Material Supply System

Abstract

The present invention provides a material supply system for a plasma system, comprising a container assembly having a plurality of containers and an opening for supplying material to the plasma system, and a material feeder assembly for supplying material to the container assembly, the container assembly being operable to move between a material supply arrangement in which the opening is aligned with the material feeder assembly to allow material to pass through the container assembly, and a plurality of material recovery arrangements in which each one of the containers prevents material from passing through the container assembly to allow recovery of material by the container.

Description

[Technical Field]

[0001] The present invention relates to a material delivery system for a plasma system and a method of operating the same. [Background technology]

[0002] This invention was made under CRADA No. NFE-19-07769 between Tokamak Energy Corporation, UT-Battelle, LLC, the operating contractor for the U.S. Department of Energy's Oak Ridge National Laboratory, and The Trustees of Princeton University, the operating contractor for the U.S. Department of Energy's Princeton Plasma Physics Laboratory. The Government has certain rights in this invention.

[0003] Impurity seeding is a process in which so-called "impurities" are introduced into the plasma vessel of a magnetic confinement plasma system before and / or during plasma operation, either as powders (e.g., particles <250 μm) or granules (e.g., particles >250 μm to several mm). Exemplary impurities are lithium, boron, boron nitride, and carbon. Impurity seeding advantageously enables real-time conditioning of both the plasma and the plasma vessel wall. For example, impurity seeding has been demonstrated to be effective in mitigating damage to the plasma vessel wall during disruptive events and promoting high-confinement plasma operating modes. Furthermore, as the pulse duration of plasma systems increases, real-time control of plasma vessel wall conditioning during the pulse via impurity seeding becomes necessary because conventional methods, such as glow discharge cleaning, cannot be used, for example, in plasma systems with permanently active magnetic fields.

[0004] A known powder dropper system 100 for a magnetic confinement plasma system is shown in Figures 1A and 1B. The powder dropper system includes a primary powder reservoir 102, a secondary powder reservoir 104, a horizontal trough 106 that receives powder from the reservoirs 102, 104, a drop tube 108 through which the powder can enter a plasma vessel (not shown), two piezoelectric actuators 110 operable to vibrate the trough 106 and the secondary reservoir 104 to force the powder on the trough into the drop tube 108, and a powder diverter 112 that includes a lateral tube 112a extending from the drop tube, an arm 112b, and a vessel 112c. Figure 1A shows the powder dropper system in an open configuration, in which the diverter arm 112b does not obstruct the passage 114 of powder through the drop tube and into the plasma vessel. FIG. 1B shows the powder dropper system 100 in a closed configuration, with the diverter arm 112b moving into the drop tube to redirect the powder passage 116 into a receptacle for waste disposal.

[0005] 1A and 1B has a single set of powder reservoirs 102, 104 and is configured to only drop a single type of powder source. However, other known systems can drop up to a total of four different types of powder by having additional powder reservoirs 102, 104, troughs 106, and piezoelectric actuators 110 for each additional powder type.

[0006] However, plasmas are very sensitive to these introduced impurities. For example, in "Initial Results of Boron Powder Injection Experiments in WEST Lower Single-Null L-Mode Plasmas" by Bodner et al., published in HAL Open Science on June 15, 2022, it was reported that boron powder mass injection rates exceeding approximately 17 mg / s can cause disruptions (i.e., instabilities) in the plasma. Therefore, proper calibration and commissioning of the powder dropper system is important.

[0007] Calibrating each set of piezoelectric actuators 110 in powder dropper system 100 involves determining the relationship between the mass flow rate at which powder is dropped and the sinusoidal voltage profile energizing that set of actuators. Mass flow rate can be measured, for example, using an optical flow meter, as known to those skilled in the art. Methods for calibrating powder dropper systems are described, for example, in Section V of "Multiple Powder Droppers for Magnetic Fusion Applications" by Nagy et al., May 16, 2018.

[0008] It is, of course, important that powder not enter the plasma vessel during calibration and / or commissioning of the powder dropper system 100. For this reason, as shown in Figures 1A and 1B, existing systems include a powder diverter 112 for diverting the flow of powder from the drop tube 108 into the vessel 112c.

