Vacuum module and vacuum device and method for regenerating a volumetric getter vacuum pump

Abstract

A method for regenerating a volumetric getter pump in a vacuum device having a volumetric getter pump and an ion getter pump, wherein the operating voltage of the ion getter pump is reduced, the current through the ion getter pump is recorded to determine the pressure in the vacuum device, and then a heating element of the NEG is controlled based on the current of the ion getter pump, with the aim of heating the NEG material.

Description

Technical Field

[0001] The invention relates to a vacuum module having a volumetric getter vacuum pump and an ion getter pump, and a vacuum device having a volumetric getter vacuum pump and an ion getter pump, and a method for regenerating a volumetric getter vacuum pump. Background Art

[0002] A large number of industrial and scientific instruments and systems require less than 10 -7 In order to generate such a vacuum in a vacuum system, a combination of various pump systems is usually used. Therefore, a main pump (rough vacuum pump or fore vacuum pump) is usually provided, thereby generating an ultra-high vacuum with a pressure of less than 10 mbar. -1 mbar to 10 -3 The main vacuum pump is combined with the high vacuum pump to produce a low vacuum of less than 10 mbar. -3 mbar to 10 -8 mbar pressure, and possibly in combination with an ultra-high vacuum pump (UHV pump) to produce pressures below 10 -7 mbar pressure. UHV pumps in this case include sorption pumps for the purpose of achieving the required pressure for ultra-high vacuum. Sorption pumps of course include ion getter pumps and volumetric getter vacuum pumps, which are also called getter pumps or volumetric getter pumps.

[0003] A large number of different gases can also be pumped with the aid of ion getter pumps. An ion getter pump typically has two cathodes and one anode, between which a high voltage is applied. With the aid of the high voltage, electrons are accelerated from the cathode to the anode and thus ionize the gas particles, which are then accelerated towards the cathode and adsorbed there, or reach the anode and are injected there by their kinetic energy, so that in both cases they no longer contribute to the gas pressure. A magnetic field applied externally by a permanent magnet increases the probability of ionization of the gas particles by the accelerated electrons. In this case, the pump capacity of the ion getter pump is dictated by the size of the anode and cathode and is therefore limited by the installation space available in the vacuum apparatus.

[0004] The working principle of the known volumetric getter pumps is the chemical adsorption of reactive gaseous media, in particular such as oxygen, nitrogen, hydrogen, etc., although the physical adsorption of hydrogen is dominant. Known volumetric getter pumps also have "non-evaporable getter materials" (NEG). These volumetric getter pumps are called NEG according to their getter material. These pumps have high adsorption speeds and therefore also high pumping speeds, which are generally higher than those of ion getter pumps of the same size. Another advantage of volumetric getter pumps is that they allow hydrogen to be pumped more easily. However, NEGs have a poorer pumping effect on hydrocarbons and NEGs in particular cannot pump inert gases.

[0005] During operation of the NEG, molecules and gas particles from the vacuum device bind to its surface and therefore no longer contribute to the pressure within the vacuum device. Due to these deposits, the active surface of the NEG material, which contributes to the pumping capacity of the NEG, decreases. When no active surface of the NEG remains available, the pumping capacity of the NEG drops to zero. The NEG must then be regenerated. This usually takes place by heating of the NEG material, which is known as "baking". In this process, molecules and gas particles bound to the surface of the NEG material are buried within the NEG material by diffusion, making the active surface of the NEG material available again. Hydrogen is not bound to the surface, but is bound within the solid bulk by means of diffusion. Upon regeneration, the hydrogen is released again and has to be removed from the vacuum chamber by other vacuum pumps. The regeneration process must only be carried out in typically less than 10 -5 mbar or 10 -6 If this is not done, destruction of the NEG material will ensue. Until now, it has been the responsibility of the user of the vacuum equipment to ensure that these required pressures are adhered to.

