Multichannel SQUID cryogenic thermometer and method of making

Abstract

The present disclosure relates to a multi-channel SQUID cryogenic thermometer and a preparation method thereof, comprising: a plurality of SQUID coils; a plurality of superconducting gradient coils, each superconducting gradient coil being connected to a corresponding SQUID coil, each superconducting gradient coil comprising a plurality of sub-coils, and the plurality of sub-coils of each superconducting gradient coil being connected in series; wherein at least two sub-coils of the plurality of sub-coils of each superconducting gradient coil are located above the metal to be measured of the SQUID, and at least two sub-coils of the plurality of sub-coils of each superconducting gradient coil are located at the hollow position. The present disclosure can at least reduce the readout time of the SQUID when reading the system temperature noise and reduce the test time of the SQUID through the multi-channel setting. At least through the multi-channel setting, the SQUID can reduce the readout time when reading the system temperature noise and reduce the test time of the SQUID.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of superconducting electronics, and particularly relates to a multi-channel SQUID cryogenic thermometer and a preparation method thereof. BACKGROUND

[0002] A superconducting quantum interference device (SQUID) is a magnetic field sensor with the highest sensitivity at present, and its equivalent energy resolution can approach the quantum limit level, and is widely used in biological magnetic measurement and geomagnetic detection. A current sensor based on a SQUID can precisely measure a small current and other signals equivalent to magnetic flux, and is the only readout device of a transition-edge sensor (TES), a metallic magnetic calorimeter (MMC), a cryogenic current comparator (CCC) and other instruments. Therefore, as a key core device of modern large-scale scientific devices in cosmology and biomedicine, the SQUID is crucial for the research on its preparation process, configuration design, principle and theory simulation and amplification readout technology.

[0003] In the related art, the low-temperature SQUID needs to read the noise of the system temperature, generally adopts a double-channel SQUID design, and needs to make the readout lines of the two-channel SQUID as consistent as possible when designing, so as to eliminate the random noise on the line through a long integration time, and only leave the low-temperature temperature noise signal, and the current double-channel SQUID also needs a very long test time (up to 700 minutes) to ensure a certain test accuracy. SUMMARY

[0004] Therefore, it is necessary to provide a multi-channel SQUID cryogenic thermometer and a preparation method thereof to at least reduce the readout time of the SQUID when reading the system temperature noise and reduce the test time of the SQUID by means of the multi-channel setting.

[0005] In order to achieve the above object and other objects, in a first aspect, the present disclosure provides a multi-channel SQUID cryogenic thermometer, comprising: a plurality of SQUID coils, a plurality of superconducting gradient coils, each superconducting gradient coil is connected to a corresponding SQUID coil, each superconducting gradient coil comprises a plurality of sub-coils, and each superconducting gradient coil is connected in series by a plurality of sub-coils, wherein at least two sub-coils in the plurality of sub-coils of each superconducting gradient coil are located on a metal to be measured of the SQUID, and at least two sub-coils in the plurality of sub-coils of each superconducting gradient coil are located at a hollow position.

[0006] In at least two of the above embodiments, by arranging multiple SQUID coils and multiple superconducting gradient coils, the SQUID can reduce the readout time when reading the system temperature noise and reduce the test time of the SQUID through the multi-channel arrangement.

[0007] In one of the embodiments, the winding directions of the multiple sub-coils on the metal to be tested of the SQUID are the same and are coupled to each other.

[0008] In one of the embodiments, the winding directions of the multiple sub-coils at the hollowed-out position are opposite to the winding directions of the multiple sub-coils on the metal to be tested of the SQUID, and are decoupled from each other.

[0009] In one of the embodiments, the multiple sub-coils on the metal to be tested of the SQUID are used to read the metal noise of the target metal; and the multiple sub-coils at the hollowed-out position are used to read the space noise.

[0010] In the multi-channel SQUID cryogenic thermometer of the above embodiments, by effective coupling of the superconducting gradient coils, the temperature noise in the metal to be tested is read, and the two-by-two decoupling design is performed at the hollowed-out position, which eliminates the interference of the space noise on the low-temperature thermometer.