[0009] One problem with existing systems is that powders of different types (particle size, material, etc.) end up mixed together in the container 112c. These mixed powder types cannot be easily separated and are often discarded, which is wasteful and costly. For example, mixed powders containing lithium require careful handling and disposal because lithium powder reacts with ambient moisture. Summary of the Invention [Problem to be solved by the invention]

[0010] An improved powder dropper system for magnetically confined plasma systems is desirable. [Means for solving the problem]

[0011] According to a first aspect of the present invention, a material supply system for a plasma system is provided. The material supply system includes a container assembly having a plurality of containers and an opening for supplying material to the plasma system, and further includes a material feeder assembly for supplying material to the container assembly. The container assembly is operable to move between a material supply arrangement, in which the opening is aligned with the material feeder assembly to allow material to pass through the container assembly, and a plurality of material recovery arrangements, in which each one of the containers prevents material from passing through the container assembly and allows the material to be recovered by that container. This system advantageously allows different forms of material (e.g., different powder size ranges, shapes, etc.) to be collected in different containers so that mixing of different material forms can be avoided. The system also advantageously allows for a greater amount of material to be recovered compared to a system having only one container.

[0012] Optionally, the material feeder assembly includes a material selection mechanism for selectively feeding one or more of the plurality of different materials into the container assembly. The materials may be physically and / or chemically different from one another. For example, the different materials may have the same or substantially the same chemical composition but have particles of different sizes or shapes or may have different physical states (e.g., the materials may be supplied in liquid form, in some cases). Alternatively, or in addition, the different materials may have different chemical compositions from one another. For example, the different materials may each be one of lithium, boron, and carbon, each in powder or granular form. Such a system may collect the different materials in different containers, so that mixing of the different materials can be avoided, at least to some extent. Collecting the different materials separately can lead to significant cost savings. In a specific example, a first container is used to collect lithium, a second container is used to collect carbon, and a third container is used to collect boron. In this specific example, the steps required to extract lithium from the mixed powder can be avoided without losing lithium.

[0013] Preferably, but not necessarily, the number of containers in the container assembly is equal to or greater than the number of different materials that the material feeder assembly can supply (e.g., is configured to supply). For example, there may be a one-to-one correspondence between the different materials that can be supplied and the containers. This ensures that there is at least one container for each different material so that mixing of the different materials can be avoided.

[0014] The material supply system may also include a controller configured to control the configuration of the container assembly depending on the material determined for which the material feeder assembly next requires calibration and / or commissioning. For example, if the material feeder assembly next requires calibration for material "A," the controller is configured to change the configuration of the container assembly to the corresponding configuration "A." If the material feeder assembly subsequently requires calibration for material "B," the controller is configured to change the configuration of the container to the corresponding configuration "B." In this manner, the system provides the functionality necessary to collect different materials "A" and "B" into separate containers, thereby avoiding mixing. As noted above, material "A" and material "B" may differ in their physical and / or chemical properties.

[0015] In some embodiments, the container assembly may be operable to simultaneously move the opening and the container. For example, the opening may be provided in a mount that supports the container (e.g., a plate having a plurality of openings with containers provided therein, at least one of the openings not having a container). The container assembly may be operable to move the mount (e.g., rotate the plate) to obtain each of the material supply and material return configurations.

[0016] Optionally, the plurality of containers and openings are arranged collinearly with one another.

[0017] Alternatively, the multiple containers and openings may be arranged circumferentially relative to one another (i.e., spaced apart from one another around a circle or polygon), which may be more compact than a linear arrangement and may conserve space (in at least one direction) within the material supply system.

[0018] The material supply system may include one or more linear actuators operable to move each container along a linear path, for example, between a first position in which the respective container is positioned to collect material entering the container assembly and a second position in which the respective container allows material to pass through the container assembly.

[0019] The material supply system may alternatively include one or more rotary actuators operable to move each container along a curvilinear path, for example, between a first position in which the respective container is positioned to collect material entering the container assembly and a second position in which the respective container allows material to pass through the container assembly.

