Method and system for maintaining cryogenic temperatures

Abstract

Methods and systems for maintaining a device at cryogenic temperatures are described, as well as systems configured to maintain such temperatures. In one example, the method and system include maintaining the temperature of a superconducting magnet, wherein the superconducting magnet includes an internal reservoir, the method and system comprising the steps of: adding a first portion of cryogenic slurry to the internal reservoir; determining that the first portion has at least partially melted; and replacing the first portion of cryogenic slurry with a second portion of cryogenic slurry.

Description

Technical Field

[0001] This disclosure relates to maintaining equipment at cryogenic temperatures and to systems configured to maintain such temperatures. Background Technology

[0002] Superconducting objects, such as superconducting magnets, need to be cooled during use to maintain a suitable temperature for superconductivity. If the temperature of a superconductor is allowed to rise, it may exceed its critical temperature and introduce resistance into the circuit. In existing systems such as the levitating dipole experiments at Columbia University and MIT, helium cryostats have been used, featuring tubular heat exchangers for initial nitrogen magnet cooling and routine helium recooling. In other examples, such as JP2006052921A, an object is immersed in a cryogen to cool to the desired temperature, and the object is placed in a cooling tank. One or more cryogens, typically liquid hydrogen or liquid nitrogen, provide the cryogenic temperature to cool the system. While immersing a superconductor in a vessel filled with cryogen provides a cooling effect, this is time-limited. To improve the usable time, cryogen can be pumped around the system to continuously refresh the cryogen and maintain the desired temperature.

[0003] However, these systems cannot provide sufficient temperature stability in environments where, for example, superconducting magnets can move. Summary of the Invention

[0004] The object of this invention is to provide a system or method for maintaining the cryogenic temperature of devices such as superconducting magnets.

[0005] In one aspect, the invention may include a method for maintaining the temperature of a superconducting magnet, wherein the superconducting magnet includes an internal reservoir, the method comprising the steps of: adding a first portion of cryogenic slurry to the internal reservoir; determining that the first portion has at least partially melted; and replacing the first portion of cryogenic slurry with a second portion of cryogenic slurry.

[0006] Optionally, the cryogenic slurry contains one or more of nitrogen, neon, hydrogen, argon, oxygen, and helium.

[0007] Optionally, the cryogenic slurry comprises a liquid and a solid of the same material. Optionally, the cryogenic slurry comprises a liquid and a solid of different materials. Optionally, the cryogenic slurry is a mixture of different materials. Optionally, the first portion and the second portion of the cryogenic slurry are obtained from an external reservoir. Optionally, the first and second portions are obtained from the same external reservoir. Optionally, the external reservoir includes a slurry generating device. Optionally, the process includes connecting and / or disconnecting the internal reservoir from the external reservoir. Optionally, a valve is included, configured to separate the first portion of the cryogenic slurry from the second portion of the cryogenic slurry during operation of the superconducting magnet. Optionally, the valve allows the first portion of the magnetic slurry to be separated from the second portion of the magnetic slurry. Optionally, the internal reservoir and the external reservoir are disconnected during operation of the superconducting magnet and reconnected between operating events of the superconducting magnet. This allows operation of the superconducting magnet without connection to an external reservoir.

[0008] Optionally, the first portion is added via the inlet of the internal reservoir and removed via the outlet of the internal reservoir. Optionally, the cryogenic slurry of the first portion is removed simultaneously with the addition of the cryogenic slurry of the second portion. Optionally, the second portion is used to advance the removal of the first portion. Optionally, determining that the first portion has at least partially melted includes determining that the solid portion has dropped below a preset threshold. Optionally, determining that the first portion has at least partially melted includes monitoring one or more of time and temperature.

[0009] Optionally, determining that the first portion has at least partially melted includes monitoring a portion of the cryogenic slurry that has become liquid. Optionally, the first portion is replaced when a threshold portion of the slurry has become liquid. Optionally, the process includes a step of circulating a portion of the cryogenic slurry within an internal reservoir. Optionally, the process includes a step of cooling the superconducting magnet to its operating temperature before adding the first portion of the cryogenic slurry. Optionally, the process includes repeatedly adding and replacing additional portions of the cryogenic slurry. Optionally, the process includes operating the superconducting magnet between the steps of adding cryogenic slurry to the internal reservoir and replacing the cryogenic slurry in the internal reservoir. Optionally, operating the superconducting magnet includes one or more of the following: changing the position of the superconducting magnet and applying current to the superconducting magnet. Optionally, changing the position of the superconducting magnet includes suspending the superconducting magnet.

[0010] Optionally, a closed-loop process is included for recooling the cryogenic slurry of the first portion for subsequent replacement. Alternatively, the cryogenic slurry of the first portion is recooled for subsequent replacement.

[0011] Optionally, the system includes a step of determining the time (or time period) for replacing the cryogenic slurry in the first section. Optionally, the prediction system includes a machine learning system. Optionally, a Kalman filter. Optionally, the prediction system includes a thermal system model. Optionally, the prediction system is configured to receive multiple measurements from one or more sensors associated with the superconducting magnet. Optionally, the machine learning method is trained to maximize the magnet's uptime and / or minimize its downtime and / or maximize the plasma duration. The prediction system can improve the maintenance of the superconducting magnet's temperature.

[0012] Optionally, it includes controlling one or more temperature control systems. Optionally, the temperature control system includes one or more heating or cooling systems. Optionally, the temperature control system is controlled based on the performance of the superconducting magnet. Optionally, the temperature control system is electrically powered. Optionally, the temperature control system is configured to heat or cool part of the internal reservoir. Optionally, the temperature control system includes one or more phase change materials. Optionally, the phase change material is located in the superconducting magnet and / or in the internal reservoir. Optionally, the phase change material is configured to maintain a desired temperature during replacement of the cryogenic slurry. Optionally, the controller is configured to monitor the temperature of one or more phase change materials and initiate preemptive action based on the monitored temperature. Optionally, one or more temperature control systems are configured to cause stratification of the internal reservoir and / or ensure the homogeneity of the internal reservoir and / or prevent stratification of the internal reservoir. Optionally, the superconducting magnet includes one or more pumps to control the stratification of the internal reservoir. Optionally, stratification is controlled when the first part is replaced with a second part. Optionally, the slurry in one or more slurry containers may be separated into layers.

[0013] Optionally, the process includes determining a variable flow rate of the pump to replace the cryogenic slurry in the first section. Optionally, the process includes monitoring one or more temperature sensors and controlling the flow rate based on one or more temperature sensors. Optionally, the temperature sensors are configured to determine the state of the cryogenic slurry. Optionally, delta-pressure is used to determine the state of the cryogenic slurry. Optionally, the variable flow rate is increased if a larger percentage of liquid slurry is determined. Optionally, the flow rate depends on the heat transfer coefficient between the cryogenic slurry and the internal reservoir.

