1. Field of the Disclosure
The disclosure relates to circuits, systems, and methods, and more particularly to circuits including superconducting elements and switches, systems including the circuits, and methods of using the systems.
2. Description of the Related Art
When the superconducting coils 124, 126, and 128 are being taken to their specified or desired magnetic field, external power supply terminals (not illustrated) are connected to power supply terminals 142 and 144. The persistent current switch 122 is placed into its higher impedance state, which can be achieved by activating the resistive heating element 1224 to substantially prevent the superconducting element 1222 from reaching a superconducting state. Current flows from one of the external power supply terminals through one of the power supply terminals (142 or 144), through the superconducting coils 124, 126, and 128, through the other of the power supply terminals (142 or 144), and to the other external power supply terminal. After the superconducting coils 124, 126, and 128 reach the specified or desired magnetic field, the persistent current switch is taken to its lower impedance state, which is achieved by deactivating the resistive heating element 1224. As the temperature decreases, the superconducting element 1222 reaches its superconducting state, and the external power supply terminals can then be removed from the power supply terminals 142 and 144. In theory, the superconducting circuit path should be able to sustain current flow and keep the magnetic fields produced by the superconducting coils 124, 126, and 128 into perpetuity. In practice, the current flow and magnetic fields should be able to be maintained for at least a year without having to reconnect the MRI system 100 to the external power source or having to provide additional liquid cryogen.
The persistent current switch 122 can have reliability that is insufficient for the MRI system 100 to reliably operate for long periods of time. Even though the resistive heating element 1224 may remain deactivated, the superconducting element 1222 may not remain in its superconducting state. The superconducting element 1222 becomes resistive when it is not is its superconducting state, and causes current within the superconducting current path 120 to become reduced and produces heat within the vessel 110. If a liquid cryogen is used, the heat can cause substantially all of the liquid cryogen to rapidly boil off. The boiling-off of the liquid cryogen can require recharging of the vessel 110 with expensive liquid cryogen and recooling the system. The presence of a resistance in the superconducting current path will cause the current to decay, thus, causing a reduction in magnetic field.
Many MRI systems, such as the MRI system 100 in
The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings.
The use of the same reference symbols in different drawings indicates similar or identical items. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale.
A switch can be used in conjunction with a superconducting current path to provide a more reliable circuit and system. The switch can be connected in parallel with a portion of the superconducting current path. In one embodiment, the switch may be connected in parallel with an entire superconducting element, such as a persistent current switch, a superconducting coil, or the like, or may be connected in parallel across only a portion of a superconducting element.
A method of using a system can include coupling a first external power supply terminal to a first power supply terminal of the system, coupling a second external power supply terminal to a second power supply terminal of the system, and flowing current through a superconducting element within the system when the first external power supply terminal to the first power supply terminal of the system and the second external power supply terminal to the second power supply terminal of the system. The method can also include placing a persistent current switch of the system into a first lower impedance state, decoupling the first external power supply terminal from the first power supply terminal of the system, decoupling the second external power supply terminal from the second power supply terminal of the system, and placing a first switch of the system into a second lower impedance state.
A few terms are defined or clarified to aid in understanding of the terms as used throughout this specification.
As used herein, a switch is characterized as having a higher impedance state and a lower impedance state. The higher impedance state can be an open circuit or a closed circuit in which resistance or other impedance through the switch is substantially higher than the lower impedance state. The lower impedance state can be a closed circuit in which the resistance or other impedance is substantially lower than the higher impedance state. For example, the higher impedance state of the switch can be at least three orders of magnitude higher in resistance as compared to the lower impedance state of the same switch.
The term “control element,” when referring to a switch, is intended to mean a circuit element or an object that is capable of changing the switch from a lower impedance state to a higher impedance state, from the higher impedance state to the lower impedance state, or both.
The term “faulting state” is intended to mean a state in which a superconducting element along a superconducting current path is not in a superconducting state.
The term “mechanical switch” is intended to mean a switch having a moving part that is used to change the switch from a lower impedance state to a higher impedance state, from the higher impedance state to the lower impedance state, or both. For the purposes of this specification, a mechanical switch can include a knife switch, an electromechanical relay, etc.
The term “persistent current switch” is intended to mean a switch capable of latching into a state and remaining in such state, after power to a control element of the switch is removed.
The term “superconducting” is intended to describe a material capable of achieving a substantially zero resistance at a critical temperature, and can include low-temperature superconductors, high-temperature superconductors, boride-based superconductors, etc.
The term “superconducting current path” is intended to mean a circuit path that is capable of allowing current to flow at nearly zero resistance. A circuit path that includes significantly higher resistance, such as through a non-superconducting portion of a switch when the switch is in a lower impedance state, is not part of a superconducting circuit path.
The term “superconducting element” is intended to mean a circuit element or an object that has substantially zero resistance when in its superconducting state.