[0020] The linear or rotary actuators may be configured to be pneumatic or hydraulic, i.e., operate with air or hydraulic pressure. Pneumatic and hydraulic pressures are not affected by the high magnetic fields present in some plasma systems. Conversely, the normal operation of other types of actuators, such as electromagnetic actuators, may be adversely affected by these magnetic fields. Therefore, pneumatically or hydraulically operated actuators advantageously provide improved control over the system.

[0021] Optionally, the material supply system includes a tubular assembly having a first tubular body extending from the material feeder assembly to the container assembly and a second tubular body extending away from the container assembly, through which material can pass. An end of the second tubular body distal from the material feeder assembly can be configured to couple with a container wall of the plasma system. The tubular assembly can facilitate coupling between the material supply system and the plasma system so that material can be supplied from the material feeder assembly into the plasma system.

[0022] The material feeder assembly may be positioned relative to the container assembly such that, in use, material dispensed by the feeder assembly enters the container assembly by gravity. Advantageously, no mechanism is required to propel the material (against gravity), saving energy costs and simplifying system design. The material feeder assembly may be, for example, a conventional dropper system as shown in FIG. 1.

[0023] The materials can include one or more of powdered or granular lithium, boron, boron nitride, and carbon. Other powdered or granular elements with low atomic numbers (e.g., Z<20) can also be used. The powders can include particles having an average diameter (or other characteristic largest dimension) of less than 250 μm. The granules can have an average diameter (or other characteristic largest dimension) between 250 μm and 5 mm. Each set of powdered or granular lithium, boron, or carbon can similarly include powders / granules with different physical properties, such as different sizes, size distributions (i.e., average size and standard deviation), and / or shapes (e.g., spherical, cubic, etc.).

[0024] The material supply system may further include a material flow meter for use in calibrating the material feeder assembly, the material flow meter being positioned relative to the material feeder assembly and the container assembly such that the material flow meter can measure the flow rate (e.g., mass flow rate) of material being supplied to the container assembly.

[0025] In a specific example, a material flow meter includes (i) a calibrated LED or other light emitting element configured to emit a collimated light beam along a path across the flow of material into a container assembly, and (ii) a detector configured to measure the light intensity of the collimated light beam reaching the detector. As material is fed into the container assembly, particles of the fed material intercept the collimated light beam, reducing the measured light intensity. By monitoring this change in light intensity, the flow rate (e.g., mass flow rate) and total mass of material being fed into the container assembly can be calculated in a known manner.

[0026] During calibration, one of the multiple containers can be positioned to collect material entering the container assembly so that the material does not reach the plasma system, thereby avoiding introducing uncontrolled (e.g., excessive) or inaccurate amounts of material into the plasma system.

[0027] The calibration process itself involves measuring the material flow rate using a material flow meter and adjusting the control parameters of the material feeder assembly in response to the measured flow rate. For example, by adjusting the amplitude and / or frequency of the sinusoidal potential of the piezoelectric actuator 110 until a desired material flow rate (e.g., 10 mg / sec) is obtained. These control parameters can be used to accurately dispense a desired amount of material. For example, 10 mg can be dispensed by the material feeder assembly by operating the material feeder assembly for 1 second using these determined control parameters.

[0028] According to a second aspect of the present invention, there is provided a plasma system comprising a material supply system as described above in relation to the first aspect.

[0029] According to a third aspect of the present invention, there is provided a method of operating a material supply system installed in a plasma system. The material supply system includes a plurality of containers and a material feeder assembly for supplying material to the plasma system. The material supply system may be similar to that described in relation to the first aspect. The method includes selecting a first container from the plurality of containers and moving the first container to a position that allows material supplied by the material feeder assembly to be collected in the first container. Advantageously, operation of the material supply system allows for the collection of material into a different container.

[0030] The method can further include selecting a first material from a plurality of different materials supplied to the plasma system by the material feeder assembly and collecting the first material in a first container. Advantageously, operation of the material supply system allows for selective collection of different materials in different containers. For example, container "A" can be used to collect material "A," container "B" can be used to collect material "B," container "C" can be used to collect a mixture of material "C," etc.

[0031] Optionally, the method is performed during calibration and / or commissioning of the material feeder assembly for the first material and / or other materials that may be supplied by the material feeder assembly. The calibration process is described above in connection with the first aspect and will not be repeated in full here. Suffice it to say that the calibration process includes (i) measuring the material flow rate while the container is in place, and (ii) adjusting control parameters of the material feeder assembly in response to the measured material flow rate. The commissioning process of the material feeder assembly is performed in substantially the same manner.