[0011] In one of the embodiments, the multiple SQUID coils are located on the same side of the multi-channel SQUID cryogenic thermometer.

[0012] In the multi-channel SQUID cryogenic thermometer of the above embodiments, by arranging the multiple SQUID coils on the same side, the coupling between the superconducting gradient coils is more convenient, and more superconducting gradient coils can be coupled to effectively eliminate the interference of the space noise.

[0013] In one of the embodiments, the multiple sub-coils on the metal to be tested of the target SQUID coil include a first coil and a second coil, and the multiple sub-coils at the hollowed-out position include a third coil, a fourth coil, a fifth coil, and a sixth coil, wherein one end of the first coil is connected to one end of a SQUID coil, the other end of the first coil is connected to one end of the third coil, the other end of the third coil is connected to one end of the fourth coil, the other end of the fourth coil is connected to one end of the fifth coil, the other end of the fifth coil is connected to one end of the sixth coil, the other end of the sixth coil is connected to one end of the second coil, and the other end of the second coil is connected to the other end of the SQUID coil.

[0014] In the multi-channel SQUID cryogenic thermometer of the above embodiments, the first coil and the second coil are used to detect the temperature noise of the resistance to be tested, and the third coil, the fourth coil, the fifth coil, and the sixth coil are used to detect the space noise, thereby improving the detection accuracy.

[0015] In one of the embodiments, the multiple sub-coils of each superconducting gradient coil are electrically connected through the superconducting metal on-chip.

[0016] In the multi-channel SQUID cryogenic thermometer in the above embodiments, the whole chip design is used to avoid the additional interface resistance, and only the random spatial noise is coupled through the inductance.

[0017] In one of the embodiments, each SQUID coil comprises: a substrate; a first superconducting layer on the substrate; a first insulating layer on the first superconducting layer; a second superconducting layer on the first insulating layer; a second insulating layer on the second superconducting layer; a third superconducting layer on the second insulating layer; a resistance layer on the third superconducting layer; a metal to be measured in the multi-channel SQUID cryogenic thermometer; and a superconducting gradient coil layer partially above the metal to be measured and partially in the hollow position in the multi-channel SQUID cryogenic thermometer.

[0018] In one of the embodiments, the substrate, the first superconducting layer, the first insulating layer, the second superconducting layer, the second insulating layer, the third superconducting layer and the resistance layer are used to form multiple SQUID coils.

[0019] In a second aspect, the embodiments of the present disclosure further provide a preparation method of a multi-channel SQUID cryogenic thermometer, comprising: forming a substrate; forming a first superconducting layer on the substrate and etching the first superconducting layer to obtain a first superconducting layer with a first target pattern; forming a first insulating layer on the first superconducting layer; forming a second superconducting layer on the first insulating layer; forming a second insulating layer on the second superconducting layer; forming a third superconducting layer on the second insulating layer and etching the third superconducting layer to obtain an input coil of a SQUID, a feedback coil of the SQUID and a bias coil of the SQUID; forming a resistance layer on the third superconducting layer; forming a metal to be measured in the multi-channel SQUID cryogenic thermometer, wherein the metal to be measured is formed above the resistance layer without contact; and forming a superconducting gradient coil layer partially above the metal to be measured and partially in a hollow position in the multi-channel SQUID cryogenic thermometer.

[0020] In the preparation method of the multi-channel SQUID cryogenic thermometer in the above embodiments, multiple SQUID coils and multiple superconducting gradient coils are provided, and the multi-channel setting reduces the readout time of the SQUID when reading the system temperature noise and reduces the test time of the SQUID. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0022] Figure 1 An equivalent schematic diagram of a multi-channel SQUID cryogenic thermometer provided in an embodiment;

[0023] Figure 2 An equivalent schematic diagram of another multi-channel SQUID cryogenic thermometer provided in an embodiment;

[0024] Figure 3 A structural schematic diagram of a multi-channel SQUID cryogenic thermometer provided in an embodiment;

[0025] Figure 4 A flowchart of a preparation method of a multi-channel SQUID cryogenic thermometer provided in an embodiment.