[0014] Optionally, the step of replacing the first portion of the cryogenic slurry with the second portion includes replacing one or more cryogenic slurry containers within the inner reservoir. Optionally, one or more containers are shaped to mate with one or more recesses of the inner reservoir. Optionally, one or more containers are substantially identical. Optionally, the containers are oriented such that the solid portion of the cryogenic slurry inside them is facilitated toward the thermal interface of the inner reservoir. Optionally, the containers are individually monitored. Optionally, the containers have thermal interfaces. Optionally, the interfaces are configured to engage with corresponding interfaces of the inner reservoir. Optionally, the containers include inlets to allow replacement of the cryogenic slurry. Optionally, the containers are configured to allow the cryogenic slurry to be recooled within the containers. The use of containers can reduce magnet contamination and / or increase reloading speed.

[0015] In one aspect, the invention may include a system for maintaining the temperature of a superconducting magnet, wherein the superconducting magnet includes an internal reservoir, the system comprising: an external reservoir for holding cryogenic slurry; one or more containers for moving the cryogenic slurry into the internal reservoir; and a controller configured to: determine the thermal state of one or more cryogenic slurry containers within the internal reservoir; and, based on the determination, replace the one or more containers containing the cryogenic slurry with one or more additional cryogenic slurry containers. The above options may be applied to this aspect.

[0016] In one aspect, the invention may include a system comprising a controller configured to implement any or more of the methods described above. Optionally, the system is configured to maintain the temperature of the superconducting magnet.

[0017] In one aspect, the invention may include a system for maintaining the temperature of a superconducting magnet, wherein the superconducting magnet includes an internal reservoir, the system comprising: an external reservoir for holding cryogenic slurry; a pump for moving a portion of the cryogenic slurry into the internal reservoir; and a controller configured to: determine the thermal state of the portion of cryogenic slurry in the internal reservoir; and based on the determination, control the pump to replace the first portion of the cryogenic slurry with a second portion of the cryogenic slurry.

[0018] Optionally, the external reservoir can be repeatedly connected to the internal reservoir. Optionally, the internal reservoir includes a path extending between an inlet and an outlet. Optionally, a pump is configured to pump a first portion and a second portion through the inlet to the internal reservoir and pump them out of the outlet. Optionally, the pump is configured to pump the first portion and the second portion synchronously. Optionally, the inlet and outlet are each repeatedly connected to the external reservoir. Optionally, the external reservoir includes a cryogenic generator for generating cryogenic slurry and cooling cryogenic slurry, or one or more of these processes. Optionally, the superconducting magnet is movable, and optionally, the system includes a docking station to position and / or orient the superconducting magnet when replacing the cryogenic slurry. Optionally, the superconducting magnet includes a guide configured to guide the position of the superconducting magnet to and from the docking station.

[0019] Optionally, the superconducting magnet is a levitation magnet. Optionally, the superconducting magnet is housed within a pressure vessel, and the external reservoir is located outside the pressure vessel. Optionally, the internal reservoir includes one or more fins configured to improve thermal conductivity of the cryogenic slurry. Optionally, the fins extend into the internal reservoir. Optionally, the internal reservoir includes a pump to move the cryogenic slurry about the internal reservoir. Optionally, the internal reservoir includes a passive thermal system configured to enhance heat transfer to the cryogenic slurry. Optionally, the passive thermal system is driven by gravity and / or the movement of the superconducting magnet. Optionally, the passive thermal system allows solid refrigerant in the slurry to settle at a first position and allows the liquid portion of the slurry to settle at a second position. Optionally, the external reservoir and / or the connector between the external reservoir and the internal reservoir are thermally insulated.

[0020] In one aspect, the invention may include a method for maintaining the temperature of an object, wherein the object includes an internal reservoir, the method comprising the steps of: adding a first portion of coolant slurry to the internal reservoir; determining that the first portion has at least partially melted; and replacing the first portion of coolant slurry with a second portion of coolant slurry. Optionally, any one or more of the steps described herein may be included, and the object may replace a magnet or a superconducting magnet. The system and method may be used on other objects that require cooling during a period of time when they are disconnected from a coolant source.

[0021] In one aspect, the invention may include a system for maintaining the temperature of an object, wherein the object includes an internal reservoir, the system comprising: an external reservoir for holding cryogenic slurry; a pump for moving a portion of the cryogenic slurry into the internal reservoir; and a controller configured to: determine the thermal state of the portion of cryogenic slurry in the internal reservoir; and based on the determination, control the pump to replace the first portion of the cryogenic slurry with a second portion of the cryogenic slurry.

[0022] Optionally, the object includes a medical device. Optionally, an MRI system. Optionally, the object is portable. Optionally, the object is a quantum computer. Optionally, the system is configured to maintain the temperature of a portion of a helium cryogenic cooler. Optionally, the system provides an operational buffer to the helium cooling system.

[0023] In one aspect, this disclosure may include a method for maintaining the temperature of an object, wherein the object includes one or more internal spaces, the method comprising the steps of: adding a first portion of cryogenic slurry to one or more internal spaces; determining that the first portion has at least partially melted; and replacing the first portion of cryogenic slurry with a second portion of cryogenic slurry. Optionally, the object is a superconducting magnet. Optionally, a levitation superconducting magnet.

[0024] Optionally, the internal space includes internal compartments. Optionally, the cryogenic slurry of the first portion and the cryogenic slurry of the second portion are held in one or more containers. Optionally, replacement includes removing one or more containers holding the cryogenic slurry of the first portion and replacing them with one or more containers holding the second portion. Optionally, one or more containers are shaped to mate with specific recesses or openings in the superconducting magnet.

[0025] In one aspect, this disclosure may include a system for maintaining the temperature of a superconducting magnet, wherein the superconducting magnet includes an internal reservoir. The system includes: a plurality of containers configured to hold cryogenic slurry; and a superconducting magnet including an internal space to receive one or more of the plurality of containers, wherein a controller is configured to determine the thermal state of a first portion of the cryogenic slurry in one or more of the containers within the internal space; and based on the determination, to control the replacement of the first portion of the cryogenic slurry with a second portion of the cryogenic slurry in one or more of the containers. Optionally, any or more of the foregoing options may be combined with this aspect. Optionally, the system is a medical device, an MRI, a quantum computer, or a portable device.

[0026] As used in this specification, the term "comprising" means "consisting of at least part of...". When interpreting the various statements in this specification that include the term "comprising", features other than those statements or features beginning with that term may also exist. Related terms such as "comprising" and "including" will be interpreted in the same manner.

[0027] References to the range of numbers disclosed herein (e.g., 1 to 10) are also intended to be combined with references to all rational numbers in that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10) as well as any range of rational numbers in that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7). Attached Figure Description

[0028] The following figures will be used to describe an example, in which:

[0029] Figure 1 This is a diagram of a refrigerant reservoir connected to a magnet with internal passageways.

