A vacuum ultraviolet discharge tube

Abstract

The present application provides a kind of vacuum ultraviolet discharge tube, the discharge tube includes magnesium fluoride optical window, transition cavity, soft glass cavity and hard glass bubble shell, transition cavity includes multiple transition units different in coefficient of thermal expansion, and multiple transition units are sequentially connected according to the size order of coefficient of thermal expansion, the hard glass bubble shell is connected with the transition unit of the lowest coefficient of thermal expansion, one end of soft glass cavity is connected with the transition unit of the highest coefficient of thermal expansion, and the other end is connected with magnesium fluoride optical window.The technical scheme of the present application is used to solve the technical problem that the magnesium fluoride optical window cannot be reliably sealed in the prior art.

Description

Technical Field

[0001] This invention relates to the field of vacuum ultraviolet standard equipment technology, and in particular to a vacuum ultraviolet discharge tube. Background Technology

[0002] Vacuum ultraviolet photons in the 115nm–200nm band in the space environment primarily originate from radiation generated by the interaction of high-temperature solar plasma, ionospheric plasma, interplanetary high-energy particles, and the Earth's magnetosphere. Therefore, many natural phenomena and laws can be observed by measuring radiation in the vacuum ultraviolet band, such as ionospheric disturbances, the physical composition and changing patterns of the Sun, and Earth's atmospheric airglow and auroras. Simultaneously, many stars in the universe have very high temperatures, with many radiation peaks in the vacuum ultraviolet spectral region. By studying these radiation spectra, we can understand the composition of stars and their physical and chemical changes, learn about the mechanisms of interaction between the Sun and Earth's atmosphere, deduce the content of various trace gases and aerosols in the atmosphere, and achieve real-time monitoring of the atmospheric environment. Detection technology targeting radiation in the 115nm–200nm band can comprehensively detect solar eruptions, the ionosphere, and space environment disturbances, possessing advantages in space environment detection that other technologies lack. With the rapid development of space exploration technology, vacuum ultraviolet remote sensing technology has become an important means of space exploration and an important way for mankind to understand the natural world. Application research in this band has also been launched one after another.

[0003] A crucial aspect of vacuum ultraviolet (VUV) remote sensing technology is the development of VUV space payloads. To ensure the accuracy of these payloads, their spectral responsivity must be calibrated using a VUV light source during development. Furthermore, during the payload's on-orbit operation, real-time on-orbit calibration using its onboard VUV light source is essential. As a core component of the VUV light source, the VUV discharge tube's material composition, sealing methods, and other key technologies are not publicly available internationally, and China currently lacks the capability to develop such technologies, making this a blank area in the field. Summary of the Invention

[0004] To address one of the problems of the prior art, the present invention provides a vacuum ultraviolet discharge tube.

[0005] According to one aspect of the present invention, a vacuum ultraviolet discharge tube is provided. The discharge tube includes a magnesium fluoride optical window, a transition cavity, a soft glass cavity, and a hard glass bulb. The transition cavity includes multiple transition units with different coefficients of thermal expansion, and the multiple transition units are connected sequentially in order of the magnitude of the coefficient of thermal expansion. The hard glass bulb is connected to the transition unit with the lowest coefficient of thermal expansion. One end of the soft glass cavity is connected to the transition unit with the highest coefficient of thermal expansion, and the other end is connected to the magnesium fluoride optical window.

[0006] Furthermore, the absolute value of the difference in the thermal expansion coefficients of any two adjacent transition units is the same constant.

[0007] Furthermore, the material basis system of the transition unit is the Na2O-B2O3-SiO2 system.

[0008] Furthermore, the transition unit includes a first type of transition unit, a second type of transition unit, and a third type of transition unit, and the materials of the first type of transition unit, the second type of transition unit, and the third type of transition unit have different compositions.

[0009] Furthermore, the materials of the first type of transition unit include Na2O, B2O3, SiO2, ZrO2, Al2O3, ZnO, PbO, CaO, K2O, Li2O, BaO, and MgO.

[0010] Furthermore, the composition of the material of the second type of transition unit includes Na2O, B2O3, SiO2, ZrO2, Al2O3, ZnO, PbO, CaO, K2O, Li2O and BaO.

[0011] Furthermore, the materials of the third type of transition unit include Na2O, B2O3, SiO2, ZrO2, Al2O3, ZnO, PbO, CaO, K2O and Li2O.

