Superconducting wire single photon detector, method of manufacture and method of superconducting wire temperature detection

Abstract

The application discloses a superconducting wire single-photon detector, a preparation method and a superconducting wire temperature detection method, and relates to the technical field of superconductivity, wherein the superconducting wire single-photon detector comprises a substrate, a superconducting thin film material and a metal electrode, the superconducting thin film material and the metal electrode are arranged on the substrate, the superconducting thin film material forms a nanowire after electron beam lithography treatment, the metal electrode is located at two ends of the superconducting thin film material, and the substrate, the nanowire and the metal electrode are all encapsulated in an encapsulating material.The detector of the application can not only adapt to the low-temperature environment of liquid helium, but also stably generate and send voltage pulses, thereby realizing rapid response and early warning of the superconducting wire quenching.

Description

Technical Field

[0001] This application relates to the field of superconducting technology, and in particular to a method for detecting the temperature of a superconducting wire using a single-photon detector on the superconducting wire. Background Technology

[0002] Cryogenic superconducting wires are wires that exhibit superconductivity at extremely low temperatures (typically liquid helium temperatures, approximately 4.2K or -268.9°C). Currently, commercially available cryogenic superconducting wires include NbTi and Nb3Sn types. NbTi superconducting wires have stable fabrication processes and relatively low costs, leading to their widespread use in equipment such as MRI (Magnetic Resonance Imaging). Nb3Sn superconducting wires have higher critical magnetic fields and are in high demand in fusion reactors (such as the International Thermonuclear Experimental Reactor ITER) and the Large Hadron Collider (LHC). During operation, if temperature fluctuations or magnetic field strength exceed the material's tolerance, the operating current may exceed the critical current, a phenomenon known as quenching failure. After quenching failure, the resistance of the superconducting wire suddenly increases, generating a large amount of heat, which can potentially damage the equipment.

[0003] By detecting the operating temperature of superconducting wires, quenching can be detected in the early stages of temperature changes. The principle is that after a superconducting wire quenches, a region of normal resistance is generated, causing a local temperature rise, which can be monitored by temperature sensors. CN212749213U provides a multi-sensor fusion superconductor quenching detection and early warning system that uses image analysis to determine temperature anomalies. This method can reflect temperature changes in the area to be detected. However, superconducting wires typically operate in a liquid helium environment, and the extremely low temperatures affect the efficiency and accuracy of the image acquisition system. Furthermore, this method struggles to capture weak local temperature rises and early quenching signals, exhibiting slow response speed and insufficient sensitivity. Summary of the Invention

[0004] This application provides a single-photon detector for superconducting wires, a preparation method, and a method for detecting the temperature of superconducting wires, in order to solve the problems of slow response speed and insufficient sensitivity in existing methods for quench warning that use image acquisition and recognition.

[0005] On one hand, embodiments of this application provide a superconducting wire single-photon detector, including a substrate, a superconducting thin film material, and a metal electrode. The superconducting thin film material and the metal electrode are both disposed on the substrate. The superconducting thin film material is formed into a nanowire after being processed by electron beam lithography. The metal electrode is located at both ends of the superconducting thin film material. The substrate, nanowire, and metal electrode are all encapsulated in an encapsulation material.

[0006] On the other hand, embodiments of this application also provide a method for fabricating a superconducting single-photon detector, including: Depositing superconducting thin film materials on a substrate; Electron beam lithography is used to process superconducting thin film materials to form nanowires; Metal electrodes are deposited at both ends of a superconducting thin film material; The substrate, nanowires, and metal electrodes are encapsulated in an encapsulation material.

[0007] On the other hand, embodiments of this application also provide a method for detecting the temperature of a superconducting wire using a single-photon detector, comprising: A superconducting single-photon detector is installed inside a superconducting magnet Dewar using an embedding device. The superconducting magnet Dewar contains a superconducting wire. Use circuitry to connect the superconducting single-photon detector and the signal processing system; The voltage pulses sent by the single-photon detector of the superconducting wire are acquired by the signal processing system. The voltage pulses are processed to obtain the temperature change of the superconducting wire.

