Bearing device, and bearing device-equipped laser device

Abstract

To provide a bearing device that is excellent in corrosion resistance to fluorine gas, and is also excellent in dimensional accuracy and durability.SOLUTION: A bearing device to be used in a fluorine gas environment is provided. The bearing device comprises: a magnetic bearing comprising a magnetic body and an electromagnetic coil; and a touchdown bearing for protecting the magnetic bearing, and comprising an inner ring, an outer ring, and a plurality of rolling bodies arranged between the inner ring and the outer ring. The inner ring and the outer ring of the touchdown bearing is made of a NiCrAl alloy.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a bearing device provided with a magnetic bearing and a touchdown bearing, and particularly to a bearing device used in a fluorine gas environment. The present invention also relates to a laser device provided with such a bearing device.

Background Art

[0002] Bearing devices used in a corrosive gas environment such as fluorine gas are known. For example, in Patent Documents 1 to 3, in an excimer laser device containing fluorine gas in a chamber, by coating the surface of a touchdown bearing that holds a cross-flow fan with a thin film of nickel or chromium nitride, corrosion by fluorine gas is prevented.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] When touchdown bearings are used in a fluorine gas environment, they need to be replaced periodically or their corrosion resistance needs to be improved. To improve corrosion resistance, touchdown bearings are made of ceramic material or plated. However, ceramic bearings are expensive, prone to cracking, and cannot be manufactured in large diameters. In the case of plated touchdown bearings, the manufacturing precision deteriorates due to the plating, and there is a risk of plating peeling, which may affect the lifespan in terms of corrosion resistance. Even in configurations where the surface of the touchdown bearing is coated with a thin film of nickel or chromium nitride, as described in Patent Documents 1-3, there are concerns about the durability of the film, and there is also the problem that the mechanical dimensional accuracy of each part of the bearing is poor due to the cumulative error of the film thickness.

[0005] The present invention has been made in view of the above points, and one of its objectives is to provide a bearing device that is excellent in terms of corrosion resistance to fluorine gas, as well as dimensional accuracy and durability. Another objective of the present invention is to provide a laser device equipped with such a bearing device. [Means for solving the problem]

[0006] [Embodiment 1] According to Embodiment 1, a bearing device is provided for use in a fluorine gas environment, comprising a magnetic bearing equipped with a magnetic material and an electromagnetic coil, and a touchdown bearing for protecting the magnetic bearing, the touchdown bearing comprising an inner ring, an outer ring, and a plurality of rolling elements (balls or rollers, etc.) disposed between the inner ring and the outer ring, wherein the inner ring and the outer ring of the touchdown bearing are made of a NiCrAl alloy.

[0007] [Form 2] According to Form 2, in the bearing device of Form 1, the plurality of rolling elements are further composed of a NiCrAl alloy. [Embodiment 3] According to Embodiment 3, in the bearing device of Embodiment 1, the plurality of rolling elements are further composed of ceramics.

[0008] [Form 4] According to Form 4, in any one of Forms 1 to 3, the NiCrAl alloy has a Ni content of 50% by weight or more.

[0009] [Form 5] According to Form 5, in any one of Forms 1 to 4, the NiCrAl alloy has a Cr content of 30% by weight or more.

[0010] [Form 6] According to Form 6, in any one of Forms 1 to 5, the NiCrAl alloy has an Al content of 3% by weight or more.

[0011] [Embodiment 7] According to Embodiment 7, a laser device is provided comprising: a chamber containing a laser gas containing fluorine gas, comprising a fan for circulating the laser gas, a pair of discharge electrodes for discharging the laser gas, and a window arranged to allow laser light to pass through; a bearing device configured to support the fan, comprising a magnetic bearing comprising a magnetic material and an electromagnetic coil; and a touchdown bearing for protecting the magnetic bearing, comprising an inner ring, an outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring, wherein the inner ring and the outer ring of the touchdown bearing are made of a NiCrAl alloy.