[0030] Figure 2 This is a diagram of a refrigerant reservoir connected to a magnet that has an internal storage tank.

[0031] Figure 3 It is used to be able to Figure 1 A flowchart of a monitoring system for a refrigerant monitoring method implemented on a breathing device.

[0032] Figure 4 It is a diagram of a system with multiple refrigerant containers for interchangeability. Detailed Implementation

[0033] While the following description pertains to superconducting magnets, the principles can be applied to other devices such as magnets, levitating dipoles, electric aircraft, and satellites. Although cryogenic slurries are described, even higher-temperature slurries can be used where higher temperatures are required. In these cases, the slurry can be referred to as a coolant slurry.

[0034] In some cases, this method is used in systems where the equipment or apparatus is mobile, allowing for a non-permanent connection to an external refrigerant reservoir. In some examples, the method is used when the goal is to reduce the time the equipment or apparatus is not moved. In both cases, by delivering a refrigerant slurry to the equipment or apparatus, the system allows for efficient temperature maintenance.

[0035] A suspended dipole is a type of nuclear fusion reactor in which a toroidal magnet (containing a superconducting ring) is suspended within a reactor vessel. In operation, a poloidal magnetic field generated by the magnet is used to contain plasma surrounding the toroidal surface within the reactor vessel. The plasma can then be heated and used to generate electricity through nuclear fusion. The magnet comprises a pressure vessel, within which the superconducting ring or toroidal element, control electronics, charging electronics, and cooling equipment are located. Current must be generated and maintained within the superconducting ring to control the plasma. Both the electronics within the magnet and the plasma surrounding it generate heat. Therefore, cooling or maintaining the magnet at a cryogenic temperature is necessary to keep the superconductor within the magnet below its critical temperature. The fact that the magnet is suspended within the pressure vessel in operation, without external connections or at least insufficient connections to transfer coolant to it, makes this process particularly challenging.

[0036] It has been discovered that sufficient cooling to maintain the cryogenic temperature of a superconductor can be achieved by adding cryogenic slurry to the internal reservoir. The slurry means that the latent heat of fusion (from solid to liquid) can be used, thus providing additional cooling capacity compared to a liquid alone. This also helps ensure that a roughly constant temperature is maintained—since the phase transition occurs at a constant temperature. Using cryogenic slurry allows for rapid switching of the coolant—by pumping and replacing the slurry from the internal reservoir. This means that any downtime, such as for magnets, is minimized.

[0037] A slurry is a mixture of solids floating in a liquid. The transport parameters of a slurry can be varied depending on the relative percentages of solids and liquid. In the presence of sufficient liquid, the slurry can be pumped or moved, for example, by a centrifugal pump. In some cases, a slurry may be referred to as a slurry fluid, where solid particles are again mixed with liquid. Cryogenic slurries are formed from materials at extremely low temperatures. Cryogenic temperatures can be less than 120 K. A phase change must occur for a slurry to form. Common materials include hydrogen, nitrogen, neon, argon, helium, and carbon dioxide.

[0038] Cryogenic slurries can be formed from a single material in both solid and liquid forms. Alternatively, cryogenic slurries can be formed from a mixture of different materials (at least one and optionally all at cryogenic temperatures). For example, a cryogenic slurry can be formed from solid neon and liquid neon. In another example, a cryogenic slurry can be formed from a first liquid and different solids (such as solid neon and liquid hydrogen). The selected materials can be adapted to improve flow and / or temperature characteristics. For example, the (initially) solid material can be the first material chosen to maintain cooling, while the liquid can be chosen to facilitate addition and replacement in an internal reservoir. The selection of materials for the slurry can improve cooling and / or transport performance. In some cases, the slurry may be referred to as a mixture of small solid particles in a slurry or liquid (e.g., particles may be smaller than about 100 mm, 50 mm, 20 mm, 10 mm, 5 mm, or 2 mm, but other sizes may be used in some cases). The slurry can act as a solid-liquid two-phase fluid.

[0039] Known means of generating cryogenic slurry include repeated freeze-thaw operations, spraying, and the use of an auger. The auger is most common for large-scale production. In some cases, the slurry may be supplied by an external provider. An external reservoir may include or be connected to the cryogenic slurry generating apparatus. This apparatus may include a refrigerant source, such as one or more coolers and augers. Using an external reservoir 11 to create and store cryogenic slurry means that the weight and complexity of the magnet can be reduced. The external reservoir 11 also allows for the cooling of currently unused portions (one or more) of the cryogenic slurry while the magnet is in use. Although a single reservoir 11 is considered, in practice, separate discardable reservoirs or annular arrangements can be used, in which the slurry is recooled between leaving and returning to the magnet.

[0040] The system can use closed-loop processing for recooling the slurry. For example, a portion of the slurry removed from magnet 12 can be cooled while the magnet is in operation, and then returned to magnet 12 in the next stage. Closed-loop processing reduces potential waste in the system and minimizes the amount of slurry required. In some cases, external reservoir 11 can hold a larger amount of slurry to increase the available time for recooling the removed slurry before it needs to be returned to magnet 12. Except at the connection to the internal reservoir of magnet 12, the system can be closed to prevent any contamination or loss of the slurry.

[0041] Figure 1A first system 10 is shown, comprising a refrigerant reservoir or external reservoir 11 and a magnet 12 having an internal reservoir 17. A conduit 13 between the external reservoir 11 and the internal reservoir 17 allows refrigerant to flow between the external reservoir 11 (or external reservoir) and the internal reservoir 17. A pump 19 may be arranged on the conduit 13 to assist refrigerant movement. A valve 15 may be used to close the conduit 13. The valve 15 or an additional or alternative connector 16 may also disconnect from the conduit 13 so that the magnet 12 can be moved relative to the refrigerant reservoir 11. The connector 16 may be reversibly connected to allow the magnet to be released, moved, and reconnected. The magnet or other object may have a docking station 18 to allow the magnet to be positioned relative to (one or more) the conduit 13 or connector 16. The magnet is shown inside a housing such as a pressure vessel 40. The controller 41 can be configured to receive input from one or more sensors and control the operation of any or more of the pump 19, valve 15, connector 16 or magnet 12 or other devices.

[0042] In the first example, a method for maintaining the temperature of magnet 12 is described. First, magnet 12 is cooled to its operating temperature. The operating temperature can refer to a set temperature or a temperature range. This cooling can be achieved by an external cooling device, by flowing refrigerant through a reservoir, or by any suitable method of cooling magnet 12. The proposed cryogenic slurry method can also be used to cool magnet 12; however, since magnet 12 does not need to be moved during the cooling phase, cooling with different methods may be easier or more efficient.

