Multi-channel SQUID low-temperature thermometer and preparation method thereof

Abstract

The invention relates to a multi-channel SQUID low-temperature thermometer and a preparation method thereof. The multi-channel SQUID low-temperature thermometer comprises a plurality of SQUID coils; a plurality of superconducting gradient coils, each superconducting gradient coil is connected with a corresponding SQUID coil, each superconducting gradient coil comprises 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 in the plurality of sub-coils of each superconducting gradient coil are located above to-be-tested metal of the SQUID, and at least two sub-coils in the plurality of sub-coils of each superconducting gradient coil are located at the hollowed-out positions. According to the invention, at least through the arrangement of multiple channels, the reading time is reduced when the SQUID reads the temperature noise of the system, and the test time of the SQUID is reduced. At least through the arrangement of multiple channels, the reading time is reduced when the SQUID reads the system temperature noise, and the test time of the SQUID is reduced.

Description

Technical Field

[0001] The present disclosure relates to the technical field of superconducting electronics, and in particular to a multi-channel SQUID low-temperature thermometer and a preparation method thereof. Background Art

[0002] Superconducting Quantum Interference Device (SQUID) is the most sensitive magnetic field sensor currently. Its equivalent energy resolution is close to the quantum limit level and is widely used in biomagnetic measurement and geomagnetic detection. The current sensor based on SQUID can accurately measure tiny currents and other signals that can be equivalently converted into magnetic flux. It is the only readout device for instruments such as superconducting transition edge sensor (TES), metallic magnetic calorimeter (MMC), and cryogenic current comparator (CCC). Therefore, as a key core device of modern large-scale scientific devices in cosmology and biomedicine, the research on its preparation process, configuration design, principle theoretical simulation, and amplification readout technology is crucial.

[0003] In the related technology, the low-temperature SQUID needs to read the noise of the system temperature. Generally, a dual-channel SQUID design is adopted. During the design, the readout lines of the two-channel SQUID need to be as consistent as possible. Therefore, a longer integration time is required to eliminate the random noise on the line, leaving only the low-temperature temperature noise signal. In addition, in terms of current dual-channel SQUID testing, in order to ensure a certain test accuracy, the test time is also very long (up to 700 minutes). Summary of the invention

[0004] Based on this, it is necessary to provide a multi-channel SQUID low-temperature thermometer and a preparation method thereof to address the above technical problems, which can at least reduce the readout time of the SQUID when reading the system temperature noise through the multi-channel setting, and reduce the test time of the SQUID.

[0005] In order to achieve the above-mentioned purpose and other purposes, 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, each superconducting gradient coil is connected in series by a plurality of sub-coils, wherein at least two of the plurality of sub-coils of each superconducting gradient coil are located on the metal to be measured of the SQUID, and at least two of the plurality of sub-coils of each superconducting gradient coil are located at a hollow position.

[0006] In the above embodiment, by arranging multiple SQUID coils and multiple superconducting gradient coils in at least two superconducting gradient coils, a multi-channel arrangement is provided, so that the readout time of the SQUID when reading out the system temperature noise is reduced, and the test time of the SQUID is reduced.

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

[0008] In one embodiment, the winding directions of the multiple sub-coils located at the hollowed-out positions and the multiple sub-coils located on the metal to be tested of the SQUID are opposite, and the sub-coils are decoupled in pairs.

[0009] In one embodiment, a plurality of sub-coils located on the metal to be tested of the SQUID are used to read the metal noise of the target metal; and a plurality of sub-coils located at the hollow position are used to read the spatial noise.

[0010] In the multi-channel SQUID cryogenic thermometer in the above embodiment, the temperature noise in the metal to be measured is read through the effective coupling of the superconducting gradient coils, and a pairwise decoupling design is performed at the hollow positions, thereby eliminating the interference of spatial noise on the cryogenic thermometer.

[0011] In one embodiment, multiple SQUID coils are located on the same side of a multi-channel SQUID cryostat.

[0012] In the multi-channel SQUID cryogenic thermometer in the above embodiment, by arranging multiple SQUID coils on the same side, it is easier to couple the superconducting gradient coils, and the interference of spatial noise can be more effectively eliminated by coupling more superconducting gradient coils.

[0013] In one embodiment, the multiple sub-coils located on the metal to be tested of the target SQUID coil include a first coil and a second coil, and the multiple sub-coils located at the hollow 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 a SQUID coil.

