Liquid cesium heating evaporation feed-in device and method for negative ion beam source

Abstract

The invention relates to the technical field of fusion device auxiliary devices, in particular to a liquid cesium heating evaporation feed-in device and method for a negative ion beam source. According to the technical scheme, the device comprises a liquid metal cesium storage and evaporation unit, a cesium steam transmission unit, a heating temperature control unit and a cesium steam feed-in nozzle. In order to solve the problems that an existing liquid metal cesium feed-in technology is poor in vacuum sealing performance, inaccurate in temperature control, prone to steam condensation, inconvenient to maintain and the like, high-reliability vacuum isolation and non-stop maintenance are achieved through the design that double corrugated pipe sealing valves are connected in series, and the segmented independent high-precision temperature control technology is innovatively introduced; the stable temperature gradient is established between the transmission pipeline and the cesium crucible, so that directional stable transmission and wide-range continuous accurate regulation and control of cesium steam are realized, the negative ion yield and the beam source operation stability are remarkably improved, the operation safety and the maintenance convenience are greatly enhanced, and the service life of key parts is effectively prolonged.

Description

Technical Field

[0001] This invention relates to the field of auxiliary devices for fusion devices, and in particular to a liquid cesium heating and evaporation feeding device and method for a negative ion beam source. Background Technology

[0002] Magnetic confinement fusion, a cutting-edge technology promising to solve humanity's future energy problems, faces the core challenge of achieving and maintaining a high-temperature, high-pressure state for the core plasma. To achieve fusion ignition conditions, the plasma ion temperature must exceed 10 keV, which strongly relies on an efficient, high-power auxiliary heating system. Among various heating methods, neutral beam injection systems based on negative ion sources have become an indispensable key subsystem for current large tokamas and future fusion reactors (such as ITER and CFETR) due to their higher energy injection efficiency and deeper deposition profile. In this system, the performance of the negative ion beam source—especially H... - The generation efficiency, beam intensity, and stability of ions directly determine the overall heating effect of the neutral beam and the operational efficiency of the fusion device. Liquid cesium, due to its unique physicochemical properties, plays an irreplaceable role in increasing negative ion yield. Cesium has a low melting point (28.5℃) and a high saturated vapor pressure, making it easy to evaporate at moderate temperatures. Its core function lies in the fact that the cesium vapor generated by evaporation, after entering the ion source, selectively adsorbs onto the surface of the plasma electrode (such as a cesium-modified electrode), forming a sub-monoatom layer. This layer significantly reduces the effective work function of the metal surface, thereby greatly promoting the generation and extraction of surface H⁻ ions, which is a key technological approach to obtaining high-current, high-brightness negative ion beams. Therefore, a device capable of continuously, stably, and controllably feeding liquid cesium is the core hardware foundation for ensuring the high performance and long lifespan of the negative ion source.

[0003] However, existing liquid metal cesium feeding devices generally suffer from a series of technical bottlenecks and reliability issues, which restrict the further development of negative ion beam source performance. These issues are mainly reflected in the following aspects:

[0004] Insufficient reliability of vacuum seals: Most existing devices use a single valve as a means of vacuum isolation. During cesium loading, crucible replacement, or routine maintenance, the risk of failure at a single seal point or operational disturbance can easily lead to system vacuum leakage. This not only disrupts the high-vacuum environment at the core of the fusion device and introduces impurity gases to contaminate the plasma, but also poses potential environmental pollution and personnel safety hazards due to cesium vapor leakage.

[0005] Coarse temperature control can easily lead to unstable cesium vapor condensation and feeding: Traditional designs often use overall heating of the crucible and transmission pipeline or coarsely zoned heating, resulting in poor temperature control accuracy (typically greater than ±5℃). This makes it impossible to form a precise and stable temperature gradient along the transmission path. This often leads to condensation and deposition of cesium vapor in lower-temperature pipeline sections or flange connections, causing not only ineffective cesium loss but also clogging of the vapor channel. This results in random fluctuations in the amount of cesium fed to the electrode surface, directly affecting the stability and repeatability of negative ion production.