[0043] Once magnet 12 has been cooled to its operating temperature, a first portion of cryogenic slurry can be added to internal reservoir 17. This first portion is used to maintain the temperature of magnet 12 at its operating temperature. In some cases, the method attempts to do so for as long as possible to increase the time the magnet can be operated. While the first portion of cryogenic slurry is in internal reservoir 17, it is monitored to determine the molten portion. By monitoring the molten portion of the slurry, the remaining time the slurry can maintain its temperature or the remaining solids are monitored. The method can account for the time required to replace the cryogenic slurry in the calculations to begin replacement earlier and avoid temperature drops. This intermittent change of the slurry allows for sufficient maintenance of the magnet's temperature to provide a long uptime, while ensuring that the slurry temperature remains constant and / or the magnet temperature does not exceed operating requirements.

[0044] Any suitable means for monitoring the amount of melting in the first part can be used. For example, a time period can be used. This time period can be predetermined to allow for estimation of the melting of the cryogenic slurry in the portion. In one example, this time period depends on temperature measurements. For example, temperature measurements of magnet 12 and / or internal reservoir 17 can be used to adjust the time period. In some cases, the temperature can be tracked within this time period, and historical temperatures can be used to adjust the time period. In another example, the temperature of the cryogenic slurry can be used to determine the amount that has melted in the first part. During the phase transition, the temperature should remain approximately constant. However, as the phase transition completes, the temperature will begin to rise. The amount of melting in the first part can be monitored by monitoring the temperature and determining the temperature rise. In another example, the amount of melting can be sensed or determined electrically or mechanically, for example, by determining the density of the amount or size of particles in the cryogenic slurry. In another example, the method can determine the amount of solid or liquid in the slurry, for example, by monitoring the properties of the slurry, such as temperature, conductivity, or density. Predefined thresholds can be used such that slurry replacement is initiated once time or slurry exceeds the threshold. If replacement is not required immediately, a threshold can be set to provide the time needed to replace the slurry.

[0045] Predictive systems can be used to determine the amount of melting in the first phase, the time to phase transition, or the time interval between slurry exchange. For example, machine learning or artificial intelligence systems can be trained. Training can be performed on a test system with additional sensors to determine the characteristics of the slurry. Characteristics can be determined under multiple conditions. Conditions can represent magnet operation, environmental conditions, plasma operation, and / or environmental conditions. The trained machine learning or artificial intelligence system can then be used to predict the state of the slurry or the time interval until slurry melting based on one or more characteristics of the slurry in use. For example, a machine learning system can use temperature readings from the magnet and one or more electrical characteristics of the system to determine the amount of melting. Another example is using the measured energy output of the fusion reaction to estimate the heat load from neutron production deposited into the magnet, and thereby estimate the amount of melting. Machine learning systems can use neural networks, classification, regression, clustering, reinforcement learning, decision trees, Kalman filters, or other techniques.

[0046] In one example, the predictive model (e.g., a machine learning model) will monitor heat loss. Several ways heat energy can be lost in a system. For example, ohmic loss (i^2 × R) is typically dominant. Additional real-time measurements can improve the model's accuracy. Possible measurements include one or more of the following: magnet current, flux pump duty cycle and reapplied current, support system current (e.g., electronics, batteries, etc.), temperature of the magnetic assembly, temperature and pressure of the cooling slurry, volumetric flow rate of the slurry (if dynamically pumped through the system), and surface temperature of the cooler. The model can be trained to maximize magnet uptime (or minimize magnet downtime) and / or plasma duration. Alternatively or in combination, the model can be trained to minimize performance degradation (i.e., maintaining the desired operating temperature).

[0047] In one example, a machine learning approach is used to monitor and maintain the thermal performance of a cryogenic system. This approach may include receiving multiple real-time measurements from one or more sensors associated with the cryogenic system. In some cases, the measurements include one or more of the following: magnet current, flux pump duty cycle, support system current, magnetic assembly temperature, coolant temperature and pressure, coolant volumetric flow rate, and cooler surface temperature. The measurements can be processed by a thermal system model. The thermal system model can be configured to represent heat generation and dissipation within the cryogenic system. The thermal system model may account for heat losses, including one or more of the following: ohmic losses, hysteresis losses, eddy current losses, and heat conduction through structural components. Based on the thermal system model and / or the measurements, the system may, for example, use an extended Kalman filter (EKF) to estimate the internal state of the cryogenic system. The internal state may include one or more of the following: the phase change state of the coolant, the remaining solids fraction of the slurry, the thermal load on the magnetic assembly, and the estimated time until the phase change is complete.

[0048] Machine learning methods, such as Kalman filters, can predict the evolution of the internal state based on a thermal system model and received measurements. These methods can further refine the internal state estimate by updating the predicted internal state based on a comparison between the predicted measurements derived from the thermal system model and the received measurements. Multiple historical operational datasets collected under varying environmental and operating conditions can be used to train the machine learning method. Training may include mapping the relationships between received measurements, thermal system model parameters, and corresponding internal state variables. Training may also include adjusting the covariance matrices of processed noise and measurement noise to improve the accuracy of the machine learning method under real-time operating conditions.

[0049] After training, machine learning methods can be deployed to the magnet or system to provide real-time predictions of the thermal state of the cryogenic system. These predictions can be used to control the replacement of the cooling slurry and / or optimize the thermal performance of the cryogenic system. Machine learning methods can be deployed in a fixed state or can be trained continuously based on results during deployment. In some cases, the machine learning method provides control signals to one or more actuators. These control signals can be based on the estimated internal state of the slurry. Control signals may include commands for dynamically adjusting one or more of the slurry volumetric flow rate, pump duty cycle, and slurry replacement timing. Control signals can be generated to maintain the thermal performance of the magnet / cryogenic system without requiring direct measurement of all system variables. In some cases, machine learning methods enable the continued operation of the cryogenic system during periods of sensor performance degradation or data loss by relying on predictive capabilities derived from a thermal system model and previously trained relationships.

[0050] The system can determine the threshold portion or percentage of the slurry that has become liquid. The state of the cryogenic slurry can be monitored continuously or periodically. Monitoring the cryogenic slurry allows for the determination of the optimal time to replace it. This can be a balance between the remaining solids in the slurry and the time required for replacement. By changing the slurry before all solids have disappeared, the slurry temperature is maintained due to the latent heat during the phase transition, thus improving thermal properties. Using this monitoring of the solid-liquid ratio can prevent operational interruptions by ensuring that the slurry is replaced before magnet heating occurs and / or ensuring that it is not replaced before a significant fraction of the slurry has melted.

[0051] Once a predetermined portion of the cryogenic slurry in the first part has melted, the first part is replaced with fresh cryogenic slurry in the second part (e.g., recooled or containing a solid refrigerant portion above a certain threshold). While the first part could be easily recooled, this would take additional time. Therefore, replacing the first part with the second part is advantageous. The removed first part can then be recooled while the second part maintains the temperature of magnet 12. Alternatively, the removed first part can be discarded and replaced with fresh cryogenic slurry. In some cases, replacing the cryogenic slurry in the first part involves removing a portion of the cryogenic slurry in the first part and replacing it. For example, the liquid portion of the cryogenic slurry can be removed and replaced with another solid cryogenic material, thereby replacing the slurry in the first part with the second part and refreshing the cooling effect.