[0032] The calibration process can be repeated for one or more additional materials. For example, after calibration and / or commissioning of a first material is complete, a second container can be selected from the plurality of containers and moved to a position from which the second material can be retrieved from the material feeder assembly. The first container can be moved away from its material retrieval position to allow space for the second container. The material feeder assembly can then select a second material from the plurality of different materials, feed the second material to the plasma system, and retrieve the material in the second container.

[0033] Optionally, the material supply system further comprises an opening, and after completion of calibration and / or commissioning of the first and / or second materials, the method further includes moving the opening to a position that allows the material supplied by the material feeder assembly to enter the plasma chamber of the plasma system, and operating the material feeder assembly to introduce the first and / or second materials into the plasma chamber.

[0034] In some cases, the container assembly may be provided (e.g., sold) separately from the material feeder assembly. For example, a container assembly for use in a material supply system of a plasma system may be provided, the container assembly comprising a plurality of containers and an opening through which material can pass. The container assembly is operable to move between a material supply arrangement, in which the openings are arranged to allow material to pass through the container assembly, and a plurality of material recovery arrangements, in which each one of the containers prevents material from passing through the container assembly, allowing recovery of the material by that container. Further details of the container assembly are described above in connection with the first aspect and will not be repeated here for the sake of brevity. [Brief explanation of the drawings]

[0035] [Figure 1] A known powder dropper system. [Figure 2A-2B] FIG. 1 is a cross-sectional view of an exemplary container assembly. [Figure 3] FIG. 2 is a schematic diagram of a top view of a container assembly. [Figure 4] FIG. [Figure 5] 1 is a cross-sectional view of an exemplary container. DETAILED DESCRIPTION OF THE INVENTION

[0036] The present disclosure proposes a material supply system for a plasma system. In use, the supply system supplies material into a plasma of the plasma system or into a plasma confined by the plasma system. The supply system includes a vessel assembly having a plurality of vessels and an opening for supplying material to the plasma system, and a material feeder assembly for supplying material to the vessel assembly.

[0037] A material feeder assembly can supply one or more of a plurality of different materials to a plasma system. Materials can be classified as different according to their physical properties and / or their chemical properties. Two materials are in different categories (i.e., different) if any of these properties are (substantially) different. For example, two materials with the same chemical composition can be different if they have different physical forms. For example, one of the materials is a liquid and the other is a solid, the materials are allotropes (e.g., different carbon allotropes), or the materials have particles of different sizes, shapes, etc.

[0038] Exemplary materials include elemental (i.e., greater than 99% pure) powders or granules of lithium, boron, boron nitride, or carbon, or alloys thereof. Other exemplary materials include other powdered or granular elements and their alloys having low atomic number elements (e.g., Z<20).

[0039] The proposed container assembly can be moved between a variety of different configurations, such as a material supply configuration in which the opening is aligned with the material feeder assembly to allow material to pass through the container assembly, to a further plurality of material recovery configurations in which different containers prevent material from passing through the container assembly. Because each container can receive material when positioned to prevent the passage of the material, the proposed material supply system can recover different materials using different containers. Advantageously, the proposed material supply system can therefore at least mitigate the problem of mixing different materials.

[0040] 2A and 2B show cross-sectional views of a material supply system 200. The material supply system 200 includes a container assembly 202 and a material feeder assembly (not shown). An exemplary material feeder assembly that can be used with the container assembly 202 is the powder dropper system 100 of FIG. 1, which can supply multiple different materials to the container assembly 202. However, other known material feeder assemblies can be substituted for this system depending on the operational needs of the plasma system.

[0041] The receptacle assembly 202 includes a plurality of receptacles 206 and openings 208 circumferentially arranged on a mount 210. The receptacles 206 are secured to the mount using suitable mechanical fasteners, such as shoulder screws; however, other types of mechanical fasteners may be used. The mount is mechanically coupled to a shaft 214 via a rotational bearing 212, and the shaft 214 is mechanically coupled to a rotational actuator device 216 that provides rotational drive to the mount.