[0012] [Embodiment 8] According to Embodiment 8, in the laser device of Embodiment 7, the plurality of rolling elements are further composed of a NiCrAl alloy. [Embodiment 9] According to embodiment 9, in the laser device of embodiment 7, the plurality of rolling elements are further composed of ceramics.

[0013] [Form 10] According to Form 10, in any one of the laser devices from Forms 7 to 9, the NiCrAl alloy has a Ni content of 50% by weight or more.

[0014] [Form 11] According to Form 11, in any one of the laser devices from Forms 7 to 10, the NiCrAl alloy has a Cr content of 30% by weight or more.

[0015] [Form 12] According to Form 12, in any one of the laser devices from Forms 7 to 11, the NiCrAl alloy has an Al content of 3% by weight or more.

[0016] [Embodiment 13] According to embodiment 13, a laser device is provided comprising: a chamber containing a laser gas containing fluorine gas, comprising a fan for circulating the laser gas, a pair of discharge electrodes for discharging the laser gas, and a window arranged to allow laser light to pass through; a bearing device configured to support the fan, comprising a magnetic bearing comprising a magnetic material and an electromagnetic coil; and a touchdown bearing for protecting the magnetic bearing, comprising an inner ring, an outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring, wherein the inner ring and the outer ring of the touchdown bearing are made of a NiCrAl alloy, and the inner ring and the outer ring are Ni plated or ceramic coated.

[0017] [Embodiment 14] According to embodiment 14, in the laser device of embodiment 13, Ni plating or ceramic coating is applied to surfaces of the inner ring and the outer ring other than the rolling surfaces.

[0018] [Embodiment 15] According to embodiment 15, in the laser device of embodiment 14, Ni plating or ceramic coating is applied only to the surface of the inner ring and the outer ring that is perpendicular to the axial direction of the touchdown bearing and is on the side closer to the chamber.

[0019] [Embodiment 16] According to embodiment 16, in a chamber filled with laser gas containing fluorine gas There is provided a laser device including a chamber including a fan for circulating the laser gas, a pair of discharge electrodes for discharging the laser gas, and a window arranged so that laser light passes through; a bearing device configured to support the fan, the bearing device including a magnetic bearing including a magnetic material and an electromagnetic coil, and a touchdown bearing for protecting the magnetic bearing, the touchdown bearing including an inner ring, an outer ring, and a plurality of rolling elements arranged between the inner ring and the outer ring, wherein the inner ring and the outer ring of the touchdown bearing are made of a NiCrAl alloy, and among the surfaces of the inner ring and the outer ring, a surface on a side close to the chamber, which is a plane perpendicular to the axial direction of the touchdown bearing, is covered with a Ni-plated or ceramic-coated metal plate.

Brief Description of the Drawings

[0020] [Figure 1] The figure is a configuration diagram of a gas laser device to which a bearing device according to an embodiment of the present invention is applied. [Figure 2] The figure shows basic chemical and mechanical properties of a NiCrAl alloy applied to a bearing device according to an embodiment of the present invention. [Figure 3] The figure shows the results of an experiment examining the corrosion resistance of a NiCrAl alloy applied to a bearing device according to an embodiment of the present invention against an HF solution. [Figure 4] The figure is a configuration diagram of an excimer laser device according to an embodiment of the present invention. [Figure 5A] The figure is a partially enlarged view of the vicinity of a touchdown bearing in an excimer laser device according to an embodiment of the present invention. [Figure 5B] The figure is a partially enlarged view of the vicinity of a touchdown bearing in an excimer laser device according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0021] Embodiments of the present invention will be described below with reference to the drawings. In the drawings described below, the same or corresponding components are denoted by the same reference numerals, and redundant descriptions are omitted.