[0006] Poor controllability and narrow adjustment range of evaporation rate: Due to limitations in heating methods and temperature control accuracy, existing devices struggle to achieve precise and wide-range linear adjustment of the evaporation rate of cesium. The evaporation rate is either unstable or can only operate within a narrow, fixed range, making it impossible to flexibly adapt to the optimal cesium feed rate of the ion source under different discharge modes (such as start-up, flat-top, and decay) and different beam current requirements. This limits the adaptability of the beam source to different operating conditions and the scope for performance optimization.

[0007] The lack of an effective cesium inventory monitoring and safety maintenance mechanism is a significant problem: during device operation, the remaining cesium level in the crucible is often a "black box," making real-time or convenient monitoring impossible. Cesium depletion could lead to sudden experimental interruptions, while overfilling could cause safety issues during heating. Furthermore, existing devices typically require "vacuum breaking" of the entire negative ion source and even the upstream vacuum system when cesium needs replenishment or maintenance. This process is cumbersome, time-consuming, and severely disrupts experimental continuity, representing a major efficiency bottleneck for modern fusion experiments aiming for long pulses or quasi-continuous operation.

[0008] In summary, existing liquid cesium metal feeding technologies have significant shortcomings in terms of sealing reliability, process controllability, and operational stability. To meet the stringent requirements of next-generation fusion devices for higher performance, greater reliability, and longer operating cycles of the negative ion beam source, this application proposes a liquid cesium heating and evaporation feeding device and method for the negative ion beam source. Summary of the Invention

[0009] The purpose of this invention is to address the significant deficiencies in the existing liquid cesium metal feeding technology in terms of sealing reliability, process controllability, and operational stability, and to propose a liquid cesium heating and evaporation feeding device and method for a negative ion beam source.

[0010] In a first aspect, the present invention provides a liquid cesium heating and evaporation feeding device for a negative ion beam source, comprising:

[0011] A liquid cesium metal storage and evaporation unit, including a crucible for containing liquid cesium metal;

[0012] A cesium vapor transmission unit includes a transmission pipe connected to the outlet of the crucible, and a cesium vapor feed nozzle is installed at the end of the transmission pipe.

[0013] The heating and temperature control unit includes a first heating component, a second heating component, and a constant temperature control heating chamber;

[0014] The first heating component is used to independently heat the crucible, and the second heating component is used to independently heat the transmission pipe;

[0015] The constant temperature control heating box is used to independently control the heating power of the first heating component and the second heating component, so that the temperature of the transmission pipe is higher than the temperature of the crucible, thereby forming a temperature gradient in the transmission pipe that drives the cesium vapor to diffuse into the cesium vapor feed nozzle.

[0016] Optionally, a vacuum isolation unit is also included, comprising a first vacuum valve and a second vacuum valve arranged in series on the cesium vapor transmission path; wherein the first vacuum valve is disposed near the crucible, and the second vacuum valve is disposed near the cesium vapor feed nozzle; the first vacuum valve and the second vacuum valve are detachably connected.

[0017] Optionally, both the first vacuum valve and the second vacuum valve are bellows-sealed valves, and the leakage rate of the bellows-sealed valve is not higher than 1×10⁻⁶. -10 Pa·m 3 / s.

[0018] Optionally, the crucible is sealed to the end of the transmission pipe via a CF16 blind flange, and the CF16 blind flange and the crucible are sealed together by an oxygen-free copper sealing ring.

[0019] Optionally, both the first heating component and the second heating component include a resistance wire wound around the outside of the corresponding heated component, an insulating sleeve fitted over the resistance wire, and an outermost heat insulation layer. The insulating sleeve is an insulating sleeve with a temperature resistance of not less than 300°C, and the heat insulation layer is a heat insulation layer.

[0020] Optionally, the transmission pipe is a stainless steel pipe with polished inner wall and a surface roughness Ra≤0.8μm. The temperature control accuracy of the constant temperature control heating box is ±1℃. The constant temperature control heating box controls the heating temperature of the transmission pipe to 200-240℃ and controls the heating temperature of the crucible to 150-190℃.

