In-situ metal deposition in tokamaks

Abstract

A method for repairing a surface of a divertor or first wall in a tokamak plasma vessel is disclosed. The surface of the divertor or first wall has a melting point of at least 2000. o C. A pressure of less than 25 mbar is maintained within the plasma vessel after operation of the plasma vessel is terminated. The refractory metal is deposited on a surface of a divertor or first wall within the plasma vessel via a deposition process selected from the group consisting of additive manufacturing, physical vapor deposition, thermal spraying, arc ion plating, diode laser cladding, and chemical vapor deposition.

Description

Technical Field

[0001] The present invention relates to a tokamak plasma vessel. In particular, the present invention relates to a method and apparatus for depositing a refractory metal on the divertor and first wall of a tokamak.

Background Art

[0002] A divertor is a device within a tokamak plasma vessel that enables the removal of waste materials and power from the plasma while the tokamak is operating. Waste materials naturally occur when particles diffuse from the magnetically confined plasma core. The waste particles are a combination of fuel (deuterium and tritium), fusion products (helium ash), and heavier ions released from the walls. To confine the plasma, a tokamak utilizes a magnetic field. However, the particles diffuse slowly and randomly and eventually collide with one of the multiple divertor surfaces configured to withstand high fluxes of ions.

[0003] Figure 1 shows a poloidal cross-section through one side of a typical tokamak. The tokamak 100 contains a toroidal plasma vessel 101. Poloidal field coils generate a poloidal magnetic field that confines the plasma (carrying the electric current). If there are no collisions between plasma particles, turbulence, waves or other such phenomena, the plasma (made of charged particles) is substantially bound to magnetic field lines (which can be represented as lines of constant poloidal flux 113). The plasma is said to be confined on lines of constant poloidal flux within a “plasma core.” This is because lines of constant flux are closed, and this is called a so-called “closed flux surface.” Through collisions and other such processes, the plasma slowly diffuses from the plasma core. A “final closed flux surface” 111, having a null point 112 at one end (usually the lower end), defines the edge of the confined core. The magnetic flux lines 114 immediately outside the plasma core ("scrape-off layer") intersect with two surfaces: an external (i.e., radially outward) divertor surface 121 (located at the bottom of the channel in the lower part of the plasma vessel in this example) below the null, and an internal (i.e., radially inward) divertor surface 122. Waste particles and power are deposited on these surfaces, with the majority of the waste particles and power being transferred to the external divertor surface (the precise separation of internal and external surfaces depends on the turbulent physics within the scrape-off layer).

[0004] Figure 2 shows a cross-section through a second typical tokamak. This tokamak has a “double null” divertor. The principle of the “double null” divertor is the same as that of the “single null” divertor in Figure 1, except that the null and the corresponding divertor surfaces 221, 222, 223, and 224 are located on both the upper and lower edges of the plasma core 210. The advantage of the double null configuration is that the heat flux on each divertor surface is approximately half the heat flux received by the single null configuration.

[0005] Figure 3 shows a more complete diagram of a tokamak in a double null divertor configuration. The drawing is symmetrical both horizontally and vertically, and for clarity, reference numbers are not duplicated for symmetrical components. Figure 3 is a cross-section taken from a vertical plane across the center of the tokamak, showing the plasma chamber wall 300 and its components. The tokamak comprises several poloidal and toroidal magnetic field coils 301 and toroidal magnetic field coils (not shown) for controlling the plasma. Each divertor assembly 310 comprises a divertor surface 311 located where the plasma collides with the divertor, and a baffle 312. The baffle 312 serves to shape the plasma and protect components located behind the baffle.

[0006] The divertor surface is subjected to high thermal loads and significant erosion. Therefore, it must be made of a material that can withstand high temperatures and is resistant to such erosion, or a metal with a low atomic number such as beryllium or lithium, so that no erosion contaminates the plasma. Furthermore, to reduce the possibility of tritium accumulation within the divertor, it is preferable that the divertor surface be made of metal. For this reason, suitable materials for the divertor surface include refractory metals, lithium, and beryllium.

