A cesium vapor thermal ionizer

Abstract

The utility model discloses a cesium vapor thermal ionization ware, it includes: the shell of cylindrical shape, the middle part of shell is provided with cylindrical negative ion beam flow channel, and the top and bottom of shell are provided with spherical focusing surface and first annular groove respectively, and the side of shell is provided with the through -hole of intercommunication with first annular groove, resistance wire of spring shape, resistance wire is arranged in first annular groove, and both ends of resistance wire all lead out from through -hole, insulating ring, insulating ring sets up in first annular groove, and the top of insulating ring is provided with the second annular groove for containing resistance wire, and the outer edge of second annular groove is provided with the avoidance opening for avoiding both ends of resistance wire, insulating heat -conducting gasket, and insulating heat -conducting gasket is located in the top of insulating ring and is located in first annular groove, the scheme replaces the conventional complex technology that resistance wire and non - heat - conducting alumina are encapsulated respectively in the form of ointment, and then roasting, reduces production cost and production time.

Description

Technical Field

[0001] This utility model relates to the field of thermal ionizer technology, specifically to a cesium vapor thermal ionizer. Background Technology

[0002] The cesium beam sputtering negative ion source (Middleton ion source) can generate a stable, high-intensity negative ion beam containing multiple elements. Its principle is that Cs has an extremely low ionization energy (3.89 eV). By contacting a high work function metal surface (such as Mo) at 1100 °C, Cs atoms are 100% ionized into Cs+ ions. Under the acceleration of an electric field, keV-level energy is generated, which bombards various target materials at high speed, causing atoms (atomic clusters) on the target surface to detach from the surface, producing escaped neutral particles that undergo "charge transfer" with the Cs atom capping layer, capturing the valence electrons of Cs atoms, and generating negative ions containing the target material (molecular and atomic negative ions). These are then extracted by a negative high voltage (keV level) relative to the ground potential and focused to form a high-intensity negative ion beam. It is widely used in techniques such as accelerator mass spectrometry (AMS) and secondary ion mass spectrometry (SIMS) for quantitative and qualitative analysis of trace or long-lived radioactive isotopes.

[0003] As a core functional component of the Middleton ion source, the performance of the cesium vapor thermal ionizer directly determines the quality and contamination level of the final negative ion beam. Its structure mainly consists of three parts: a resistance wire, a high work function metal ionization surface, and an insulating filler. It must meet multiple stringent operating requirements: on the one hand, the cesium vapor thermal ionizer must be insulated from other metal components of the ion source (such as high-voltage electrodes, accelerating electrodes, and target holders) through insulating components to avoid potential interference; on the other hand, by precisely controlling the current applied to the resistance wire, the heating temperature of the cesium vapor thermal ionizer can be adjusted, thereby achieving 100% efficient ionization of Cs atoms and ensuring the generation of a stable Cs⁺ beam to bombard the sputtering target. In the selection of materials for the shell of cesium vapor thermal ionizers, refractory metals with high hardness, stable thermal conductivity, and high work function (tantalum Ta, tungsten W, rhenium Re, molybdenum Mo) are usually used. These materials not only need to withstand the high temperature environment and Cs vapor corrosion during the ionization process for a long time, but also need to resist the impact of scattered ion beams with energy up to several keV. Under this working environment, it is still necessary to maintain the stability of the geometry of the outer curved surface of the ionizer and the purity of the surface for a long time, so as to achieve the long-term stability of Cs ionization quality.

[0004] However, in practical applications, maintaining the long-term stable performance of ionizers, especially the cleanliness of their outer surfaces, is difficult to guarantee effectively. In accelerator mass spectrometry, the outer curved surface of the ionizer is easily contaminated by low work function metals such as copper, aluminum, niobium, and uranium, which reduces its surface work function, causing the ionization efficiency of Cs atoms to be significantly lower than 100%. When this problem becomes increasingly severe, it is usually considered that the ionizer has been "poisoned." Furthermore, the decrease in outer surface purity can also lead to another consequence: enhancing the "memory" effect inside the ion source, significantly improving the mass spectrometer's detection of rare nuclides. Background measurement; due to the high energy during injection, contaminants on the outer surface of the ionizer often penetrate into the metal surface of the ionizer structure, making them virtually impossible to clean using conventional non-destructive methods; however, replacing ionizers is currently extremely costly and their manufacturing process is quite complex; therefore, in accelerator mass spectrometry laboratories, these ionizers can only be used continuously until extreme conditions occur before they have to be replaced; with the rapid development of accelerator mass spectrometers, especially the recent explosive growth in the domestic market, there is an urgent need for an easily obtainable cesium vapor thermal ionizer to solve the long-standing dilemma of ionizer contamination and performance degradation. Utility Model Content

[0005] To address the aforementioned shortcomings of the existing technology, this utility model provides a cesium vapor thermal ionizer that is easy to process and prepare.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A cesium vapor thermal ionizer is provided, comprising: a cylindrical shell with a cylindrical negative ion beam channel in the middle, a spherical focusing surface and a first annular groove at the top and bottom of the shell respectively, and a through hole communicating with the first annular groove on one side of the shell; a spring-shaped resistance wire arranged in the first annular groove, with both ends of the resistance wire leading out from the through hole and connected to an external high-voltage electrode; an insulating ring disposed in the first annular groove, with a second annular groove at the top of the insulating ring for accommodating the resistance wire and insulating it from the shell, and an avoidance opening at the outer edge of the second annular groove for avoiding the two ends of the resistance wire; and an insulating thermally conductive pad located at the top of the insulating ring and confined within the first annular groove.

