Electrical connections for use in cryogenic applications

Abstract

An apparatus is described for electrically connecting a superconducting component located within a cryogenic chamber to an electrical device located outside the cryogenic chamber. The apparatus includes a coil including a plurality of helical loops and located within the cryogenic chamber, and an actuator for compressing and expanding the coil between a first state and a second state. In the first state, the coil has a first electrical resistance and a first thermal conductivity, and in the second state, the coil has a second electrical resistance and a second thermal conductivity.

Description

[Background technology]

[0001]

[0001] Superconducting devices, including superconducting magnets, are typically maintained at extremely low pressures and cryogenic temperatures (e.g., near absolute zero) by enclosing the superconducting magnet in a chamber containing a coolant. These superconducting devices are used in a variety of applications, one common application being magnetic resonance imaging (MRI) systems, which are commonly used in medicine.

[0002]

[0002] Maintaining a constant low temperature within these so-called cryogenic chambers is crucial for the proper operation of the superconductors that make up superconducting magnets. Therefore, maintaining a sealed cryogenic chamber is crucial to prevent heat from outside the cryogenic chamber from significantly affecting the temperature inside the cryogenic chamber. However, electrical connections from room-temperature equipment to superconducting components (such as superconducting magnets) are essential. For example, the operation of superconducting components requires the flow of electrical current from an external power source. However, when electrically connecting an external device to a superconducting component within a cryogenic chamber, a thermal conduction path can be created. As a result, unacceptable levels of heat can be transferred from the surroundings to the cryogenic chamber, potentially damaging the desirable superconducting properties of the superconducting component within the cryogenic chamber.

[0003]

[0003] In typical superconducting components (such as magnets), a liquid helium bath is used to maintain the cryogenic temperatures of superconducting coils and accessories housed within a cryogenic chamber. In certain known systems, electrical connection to these types of magnetic coils is often provided by removable electrical leads that penetrate the pressure vessel, relying on the constant evaporation of contained liquid helium to conduct along these leads and temporarily remove the heat generated by them. As such, these leads are inserted into the cryogenic chamber during ramp-up operation of the superconducting component, and once steady-state operation is achieved, these leads are removed to reduce the heat load on the refrigeration system. Specifically, and as known to those skilled in the art, after ramping up the magnet to full current, a superconducting switch is closed to create a loop.

[0004]

[0004] However, some superconducting magnets include a sealed cooling system within the vacuum space of the cryogenic chamber that directly cools the superconducting components. In such applications, an electrical path is required to electrically connect from an electrical device (such as a power source) outside the cryogenic chamber to the superconducting components. Known connections result in unacceptable levels of thermal conductivity along the electrical connections. As a result, the use of known electrical connections can significantly degrade the performance of the superconducting components. Summary of the Invention [Problem to be solved by the invention]

[0005] What is needed, therefore, is an electrical connection between a superconducting component within a cryogenic chamber and an electrical device outside the cryogenic chamber that overcomes at least the shortcomings of the known electrical connections discussed above. [Means for solving the problem]

[0006] According to an aspect of the present disclosure, an apparatus for electrically connecting a superconducting component within a cryogenic chamber to an electrical device outside the cryogenic chamber is disclosed. The apparatus includes a coil including a plurality of helical loops and an actuator for compressing and expanding the coil between a first state and a second state. In the first state, the coil has a first electrical resistance and a first thermal conductivity, and in the second state, the coil has a second electrical resistance and a second thermal conductivity.

[0007] According to another aspect of the present disclosure, a method of providing an electric current to a superconductor component located within a cryogenic chamber is disclosed, the method including the steps of providing an apparatus including a coil including a plurality of helical loops, compressing the coil to a first state, wherein in the first state the coil has a first electrical resistance and a first thermal conductivity, and expanding the coil to a second state, wherein in the second state the coil has a second electrical resistance and a second thermal conductivity.

[0008] According to another aspect of the present disclosure, a magnetic resonance imaging (MRI) system includes a magnet system including a superconducting magnet within a cryogenic chamber, and an apparatus for electrically connecting a superconducting component within the cryogenic chamber to an electrical device outside the cryogenic chamber. The apparatus includes a coil including a plurality of helical loops, and an actuator for compressing and expanding the coil between a first state and a second state. In the first state, the coil has a first electrical resistance and a first thermal conductivity, and in the second state, the coil has a second electrical resistance and a second thermal conductivity. [Brief explanation of the drawings]

[0009]

[0009] Example embodiments are best understood from the following detailed description when read in conjunction with the accompanying drawing figures. It is emphasized that the various features are not necessarily drawn to scale. In fact, dimensions have been arbitrarily increased or decreased for clarity of discussion. Where applicable and practical, like reference numerals refer to like elements.