[0026] Legend of reference signs:

[0027] CH1, first SQUID coil; CH2, second SQUID coil; CH3, third SQUID coil; CH4, fourth SQUID coil; 201, metal to be measured; 202, hollowed position; L1, first coil; L2, second coil; L3, third coil; L4, fourth coil; L5, fifth coil; L6, sixth coil; 13, first superconducting layer; 14, third superconducting layer; 201, substrate; 202, second superconducting layer; 203, first insulating layer; 204, second insulating layer; 205, resistance layer. DETAILED DESCRIPTION

[0028] In order to facilitate the understanding of the present disclosure, the present disclosure will be described more fully below with reference to the related drawings. The preferred embodiments of the present disclosure are shown in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present disclosure more thorough and comprehensive.

[0029] 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 the present disclosure belongs. The terms used in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure.

[0030] It will be understood that when an element or layer is referred to as being "on" or "connected to" another element or layer, it can be directly on or connected to the other element or layer or intervening elements or layers can be present. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element or layer, there are no intervening elements or layers present. It will also be understood that, although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section; for example, a first doped type could be termed a second doped type; and similarly, a second doped type could be termed a first doped type; a first doped type and a second doped type are different doped types, for example, a first doped type can be P-type and a second doped type can be N-type, or a first doped type can be N-type and a second doped type can be P-type.

[0031] Spatially relative terms, such as "beneath", "below", "lower", "under", "above", "upper" and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and / or operation in addition to the orientations depicted in the figures. For example, if a device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device can also be oriented in the other direction (for example, rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. The terms "first", "second", "third", etc. can be used herein to describe various elements, components, regions, layers and / or sections but are not intended to be limiting. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section; for example, a first doped type could be termed a second doped type; and similarly, a second doped type could be termed a first doped type; a first doped type and a second doped type are different doped types, for example, a first doped type can be P-type and a second doped type can be N-type, or a first doped type can be N-type and a second doped type can be P-type.

[0032] As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. It should also be understood that, when the term "comprising" is used in the present description and claims, it is intended to mean that the compositions and methods include the recited elements, integers, steps, or components, but not to the exclusion of one or more other elements, integers, steps, components, or groups thereof. Additionally, as used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0033] Embodiments of the invention are described herein with reference to cross-sectional views that serve as schematic diagrams of preferred embodiments (and intermediate structures) of the present disclosure, thus allowing for variations in the illustrated shapes due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of the present disclosure should not be limited to the specific shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing techniques. For instance, implantation regions shown as rectangular typically have rounded or curved features at their edges and / or implantation concentration gradients, rather than a binary change from implantation regions to non-implantation regions. Similarly, buried regions formed by implantation can result in some implantation in the region between the buried region and the surface traversed during implantation. Therefore, the regions shown in the figures are substantially schematic, and their shapes do not represent the actual shapes of regions of the device and do not limit the scope of the present disclosure.

[0034] Please see Figure 1 , Figure 1 This application provides a schematic diagram of a prior art two-channel SQUID in a two-channel SQUID cryothermometer. The SQUID is located at both ends of the superconducting gradient coil (i.e.,...). Figure 1 The two numbers 1 and 2 are each connected to a channel (SQUID), and electrical connections are made using spot welding, with additional leads introduced.

[0035] Based on existing two-channel SQUID technology, the readout lines of the two channels need to be as consistent as possible. This requires a long integration time to eliminate random noise on the lines, leaving only the low-temperature noise signal. Furthermore, in terms of testing, current dual-channel SQUID testing also requires a very long testing time (up to 700 minutes) to ensure a certain level of testing accuracy.