[0007] Furthermore, the outer shell is made of molybdenum metal with a purity of not less than 99.95%.

[0008] Furthermore, the resistance wire is made of iron-chromium-aluminum alloy, and the maximum withstand temperature of the resistance wire is not less than 1400°C.

[0009] Furthermore, the insulating ring is made of non-thermally conductive alumina material with a purity of not less than 99.5%, the maximum withstand temperature of the insulating ring is not less than 1600°C, and the room temperature insulation resistance is greater than 10 Ω·cm.14 Ω·cm.

[0010] Furthermore, both ends of the resistance wire located at the through hole are fitted with insulating sleeves for insulation and isolation from the outer casing.

[0011] Furthermore, both the insulating thermal pad and the insulating sleeve are made of aluminum nitride ceramic material, with a thermal conductivity of not less than 170 W / (m·K) and a temperature resistance of not less than 1500°C.

[0012] The beneficial effects of this utility model are as follows: 1. This solution uses aluminum nitride ceramic as the thermally conductive material, replacing the traditional and complex process of first encapsulating the resistance wire and non-thermally conductive alumina separately in the form of ointment and then baking it. This greatly simplifies the assembly process of the ionizer, reduces production costs and time. With the reduced cost, users can replace the cesium vapor thermal ionizer periodically, avoiding long-term use and contaminating the components, thus ensuring the high efficiency and low background characteristics of the ion source of the accelerator mass spectrometer.

[0013] 2. The molybdenum outer shell of this solution has high temperature resistance, low expansion, high thermal and electrical conductivity, high hardness, and excellent resistance to cesium vapor corrosion, ensuring that the ionizer is stable under high temperature and high pressure environments, and that the cesium ionization efficiency is maintained at a high level, thus extending the overall service life.

[0014] 3. The modular design of each component in this solution facilitates the subsequent development of cesium vapor thermal ionizers with different shapes and specifications, meets diverse ion source configuration requirements, and promotes the process of domestic substitution. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The above and other objects, features, and advantages of the present invention will become clearer through the drawings. The same reference numerals indicate the same parts in all the drawings. The drawings are not intentionally drawn to scale with actual dimensions; the focus is on illustrating the main idea of ​​the present utility model.

[0016] Figure 1 This is a schematic diagram of the first structure of a cesium vapor thermal ionizer.

[0017] Figure 2 This is a schematic diagram of the second structure of a cesium vapor thermal ionizer.

[0018] Figure 3 This is an internal cross-sectional view of a cesium vapor thermal ionizer.

[0019] Figure 4 This is a schematic diagram of the first structure of the outer shell.

[0020] Figure 5 This is a schematic diagram of the second structure of the outer shell.

[0021] Figure 6 This is a schematic diagram of the insulating ring.

[0022] Figure 7 This is a schematic diagram of the structure of the resistance wire and the insulating sleeve.

[0023] Among them, 1. outer shell, 2. cylindrical negative ion beam channel, 3. spherical focusing surface, 4. first annular groove, 5. through hole, 6. resistance wire, 7. insulating ring, 8. second annular groove, 9. clearance opening, 10. insulating thermal pad, 11. insulating sleeve. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0027] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0028] like Figures 1 to 7As shown, the cesium vapor thermal ionizer of this scheme includes: a cylindrical outer shell 1, a cylindrical negative ion beam channel 2 disposed in the middle of the outer shell 1, a spherical focusing surface 3 and a first annular groove 4 respectively opened at the top and bottom of the outer shell 1, and a through hole 5 communicating with the first annular groove 4 on one side of the outer shell 1. Specifically, the diameter of the spherical focusing surface 3 is 17.5 mm, the diameter of the cylindrical negative ion beam channel 2 is 8.2 mm, and the outer diameter of the first annular groove 4 is 17.85 mm; a spring-shaped resistance wire 6, which is arranged in the first annular groove 4, and both ends of the resistance wire 6 are led out from the through hole 5 and connected to an external high-voltage electrode; and an insulating ring 7, which is disposed in the first annular groove 4 and has an outer diameter of 17.85 mm. mm, the top of the insulating ring 7 is provided with a second annular groove 8 for accommodating the resistance wire 6 and is insulated from the outer shell 1, and the outer edge of the second annular groove 8 is provided with clearance openings 9 for avoiding the two ends of the resistance wire 6; the insulating thermally conductive pad 10 is located at the top of the insulating ring 7 and is limited in the first annular groove 4, which is used for directional conduction of heat from the resistance wire 6 to the outer shell 1 and for insulation between the resistance wire 6 and the outer shell 1.

