Temperature sensing unit and detection device

Abstract

The utility model provides a temperature sensing unit and a detection device. The temperature sensing unit comprises a magnetic material, an antenna substrate, a diamond, a condensing lens, an optical filter, a photoelectric detector and a laser output port. According to the scheme, on the basis of the principle that the magnetic field of the magnetic material can change along with the temperature, the temperature is reversely deduced by measuring the magnetic field change of the magnetic material through the diamond NV color center, and due to the fact that the magnetic field detection sensitivity of the diamond NV color center is extremely high, higher temperature measurement sensitivity can be obtained in a wide temperature range through temperature inversion through the scheme. Meanwhile, the utility model provides a detection device suitable for monitoring the temperature of the cold plate of the dilution refrigerator, and the application feasibility of the NV color center sensing technology in the field is verified.

Description

Technical Field

[0001] This utility model relates to the field of quantum precision measurement, and in particular to a temperature sensing unit and a cold plate temperature detection device for a dilution refrigeration machine. Background Technology

[0002] Cryogenic dilution refrigerators are indispensable core equipment in cutting-edge fields such as modern condensed matter physics, quantum information science, cryogenic electronics, and deep space exploration. Through the phase transition dilution effect of a helium-3 / helium-4 mixture at extremely low temperatures, they can continuously generate and maintain ultra-low temperature environments at the milliKelvin (mK) to microKelvin (μK) levels. In this system, cold plates located at different temperature levels (e.g., 50K, 4K, 0.1K cold plates) constitute the key thermodynamic framework. They not only bear the heavy responsibility of intercepting and dissipating thermal radiation from the room temperature environment, but also serve as direct mounting platforms for experimental samples (such as superconducting quantum bit chips, low-dimensional materials, and high-sensitivity detectors). Therefore, accurate, real-time, and in-situ monitoring of the temperatures of these cold plates is an absolute prerequisite for ensuring the efficient and stable operation of the refrigerator, assessing the system's heat load, and ensuring the reliability of experimental data.

[0003] As an excellent quantum sensing material in recent years, diamond NV color centers not only excel in magnetic field measurement, but also have extremely high accuracy in temperature sensing. Through optical detection magnetic resonance technology, it converts temperature information into precise changes in the zero-field splitting (D) of the ground state energy level of nitrogen-vacancy color centers.

[0004] When considering the application of diamond NV color center sensing technology to the temperature measurement of 50K cold plates in a dilution refrigeration unit, it was found that the diamond NV color center is less sensitive to temperature changes at ultra-low temperatures than at room temperature, due to the low temperature of around 50K. In order to achieve consistent high sensitivity of diamond NV color center temperature sensing in a wide temperature range, this solution is proposed. Utility Model Content

[0005] To achieve the objectives mentioned above and other related objectives, the first aspect of this utility model provides a temperature sensing unit, comprising:

[0006] Magnetic materials;

[0007] An antenna substrate is disposed on the top surface of a magnetic material, and a microwave antenna is plated on the top of the antenna substrate.

[0008] Diamond, containing the NV color center of the ensemble, is mounted in the middle of the top surface of the antenna substrate;

[0009] A focusing lens, positioned above the diamond, is used to concentrate the light emitted from the diamond.

[0010] A filter, positioned above a condenser lens, is used to filter out photofluorescence;

[0011] A photodetector, positioned above the filter, is used to collect photoluminescence;

[0012] The laser output port is located on one side of the diamond. During operation, the excitation light is output from the laser output port and enters from one side of the diamond to excite the NV color center.

[0013] As described above, in the temperature sensing unit, the magnetic field direction of the magnetic material at the diamond is parallel to any of its internal NV axes.

[0014] As described above regarding the temperature sensing unit, the diamond further includes a first side surface, and an NV axis therein is perpendicular to the first side surface.

[0015] As described above, the temperature sensing unit further includes a magnetic shielding cylinder with an opening at the bottom. The magnetic material, antenna substrate, diamond, focusing lens, filter, and photodetector are installed sequentially from bottom to top inside the magnetic shielding cylinder. The magnetic material is filled at the bottom opening of the magnetic shielding cylinder. The side wall of the magnetic shielding cylinder is provided with an optical fiber connector as a laser output port, and the magnetic shielding cylinder is provided with a connection port for the photodetector and microwave antenna.

[0016] As described above regarding the temperature sensing unit, the cover of the magnetic shielding cylinder is further detachable.