[0036] It should be noted that a SQUID (Superconducting Quantum Interference Device) cryothermometer is an extremely sensitive temperature measurement device specifically designed for temperature measurement in extremely low-temperature environments (such as the millikelvin level). Because SQUIDs can detect extremely weak magnetic field changes, they can be combined with other temperature-sensitive materials to accurately measure temperatures at low temperatures. However, due to their extreme sensitivity to external magnetic fields, SQUIDs are easily affected by circuit noise and ambient noise. Therefore, detecting circuit noise and ambient noise significantly improves the accuracy and sensitivity of the cryothermometer.

[0037] Please see Figures 2-3It should be noted that the diagram provided in the embodiment only illustrates the basic concept of the present application in a schematic manner, and only shows the components related to the present application, not the number, shape and size of the components when actually implemented. The actual implementation of each component may be a random change, and the component layout may be more complex.

[0038] Please refer to Figures 2-3 , Figure 2 is an equivalent circuit diagram of a multi-channel SQUID cryogenic thermometer provided in an embodiment. It should be noted that the present application takes a four-channel SQUID cryogenic thermometer as an example to give an equivalent circuit diagram of a four-channel SQUID cryogenic thermometer. The multi-channel SQUID cryogenic thermometer mentioned in the present application can be four-channel, eight-channel, sixteen-channel, etc. The setting and connection relationship of each channel are similar to the design position and connection relationship of the channels in the four-channel SQUID cryogenic thermometer, which will not be described here.

[0039] It should be noted that the number of channels can be set according to the actual size of the cryogenic thermometer and the required temperature detection speed and accuracy. It should be understood that the increase of the number of channels is multiplied to enhance the temperature measurement speed and accuracy.

[0040] Please continue to refer to Figure 2 , Figure 2 The multi-channel SQUID cryogenic thermometer includes: a plurality of SQUID coils; a plurality of superconducting gradient coils, each superconducting gradient coil is connected to a corresponding SQUID coil, and each superconducting gradient coil includes a plurality of sub-coils, and the plurality of sub-coils of each superconducting gradient coil are connected in series; wherein at least two sub-coils of the plurality of sub-coils of each superconducting gradient coil are located above the measured metal 201 of the SQUID, and at least two sub-coils of the plurality of sub-coils of each superconducting gradient coil are located at the hollow position 202.

[0041] Wherein, the winding directions of the plurality of sub-coils located above the measured metal 201 of the SQUID are the same and are coupled to each other.

[0042] As an example, the plurality of SQUID coils includes a first SQUID coil CH1, a second SQUID coil CH2, a third SQUID coil CH3, and a fourth SQUID coil CH4.

[0043] Wherein, the winding directions of the plurality of sub-coils located at the hollow position 202 are opposite to the winding directions of the plurality of sub-coils located above the measured metal 201 of the SQUID, and each two are decoupled.

[0044] As shown in Figure 2 , Figure 2The arrowed lines between the coils in the plurality of channels indicate the coupling relationship between the plurality of sub-coils, the arrowed lines above the metal to be measured 201 indicate the coupling relationship between the plurality of coils, and the arrowed lines in the hollow position 202 indicate the decoupling relationship between the plurality of coils.

[0045] Specifically, the plurality of sub-coils above the metal to be measured 201 of the SQUID are used to read the metal noise of the metal to be measured 201.

[0046] Specifically, the plurality of sub-coils at the hollow position 202 are used to read the spatial noise.

[0047] Specifically, the multi-channel SQUID cryogenic thermometer further comprises a SQUID signal reading unit, the four-channel coils can be coupled in the same direction by winding, and the temperature noise signal on the metal substrate 201 can be read together, and the coils at the hollow position 202 are decoupled to balance the spatial magnetic flux noise between different channels.

[0048] Please continue to refer to Figure 2 , the plurality of SQUID coils are located on the same side of the multi-channel SQUID cryogenic thermometer.

[0049] Specifically, the plurality of sub-coils above the metal to be measured 201 of the target SQUID coil include a first coil L1 and a second coil L2, and the plurality of sub-coils at the hollow position 202 include a third coil L3, a fourth coil L4, a fifth coil L5, and a sixth coil L6.