[0010] [Figure 1] FIG. 1 illustrates a magnetic resonance imaging (MRI) system according to a representative embodiment. [Figure 2] FIG. 2 is a perspective view of an apparatus for electrically connecting a superconducting component located within a cryogenic chamber to an electrical device located outside the cryogenic chamber according to a representative embodiment. [Figure 3]

[0011] FIG. 3 is a cross-sectional view of an apparatus for making electrical connections within a cryogenic chamber in a first state, according to a representative embodiment. [Figure 4]

[0012] FIG. 4 is a cross-sectional view of an apparatus for making electrical connections within a cryogenic chamber in a second state, according to a representative embodiment. [Figure 5]

[0013] FIG. 5 is a perspective cross-sectional view of an apparatus for making electrical connections in a cryogenic chamber in a first state according to a representative embodiment. [Figure 6]

[0014] FIG. 6 is a perspective cross-sectional view of an apparatus for making electrical connections in a cryogenic chamber in a second state according to a representative embodiment. [Figure 7]

[0015] FIG. 7 is a conceptual diagram illustrating the compressive and expansive forces applied by an actuator to compress an apparatus for making electrical connections in a cryogenic chamber from a second state to a first state. [Figure 8]

[0016] FIG. 8 is a flowchart of a method for providing electrical current to a superconductor component located within a cryogenic chamber, according to a representative embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0017] In the following detailed description, for purposes of explanation and not limitation, exemplary embodiments disclosing specific details are set forth to provide a thorough understanding of embodiments according to the present teachings. Descriptions of known systems, devices, materials, methods of operation, and methods of manufacture may be omitted so as not to obscure the description of the exemplary embodiments. However, systems, devices, materials, and methods within the purview of those skilled in the art are within the scope of the present teachings and may be used in accordance with the exemplary embodiments. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. Defined terms are intended to add the technical and scientific meaning of the defined terms as commonly understood and accepted in the art of the present teachings.

[0012]

[0018] Although terms such as "first," "second," and "third" are used herein to describe various elements or components, it should be understood that these elements or components are not limited by these terms. These terms are used only to distinguish one element or component from another. Thus, a first element or component discussed below could be termed a second element or component without departing from the teachings of the inventive concept.

[0013]

[0019] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in this specification and the appended claims, the singular terms "a," "an," and "the" are intended to include both the singular and the plural unless the context clearly dictates otherwise. Furthermore, the term "comprises" and / or similar terms specify the presence of stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0014]

[0020] Unless otherwise specified, when an element or component is said to be "connected," "coupled," or "adjacent" to another element or component, it is understood that the element or component may be directly connected or coupled to the other element or component, or there may be intervening elements or components. That is, these and similar terms encompass the case where one or more intermediate elements or components may be used to connect the two elements or components. However, when an element or component is said to be "directly connected" to another element or component, this only encompasses the case where the two elements or components are connected to each other with no intermediate or intervening elements or components.

[0015]

[0021] As used herein and in the appended claims, and in addition to their ordinary meaning, the terms "substantial" or "substantially" mean an acceptable limit or degree, e.g., "substantially thermally isolated" means that one of ordinary skill in the art would consider thermal isolation acceptable.

[0016]

[0022] As used herein and in the appended claims, and in addition to its ordinary meaning, the term "approximately" means within a limit or amount that would be acceptable to one of ordinary skill in the art. For example, "approximately the same" means that one of ordinary skill in the art would consider the compared items to be the same.

[0017]

[0023] The present disclosure describes embodiments, and / or particular features, subcomponents, according to one or more of its various aspects, and is therefore intended to provide one or more of the advantages specifically set forth below. For purposes of explanation and not limitation, example embodiments disclosing specific details are described to provide a thorough understanding of embodiments according to the present teachings. However, other embodiments consistent with the present disclosure that depart from the specific details disclosed herein remain within the scope of the appended claims. Furthermore, descriptions of well-known devices and methods may be omitted so as not to obscure the description of the example embodiments. Such methods and devices are within the scope of the present disclosure.

[0018]

[0024] The present teachings disclose an apparatus and method for providing an electrical connection between sealed superconducting magnets that reduces heat loss from a cryogenic chamber. In certain embodiments, the apparatus connects to an actuator (such as a solenoid-operated electrical switch) within the vacuum space of the cryogenic chamber to enable electrical connection between an electrical device within the room temperature space and the superconducting magnet within the cryogenic chamber during transient use, while substantially thermally preventing significant heat loss from the cryogenic chamber during steady-state operation (i.e., providing substantial thermal isolation of the superconducting magnet).