[0042] The rotary actuator device 216 includes a stepper motor 216a and a belt drive 216b for amplifying the rotational speed of the stepper motor 216a. The rotary stepper motor 216a is operable to move each of the containers 206 along a curved path (e.g., along an arc on the mount 210). The shaft 214 is centered relative to the containers such that, upon actuation of the stepper motor 216a, the mount 210, and thus the containers 206 and openings 208, are rotated about an axis defined by the shaft 214. In the illustrated example, the openings 208 are provided with a through funnel 218, although this is not required.

[0043] The material supply system 200 further includes a tubular assembly 204 through which material can pass from the material feeder assembly 202 to a plasma system (not shown). The direction of material is indicated by the arrows in FIG. 2A . The tubular assembly includes a first tubular assembly extending from the material feeder assembly to the plasma system and a second tubular assembly extending away from the vessel assembly 202 to the plasma system (not shown). Thus, the vessel assembly 202 can selectively allow or prevent passage of material from the material feeder assembly to the plasma system by appropriate positioning of the vessel and opening 208 (and funnel 218). The end of the second tubular body closest to the plasma system is provided with a coupling mechanism for attaching or otherwise securing the tubular body to the vessel wall of the plasma system.

[0044] The material feed system 200 further includes a controller (not shown) that controls the positioning of the container assemblies via the rotary actuator device 216 so that any particular one of the containers 206 can be positioned to prevent material from being passed from the material feeder assemblies to the plasma system. The positioning of the container assembly can be controlled depending on the material that the material feeder assembly is determined to next require calibration. Limit switches are used to allow the controller to determine the current position of the container assembly, although other methods of determining the current position of the container assembly may be used.

[0045] For example, if the material feeder assembly next requires calibration for material of type or shape "A," the controller changes the configuration of the container assembly to the corresponding configuration "A." In configuration "A," container "A" is moved to a position where it can collect material dispensed from the material feeder assembly during the calibration procedure. If the material feeder assembly then requires calibration for material of type or shape "B," the controller changes the configuration of the container assembly to the corresponding configuration "B." In configuration "B," container "B" (different from container "A") is moved to a position where it can collect material dispensed from the material feeder assembly during the calibration procedure. As container "B" is moved to its position, container "A" is moved away from its collection position. After the material feeder assembly is properly calibrated, the controller can change the configuration of the container assembly so that opening 208 and funnel 218 are positioned to allow material to pass through the container assembly and enter the plasma system. In this way, the material supply system has the necessary functionality (i) to collect material "A" and material "B" in separate containers to avoid mixing of the materials, e.g., during calibration, and (ii) to supply the materials to the plasma system, e.g., after calibration.

[0046] When used in a plasma system, the interior of the vessel assembly 202, including the lower portion 202a and the upper portion 202b, can be under a partial vacuum, while the stepper motor 216a is under a higher pressure, such as ambient pressure. Therefore, to facilitate rotation of the mount 210, a bellows-sealed rotary feedthrough 220 is used to connect the stepper motor 216a to the mount 210. The vessel assembly may further include an electrical feedthrough (not shown) for a limit switch cable (not shown).

[0047] In the illustrated example, stepper motor 216a is a pneumatic stepper motor. A hydraulic stepper motor is a suitable alternative. While pneumatically or hydraulically operated actuators are immune to magnetic fields, electromagnetic actuators, without magnetic shielding, are susceptible to interference issues in magnetic fields above 0.03 T. The magnetic field strength in a typical plasma system far exceeds this value. Therefore, pneumatic or hydraulic stepper motors can provide improved control and stability compared to other stepper motors. In a specific example, the pneumatic stepper motor is configured to rotate three degrees per valve actuation, and the belt drive 216b triples the rotational speed. More generally, the rotation angle per valve actuation and the speed multiplication factor of the belt drive can vary in various implementations depending on the required step size and rotational speed. Optionally, a belt tensioning block (not shown) can be provided to assist the belt drive.

[0048] In the example shown, the rotary bearing 212 is made from a ceramic (e.g., ZrO2) with a retainer made from PEEK (or any other vacuum-compatible polymer known to those skilled in the art), however, other rotary bearings made from different materials can be used.