[0021] In a second aspect, the present invention provides a method for feeding liquid cesium by heating and evaporating it into a negative ion beam source, applied to a liquid cesium heating and evaporating feeding device for a negative ion beam source as described in the first aspect, comprising the following steps:

[0022] Independent heating control is implemented for the crucible containing liquid cesium metal and the transmission pipeline used to transfer cesium vapor;

[0023] The heating temperature of the transmission pipe is controlled to be higher than that of the crucible, so as to form a temperature gradient in the transmission pipe that drives the cesium vapor to diffuse from the crucible to the cesium vapor feed nozzle;

[0024] The cesium vapor generated by heating and evaporating the liquid cesium metal in the crucible moves directionally along the transmission pipe under the action of the temperature gradient and is ejected through the cesium vapor feed nozzle.

[0025] Optionally, the evaporation rate of cesium can be controlled within the range of 0.1-5 mg / h by adjusting the heating power of the crucible.

[0026] Optionally, before heating is applied to the transfer pipe and the crucible, the feeding device containing the crucible and the transfer pipe is evacuated to achieve and maintain a high vacuum state.

[0027] Optionally, when it is necessary to replenish the liquid cesium metal in the crucible or to maintain the crucible, the first vacuum valve and the second vacuum valve provided on the transmission pipeline are closed, and the connection between the first vacuum valve and the second vacuum valve is disconnected, so as to perform offline operation on the crucible while maintaining the downstream vacuum system without damage.

[0028] Compared with the prior art, this application includes at least one of the following beneficial technical effects:

[0029] A dual-bellows sealing valve series design is adopted to form a two-stage high-vacuum isolation barrier. The leakage rate of each valve is no higher than 1×10⁻⁶. -10 Pa·m 3 / s ensures extremely high static sealing performance of the system. This design allows for effective isolation of the fusion device's main vacuum system during cesium loading, crucible disassembly, or maintenance, enabling online maintenance without shutting down the system. This completely avoids vacuum breaches in the entire experimental system due to maintenance operations, greatly improving the device's operational reliability and experimental efficiency.

[0030] By employing two independent heating circuits and a high-precision PID constant temperature control system, the cesium crucible and the transmission pipeline are independently and precisely temperature-controlled. A stable positive temperature gradient is created by setting the pipeline temperature higher than the crucible temperature. This thermodynamically drives the cesium vapor to diffuse directionally towards the nozzle and ensures that the vapor remains superheated throughout the transmission process. This fundamentally solves the technical problem of cesium vapor condensation and deposition within the pipeline, leading to channel blockage and unstable feed.

[0031] Based on high-precision temperature control, the cesium evaporation rate can be broadly, continuously, and linearly adjusted within the range of 0.1 mg / h to 5 mg / h by fine-tuning the temperature of the crucible heating section. This allows the device to flexibly and precisely adapt to the optimal cesium requirements of the negative ion source under different discharge stages and beam power conditions, providing a key means to optimize negative ion yield and beam quality, and significantly improving the performance and adaptability of the negative ion beam source.

[0032] The detachable connection between the two valves, combined with the offline-operable cesium crucible module, makes cesium level checks, replenishment, and component replacement safe and convenient. The main vacuum environment remains unaffected during maintenance, while also avoiding the risk of operators being directly exposed to the high vacuum system or cesium vapor environment. This design also facilitates real-time estimation and monitoring of cesium consumption, preventing experimental interruptions due to cesium depletion, and comprehensively improving the system's operational safety and maintenance convenience.

[0033] Stable cesium feed avoids the impact or contamination of plasma electrodes caused by cesium quantity fluctuations; efficient vapor transport reduces the deposition and waste of cesium in non-target areas; and reliable vacuum sealing reduces the damage to the ion source caused by the intrusion of impurity gases. These factors work together to effectively extend the service life of key components such as the cesium-modified electrodes in the negative ion source and reduce the long-term operation and maintenance costs of the fusion device.

[0034] In summary, this invention addresses the problems of poor vacuum sealing, inaccurate temperature control, easy vapor condensation, and inconvenient maintenance in existing liquid cesium metal feeding technologies. It achieves highly reliable vacuum isolation and maintenance without shutting down the system by employing a series design of dual-bellows sealing valves. Furthermore, it innovatively introduces segmented independent high-precision temperature control technology to establish a stable temperature gradient between the transmission pipeline and the cesium crucible. This enables directional and stable transmission of cesium vapor and wide-range continuous and precise control. The device significantly improves negative ion yield and beam source operational stability, while greatly enhancing operational safety and maintenance convenience, and effectively extending the lifespan of key components. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a liquid cesium heating and evaporation feeding device for a negative ion beam source;

[0036] Figure 2 A schematic diagram of the structure of the liquid cesium heating and evaporation feeding device above the negative ion beam source;

[0037] Figure 3 This is a schematic diagram of the structure of the liquid cesium heating and evaporation feeding device at the bottom of the negative ion beam source.