[0050] One end of the first coil L1 is connected to one end of a SQUID coil, the other end of the first coil L1 is connected to one end of the third coil L3, the other end of the third coil L3 is connected to one end of the fourth coil L4, the other end of the fourth coil L4 is connected to one end of the fifth coil L5, the other end of the fifth coil L5 is connected to one end of the sixth coil L6, the other end of the sixth coil L6 is connected to one end of the second coil L2, and the other end of the second coil L2 is connected to the other end of the SQUID coil.

[0051] Each superconducting gradient coil is connected to the plurality of sub-coils through a superconducting metal sheet.

[0052] The superconducting metal sheet can be superconducting niobium, which can avoid additional magnetic flux noise and other influences and can accelerate the temperature measurement speed by several times.

[0053] Here, the temperature signal is collected into the SQUID by the superconducting gradient coil, and the electrical connection between them is a superconducting niobium lead connection, which eliminates the interference of additional magnetic flux noise and interface resistance, etc., and effectively improves the test speed.

[0054] Please refer to Figure 3 In one embodiment, the multi-channel SQUID cryogenic thermometer includes: a substrate 201; a first superconducting layer 13 on the substrate 201; a first insulating layer 203 on the first superconducting layer 13; a second superconducting layer 202 on the first insulating layer 203; a second insulating layer 204 on the second superconducting layer 202; a third superconducting layer 14 on the second insulating layer 204; a resistance layer 205 on the third superconducting layer 14; a metal to be measured 201 (not shown in the figure) in the multi-channel SQUID cryogenic thermometer; a superconducting gradient coil layer (not shown in the figure), part of which is above the metal to be measured 201 and part of which is in the hollow position 202 in the multi-channel SQUID cryogenic thermometer.

[0055] The substrate 201, the first superconducting layer 13, the first insulating layer 203, the second superconducting layer 202, the second insulating layer 204, the third superconducting layer 14 and the resistance layer 205 are used to form a plurality of SQUID coils.

[0056] It should be noted that the superconducting quantum interference device formed by the plurality of SQUID coils also includes an input coil, a feedback coil, a bias port, a Josephson junction and other structures of the superconducting quantum interference device. The specific structure of the superconducting quantum interference device will not be described here.

[0057] Please refer to Figure 4 As an example, the embodiment of the present disclosure provides a multi-channel SQUID cryogenic thermometer preparation method, including the following steps:

[0058] Step S1000: forming a substrate 201.

[0059] The substrate 201 can be made of a semiconductor material or an insulating material. The substrate 201 can be a single-layer structure or a multi-layer structure. For example, the substrate 201 can be a silicon substrate 201, a silicon dioxide substrate 201, etc., or, for example, the substrate 201 can be a layered substrate 201 including silicon / silicon carbide, silicon-on-insulator or silicon-on-silicon germanium. Therefore, the type of substrate 201 should not limit the protection scope of the present disclosure.

[0060] Step S2000: forming a target superconducting layer on the substrate 201.

[0061] The target superconducting layer includes a first superconducting layer 13, a first insulating layer 203, and a second superconducting layer 202. The first superconducting layer 13 is located on the substrate 201. The first insulating layer 203 is located on the first superconducting layer 13. The second superconducting layer 202 is located on the first insulating layer 203.

[0062] The first superconducting layer 13 is also referred to as a bottom electrode (BE layer), that is, a superconducting thin film layer.

[0063] Specifically, the material of the first superconducting layer 13 is polycrystalline niobium (Nb).

[0064] As an example, a magnetron sputtering method can be used to deposit and etch a corresponding pattern (for example, a positive plate + positive resist method can be used).

[0065] The thickness of the first superconducting layer 13 can be 100 nm to 200 nm.

[0066] As an example, the thickness of the first superconducting layer 13 can be 100 nm, 130 nm, 155 nm, 180 nm, or 200 nm, and the like.

[0067] The first insulating layer 203 is used to form a channel layer of a Josephson junction.

[0068] Specifically, the material of the first insulating layer 203 is aluminum oxide.

[0069] As an example, a corresponding pattern can be etched by ion beam etching after anodic oxidation (for example, a positive plate + positive resist method can be used).

