Single-probe fully-encapsulated NV quantum magnetic field detection device

Abstract

A single-probe fully-encapsulated NV quantum magnetic field detection device relates to the technical field of quantum precision measurement, and particularly relates to a single-probe fully-encapsulated NV quantum magnetic field detection device.The whole adopts an axial coaxial layered and modular integrated structure, and integrates an optical excitation system, a microwave control system, a fluorescence acquisition and signal processing system, a multi-stage vibration reduction and heat insulation structure, a magnetic shielding and magnetic flux orientation structure and a probe protection and installation structure in a single exposed probe.The device only sets a magnetic field sensing window at one end close to a measured bearing, and the rest directions are closed or attenuated through a high magnetic permeability magnetic shielding structure, so that a one-way selective response to a target direction magnetic field is formed at a structural level.The optical system, the microwave system, the quantum magnetic sensing chip, the signal processing circuit and the protection structure are integrated in the single exposed probe, and the limited installation space of a high-speed train is adapted.

Description

Technical Field

[0001] This invention relates to the field of quantum precision measurement technology, specifically to a single-probe fully encapsulated NV quantum magnetic field detection device. Background Technology

[0002] In the high-speed train operating environment, the bearing area is simultaneously affected by strong mechanical vibration, continuous temperature rise and temperature gradient changes, as well as the superposition of multiple sources of stray magnetic fields such as traction current, motor magnetic field and geomagnetic field.

[0003] Diamond NV Center's quantum magnetic sensing technology has the capability to detect magnetic fields at the nanotesla level. Currently, those skilled in the art have achieved highly sensitive detection of extremely weak magnetic field changes under laboratory conditions using Diamond NV Center's quantum magnetic sensing technology. However, laboratory detection relies on low vibration, constant temperature, and controllable magnetic environments. The magnetoelastic effect caused by early damage to high-speed train bearings is only representative under actual load, speed, and vibration coupling conditions. If the bearing is disassembled for offline testing, not only will the original stress state be destroyed, but the dynamic magnetic disturbance characteristics during operation cannot be reproduced, making it difficult to achieve early warning.

[0004] Because its measurement mechanism is based on the precise modulation and readout of the spin level resonance frequency, it is highly sensitive to mechanical strain disturbances, temperature drift, and changes in the background magnetic field. When the NV chip is directly exposed near the bearing, external vibrations are transmitted to the diamond lattice through structural coupling, causing spin level broadening and fluorescence signal jitter; temperature changes cause the zero-field splitting parameter to drift, resulting in a shift in the resonance frequency; and the amplitude of the ambient stray magnetic field is usually much higher than the weak magnetic disturbances caused by early bearing damage, which can easily cause signal submersion.

[0005] Existing technologies for addressing vibration or temperature issues often rely on algorithm compensation or single vibration reduction measures. However, frequency drift and magnetic field disturbance in quantum magnetic measurements are equivalent in the signal dimension, and it is difficult to distinguish between thermal drift and real magnetic signals using only back-end algorithms. For magnetic interference issues, simple shielding or increased sensitivity are usually employed. However, a single shielding structure cannot suppress the ambient magnetic field while maintaining selective enhancement of weak magnetic flux in a specific direction. Summary of the Invention

[0006] To address the aforementioned problems, the purpose of this invention is to propose a single-probe, fully encapsulated NV quantum magnetic field detection device. While ensuring high sensitivity in quantum measurements, it also possesses excellent resistance to vibration, temperature drift, and magnetic field direction selectivity, thereby achieving highly reliable online monitoring of early bearing damage.

[0007] The device includes: The device is integrated inside a single detection probe, with the end of the device closer to the bearing being tested as the lower end and the end farther from the bearing being tested as the upper end. The device is arranged sequentially from top to bottom along the central axis of the detection probe: a signal output and system interface module, a fluorescence photoelectric conversion and signal processing module, a multi-physics field isolation module, an NV quantum magnetic sensing chip assembly, and a probe end protection and installation module. Between the fluorescence photoelectric conversion and signal processing module and the multi-physics field isolation module, the microwave control module and the optical excitation and fluorescence acquisition module are positioned side by side via a non-magnetic bracket. The device also includes a magnetic shielding and magnetic flux orientation module, which surrounds the NV quantum magnetic sensing chip assembly and forms a circular magnetic flux opening only at one end near the bearing being tested. The device also includes an external detection system and a power supply.