The term “typical operating state” is intended to mean a state in which all superconducting elements along a superconducting current path are in their superconducting states.
As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).
Additionally, for clarity purposes and to give a general sense of the scope of the embodiments described herein, the use of the “a” or “an” are employed to describe one or more articles to which “a” or “an” refers. Therefore, the description should be read to include one or at least one whenever “a” or “an” is used, and the singular also includes the plural unless it is clear that the contrary is meant otherwise.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
To the extent not described herein, many details regarding specific materials, processing acts, and components, assemblies, and systems are conventional and may be found in textbooks and other sources within the superconducting, cryogenic, and medical device arts.
While much of the description herein is directed to an MRI system, after reading this specification, skilled artisans will appreciate that the concepts described herein may also be extended to a different system. In another embodiment, the system may include a superconducting element in a different application (e.g., a transmission or distribution cable, a transformer, a fault current limiter, one or more other suitable electronic devices, or any combination thereof). Thus, the systems and methods described herein are not limited only for use with an MRI system.
The system 200 further includes a switch 262 that is connected in parallel with a portion of the superconducting current path 220. In the embodiment as illustrated in
The persistent current switch 222 also has a terminal connected to the node 282 and another terminal connected to the node 284, the power supply terminal 242 is connected to the node 282, and the power supply terminal 244 is connected to the node 284. In one embodiment, the switch 262 includes a current-carrying portion that does not include a superconducting element. Another current-carrying portion of the switch 262 may or may not include a superconducting element, such as a superconducting wire, tape, or solder. A terminal of the superconducting coil 224 is coupled to the node 282, and a terminal of the superconducting coil 228 is coupled to the node 284, and in a particular embodiment, the terminal of the superconducting coil 224 is connected to the node 282, and a terminal of the superconducting coil 228 is connected to the node 284. The superconducting coils 224, 226, and 228 are coupled to each other, and in a particular embodiment, superconducting coil 224 is connected to the superconducting coil 226, which is connected to the superconducting coil 228. In another particular embodiment, a circuit element (not illustrated) may lie (1) between (i) the node 282 and (ii) the power supply terminal 242, the persistent current switch 222, the switch 262, the superconducting coil 224, or any combination thereof, (2) between (i) the node 284 and (ii) the power supply terminal 244, the persistent current switch 222, the switch 262, the superconducting coil 228, or any combination thereof, (3) between each immediately adjacent pair of superconducting coils (224, 226, 228), or any combination of (1), (2), and (3). The circuit element may or may not be a superconducting element.
Attention is now directed to
In one embodiment, a persistent current switch 422, superconducting coils 424, 426, and 428, and nodes 482 and 484 (illustrated by dashed ovals) are disposed within the vessel 410. The persistent current switch 422 can be any of the configurations as described with respect to the persistent current switch 222 in
The switch 462 is designed to be more robust and reliable compared to the persistent current switch 464. In one embodiment, the switch 462 includes a portion that is not a superconducting element, and another portion that may or may not include a superconducting element. In a particular embodiment, the switch 462 is designed to have relatively low impedance, including the resistance and inductance of all elements of the switch 462 and their contact resistance when in its lower impedance state, however, even when in its lower impedance state, the resistance through the switch 462 is significantly higher than zero ohms. In one embodiment, the switch 462 may have a resistance of at least 10−6 Ohms when in its lower impedance state. In another embodiment, any detectible resistance may be considered significant when used with a superconducting element. Therefore, even when the switch 462 is in its lower impedance state, the impedance through the switch 462 can be at least 10 times higher than the impedance through persistent current switch 422 when in its lower impedance state. In a more particular embodiment, the impedance through the switch 462 when in its lower impedance state can be at least 100, 200 or 1000 times higher than the impedance through the persistent current switch 422 when in its lower impedance state.
In one embodiment, the switch 462 comprises a mechanical switch including terminals and a shorting link. In
The connections within the switch 462 may be treated to provide low contact resistance. Such treatments can include polishing, gold plating, CuNi plating, tinning with solders (superconducting, or non-superconducting), another suitable contact resistance lowering treatment, or any combination thereof The connection between the terminals and the shorting link can use relatively smooth interfaces, screw threads, or the like. The shorting link can be straight sided, tapered, or any combination thereof. In yet another embodiment, the switch 462 can have a shorting receptacle that includes the terminals 4622 and 4624. The shorting receptacle and the shorting link (e.g., control element 4626) can be substantially circular, oval, rectangular, or another suitable shape that can be designed a low resistance contact between the shorting receptacle and the shorting link. The shorting link can be one object or a combination of elements that are electrically connected to provide sufficiently low resistance. In still another embodiment, the switch 462 may include a heater that enables hot solder to connect the shorting link to the terminals of the switch, disconnect the shorting link from a terminal of the switch, or both. The heater may be permanently installed or removable.