[0019]

[0025] Beneficially, and as described in more detail below, the apparatus and methods of the present teachings substantially overcome the difficulties of balancing magnetic bistable behavior (i.e., ramp-up and steady-state operation), ohmic heating, heat conduction, and ice intolerance within a magnetic system. As described in more detail below, the apparatus described in connection with various exemplary embodiments achieves lower ohmic heating, similar steady-state heat conduction, lower transient heat conduction, and superior ice tolerance compared to known electrical connections. These improvements result in increased performance in areas such as refrigeration capacity, magnet system availability, and magnet system reliability, as well as magnet manufacturability, to name a few. Finally, while various exemplary embodiments of the apparatus and methods of the present teachings are described in connection with a magnetic resonance imaging (MRI) system, it should be emphasized that this is merely an exemplary application. More generally, the apparatus and methods of the present teachings are contemplated for use in other applications requiring electrical connection between a device within a cryogenic chamber and an electrical device located outside the cryogenic chamber and at a higher temperature (e.g., room temperature).

[0020]

[0026] The electrical connection to the superconducting magnet provided by the apparatus of various exemplary embodiments described below is necessary to change the state of the magnetic field. When the magnet is needed for imaging, current is ramped up by passing it through the superconducting coils through the apparatus in a first state. Once the full magnetic field is achieved and the superconducting circuit is completed, the apparatus is placed in a second state. As described in more detail below, in the second state, both electrical and thermal conduction through the apparatus is approximately two orders of magnitude lower than in the first state.

[0021]

[0027] In certain circumstances, returning the device to the first state and zeroing the voltage removes current from the superconducting coils through the device. Operation of the device is controlled by on-board magnet electronics, which determine when the device can switch from the first state to the second state or vice versa. The electronics use known algorithms to determine when to operate the device based on input from a number of sensors. These electronics, including the processor 112, memory 114, and actuators 304, 404, 504, may be part of the MRI system 100, described below, and function according to the method 800, described below. Alternatively, the device may be manually operated to switch between the first and second states based on the timing and sequence of ramp-up / ramp-down events.

[0022]

[0028] Although the magnet can remain in the field for very long periods (years) without external intervention, there are reasons to ramp down a superconducting magnet and then ramp it up again for operation. These reasons include, for example, preventative maintenance schedules for external magnet system components, cleaning or maintenance of the imaging suite, safety, power loss, and other common occurrences. The present teachings allow these desired ramp-up and ramp-down of a superconducting magnet to be performed without compromising the seal of the cryogenic chamber housing the superconducting magnet. Furthermore, during relatively long periods of operation, the apparatus of various representative embodiments reduces heat loss from the cryogenic chamber to an acceptable level. For illustrative purposes, heat loss in the second state is approximately two orders of magnitude lower than heat loss in the first state (e.g., during ramp-up).

[0023]

[0029] FIG. 1 illustrates an exemplary embodiment of an MRI system 100 in accordance with a representative embodiment. The MRI system 100 includes a magnet system 101, a patient table 104 that holds a subject or patient 20, gradient coils 103 that at least partially surround at least a portion of the patient 20 for which the MRI system 100 generates an image, radio frequency coils 105 that apply radio frequency signals to at least a portion of the subject or patient 20 being imaged and perturb the magnetic field alignment, and one or more sensors 106 that detect changes in the magnetic field caused by the radio frequency signals and the patient 20. In particular, the magnet system 101 includes a main magnet 106 that resides within a cryogenic chamber 107. The main magnet 106 includes a superconducting coil 108 that is maintained at an appropriate temperature and pressure via the cryogenic chamber 107. As mentioned above, the magnet system 101 is sealed using a two-state device (not shown in FIG. 1 ) that connects the superconducting coil 108 to an electrical connection via conduit 109 and to a power supply (not shown) used to power the superconducting magnet. In particular, although the MRI system 100 is described in the singular, the term "system" shall be construed to include a collection of systems or subsystems that individually or collectively execute one or more sets of software instructions.

[0024]

[0030] The MRI system 100 also includes a power supply 110, a processor 112, and a memory 114. The memory 114 and the processor 112 are sometimes collectively referred to as a controller. In certain exemplary embodiments, the memory 114 and the processor 112 may be components of a main system (not shown) used to control various components of the system. Alternatively, the memory 114 and the processor 112 may be separate elements from the main system. The controller may include a display (not shown), including, but not limited to, a light-emitting diode (LED), a liquid crystal display (LCD), an organic light-emitting diode (OLED) display, a flat panel display, a solid-state display, or a cathode ray tube (CRT). The controller, including the memory 114 and the processor 112, may be housed in or linked to a workstation (not shown), such as a computer or a separate assembly of one or more computing devices, a display / monitor, and one or more input devices (such as a keyboard, joystick, mouse, etc.) in the form of a standalone computing system, desktop, tablet, etc., to perform one or more computer functions.

[0025]

[0031] The tangible, non-transient processor 112 represents one or more processors. As used herein, the term "non-transient" is to be interpreted as a property of a state that persists for a period of time, rather than a permanent property of the state. The term "non-transient" specifically negates momentary properties, such as carrier waves or signals or other types of properties that exist only temporarily at any time and in any place. The processor 112 (and other processors) of the present teachings are products and / or machine parts.