[0070] The thickness of the first insulating layer 203 can be 8 nm to 16 nm.

[0071] As an example, the thickness of the first insulating layer 203 can be 8 nm, 10 nm, 12 nm, 15 nm, or 16 nm, and the like.

[0072] Specifically, the material of the second superconducting layer 202 is polycrystalline niobium (Nb).

[0073] As an example, a magnetron sputtering method can be used to deposit and etch a corresponding pattern (for example, a positive plate + positive resist method can be used).

[0074] The thickness of the second superconducting layer 202 can be 100 nm to 200 nm.

[0075] As an example, the thickness of the second superconducting layer 202 can be 100 nm, 110 nm, 130 nm, 170 nm, 190 nm, or 200 nm, and the like.

[0076] Step S3000: forming a second insulating layer 204 on the target superconducting layer.

[0077] Specifically, the material of the second insulating layer 204 can be silicon oxide.

[0078] The thickness of the second insulating layer 204 can be 350 nm-380 nm.

[0079] For example, the thickness of the second insulating layer 204 can be 350 nm, 360 nm, 370 nm, 380 nm, etc.

[0080] Step S4000: forming a third superconducting layer 14 on the second insulating layer 204, and etching the third superconducting layer 14 to obtain an input coil of a SQUID, a feedback coil of the SQUID, and a bias coil of the SQUID.

[0081] Specifically, the material of the third superconducting layer 14 is polycrystalline niobium (Nb).

[0082] For example, a magnetron sputtering method can be used to deposit and ion beam etch a corresponding pattern (for example, a positive resist + positive resist method can be used).

[0083] The thickness of the third superconducting layer 14 can be 390 nm-410 nm.

[0084] For example, the thickness of the third superconducting layer 14 can be 390 nm, 395 nm, 400 nm, or 410 nm, etc.

[0085] Step S5000: forming a resistance layer 205 on the third superconducting layer 14.

[0086] Specifically, the material of the resistance layer 205 can be a PdAu thin film.

[0087] The thickness of the resistance layer 205 can be 50 nm-500 nm.

[0088] For example, the thickness of the resistance layer 205 can be 50 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc.

[0089] For example, a chemical vapor deposition method can be used to deposit and etch a corresponding pattern (for example, a negative resist + positive resist method can be used).

[0090] Step S6000: forming a metal to be measured 201 in the multi-channel SQUID cryogenic thermometer.

[0091] The metal to be measured 201 is formed above the resistance layer 205 without contact.

[0092] Here, the metal to be measured 201 can be a temperature-sensitive metal such as copper.

[0093] Step S7000: A superconducting gradient coil layer is formed on the multi-channel SQUID cryogenic thermometer, and the superconducting gradient coil layer is partially located above the metal to be measured 201 and partially located at the hollow position 202 in the channel SQUID cryogenic thermometer.

[0094] In the preparation method of the multi-channel SQUID cryogenic thermometer in the above embodiment, by arranging a plurality of SQUID coils and a plurality of superconducting gradient coils, the readout time of the SQUID when reading out the system temperature noise is reduced, and the test time of the SQUID is also reduced. The technical features of the above embodiment can be combined arbitrarily. In order to make the description simple, all possible combinations of the technical features of the above embodiment are not described, but as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present disclosure.

[0095] The above embodiments only express several implementation manners of the present disclosure, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be noted that for those skilled in the art, without departing from the concept of the present disclosure, a number of modifications and improvements can be made, which are all within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure patent should be subject to the appended claims.