[0052] Slurry replacement has been described using slurry as a pump. However, one or more containers can be used. When using containers, an internal reservoir may refer to an internal space configured to receive the slurry, such as an internal compartment. Containers may flow into or fit into an internal reservoir, for example, via a mechanical latch or fastening device. Containers may form slurry pools. Interchangeability of slurry pools allows for rapid slurry replacement and / or reduces the possibility of contamination and minimizes liquid management. Containers may have substantially the same shape, allowing them to be easily interchanged. For example, containers may be substantially spherical or cuboid. Alternatively, containers may have a range of shapes. These shapes may be configured to engage with matching recesses in magnet 12. This allows for full utilization of available space in magnet 12 and / or ensures proper cooling in specific areas of magnet 12. Containers may include an outer wall surrounding the slurry reservoir. The outer wall may be configured to enhance heat transfer to the slurry. Containers may include one or more sensors to monitor the properties of the slurry within the container. The system can be configured to receive these characteristics and determine whether container (or all containers) needs to be replaced. Containers may have standardized thermal interfaces for connecting magnets or for refilling (replacing) the slurry within the container after use. Containers may include inlets to allow for the removal and replacement of slurry, or the slurry may be recooled within the container. Containers may be relatively small in size relative to the internal reservoir to allow containers to be pushed in and / or passed through the internal reservoir for slurry replacement.

[0053] Figure 4 The use of container 41 is illustrated. A superconducting magnet 12 is located within a pressure vessel 40. A docking station 18 is shown connected to the magnet 12 and an internal reservoir or compartment. Two containers 41 are inserted into the magnet 12. Containers 41 can be placed in recesses within the magnet 12. Containers 41 can be secured in place, for example, by one or more locks or clamps, or the shape of the containers can allow for a wedge fit or friction fit. Containers 41 may have a thermal interface to engage the internal reservoir 17. An external reservoir 11 is used for recooling or refilling containers 41. Containers 41 may have a thermal interface to facilitate this process. Containers 41 can have different shapes or sizes, such as containers 42, 43, etc. This may require and / or ensure that the containers are placed in the desired position. Different shapes may include one or more recesses and / or bonding portions to restrict engagement within the internal reservoir 17. Containers may be shaped to mate with specific recesses of the internal reservoir.

[0054] The melting of cryogenic slurry provides sufficient cooling time for the superconducting magnet 12 without the need for permanent connection to, for example, the superconducting magnet 12. By monitoring and estimating the amount of solids remaining (or corresponding characteristics) in the slurry, this method can determine when to replace the first portion of the slurry with a fresh portion to maintain temperature while reducing, for example, magnet downtime. The use of slurry improves the ability to move refrigerant between the external reservoir 11 and the internal reservoir 17. The use of slurry also provides a constant temperature. This is beneficial for maintaining the temperature of the superconducting magnet without the need for adjustment or control of fluctuating temperatures.

[0055] Figure 1 A single connection is shown between the external reservoir 11 and the internal reservoir 17 via conduit 13. A pump 19 or other actuator may be configured to add and remove slurry relative to the internal reservoir 17 or between the external reservoir 11 and the internal reservoir 17. The pump 19 may be permanently connected to the external reservoir 11 or the conduit 13 (e.g., a pipe or tube).

[0056] Figure 2 A second example is shown where the internal reservoir 17 is formed as a passage 21, where the passage 21 can be a loop or a circuit. The passage 21 has an inlet 22 and an outlet 23. The inlet 22 and outlet 23 can be connected to allow simultaneous filling and emptying of the internal reservoir. The connector 16 can be repeatedly connected to allow for multiple connection and disconnection. Figure 1 Similarly, outlet 23 can be connected to an external reservoir or waste outlet. Pump 19 can be used to move refrigerant slurry through passage 21. Each of the two conduits 25, 26 can have one or more of a valve 15 and a disconnect point 16 to allow magnet 12 to move and / or prevent or allow refrigerant flow through passage 21. For thermal performance, conduits 25, 26 can be insulated. Reserve reservoir 29 can be used to store discharged refrigerant before returning it to external reservoir 11.

[0057] The passage 21 may be tortuous or configured to provide cooling in a specific region of the superconducting magnet 12. In another example, the passage may be generally straight or a constant curve to improve the addition and removal of slurry. The passage may follow the superconducting material (e.g., a ring or coil) within the magnet 12 or be arranged near the superconducting material. Inlet 22 and outlet 23 may be located at opposite ends of the superconducting magnet 12. In some cases, both inlet 22 and outlet 23 are positioned on the lower or bottom surface of the magnet 12 to allow for easy connection when the magnet is lowered to the ground. The weight of the magnet 12 may be used to open the inlet 22 and outlet 23 of the passage 21 or to connect the inlet 22 and outlet 23 of the passage 21 to the corresponding conduits. The shape and design of the passage 21 forming the internal reservoir 17 ( Figure 2The passage shown as 21) can be configured to allow improved cooling of the magnet.

[0058] For example, the passage may have one or more fins or restraints. The fins may protrude into or outside the internal reservoirs 17, 21. For example, fins protruding into the reservoir can improve heat transfer to the components of the magnet 12. The fins or protrusions may be formed of a conductor, such as copper for electrically connecting superconductors, or steel for supporting the shape of the superconductor. Alternatively or in combination, the fins or passages may extend from the reservoirs 17, 21 to reach specific components or features within the magnet 12 to provide directional cooling. However, in these cases, the discharge or removal of refrigerant may need to be considered. The shape and position of the fins may position them near the hottest part of the magnet 12, or where cooling is most needed. Alternatively, the passage 21 (forming the internal reservoir 17) may be configured to be as wide as possible to allow for the most efficient or rapid addition and removal of refrigerant slurry.

[0059] In some cases, magnet 12 may have one or more additional cooling systems. These additional cooling systems may be configured to improve the performance of the cryogenic slurry and / or optimize performance according to the operation of the magnet. For example, one or more heaters or coolers may be placed around the internal reservoir 17. These can be used to control the state of the slurry (i.e., increasing the time before melting or melting faster to allow for replacement). These heaters / coolers may be electric. In some cases, additional phase change material may be located within the superconducting magnet, such as in the internal reservoir. The phase change material may be cooled by the slurry. The phase change material then provides cooling (or maintains the desired temperature) during slurry replacement. In some cases, the system may control the use of the additional cooling system for operational performance. For example, the additional cooling system may be activated only in the event of a temperature spike.