In another embodiment (not illustrated), the switch 462 can include a shorting link portion and a resistive portion. When the shorting link portion is connected or otherwise active, the switch 462 is in its lower impedance state, as previously described. When the resistive portion is connected or otherwise active, the switch 462 is in its higher impedance state, and as compared to its lower impedance state, the impedance through the switch 462 when in its higher impedance state can be at least 3, 6, or more orders of magnitude higher than the impedance through the switch 462 when in its lower impedance state. In one embodiment, the switch 462 can include a resistive portion that can, for example, be made active without mechanical linking by heating a superconducting element that is part of the switch 462. The external power supply terminals 452 and 454 may or may not be part of the system 400.
The actual location of some of the components can be varied. As illustrated in
As illustrated in
Although not illustrated, the system 400 can include ports (not illustrated) that allow the external power supply terminal 452, the external power supply terminal 454, the control element 4626, or any combination thereof to be inserted through the cover 408 and through a wall of the vessel 410. One or all of the ports may be sealed or otherwise closed during different states. For example, when the system 410 is in its typical operating state, the control element 4626 may extend through its corresponding port, whereas ports corresponding to the power supply terminals 442 and may be sealed or otherwise closed. After reading this specification, skilled artisans will understand how to physically and electrically configure the system 400 to meet their needs or desires.
Attention is now directed to methods of using the systems. The method will be described in
Powering the system can be performed using the actions in
The method can further include flowing current through a superconducting element within the system, at block 722 of
The method can still further include placing the persistent current switch of the system into its lower impedance state, at block 802 in
The method can yet further include decoupling the first external power supply terminal from the first power supply terminal of the system, at block 822 in
The method can also include placing the first switch of the system into its lower impedance state, at block 842 of
The method can further include operating the system, wherein during operating, the persistent current switch changes from a typical operating state to a faulting state, at block 902 of
After the persistent current switch changes from a typical operating state to a faulting state, the method can include flowing current through the first switch when the persistent current switch is in the faulting state, at block 904. Referring to
After the faulting state occurs and current flows through the switch 462, the next action can vary depending on the state of the system 400, nature of the problem, another factor, or any combination thereof. In one embodiment, the system 400 may be taken to substantially zero magnetic field. The method can include re-coupling the first external power supply to the first power supply terminal of the system, at block 922 of
In another embodiment, current can be increased in the superconducting element to place the system in a pre-faulting state. Alternatively, current flowing through the switch 462 can be monitored to determine current flow through the switch 462 as a function of time. The operating data may be used to detect low-level, intermittent problems may be more quickly. For example, the current flow through the switch 462 should be negligible except for when the persistent current switch 422 is in a faulting date. The operating data may indicate that the current flow persistent current switch 422 at the specified or desired level occurs nearly all the time but occasionally varies. By monitoring current through switch 462, a qualified service technician may determine that the connections at the terminals of the persistent current switch 422 should be examined.
Other actions may be performed and may not require the system 400 to be taken to substantially zero magnetic field.
After reading this specification, skilled artisans will appreciate that the concepts described herein are not limited to a particular MRI system, such as a cylindrical MRI system, as illustrated in
After reading this specification, skilled artisans will appreciate that use of a more robust and reliable switch can allow for a longer time period before a system boils off substantially all of its liquid cryogen. The longer time period can allow for a qualified service technician to be dispatched and reach a remote location where the system is located. The qualified service technician can diagnose the system or perform other actions that may prevent quenching, reduce further damage to the system, reduce the amount of liquid cryogen lost, reduce the necessity of taking the system to substantially zero magnetic field, reduce the likelihood of another undesired consequence, or any combination thereof.
Many different aspects and embodiments are possible. Some of those aspects and embodiments are described below. After reading this specification, skilled artisans will appreciate that those aspects and embodiments are only illustrative and do not limit the scope of the present invention.
In a first aspect, a circuit can include a superconducting current path and a first switch having a first terminal and a second terminal. The first switch can be connected in parallel with a portion of the superconducting current path. The first terminal can be connected to the superconducting current path at a first node, and the second terminal is connected to the superconducting current path at a second node, wherein the second node is different from the first node.
In one embodiment of the first aspect, the superconducting current path can include a persistent current switch that includes a first superconducting element. In a particular embodiment, the first superconducting element can have a third terminal and a fourth terminal, wherein the third terminal of the first superconducting element is connected to the first node, and the fourth terminal of the first superconducting element is connected to the second node. In a more particular embodiment, the first switch and the persistent current switch can be configured such that when the first switch would be in a first lower impedance state and the persistent current switch would be in a second lower impedance state, the first switch would have a higher impedance as compared to the persistent current switch.