[0014] In the multi-channel SQUID low-temperature thermometer in the above embodiment, the temperature noise of the resistor to be measured is detected by the first coil and the second coil, and the spatial noise is detected by the third coil, the fourth coil, the fifth coil, and the sixth coil, thereby improving the detection accuracy.

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

[0016] In the multi-channel SQUID low-temperature thermometer in the above embodiment, the whole chip design is used to avoid the additional interface resistance, and the random spatial noise is only coupled by induction.

[0017] In one embodiment, each SQUID coil includes: a substrate; a first superconducting layer, located on the substrate; a first insulating layer, located on the first superconducting layer; a second superconducting layer, located on the first insulating layer; a second insulating layer, located on the second superconducting layer; a third superconducting layer, located on the second insulating layer; a resistor layer, located on the third superconducting layer; a metal to be measured, located in a multi-channel SQUID cryogenic thermometer; and a superconducting gradient coil layer, wherein the superconducting gradient coil layer is partially located above the metal to be measured and partially located at a hollow position in the channel SQUID cryogenic thermometer.

[0018] In one embodiment, the substrate, the first superconducting layer, the first insulating layer, the second superconducting layer, the second insulating layer, the third superconducting layer and the resistive layer are used to form a plurality of SQUID coils.

[0019] In a second aspect, the disclosed embodiment also provides a method for preparing 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 of 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 for forming a SQUID, a feedback coil for the SQUID, and a bias coil for 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, the superconducting gradient coil layer being partially located above the metal to be measured and partially located at a hollow position in the channel SQUID cryogenic thermometer.

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

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

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

[0023] Figure 2 is an equivalent schematic diagram of another multi-channel SQUID low-temperature temperature measuring device provided in an embodiment;

[0024] Figure 3 A schematic diagram of the structure of a multi-channel SQUID low-temperature thermometer provided in an embodiment;

[0025] Figure 4 Flow chart of a method for preparing a multi-channel SQUID low-temperature thermometer provided in one embodiment.

[0026] Description of reference numerals:

[0027] CH1, first SQUID coil; CH2, second SQUID coil; CH3, third SQUID coil; CH4, fourth SQUID coil; 201, metal to be tested; 202, hollow 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 understanding of the present disclosure, the present disclosure will be described more fully below with reference to the relevant 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 those commonly understood by those skilled in the art to which the present disclosure belongs. The terms used herein 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 should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. On the contrary, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, doping types and / or parts, these elements, components, regions, layers, doping types and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, doping type or part from another element, component, region, layer, doping type or part. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer, doping type or portion discussed below may be represented as a second element, component, region, layer or portion; for example, the first doping type may be referred to as the second doping type, and similarly, the second doping type may be referred to as the first doping type; the first doping type and the second doping type are different doping types, for example, the first doping type may be P-type and the second doping type may be N-type, or the first doping type may be N-type and the second doping type may be P-type.

[0031] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientations shown in the figures, spatially relative terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, an element or feature described as "under other elements" or "under it" or "under it" will be oriented as being "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0032] When used herein, the singular forms "a", "an" and " / the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that when the terms "consisting of" and / or "comprising" are used in this specification, the presence of features, integers, steps, operations, elements and / or components can be determined, but the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups is not excluded. At the same time, when used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0033] Embodiments of the invention are described herein with reference to cross-sectional views which are schematic representations of ideal embodiments (and intermediate structures) of the present disclosure, such that variations in the shapes shown due to, for example, manufacturing techniques and / or tolerances are anticipated. Thus, embodiments of the present disclosure should not be limited to the particular shapes of the regions shown herein, but rather include deviations in shapes due to, for example, manufacturing techniques. For example, an implanted region shown as a rectangle typically has rounded or curved features and / or an implant concentration gradient at its edges rather than a binary change from an implanted region to a non-implanted region. Similarly, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation is performed. Thus, the regions shown in the figures are schematic in nature, their shapes do not represent the actual shape of the region of the device, and do not limit the scope of the present disclosure.

[0034] See also Figure 1 , Figure 1 The schematic diagram of the two-channel SQUID in the prior art provided in the embodiment of the present application, in the two-channel SQUID low temperature thermometer, the SQUID is at both ends of the superconducting gradient coil (ie Figure 1 The two digital labels 1 and 2 are connected to a channel respectively in the SQUID), and spot welding process is required for electrical connection, and additional leads are introduced.

