3 It generates a rough vacuum with pressures of up to 10 mbar. The main vacuum pump has a -1 from under mbar to 10 -8 Combined with a high vacuum pump to generate pressures up to 10 mbar, in some cases -7 To generate pressures below mbar, they are combined with ultra-high vacuum pumps (UHV pumps). In such cases, the UHV pumps include adsorption pumps to achieve the pressures required for ultra-high vacuum. Of course, adsorption pumps include ion getter pumps and volume getter vacuum pumps, the latter also being called getter pumps or volume getter pumps.

[0003] Also, a large number of gases can be pumped by ion getter pumps. In general, ion getter pumps have two cathodes and one anode, between which a high voltage is applied. The high voltage accelerates electrons from the cathode to the anode, thereby ionizing the gas particles, which are then accelerated toward the cathode, where they are either adsorbed or otherwise reach the anode, where they are injected into the anode by their kinetic energy, without contributing to the gas pressure in either case. An external magnetic field applied by a permanent magnet increases the possibility of ionizing the gas particles by the accelerated electrons. In this case, the pumping capacity of the ion getter pump is limited by the size of the anode and cathode, and is therefore limited by the installation space available in the vacuum device.

[0004] Known volume getter pumps operate on the principle of chemical sorption, especially for reactive gaseous media such as oxygen, nitrogen and hydrogen, whereas for hydrogen physical sorption predominates. Known volume getter pumps also have "non-evaporable getter materials" (NEGs). These volume getter pumps are designated as NEGs based on their getter material. These pumps have high sorption rates and, as a result, high pumping speeds, which are usually higher than ion getter pumps of the same size. A further advantage of volume getter pumps is that hydrogen can be pumped more easily. However, the pumping efficiency of NEGs for hydrogen-carbon compounds is low, and in particular NEGs cannot pump noble gases.

[0005] During operation of the NEG, molecules and gas particles from the vacuum system are bound to its surface and do not contribute to the pressure in the vacuum system. As a result of this fouling, the active surface of the NEG material that contributes to the pumping power of the NEG is reduced. With the active surface of the NEG unavailable, the pumping power of the NEG drops to zero. The NEG therefore needs to be regenerated. This is usually done by heating the NEG material, called "bakeout". In this process, the molecules and gas particles bound to the surface of the NEG material are embedded in the NEG material by diffusion and the active surface of the NEG material becomes available again. Hydrogen does not bind to the surface, but to the solid by diffusion. During regeneration, it is released again and needs to be removed from the vacuum chamber by another vacuum pump. The regeneration process usually takes 10 -5 mbar or 10 -6 This must be done at a pressure below mbar, otherwise destruction of the NEG material may occur. Until now, ensuring this required pressure was the responsibility of the user of the vacuum device.

[0006] Compound pumps with a NEG pump and an ion getter pump are known, and typically during the NEG regeneration process the ion getter pump is switched off, i.e. the supply voltage to the ion getter pump is zero and the ion getter pump does not produce any pumping output. This prevents the ion getter pump from filling with gas particles coming out of the NEG during the bake-out / regeneration of the NEG material. Maintenance of the vacuum must be ensured by another pumping system, for example an external turbopump system.

[0007] Therefore, existing systems require additional vacuum monitoring during the NEG regeneration process, which requires additional technological steps such as pressure measurement in the vacuum device as well as permanent monitoring to prevent destruction of the NEG material. Summary of the Invention [Problem to be solved by the invention]

[0008] The technical problem of the present invention is to come up with a method that can reliably and reliably regenerate the NEG material of the NEG. [Means for solving the problem]

[0009] This problem is solved by a method according to claim 1 as well as a vacuum module according to claim 7 or a vacuum device according to claim 8.

[0010] The method according to the invention for the regeneration of a volume getter pump (non-evaporable getter pump - NEG) is applied to a vacuum module with a NEG and an ion getter pump or to a vacuum system with a NEG and an ion getter pump, in which case the NEG and the ion getter pump are always coupled to the vacuum system.

[0011] In the method according to the invention, the operating voltage of the ion getter pump is reduced. However, only the operating voltage of the ion getter pump is reduced. The operating voltage is not reduced to zero and the operating voltage of the ion getter pump is not switched off. Then, the current through the ion getter pump is recorded to determine the pressure in the vacuum device. Here, the current of the ion getter pump is proportional to the pressure in the vacuum device. Then, the heating element of the NEG is controlled as a function of the current of the ion getter pump for the bake-out and regeneration of the NEG material. In this way, since the ion getter pump is utilized to determine the pressure in the vacuum device, no additional technical means are required to determine the pressure in the vacuum device. Instead, the existing ion getter pump is used to determine the pressure in the vacuum device by measuring the current through the ion getter pump. In that case, the ion getter pump is used as a cold cathode gauge. Since the heating element of the NEG is controlled as a function of the current of the ion getter pump, the control of the heating element of the NEG is performed in direct dependence on the pressure of the vacuum device.