[0017] As described above, the temperature sensing unit further includes an inner cylinder disposed on the top surface of the antenna substrate, with a diamond located inside the inner cylinder and a focusing lens disposed on the top of the inner cylinder. The side wall of the inner cylinder is provided with a light passage hole corresponding to the laser output port.

[0018] As described above regarding the temperature sensing unit, further, the bottom of the inner cylinder includes at least one section of cylindrical structure, the inner diameter of which gradually increases from bottom to top.

[0019] To achieve the above and other related objectives, a second aspect of this utility model provides a detection device for detecting the temperature of a cold plate used in a dilution refrigeration machine. The device utilizes the temperature sensing unit as described above, and during operation, a magnetic material is configured to contact the surface of the cold plate to be tested.

[0020] In addition to the detection device described above, the magnetic material is a dilute magnetic CuNi alloy with a Ni content of less than 45%.

[0021] As described above, the photodetector is further described as an avalanche diode.

[0022] As described above, the temperature sensing unit and detection device of this utility model have the following beneficial effects:

[0023] This scheme is based on the principle that the magnetic field of magnetic materials changes with temperature. It uses diamond NV centers to measure the change in the magnetic field of the magnetic material to infer the temperature. Because diamond NV centers have extremely high magnetic field detection sensitivity, this scheme achieves higher temperature measurement sensitivity across a wide temperature range. Furthermore, a detection device suitable for monitoring the temperature of the cold plate in a dilution refrigerator is proposed, verifying the feasibility of applying NV center sensing technology in this field. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the temperature sensing unit.

[0025] Figure 2 The diagram shows the relationship between the crystal orientation of diamond

[111] and the direction of the magnetic field of the magnetic material;

[0026] Figure 3 Four-peak ODMR spectrum;

[0027] Figure 4 This is a schematic diagram of a temperature sensing unit with a magnetically shielded cylinder.

[0028] Figure 5 This is a schematic diagram of one possible structure of the inner cylinder;

[0029] Figure 6 This is a system block diagram of the cold plate inspection device.

[0030] Figure label:

[0031] 1-Temperature sensing unit; 2-Laser module; 3-Microwave module; 4-Data acquisition module; 5-Main unit; 6-Magnetic shielding cylinder; 7-Sample to be tested; 10-Magnetic material; 11-Antenna substrate; 12-Microwave antenna; 13-Diamond; 14-Condensing lens; 15-Filter; 16-Photodetector; 17-Laser output port; 21-532nm laser source; 22-Adjustable attenuator; 23-Acousto-optic modulator; 31-Microwave source; 32-Microwave amplifier; 33-Microwave circulator; 61-Cylinder cover; 62-Cylinder body; 141-Inner cylinder; 611-Connection port. Detailed Implementation

[0032] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification.

[0033] It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of this invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, provided they do not affect the effectiveness or purpose of this invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of this invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of this invention. Example 1

[0034] like Figure 1 As shown, this example proposes a temperature sensing unit 1, which includes a magnetic material 10, an antenna substrate 11, a diamond 13, a condenser lens 14, a filter 15, a photodetector 16, and a laser output port 17.

[0035] In this example, the magnetic material 10 serves as a medium for sensing changes in external temperature and also as a carrier for some components, such as the antenna substrate 11 and the diamond 13. Regarding the magnetic material 10, a magnet with better temperature characteristics is preferred, such as a neodymium iron boron magnet that can be used for measurement at room temperature. Regarding the shape of the magnetic material 10, a cylindrical or square columnar shape is selected in this example. This shape selection is based on a simpler structural design, but in reality, other shapes of magnetic material 10 are also feasible, even irregular shapes.

[0036] In this example, the antenna substrate 11 is disposed on the top surface of the magnetic material 10, and the top of the antenna substrate 11 is plated with a microwave antenna 12. In a specific embodiment, the antenna substrate 11 can be bonded to the magnetic material 10 by adhesive. A microwave antenna of the required shape can be designed on its surface by copper plating technology. An RF transmission line connector is left on one side of the top surface of the antenna substrate 11.

[0037] In this example, diamond 13 contains the NV color center of the ensemble and is mounted in the middle of the top surface of antenna substrate 11. In a specific embodiment, diamond 13 is selected as a cuboid (preferably with dimensions of 200μm*200μm*100μm), and diamond 13 is fixedly connected to antenna substrate 11 by optical adhesive. Diamond 13 containing NV color center will produce red photofluorescence under the illumination of green excitation light with a wavelength of about 532nm. The change of external physical quantity can be calculated by measuring the intensity of photofluorescence.