[0060] In some cases, the magnet incorporates auxiliary phase change materials. These materials can include solid-to-liquid, liquid-to-gas, or solid-to-gas phase change materials (PCMs). PCMs are configured to provide thermal buffering capabilities during events of transient temperature shifts. For example, they help maintain a desired temperature when there are unexpected changes in the temperature of the slurry or magnet. PCMs are not intended to be used as the primary cooling mechanism (the primary cooling mechanism is cryogenic slurry), but rather to act as temporary heat reservoirs to mitigate thermal spikes during specific operating scenarios. One example is when the cryogenic slurry has completely transformed into a liquid. The PCM is configured to undergo a phase change (melting) at a predetermined temperature. This predetermined temperature is higher than the temperature of the slurry in the internal reservoir.

[0061] In some cases, the PCM can be strategically positioned within the thermal management system of the magnet to act as a local heat sink. The latent heat absorption during the phase transition when the PCM's melting point is reached provides a critical time buffer, allowing the system to transition from active operation to a safe shutdown, or allowing the system to refill its internal reservoir with a new portion of cryogenic slurry. This buffering capability is particularly advantageous during periods of high demand or when the system experiences transient thermal loads exceeding the cooling capacity of the remaining liquid coolant.

[0062] The use of PCM can also be integrated with real-time temperature and pressure monitoring to dynamically assess the thermal state of the system. This can be combined with the predictive modeling discussed earlier. Sensors located near the PCM module and throughout the magnet assembly can detect the onset of a phase transition in the PCM. These measurements can be used to warn the system of an impending thermal shift and initiate preemptive actions. Example preemptive actions include inducing a refill operation or temporarily reducing the system's thermal load.

[0063] In some cases, heaters can be used as an auxiliary system to address stratification issues within cryogenic slurries. If solid material in the slurry accumulates in localized areas (e.g., due to gravity or fluid dynamics), the heater can be selectively activated to remelt or redistribute the solid phase. This ensures slurry homogeneity and maintains optimal heat transfer characteristics. The heater can be activated based on data from temperature and pressure sensors or other sensors that can detect changes indicative of stratification. In some cases, predictive models combining known thermodynamic and hydrodynamic properties of the slurry can anticipate potential solid accumulation zones and preemptively activate the heater.

[0064] Integrating either or both of the PCM-based thermal buffer and stratified control heaters can enhance system robustness by minimizing temperature spikes during transitions and ensuring consistent cooling performance.

[0065] In some cases, the second portion of the slurry is used to advance, push, or facilitate the removal of the first portion. This allows for the simultaneous addition and removal of slurry. Because the fresh slurry has a higher solids content (i.e., density), the second portion may be able to displace the first portion. This can increase the replacement rate of the cryogenic slurry due to the simultaneous addition and removal of portions. In another example, the system may have two pumps 19, one for removing the first portion and the second for adding the second portion. The pumps 19 may be connected to separate conduits. Alternatively, the second portion can be used to push the first portion out of the superconducting magnet 12.

[0066] The internal reservoir 17 may include one or more pumps 27, or include means configured to circulate the slurry within the internal reservoir 17. This allows for a circulation step to improve or make the refrigerant diffusion within the magnet 12 more constant. This can occur even when the magnet 12 is moving and / or levitating. In some cases, a passive pump may be used alternatively. Pump 27 may circulate the refrigerant within the internal reservoir or along connecting passages within the internal reservoir. The internal reservoir may have one or more valves to allow the connecting passages to be opened and closed, for example, during refrigerant replacement.

[0067] Passive pumps or systems can be driven by gravity or the movement of magnets to facilitate the movement of slurry to a specific area. In some cases, slurry can be added to facilitate movement. For example, the liquid portion can be added separately to the solid portion, such that the liquid portion then moves into the solid portion over time. Alternatively, the internal reservoir can be configured to allow the solid and liquid portions of the slurry to settle at different locations. In another example, as the slurry becomes more liquid, it may be able to pass through narrow openings into different sections of the internal reservoir.

[0068] Figure 3 An example loop method is shown. A cryogenic slurry is created 31 outside the object to be maintained at a certain temperature. A portion of the slurry (which may be the entire amount of slurry produced) is transferred 32 to the object's internal reservoir. The object is operated, and 33 the slurry status is monitored to determine the amount of solids, liquid, or remaining time. For example, if the solids percentage has dropped 34 below a threshold, or is estimated to have dropped below a threshold, the cryogenic slurry is removed from the internal reservoir 35 and replaced with fresh cryogenic slurry. This may require pausing the operation of the object. For example, the object may return to ( Figure 1 (As shown) docking station 18 or similar. Cryogenic slurry can be recycled back to external reservoir 11 when removed from internal reservoir 17 35, or fresh portions of cryogenic slurry can be created 31.

[0069] To maintain a constant temperature, the cryogenic slurry can be circulated regularly. This could mean dozens or hundreds of cycles to allow, for example, magnet 12 to operate in a superconducting state while in a hot chamber. Because the downtime of magnet 12 is reduced (due to the rapid exchange of slurry), magnet 12 can be repeatedly reloaded without major interruptions to operation. In normal operation, magnet 12 is cooled to the desired temperature, cryogenic slurry is added, magnet 12 is levitated and operated until the slurry has melted to a threshold amount, then the magnet is landed and the cryogenic slurry is replaced. Magnet 12 is then re-levitated and returned to operation. The cycles of landing, replacing the cryogenic slurry in the magnet, and levitating magnet 12 can then be repeated as needed. In the case of a levitated dipole, operating magnet 12 involves levitating magnet 12 to the operating position and generating a current in the superconducting coil to confine the plasma within the generated dipole field. If the object is not magnet 12, the movement of the object may not be levitated. Docking station 18 or guide can be used to ensure that the magnet or object returns to the proper position and / or orientation. For example, the guide can be a protrusion. The protrusion can have one or more tracks or fins that mate or engage with corresponding recesses on the magnet to guide it into place (or vice versa).

[0070] In the case of using magnet 12, and in other cases, the advantage of the system is that it allows the refrigerant to be stored or manufactured outside of magnet 12. For example, a levitation dipole magnet is typically a pressure vessel container, a superconducting ring, or a coil. Magnet 12 is then placed inside a large pressure vessel 40 to contain plasma. The system will allow the external reservoir 11 and pump 19 to be located outside both pressure vessels, and only the internal reservoir needs to be inside the magnet. This allows for easier handling and maintenance of the refrigerant and pump, and reduces the load on magnet 12. Although Figure 1 The connection is shown on the side of the pressure vessel 40, but it can usually be on the bottom to allow for easier orientation and connection.

[0071] The system may have a controller 41. The controller may be configured (e.g., via one or more sensors) to determine the thermal state of the cryogenic slurry in the internal reservoir 17 and to control pumps 19 to replace the cryogenic slurry in the internal reservoir 17 (or to control multiple pumps 19 to remove and replace the cryogenic slurry). The controller 41 may also control or signal other devices to perform any of the steps described herein. For example, the controller may monitor or adjust valves and / or connectors 16.