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

[0036] It should be noted that the SQUID (Superconducting Quantum Interference Device) cryogenic thermometer is an extremely sensitive temperature measurement device, which is specially used for temperature measurement in extremely low temperature environments (such as milliKelvin level). Since SQUID can detect extremely weak magnetic field changes, it can be combined with other temperature-sensitive materials to accurately measure the temperature at low temperatures. However, since SQUID is extremely sensitive to external magnetic fields and is easily affected by line noise and spatial noise, the detection of line noise and spatial noise plays a great role in improving the accuracy and sensitivity of cryogenic thermometers.

[0037] See also Figure 2-Figure 3It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present application in a schematic manner. The illustrations only show the components related to the present application rather than being drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0038] See also Figure 2-Figure 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 provide 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 channel in the four-channel SQUID cryogenic thermometer, and will not be repeated here.

[0039] It should be noted that the number of channels can be set according to the actual size of the low-temperature thermometer and the required temperature detection speed and accuracy. It should be understood that as the number of channels increases, the temperature measurement speed and accuracy are enhanced exponentially.

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

[0041] The winding directions of the multiple sub-coils located above the metal to be tested 201 of the SQUID are the same and they are coupled to each other.

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

[0043] The winding directions of the multiple sub-coils located at the hollow position 202 and the multiple sub-coils located on the metal to be tested 201 of the SQUID are opposite, and they are decoupled in pairs.

[0044] like Figure 2 As shown in Figure 2The indicator lines with arrows between the coils of multiple channels indicate the coupling relationship between the multiple sub-coils, the multiple indicator lines with arrows located above the metal to be tested 201 indicate the coupling relationship between the multiple coils, and the multiple indicator lines with arrows located at the hollow position 202 indicate the decoupling relationship between the multiple coils.

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

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

[0047] Specifically, the multi-channel SQUID low-temperature thermometer also includes a SQUID signal readout unit. The four-channel coils can be coupled by winding in the same direction on the metal 201 to be tested, and jointly read the temperature noise signal on the metal substrate 201. The coils are decoupled in pairs at the hollow position 202 to balance the spatial magnetic flux noise between different channels.

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

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

[0050] Among them, 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] The multiple sub-coils of each superconducting gradient coil are electrically connected on-chip through a superconducting metal sheet.

[0052] The superconducting metal sheet may be superconducting niobium. The on-chip electrical connection of the superconducting niobium can avoid the influence of additional magnetic flux noise and can increase the temperature measurement speed exponentially.

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

[0054] See also Figure 3 In one embodiment, the multi-channel SQUID cryogenic thermometer includes: a substrate 201; a first superconducting layer 13, located on the substrate 201; a first insulating layer 203, located on the first superconducting layer 13; a second superconducting layer 202, located on the first insulating layer 203; a second insulating layer 204, located on the second superconducting layer 202; a third superconducting layer 14, located on the second insulating layer 204; a resistance layer 205, located on the third superconducting layer 14; a metal to be measured 201 (not shown in the figure), located in the multi-channel SQUID cryogenic thermometer; a superconducting gradient coil layer (not shown in the figure), wherein the superconducting gradient coil layer is partially located above the metal to be measured 201 and partially located at a hollow position 202 in the 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 multiple SQUID coils also includes the structures of the superconducting quantum interference device such as an input coil, a feedback coil, a bias port, and a Josephson junction. The specific structure of the superconducting quantum interference device will not be repeated here.

[0057] Please refer to Figure 4 As an example, the present disclosure provides a method for preparing a multi-channel SQUID low-temperature thermometer, comprising the following steps:

[0058] Step S1000: forming a substrate 201 .

[0059] The substrate 201 may be made of semiconductor material or insulating material. The substrate 201 may be a single-layer structure or a multi-layer structure. For example, the substrate 201 may be a silicon substrate 201, a silicon dioxide substrate 201, or the like, or, for another example, the substrate 201 may be a layered substrate 201 including, for example, silicon / silicon carbide, silicon on insulator, or silicon germanium on insulator. Therefore, the type of the 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 called (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 may be used to deposit and etch the corresponding pattern (for example, a positive plate + positive resist method may be used).

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

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

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

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

[0069] As an example, the corresponding pattern may be etched out by ion beam etching after anodization (for example, a positive plate + positive resist method may be used).

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

[0071] As an example, the thickness of the first insulating layer 203 may be 8 nm, 10 nm, 12 nm, 15 nm, 16 nm, etc.

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

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

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

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

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

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

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

[0079] As an example, the thickness of the second insulating layer 204 may 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 for forming a SQUID, a feedback coil for the SQUID, and a bias coil for the SQUID.