[0038] In this example, the condenser lens 14 is positioned above the diamond 13 to focus the light emitted from the diamond 13. Since the conversion ratio between the excitation light and photoluminescence is not high, it is necessary to ensure extremely high photoluminescence collection efficiency in order to ensure measurement accuracy. Therefore, it is considered to add a condenser lens 14 to focus the diffused light generated by the diamond 13, so that it can be transmitted to the photodetector 16 with higher efficiency.

[0039] In this example, the filter 15 is positioned above the condenser lens 14 to filter out photofluorescence. The light generated at the diamond 13 includes photofluorescence, excitation light, and stray light. Except for photofluorescence, other wavelengths of light will interfere with the measurement accuracy. Therefore, the filter 15 is needed to filter out light other than photofluorescence and only filter out photofluorescence for collection by the photodetector 16.

[0040] In this example, the photodetector 16 is positioned above the filter 15 and is used to collect photoluminescence. The photodetector 16 converts the fluorescence signal into an electrical signal output. In specific implementations, since the photodetector 16 is installed in the temperature measurement area, it is necessary to select a suitable photodetector 16 according to the actual measurement temperature range to ensure stable operation. For example, in an ultra-low temperature detection environment, an avalanche diode that can operate at ultra-low temperatures can be selected as the photodetector.

[0041] In this example, the laser output port 17 is located on one side of the diamond 13 (as in...). Figure 1 (Located on the left side of diamond 13), during operation, the excitation light is output from the laser output port and enters from one side of diamond 13 to excite the NV color center. Regarding the laser output port 17, its main function is to restrict the incident path of the excitation light. Specifically, it can be a fiber optic connector. The external laser transmits the excitation light through an optical fiber, connects to the fiber optic connector, and finally enters diamond 13 along the desired path. In this scheme, the laser source can be far from the temperature measurement area, resulting in high laser stability. Of course, without considering these conditions, the laser source can be directly located near the diamond 13, with its optical output port directly serving as the laser output port 17.

[0042] When the above embodiment is working, the external temperature affects the magnetic field strength of the magnetic material 10. The temperature-induced magnetic field change can be sensed and obtained through the ultra-high sensitivity of the NV color center to the magnetic field, and the external temperature can be calculated in reverse. Compared with directly using the diamond NV color center to sense the temperature, it can maintain a high temperature measurement sensitivity in a wide temperature range.

[0043] Considering that the aforementioned temperature measurement technique is also based on optically detected magnetic resonance (ODMR) technology, analysis of different ODMR curves reveals that only when the magnetic field direction is parallel or approximately parallel to a certain NV axis, and the corresponding fluorescence microwave peak shape is traced, will better spectral contrast and lower linewidth be obtained. This is beneficial for improving measurement accuracy. Therefore, in some implementation schemes, it is required that the magnetic field direction of the magnetic material 10 at the diamond 13 is parallel to any NV axis within it. The ODMR spectrum obtained under these conditions is shown in the attached figure. Figure 3 As shown.

[0044] Furthermore, considering the significant adjustment difficulty in requiring the magnetic field direction to be parallel to the NV axis, to facilitate achieving this directional requirement, in a preferred design, the diamond containing the NV color center is positioned (see Appendix). Figure 2 The diamond 13 is required to include a first side surface (the top or bottom surface of the diamond in the figure), and an NV axis (i.e., the

[111] crystal direction in the figure) within it is perpendicular to the first side surface. In this diamond structure, an NV axis is perpendicular to a surface of the diamond and has a relatively clear direction indicator. This makes it easier to achieve the parallelism between the direction of the external magnetic field and the NV axis. For example, a cylindrical magnet is provided, and the diamond is placed in the middle of the top surface of the cylindrical magnet, so that the first side surface is in close contact with the top surface of the cylindrical magnet. At this time, the magnetic field lines emitted from the middle of the top surface of the cylindrical magnet are also basically perpendicular to the first side surface, thereby achieving the parallelism or approximately parallelism between the direction of the magnetic field and the NV axis.