[0006] Combined pumps comprising a NEG pump and an ion getter pump are known, wherein the ion getter pump is normally switched off during the regeneration process of the NEG, that is, the supply voltage to the ion getter pump is reduced to 0, so that the ion getter pump no longer produces any pump output. This means that filling of the ion getter pump by gas particles escaping from the NEG during bake-out / regeneration of the NEG material is prevented. The maintenance of the vacuum has to be ensured by other pump systems, for example an external turbo pump system.

[0007] Therefore, in existing systems, additional monitoring of the vacuum during the NEG regeneration process is necessary. This requires additional technical steps for measuring the pressure within the vacuum equipment and permanent monitoring to prevent destruction of the NEG material. Summary of the invention

[0008] The technical problem underlying the present invention is to devise a method by which the NEG material of the NEG can be safely and reliably regenerated.

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

[0010] The method according to the invention for regeneration of a volumetric getter pump ('non-evaporable getter pump' - NEG) is applied to a vacuum module with NEG and an ion getter pump, or to a vacuum apparatus with NEG and an ion getter pump. In this case, the NEG and the ion getter pump are always connected to the vacuum apparatus.

[0011] In the method according to the present invention, the operating voltage of the ion getter pump is reduced. However, there is only a reduction in the operating voltage of the ion getter pump. The operating voltage is not reduced to 0, and the operating voltage of the ion getter pump is not turned off. The current through the ion getter pump is then recorded for determining the pressure inside the vacuum equipment. Here, the current through the ion getter pump is proportional to the pressure inside the vacuum equipment. Then, the heating element of the NEG is controlled according to the current of the ion getter pump for the purpose of baking and regeneration of the NEG material. Therefore, the ion getter pump is used to determine the pressure inside the vacuum equipment, and therefore no further technical means are required to determine the pressure inside the vacuum equipment. In contrast, the existing ion getter pump is used to determine the pressure in the vacuum equipment by measuring the current through the ion getter pump. In this case, the ion getter pump is used as a cold cathode vacuum gauge. Since the heating element of the NEG is controlled according to the current of the ion getter pump, the control of the heating element of the NEG occurs directly dependent on the pressure of the vacuum equipment.

[0012] Preferably, the operating voltage of the ion getter pump is reduced at least to a point where there is essentially no longer any pumping action. This prevents material escaping from the NEG material during regeneration from being deposited in / bound to the ion getter pump. For this purpose, it is preferred to reduce the operating voltage of the ion getter pump to less than 5 kV, in particular less than 3 kV, and most preferably less than 1 kV. At such an operating voltage, no appreciable 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] Preferably, if the current recorded by the ion getter pump corresponds to a pressure exceeding a first preset pressure, the heating element is switched off. If the pressure in the vacuum device rises above the first preset pressure, the heating element of the NEG is therefore switched off in order to prevent destruction of the NEG material. Thus, it is ensured at all times that the regeneration of the NEG material is performed only at a pressure without the risk of NEG material destruction.

[0014] Preferably, if the current recorded by the ion getter pump corresponds to a pressure below the second preset pressure, the heat output is increased. Thus, if there is a better vacuum in the vacuum device than required for regeneration of the NEG, the regeneration temperature can be increased and the regeneration can be accelerated due to the increased heat output of the heating element, thereby reducing the regeneration time required to achieve complete regeneration of the NEG material. Typically, the regeneration temperature is increased within about 10 -6 At a pressure of 10 mbar, the regeneration of typical NEG materials takes place at 300°C to 400°C. For example, if the pressure in the vacuum system now drops to 10 -7mbar, regeneration of the NEG material can occur at higher temperatures (e.g. up to 700°C), in which case the required regeneration time can be significantly reduced. Thus, by ensuring that these temperatures are generated only by the heating elements of the NEG where the required pressure is present, rapid regeneration is possible and damage or destruction of the NEG material can be avoided.