[0008] This application proposes a method for detecting temperature changes using a superconducting single-photon detector (SNSPD). An SNSPD is a type of single-photon detector, typically constructed from ultrathin, low-temperature superconducting nanowires. When a photon is absorbed by the superconducting nanowire, a non-superconducting hotspot region is formed. This hotspot region causes localized quenching of the nanowire, creating a resistive region. The energy from this resistive region is transferred to the substrate, restoring the superconducting state. This dynamic process of superconducting state-resistive state-superconducting state is represented in the circuit by a voltage pulse generated across the nanowire. Single-photon detection can be achieved by discriminating this voltage pulse. The SNSPD can detect superconducting quenching for two reasons: First, superconducting wires emit thermal radiation (infrared light). When a superconducting wire quenches, the temperature change causes a change in thermal radiation, which the SNSPD can receive. Second, when a superconducting wire quenches, the temperature rises, causing a corresponding change in the liquid helium environment. The change in the liquid helium flow rate affects the reception of thermal radiation, and the increase in liquid helium temperature affects the superconducting state of the SNSPD itself. Therefore, when the superconducting wire loses its quench, the SNSPD can quickly respond to the temperature change.

[0009] Therefore, the superconducting single-photon detector of this application has the following advantages: 1. The process and structure are very simple: only a single-layer superconducting thin film is required, and the processing of superconducting thin films can be achieved with a single-layer process.

[0010] 2. Simple readout circuit: A high signal-to-noise ratio signal can be obtained by using only a low-noise amplifier at room temperature.

[0011] 3. Strong robustness: As a photodetector, it realizes the conversion of photons into electrical pulses, which can be described as the conversion of optical digital signals into electrical digital signals, and has strong resistance to environmental noise.

[0012] 4. Prepared using low-temperature superconducting materials such as NbN, it can operate in the liquid helium temperature range. The relatively harsh low-temperature liquid helium environment, which is relatively harsh for other quench detection methods, is a necessary condition for the normal operation of SNSPD. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a structural diagram of a superconducting single-photon detector provided in an embodiment of this application.

[0015] Figure 2 The diagram shows the structure of a superconducting magnet that uses a superconducting single-photon detector, as provided in the embodiments of this application.

[0016] Explanation of reference numerals in the attached figures: 1. Superconducting magnet Dewar; 2. Circuit line; 3. Embedded device; 4. Superconducting wire single-photon detector; 4001. Encapsulation material; 4002. Substrate; 4003. Superconducting thin film material; 4004. Metal electrode; 5. Superconducting wire; 6. Liquid helium; 7. Signal processing system. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] Figure 1 This is a schematic diagram of the structure of a superconducting wire single-photon detector provided in an embodiment of this application. The embodiment of this application provides a superconducting wire single-photon detector, including a substrate 4002, a superconducting thin film material 4003, and a metal electrode 4004. Both the superconducting thin film material 4003 and the metal electrode 4004 are disposed on the substrate 4002. The superconducting thin film material 4003 is formed into nanowires after electron beam lithography. The metal electrode 4004 is located at both ends of the superconducting thin film material 4003. The substrate 4002, the nanowires, and the metal electrode 4004 are all encapsulated in an encapsulation material 4001.

[0019] This application also provides a method for fabricating a superconducting single-photon detector, which includes the following steps: S1, deposit superconducting thin film material 4003 on substrate 4002.

[0020] For example, a superconducting thin film material 4003 is deposited using magnetron sputtering technology. The superconducting thin film material can be selected from niobium titanium alloy (NbTi), niobium nitride (NbN), or tungsten silicide (WSi), and the substrate can be selected from sapphire (Al2O3) or silicon (Si). The magnetron sputtering uses argon as the working gas, with the pressure controlled between 0.5 Pa and 2 Pa, the sputtering power is between 100 W and 300 W, the deposition time is between 10 minutes and 30 minutes, and the film thickness is controlled between 5 and 10 nanometers.

[0021] S2 uses electron beam lithography to process superconducting thin film material 4003 to form nanowires.

[0022] For example, this step specifically includes: Electron beam photoresist was spin-coated onto superconducting thin film material 4003. Expose the electron beam photoresist; Electron beam photoresist in the area to be removed on superconducting thin film material 4003 was etched using reactive ion etching technology. The etched electron beam photoresist is developed using a developer to remove the electron beam photoresist and the corresponding area of ​​the superconducting thin film material 4003, thus forming nanowires.

[0023] Specifically, PMMA (polymethyl methacrylate) was used as the electron beam photoresist, with a spin-coating thickness of 200 to 300 nanometers. The exposure dose was 100 μC / cm. 2 Up to 300 μC / cm 2 Excess superconducting material was removed by reactive ion etching (RIE). A mixed solution of MIBK (methyl isobutyl ketone) and IPA (isopropanol) in a volume ratio of 1:3 was used as the developing solution for 60 seconds to form nanowires with widths ranging from 80 nm to 240 nm and lengths ranging from 0.8 mm to 2.4 mm.