[0038] Reference numerals: 1. Bellows sealing valve; 2. Pipeline; 3. CF16 blind flange; 4. Crucible; 5. Thermocouple; 6. Resistance wire; 7. Insulating sleeve; 8. Insulation layer; 9. Thermostatic control heating box; 10. Nozzle; 11. Fusion device vacuum chamber; 201. Pipeline 1; 202. Pipeline 2. Detailed Implementation

[0039] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0040] Example 1: Refer to Figures 1 to 3 This embodiment provides a liquid cesium heating and evaporation feeding device for a negative ion beam source.

[0041] 1. Overall structure and connection relationships of the device

[0042] The device mainly consists of a vacuum isolation and connection module, a cesium storage and evaporation module, a steam transmission and guiding module, and a high-precision heating and temperature control module, and is connected to the negative ion source electrode area of ​​the fusion device through a cesium feed nozzle 10.

[0043] Vacuum Isolation and Connection Module: The core of this module consists of two bellows-sealed valves 1 arranged in series, defined as the first sealing valve (near the cesium source side) and the second sealing valve (near the ion source side). The two valves are connected by a detachable stainless steel pipe 2. This embodiment uses a compression fitting connection to facilitate disconnection without damaging the downstream fusion device vacuum chamber 11. The bellows-sealed valves 1 are selected with a leakage rate ≤ 1×10⁻¹. 0 The high vacuum model (Pa·m³ / s) ensures extremely high static sealing performance.

[0044] Cesium storage evaporation module: This includes a stainless steel cesium crucible 4 and a CF16 blind flange 3 (which also serves as the crucible lid) sealed to it. The cesium crucible 4 has a volume of 20 mL and is manufactured using a one-piece molding process to reduce weld seams and improve reliability. The interface between the CF16 blind flange 3 and the cesium crucible 4 uses an oxygen-free copper sealing ring and is evenly tightened with multiple M4×14 mm bolts to ensure long-term sealing effectiveness under high-temperature (150-190℃) conditions. A short stainless steel connecting pipe is welded to the CF16 blind flange 3 for connection to the output end of the first sealing valve via a compression fitting.

[0045] Steam transmission and guiding module: The main body is a section of stainless steel pipe 2 with a precision-polished inner wall, made of 316L stainless steel, with an inner wall surface roughness Ra ≤ 0.8 μm. One end of the pipe is connected to a second sealing valve via a clamp, and the other end is connected to a cesium-feeding nozzle 10 at a specific angle. This nozzle is designed to directly align with and extend into the plasma electrode of the negative ion source. The smooth inner wall greatly reduces condensation and adhesion losses of cesium vapor during transmission.

[0046] High-precision heating and temperature control module: includes two independent heating circuits and a constant temperature control heating chamber 9.

[0047] Heating circuit: Each circuit consists of a nickel-chromium alloy resistance wire 6 (0.45 mm in diameter, resistance approximately 25 Ω), an insulating sleeve 7 (temperature resistance ≥300℃, diameter 1 mm), and an insulation layer 8 (ceramic fiber material). The insulating sleeve 7 is a glass fiber sleeve. One resistance wire 6 is tightly wound around the outer wall of the cesium crucible 4, forming the "crucible heating section"; the other is wound around the outer wall of the stainless steel pipe 2 at a density of 4-6 turns per centimeter, forming the "pipe heating section". The insulating sleeve 7 is first placed over the resistance wire 6 for insulation protection, and then wrapped and fixed with the insulation layer 8 at a density of 8-12 layers per turn, providing insulation. The insulation layer 8 is made of high-temperature resistant glass fiber tape.

[0048] Temperature Measurement and Control: K-type thermocouples 5 are attached tightly to the outer walls of the crucible and pipes for real-time temperature monitoring. The signal lines of the two thermocouples 5 and the power lines of the two resistance wires 6 are all connected to the constant temperature control heating chamber 9. The constant temperature control heating chamber 9 adopts a PID closed-loop control algorithm, which can independently and accurately control the temperature of the two heating sections, with a temperature control accuracy of ±1℃.