[0049] The material supply system may further include a material flow meter (not shown) for use in calibrating the material feeder assembly, the material flow meter being positioned relative to the material feeder assembly and the container assembly such that the material flow meter can measure the flow rate (e.g., mass flow rate) of material being supplied to the container assembly.

[0050] The material flow meter can be an optical flow meter in some embodiments. In a specific example, the material flow meter includes (i) a calibrated LED or other light emitting element configured to emit a (preferably parallel) light beam along a path that intersects the flow of material into the container assembly, and (ii) a detector configured to measure the light intensity of the light beam reaching the detector. As material is delivered to the container assembly, the delivered material blocks the light beam, reducing the measured light intensity. By monitoring this change in light intensity, the flow rate (e.g., mass flow rate) and total mass of material delivered to the container assembly can be calculated in a known manner.

[0051] 3 is a schematic diagram of a top view of the container assembly 202 of FIGS. 2A and 2B. As shown, the mount 210 of the container assembly 202 includes three containers 306a, 306b, and 306c and an opening 208 with a through funnel 218. The particular container assembly shown is adapted for use with a material feeder assembly capable of feeding two or three different materials, such as powdered lithium and carbon and / or boron.

[0052] In the specific example shown, a first container 306a is provided to receive a first material from the feeder assembly, a second container 306b is provided to receive a second material, different from the first material, from the feeder, and a third container 306c is provided to receive either or both of the first and second materials from the feeder, for example, when the feeder assembly is operated to simultaneously feed a mixture of the first and second materials. The controller then controls the placement of the container assemblies to ensure that the corresponding container is moved to a position to retrieve its corresponding material (e.g., during calibration).

[0053] More generally, the number of containers in the container assembly can be equal to or greater than the number of different materials that the material feeder can supply (i.e., supply individually), thereby ensuring that a separate container is provided for each different material.

[0054] The operation of the material delivery system shown in FIGS. 2A, 2B and 3 will be described with reference to the method flow diagram 400 shown in FIG.

[0055] In step 402, a first container is selected from a plurality of containers in a material delivery system, for example, during calibration of the material delivery system.

[0056] In step 404, the first container is moved to a position that allows the material supplied by the material feeder assembly to be collected in the first container.

[0057] Optionally, in step 406, a first material is selected from a plurality of different materials that the material feeder assembly can feed to the plasma system.

[0058] Optionally, in step 408, the first material is collected in a first container.

[0059] Optionally, in step 410 (not shown), the first container is moved away from its collection position and the opening of the container assembly is moved to a position that allows material supplied by the material feeder assembly to enter the plasma system.

[0060] The method of Figure 4 is performed during calibration and / or commissioning of a material feeder assembly. Calibration / commissioning (referred to interchangeably herein) can be performed for any one or combination of several different materials that the material feeder assembly is capable of feeding. For example, with specific reference to the system described in connection with Figure 3, the calibration / commissioning can be performed for only the first material, only the second material, or a mixture of the first and second materials in any volume or mass fraction. Those skilled in the art will understand that the material for which the material feeder assembly is calibrated will depend on the operational needs of the plasma system, and in particular the plasma.

[0061] During calibration, one of the containers is positioned to collect material entering the container assembly and prevent it from reaching the plasma system, thus avoiding uncontrolled or inaccurate amounts of material being introduced into the plasma system.

[0062] Calibration involves measuring the material flow rate using a material flow meter while the container is in the retrieve position. The control parameters of the material feeder assembly can be adjusted in response to the measured material flow rate. In a specific example, the amplitude and / or frequency of the sinusoidal potential of the piezoelectric actuator are adjusted until a desired material flow rate (e.g., 10 mg / sec) is achieved, and these control parameters can then be used to accurately dispense the desired amount of material. For example, 10 mg can be dispensed by the material feeder assembly by operating the material feeder assembly for 1 second using these determined control parameters.

[0063] Steps 402 through 408 may then be repeated for any other one or combination of the multiple different materials that the material feeder assembly can supply until a calibration has been performed for each different material, or until such time as the material supply system is required to supply each one of these materials to the plasma system. Steps 402 through 408 may also be repeated for the same material if recalibration is required.