[0012] Furthermore, the mass percentage of a single component in all components within the first, second, or third type of transition unit is determined by the following formula:

[0013] α=∑α i X i ,

[0014] Where α represents the thermal expansion coefficient of the first, second, or third type of transition unit, α i X represents the coefficient of thermal expansion of a single component. i It represents the mass percentage of a single component in all components.

[0015] Furthermore, the number of transition units is five, including three type I transition units, one type II transition unit, and one type III transition unit. The thermal expansion coefficients of the three type I transition units are 4.7 × 10⁻⁶. -6 / ℃, 5.5×10 -6 / ℃ and 6.3×10 -6 / ℃, the coefficient of thermal expansion of the second type of transition unit is 7.1×10. -6 / ℃, the coefficient of thermal expansion of the third type of transition unit is 8.0×10. -6 / ℃.

[0016] Furthermore, the discharge tube also includes a welding flux with a coefficient of thermal expansion of 8.86 × 10⁻⁶. -6 / ℃, the welding agent is used to seal the soft glass cavity and the magnesium fluoride optical window.

[0017] The present invention provides a vacuum ultraviolet discharge tube. This discharge tube forms a transition cavity by sequentially connecting multiple transition units with different coefficients of thermal expansion in order of their coefficients of thermal expansion. A hard glass bulb is connected to the end of the transition cavity with the lowest coefficient of thermal expansion, and a soft glass cavity is connected to the end with the highest coefficient of thermal expansion. The soft glass cavity is then sealed to a magnesium fluoride optical window. This achieves a reliable sealing of the two materials with significantly different coefficients of thermal expansion, namely the hard glass bulb and the magnesium fluoride optical window. The overall structure has a reliable sealing performance and good airtightness. Furthermore, the magnesium fluoride optical window has high transmittance in the 115nm-200nm ultraviolet band, filling a gap in the domestic vacuum ultraviolet discharge tube market. Attached Figure Description

[0018] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0019] Figure 1 A schematic diagram of the external structure of a vacuum ultraviolet discharge tube according to a specific embodiment of the present invention is shown;

[0020] Figure 2 A schematic diagram of the internal structure of a vacuum ultraviolet discharge tube according to a specific embodiment of the present invention is shown;

[0021] Figure 3 A schematic diagram of the internal connection relationship of a vacuum ultraviolet discharge tube according to a specific embodiment of the present invention is shown. Detailed Implementation

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0025] like Figure 1 As shown, a vacuum ultraviolet discharge tube is provided according to a specific embodiment of the present invention. The discharge tube includes a magnesium fluoride optical window 10, a transition cavity 20, a soft glass cavity 30, and a hard glass bulb 40. The transition cavity 20 includes a plurality of transition units 21 with different coefficients of thermal expansion, and the plurality of transition units 21 are connected in sequence according to the order of the coefficients of thermal expansion. The hard glass bulb 40 is connected to the transition unit 21 with the lowest coefficient of thermal expansion. One end of the soft glass cavity 30 is connected to the transition unit 21 with the highest coefficient of thermal expansion, and the other end is connected to the magnesium fluoride optical window 10.

[0026] In this invention, to ensure the discharge tube meets the required airtightness and can operate normally under vacuum conditions, a hard glass bulb, such as 95% pure glass / B40, is selected, which has excellent airtightness. Simultaneously, to improve the ultraviolet spectral brightness of the discharge tube, magnesium fluoride is used as the optical window of the vacuum ultraviolet discharge tube. The magnesium fluoride optical window 10 is made of tetragonal magnesium fluoride crystal, with a melting point of 1255℃, high hardness, good mechanical properties, stable chemical properties, and is not prone to deliquescence or corrosion. It also has high transmittance in the vacuum ultraviolet band, making it a stable and long-lasting optical window for the discharge tube. However, the hard glass bulb 40 has a low coefficient of thermal expansion, while the magnesium fluoride optical window 10 has a high coefficient of thermal expansion. The significant difference in their coefficients means that directly sealing them together will generate substantial thermal stress, leading to micro-cracks or even breakage of both the magnesium fluoride optical window 10 and the hard glass bulb 40. This compromises the airtightness of the discharge tube and severely affects its quality and stability. To address this issue, the present invention provides a transition cavity 20 and a soft glass cavity 30 between the magnesium fluoride optical window 10 and the hard glass bulb 40. The transition unit with the lowest coefficient of thermal expansion in the transition cavity 20 has the smallest difference in coefficient of thermal expansion with the hard glass bulb 40, and the two are sealed together. This transition unit is then sealed with another transition unit with the smallest difference in coefficient of thermal expansion, and so on, sealing the remaining transition units together. The last transition unit has the highest coefficient of thermal expansion in the transition cavity 20, while the coefficient of thermal expansion of the soft glass cavity 30 is between that of the last transition unit and the magnesium fluoride optical window 10. Through this configuration, the large difference in coefficient of thermal expansion between the magnesium fluoride optical window 10 and the hard glass bulb 40 can be divided into multiple smaller differences in coefficient of thermal expansion. By utilizing the progression of the coefficient of thermal expansion between the components, the sealing interface transitions from hard glass to a soft glass material that can be matched and sealed with magnesium fluoride, making the sealing between the magnesium fluoride optical window 10, the transition cavity 20, the soft glass cavity 30, and the hard glass bulb 40 stable and reliable, ensuring that the airtightness meets the standards.