[0029] As an optional implementation, the outer shell 1 is made of metallic molybdenum with a purity of not less than 99.95%, which has high temperature resistance (melting point 2623℃) and low expansion (average linear coefficient of approximately 5.8 × 10⁻⁶). -6 With high thermal and electrical conductivity (thermal conductivity of approximately 138 W / (m･K)), high hardness (Mohs hardness of approximately 5.5), and excellent resistance to cesium vapor corrosion, the ionizer maintains morphological stability under high temperature and high pressure environments, and its cesium ionization efficiency remains at a high level, thus extending its overall service life.

[0030] As an optional implementation, the resistance wire 6 is made of iron-chromium-aluminum alloy material, and the maximum withstand temperature of the resistance wire 6 is not less than 1400°C.

[0031] As an optional implementation, the insulating ring 7 is made of non-thermally conductive alumina material with a purity of not less than 99.5%, the maximum withstand temperature of the insulating ring 7 is not less than 1600°C, and the room temperature insulation resistance is greater than 10 Ω·cm. 14 Ω·cm.

[0032] As an optional implementation, both ends of the resistance wire 6 located at the through hole 5 are fitted with insulating sleeves 11 for insulation and isolation from the outer casing 1. The insulating thermal pad 10 and the insulating sleeves 11 are both made of aluminum nitride ceramic material with a thermal conductivity of not less than 170 W / (m·K) and a temperature resistance of not less than 1500°C.

[0033] The working principle of this scheme is as follows: by controlling the preset parameters of the high-voltage electrode to output a DC negative high voltage of 18A, the resistance wire 6 connected to the high-voltage electrode is heated. The heat is conducted to the outer shell 1 through the insulating thermal pad 10, and heats the spherical focusing surface 3 to about 1100°C, ionizing cesium vapor to generate Cs+ ions. Under the focusing effect of the spherical focusing surface 3, a Cs+ ion beam is generated to sputter the target material. After the target material is sputtered, a negative ion beam is generated and enters the mass spectrometry analysis system through the cylindrical negative ion beam channel 2 for trace or long-lifetime radioactive isotope analysis.

[0034] In summary, this solution uses aluminum nitride ceramic as the thermally conductive material, replacing the traditional and complex process of separately encapsulating the resistance wire 6 and non-thermally conductive alumina in the form of ointment and then baking it. This significantly simplifies the ionizer assembly process and reduces production costs and time. With the reduced cost, users can periodically replace the cesium vapor thermal ionizer, avoiding long-term use that contaminates components and ensuring the high efficiency and low background characteristics of the accelerator mass spectrometer ion source.

[0035] Although the specific embodiments of the utility model have been described in detail with reference to the accompanying drawings, they should not be construed as limiting the scope of protection of this patent; various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims are still within the scope of protection of this patent.

Claims

1. A cesium vapor thermal ionizer, characterized in that, include: The outer shell is cylindrical, with a cylindrical negative ion beam channel in the middle. The top and bottom of the outer shell are respectively provided with a spherical focusing surface and a first annular groove. A through hole communicating with the first annular groove is provided on one side of the outer shell. A spring-shaped resistance wire is arranged in a first annular groove, and both ends of the resistance wire are led out from a through hole and connected to an external high-voltage electrode. An insulating ring is provided in a first annular groove. The top of the insulating ring is provided with a second annular groove for accommodating the resistance wire and is insulated from the outer shell. The outer edge of the second annular groove is provided with clearance openings for avoiding the two ends of the resistance wire. An insulating thermally conductive pad is located at the top of an insulating ring and confined within a first annular groove.

2. The cesium vapor thermal ionizer according to claim 1, characterized in that, The outer shell is made of metallic molybdenum with a purity of not less than 99.95%.

3. The cesium vapor thermal ionizer according to claim 1, characterized in that, The resistance wire is made of iron-chromium-aluminum alloy and has a maximum withstand temperature of not less than 1400°C.

4. The cesium vapor thermal ionizer according to claim 1, characterized in that, The insulating ring is made of non-thermally conductive alumina material with a purity of not less than 99.5%. The maximum temperature resistance of the insulating ring is not less than 1600°C, and its room temperature insulation resistance is greater than 10 Ω·cm. 14 Ω·cm.

5. The cesium vapor thermal ionizer according to claim 1, characterized in that, Both ends of the resistance wire located at the through hole are fitted with insulating sleeves for insulation and isolation from the outer casing.

6. The cesium vapor thermal ionizer according to claim 5, characterized in that, Both the insulating thermal pad and the insulating sleeve are made of aluminum nitride ceramic material, with a thermal conductivity of not less than 170 W / (m·K) and a temperature resistance of not less than 1500°C.

Images