[0045] Considering the complex external magnetic fields in some measurement scenarios, and the fact that the temperature measurement in this scheme mainly relies on sensing the changes in the magnetic field of the magnetic material 10 to infer temperature information, it is essential to isolate the influence of external magnetic fields, especially changing magnetic fields, on the measurement results. Therefore, in a preferred design, the temperature sensing unit also includes a magnetic shielding cylinder 6 with an opening at the bottom. The magnetic material 10, antenna substrate 11, diamond 13, condenser lens 14, filter 15, and photodetector 16 are sequentially installed inside the magnetic shielding cylinder 6 from bottom to top, with the magnetic material 10 filling the bottom opening of the magnetic shielding cylinder 6. The side wall of the magnetic shielding cylinder 6 is provided with an optical fiber connector as a laser output port 17, and the magnetic shielding cylinder 6 is provided with a connection port 611 for the photodetector and microwave antenna. For the specific structural design, please refer to the appendix. Figure 4To facilitate structural installation, in the preferred design, the cover of the magnetic shielding cylinder 6 is detachable, consisting of a cover 61 and a cylinder body 62. The connection between the two is designed with corresponding concave and convex embedded parts to ensure the magnetic shielding effect. A further design includes an inner cylinder 141 located on the top surface of the antenna substrate 11. A diamond 13 is located within the inner cylinder 141, and a focusing lens 14 is located at the top of the inner cylinder 141. The side wall of the inner cylinder 141 has a light-passing hole corresponding to the laser output port 17. The design of the inner cylinder 141 not only provides a supporting structure for the focusing lens 14 but also effectively increases the total amount of upward-propagating light. Furthermore, the design of the inner cylinder 141 facilitates the connection of the RF transmission line to the microwave antenna 12. In this design, the filter 15 is directly connected to the bottom surface of the photodetector 16. The size of the photodetector 16 is smaller than the inner diameter of the cover 61, but efforts should be made to ensure that the light focused by the focusing lens 14 fully enters the photodetector 16. The dimensions and distance between the two can be determined through testing.

[0046] To further improve the collection efficiency of photoluminescence, based on the aforementioned inner cylinder design, in a preferred embodiment, the bottom of the inner cylinder 141 is required to include at least one cylindrical structure, the inner diameter of which gradually increases from bottom to top. A specific embodiment is shown in the attached figure. Figure 5 As shown, the inner diameter of the inner cylinder 141 gradually increases from bottom to top, like a rotating parabola. This allows the light generated at the diamond to be transmitted upwards efficiently, thereby improving the fluorescence collection efficiency. Example 2

[0047] This embodiment provides a detection device for detecting the temperature of a cold plate used in a dilution refrigeration unit. It utilizes the temperature sensing unit described above. During operation, a magnetic material is configured to contact the surface of the cold plate being tested. Specifically, as shown in the attached diagram... Figure 6 As shown, it includes a temperature sensing unit 1, a laser module 2, a microwave module 3, a data acquisition module 4, and a host unit 5.

[0048] In this example, the temperature sensing unit 1 is the same as the temperature sensing unit introduced in Embodiment 1. It is installed on the sample to be tested 7 inside the dilution refrigerator. The sample to be tested 7 is the cold plate (temperature about 50K). The cold plate is in contact with the magnetic material 10. The temperature change affects the magnetic field strength of the magnetic material 10. The temperature information is then inferred by sensing the change of the magnetic field through the NV color center.

[0049] In this example, laser module 2 is used to output excitation light. Laser module 2 is located outside the dilution refrigerator, and the excitation light is transmitted via optical fiber to the temperature sensing unit 1 inside the refrigerator. For example, for NV color centers, a 532nm laser is generally used as the excitation light; therefore, the laser module should include a 532nm laser source 21. Since the dilution refrigerator has extremely high requirements for temperature control, considering that the excitation light used in this solution may cause a temperature rise in the cold plate, to suppress this effect, a preferred solution requires the laser module to include an adjustable attenuator 22, which is used to adjust the excitation light power, such as down to below 100μW. By reducing the power of the excitation light, the temperature rise effect of the excitation light on the cold plate is greatly reduced. In another solution, an acousto-optic modulator 23 can also be set in the laser module to control the output pulsed excitation light. In this example, pulsed light is used for temperature detection, reducing the total energy input of the excitation light. Of course, both solutions can coexist, doubly suppressing the temperature rise effect of the excitation light on the cold plate.

[0050] In this example, microwave module 3 is used to output microwave signals to temperature sensing unit 1. The microwave signals enter microwave antenna 12 and eventually form a microwave field radiating diamond 13. For example, the microwave signal is a swept frequency signal with a frequency between approximately 2.8 GHz and 2.9 GHz. For example, microwave module 3 includes microwave source 31, microwave amplifier 32, and microwave circulator 33. The initial microwave signal output by microwave source 31 first passes through microwave amplifier 32 and then microwave circulator 33 before being output.