[0008] Furthermore, the operation of the device includes the following steps: S1. The external detection system generates a control signal, which is output to the fluorescence photoelectric conversion and signal processing module through the signal output and system interface module. S2, the fluorescence photoelectric conversion and signal processing module transmits the control signal to both the microwave control module and the optical excitation and fluorescence acquisition module. S3. The microwave control module generates a microwave signal according to the control signal and outputs it to the NV quantum magnetic sensing chip assembly. The optical excitation and fluorescence acquisition module generates excitation light according to the control signal and outputs it to the NV quantum magnetic sensing chip assembly. The S4 and NV quantum magnetic sensing chip components receive microwave signals, excitation light, and magnetic field signals from the bearing under test, generating a mixed fluorescence signal. S5. The mixed fluorescence signal is converted into a coupled fluorescence signal by the optical excitation and fluorescence acquisition module; S6. The coupled fluorescence signal is processed by the fluorescence photoelectric conversion and signal processing module to obtain the detection signal; S7. The detection signal is then output to the external detection system via the signal output and system interface module.

[0009] Furthermore, the signal output and system interface module includes: a sealed electrical connector and a shielded wire. One end of the sealed electrical connector is connected to the power supply through the shielded wire; the other end is connected to an external detection system through the shielded wire to receive control signals and output detection signals.

[0010] Furthermore, the fluorescence photoelectric conversion and signal processing module includes: a photodiode, a transimpedance amplifier, and a high-frequency low-noise PCB; The coupled fluorescent signal is processed by the fluorescence photoelectric conversion and signal processing module to obtain the detection signal. Specifically, the photodiode receives the coupled fluorescent signal and converts it into an electrical signal. The electrical signal is then converted into a voltage signal by a transimpedance amplifier. The voltage signal is then processed by a low-pass filter and phase-locked synchronous demodulation circuit in a high-frequency low-noise PCB to obtain the detection signal.

[0011] Furthermore, the microwave control module includes: a microwave signal source, a voltage-controlled oscillator, a power regulation circuit, a loop microwave antenna, and an impedance matching unit; The microwave control module generates a microwave signal according to the control signal and outputs it to the NV quantum magnetic sensing chip assembly. Specifically, the microwave signal source receives the control signal and outputs a radio frequency reference signal. The voltage-controlled oscillator outputs a carrier signal according to the radio frequency reference signal. The power adjustment circuit outputs a radio frequency signal according to the carrier signal. The impedance matching unit outputs a matched radio frequency signal according to the radio frequency signal. The loop microwave antenna radiates the microwave signal to the NV quantum magnetic sensing chip assembly according to the matched radio frequency signal to drive the NV quantum magnetic sensing chip assembly to resonantly transition.

[0012] Furthermore, the optical excitation and fluorescence acquisition module includes: a semiconductor laser, a quartz collimating lens, an optical fiber coupling structure, and a bandpass filter; the bandpass filter is disposed in the optical path between the optical fiber coupling structure and the fluorescence photoelectric conversion and signal processing module. The optical excitation and fluorescence acquisition module generates excitation light according to the control signal and outputs it to the NV quantum magnetic sensing chip assembly. Specifically, the semiconductor laser receives the control signal and outputs initial excitation light. The quartz collimating lens outputs a collimated beam according to the initial excitation light. The fiber optic coupling structure outputs excitation light transmitted through the fiber optic cable according to the collimated beam. The excitation light transmitted through the fiber optic cable is then filtered by a bandpass filter to remove stray light and background scattered light before being output to the NV quantum magnetic sensing chip assembly. The mixed fluorescence signal is converted into a coupled fluorescence signal by the optical excitation and fluorescence acquisition module. Specifically, the mixed fluorescence signal is filtered by a bandpass filter to remove residual excitation light and background scattered light to obtain a filtered fluorescence signal. The filtered fluorescence signal is then coupled by an optical fiber coupling structure to obtain a coupled fluorescence signal, which is then transmitted to the fluorescence photoelectric conversion and signal processing module.