[0027] This configuration provides a vacuum ultraviolet discharge tube. The tube forms a transition cavity 20 by sequentially connecting multiple transition units 21 with different coefficients of thermal expansion in ascending order of their coefficients. A rigid glass bulb 40 is connected to the end of the transition cavity 20 with the lowest coefficient of thermal expansion, and a soft glass cavity 30 is connected to the end with the highest coefficient of thermal expansion. The soft glass cavity 30 is then sealed to a magnesium fluoride optical window 10. This achieves a reliable seal between the rigid glass bulb 40 and the magnesium fluoride optical window 10, two materials with significantly different coefficients of thermal expansion. The overall structure provides a reliable seal and good airtightness. Furthermore, the magnesium fluoride optical window 10 has high transmittance in the 115nm–200nm ultraviolet band, filling a gap in domestic vacuum ultraviolet discharge tube technology. Compared with existing technologies, the technical solution of this invention solves the technical problem that existing technologies cannot reliably seal magnesium fluoride optical windows.

[0028] To further improve the reliability of the overall sealing structure of the discharge tube, preferably, the absolute value of the difference in the thermal expansion coefficients of any two adjacent transition units 21 is the same constant. That is, the thermal expansion coefficients of the transition units 21 form an arithmetic sequence, and the tolerance is determined according to actual needs. As a specific embodiment of the present invention, the gradient of the thermal expansion coefficients of adjacent transition units 21, i.e., the tolerance, is (0.8~0.9)×10. -6 Within a temperature range of / ℃, this configuration allows each transition unit 21 to bear relatively uniform thermal stress, thereby improving the reliability of the transition cavity 20.

[0029] Furthermore, the material of the transition unit 21 is selected according to actual needs. As a specific embodiment of the present invention, the basic material system of the transition unit 21 is the Na2O-B2O3-SiO2 system. This system material is a microcrystalline glass with a wide range of thermal expansion coefficients. By adjusting the components in the system, materials with different thermal expansion coefficients can be obtained, while also exhibiting good thermal stability. Using this system material to fabricate the transition unit 21 can meet the requirements of different thermal expansion coefficients for each transition unit 21, and also provides good stability.

[0030] Furthermore, to precisely control the coefficient of thermal expansion of each transition unit 21, ensuring it is as close as possible to or even exactly at the expected value, and to possess good chemical stability, other components, such as alkali metal oxides, can be added to the Na2O-B2O3-SiO2 base system for adjustment. The transition units 21 are classified into different categories based on the added components; for example, transition units 21 include first-type, second-type, and third-type transition units, with different material compositions for each category.

[0031] As a specific embodiment of the first type of transition unit, the material composition of the first type of transition unit includes Na2O, B2O3, SiO2, ZrO2, Al2O3, ZnO, PbO, CaO, K2O, Li2O, BaO, and MgO. This compositional configuration yields transition units with low coefficients of thermal expansion and good chemical stability and mechanical properties.

[0032] As a specific embodiment of the second type of transition unit, the material composition of the second type of transition unit includes Na2O, B2O3, SiO2, ZrO2, Al2O3, ZnO, PbO, CaO, K2O, Li2O, and BaO. Compared with the first type of transition unit, the second type of transition unit reduces the amount of MgO, thus obtaining a material with a higher coefficient of thermal expansion than the first type of transition unit.

[0033] As a specific embodiment of the third type of transition unit, the material composition of the third type of transition unit includes Na2O, B2O3, SiO2, ZrO2, Al2O3, ZnO, PbO, CaO, K2O, and Li2O. Compared with the second type of transition unit, the third type of transition unit reduces the BaO component, thus obtaining a material with a higher coefficient of thermal expansion than the second type of transition unit.