[0072] This system can be pumped using a fixed flow rate, or with a fixed pumping pressure or power. However, the system can dynamically control a pump with a variable flow rate. Proper control can be important due to the changing state of the cryogenic slurry (i.e., the liquid / solid fraction). For example, the system can use one or more characteristics of the cryogenic slurry and / or one or more characteristics of the system to determine the appropriate flow rate when replacing the slurry. For example, the state of the slurry can be determined. If the slurry has a larger liquid fraction, the flow rate can be increased because this will allow it to flow more quickly from the internal reservoir. For example, slurry separation can be determined, and the flow rate can be controlled to prevent slurry separation (liquid rising above the solid). For example, the system can use characteristics of a magnet or the environment to determine the state of the slurry. The temperature of the magnet or the temperature around the magnet (e.g., plasma temperature or fusion energy) can be used to estimate the slurry state and / or directly to determine the appropriate flow rate.

[0073] Flow rate control can be determined by considering at least the system's Δ pressure (i.e., the Δ pressure of the internal reservoir or the internal / external reservoir). Δ pressure can be understood as the resistance to slurry flow through the system (e.g., the internal reservoir). The higher the viscosity of the slurry (up to being entirely solid), the more difficult it is to pump it into the internal reservoir. This results in greater force required to move the slurry and a corresponding higher Δ pressure, especially when moving the slurry at a higher flow rate. The higher Δ pressure (and consequently higher system pressure) adds mechanical strain to the system due to the increased load. Therefore, the controller can balance one or more of the following: Δ pressure, flow rate requirement, system threshold, and slurry viscosity and / or state.

[0074] The thermal parameters of flow rate depend on the local convection rate at the slurry boundary and the source of the heat flux (i.e., the walls of the internal reservoir). A higher flow rate results in a higher heat transfer coefficient (Δtemperature) between these characteristics because the slurry maintains a constant temperature. During slurry exchange, the heat transfer coefficient should be selected or controlled below a threshold (e.g., through dynamic flow rate). Insufficient heat transfer may cause component temperatures to rise or magnet downtime to increase. Excessive heat transfer and thermal strain issues may lead to mechanical stress or exceed threshold limits. The determination of the flow rate can vary because the viscosity of the slurry may change during use (due to a decrease in the ice mixing fraction). For example, the Δpressure limit may decrease, and the available thermal energy storage will also decrease. This may lead to an increase in flow rate, and the slurry will also be easier to pump. Understanding the state of the slurry (predicted or measured) allows for flow rate control to balance mechanical thresholds with performance. This can be determined by parameters such as Δpressure (which may alternatively be measured as other parameters). For example, a controller can control the flow rate to provide the desired heat flux to the magnet while ensuring that the Δpressure remains below the system threshold. The desired heat flux can be ranged to provide flexibility in the flow rate.

[0075] The system can monitor slurry stratification. Preventing stratification ensures that the desired temperature is maintained on the magnet. Stratification control can be achieved by controlling the pump to ensure the slurry is evenly distributed throughout the system. Stratification can also be controlled by mixing. For example, by pumping the slurry into and / or out of an external reservoir where fluid enters at the bottom and exits from the top (or vice versa, for example, depending on density). In some cases, stratification can be altered using additional inlets or flow paths within an internal reservoir. A mixer may also be present in the reservoir to cause stratification of the slurry within the internal reservoir.

[0076] In some cases, stratification is advantageous (i.e., the slurry lacks homogeneity). In neon slurries, solids will form below the liquid (however, this may be the opposite when using alternative slurry materials). In one example, a modular slurry container is used. The container can begin as a solid block inserted into the system (thus eliminating the need for pumping material). This means it requires no flow path or openings during use. As the solid cryogenic material melts, the liquid will rise to the top (or alternatively, sink to the bottom, depending on density). This brings additional solids to the top of the container. If the thermal interface is located at the top of the container, the solid slurry is held closer to the thermal interface to enhance cooling.

[0077] In some cases, outlet 23 can be positioned or shaped to facilitate liquid outflow, so that once melted, the liquid portion of the cryogenic slurry can be easily removed while retaining any remaining solids, and a replacement second portion can be added.

[0078] The previously described examples have focused on a suspended dipole magnet 12 that needs to be cooled to cryogenic temperatures for superconductivity. However, the system and method can be applied to other systems where maintaining the operating temperature is advantageous. Unique advantages may exist where the system and method do not require continuous pumping of the refrigerant, especially in cases where the object to be kept at cryogenic temperatures is movable or needs to be detached from the refrigerant reservoir. The method can also be applied to other applications where limiting downtime for cooling is important. Examples include magnetic systems that need to operate at constant temperatures without direct connection to the cooling loop during operation; electric aircraft motors that need to maintain constant temperatures during flight but desire short downtime to minimize waiting time on the ground; and satellites that periodically dock with support stations. For example, a satellite may have a limited time to dock with a support station before rejoining its orbit. By rapidly replacing the onboard cryogenic slurry, sufficient cooling can be provided while reducing downtime. In these examples, the internal reservoir can be within an alternative container (i.e., without the magnet). Magnet- or fusion-specific features can be replaced by alternative applications.

[0079] For example, this system can be applied to MRI (Magnetic Resonance Imaging) systems to reduce the amount of helium required. MRI machines typically use superconductors that require liquid helium for cooling. This system can allow for a reduction in the amount of superconductor and minimize system complexity, or at least prevent the requirement for continuous operation of the system. The internal reservoir allows the system to be disconnected from the slurry source, which allows the MRI (or other medical device) to be transported while maintaining the required temperature. In these applications, the uptime / downtime of the device (container / magnet) can be much longer than in the system described, because thermal heating is reduced compared to the fusion reactor example discussed above. This system can also be applied to quantum computing and / or supercomputing cooling. In quantum computing, the operating principle relies on superconducting materials and has a near-zero heat distribution to reduce vibration. Although dilution cooling (a mixture of He3 and He4) is used, this heat still needs to be removed. Previously, liquid helium cryogenic coolers in static condensation devices have been used. In some cases, this system can provide an operational buffer for He3 / He4 systems. The system can outperform liquid helium in managing transients and maintaining temperature consistency. This system may be particularly advantageous for cooling portable devices where continuous cooling is not possible; therefore, the described intermittent cooling allows for operation at low temperatures and reduces downtime for refilling.

[0080] The aforementioned aspects of the controller and method can be operated or implemented on any type of dedicated or special computer, or any machine or computer or server or electronic device having a microprocessor, processor, microcontroller, or programmable controller, or a cloud-based platform or other network (whether local or remote) of the processor and / or server, or any combination of such devices.