[0026]

[0032] The processor 112 executes software instructions stored in the memory 114 to perform various functions, including ramping up and down a superconducting magnet using the apparatus described in various embodiments herein. The processor 112 may be a general-purpose processor or part of an application-specific integrated circuit (ASIC). The processor 112 may also be (or include) a microprocessor, microcomputer, processor chip, controller, microcontroller, digital signal processor (DSP), state machine, or programmable logic device. The processor 112 may also be (or include) a logic circuit, such as a programmable gate array (PGA) such as an FPGA, or another type of circuit including discrete gate and / or transistor logic. The processor 112 may be (or include) a central processing unit (CPU), a graphics processing unit (GPU), or both. Furthermore, the processor 112 may include multiple processors, parallel processors, or both. Multiple processors may be included in or combined within a single device or multiple devices.

[0027]

[0033] The memory 114 may include main memory, static memory, or both, and the memories may communicate with each other via a bus (not shown). The memory 114 described herein is a tangible storage medium capable of storing data and executable instructions and is non-transitory while the instructions are stored therein. As used herein, the term "non-transitory" is to be interpreted as a property of a state that persists for a period of time, rather than a permanent property of a state. The term "non-transitory" specifically negates fleeting properties, such as those of a carrier wave or signal or other type of property that exists only temporarily at any time and in any place.

[0028]

[0034] The memory 114 of the present teachings is a product and / or machine component. The memory 114 includes one or more computer-readable media from which the processor 112 can read data and executable instructions (e.g., to execute the processes described in connection with ramp-up and steady-state operations). The memory described herein may be random access memory (RAM), read-only memory (ROM), flash memory, electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disk, removable disk, tape, compact disk read-only memory (CD-ROM), digital versatile disk (DVD), floppy disk, Blu-ray disk, or any other form of storage medium known to those skilled in the art. The memory of the present teachings may be volatile or nonvolatile memory, secure and / or encrypted memory, or non-secure and / or unencrypted memory. The monitor and interface (not shown), processor 112 and memory 114 may be housed in or linked to a workstation (not shown), such as a computer or another assembly of one or more computing devices, a display / monitor, and one or more input devices (keyboard, joystick, mouse, etc.), in the form of a standalone computing system, desktop or tablet, etc.

[0029]

[0035] For illustrative purposes, the main magnet is a 1.5 T (or greater) sealed MRI magnet commercially available from Koninklijke Philips. The apparatus described below allows for electrical connection of an external 300 K power supply to a superconducting magnet maintained at 40 K, providing improved electrical and thermal properties compared to known connections. However, it is emphasized that the apparatus is not limited to use in MRI devices and systems, but may be implemented in any one of many applications requiring electrical connections across relatively large temperature gradients that necessitate specific desired electrical and thermal behavior. Thus, apparatus according to various embodiments of the present teachings enable electrical connections across the interface between a relatively low temperature environment (e.g., a cryogenic chamber) and a relatively high temperature environment (e.g., room temperature).

[0030]

[0036] FIG. 2 is a perspective view of an apparatus 200 for electrically connecting a superconducting component (not shown in FIG. 2) located within a cryogenic chamber (not shown in FIG. 2) to an electrical device (not shown in FIG. 2) located outside the cryogenic chamber, according to a representative embodiment. The apparatus 200 has a first end 202, a second end 204, and a plurality of helical loops 206 between the first end 202 and the second end 204. As will be understood as the description progresses, the apparatus provides an electrical path and a thermal path between the superconducting component and the electrical device. In FIG. 2, the apparatus is shown in a compressed state (sometimes referred to as a first state). This results in an increased cross-sectional area, resulting in a decreased electrical resistance and increased thermal conductivity compared to the apparatus 200 stretched in an expanded state (sometimes referred to as a second state).

[0031]

[0037] Device 200 is generally made of a flexible, conductive material cut to create a seam 208 that allows it to compress in the −x direction of the coordinate system of Figure 2 or expand in the +x direction of the coordinate system of Figure 2. For ease of understanding, the conductive material may include copper or aluminum, and device 200 in its compressed state has an axial length (x direction of the coordinate system of Figure 2) of approximately 4 inches (1 inch = 2.54 cm).

[0032]

[0038] As will be explained in more detail below, when compressed, the seams 208 between adjacent helical loops 206 are beneficially substantially gap-free, as adjacent helical loops 206 are in physical contact with one another. In contrast, when stretched, the seams 208 between adjacent helical loops are relatively large, typically preventing one helical loop 206 from physically contacting an adjacent helical loop 206. By way of illustration only, in the uncompressed state, the seams 208 form a gap of approximately 0.050 inches to 0.100 inches. Notably, the gap typically depends on the distance of movement and the force required to expand the device to a second state. Thus, device 200 is a continuous structure that is compressible to a first state and stretchable to a second state, as will be explained below, capable of changing its effective cross-sectional area and altering both its electrical and thermal conductivity.