[0024] S3, depositing a metal electrode 4004 on superconducting thin film material 4003.

[0025] For example, a metal electrode 4004 is deposited using magnetron sputtering. The metal electrode material is either gold (Au) or silver (Ag). The magnetron sputtering uses argon as the working gas, with a pressure controlled between 0.5 Pa and 2 Pa, a sputtering power of 100 W to 300 W, a deposition time of 20 minutes to 60 minutes, and a metal electrode 4004 thickness controlled to 100-150 nanometers.

[0026] S4, the substrate 4002, nanowires and metal electrodes 4004 are encapsulated in encapsulation material 4001.

[0027] For example, the encapsulation material 4001 is made of low-temperature epoxy resin, and the substrate 4002, nanowires, and metal electrodes 4004 are encapsulated in the encapsulation material 4001 in a vacuum environment. The vacuum degree inside the encapsulation material 4001 is less than 10. -6 Torr.

[0028] This application also provides a method for detecting the temperature of a superconducting wire using the aforementioned single-photon detector, the method comprising: The superconducting single-photon detector 4 is installed inside the superconducting magnet Dewar 1 through the embedding device 3. The superconducting magnet Dewar 1 is equipped with a superconducting wire 5. Use circuit line 2 to connect the superconducting single-photon detector 4 and the signal processing system 7; The voltage pulses sent by the single-photon detector 4 of the superconducting wire are acquired by the signal processing system 7, and the temperature changes of the superconducting wire 5 are obtained by processing the voltage pulses.

[0029] For example, such as Figure 2 As shown, the embedding device 3 is a low-temperature adhesive or mechanical clamp. The circuit wire 2 uses fine gold or silver wire. The internal environment of the superconducting magnet Dewar 1 is liquid helium 6.

[0030] The signal processing system 7 includes a preamplifier, a filter, and a data acquisition card connected in sequence. All three components are powered by a power supply. The preamplifier is an AD8676 with a gain set between 50 and 200. A low-pass filter is used, with a cutoff frequency of 0.5 MHz to 2 MHz. The data acquisition card has a sampling rate of 5 MS / s to 20 MS / s and a resolution of 16 bits. The power supply provides a voltage stability range of ±0.1%.

[0031] Example 1 Step 1: Deposit superconducting thin film material 4003 on substrate 4002 using magnetron sputtering technology.

[0032] The superconducting thin film material 4003 is made of niobium-titanium alloy (NbTi), the substrate 4002 is made of silicon (Si), argon is used as the working gas for magnetron sputtering, the pressure is controlled at 2Pa, the sputtering power is 300W, the deposition time is 30 minutes, and the film thickness is controlled at 10 nanometers.

[0033] Step 2: Define the nanowire structure of the superconducting thin film material 4003 by electron beam lithography.

[0034] PMMA was used as the electron beam photoresist, with a spin coating thickness of 300 nm and an exposure dose of 300 μC / cm.2 Excess superconducting material was removed by reactive ion etching (RIE), and development was performed using a solution with a MIBK:IPA volume ratio of 1:3 for 60 seconds to form a nanowire structure with a width of 240 nm and a length of 2.4 mm.

[0035] Step 3: Deposit metal electrodes 4004 at both ends of the superconducting thin film material 4003 using magnetron sputtering technology.

[0036] The 4004 metal electrode is made of silver (Ag). Argon is used as the working gas in the magnetron sputtering process, with a pressure controlled at 2 Pa, a sputtering power of 300 W, a deposition time of 60 minutes, and an electrode thickness controlled at 150 nm.

[0037] Step 4: Encapsulate the prepared SNSPD in a vacuum environment.

[0038] The encapsulation material 4001 is a low-temperature epoxy resin, and the vacuum degree inside the encapsulation cavity is less than 10. -6 Torr.

[0039] Step 5: Install the SNSPD into the superconducting magnet Dewar 1 using the embedding device 3, and connect it to the external readout circuit using the circuit wire 2.

[0040] The embedding device 3 is a mechanical clamp. The circuit wire 2 uses fine silver wire. The superconducting magnet Dewar 1 contains superconducting wire 5, and the internal environment is liquid helium 6.

[0041] Step 6: Use the signal processing system 7 to process the electrical signal to achieve rapid response and early warning of quench failure.

[0042] The signal processing system 7 consists of a preamplifier, a filter, a data acquisition card, and a power supply. The preamplifier is an AD8676 with a gain of 200. A low-pass filter with a cutoff frequency of 2MHz is selected. The data acquisition card has a sampling rate of 20MS / s and a resolution of 16 bits. The power supply has a voltage stability range of ±0.1%.