[0081] The controller described in conjunction with the examples disclosed herein can be implemented or performed using: a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic components; discrete gate or transistor logic; discrete hardware components; or any combination thereof designed to perform the functions described herein. The general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, circuit, and / or state machine. The processor may also be implemented as a combination of computing components (e.g., a combination of a DSP and a microprocessor), multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0082] The methods or algorithms described in conjunction with the examples disclosed herein can be embodied directly in hardware, processor-executable software modules, or a combination of both, in the form of processing units, programming instructions, or other means, and can be contained in a single device or distributed across multiple devices. Software modules can reside in storage media such as RAM, flash memory, ROM, EPROM, EEPROM, registers, hard disks, removable disks, CD-ROMs, or any other form of storage media known in the art. The storage medium can be coupled to the processor, enabling the processor to read information from and write information to the storage medium. Alternatively, the storage medium can be integrated with the processor.

[0083] In various aspects, embodiments of this disclosure may be embodied in computer-implemented processes, machines (such as electronic devices, or general-purpose computers, or other devices that provide a platform for executing computer programs), processes performed by such machines, or articles of art. Such articles of art may include computer program products or digital information products, wherein a computer-readable storage medium contains computer program instructions or computer-readable data stored thereon, and processes and machines for creating and using the articles of art.

Claims

1. A method for maintaining the temperature of a superconducting magnet, wherein the superconducting magnet includes an internal storage device, the method comprising the steps of: The first portion of the cryogenic slurry is added to the internal reservoir; It has been determined that the first portion has at least partially melted; Replace the first part of the cryogenic slurry with the second part of the cryogenic slurry.

2. The method of claim 1, wherein the cryogenic slurry comprises one or more of nitrogen, neon, and hydrogen.

3. The method according to claim 1 or 2, wherein the cryogenic slurry comprises a liquid and a solid of the same material.

4. The method according to any one of claims 1 to 3, wherein the first portion of cryogenic slurry and the second portion of cryogenic slurry are obtained from an external reservoir.

5. The method of claim 4, wherein the first portion and the second portion are obtained from the same external storage.

6. The method according to claim 4 or 5, wherein the external reservoir comprises a slurry generating device.

7. The method according to any one of claims 4 to 6, comprising the steps of connecting and / or disconnecting the internal storage to the external storage.

8. The method of claim 7, wherein the internal storage and the external storage are disconnected during operation of the superconducting magnet and reconnected between operational events of the superconducting magnet.

9. The method according to any one of claims 1 to 8, comprising simultaneously removing the first portion of cryogenic slurry while adding the second portion of cryogenic slurry.

10. The method according to any one of claims 1 to 9, wherein the second portion is used to advance the removal of the first portion.

11. The method according to any one of claims 1 to 10, wherein determining that the first portion has at least partially melted includes determining that the solid portion has dropped below a preset threshold.

12. The method according to any one of claims 1 to 11, wherein determining that the first portion has at least partially melted includes monitoring one or more of time and temperature.

13. The method according to any one of claims 1 to 12, wherein determining that the first portion has at least partially melted includes monitoring the portion of the cryogenic slurry that has become liquid.

14. The method according to any one of claims 1 to 13, wherein the first portion is replaced when the threshold portion of the slurry has become liquid.

15. The method according to any one of claims 1 to 14, comprising the step of circulating a portion of the cryogenic slurry within the internal reservoir.

16. The method according to any one of claims 1 to 15, comprising the step of cooling the superconducting magnet to the operating temperature before adding the first portion of the cryogenic slurry.

17. The method according to any one of claims 1 to 16, comprising the step of repeatedly adding and replacing additional portions of the cryogenic slurry.

18. The method according to any one of claims 1 to 17, comprising operating the superconducting magnet between the step of adding the cryogenic slurry to the internal reservoir and the step of replacing the cryogenic slurry in the internal reservoir.

19. The method of claim 18, wherein operating the superconducting magnet comprises one or more of the following: Changing the position of the superconducting magnet, and An electric current is applied to the superconducting magnet.

20. The method of claim 19, wherein changing the position of the superconducting magnet comprises suspending the superconducting magnet.

21. A system for maintaining the temperature of a superconducting magnet, wherein the superconducting magnet includes an internal storage device, the system comprising: External storage container for holding cryogenic slurry; A pump for moving a portion of the cryogenic slurry into the internal reservoir; The controller is configured as follows: Determine the thermal state of the cryogenic slurry in the first portion of the internal reservoir; as well as The pump is controlled to replace the first portion of the cryogenic slurry with the second portion of the cryogenic slurry based on the determination.

22. The system of claim 21, wherein the external storage device is reusable to the internal storage device.

23. The system of claim 21 or 22, wherein the internal storage includes a path extending between an inlet and an outlet.

24. The system of claim 23, wherein the pump is configured to pump the first portion and the second portion through the inlet to the internal reservoir and pump them out of the outlet.

25. The system of claim 24, wherein the pump is configured to pump the first portion and the second portion synchronously.

26. The system of claim 24 or 25, wherein the inlet and the outlet are each reusable to the external storage device.

27. The system according to any one of claims 21 to 26, wherein the external reservoir includes a cryogenic generator for generating the cryogenic slurry and cooling the cryogenic slurry, or one or more of the cryogenic generator.

28. The system according to any one of claims 21 to 27, wherein the superconducting magnet is movable, and optionally wherein the system includes a docking station for positioning and / or orienting the superconducting magnet when replacing the cryogenic slurry.

29. The system of claim 28, wherein the superconducting magnet includes a guide configured to guide the position of the superconducting magnet to and from the docking station.

30. The system according to any one of claims 21 to 29, wherein the superconducting magnet is a levitation magnet.

31. The system of claim 30, wherein the superconducting magnet is housed within a pressure vessel, and the external reservoir is located outside the pressure vessel.

32. The system according to any one of claims 21 to 31, wherein the internal reservoir comprises one or more fins, the one or more fins being configured to improve the thermal conductivity of the cryogenic slurry.

33. The system of claim 32, wherein the fins extend into the internal reservoir.

34. The system according to any one of claims 21 to 33, wherein the internal reservoir includes a pump to move the cryogenic slurry about the internal reservoir.

35. The system according to any one of claims 21 to 34, wherein the internal reservoir includes a passive thermal system configured to enhance heat transfer to the cryogenic slurry.

36. The system of claim 35, wherein the passive thermal system is driven by gravity and / or the movement of the superconducting magnet.

37. The system of claim 35 or 36, wherein the passive heating system allows the solid refrigerant in the slurry to settle at a first position and allows the liquid portion of the slurry to settle at a second position.

38. The system according to any one of claims 21 to 37, wherein the external storage device and / or the connector between the external storage device and the internal storage device is thermally insulated.

39. A method for maintaining the temperature of an object, wherein the object includes an internal storage device, the method comprising the steps of: Add the first portion of coolant slurry to the internal reservoir; It has been determined that the first portion has at least partially melted; Replace the first part of the coolant slurry with the second part of the coolant slurry.

40. The method of claim 39, comprising any one or more of the steps of the method of claims 1 to 20.

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