[0064] 4 is not intended to be limiting. For example, step 406 may occur before step 402 and / or step 404. If steps 402 through 408 are repeated for different materials and / or containers, step 410 may occur in the process of moving the first container away from its collection location.

[0065] FIG. 5 shows an enlarged cross-sectional view of the vessel 206 of the material delivery system 200 shown in FIGS. 2A and 2B.

[0066] As shown, the container 206 defines a cap portion 206a having a tapered inner surface, a base portion 206b, and a sidewall portion 206c extending between the cap portion 206a and the base portion 206b. The interior volume defined by these portions is suitable for receiving a material. In a specific example, the interior volume of the container 206 is 80 cm3. Larger or smaller container volumes are also possible.

[0067] FIG. 5 shows a removable pin 222 for removing the container 206 from the lower portion 202a to the upper portion 202b of the container assembly. The pin 222 includes a latching device 224 at one end for engaging the tapered inner surface of the cap portion 206a for this purpose. The opposite end is provided with a grip to allow an operator to easily remove the container. In a specific example, the pin 222 is a detent pin, but other mechanisms for removing the container are possible. In this manner, a container 206 filled with material can be removed after pressurizing the container assembly 202 to ambient pressure. To maintain cleanliness within the assembly 202 while the container 206 is being replaced, the assembly 202 can be filled with dry nitrogen gas. Once pressurized, the container 206 can be easily removed (e.g., by hand or using a robotic operator), emptied, and returned to the container assembly.

[0068] The particular material delivery system described above delivers powdered lithium, carbon, and / or boron, but is suitable for delivering other and additional materials, such as powders or granules of other elements (i.e., greater than 99% purity) including low atomic number elements (e.g., Z<20) and their alloys (e.g., boron nitride).

[0069] As will be apparent to those skilled in the art, various modifications are possible within the scope of the present invention. At least the following modifications are possible:

[0070] The container assembly can have multiple openings 208 so that the rotation angle required to move the opening 208 (optionally including the funnel 218) into a position collinear with the tubular body 204 is reduced.

[0071] The number of containers may be more than three, for example there may be four, five, six, seven, eight, nine or ten containers.

[0072] One or more of these vessel assemblies 202 can be stacked so that material passes through multiple vessel assemblies 202 before entering the plasma system. The tubular assembly 204 may include a first tubular body extending from the material feeder assembly to the plasma system and a second tubular body extending away from the vessel assembly 202 to the plasma system, as well as additional tubular bodies extending between adjacent stacked vessel assemblies 202.

[0073] The multiple containers and openings may be arranged collinearly (as opposed to circumferentially) with one another and substantially perpendicular to the longitudinal axis defined by the tubular assembly 204. The rotary actuator device 216 of FIG. 2 is replaced with one or more linear actuators. The one or more linear actuators may move each container along a linear path between a position where the container prevents material from passing through the container assembly and a position where the container does not affect material from passing through the container assembly. Such linear actuators may be provided for each container so that each can be linearly actuated independently of the other containers. Alternatively, the linear actuators may act on the containers collectively to linearly actuate the containers collectively; for example, the linear actuators may act on mounts that support the containers.

[0074] The multiple containers may be arranged circumferentially, with the openings centrally located relative to the containers. The rotary actuator device 216 of FIG. 2 is replaced with multiple linear actuators, each configured to move a respective container between a circumferential position and a central position. The central position corresponds to the containers being co-located with the openings so that material entering the container assembly is collected by the container rather than entering the plasma system through the openings.

[0075] The one or more linear actuators may be pneumatically or hydraulically operated.

[0076] In some instances (e.g., when multiple linear actuators are used), the opening of the container assembly does not move when the container assembly 202 changes position. Instead, to prevent material from passing through the container assembly, one of the containers is moved to a position (i.e., immediately upstream) that prevents material from passing through the opening.

[0077] 2A and 2B may be a dropper-type system whereby material is fed by the feeder assembly to the plasma system by gravity. Alternatively, the material feeder assembly may include a mechanism for propelling material to the plasma system so that the system can be positioned in any given orientation.

[0078] The material supply systems and variations thereof described above may form part of a plasma system that includes a magnetic confinement chamber (or plasma vessel), which may comprise or be part of any suitable device for confining a plasma, such as a tokamak or stellarator.