[0049] 2. Assembly and Sealing Inspection Procedures

[0050] (1) Cesium filling and primary sealing: In a vacuum glove box filled with inert gas (such as argon), open the CF16 blind flange 3 and precisely fill a clean, dry stainless steel cesium crucible 4 with a measured amount (such as 12-13 g) of high-purity liquid cesium metal. After filling, carefully place the oxygen-free copper sealing ring, install and tighten the CF16 blind flange 3 to complete the primary sealing of the cesium storage unit.

[0051] (2) System Assembly: Remove the cesium storage evaporation module, which has undergone primary sealing, from the glove box. According to... Figure 1 The structure shown is connected in sequence as follows: CF16 blind flange 3 of cesium crucible 4, first sealing valve, intermediate connecting pipe 2, second sealing valve, main transmission pipe 2, and cesium feed nozzle 10. All metal sealing surfaces (such as CF flanges) must be clean, and all ferrule connections must be tightened as required.

[0052] (3) Vacuum sealing verification: A high-sensitivity helium mass spectrometer leak detector was used to check for leaks in all sealing parts of the device, with a focus on the sealing surface of the CF16 blind flange 3, the bellows sealing valve 1 itself, and its ferrule connection. The overall static leak rate was required to be less than 1×10⁻⁶. -10 Pa·m 3 / s, ensuring that the requirements of the high vacuum system are met.

[0053] 3. Device usage methods and operating procedures

[0054] (1) System evacuation and preparation: Install the assembled device onto the corresponding interface of the fusion device vacuum chamber 11 through the cesium feed nozzle 10. First, keep both the first and second sealing valves closed. Start the molecular pump group connected to the fusion device to evacuate the main vacuum chamber to achieve a basic vacuum (e.g., 10⁻⁻⁴). 5 (Pa level). Then, slowly open the second sealing valve to connect the piping section inside the device to the main vacuum chamber and evacuate it to the same vacuum level. Finally, slowly open the first sealing valve again to evacuate the entire feed device, including the cesium crucible 4, until the entire system reaches the vacuum level required for operation.

[0055] (2) Segmented heating and temperature gradient establishment: The target temperature is set by the constant temperature control heating chamber 9. To achieve directional diffusion of cesium vapor, the set temperature of the pipe heating section should always be higher than that of the crucible heating section. The typical set values ​​in this embodiment are: 200-220℃ for the pipe heating section and 160-180℃ for the crucible heating section. Set the heating rate (e.g., 5℃ / min) and start the heating program. The PID control system will automatically adjust the heating power according to the feedback from the thermocouple 5, so that the two temperatures can quickly and stably reach the set values, and form a stable temperature gradient field from the crucible to the nozzle.

[0056] (3) Cesium vapor feeding and rate regulation: Once the temperatures of the two sections stabilize at the set values, cesium vapor can be fed in. By fine-tuning the heating power of the crucible heating section through the constant temperature control heating box 9, the evaporation rate of liquid cesium can be precisely controlled. This device can achieve continuous and stable evaporation rate regulation within the range of 0.1 mg / h to 5 mg / h. After cesium vapor is generated in the crucible 4, under the maintenance of the higher temperature in the pipeline and the drive of the temperature gradient, it diffuses directionally along the transmission pipeline 2 towards the low-temperature (relative) vacuum chamber, and finally is stably and uniformly sprayed onto the electrode surface through the nozzle 10.

[0057] (4) Operation monitoring and maintenance: During the long-term operation of the device, the constant temperature control heating box 9 continuously monitors and maintains a stable temperature. The consumption of cesium can be estimated by accumulating the evaporation rate and the operating time. When it is necessary to confirm the remaining amount or replenish cesium, the advantages of the dual-valve structure can be utilized: first, the first and second sealing valves are closed simultaneously to isolate the cesium crucible 4 from the vacuum system; then, the connecting pipe between the two valves is disassembled, and the module containing the crucible 4 is moved to the glove box for offline inspection or replenishment. This process does not affect the integrity of the main vacuum system of the fusion device at all, realizing "non-stop maintenance".