[0007] Refractory metals have a melting point of 2,000°C. ° These are metallic elements with a carbon content greater than 150, including niobium, molybdenum, tantalum, tungsten, and rhenium. They are also highly resistant to wear caused by plasma erosion, etc. However, even when these metals are used as divertor surfaces, wear still occurs, and divertors need to be replaced or repaired periodically. Replacing or repairing a divertor requires stopping the fusion path and repressurizing the plasma vessel, which necessitates considerable downtime as the chamber must be returned to a vacuum before the plasma vessel can resume operation. This requires a lengthy degassing process to remove residual gases adsorbed on the chamber walls.

[0008] Similar considerations apply to the "first wall" of the plasma vessel, i.e., the portion of the inner chamber wall that directly faces the plasma, such as the cover over the coils within the plasma chamber. This too is damaged by heat and abrasion caused by interaction with the plasma and needs to be repaired periodically to mitigate damage from these instabilities. [Overview of the project]

[0009] According to a first aspect of the present invention, a method is provided for repairing the surface of a divertor or first wall in a tokamak plasma vessel. The surface of the divertor or first wall has a melting point of at least 2000 ℃ It contains a refractory metal. After the operation of the plasma container is completed, the pressure inside the plasma container is set to 25 00Pa Maintain below. Deposit a refractory metal onto the surface of the diverter or first wall within the plasma vessel via one of the following deposition processes: additive manufacturing, physical vapor deposition, thermal spraying, arc ion plating, diode laser cladding, and chemical vapor deposition.

[0010] A second aspect of the present invention provides a method for operating a tokamak plasma vessel. A first plasma is formed and maintained within the plasma vessel. The first plasma is extinguished. The divertor or first wall of the plasma vessel is repaired in accordance with the first aspect. A second plasma is formed within the plasma vessel. The pressure within the plasma vessel is 25 from the time the first plasma is extinguished until the second plasma is formed. 00Pa It remains below that value.

[0011] In a further embodiment, a tokamak plasma vessel is provided. The tokamak plasma vessel comprises a vacuum chamber, a vacuum maintenance system, a first wall, a diverter, and a refractory metal deposition system. The vacuum maintenance system maintains the internal pressure at 25 00Pa It is configured to maintain a melting point of less than 2000. The first wall and divertor have a melting point of 2000 ℃ Each surface has a refractory metal content exceeding a certain amount. The refractory metal deposition system varies among further embodiments.

[0012] In a third embodiment, the refractory metal deposition system comprises a refractory metal source, a heating system, a positioning system, and a controller. The heating system is configured to heat a portion of the refractory metal from the refractory metal source. The positioning system is configured to position the refractory metal and heat source of the refractory metal source in any area of ​​the surface of the first wall or diverter. The controller is configured to cause the heating system to heat a portion of the refractory metal from the refractory metal source, to cause the positioning system and / or the refractory metal source to deposit a portion of the refractory metal onto a target area, and to melt a portion of the refractory metal on the target area.

[0013] In a fourth embodiment, the refractory metal deposition system comprises a refractory metal source, a positioning system, and a controller. The refractory metal source comprises a refractory metal, a vaporization system configured to vaporize the refractory metal, and a discharge port. The positioning system is configured to position the discharge port of the refractory metal source so that the vaporized refractory metal is directed to any area on the surface of the first wall or diverter. The controller is configured to position the discharge port by the positioning system so that, when vaporized, the refractory metal is directed to a target area on the surface of the first wall or diverter, and to vaporize a portion of the refractory metal by the refractory metal source, thereby coating the target area with the refractory metal.

[0014] In a fifth embodiment, the refractory metal deposition system comprises a refractory metal source, a heater, a spray unit, and a controller. The controller is configured to cause the refractory metal source to supply the heater with refractory metal, and the spray unit to spray heated particles of the refractory metal from the heater onto the surface of the diverter and / or the first wall.

[0015] In a sixth embodiment, the refractory metal deposition system comprises a refractory metal source, an electrode, and a voltage source. The electrode is configured to generate an arc between the electrode and the refractory metal source. The voltage source is configured to supply a voltage to the divertor and / or first wall such that the divertor and / or first wall acquires a charge opposite to the charge of the plasma caused by the arc.

[0016] In a seventh embodiment, the refractory metal deposition system comprises a refractory metal source, a heating system, a positioning system, and a controller. The heating system is configured to heat a target area on the surface of the first wall or diverter. The positioning system is configured to position the refractory metal and heat source of the refractory metal source in any area on the surface of the first wall or diverter. The controller causes the heating system to heat the target area on the surface of the diverter or first wall so that the surface melts at the target area. The positioning system and / or refractory metal source are configured to bring a portion of the refractory metal into contact with the target area so that a portion of the refractory metal is melted on the target area.