[0022] Figure 1 is a configuration diagram of a gas laser apparatus to which a bearing device according to one embodiment of the present invention is applied. The bearing device 100 can be incorporated into, for example, an excimer laser apparatus 10. The excimer laser apparatus 10 may be, for example, an ArF (argon-fluorine) excimer laser, a KrF (krypton-fluorine) excimer laser, a XeCl (xenon-chlorine) excimer laser, or a XeF (xenon-fluorine) excimer laser.

[0023] As shown in Figure 1, the excimer laser apparatus 10 comprises a chamber 20, a through-flow fan 30, a rotating shaft 40, a motor 50, and a bearing device 100. The excimer laser apparatus 10 further includes discharge electrodes and a laser resonator, etc. (not shown).

[0024] Chamber 20 is filled with a mixed gas consisting of a noble gas such as Ar (argon) and a halogen gas such as F2 (fluorine). A once-through fan 30 is installed inside the chamber 20 and circulates the mixed gas within the chamber 20. A motor 50 rotates a rotating shaft 40, which in turn rotates the once-through fan 30 attached to the rotating shaft 40. The rotating shaft 40 and the once-through fan 30 attached to the rotating shaft 40 are supported at both ends of the rotating shaft 40 by bearing devices 100.

[0025] During operation of the excimer laser apparatus 10, a mixed gas is circulated within the chamber 20 by a through-flow fan 30, while pulsed discharge is performed on the discharge electrode. The pulsed discharge excites the noble gas atoms and halogen atoms into the excimer molecule state, generating synchrotron radiation, which in turn causes laser oscillation in the resonator, generating laser light.

[0026] The motor 50 and bearing device 100 are housed in a housing 60 located outside the chamber 20. It is located inside. Furthermore, both ends of the rotating shaft 40 of the through-flow fan 30 protrude from the chamber 20 and extend into the housing 60. The internal space of the housing 60 does not have to be isolated from the internal space of the chamber 20, in which case the same mixed gas (corrosive gas) as in the chamber 20 is present in the housing 60. Alternatively, the internal space of the housing 60 may be isolated from the inside of the chamber 20 by an appropriate structure or material, but if the isolation is not complete, the mixed gas may leak from the chamber 20 into the housing 60. Thus, the bearing device 100 is in a corrosive gas environment.

[0027] The motor 50 comprises a rotor 52 and a stator 54. The rotor 52 is mounted in an annular manner on the outer surface of a portion of the rotating shaft 40 that extends into the housing 60. The stator 54 is installed on the inner wall of the housing 60 so as to face the rotor 52. The motor 50 is configured to generate a rotating magnetic field by passing an electric current through the coils of the stator 54, thereby rotating the rotating shaft 40 on which the rotor 52 is mounted.

[0028] The bearing device 100 includes a magnetic bearing 110 and a touchdown bearing 120. The magnetic bearing 110 supports the rotating shaft 40 of the through-flow fan 30 non-contact using magnetic force. The touchdown bearing 120 is an auxiliary bearing that protects the magnetic bearing 110 to prevent the rotating shaft 40 from colliding with and damaging the magnetic bearing 110 if the magnetic bearing 110 does not function properly (for example, if the power supply to the magnetic bearing 110 is cut off). The rotational speed of the through-flow fan 30 is several thousand rpm (for example, 4000 to 5000 rpm), and the performance of the magnetic bearing 110 depends on the clearance. It is preferable to have as narrow a clearance as possible, and if the clearance of the magnetic bearing 110 is set narrowly, the clearance of the touchdown bearing 120 will become even narrower. For example, the clearance of the touchdown bearing 120 may be set to 0.1 mm or less. Touchdown (contact of the rotating shaft 40 with the touchdown bearing 120) does not occur very often because it occurs in emergencies such as sudden power outages, but it is necessary to safely stop the through-flow fan 30 in emergencies, making it an important technology for ensuring safety.