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

[0082] As an example, magnetron sputtering may be used for deposition and ion beam etching may be used to form a corresponding pattern (for example, a positive plate + positive resist method may be used).

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

[0084] As an example, the thickness of the third superconducting layer 14 may 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 may be a PdAu thin film.

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

[0088] As an example, the thickness of the resistive layer 205 may be 50 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc.

[0089] As an example, chemical vapor deposition may be used to deposit and etch corresponding patterns (eg, a negative plate + positive resist method may be used).

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

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

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

[0093] Step S7000: forming a superconducting gradient coil layer in the multi-channel SQUID cryogenic thermometer, wherein 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 method for preparing the multi-channel SQUID cryogenic thermometer in the above embodiment, by setting a plurality of SQUID coils and a plurality of superconducting gradient coils, the multi-channel setting reduces the readout time when the SQUID reads out the system temperature noise, and reduces the test time of the SQUID. The technical features of the above embodiment can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features of the above embodiment are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The above embodiments only express several implementation methods of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure shall be subject to the attached claims.

Claims

1. A multi-channel SQUID low temperature thermometer, characterized in that: The multi-channel SQUID cryogenic thermometer comprises: Multiple SQUID coils; A plurality of superconducting gradient coils, each of which is connected to a corresponding SQUID coil, each of which comprises a plurality of sub-coils, and each of which is connected in series by a plurality of sub-coils; Among them, at least two sub-coils among the multiple sub-coils of each superconducting gradient coil are located above the metal to be measured of the SQUID, and at least two sub-coils among the multiple sub-coils of each superconducting gradient coil are located at the hollow position.

2. The multi-channel SQUID cryogenic thermometer according to claim 1, characterized in that: The multiple sub-coils located above the metal to be tested of the SQUID are wound in the same direction and are coupled to each other.

3. The multi-channel SQUID cryogenic thermometer according to claim 1 or 2, characterized in that: The winding directions of the multiple sub-coils located at the hollowed-out positions and the multiple sub-coils located on the metal to be tested of the SQUID are opposite, and they are decoupled in pairs.

4. The multi-channel SQUID cryogenic thermometer according to claim 1, characterized in that: A plurality of sub-coils located above the metal to be tested of the SQUID are used to read the metal noise of the metal to be tested; Multiple sub-coils located at the hollowed-out positions are used to read spatial noise.

5. The multi-channel SQUID cryogenic thermometer according to claim 1, characterized in that: The plurality of SQUID coils are located on the same side of the multi-channel SQUID cryostat.

6. The multi-channel SQUID cryogenic thermometer according to claim 1, characterized in that: The multiple sub-coils located on the metal to be tested of the target SQUID coil include a first coil and a second coil, and the multiple sub-coils located at the hollow position include a third coil, a fourth coil, a fifth coil, and a sixth coil. Among them, 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.

7. The multi-channel SQUID cryogenic thermometer according to claim 1, characterized in that: Multiple sub-coils of each superconducting gradient coil are electrically connected on-chip through superconducting metal.

8. The multi-channel SQUID cryogenic thermometer according to claim 1, characterized in that: Multi-channel SQUID cryogenic thermometer includes: substrate; A first superconducting layer, located on the substrate; a first insulating layer, located on the first superconducting layer; a second superconducting layer, located on the first insulating layer; a second insulating layer, located on the second superconducting layer; A third superconducting layer located on the second insulating layer; a resistance layer, located on the third superconducting layer; A metal to be tested, located in the multi-channel SQUID low-temperature thermometer, the metal to be tested; A superconducting gradient coil layer, wherein the superconducting gradient coil layer is partially located above the metal to be measured and partially located at a hollow position in the channel SQUID low-temperature thermometer.

9. The multi-channel SQUID cryogenic thermometer according to claim 8, characterized in that: 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.

10. A method for preparing a multi-channel SQUID low-temperature thermometer, characterized in that: include: 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, wherein the first superconducting layer is located on the substrate, the first insulating layer is located on the first superconducting layer, and the second superconducting layer is located 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 for forming a SQUID, a feedback coil for the SQUID, and a bias coil for the SQUID; forming a resistance layer on the third superconducting layer; forming a metal to be tested in the multi-channel SQUID low-temperature thermometer, wherein the metal to be tested is formed above the resistor layer without contact; A superconducting gradient coil layer is formed in the multi-channel SQUID cryogenic thermometer, wherein a portion of the superconducting gradient coil layer is located above the metal to be measured and a portion of the superconducting gradient coil layer is located at a hollow position in the channel SQUID cryogenic thermometer.

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