[0017] In an eighth embodiment, the refractory metal deposition system comprises a chemical reactant supply system and a heater. The chemical reactant supply system is configured to supply one or more reagents to the chamber in gaseous or plasma form through a port, the reagents reacting to form the refractory metal and gaseous byproducts. The heater is configured to heat the surface of the diverter or first wall to a temperature sufficient to react the reagents to form the refractory metal. The vacuum maintenance system is configured to remove the gaseous byproducts and excess reagents from the chamber after the deposition of the refractory metal.

[0018] Further embodiments are described in claim 2 and subsequent claims. [Brief explanation of the drawing]

[0019] [Figure 1]It is a schematic diagram of a tokamak with a single null divertor. [Figure 2] It is a schematic diagram of a tokamak with a double null divertor. [Figure 3] It is a cross-sectional view of a tokamak with a double null divertor, showing additional components. [Figure 4] It is a schematic diagram of a typical tokamak. [Figure 5] It is a flowchart of a method for repairing the surface of a divertor or a first wall. [Figure 6] It is a schematic diagram of a tokamak plasma vessel. [Figure 7] It is a schematic diagram of a typical refractory metal deposition system.

Embodiments for Carrying Out the Invention

[0020] In order to enable repair without the need to repressurize the plasma vessel, a system and method for regenerating the divertor or the first wall of a tokamak plasma vessel on-site are proposed below. The proposed solution includes providing these inside the plasma vessel so that a vacuum is maintained, using a vacuum deposition technique suitable for use with refractory metals. This reduces the downtime of the plasma vessel during such repairs. That is, instead of long repressurization, depressurization, and degassing procedures, the plasma operation can be temporarily stopped while under vacuum, and after the repair is completed, the chamber can be reused almost immediately (there is a step of removing by-products of the deposition process if necessary).

[0021] Figure 4 shows a schematic diagram of an exemplary plasma vessel. The plasma vessel 400 comprises a first wall 401, a diverter surface 402, a port 403, and refractory metal deposition systems 404a, b, c, d. During the operation of the plasma vessel, wear occurs on the diverter and the first wall. To repair this wear, the plasma vessel is stopped but kept under vacuum, and refractory metal is deposited on the diverter 402 and / or the first wall 301 using the refractory metal deposition systems 404a, b, c, d. Depending on the deposition technique used, the refractory metal deposition system may include components that are always located in the fusion path (e.g., electrodes 404a), components incorporated into the diverter and / or the first wall (e.g., heaters 404b), components present in an insertable arm via the port (e.g., refractory metal source 404c), and / or components located within a protected area of ​​the chamber (e.g., spray system 404d).

[0022] Generally, components of a refractory metal deposition system may be contained within the fusion path if they are in a protected area (i.e., the tokamak region where the plasma cannot reach) or do not protrude into the chamber to the extent that they interfere with the plasma, and can be made sufficiently refractory and abrasion resistant to withstand the conditions inside the chamber. Otherwise, components that require access to the chamber itself during deposition may be provided so that they can be introduced through a port using a "load lock" or similar means to maintain the vacuum in the chamber.

[0023] Next, we will describe several exemplary deposition systems using various deposition techniques. However, it should be noted that any deposition technique may be used if it is suitable for applying a refractory metal to a surface containing that metal and is capable of operating in a vacuum. In the standard literature, many deposition techniques include a first step of providing a vacuum, a step of removing moisture from the components, or a similar degassing procedure. These steps are generally unnecessary since the plasma vessel is already under vacuum and degassed. Some techniques include a step of etching the components to remove surface oxides, usually by ion bombardment. Again, this may be unnecessary since the divertor and first wall have already been effectively etched by the plasma (and indeed, this "etching" is wear that needs to be repaired).

[0024] The first example presented is arc ion plating. Arc ion plating is performed on a clean surface under vacuum. In other applications, this is cleaned by heating to remove moisture and then ion etching to remove impurities from the surface. However, when used in a tokamak, these steps are optional, as there is no moisture on the surface and the plasma effectively acts as an ion etcher. An arc discharge is formed between the refractory metal source and ground to vaporize the refractory metal into a positively charged plasma. When a negative voltage is applied to the target surface (i.e., the divertor or first wall region that requires repair), ions of the refractory metal are attracted, thereby depositing them on the surface. Alternatively, the plasma may be negatively charged and the target positively charged.