[0029] The magnetic bearing 110 comprises a rotor-side magnetic body 112 and a housing-side electromagnetic coil 114. The rotor-side magnetic body 112 is mounted in an annular manner on the outer circumferential surface of a portion of the rotating shaft 40 that extends into the housing 60. The housing-side electromagnetic coil 114 is installed on the inner wall of the housing 60 so as to face the rotor-side magnetic body 112. The magnetic bearing 110 is configured to support the rotating shaft 40 of the through-flow fan 30 in a non-contact manner by forming a magnetic attractive force between the rotor-side magnetic body 112 and the housing-side electromagnetic coil 114 by passing an electric current through the housing-side electromagnetic coil 114. The magnetic bearing 110 may further include a sensor (e.g., a magnetic sensor) not shown for detecting the size of the gap between the rotor-side magnetic body 112 and the housing-side electromagnetic coil 114, and may be configured to maintain a constant gap size by adjusting the current to the housing-side electromagnetic coil 114 based on the signal from this sensor.

[0030] The touchdown bearing 120 consists of an inner ring 122, an outer ring 124, and a plurality of rolling elements (balls or rollers) 126. The outer ring 124 is fixed to the inner wall of the housing 60, and the plurality of rolling elements 126 are arranged sandwiched in a groove formed between the outer ring 124 and the inner ring 122. The rolling elements 126 are in contact with the outer circumferential surface of the inner ring 122 and the inner circumferential surface of the outer ring 124, and the inner ring 122 is rotatable relative to the outer ring 124. A gap smaller than the gap between the rotor-side magnetic material 112 and the housing-side electromagnetic coil 114 of the magnetic bearing 110 is provided between the inner circumferential surface of the inner ring 122 (i.e., the surface facing the rotating shaft 40) and the rotating shaft 40. Therefore, if the magnetic bearing 110 does not operate normally (for example, if the magnetic repulsive force of the magnetic bearing 110 is insufficient), the inner ring 122 of the touchdown bearing 120 will come into contact with the rotating shaft 40, thereby preventing contact between the rotor-side magnetic material 112 and the housing-side electromagnetic coil 114 in the magnetic bearing 110. In this way, when the magnetic bearing 110 is not operating normally, the touchdown bearing 120 will come into contact with the magnetic material 112. Instead of bearing 110, the rotating shaft 40 of the through-flow fan 30 is supported in contact. This prevents damage to the magnetic bearing 110.

[0031] As mentioned above, since the mixed gas from the chamber 20 is present in the internal space of the housing 60, the touchdown bearing 120 is constantly exposed to halogen gases such as F2 (fluorine), and if it is made of a material that is not corrosion-resistant, it will corrode.

[0032] To prevent corrosion of the touchdown bearing 120 by halogen gas, it is preferable that the inner ring 122 and outer ring 124 of the touchdown bearing 120 be made of NiCrAl alloy. The multiple rolling elements 126 of the touchdown bearing 120 may also be made of NiCrAl alloy or ceramic. NiCrAl alloy is an alloy containing Ni (nickel), Cr (chromium), and Al (aluminum) as components. For example, the inner ring 122, outer ring 124, and rolling elements 126 of the touchdown bearing 120 may be made of NiCrAl alloy with a Ni content of 50% by weight or more. Furthermore, the Cr content in this NiCrAl alloy may be 30% by weight or more, and the Al content may be 3% by weight or more.

[0033] Furthermore, "made of NiCrAl alloy" means that the entire inner ring 122, the entire outer ring 124, or the entire rolling element 126 of the touchdown bearing 120 is made of NiCrAl alloy (not just the surface, but the interior as well). Therefore, the inner ring 122, outer ring 124, and rolling element 126 of such a touchdown bearing 120 have excellent durability because their surfaces are not coated with a thin film, and can be manufactured with high processing precision. However, the inner ring 122, outer ring 124, or rolling element 126 of the touchdown bearing 120 may have only their surfaces coated with a thin film of NiCrAl alloy (for example, by thin-film formation techniques such as plating or vapor deposition), and their interiors may be made of other metals or ceramics.