[0013] Furthermore, the multi-physics isolation module includes: a fluororubber damping layer, a ceramic thermal insulation support component, and a non-magnetic elastic metal frame; In the multi-physics isolation module, a non-magnetic elastic metal frame serves as the outer support structure, fixed to the inner wall of the detection probe, with a fluororubber damping layer attached to its inner side; a ceramic thermal insulation support is embedded within the fluororubber damping layer. Multiphysics isolation modules are used to attenuate external mechanical vibrations, isolate temperature gradients, and block non-target coupling of magnetic fields along the structural path; The multi-physics isolation module is clamped and fixed between the non-magnetic bracket and the magnetic shield and magnetic flux orientation module.

[0014] Furthermore, the magnetic shielding and flux orientation module includes: a high permeability alloy shielding layer, an asymmetric flux orientation backplate, and a non-magnetic support structure; A non-magnetic support structure serves as the mounting base and is fixed to the inner wall of the detection probe. A high permeability alloy shielding layer is assembled inside the non-magnetic support structure. An asymmetric magnetic flux orientation backplate is installed at the bottom of the high permeability alloy shielding layer and on the side closest to the bearing under test. Together with the high permeability alloy shielding layer, they form a semi-enclosed cavity. The high permeability alloy shielding layer only forms a circular magnetic flux opening at the end closest to the bearing under test. The thickness of the asymmetric flux orientation backplate is non-uniformly distributed circumferentially, being thinnest on the side closest to the central axis of the probe and thickest on the side furthest from the central axis of the probe. The magnetic shielding and flux orientation module is used to shield stray magnetic fields in non-target directions and guide the magnetic field signal in the direction of the bearing under test into the NV quantum magnetic sensing chip component area.

[0015] Furthermore, the NV quantum magnetic sensing chip assembly includes: an NV central functional layer and an aluminum nitride ceramic substrate; The NV central functional layer is obtained by ion implantation to form a nitrogen vacancy structure on a type IIa single crystal diamond substrate, followed by annealing. The NV quantum magnetic sensing chip assembly receives microwave signals, excitation light, and magnetic field signals from the bearing under test, generating a mixed fluorescence signal. Specifically, under the combined action of excitation light, microwave signals, and magnetic field signals from the bearing under test, the electron spin of the NV central functional layer undergoes resonant transition, and Zeeman splitting occurs simultaneously, generating a mixed fluorescence signal. The NV central functional layer is fixed on an aluminum nitride ceramic base and is threaded to the inner wall of the detection probe via a non-magnetic structural component.

[0016] Furthermore, the probe end protection and installation module includes: a ceramic end cap, a sealing ring, and a flange structure; The probe end protection and installation module provides mechanical protection, dust protection, moisture protection, and installation positioning functions; The probe end protection and installation module is fixed at the end of the detection probe that is close to the bearing being tested.

[0017] The beneficial effects of the method described in this invention are as follows: (1) This invention utilizes an NV quantum magnetic sensing chip assembly combined with fluorescence photoelectric conversion and lock-in amplification signal processing techniques. Based on the NV color center optical detection magnetic resonance principle, a microwave control module drives the NV center electron spin to resonantly transition, resulting in a linear response of fluorescence intensity to magnetic field changes. A transimpedance amplifier and a high-frequency, low-noise PCB perform low-noise amplification, bandpass filtering, and demodulation processing synchronized with the microwave modulation frequency on the fluorescence signal, suppressing the system's background noise to below 1 nT / √Hz. This enables highly sensitive detection of nanotesla-level weak magnetic anomaly signals generated by early micro-wear and fatigue cracks in bearings, significantly improving defect identification capabilities. It can achieve highly sensitive detection of nanotesla-level magnetic field changes, significantly improving the ability to identify early bearing defects.

[0018] (2) This invention uses a magnetic shielding and magnetic flux orientation module, based on the principle of low magnetic reluctance bypass of magnetic lines of force by a high permeability alloy (1J85), to form a shielding effect of ≥40dB against stray magnetic fields in the environment; at the same time, it adopts the non-uniform thickness distribution structure of the asymmetric magnetic flux orientation backplate (PC-5AS) to guide the target magnetic flux in the bearing direction to converge along the axial direction to the sensitive area of ​​the NV chip, thereby improving the axial detection sensitivity by 3 to 5 times; the synergistic mechanism of magnetic flux selectivity enhancement and environmental suppression makes its stray magnetic field suppression capability significantly better than that of traditional Hall and magnetoresistive sensing schemes.