[0025] For in-situ use in a tokamak, arc ion plating may be implemented by providing a refractory metal source (e.g., tungsten) either inside the chamber or in the port, electrodes configured to generate an arc in the metal source to produce a charged plasma, a diverter, and / or a device configured to supply voltage to the first wall. When arc ion plating is used to repair the first wall, the voltage may be applied locally only to specific areas of the first wall, such as target areas where significant wear has occurred or is expected.

[0026] The second example presented is chemical vapor deposition (CVD). Chemical vapor deposition is a coating process that uses a thermally induced chemical reaction on the surface of a heated target, with the reagent supplied as a gas. For example, tungsten may be deposited via the reaction WF6 + 3H2 = W + HF. The reaction takes place on the heated target (i.e., a divertor, first wall, or selected first wall section), and the reaction byproduct is a gas that can be removed from the chamber by returning to a vacuum.

[0027] Chemical vapor deposition provides a heating element within the diverter and / or first wall, bringing the target region to the temperature required for CVD (typically 600°C). ° From C to 1100 ° It may be implemented as a tokamak by heating (between C) and introducing the reagent into the plasma vessel through a port. Once the reaction is complete, the remaining reagent or gaseous byproduct can be pumped out of the plasma vessel.

[0028] A variation of CVD is plasma-assisted CVD (PACVD), which accelerates the reaction by using electrical discharge to plasmaize the reagents. While the coating rate of PACVD is generally lower than that of conventional CVD, this is partially offset by the lower pressure of the reactants required in the tokamak, and the pumping required to restore the vacuum is reduced.

[0029] As a third example, the deposition method used may be thermal spraying. In thermal spraying, a large number of small particles of softened or molten refractory metal are projected onto a target surface, where they flatten and adhere, providing a uniform coating. Thermal spraying typically involves a material source through which the material is sprayed to a diverter after passing through a heat source to achieve the required temperature. When implementing a vacuum environment, the heat source is often plasma.

[0030] Thermal spraying may be implemented in a tokamak by providing the device to the tokamak via a port, without requiring any modifications to the inside of the plasma vessel.

[0031] As a fourth example, additive manufacturing technology may be used. When such technology is applied to refractory metals, the spot to which the metal is to be applied is heated using a heat source (e.g., a laser or electron beam), and then the refractory metal is applied, for example, by spraying powdered refractory metal onto the spot or by bringing the end of a refractory metal wire into contact with the spot. Further heat is applied to the applied refractory metal, causing it to melt onto the target spot as a small weld. This is repeated over the area to be covered to the desired depth. Optionally, the step of heating the target spot may be omitted, and only the refractory metal to be applied is heated.

[0032] The resolution of additive manufacturing techniques for refractory metals can be low. That is, the minimum spot size for applying the refractory metal may be too large, making it impossible to accurately fill defects or achieve an acceptable surface finish. Therefore, additive manufacturing may continue slightly beyond the required thickness and area, with the excess being milled or removed.

[0033] Within the tokamak, additive manufacturing may be implemented by providing a robot (and optionally a milling or other refractory metal removal device) equipped with a heat source and a refractory metal source, which can enter through a port and be moved to the location where repair is needed. Additive manufacturing can be performed at any level of vacuum.

[0034] The fifth example is physical vapor deposition (PVD). In PVD, first, the refractory metal to be deposited is suspended in a gas phase, and then deposited or condensed on a surface. The metal is vaporized into a gas phase in an "evaporation cell" by, for example, sputtering, vaporization with a heater such as a resistance heater, electron beam heating, vacuum arc heating, or other suitable technique. The vapor is allowed to escape from an opening in the evaporation cell, and the opening is shaped and positioned so that the vapor is directed towards the target surface. Because this is a "line of sight" deposition process, anything within the cone of vapor will have the refractory metal deposited on it, and if there are steps or bumps on the target, a shadow effect will occur.