[0034] The inventors experimentally confirmed that a NiCrAl alloy with the above composition exhibits extremely high corrosion resistance, particularly to F2 (fluorine) gas. Figure 2 shows the basic chemical and mechanical properties of the NiCrAl alloy used in the experiment. The Ni content was 58.2% by weight, the Cr content was 38% by weight, and the Al content was 3.8% by weight. The tensile strength was 1500 N / mm². 2 The hardness (HRC) was approximately 57. This hardness is comparable to that of SUS440C, indicating that NiCrAl alloy possesses sufficient mechanical properties for use as a touchdown bearing material.

[0035] To investigate the corrosion resistance of NiCrAl alloy to F2 (fluorine) gas, four samples of NiCrAl alloy with the above composition were prepared by cutting it into 20 × 20 × 15 mm blocks. Two of these samples were immersed in a 1% HF (hydrofluoric acid) solution at 45°C for one hour, and the remaining two samples were immersed in a 1% HF solution at 75°C for one hour, and the weight change was measured. The experimental results are shown in Figure 3.

[0036] When the immersion temperature in the HF solution was 45°C, no thinning due to corrosion was observed in any of the samples. On the other hand, when the immersion temperature in the HF solution was 75°C, slight thinning was observed in each sample, but the ratio of thinning to the sample weight before immersion in the HF solution was at most 0.0048%. Furthermore, regarding the appearance of the samples after immersion, a slight loss of gloss was observed in the samples immersed at 75°C, but no significant changes in appearance were observed.

[0037] As described above, the NiCrAl alloy used in the experiment demonstrated high corrosion resistance to HF solution, and therefore, it can be expected to exhibit extremely high corrosion resistance to F2 (fluorine) gas as well.

[0038] Therefore, the NiCrAl alloy touchdown bearing 120 according to this disclosure can maintain normal function without corrosion even in an F2 (fluorine) gas environment. Furthermore, since the inner ring 122, outer ring 124, and rolling elements 126 of the NiCrAl alloy touchdown bearing 120 according to this disclosure can be manufactured by processing (i.e., without coating with a NiCrAl alloy thin film), a touchdown bearing 120 with high dimensional accuracy can be realized.

[0039] Figure 4 is a configuration diagram of an excimer laser apparatus according to one embodiment of the present invention. The excimer laser apparatus 11 comprises a chamber 20, a through-flow fan 30, a rotating shaft 40, a motor 50, a bearing device 100, and a pair of resonant mirrors 70. The chamber 20 comprises a pair of discharge electrodes 22 and windows 23 and 24, which were not shown in Figure 1. The chamber 20, through-flow fan 30, rotating shaft 40, motor 50, and bearing device 100 are the same as those described for the excimer laser apparatus 10 in Figure 1, and redundant explanations are omitted here. The pair of resonant mirrors 70 constitute a laser resonator.

[0040] During operation of the excimer laser apparatus 11, a mixed gas (laser gas) containing a noble gas such as Ar (argon) and a halogen gas such as F2 (fluorine) is circulated within the chamber 20 by a through-flow fan 30, while pulsed discharge is performed on the discharge electrode 22. The pulsed discharge excites the noble gas atoms and halogen atoms into the excimer molecule state, generating synchrotron radiation. The synchrotron radiation travels back and forth within the laser resonator (i.e., between the pair of resonant mirrors 70) through windows 23 and 24, causing laser oscillation and generating laser light.

[0041] Similar to the excimer laser apparatus 10 in Figure 1, in the excimer laser apparatus 11 in Figure 4, the inner ring 122 and outer ring 124 of the touchdown bearing 120 are made of NiCrAl alloy to prevent corrosion of the touchdown bearing 120 by halogen gas. Furthermore, in the excimer laser apparatus 11 according to this embodiment, it is preferable that the surfaces of the inner ring 122 and outer ring 124 of the touchdown bearing 120, which are made of NiCrAl alloy, be plated with Ni (nickel) or a Ni-containing material, or ceramic coated. From the viewpoint of not hindering the driving performance of the touchdown bearing 120 (i.e., avoiding rotational failure due to peeling of the plating from the rolling surface), it is desirable that the areas to which plating or ceramic coating is applied are limited to parts other than the rolling surfaces of the inner ring 122 and outer ring 124, as shown in Figure 5A.