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

[0016] Preferably, a continuous regulation of the heat output of the heating element of the NEG to the pressure in the vacuum device can occur. -5 At a first preset pressure of 1000 mbar, the heating element of the NEG can be switched off. At a lower pressure below a second preset pressure, the heat output of the heating element is continuously increased depending on the vacuum in the vacuum device.

[0017] The invention also relates to a vacuum module with a volumetric getter pump (NEG) and an ion getter pump, wherein the NEG and the ion getter pump are directly connected to each other so that there is a combination of the NEG and the ion getter pump. In this case, the NEG and the ion getter pump are connected to a control unit designed to perform the above method.

[0018] The invention also relates to a vacuum device having a volume getter pump (NEG) and an ion getter pump, wherein the NEG and the ion getter pump are arranged separately from each other in the vacuum device. The NEG and the ion getter pump are further connected to a control unit, wherein the control unit is designed to perform the above method.

[0019] Preferably, the control unit comprises a common control unit for the NEG and the ion getter pump, thereby ensuring a compact design. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will now be explained in more detail hereinafter on the basis of preferred embodiments with reference to the accompanying drawings.

[0021] The attached figure is shown below:

[0022] Figure 1 : According to a first embodiment of the pump module of the present invention,

[0023] Figure 2 : a flow chart of the method according to the invention, and

[0024] Figure 3: Graphical representation of the relationship between the current determined by the ion getter pump and the regeneration temperature of the NEG according to the present method. DETAILED DESCRIPTION

[0025] The pump module 10 according to the invention has a flange 12 having a first side 14 and a second side 16 positioned opposite the first side. If the flange 12 is connected to a vacuum device (not shown), the first side 14 faces the vacuum device and is particularly exposed to the vacuum generated inside the vacuum device. The second side 16 is exposed to atmospheric pressure and is arranged outside the vacuum device. By means of known means such as screws and seals, the flange 12 can be connected to the vacuum device in a vacuum-tight manner.

[0026] An ion getter pump 18 is connected to a first side 14 of the flange 12. A volume getter pump (NEG) 20 is arranged on the side of the ion getter pump 18 opposite to the flange 12 side. Therefore, the flange 12 and the NEG 20 are arranged at opposite ends of the ion getter pump. This means that the NEG 20 is not directly connected to the flange 12, but is indirectly connected by means of the ion getter pump 18. Therefore, in the installed state, the ion getter pump 18 and the NEG 20 protrude into the vacuum device and are arranged therein so as to pump gas.

[0027] The flange 12 also has a common conduction 22 through which the high voltage for operation of the ion getter pump 18 and the low voltage for the heating element for regeneration of the NEG are conducted. This means that only one conduction is required, thereby reducing the number of potential leak points of the ultra-high vacuum equipment.

[0028] Since the diameter of the flange or the diameter of the flange face 24 directly located in the vacuum exactly corresponds to or is slightly larger than the base area of ​​the ion getter pump 18 or the NEG 20, the diameter of the flange 12 can be kept small by the stacked or series structure of the NEG 20, the ion getter pump 18 and the flange 12. Therefore, at the time of installation, the NEG 20 and the ion getter pump 18 are introduced through the flange opening and are firmly attached to the vacuum equipment by attaching the flange 12 to the vacuum equipment.

[0029] Use Figure 2According to the method of the present invention shown in, in a first step S01, the operating voltage of the ion getter pump is reduced. In this case, it is not reduced to 0, nor is the power supply voltage of the ion getter pump turned off. On the contrary, the operating voltage of the ion getter pump is only reduced, so that there is effectively no longer any pumping action of the ion getter pump. In this case, the operating voltage or the voltage between the cathode and anode of the ion getter pump can be, for example, 1kV. Under such an operating voltage, the current through the ion getter pump is proportional to the pressure inside the vacuum equipment to which the ion getter pump and the NEG are connected. In a second step S02, the current through the ion getter pump is recorded and, due to the existing ratio, is used to determine the pressure inside the vacuum equipment. In a third step S03 of the method according to the present invention, the heating element of NEG20 is controlled according to the current of the ion getter pump corresponding to the pressure inside the vacuum equipment for the purpose of baking and regeneration of the NEG material.