[0035] Inside the tokamak, the vapor cell may enter through a port in the arm so as to be directed towards the target site. Alternatively, the vapor cell may remain stationary, and the vapor flow may be directed towards the target site using an exhaust hose in the arm. PVD is, for example, 10 -4 P a. This may be carried out under a strong vacuum as follows:

[0036] Many of the above deposition techniques may be applied to specific regions of the tokamak. This has the advantage of identifying areas that require repair and regeneration. Early detection of the need for regeneration may be performed by monitoring the plasma (e.g., to identify impacts against the first wall), monitoring the temperature of the first wall elements (e.g., to identify areas that are likely to be partially melted or sublimated), or other similar monitoring. During the regeneration process, before applying refractory metal by one of the above techniques, a more detailed scanning method may be used to determine the extent of damage to the first wall and / or the necessary repairs. This may include optical scanning, cameras such as depth mapping cameras, LIDAR imaging, or other depth sensing for mapping the damaged surface, which may generate a 3D model of the surface or a 2D image from which the damage can be determined. The results of this scan can then be used by a controller of the deposition process to control deposition so that it is concentrated on the areas that require repair and limits the additional deposition of material outside those areas. The apparatus for such scanning may be inserted into the tokamak via a robotic arm or similar positioning means, which may be the same positioning means used to position the apparatus implementing the above deposition techniques.

[0037] Some of the above techniques generate powder, milling debris, or similar material within the tokamak after repair. The deposition apparatus may include a debris removal system to collect the powder or debris left over by the deposition process and / or subsequent milling. This may be implemented by a vacuum pump, as the debris flows into the pump as residual gas (or any gas added during deposition) in the chamber moves when the pump is in operation. Since primary vacuum pumps for tokamaks are generally not resilient enough to withstand a considerable amount of powder or milling debris, secondary vacuum pumps (or pumps) of a type that can withstand the entry of debris into the pump may be provided, such as scroll pumps. To assist this, a small amount of gas may be added to the chamber while maintaining the pressure below a desired threshold.

[0038] If the above techniques require introducing powder into the chamber, this may be done by flowing the powder into the chamber with a stream of an inert gas such as argon. This will result in a partial loss of vacuum, but it will still be possible to maintain a pressure considerably lower than atmospheric pressure. As mentioned earlier, pumping the inert gas has the additional benefit of helping to remove powder or other debris from within the chamber.

[0039] Masking may be used to provide further precision to the above techniques. This may be done by applying a removable mask around the target area, which is removed after deposition. Alternatively, it may be done by providing a mask as part of a deposition apparatus that limits the area on which the refractory metal is deposited.

[0040] Generally, masking and / or milling to limit the area or improve surface smoothness is not essential. The deposition techniques described above result in layer thicknesses on the order of microns to millimeters, and this additional thickness does not significantly affect the first wall. Milling to improve surface smoothness generally offers a slight advantage in that a smoother surface is less and / or more predictable to erosion by plasma impacts. Masking or milling to prevent deposition outside the area requiring repair offers a slight advantage in that the result is a more uniform first wall that is more predictably eroded and conducts heat (i.e., no unintended hot spots). However, these effects are small, and a balance must be struck between the additional complexity of masking and milling and the need to remove debris from milling.

[0041] As the above examples show, there are various deposition techniques that can be used to regenerate the divertor and / or first wall of a tokamak plasma vessel. Again, it should be noted that there are many more techniques than those shown in the above examples, and deposition techniques that can be achieved in a vacuum using refractory metals can offer the general advantages obtained by depositing metal in situ on the divertor and / or first wall. In addition to the general advantage of not having to repressurize the chamber and re-establish a vacuum from atmospheric pressure, individual techniques have advantages over others.

[0042] For example, among the techniques described above, arc ion plating and CVD do not require a line of sight between the material source and the target (i.e., the divertor or first wall). In arc ion plating and thermal spraying, only the minimum amount of material that needs to be pumped out before restarting operation (compared to the reaction byproducts left by CVD and other techniques) remains in the chamber. Thermal spraying does not require any specific modifications to the divertor or first wall itself; that is, it does not require heating or supplying charge to the target area, and can therefore be easily incorporated independently of other design considerations of the plasma vessel.

[0043] If heating of the target (i.e., the diverter or first wall) is required during deposition, this may be provided by a resistance heating element incorporated inside or behind the target, or by passing an electric current directly through the target. Alternatively, this may be achieved by pumping a hot gas through the coolant channels of the diverter or first wall to reach the required temperature. This is generally not necessary for deposition methods where heating before deposition is required to remove moisture.

[0044] If the target requires an electric charge, an electrical component may be incorporated into the target to provide such a charge.