[0043] When the operating current of the superconducting magnet continues to increase, the SNSPD detects an increase in signal strength of approximately 15%, and the system immediately triggers an alarm, indicating that the operating temperature of the superconducting wire 5 has changed and that the superconducting wire 5 has experienced local quenching failure.

[0044] Example 2 Step 1: Deposit superconducting thin film material 4003 on substrate 4002 using magnetron sputtering technology.

[0045] The superconducting thin film material is niobium nitride (NbN), the substrate is sapphire (Al2O3), the magnetron sputtering uses argon as the working gas, the pressure is controlled at 1 Pa, the sputtering power is 200 W, the deposition time is 20 minutes, and the film thickness is controlled at 8 nanometers.

[0046] Step 2: Define the nanowire structure of the superconducting thin film material 4003 by electron beam lithography.

[0047] PMMA was used as the electron beam photoresist, and a spin-coating thickness of 250 nm was achieved. The exposure dose was 200 μC / cm. 2 Excess superconducting material was removed by reactive ion etching (RIE), and development was performed using a MIBK:IPA solution with a volume ratio of 1:3 for 60 seconds to form nanowires with a width of 160 nm and a length of 1.6 mm.

[0048] Step 3: Deposit metal electrodes 4004 at both ends of the superconducting thin film material 4003 using magnetron sputtering technology.

[0049] The 4004 metal electrode material uses gold (Au). Magnetron sputtering uses argon as the working gas, with a pressure controlled at 1 Pa, a sputtering power of 200 W, a deposition time of 40 minutes, and a thickness of 120 nm for the 4004 metal electrode.

[0050] Step 4: Encapsulate the prepared SNSPD in a vacuum environment.

[0051] The encapsulation material 4001 is a low-temperature epoxy resin, and the vacuum level inside its encapsulation cavity is less than 10. -6 Torr.

[0052] Step 5: Install the SNSPD into the superconducting magnet Dewar 1 using the embedding device 3, and connect it to the external readout circuit using the circuit wire 2.

[0053] The embedding device 3 is made of low-temperature adhesive. The circuit wire 2 uses fine gold wire. The superconducting magnet Dewar 1 contains superconducting wire 5, and the internal environment is liquid helium 6.

[0054] Step 6: Use the signal processing system 7 to process the electrical signal to achieve rapid response and early warning of quench failure.

[0055] The signal processing system 7 consists of a preamplifier, filter, data acquisition card, power supply, and alarm. The preamplifier uses an AD8676 with a gain of 120. A low-pass filter with a cutoff frequency of 1.5MHz is selected. The data acquisition card has a sampling rate of 15MS / s and a resolution of 16 bits. The power supply has a voltage stability range of ±0.1%.

[0056] When the operating current of the superconducting magnet continues to increase, the SNSPD detects an increase in signal strength of approximately 20%, and the system immediately triggers an alarm, indicating that the operating temperature of the superconducting wire 5 has changed and that the superconducting wire 5 has experienced local quenching failure.

[0057] Example 3 Step 1: Deposit superconducting thin film material 4003 on substrate 4002 using magnetron sputtering technology.

[0058] The superconducting thin film material 4003 is tungsten silicide (WSi), the substrate is sapphire (Al2O3), the magnetron sputtering uses argon as the working gas, the pressure is controlled at 0.5 Pa, the sputtering power is 100 W, the deposition time is 10 minutes, and the film thickness is controlled at 5 nanometers.

[0059] Step 2: Define the nanowire structure of the superconducting thin film material 4003 by electron beam lithography.

[0060] PMMA was used as the electron beam photoresist, and a spin-coating thickness of 200 nanometers was achieved. The exposure dose was 100 μC / cm. 2 Excess superconducting material was removed by reactive ion etching (RIE), and development was performed using a MIBK:IPA solution with a volume ratio of 1:3 for 60 seconds to form nanowires with a width of 80 nm and a length of 0.8 mm.

[0061] Step 3: Deposit metal electrodes 4004 at both ends of the superconducting thin film material 4003 using magnetron sputtering technology.

[0062] The 4004 metal electrode material uses gold (Au). Magnetron sputtering uses argon as the working gas, with a pressure controlled at 0.5 Pa, a sputtering power of 100 W, a deposition time of 20 minutes, and the thickness of the 4004 metal electrode is controlled at 100 nanometers.

[0063] Step 4: Encapsulate the prepared SNSPD in a vacuum environment.