Claims

1. 1. A material delivery system for a plasma system, the delivery system comprising: a vessel assembly comprising a plurality of vessels and an opening for supplying materials to the plasma system; a material feeder assembly for supplying material to said container assembly; Equipped with A material supply system wherein the container assemblies are operable to move between a material supply arrangement in which the opening is aligned with the material feeder assembly to allow material to pass through the container assembly, and a plurality of material recovery arrangements in which each one of the containers prevents material from passing through the container assembly to allow material to be recovered by the container.

2. The material supply system of claim 1 , wherein the material feeder assembly includes a material selection mechanism for selectively supplying one or more of a plurality of different materials to the container assembly.

3. 3. The material supply system of claim 2, wherein the number of containers in the container assembly is equal to or greater than the number of different materials that the material feeder assembly is capable of supplying.

4. 4. The material supply system of claim 2, further comprising a controller configured to control the positioning of the container assembly according to the material determined to be the next material for which the material feeder assembly requires calibration and / or commissioning.

5. The material supply system according to claim 1 , wherein the plurality of containers and the openings are arranged in the same line as each other.

6. The material supply system of claim 1 , wherein the plurality of containers and the openings are circumferentially arranged relative to one another.

7. 7. The material dispensing system of claim 5 or 6, further comprising one or more linear actuators operable to move each container along a linear path.

8. The material dispensing system of claim 6 , further comprising one or more rotary actuators operable to move each container along a curved path.

9. 9. A material feeding system according to claim 7 or 8, wherein the or each linear actuator or the or each rotary actuator is pneumatic or hydraulic.

10. 10. The material supply system of claim 1, further comprising a tubular assembly having a first tubular body extending from the material feeder assembly to the container assembly and a second tubular body extending away from the container assembly, wherein material can pass through the tubular assembly.

11. The material feed system of claim 10 , wherein an end of the second tubular body distal from the material feeder assembly is configured to mate with a vessel wall of a plasma system.

12. 12. The material supply system of claim 1, wherein the material feeder assembly is positioned relative to the container assembly such that material supplied by the feeder assembly enters the container assembly by gravity.

13. 13. A material supply system according to any one of claims 1 to 12, wherein the material comprises a powdered or granular element having an atomic number less than 20, in particular one or more of lithium, boron, boron nitride and carbon.

14. 14. The material supply system of claim 1, further comprising a material flow meter used to calibrate the material feeder assembly.

15. A plasma system comprising a material supply system according to any one of claims 1 to 14.

16. 1. A method of operating a material supply system installed in a plasma system, the material supply system comprising a plurality of containers and a material feeder assembly for supplying material to the plasma system, the method comprising: selecting a first container from the plurality of containers; moving the first container to a position that allows material supplied by the material feeder assembly to be collected in the first container; A method comprising:

17. selecting a first material from a plurality of different materials supplied to the plasma system by the material feeder assembly; collecting the first material in the first container; 17. The method of claim 16, further comprising:

18. 20. The method of claim 17, wherein the method is performed during calibration and / or commissioning of the material feeder assembly for the first material.

19. 18. The method of claim 16 or 17, wherein calibrating the material feeder assembly includes measuring a material flow rate while the first container is in the position.

20. 20. The method of claim 19, further comprising adjusting a control parameter of the material feeder assembly in response to the measured material flow rate.

21. After completing calibration and / or commissioning of the first material, the method further comprises: (i) selecting a second container from the plurality of containers; (ii) moving the first container away from its material collection location; (iii) moving the second container to a position where a second material can be retrieved from the material feeder assembly; and 21. The method of any one of claims 18 to 20, further comprising:

22. operating the material feeder assembly to supply the second material from the plurality of different materials to the plasma system; collecting the second material in the second container; and 22. The method of claim 21 further comprising:

23. The material supply system further comprises an opening, and after completion of calibration and / or test run of the first material and / or second material, the method further comprises: moving the opening to a position that allows material supplied by the material feeder assembly to enter a plasma chamber of the plasma system; operating the material feeder assembly to introduce the first material and / or the second material into the plasma chamber; 23. The method of any one of claims 18 to 22, further comprising:

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