[0045] To clean the target before deposition, an etching system, such as an ion etching system, may be used. This is optional, and even in deposition methods that typically require such etching, the target is likely to be cleaned by the action of plasma on it. Additionally, the target may be heated before degassing any hydrogen absorbed into the divertor plate or first wall.

[0046] Where the term "vacuum" is used above, it should be understood that a perfect vacuum is not actually achievable. In some scenarios, the internal pressure of the plasma vessel is within an order of magnitude of the pressure obtained after the plasma has cooled, for example, 2 to 7 x 10⁻¹⁰ -6 P It may be maintained between a. As another example, the internal pressure of the plasma vessel may be maintained at a moderate vacuum, i.e., less than 2500 Pa. As yet another example, the internal pressure of the plasma vessel may be maintained at a high vacuum, i.e., such that the mean free path of particles in the plasma vessel is smaller than the radius of the plasma vessel. Although these represent very different grades of vacuum, it will be understood that even maintaining the vessel below a moderate vacuum is a considerable improvement over the current method, which requires returning the vessel to atmospheric pressure to remove the divertor or first wall section.

[0047] The above refers to a tokamak plasma vessel, which is used specifically in tokamak fusion reactors. It should be noted that wear on the divertor and first wall is significantly greater compared to colder plasmas, and there may be a greater need to avoid downtime (to enable efficient experiment execution and ultimately economical power generation).

[0048] The apparatus implementing the above method may be controlled by a controller, which may be implemented as software running on one or more processors. The controller may be integrated into the hardware of the plasma vessel, or it may be implemented as software running on a remote computer that can access the functions of the plasma vessel and the deposition apparatus. The controller may be implemented as distributed software running on multiple computers.

[0049] Figure 5 is a flowchart of a method for repairing the surface of the divertor or first wall in a tokamak plasma vessel, wherein the surface of the divertor or first wall has a melting point of at least 2000 ℃ It is equipped with fire-resistant metal. In step S501, after the operation of the plasma vessel is completed, the pressure inside the plasma vessel is set to 25 00Pa Maintain below. In step S502, a refractory metal is deposited on the surface of the diverter or first wall within the plasma vessel via one of the following deposition processes: additive manufacturing, physical vapor deposition, thermal spraying, arc ion plating, diode laser cladding, and chemical vapor deposition.

[0050] Figure 6 is a schematic diagram of the tokamak plasma vessel. The tokamak plasma vessel consists of a vacuum chamber 601 and a pressure of 25 in the vacuum chamber. 00Pa A vacuum maintenance system 602 configured to maintain a melting point below 2000 ℃ The system comprises a first wall 603 and a diverter 604, each having a surface made of a refractory metal exceeding a certain value, and a refractory metal deposition system 605, such as the one described in the example above.

[0051] In this example, the refractory metal deposition system is located at port 606 so that its components can enter the vacuum chamber through the port.

[0052] Figure 7 is a schematic diagram of an exemplary refractory metal deposition system configured for additive manufacturing in the above example. The refractory metal deposition system 700 includes a refractory metal source 701, a heating system 702 configured to heat a portion of the refractory metal of the refractory metal source, such as an electron gun or laser, and a robotic arm, for example, on any area of ​​the surface of the first wall or diverter. Heat source and Refractory metal source and The system includes a positioning system 703 configured to position the diverter, and a controller 704 configured to cause a heating system to heat a portion of the refractory metal from a refractory metal source, causing the positioning system and / or the refractory metal source to deposit a portion of the refractory metal onto a target area on the surface of the diverter or first wall, and to melt a portion of the refractory metal onto the target area.

Claims

1. A method for repairing the surface of a diverter or first wall in a tokamak, The aforementioned tokamak, Vacuum chamber and A vacuum maintenance system configured to maintain the pressure inside the vacuum chamber at less than 2500 Pa, A first wall and a diverter, each having a surface containing a refractory metal with a melting point exceeding 2000°C, A refractory metal deposition system comprising a refractory metal source, a heating system, and a positioning system. It is equipped with, The aforementioned method, The vacuum maintenance system maintains the pressure inside the vacuum chamber below 2500 Pa after the tokamak has finished operating. A step of depositing the refractory metal onto the surface of the diverter or the first wall via a deposition process, The positioning system is used to position the heating system and a portion of the refractory metal of the refractory metal source at a target location on the surface of the first wall or diverter. The heating system heats a portion of the refractory metal in the refractory metal source, causing that portion of the refractory metal to melt on the target area. Steps including and Methods that include...