[0033]

[0039] 3 is a cross-sectional view of an apparatus 300 for making electrical connections within a cryogenic chamber 302 in a first state, according to an exemplary embodiment. Various aspects and details of apparatus 300 are similar or identical to those described in connection with the exemplary embodiment of FIGS. 1 and 2 and will not be repeated so as not to obscure the description of this exemplary embodiment.

[0034]

[0040] Apparatus 300 resides within cryogenic chamber 302 and includes actuator 304. For ease of understanding, actuator 304 is an electrical, solenoid-actuated device. More generally, actuator 304 is one of many devices that provide a force suitable for expanding / compressing apparatus 300. These include, but are not limited to, known linear motors and translation mechanisms such as cams, pistons, or rods. As described in more detail below, actuator 304 compresses apparatus 300 (in the −z direction of the illustrated coordinate system) when a connection is required to provide power from a power source (not shown) to the superconducting components. As described above, compression places the apparatus in a first state, where the apparatus forms an electrically (and thermally) conducting tube. In contrast, and as described in more detail below, when the superconducting components are functioning in a steady-state mode, the actuator applies a force to expand apparatus 300, placing apparatus 300 in a second state. In the second state, the seams between the spiral loops comprising device 300 are relatively large, typically preventing one spiral loop from physically contacting an adjacent spiral loop. As noted above, the second state results in a relatively high electrical resistance and a relatively low thermal conductivity. Device 300 is connected to cryochamber 302 using conduit 306. To aid in understanding, conduit 306 is a ceramic piece (such as a ring) through which electrical connection 308 to actuator 304 and device 300 is made. Conduit 306 is advantageously a poor conductor of heat, thereby reducing heat transfer from the ambient to cryochamber 302 and preventing significant impact on the performance of the superconducting components located within the cryochamber. Thus, conduit 306 typically comprises a ceramic material that provides substantial electrical and thermal isolation from the ambient or exterior of the cryocontainer, along with a substantially leak-tight seal. Conduit 306 typically has a diameter of about 2 inches to about 3 inches and a thickness (x direction in the coordinate system of FIG. 3) of about 0.5 inches.

[0035]

[0041] In the first state, device 300 provides a relatively low electrical resistance path between external electrical devices and the superconducting components within the cryogenic chamber. As noted above and described in more detail below, in the compressed state (first state), the device provides a substantially solid tube having a ring-shaped cross-section, as shown. This ring-shaped cross-section provides a cross-section with increased electrical (and thermal) conductivity compared to the discrete helical loops present when device 300 is uncompressed. Thus, in this first state, the electrical resistance is beneficially low compared to the electrical resistance in the second state, as described in more detail below.

[0036]

[0042] For example, when the superconducting component requires ramp-up, actuator 304 compresses apparatus 300, providing an electrical path from an external electronic device (such as a power supply) via (external) electrical connection 308 to internal electrical connection 310, which is electrically connected to the superconducting component. As will be appreciated, apparatus 300 allows for electrical connection between an external electrical device (such as a power supply) at 300 K and a superconducting component (such as the magnet of an MRI device or system) maintained at 40 K, providing improved electrical and thermal properties compared to known connections.

[0037]

[0043] 4 is a cross-sectional view of an apparatus 400 for making electrical connections within a cryogenic chamber in a second state, according to an exemplary embodiment. Various aspects and details of apparatus 400 are similar or identical to those described in connection with the exemplary embodiment of FIGS. 1-3 and will not be repeated so as not to obscure the description of this exemplary embodiment.

[0038]

[0044] Apparatus 400 resides within cryogenic chamber 402 and includes actuator 404. For ease of understanding, actuator 404 is a solenoid-actuated device. As described in more detail below, actuator 404 expands apparatus 400 (in the +z direction of the illustrated coordinate system) when the superconducting components are operating in a steady state with substantially no power applied to the superconducting components. As noted above, expansion of apparatus 400 causes the apparatus to enter a second state in which the seams between the helical loops comprising apparatus 400 are relatively large, typically preventing one helical loop from physically contacting an adjacent helical loop. As noted above, the second state results in a relatively high electrical resistance and a relatively low thermal conductivity.

[0039]

[0045] Apparatus 400 is connected to cryochamber 402 using conduit 406. To aid in understanding, conduit 406 is substantially similar to conduit 306 described above, being a ceramic piece (such as a ring) through which electrical connections 408 are made to actuator 404 and apparatus 400. Conduit 406 is beneficially a poor conductor of heat, thereby reducing heat transfer from the surroundings to cryochamber 402 and preventing a significant impact on the performance of the superconducting components located within the cryochamber.

[0040]

[0046] In the second state, device 400 provides a relatively high electrical resistance path between external electrical devices and the superconducting components within cryogenic chamber 402. As noted above and described in more detail below, in the expanded state (second state), the device presents a substantially rectangular cross-section as shown. This rectangular cross-section provides a cross-section with reduced electrical (and thermal) conductivity compared to the ring-shaped cross-sectional loop that device 400 assumes when compressed. Thus, in this second state, the thermal resistance is beneficially higher compared to the thermal resistance of device 400 in the first state, as described in more detail below.