[0012] Preferably, the operating voltage of the ion getter pump is reduced to a level at least at which there is essentially no more pumping action. This prevents material leaving the NEG material during regeneration from depositing / adhering to the ion getter pump. For this purpose, the operating voltage of the ion getter pump is preferably reduced to less than 5 kV, in particular less than 3 kV, most preferably less than 1 kV. At such operating voltages, no significant pumping action of the ion getter pump remains. However, at the same time, the current through the ion getter pump remains proportional to the pressure in the vacuum device, so that the ion getter pump can be used to determine the pressure in the vacuum device.

[0013] If the current recorded by the ion getter pump corresponds to a pressure exceeding the first preset pressure, the heating element is preferably switched off. Thus, if the pressure in the vacuum device becomes higher than the first preset pressure, the heating element of the NEG is switched off in order to prevent the destruction of the NEG material. Thus, it is always ensured that the regeneration of the NEG material is only performed at pressures at which there is no risk of destruction of the NEG material.

[0014] Preferably, the heat output is increased when the current recorded by the ion getter pump corresponds to a pressure lower than the second preset pressure. In this way, when a greater vacuum exists in the vacuum system than is required for regeneration of the NEG, the regeneration temperature can be increased and the heat output of the heating element can be increased, thereby accelerating the regeneration, thereby shortening the regeneration time required to achieve full regeneration of the NEG material. Typically, the regeneration time is increased by 10 -6 At pressures of the order of mbar, regeneration of typical NEG materials occurs at 300 to 400 °C. If the pressure in the vacuum chamber is, for example, 10 -7 When the pressure is reduced to 1000 psi, the regeneration of the NEG material can take place at higher temperatures, for example up to 700° C., in which case the required regeneration time can be significantly reduced. As a result, rapid regeneration is possible, where the NEG heating element simply ensures that the necessary pressure is present and that a temperature is generated that can prevent damage or destruction of the NEG material.

[0015] Preferably, the first preset pressure and / or the second preset pressure is 10 -5 mbar, preferably 10 -6 In particular, the first preset pressure and the second preset pressure may be the same.

[0016] It is preferable to be able to continuously adjust the heat output of the NEG heating element relative to the pressure in the vacuum system. -5 At a first preset pressure of mbar the heating element of the NEG can be switched off. At pressures below a second preset pressure the heat output of the heating element is continuously increased depending on the vacuum in the vacuum device.

[0017] Furthermore, the invention relates to a vacuum module comprising a volume getter pump (NEG) and an ion getter pump, the NEG and the ion getter pump being directly coupled to each other, so that there is a combination of NEG and ion getter pump, in which case the NEG and the ion getter pump are connected to a control unit, the control unit being designed to execute the above mentioned method.

[0018] Furthermore, the present invention relates to a vacuum device comprising a volume getter pump (NEG) and an ion getter pump, the NEG and the ion getter pump being arranged separately from each other in the vacuum device, the NEG and the ion getter pump being further connected to a control unit, the control unit being designed to perform the above mentioned method.

[0019] Preferably, the control unit constitutes a common control unit for the NEG and the ion getter pump, thus ensuring a compact design. The invention will now be described in more detail based on preferred embodiments with reference to the accompanying drawings. [Brief description of the drawings]

[0020] [Figure 1]1 is a first embodiment of a pump module according to the present invention; [Diagram 2] 2 is a flow chart of a method according to the present invention; [Diagram 3] 1 illustrates a schematic diagram of the correlation between the current determined by an ion getter pump according to the present invention and the regeneration temperature of the NEG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] A pump module 10 according to the present invention comprises a flange 12 having a first side 14 and a second side 16 opposite the first side. When the flange 12 is coupled to a vacuum apparatus (not shown), the first side 14 faces the vacuum apparatus and is exposed to the vacuum created within the vacuum apparatus, among other things. The second side 16 is exposed to atmospheric pressure and is disposed outside the vacuum apparatus. The flange 12 can be coupled to the vacuum apparatus in a vacuum-tight manner using known means such as screws and seals.

[0022] An ion getter pump 18 is coupled to the first side 14 of the flange 12. A volume getter pump (NEG) 20 is disposed on the opposite side of the ion getter pump 18 from the flange 12. Thus, the flange 12 and the NEG 20 are disposed at opposite ends of the ion getter pump. That is, the NEG 20 is not directly coupled to the flange 12, but is indirectly coupled via the ion getter pump 18. Thus, in an installed state, the ion getter pump 18 and the NEG 20 are disposed to protrude into the vacuum system and pump gas therein.