2. The method according to claim 1, wherein the deposition process includes heating the target site with the heating system.

3. The method according to claim 1, comprising the step of coating a region with the refractory metal by performing the step of depositing the refractory metal onto each of a plurality of target regions within a region of the surface of the first wall.

4. The method according to any one of claims 1 to 3, wherein the refractory metal is provided as a powder, the portion of the refractory metal is a portion of the powder, and the refractory metal source includes a powder dispenser configured to distribute the portion of the refractory metal.

5. The method according to claim 4, wherein the powder dispenser is equipped with an inert gas source, and the powder dispenser distributes the refractory metal powder by blowing the refractory metal powder from a refractory metal powder source onto the target area via an output channel.

6. The aforementioned refractory metal source includes a refractory metal wire. The method according to any one of claims 1 to 3, wherein the part of the refractory metal source is one end of the refractory metal wire.

7. The method according to any one of claims 1 to 3, wherein the step of heating the target portion and / or the portion of the refractory metal includes heating using a laser or electron beam heating.

8. The step includes scanning the surface of the diverter or the first wall to identify areas requiring repair before depositing the refractory metal, The method according to any one of claims 1 to 3, wherein the step of depositing the refractory metal includes depositing the refractory metal in the area requiring repair.

9. The method according to any one of claims 1 to 3, comprising the steps of providing a mask on a portion of the surface of the diverter or the first wall before depositing the refractory metal, and removing the mask after depositing the refractory metal.

10. The method according to any one of claims 1 to 3, further comprising the step of milling a portion of the surface of the diverter or first wall on which the refractory metal has been deposited after deposition.

11. The tokamak comprises first and second vacuum pump systems, The method according to any one of claims 1 to 3, wherein the first vacuum pump system is used during the normal operation of the tokamak, and the second vacuum pump system is used during the deposition of the refractory metal and during the removal of waste from the deposition and / or subsequent milling.

12. The method according to claim 11, wherein the second vacuum pump system includes a scroll pump.

13. A method for operating a tokamak, The steps include forming and maintaining a first plasma within the tokamak, The first step of extinguishing the plasma, A step of repairing the diverter or first wall of the tokamak by the method described in any one of claims 1 to 3, The steps of forming a second plasma inside the tokamak and Includes, The pressure inside the tokamak remains below 2500 Pa from the time the first plasma disappears until the second plasma is formed, in this method.

14. Vacuum chamber and A vacuum maintenance system configured to maintain the pressure inside the vacuum chamber at less than 2500 Pa, A first wall and a diverter, each having a surface containing a refractory metal with a melting point exceeding 2000°C, Refractory metal deposition system and In the tokamak, The aforementioned refractory metal deposition system is refractory metal sources, A heating system configured to heat a portion of the refractory metal of the refractory metal source, A positioning system configured to position the heating system and the refractory metal of the refractory metal source in any region of the surface of the first wall or diverter, controller Equipped with, The aforementioned controller, The positioning system positions the heating system and a portion of the refractory metal of the refractory metal source at a target location on the first wall or the surface of the diverter. A tokamak configured such that the heating system heats a portion of the refractory metal in the refractory metal source and melts the portion of the refractory metal on the target area.

15. The tokamak according to claim 14, wherein the heating system is further configured to heat a target area on the surface of the first wall or diverter.

16. The tokamak according to claim 14 or 15, wherein the controller is further configured to perform the step of heating a portion of the refractory metal over a plurality of target areas within a region of the surface of the first wall, thereby coating the region with the refractory metal.

17. The vacuum chamber is equipped with a port, The tokamak according to claim 14 or 15, wherein at least a portion of the refractory metal deposition system is configured to enter the vacuum chamber through the port.

18. The vacuum maintenance system comprises first and second vacuum pump systems and a controller. The tokamak according to claim 14 or 15, wherein the controller is configured to maintain a vacuum during normal operation of the tokamak using the first vacuum pump system and to maintain a vacuum during the deposition of the refractory metal and during the removal of waste from the deposition and / or subsequent milling using the second vacuum pump system.

19. The tokamak according to claim 18, wherein the second vacuum pump system includes a scroll pump.