[0019] (3) This invention uses a multi-physics field isolation module to convert mechanical vibration energy in the 20Hz–5kHz frequency band into heat energy based on the high molecular internal energy dissipation principle of fluororubber damping layer (FKM-70), with a vibration transmissibility ≤0.1. Combined with the micro-deformation buffer of titanium alloy TC4 elastic frame and the low thermal conductivity insulation of alumina ceramic (Al2O3-995) (thermal resistance ≥1K / W), it effectively isolates the influence of temperature gradient on the spectral line drift of NV chip, thereby ensuring that quantum measurement maintains stable output under the strong vibration and wide temperature variation conditions of high-speed trains, and maintains stable output in the 20Hz–5kHz vibration frequency band, adapting to the operating conditions of high-speed trains.

[0020] (4) This invention integrates all functional units such as signal output, photoelectric conversion, microwave control, optical excitation, physical field isolation, magnetic sensing, magnetic shielding, and end protection into a single probe housing of Φ22mm×120mm by means of fully encapsulated single probe integrated design technology, based on the principle of 8 functional modules stacked in sequence along the axial direction and threaded connection fixing. It adopts standard flange interface and sealing ring structure to realize direct replacement installation with existing bearing seat detection holes, without additional space modification or complex debugging, and has IP67 protection and long-term maintenance-free characteristics, which is suitable for long-term reliable operation in existing train online monitoring systems. Attached Figure Description

[0021] Figure 1 This is a structural diagram of the device described in this invention; Figure 2 This is a flowchart of the method described in this invention. Detailed Implementation

[0022] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This embodiment provides a single-probe fully encapsulated NV quantum magnetic field detection device. The present invention provides a single-probe fully encapsulated NV quantum magnetic field detection device, which adopts an axial coaxial layered and modular integrated structure, integrating an optical excitation system, a microwave control system, a fluorescence acquisition and signal processing system, a multi-level vibration reduction and heat insulation structure, a magnetic shielding and magnetic flux orientation structure, and a probe protection and installation structure into a single exposed probe.

[0024] The device has a magnetic field sensing window at one end near the bearing being tested, while the other directions are closed or attenuated by a high-permeability magnetic shielding structure, thereby forming a "one-way selective response" to the magnetic field in the target direction at the structural level.

[0025] During operation, the optical excitation module provides excitation light to the NV quantum magnetic sensing chip; the microwave control module generates a local microwave magnetic field in the chip area to drive the NV central spin resonance; the NV chip outputs a fluorescence signal related to the magnetic field change; after optical filtering and photoelectric conversion, the fluorescence is amplified, filtered and synchronously demodulated by the signal processing module, and then output to the external monitoring system through the signal interface module to realize real-time analysis and remote early warning of the bearing status.

[0026] like Figure 1 As shown, the device is integrated inside a single detection head, and the detection head is surrounded by a cylindrical shell with a diameter of Φ22mm and a length of 120mm. The device has the end closer to the bearing being tested as the lower end and the end farther away from the bearing being tested as the upper end. The device is arranged sequentially from top to bottom along the central axis of the detection probe: a signal output and system interface module, a fluorescence photoelectric conversion and signal processing module, a multi-physics field isolation module, an NV quantum magnetic sensing chip assembly, and a probe end protection and mounting module; each module is coaxially arranged and connected by non-magnetic structural components. Between the fluorescence photoelectric conversion and signal processing module and the multi-physics field isolation module, the microwave control module and the optical excitation and fluorescence acquisition module are positioned side by side via a non-magnetic bracket. The device also includes a magnetic shielding and flux orientation module, which surrounds the NV quantum magnetic sensing chip assembly, forming a circular flux opening only at the end near the bearing under test. This opening is circular with a diameter of Φ5±0.1mm. This opening size is determined based on the spatial frequency characteristics of the defective magnetic field in the bearing under test and the effective sensitive area of ​​the NV chip (typically a circular area with a diameter of Φ3mm): the opening diameter is slightly larger than the sensitive area, ensuring that magnetic flux from the bearing direction fully covers the NV chip and couples into it; simultaneously, the smaller opening restricts the entry path of stray magnetic fields from non-target directions. Combined with the shielding effect of the magnetic shielding layer, this achieves selective enhancement of magnetic flux in the bearing direction and spatial filtering of the background magnetic field, improving the signal-to-noise ratio and detection directivity.