[0023] The flange 12 further includes a common lead-through 22 through which the high voltage for operation of the ion getter pump 18 as well as the low voltage for the heating element for regeneration of the NEG are conducted, meaning that only one lead-through is required, reducing potential leak points in the ultra-high vacuum system.

[0024] Due to the stacked or serial structure of the NEG 20, the ion getter pump 18 and the flange 12, the diameter of the flange, i.e., the diameter of the flange surface 24 directly located in the vacuum, can be kept small, since it exactly matches or is slightly larger than the base area of ​​the ion getter pump 18 or the NEG 20. Thus, during installation, the NEG 20 and the ion getter pump 18 are introduced through the flange openings and are firmly attached to the vacuum system by the attachment of the flange 12 to the vacuum system.

[0025] In the method according to the invention as shown in FIG. 2, in a first step S01, the operating voltage of the ion getter pump is reduced. In this case, it is not reduced to zero, nor is the supply voltage to the ion getter pump switched off. Rather, the operating voltage of the ion getter pump is simply reduced, so that in practice the pumping action of the ion getter pump is no longer present. The operating voltage of the ion getter pump or the voltage between its cathode and anode may then reach, for example, 1 kV. At such an operating voltage, the current through the ion getter pump is proportional to the pressure inside the vacuum device to which the ion getter pump and the NEG are coupled. In a second step S02, the current through the ion getter pump is recorded and, due to the proportionality that exists, is used to determine the pressure in the vacuum device. In a third step S03 of the method according to the invention, the heating element of the NEG 20 is controlled based on the current of the ion getter pump, which corresponds to the pressure in the vacuum device, for the bake-out and regeneration of the NEG material.

[0026] FIG. 3 is a schematic representation showing the correlation between the current determined by the ion getter pump and corresponding to the pressure inside the vacuum device, and the bake-out temperature of the NEG material for regeneration of the NEG material.

[0027] In FIG. 3, the x-axis is the pressure or current of the ion getter pump and the y-axis is the temperature of the heating element. -5 mbar or 10 -6Up to a first pressure 40 in mbar, no heating of the NEG material is performed, since this could result in destruction of the NEG material. However, if a pressure lower than a threshold exists, a bakeout is performed, resulting in regeneration of the NEG material, in which case the lower pressure leads to a higher temperature of the heating elements of the NEG, which allows the NEG material to be regenerated faster. For example, if there is a first bakeout temperature 42 at the first pressure 40, then at a pressure lower than the first pressure there is a second bakeout temperature 44 that is higher than the first bakeout temperature 42 of the heating elements of the NEG 20. The correlation between pressure and bakeout temperature must then be non-linear, as shown diagrammatically in FIG. 3, but can follow any functional correlation and be adjusted for the application of interest. Thus, a method is proposed in which the regeneration of the NEG material in the NEG is reliably, robustly and efficiently brought about by the use of existing ion getter pumps. [Explanation of symbols]

[0028] S01: Reduce the operating voltage of the ion getter pump S02: Detect the current through the ion getter pump to determine the pressure in the vacuum system. S03: Control the heating element of the NEG based on the detected current

Claims

1. 1. A method for regenerating a volume getter pump (NEG) in a vacuum apparatus including an NEG and an ion getter pump, comprising the steps of: reducing an operating voltage of the ion getter pump; recording a current through the ion getter pump to determine a pressure within the vacuum system; controlling a heating element of the NEG as a function of the current of the ion getter pump to heat a NEG material; The method includes:

2. 2. The method of claim 1, wherein the operating voltage of the ion getter pump is at least reduced so that no pumping action remains.

3. 3. The method of claim 1 or 2, wherein the operating voltage is reduced to less than 5 kV.

4. The method of any of claims 1 to 3, wherein the heating element is turned off when the current recorded by the ion getter pump corresponds to a pressure exceeding a first preset pressure.

5. 5. The method of claim 1, wherein the heat output is increased if the current recorded by the ion getter pump corresponds to a pressure lower than a second preset pressure.

6. The first preset pressure and / or the second preset pressure are 10 -5 6. The method according to claim 4 or 5, wherein the mbar corresponds to

7. A vacuum module comprising a volume getter pump (NEG) and an ion getter pump, the NEG and the ion getter pump being directly coupled, the NEG and the ion getter pump being connected to a control unit, the control unit being designed to perform the method according to any one of claims 1 to 6.

8. A vacuum apparatus comprising a volume getter pump (NEG) and an ion getter pump, the NEG and the ion getter pump being arranged separately from each other in the vacuum apparatus, the NEG and the ion getter pump being connected to a control unit, the control unit being designed to perform a method according to any one of claims 1 to 6.

9. 9. A vacuum module according to claim 7 or a vacuum device according to claim 8, comprising a common control unit.

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