[0058] (5) Shutdown Procedure: At the end of the experiment or operating cycle, follow these steps to shut down the system: First, close the second sealing valve near the ion source to cut off the path of cesium vapor into the vacuum chamber. Then, gradually reduce and finally shut off the power of the two heating sections using the constant temperature control heating chamber 9, allowing the device to cool naturally to room temperature (e.g., 25°C). After the temperature has completely cooled down, close the first sealing valve. Finally, perform subsequent vacuum venting and other operations as required by the system.

[0059] By operating the device according to the specific implementation method described above, and through testing and verification, the vacuum level of the system was stably maintained at 10 during operation. -5 Above Pa, there is no leakage. Temperature control is precise, with fluctuations within ±1℃, effectively preventing cesium condensation in the pipeline. Cesium vapor feed is continuous, stable, and precisely controllable, and the negative ion beam yield is significantly improved (by more than 35%) compared to traditional single-valve, overall heating feed devices.

[0060] The dual-valve design greatly improves operational safety and maintenance convenience, avoiding vacuum breakage in the main system due to maintenance operations, making it particularly suitable for fusion devices that operate with long pulses or quasi-continuous operation.

[0061] Example 2: Based on Example 1, this example configures a negative ion source system with multiple feed points. For example... Figure 2 and Figure 3 As shown, two independent feed devices are installed above and below the vacuum chamber 11 of the fusion device. The two devices have identical structures, but their spatial arrangement and the length of the connecting pipes 2 are adjusted according to the actual installation space. Pipes 2 include pipe 201 (upper part of the negative ion beam source for liquid cesium heating and evaporation feed) and pipe 202 (lower part of the negative ion beam source for liquid cesium heating and evaporation feed). Pipe 201 is bent at an acute angle to ensure that the opening of the crucible 4 is slightly upward, allowing cesium vapor to evaporate through heating. The two devices share or use a constant-temperature controlled heating chamber 9, allowing for independent setting of temperature and evaporation rate. This enables independent optimization and control of cesium coverage in different electrode areas, further improving the overall performance and uniformity of the negative ion beam.

[0062] In summary, this invention provides a highly stable, safe, and easy-to-maintain solution for feeding liquid cesium metal through a collaborative design that incorporates dual-valve vacuum isolation, segmented independent and precise temperature control to create a temperature gradient, and high-smoothness pipeline transport. Those skilled in the art can adaptively adjust parameters such as crucible volume, pipeline dimensions, heating power, and temperature setpoint according to actual application scenarios. These adjustments and modifications based on the core concept of this invention should all be included within the scope of protection of the appended claims.

[0063] Example 3: This example provides a method for using a liquid metal cesium heating and evaporation feeding device suitable for a negative ion beam source, as described in Example 1, including the following steps:

[0064] The crucible 4 containing liquid cesium metal and the transmission pipe 2 for transmitting cesium vapor are independently heated and controlled; by adjusting the heating power of the crucible 4, the evaporation rate of cesium is controlled within the range of 0.1-5 mg / h.

[0065] The heating temperature of the transmission pipe 2 is controlled to be higher than that of the crucible 4. Before applying heat to the transmission pipe 2 and the crucible 4, the feeding device containing the crucible 4 and the transmission pipe 2 is evacuated to achieve and maintain a high vacuum state, so as to form a temperature gradient in the transmission pipe 2 that drives the cesium vapor to diffuse from the crucible 4 to the cesium vapor feed nozzle 10.

[0066] The cesium vapor generated by the heating and evaporation of liquid cesium metal in the crucible 4 moves directionally along the transmission pipe 2 under the influence of the temperature gradient and is ejected through the cesium vapor feed nozzle 10. When it is necessary to replenish the liquid cesium metal in the crucible 4 or to perform maintenance on the crucible 4, the first vacuum valve and the second vacuum valve provided on the transmission pipe 2 are closed, and the connection between the first vacuum valve and the second vacuum valve is disconnected, so as to perform offline operation on the crucible 4 without damaging the downstream vacuum system.