[0041]

[0047] For example, when the superconducting component requires steady-state operation, actuator 404 expands device 400. Because device 400 has a relatively small conductive cross-section, the electrical path from an external electronic device (e.g., a power source) through (external) electrical connection 408 to internal electrical connection 410, which is electrically connected to the superconducting component, has a relatively large electrical and thermal resistance. Therefore, during steady-state operation, current conduction and thermal conduction are reduced to acceptable values. For ease of understanding, during steady-state operation, current conduction and thermal conduction are reduced to acceptable levels. For ease of understanding, during steady-state operation, current conduction and thermal conduction are two orders of magnitude lower than those of device 300 described above. Beneficially, this reduces heat loss from cryogenic chamber 402. As can be seen, device 400 allows electrical connection between an external electrical device (e.g., a power source) at 300 K and a superconducting component (e.g., a magnet in an MRI device or system) maintained at 40 K, providing improved electrical and thermal properties compared to known connections.

[0042]

[0048] Beneficially, the relatively low electrical conductivity of the second state promotes a form of self-cleaning. Specifically, ice formation on surfaces is not an uncommon problem when magnets are operating at steady state. This occurs even in the substantial absence of moisture, as ice can form from nitrogen in the environment. In known devices, ice can form on the contact pads of electrical connections. Therefore, a distinct advantage of device 400 lies in its helical coil design. To this end, if ice forms between adjacent turns of adjacent helical coils (e.g., seams 508 of adjacent helical loops 506 in the exemplary embodiment described below) when device 400 is in the second state during steady-state operation, actuation to compress the device to the first state compresses the helical loops, reducing the conductive cross-section at the location of the ice formation, as described below, but separating the coil turns (maintaining some gap), so that electrically, the cross-section of this turn corresponds to that in the second state (described below). This results in relatively high electrical resistance and relatively high ohmic heating. When device 400 is compressed to the first state, heat generated during conduction raises the temperature, melts the ice, and the gap between adjacent helical coils is again substantially zero (i.e., they touch each other). Beneficially, in the present teachings, this cleaning step is performed by a controller external to the cryogenic chamber, and therefore, is performed without compromising the seal of the cryogenic chamber.

[0043]

[0049] 5 is a perspective cross-sectional view of an apparatus 500 for making electrical connections in a cryogenic chamber in a first state, according to a representative embodiment. Various aspects and details of apparatus 500 are similar or identical to those described in connection with the representative embodiment of FIGS. 1-4 and will not be repeated so as not to obscure the description of this representative embodiment.

[0044]

[0050] The device 500 includes a plurality of helical loops 506. The device 500 provides electrical and thermal paths between a superconducting component and an electrical device. Similar to the devices described above, the device 500 is generally made of a flexible, electrically conductive material that is cut to have seams 508 that allow it to either compress in the −z direction of the coordinate system of FIG. 5 or, as described below, stretch in an expanded state in the +z direction of the coordinate system of FIG. 5. As described above, when compressed, the seams 508 between adjacent helical loops 506 are relatively small. Thus, when compressed, adjacent helical loops 506 are in intimate contact, resulting in the device 500 exhibiting a ring-shaped conductive cross-section. Specifically, the cross-sectional area of ​​the device 500 is π(r o 2 -r i 2 ), where r o is the outer diameter of the spiral loop 506, and r i is the inner diameter of the helical loop 506. As noted above, in this first state, the device provides a lower electrical resistance compared to when the device is in the second state (when adjacent helical rings are physically separated). In particular, the electrical and thermal resistances of device 500 are reduced to acceptable levels. To aid in understanding, the electrical and thermal resistances of device 500 are two orders of magnitude lower than the electrical and thermal resistances of the device in the second state when helical loops 506 are separated.

[0045]

[0051] In the first state, a continuous electrical path is provided from one end of the device 500 to the other, minimizing the effects of surface contamination. Specifically, when the mating surfaces of adjacent helical loops 506 are compressed, the compressed structure (turn) is free of contamination, and electricity conducts through the large compressed cross-section and along the short compressed length. The short structure provided by the device 500, with its larger cross-sectional area compared to the expanded device, offers little thermal resistance. Furthermore, if the mating surfaces between adjacent helical loops 506 are contaminated with ice, heat will be generated locally in these regions due to the reduced conductive cross-section. As this region of the device 500 is heated by the flow of electrical current, the contaminants will evaporate (especially in a vacuum), leaving behind a clean, conductive surface, as desired.

[0046]

[0052] Furthermore, the inter-turn pressure between adjacent helical loops 506, which results in electrical conductivity similar to a closed cross-section, is much lower than the inter-turn pressure that results in thermal conductivity similar to a closed cross-section. This means that the cross-section of the compressed device 500 is nearly electrically uninterrupted, but thermally much smaller, compared to the device in its expanded state where the helical loops 506 are separated.