Claims

1. A multi-channel SQUID cryogenic thermometer characterized by, The multi-channel SQUID cryogenic thermometer comprises: a plurality of SQUID coils; a plurality of superconducting gradient coils, each superconducting gradient coil being connected with a corresponding one of the SQUID coils respectively, each superconducting gradient coil comprising a plurality of sub-coils, and each superconducting gradient coil being connected in series by the plurality of sub-coils; wherein at least two of the plurality of sub-coils of each superconducting gradient coil are located above a metal to be measured of the SQUID coil, and at least two of the plurality of sub-coils of each superconducting gradient coil are located at a hollow position; the hollow position is located on the side of the metal to be measured; the plurality of sub-coils located above the metal to be measured of the SQUID coil have the same winding direction and are coupled to each other; the plurality of sub-coils located at the hollow position have opposite winding directions to the plurality of sub-coils located above the metal to be measured of the SQUID coil, and are decoupled from each other; the plurality of sub-coils located above the metal to be measured of the SQUID coil are used to read the metal noise of the metal to be measured; and the plurality of sub-coils located at the hollow position are used to read the space noise.

2. The multi-channel SQUID cryogenic thermometer of claim 1, wherein, The plurality of SQUID coils are located on the same side of the multi-channel SQUID cryogenic thermometer.

3. The multi-channel SQUID cryogenic thermometer of claim 1, wherein, The plurality of sub-coils located above the metal to be measured of the SQUID coil comprise a first coil and a second coil, and the plurality of sub-coils located at the hollow position comprise a third coil, a fourth coil, a fifth coil, and a sixth coil, wherein one end of the first coil is connected with one end of one of the SQUID coils, the other end of the first coil is connected with one end of the third coil, the other end of the third coil is connected with one end of the fourth coil, the other end of the fourth coil is connected with one end of the fifth coil, the other end of the fifth coil is connected with one end of the sixth coil, the other end of the sixth coil is connected with one end of the second coil, and the other end of the second coil is connected with the other end of the one of the SQUID coils.

4. The multi-channel SQUID cryogenic thermometer of claim 1, wherein, The plurality of sub-coils of each superconducting gradient coil are connected by a superconducting metal on a chip.

5. The multi-channel SQUID cryogenic thermometer of claim 1, wherein, The multi-channel SQUID cryogenic thermometer comprises: a substrate; a first superconducting layer on the substrate; a first insulating layer on the first superconducting layer; a second superconducting layer on the first insulating layer; a second insulating layer on the second superconducting layer; a third superconducting layer on the second insulating layer; a resistance layer on the third superconducting layer; a metal to be measured in the multi-channel SQUID cryogenic thermometer, wherein the multi-channel SQUID cryogenic thermometer has a hollow position on the side of the metal to be measured; and a superconducting gradient coil layer, part of which is located above the metal to be measured and part of which is located at the hollow position in the multi-channel SQUID cryogenic thermometer.

6. The multi-channel SQUID cryogenic thermometer of claim 5, wherein, The substrate, the first superconducting layer, the first insulating layer, the second superconducting layer, the second insulating layer, the third superconducting layer, and the resistance layer are used to form a plurality of SQUID coils.

7. A method of fabricating a multi-channel SQUID cryogenic thermometer, characterized by, comprising: forming a substrate; forming a target superconducting layer on the substrate, the target superconducting layer comprising a first superconducting layer, a first insulating layer and a second superconducting layer, the first superconducting layer being on the substrate, the first insulating layer being on the first superconducting layer, and the second superconducting layer being on the first insulating layer; forming a second insulating layer on the target superconducting layer; forming a third superconducting layer on the second insulating layer, and etching the third superconducting layer to obtain an input coil of a SQUID, a feedback coil of the SQUID, and a bias coil of the SQUID; forming a resistance layer on the third superconducting layer; forming a metal to be measured in the multi-channel SQUID cryogenic thermometer, the metal to be measured being formed above the resistance layer without contact; forming a superconducting gradient coil layer in the multi-channel SQUID cryogenic thermometer, the superconducting gradient coil layer being partially above the metal to be measured and partially at a hollow position in the multi-channel SQUID cryogenic thermometer; the hollow position being beside the metal to be measured; wherein the winding directions of a plurality of sub-coils in the superconducting gradient coil layer above the metal to be measured are the same and are coupled to each other; the winding directions of a plurality of sub-coils in the superconducting gradient coil layer at the hollow position are opposite to those of the plurality of sub-coils above the metal to be measured, and the sub-coils are decoupled from each other.

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