[0042] Furthermore, if plating or ceramic coating is applied to the outer and inner surfaces of the touchdown bearing 120 (i.e., the surfaces perpendicular to the radial direction of the touchdown bearing 120, see Figure 5B), variations in the film thickness can eliminate the radial gap of the touchdown bearing 120, thereby narrowing the control range of the magnetic bearing 110. In addition, the plating on the outer or inner surface may be scratched and peel off, and the peeled-off plating may clog the gap, leading to failure of the touchdown bearing 120. On the other hand, among the surfaces perpendicular to the axial direction of the touchdown bearing 120, the surface closest to the chamber 20 (or through-fan 30) is at a higher risk of corrosion due to halogen gas, and therefore requires superior corrosion resistance.

[0043] Therefore, as shown in Figure 5B, it is more desirable to limit the areas on the inner ring 122 and outer ring 124 of the touchdown bearing 120 that are plated or ceramic coated to areas with a high risk of corrosion, namely, the surfaces of the touchdown bearing 120 perpendicular to the axial direction that are closest to the chamber 20 (or through-fan 30).

[0044] Furthermore, instead of applying plating or ceramic coating to the surfaces of the inner ring 122 and outer ring 124 of the touchdown bearing 120 as described above, a plated or ceramic-coated metal plate such as Al (aluminum) is used to cover the inner ring 122 and outer ring 124 of the touchdown bearing 120. The surface of the outer ring 124 may also be covered with the metal plate. The part covered with the metal plate may be the same as the part to which plating or ceramic coating is applied as described above.

[0045] The touchdown bearing 120 according to this embodiment has extremely high corrosion resistance to halogen gases (especially fluorine). Furthermore, because the surfaces of the inner ring 122 and outer ring 124, which are made of NiCrAl alloy, are plated or ceramic coated, it is possible to suppress the scattering of Cr (chromium) from the inner ring 122 and outer ring 124 into the chamber 20 and contaminating the windows 23 and 24, thereby suppressing a reduction in the lifespan of the chamber 20.

[0046] Furthermore, by limiting the areas to which plating or ceramic coating is applied to parts other than the rolling surfaces of the inner ring 122 and outer ring 124, the above effects can be obtained without hindering the driving performance of the touchdown bearing 120. In addition, by limiting the areas to which plating or ceramic coating is applied to only the surface of the touchdown bearing 120 perpendicular to the axial direction that is closest to the chamber 20 (or through-fan 30), the above effects can be obtained without narrowing the control range of the magnetic bearing 110. Similar effects can also be obtained in a configuration using plated or ceramic-coated metal plates.

[0047] While embodiments of the present invention have been described above based on several examples, the embodiments described above are intended to facilitate understanding of the present invention and do not limit it. The present invention can be modified and improved without departing from its spirit, and of course, its equivalents are included. Furthermore, any combination or omission of the components described in the claims and specification is possible to the extent that at least some of the above-mentioned problems can be solved or at least some of the effects can be achieved. [Explanation of symbols]

[0048] 10. Excimer laser device 20 Chambers 30 Kanryu Fan 40 Rotation axis 50 motors 52 rotors 54 stata 60 Housing 100 Bearing device 110 Magnetic bearing 112 Rotor-side magnetic material 114 Housing-side electromagnetic coil 120 Touchdown Bearing 122 Inner Ring 124 Outer ring 126 Rolling element 11. Excimer laser device 22 Discharge electrode 23, 24 windows 70 Resonant Mirrors

Claims

1. A bearing device for use in a fluorine gas environment, A magnetic bearing comprising a magnetic material and an electromagnetic coil, A touchdown bearing for protecting the magnetic bearing, comprising an inner ring, an outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring, A bearing device comprising the inner ring and outer ring of the touchdown bearing, wherein the inner ring and outer ring of the touchdown bearing are made of NiCrAl alloy.