[0047]

[0053] 6 is a perspective cross-sectional view of an apparatus 600 for making electrical connections in a cryogenic chamber in a first state, according to a representative embodiment. Various aspects and details of apparatus 600 are similar or identical to those described in connection with the representative embodiment of FIGS. 1-5 and will not be repeated so as not to obscure the description of this representative embodiment.

[0048]

[0054] Device 600 includes a plurality of helical loops 606. Device 500 provides electrical and thermal paths between a superconducting component and an electrical device. Similar to the devices described above, device 600 is generally made of a flexible, electrically conductive material cut to create seams 508 that allow it to stretch or expand in the +z direction of the coordinate system of FIG. 6 or, as described above, compress in the −z direction of the coordinate system of FIG. 6 into a compressive state. As described above, when stretched, the seams 608 between adjacent helical loops 606 are relatively large. Thus, when stretched or expanded, adjacent helical loops 606 are stretched, and device 600 exhibits a rectangular conductive cross-section having an area H×W, where H is the height of helical loop 606 and W is the width of helical loop 606. In particular, when H=W, the device exhibits a square conductive cross-section. As described above, in this second state, the electrical resistance offered by the device is higher compared to when the device is in the first state (when adjacent helical loops are physically separated). In particular, the electrical and thermal resistances of device 600 are increased relative to device 500. To aid in understanding, the electrical and thermal resistances of device 600 are two orders of magnitude greater than the electrical and thermal resistances of device 500 in the first state when the helical coils are separated.

[0049]

[0055] In particular, during periods when no current needs to be passed through device 600, device 600 is uncompressed and adjacent helical loops 606 are separated (i.e., seams 608 are larger in the +z direction of the coordinate system of FIG. 6). In this second state, heat conduction from one end of device 600 to the other must occur through a relatively smaller H×W cross-section and along a larger uncompressed length compared to compressed device 500. Such a relatively long structure with a smaller cross-sectional area provides poor heat conduction compared to compressed device 500.

[0050]

[0056] Additionally, heat radiated through the open space at seam 608 between adjacent helical loops 606 is reduced compared to compressed device 500. This results in a smaller temperature difference between adjacent helical loops 606 compared to device 500. Furthermore, when device 600 is used in a vacuum, there is no convective heat transfer across seam 608. Therefore, in this second state, heat loss by device 600 is lower compared to device 500 in which the helical loops 506 are compressed and in contact with each other.

[0051]

[0057] 7 is a conceptual diagram illustrating the compressive and expansive forces (F) applied by an actuator to compress and elongate or expand an apparatus 700 for making electrical connections in a cryogenic chamber from a second state to a first state. Various aspects and details of apparatus 700 are similar or identical to those described in connection with the exemplary embodiment of FIGS. 1-6 and will not be repeated so as not to obscure the description of this exemplary embodiment.

[0052]

[0058] As shown in FIG. 7 , an actuator (e.g., actuators 304, 404) applies a force that compresses device 700 (i.e., a force in the −z direction according to the coordinate system shown in FIG. 7 ) and a force that expands or stretches device 700 (i.e., a force in the +z direction according to the coordinate system shown in FIG. 7 ). As described above, when compressed by an actuator, device 700 enters a first state in which it has a lower electrical resistance and a higher thermal conductivity compared to when device 700 is stretched. Similarly, when stretched by an actuator, device 700 enters a second state in which it has a higher electrical resistance and a lower thermal conductivity compared to when device 700 is compressed. As described above, the electrical resistance and thermal conductivity of device 700 in the first state are two orders of magnitude lower than the electrical resistance and thermal conductivity of device 700 in the second state.

[0053]

[0059] 8 is a flowchart of a method for providing an electric current to a superconductor component located in a cryogenic chamber, according to an exemplary embodiment. Various aspects and details of method 800 are similar or identical to those described in connection with the exemplary embodiment of FIGS. 1-7 and will not be repeated so as not to obscure the description of this exemplary embodiment.

[0054]

[0060] The method includes, in step 801, providing a device including a coil including a plurality of helical loops.

[0055]

[0061] The method includes compressing the coil to a first state at step 802. In the first state, the device has a first electrical resistance and a first thermal conductivity.

[0056]

[0062] The method expands the device to a second state in step 803. In the second state, the device has a second electrical resistance and a second thermal conductivity.

[0057]

[0063] Methods, systems, and components for reducing heat loss and providing power across an interface between a relatively low temperature environment (such as a cryogenic chamber) and a relatively high temperature environment (such as room temperature) have been described with reference to several exemplary embodiments, but it is understood that the terms used are terms of description and illustration, rather than of limitation. Changes may be made in their aspects within the scope of the appended claims, as presently presented and as amended, without departing from the scope and spirit of interventional procedure optimization. While the development of adaptive predictive analytics has been described with reference to particular means, materials, and embodiments, it is not intended that the development of adaptive predictive analytics be limited to the details disclosed. Rather, the development of adaptive predictive analytics extends to all functionally equivalent structures, methods, and uses, as within the scope of the appended claims.