[0067] The above specific embodiments are merely several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant teachings of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A device and method for feeding liquid cesium through heating and evaporation into a negative ion beam source, characterized in that, include: A liquid cesium metal storage and evaporation unit includes a crucible (4) for containing liquid cesium metal. The cesium vapor transmission unit includes a transmission pipe (2) connected to the outlet of the crucible (4), and a cesium vapor feed nozzle (10) is installed at the end of the transmission pipe (2). The heating and temperature control unit includes a first heating component, a second heating component, and a constant temperature control heating box (9); The first heating component is used to independently heat the crucible (4), and the second heating component is used to independently heat the transmission pipe (2); The constant temperature control heating box (9) is used to independently control the heating power of the first heating component and the second heating component, so that the temperature of the transmission pipe (2) is higher than the temperature of the crucible (4), so as to form a temperature gradient in the transmission pipe (2) that drives the cesium vapor to diffuse into the cesium vapor feed nozzle (10).

2. The liquid cesium heating and evaporation feeding device for a negative ion beam source according to claim 1, characterized in that, It also includes a vacuum isolation unit, which includes a first vacuum valve and a second vacuum valve arranged in series on the cesium vapor transmission path; wherein the first vacuum valve is located near the crucible (4) and the second vacuum valve is located near the cesium vapor feed nozzle (10); the first vacuum valve and the second vacuum valve are detachably connected.

3. The liquid cesium heating and evaporation feeding device for a negative ion beam source according to claim 2, characterized in that, Both the first vacuum valve and the second vacuum valve are bellows-sealed valves, and the leakage rate of the bellows-sealed valve is no higher than 1×10⁻⁶. -10 Pa·m 3 / s.

4. The liquid cesium heating and evaporation feeding device for a negative ion beam source according to claim 1, characterized in that, The crucible (4) is sealed to the end of the transmission pipe (2) through a CF16 blind plate (3), and the CF16 blind plate (3) and the crucible (4) are sealed by an oxygen-free copper sealing ring.

5. The liquid cesium heating and evaporation feeding device for a negative ion beam source according to claim 1, characterized in that, The first heating component and the second heating component both include a resistance wire (6) wound around the outside of the corresponding heated component, an insulating sleeve (7) fitted over the resistance wire (6), and an outermost heat insulation layer (8). The insulating sleeve (7) is an insulating sleeve with a temperature resistance of not less than 300°C; the heat insulation layer (8) is a heat insulation layer.

6. The liquid cesium heating and evaporation feeding device for a negative ion beam source according to claim 1, characterized in that, The constant temperature control heating box (9) controls the heating temperature of the transmission pipe (2) to 200-240℃ and controls the heating temperature of the crucible (4) to 150-190℃.

7. A method for feeding liquid cesium through heating and evaporation into a negative ion beam source, applied to the liquid cesium heating and evaporation feeding device for a negative ion beam source as described in any one of claims 1-6, characterized in that, Includes the following steps: Independent heating control is applied to the crucible (4) containing liquid cesium metal and the transmission pipe (2) used to transmit cesium vapor; The heating temperature of the transmission pipe (2) is controlled to be higher than that of the crucible (4) so ​​as to form a temperature gradient in the transmission pipe (2) that drives the cesium vapor to diffuse from the crucible (4) to the cesium vapor feed nozzle (10); The cesium vapor generated by heating and evaporating the liquid cesium metal in the crucible (4) moves directionally along the transmission pipe (2) under the action of the temperature gradient and is ejected through the cesium vapor feed nozzle (10).

8. The method for feeding liquid cesium through heating and evaporation into a negative ion beam source according to claim 7, characterized in that, By adjusting the heating power of the crucible (4), the evaporation rate of cesium is controlled within the range of 0.1-5 mg / h.

9. A method for feeding liquid cesium by heating and evaporation into a negative ion beam source according to claim 7, characterized in that, Before heating is applied to the transfer pipe (2) and the crucible (4), the feed device containing the crucible (4) and the transfer pipe (2) is evacuated to achieve and maintain a high vacuum state.

10. A method for feeding liquid cesium by heating and evaporation into a negative ion beam source according to claim 7, characterized in that, When it is necessary to replenish the liquid cesium metal in the crucible (4) or to maintain the crucible (4), the first vacuum valve and the second vacuum valve installed on the transmission pipeline (2) are closed, and the connection between the first vacuum valve and the second vacuum valve is disconnected, so as to perform offline operation on the crucible (4) without damaging the downstream vacuum system.

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