[0064] The encapsulation material 4001 is a low-temperature epoxy resin, and the vacuum degree inside its encapsulation cavity is less than 10. -6 Torr.

[0065] Step 5: Install the SNSPD into the superconducting magnet Dewar 1 using the embedding device 3, and connect it to the external readout circuit using the circuit wire 2.

[0066] The embedding device 3 is made of low-temperature adhesive. The circuit wire 2 uses fine gold wire. The superconducting magnet Dewar 1 contains superconducting wire 5, and the internal environment is liquid helium 6.

[0067] Step 6: Use the signal processing system 7 to process the electrical signal to achieve rapid response and early warning of quench failure.

[0068] The signal processing system 7 consists of a preamplifier, a filter, a data acquisition card, and a power supply. The preamplifier uses an AD8676 with a gain of 50. A low-pass filter with a cutoff frequency of 0.5MHz is selected. The data acquisition card has a sampling rate of 5MS / s and a resolution of 16 bits. The power supply has a voltage stability range of ±0.1%.

[0069] When the operating current of the superconducting magnet continued to increase, the SNSPD detected an increase in signal strength of approximately 18%, and the system immediately triggered an alarm, indicating that the operating temperature of the superconducting wire 5 had changed and that the superconducting wire 5 had experienced a local loss of quench.

[0070] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0071] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A superconducting single-photon detector, characterized in that, The device includes a substrate (4002), a superconducting thin film material (4003), and a metal electrode (4004). The superconducting thin film material (4003) and the metal electrode (4004) are both disposed on the substrate (4002). The superconducting thin film material (4003) is formed into nanowires after being processed by electron beam lithography. The metal electrode (4004) is located at both ends of the superconducting thin film material (4003). The substrate (4002), the nanowires, and the metal electrode (4004) are all encapsulated in an encapsulation material (4001).

2. The method for fabricating the superconducting single-photon detector according to claim 1, characterized in that, include: Superconducting thin film material (4003) is deposited on substrate (4002); The superconducting thin film material (4003) was processed using electron beam lithography to form nanowires; Metal electrodes (4004) are deposited at both ends of the superconducting thin film material (4003). The substrate (4002), the nanowire, and the metal electrode (4004) are encapsulated in an encapsulation material (4001).

3. The preparation method according to claim 2, characterized in that, The superconducting thin film material (4003) and the metal electrode (4004) are deposited using magnetron sputtering technology.

4. The preparation method according to claim 2, characterized in that, The substrate (4002) is made of sapphire or silicon, the superconducting thin film material (4003) is made of niobium-titanium alloy, niobium nitride or tungsten silicide, the metal electrode (4004) is made of gold or silver, and the encapsulation material (4001) is made of low-temperature epoxy resin.

5. The preparation method according to claim 2, characterized in that, The method for processing the superconducting thin film material (4003) using electron beam lithography includes: Electron beam photoresist is spin-coated onto the superconducting thin film material (4003); The electron beam photoresist is exposed; The electron beam photoresist in the area to be removed on the superconducting thin film material (4003) was etched using reactive ion etching technology; The electron beam photoresist after etching is developed using a developer to remove the electron beam photoresist and the corresponding area of ​​the superconducting thin film material (4003) to form the nanowire.

6. The preparation method according to claim 5, characterized in that, The electron beam photoresist is polymethyl methacrylate, and the developer is a mixture of methyl isobutyl ketone and isopropanol in a volume ratio of 1:

3.

7. The preparation method according to claim 2, characterized in that, The substrate (4002), the nanowire, and the metal electrode (4004) are encapsulated in the encapsulation material (4001) in a vacuum environment.

8. A method for detecting the temperature of a superconducting wire using the single-photon detector of claim 1, characterized in that, include: The superconducting single-photon detector (4) is installed inside the superconducting magnet Dewar (1) by means of an embedding device (3), and the superconducting magnet Dewar (1) is provided with a superconducting wire (5). The superconducting single-photon detector (4) and the signal processing system (7) are connected using a circuit line (2); The signal processing system (7) acquires the voltage pulse sent by the single-photon detector (4) of the superconducting wire, processes the voltage pulse, and obtains the temperature change of the superconducting wire (5).

9. The method for detecting the temperature of a superconducting wire according to claim 8, characterized in that, The embedding device (3) is a low-temperature adhesive or a mechanical clamp.

10. The method for detecting the temperature of a superconducting wire according to claim 8, characterized in that, The signal processing system (7) includes a preamplifier, a filter and a data acquisition card connected in sequence, and the preamplifier, the filter and the data acquisition card are all powered by a power supply.

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