2. Furthermore, the bearing device according to claim 1, wherein the plurality of rolling elements are made of a NiCrAl alloy.

3. Furthermore, the bearing device according to claim 1, wherein the plurality of rolling elements are made of ceramic.

4. The bearing device according to any one of claims 1 to 3, wherein the NiCrAl alloy has a Ni content of 50% by weight or more.

5. The bearing device according to claim 4, wherein the NiCrAl alloy has a Cr content of 30% by weight or more.

6. The bearing device according to claim 5, wherein the NiCrAl alloy has an Al content of 3% by weight or more.

7. A chamber containing a laser gas that includes fluorine gas, A fan for circulating the laser gas, A pair of discharge electrodes for discharging the laser gas, A window positioned so that the laser beam can pass through, A chamber equipped with, A bearing device configured to support the aforementioned fan, A magnetic bearing comprising a magnetic material and an electromagnetic coil, A touchdown bearing for protecting the magnetic bearing, comprising an inner ring, an outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring, A bearing device comprising the inner ring and outer ring of the touchdown bearing, wherein the inner ring and outer ring of the touchdown bearing are made of NiCrAl alloy, A laser device equipped with the following features.

8. Furthermore, the plurality of rolling elements are made of a NiCrAl alloy, as described in claim 7.

9. Furthermore, the plurality of rolling elements are made of ceramic, as described in claim 7.

10. The laser apparatus according to any one of claims 7 to 9, wherein the NiCrAl alloy has a Ni content of 50% by weight or more.

11. The laser apparatus according to claim 10, wherein the NiCrAl alloy has a Cr content of 30% by weight or more.

12. The laser apparatus according to claim 11, wherein the NiCrAl alloy has an Al content of 3% by weight or more.

13. A chamber containing a laser gas that includes fluorine gas, A fan for circulating the laser gas, A pair of discharge electrodes for discharging the laser gas, A window positioned so that the laser beam can pass through, A chamber equipped with, A bearing device configured to support the aforementioned fan, A magnetic bearing comprising a magnetic material and an electromagnetic coil, A touchdown bearing for protecting the magnetic bearing, comprising an inner ring, an outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring, A bearing device comprising the following, wherein the inner and outer rings of the touchdown bearing are made of NiCrAl alloy, and the inner and outer rings are Ni plated or ceramic coated, A laser device equipped with the following features.

14. The laser apparatus according to claim 13, wherein the surfaces of the inner ring and the outer ring other than the rolling surfaces are coated with Ni plating or ceramic coating.

15. The laser apparatus according to claim 14, wherein Ni plating or ceramic coating is applied only to the surface of the inner ring and the outer ring that is perpendicular to the axial direction of the touchdown bearing and is closer to the chamber.

16. A chamber containing a laser gas that includes fluorine gas, A fan for circulating the laser gas, A pair of discharge electrodes for discharging the laser gas, A window positioned so that the laser beam can pass through, A chamber equipped with, A bearing device configured to support the aforementioned fan, A magnetic bearing comprising a magnetic material and an electromagnetic coil, A touchdown bearing for protecting the magnetic bearing, comprising an inner ring, an outer ring, and a plurality of rolling elements disposed between the inner ring and the outer ring, A bearing device comprising the following, wherein the inner and outer rings of the touchdown bearing are made of NiCrAl alloy, and the surfaces of the inner and outer rings that are perpendicular to the axial direction of the touchdown bearing and closer to the chamber are covered with a Ni-plated or ceramic-coated metal plate, A laser device equipped with the following features.

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