[0030] Figure 3 is a graphical representation of the relationship between the current determined by the ion getter pump and corresponding to the pressure inside the vacuum apparatus and the NEG material bakeout temperature for regeneration of the NEG material.

[0031] exist Figure 3 In the embodiment of the present invention, the pressure or current of the ion getter pump is plotted on the x-axis relative to the y-axis, which corresponds to the temperature of the heating element. -5 mbar or 10 -6 10 mbar) does not heat up the NEG material, since this could lead to destruction of the NEG material. However, if there is a pressure below the threshold value, baking out and thus regeneration of the NEG material occurs, in which case, as the pressure drops, a higher temperature of the heating element of the NEG exists, so that a faster regeneration of the NEG material can be achieved. If, for example, there is a first baking temperature 42 at a first pressure 40, then there is a second baking temperature 44 at a pressure below the first pressure, which is higher than the first baking temperature 42 of the heating element of the NEG 20. In this case, the correlation between pressure and baking temperature must be nonlinear, as Figure 3 It is illustrated diagrammatically in , but any functional dependency may follow and be adapted depending on the application in question.

[0032] Therefore, a method is proposed whereby regeneration of NEG material in a NEG is performed reliably, safely and efficiently by utilizing existing ion getter pumps.

Claims

1. A method for regenerating NEG in a vacuum apparatus having a volumetric getter pump NEG and an ionic getter pump, wherein reducing the operating voltage of the ion getter pump to a voltage at which the ion getter pump no longer performs any active pumping, but the ion getter pump continues to produce current, recording the current through the ion getter pump to determine the pressure in the vacuum apparatus, in, The current through the ion getter pump is proportional to the pressure within the vacuum apparatus, and The heating element of the NEG is controlled according to the current passing through the ion getter pump, with the aim of heating the NEG material of the NEG while maintaining the operating voltage of the ion getter pump at a voltage at which the ion getter pump no longer performs any active pumping, but the ion getter pump continues to generate the current.

2. The method according to claim 1, in, The operating voltage of the ion getter pump is reduced to less than 5 kV.

3. The method according to claim 1, in, The operating voltage is reduced to less than 3 kV.

4. The method according to claim 1, in, The operating voltage is reduced to less than 1 kV.

5. The method according to one of claims 1 to 4, in, If the current recorded by the ion getter pump corresponds to a pressure above a first preset pressure, the heating element is turned off.

6. The method according to claim 5, in, If the current recorded by the ion getter pump corresponds to a pressure below a second preset pressure, the heat output of the heating element is increased.

7. The method according to claim 6, in, The first preset pressure and / or the second preset pressure corresponds to 10 -5 millibar.

8. The method according to claim 6, in, The first preset pressure and / or the second preset pressure corresponds to 10 -6 millibar.

9. The method according to claim 7 or 8, in, The first preset pressure and the second preset pressure are the same.

10. A vacuum module with a volumetric getter pump, a NEG and an ion getter pump, in, The NEG and the ion getter pump are directly connected, wherein the NEG and the ion getter pump are connected to a control unit, and wherein the control unit is designed to perform the method according to one of claims 1 to 9.

11. The vacuum module according to claim 10, It is characterized in that The control unit is a common control unit.

12. Vacuum equipment with volumetric getter pumps, NEG and ion getter pumps, in, The NEG and the ion getter pump are arranged separately from one another in the vacuum device, wherein the NEG and the ion getter pump are connected to a control unit, and wherein the control unit is designed to perform the method according to one of claims 1 to 9.

13. The vacuum device according to claim 12, It is characterized in that The control unit is a common control unit.

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