[0058]

[0064] The illustrations of the embodiments described herein are intended to provide a general understanding of the structure of various embodiments. The illustrations do not completely describe all elements and features of the disclosure described herein. Many other embodiments will be apparent to those skilled in the art upon reviewing the present disclosure. Other embodiments may be utilized and derived from the present disclosure, such as structural and logical substitutions and changes that may be made without departing from the scope of the present disclosure. Furthermore, the illustrations are merely representative and may not be to scale. Certain proportions in the illustrations may be exaggerated, while other proportions may be minimized. Therefore, the present disclosure and the figures should be considered illustrative and not restrictive.

[0059]

[0065] Although specific embodiments have been illustrated and described herein, it should be understood that subsequent arrangements designed to achieve the same or similar purposes may be substituted for the specific embodiments shown. The present disclosure is intended to cover any and all subsequent adaptations or variations of the various embodiments. Combinations of the above embodiments with other embodiments not specifically described herein will be apparent to those skilled in the art upon review of the description.

[0060]

[0066] This 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. Additionally, the foregoing Detailed Description may group or describe various features 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 embodiments require 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 features of any of the disclosed embodiments. Accordingly, the following claims are incorporated into this Detailed Description, with each claim standing on its own as defining separate claimed subject matter.

[0061]

[0067] The foregoing description of the disclosed embodiments is provided to enable any person skilled in the art to practice the concepts described in the present disclosure. Accordingly, the above disclosed subject matter is considered to be illustrative and not restrictive. Furthermore, the appended claims are intended to cover all such modifications, enhancements, and other implementations that fall within the true spirit and scope of the present disclosure. Accordingly, to the maximum extent permitted by law, the scope of the present disclosure shall be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be limited or restricted by the foregoing detailed description.

Claims

1. 1. An apparatus for electrically connecting a superconducting component located within a cryogenic chamber to an electrical device located outside the cryogenic chamber, the apparatus comprising: a coil providing an electrical path from the external electrical device to the superconducting component, the coil including a plurality of helical loops and located within the cryogenic chamber; an actuator for compressing and expanding the coil between a first state and a second state; Including, 1. An apparatus, wherein in the first state, the coil has a first electrical resistance and a first thermal conductivity, and in the second state, the coil has a second electrical resistance and a second thermal conductivity; The apparatus, wherein the actuator includes a linear motor.

2. The apparatus of claim 1 , wherein the first electrical resistance is less than the second electrical resistance.

3. The apparatus of claim 1 , wherein the first thermal conductivity is greater than the second thermal conductivity.

4. 10. The device of claim 1, wherein the device has a first cross-sectional area in the first state and a second cross-sectional area in the second state, the second cross-sectional area being smaller than the first cross-sectional area.

5. 5. The device of claim 4, wherein when the device is in the first state, the helical loops are compressed relative to one another and the first cross-sectional area is the area of ​​a ring.

6. 5. The device of claim 4, wherein when the device is in the second state, the helical loops separate from one another and the second cross-sectional area is a rectangular area.

7. 6. The device of claim 5, wherein a current of a first magnitude is passed through the device when the device is in the first state.

8. 8. The device of claim 7, wherein substantially no current flows through the device when the device is in the second state.

9. 1. A method of providing an electric current to a superconductor component located within a cryogenic chamber, the method comprising: providing an apparatus including a coil providing an electrical path from an electrical device to the cryogenic chamber to the superconductor component, the coil including a plurality of helical loops; compressing the coil to a first state, wherein in the first state the coil has a first electrical resistance and a first thermal conductivity; expanding the coil to a second state, wherein in the second state the coil has a second electrical resistance and a second thermal conductivity; Including, The method wherein the compression and expansion are performed by a linear motor.

10. The method of claim 9 , wherein the first electrical resistance is less than the second electrical resistance.

11. The method of claim 9 , wherein the first thermal conductivity is greater than the second thermal conductivity.

12. 10. The method of claim 9, wherein the device has a first cross-sectional area in the first state and a second cross-sectional area in the second state, the second cross-sectional area being smaller than the first cross-sectional area.

13. 13. The method of claim 12, wherein when the device is in the first state, the helical loops are compressed relative to one another and the first cross-sectional area is the area of ​​a ring.

14. 13. The method of claim 12, wherein when the device is in the second state, the helical loops separate from one another and the second cross-sectional area is a rectangular area.

15. a magnet system including a superconducting magnet located within a cryogenic chamber; An apparatus according to any one of claims 1 to 8; 1. A magnetic resonance imaging (MRI) system comprising:

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