[0034] Furthermore, the component ratio of transition unit 21 is determined based on the expected coefficient of thermal expansion of transition unit 21 and the summation coefficient of thermal expansion of each component. That is, the mass percentage of a single component in all components of the first, second, or third type of transition unit is determined by the following formula:

[0035] α=∑α i X i ,

[0036] Where α represents the thermal expansion coefficient of the first, second, or third type of transition unit, α i X represents the coefficient of thermal expansion of a single component. i It represents the mass percentage of a single component in all components.

[0037] Furthermore, considering only the impact of the coefficient of thermal expansion on sealing stability, a greater number of transition units 21, i.e., a smaller gradient of the coefficient of thermal expansion between adjacent transition units 21, results in a more stable seal and reduces the likelihood of cracks or even breakage. However, from a manufacturing perspective, a greater number of transition units 21 makes it more difficult to guarantee the coaxiality and flatness of the transition cavity 20 as a whole, which can negatively impact airtightness and complicate the manufacturing process. Therefore, in actual design and manufacturing, these factors should be comprehensively considered to determine the appropriate number of transition units 21 and the gradient of their coefficients of thermal expansion. In a specific embodiment of the present invention, the number of transition units 21 is five, including three first-type transition units, one second-type transition unit, and one third-type transition unit. The coefficients of thermal expansion of the three first-type transition units are 4.7 × 10⁻⁶. -6 / ℃, 5.5×10 -6 / ℃ and 6.3×10 -6 / ℃, the coefficient of thermal expansion of the second type of transition unit is 7.1×10. -6 / ℃, the coefficient of thermal expansion of the third type of transition unit is 8.0×10. -6 / ℃. The composition of the components in the five transition units 21 is shown in the example in Table 1. Transition units one, two, and three are all type I transition units, with thermal expansion coefficients of 4.7 × 10⁻⁶ respectively. -6 / ℃, 5.5×10 -6 / ℃ and 6.3×10 -6 / ℃, Transition unit four is a type II transition unit with a thermal expansion coefficient of 7.1×10. -6 / ℃, Transition unit five is a type III transition unit with a thermal expansion coefficient of 8.0×10. -6 / ℃, transition units one, two, three, four, and five are sequentially sealed together. The rigid glass bulb 40 is sealed to transition unit one, transition unit five is sealed to the soft glass cavity 30, and the soft glass cavity 30 is then sealed to the magnesium fluoride optical window 10. The thermal expansion coefficient gradient between adjacent transition units is (0.8~0.9)×10. -6 / ℃.

[0038] Table 1 Examples of the composition of the five transition units

[0039]

[0040] To further improve the connection reliability between the soft glass cavity 30 and the magnesium fluoride optical window 10, the discharge tube in this invention also includes a welding agent with a coefficient of thermal expansion of 8.86 × 10⁻⁶. -6 / ℃, the welding flux is used to seal the flexible glass cavity 30 and the magnesium fluoride optical window 10. The coefficient of thermal expansion of the welding flux is between that of the flexible glass cavity 30 and the magnesium fluoride optical window 10. This configuration further reduces the instability risk caused by the difference in the coefficients of thermal expansion and prevents the flexible glass cavity 30, the magnesium fluoride optical window 10, and the joint between them from cracking.

[0041] In addition, please refer to Figure 2 In an example, the vacuum ultraviolet discharge tube proposed in this invention also includes an aperture 50, an electrode box 60, and a lamp head 70. The lamp head 70 is sealed to the end of a hard glass bulb 40, forming a sealed space together with the hard glass bulb 40, the soft glass cavity 30, the transition cavity 20, and the magnesium fluoride optical window 10. The aperture 50 and the electrode box 60 are both located within this sealed space and are connected. The aperture 50 uses nickel (Ni) material with a purity of 99.5% or higher, and its specific dimensions are used to limit the divergence angle of the emitted light. Multiple core posts 71 are inserted into the bottom of the lamp head 70. The core posts 71 are sealed and fixed to the lamp head 70 using hard glass, such as 95% B40. The core posts 71 serve two purposes: firstly, to support the entire vacuum ultraviolet discharge tube; secondly, any three of them are used to electrically connect the power supply to the electrode box 60 to provide power. Figure 3 As shown, one core column is connected to the positive terminal of the power supply and the anode of the electrode box 60 at both ends, the other core column is connected to the negative terminal of the power supply and the cathode of the electrode box 60 at both ends, and the third core column is connected to the ground wire of the power supply and the ground wire of the electrode box 60 at both ends. With this configuration, the power supply provides power to the electrode box 60 through the core column 71. When excited, the electrode box 60 emits radiation light, which passes through the aperture 50 and reaches the magnesium fluoride optical window 10. The ultraviolet light band is emitted through the magnesium fluoride optical window 10. The vacuum ultraviolet discharge tube proposed in this invention is mainly used to generate vacuum ultraviolet radiation in the 115nm–200nm wavelength range. After metrological calibration, a standard vacuum ultraviolet spectral radiance value is obtained, which serves as a standard light source for metrological calibration of other calibrated equipment.