[0051] In this example, the data acquisition module 4 is used to acquire the electrical signals generated by the photodetector 16 and transmit them to the host 5; for example, the data acquisition module 4 is an FPGA; wherein, the host 5 is used for at least human-computer interaction, fluorescent electrical signal processing and microwave-laser control.

[0052] In this example, in order to achieve the requirement that the magnetic material 10 is in contact with the surface of the cold plate under test, a fixed connection structure (not shown in the figure) is preferably designed to fix the temperature sensing unit and the surface of the cold plate, thereby achieving the requirement that the magnetic material 10 is in contact with the surface of the cold plate under test.

[0053] Considering that the temperature sensing unit 1 in this example is used in ultra-low temperature measurement scenarios, different magnetic materials have different magnetic field strain coefficients for temperature. In order to obtain higher temperature measurement sensitivity, it is better to use magnetic materials with higher temperature coefficients in ultra-low temperature environments. Based on this, in a specific embodiment, the magnetic material is selected as a dilute magnetic CuNi alloy with a Ni content of less than 45%, such as Cu60Ni40. This is because when the Ni content in such magnetic materials is lower than the threshold for forming long-range ferromagnetic order, although the material as a whole does not exhibit ferromagnetism, Ni-rich ferromagnetic nanoclusters will be formed inside. These clusters have very low "local Curie temperatures", and magnetic abrupt changes will also occur in their vicinity, thereby generating extremely high temperature coefficients. This method is suitable for high-sensitivity detection at ultra-low temperatures.

[0054] Considering that ordinary photodiodes usually fail due to the carrier "freezing" effect in ultra-low temperature environments such as 50K (approximately -223℃), it is necessary to select a photodetector in order to ensure the effective operation of the equipment. In this solution, in one preferred embodiment, the photodetector is an avalanche diode, which can effectively meet the requirements of ultra-low temperature detection environment.

[0055] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A temperature sensing unit, characterized by, Include: Magnetic materials; An antenna substrate is disposed on the top surface of a magnetic material, and a microwave antenna is plated on the top of the antenna substrate. Diamond, containing the NV color center of the ensemble, is mounted in the middle of the top surface of the antenna substrate; A focusing lens, positioned above the diamond, is used to concentrate the light emitted from the diamond. A filter, positioned above a condenser lens, is used to filter out photofluorescence; A photodetector, positioned above the filter, is used to collect photoluminescence; The laser output port is located on one side of the diamond. During operation, the excitation light is output from the laser output port and enters from one side of the diamond to excite the NV color center.

2. The temperature sensing unit of claim 1, wherein, The magnetic field direction of the magnetic material at the diamond is parallel to any of its internal NV axes.

3. The temperature sensing unit as described in claim 2, characterized in that, The diamond includes a first side surface, and an NV axis therein is perpendicular to the first side surface.

4. The temperature sensing unit of claim 1, wherein, It also includes a magnetic shielding cylinder with an opening at the bottom. The magnetic material, antenna substrate, diamond, focusing lens, filter and photodetector are installed in the magnetic shielding cylinder from bottom to top. The magnetic material is filled at the bottom opening of the magnetic shielding cylinder. The side wall of the magnetic shielding cylinder is provided with an optical fiber connector as a laser output port. The magnetic shielding cylinder is provided with a connection port for the photodetector and microwave antenna.

5. The temperature sensing unit of claim 4, wherein, The cap of the magnetic shielding cylinder is removable.

6. The temperature sensing unit of claim 4, wherein, It also includes an inner cylinder located on the top surface of the antenna substrate, with a diamond located inside the inner cylinder and a focusing lens located on the top of the inner cylinder. The side wall of the inner cylinder has a light-passing hole corresponding to the laser output port.

7. The temperature sensing unit of claim 6, wherein, The bottom of the inner cylinder includes at least one section of cylindrical structure, the inner diameter of which gradually increases from bottom to top.

8. A detecting device for detecting a temperature of a cold plate for a dilution refrigerator, characterized by, It employs a temperature sensing unit as described in any one of claims 1-7, wherein, during operation, a magnetic material is configured to contact the surface of the cold plate to be tested.

9. The detection device of claim 8, wherein, The magnetic material is a dilute magnetic CuNi alloy with a Ni content of less than 45%.

10. The detection device of claim 8, wherein, The photodetector is an avalanche diode.

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