In another particular embodiment of the first aspect, the superconducting current path can further include a second superconducting element. In a more particular embodiment, a superconducting coil can include a third terminal and a fourth terminal, wherein the third terminal of the superconducting coil is coupled to the first node, and the fourth terminal of the superconducting coil is coupled to the second node. In an even more particular embodiment, the first switch can be connected to the superconducting coil at a location other than the third terminal or the fourth terminal.
In a second aspect, a system can include a first superconducting element including a first terminal and a second terminal, and a first switch including a third terminal and a fourth terminal, wherein the first switch is not a persistent current switch. The third terminal can be coupled to a first terminal of the first superconducting element, and the fourth terminal can be coupled to a second terminal of the first superconducting element.
In one embodiment of the second aspect, the first superconducting element can be a superconducting coil. In another embodiment, the system can further include a first power supply terminal coupled to the first terminal of the superconducting element, a second power supply terminal coupled to the second terminal of the superconducting element, and a persistent current switch can include a fifth terminal and a sixth terminal, wherein the fifth terminal is coupled to the first power supply terminal, and the sixth terminal is coupled to the second power supply terminal. In a particular embodiment, the persistent current switch and the first switch are connected in parallel. In another particular embodiment, the persistent current switch can include a second superconducting element and a control element. In a more particular embodiment, the control element can include a heating element that is configured to be active when the persistent current switch would be in a higher impedance state and is configured to not be active when the persistent current switch would be in a lower impedance state.
In a further particular embodiment of the second aspect, the first switch and the persistent current switch can be configured such that when the first switch would be in a first lower impedance state and when the persistent current switch would be in a second lower impedance state, the first switch would have a higher impedance as compared to the persistent current switch. In still a further embodiment, the first terminal of the first superconducting element can be coupled to the third terminal of the first switch and the fifth terminal of the persistent current switch, and the second terminal of the first superconducting element can be coupled to the fourth terminal of the first switch and the sixth terminal of the persistent current switch.
In a further embodiment of the second aspect, the first switch can include a mechanical switch. In still a further embodiment, the first switch can be connected to the first superconducting element at a location other than the first terminal or the second terminal. In yet a further embodiment, the system can further include a liquid cryogen that surrounds the first superconducting element.
In a third aspect, a method of using a system can include coupling a first external power supply terminal to a first power supply terminal of the system, coupling a second external power supply terminal to a second power supply terminal of the system, and flowing current through a superconducting element within the system when the first external power supply terminal to the first power supply terminal of the system and the second external power supply terminal to the second power supply terminal of the system. The method can also include placing a persistent current switch of the system into a first lower impedance state, decoupling the first external power supply terminal from the first power supply terminal of the system, decoupling the second external power supply terminal from the second power supply terminal of the system, and placing a first switch of the system into a second lower impedance state.
In one embodiment of the third aspect, the method can further include operating the system, wherein during operating, the persistent current switch changes from a typical operating state to a faulting state, and flowing current through the first switch when the persistent current switch is in the faulting state. In a particular embodiment, the method can further include re-coupling the first external power supply to the first power supply terminal of the system, re-coupling the second external power supply to the second power supply terminal of the system, and reducing the current flow through the first switch of the system after re-coupling the first external power supply to the first power supply terminal of the system and re-coupling the second external power supply to the second power supply terminal of the system and before substantially all liquid cryogen or magnetic field loss occurs.
Note that not all of the activities described above in the general description or the examples are required, that a portion of a specific activity may not be required, and that one or more further activities may be performed in addition to those described. Still further, the order in which activities are listed is not necessarily the order in which they are performed.
The illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The illustrations are not intended to serve as a complete description of all of the elements and features of apparatus and systems that utilize the structures or methods described herein. Many other embodiments may be apparent to those of skill in the art upon reviewing the disclosure. Other embodiments may be utilized and derived from the disclosure, such that a structural substitution, logical substitution, or another change may be made without departing from the scope of the disclosure. Additionally, the illustrations are merely representational and may not be drawn to scale. Certain proportions within the illustrations may be exaggerated, while other proportions may be minimized. Accordingly, the disclosure and the figures are to be regarded as illustrative rather than restrictive.
One or more embodiments of the disclosure may be referred to herein, individually or collectively, by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any particular invention or inventive concept. Moreover, although specific embodiments have been illustrated and described herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the description.
The Abstract of the Disclosure is provided to comply with 37 C.F.R. § 1.72(b) and is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure is not to be interpreted as reflecting an intention that the claimed subject matter requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may be directed to less than all of the features of any of the disclosed embodiments. Thus, the following claims are incorporated into the Detailed Description, with each claim standing on its own as defining separately claimed subject matter.
Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any feature(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature of any or all the claims.
It is to be appreciated that certain features are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. Further, reference to values stated in ranges includes each and every value within that range.
The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover any and all such modifications, enhancements, and other embodiments that fall within the scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.