[0042] In summary, this invention provides a vacuum ultraviolet discharge tube. This tube forms a transition cavity by sequentially connecting multiple transition units with different coefficients of thermal expansion in order of their magnitude. A rigid glass bulb is connected to the end of the transition cavity with the lowest coefficient of thermal expansion, and a soft glass cavity is connected to the end with the highest coefficient of thermal expansion. The soft glass cavity is then sealed to a magnesium fluoride optical window. This achieves a reliable seal between the rigid glass bulb and the magnesium fluoride optical window, two materials with significantly different coefficients of thermal expansion. The overall structure provides a reliable seal and good airtightness. Furthermore, the magnesium fluoride optical window has high transmittance in the 115nm–200nm ultraviolet band, filling a gap in domestic vacuum ultraviolet discharge tube technology. Compared with existing technologies, the technical solution of this invention solves the technical problem that existing technologies cannot reliably seal the magnesium fluoride optical window.

[0043] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0044] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A vacuum ultraviolet discharge tube, characterized in that, The discharge tube includes a magnesium fluoride optical window (10), a transition cavity (20), a soft glass cavity (30), and a hard glass bulb (40). The transition cavity (20) includes multiple transition units (21) with different coefficients of thermal expansion, and the multiple transition units (21) are connected in sequence according to the order of their coefficients of thermal expansion. The hard glass bulb (40) is connected to the transition unit (21) with the lowest coefficient of thermal expansion. One end of the soft glass cavity (30) is connected to the transition unit (21) with the highest coefficient of thermal expansion, and the other end is connected to the magnesium fluoride optical window (10). The discharge tube also includes a welding agent used to seal the soft glass cavity (30) and the magnesium fluoride optical window (10); The material basis system of the transition unit (21) is Na2O-B2O3-SiO2 system; The transition unit (21) includes a first type of transition unit, a second type of transition unit and a third type of transition unit, wherein the materials of the first type of transition unit, the second type of transition unit and the third type of transition unit have different compositions; The materials of the first type of transition unit include Na2O, B2O3, SiO2, ZrO2, Al2O3, ZnO, PbO, CaO, K2O, Li2O, BaO and MgO; The composition of the material of the second type of transition unit includes Na2O, B2O3, SiO2, ZrO2, Al2O3, ZnO, PbO, CaO, K2O, Li2O and BaO; The materials of the third type of transition unit include Na2O, B2O3, SiO2, ZrO2, Al2O3, ZnO, PbO, CaO, K2O and Li2O.

2. The discharge tube according to claim 1, characterized in that, The absolute value of the difference in the thermal expansion coefficients of every two adjacent transition units (21) is the same constant.

3. The discharge tube according to claim 1 or 2, characterized in that, The mass percentage of a single component in all components in the first, second, or third type of transition unit is determined by the following formula: α＝∑α i X i ， Wherein, α represents the coefficient of thermal expansion of the first type of transition unit, the second type of transition unit, or the third type of transition unit. i X represents the coefficient of thermal expansion of a single component. i It represents the mass percentage of a single component in all components.

4. The discharge tube according to claim 3, characterized in that, The number of transition units (21) is five, including three first-type transition units, one second-type transition unit, and one third-type transition unit. The thermal expansion coefficients of the three first-type transition units are 4.7 × 10⁻⁶. -6 / ℃, 5.5×10 -6 / ℃ and 6.3×10 -6 / ℃, the coefficient of thermal expansion of the second type of transition unit is 7.1×10. -6 / ℃, the coefficient of thermal expansion of the third type of transition unit is 8.0×10. -6 / ℃.

5. The discharge tube according to claim 4, characterized in that, The coefficient of thermal expansion of the welding flux is 8.86 × 10⁻⁶. -6 / ℃.

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