[0027] Within the device, the radial dimension of each module does not exceed Φ18mm, and the total axial assembly height is 110mm. Through a compact and integrated layout, the entire device can be directly embedded into the reserved detection hole of the existing bearing housing without additional structural modifications, thus achieving a high-sensitivity quantum magnetic sensing function within a limited space.

[0028] The device also includes an external detection system and a power supply.

[0029] When the device is in operation, the optical excitation module emits excitation light, which is then collimated through a collimation structure and irradiated into the NV central functional layer of the NV quantum magnetic sensing chip, causing the NV center to enter an excited state. The microwave control module generates a frequency-tunable microwave magnetic field in the chip region. When the microwave frequency matches the spin level splitting frequency of the NV center, an optical detection magnetic resonance phenomenon occurs at the NV center, and its fluorescence intensity or fluorescence spectrum changes measurably with the change of the external magnetic field.

[0030] The magnetic field change from the bearing direction is preferentially guided to the NV chip area by the flux orientation module, while stray magnetic fields from other directions are attenuated by a high-permeability shielding layer. The fluorescence signal output by the NV chip is converted into an electrical signal by the photodetector after the excitation light is removed by the optical filtering module. Then, it undergoes transimpedance amplification, filtering, and synchronous demodulation in the signal processing module, and finally outputs a detection signal proportional to the bearing magnetic field change to the external monitoring system.

[0031] like Figure 2 As shown, the operation of the device includes the following steps: S1. The external detection system generates a control signal, which is output to the fluorescence photoelectric conversion and signal processing module through the signal output and system interface module. S2, the fluorescence photoelectric conversion and signal processing module transmits the control signal to both the microwave control module and the optical excitation and fluorescence acquisition module. S3. The microwave control module generates a microwave signal according to the control signal and outputs it to the NV quantum magnetic sensing chip assembly. The optical excitation and fluorescence acquisition module generates excitation light according to the control signal and outputs it to the NV quantum magnetic sensing chip assembly. The S4 and NV quantum magnetic sensing chip components receive microwave signals, excitation light, and magnetic field signals from the bearing under test, generating a mixed fluorescence signal. S5. The mixed fluorescence signal is converted into a coupled fluorescence signal by the optical excitation and fluorescence acquisition module; S6. The coupled fluorescence signal is processed by the fluorescence photoelectric conversion and signal processing module to obtain the detection signal; S7. The detection signal is then output to the external detection system via the signal output and system interface module.

[0032] The signal output and system interface module includes: a sealed electrical connector, a shielded cable (multi-layer shielded twisted pair or coaxial cable), a PTFE insulation layer, and a non-magnetic metal housing. One end of the sealed electrical connector is connected to the power supply through the shielded cable. The lasers in the signal output and system interface module, the fluorescence photoelectric conversion and signal processing module, the microwave control module, and the optical excitation and fluorescence acquisition module are all connected to the power supply through the optical excitation and fluorescence acquisition module.

[0033] The other end is connected to an external detection system via a shielded wire to receive control signals and output detection signals; The shielded wire has a PTFE insulation layer inside, which is used for electrical insulation and impedance stabilization between the conductor and the shielding layer.

[0034] In this embodiment, the enclosed electrical connector is preferably the LEMO FGG.1B.304.CLAD52 model, which has an IP68 protection rating and vibration resistance.

[0035] The signal output and system interface module is connected to the inner wall of the detection probe via a non-magnetic metal housing and a threaded (or snap-fit) connection.

[0036] In this embodiment, the non-magnetic metal shell material is 6061-T6 aluminum alloy or 316L low magnetic permeability stainless steel. Fine thread is used in conjunction with conductive washers to form a continuous electromagnetic shielding structure and improve vibration resistance reliability.

[0037] The signal output and system interface module can realize power input, control signal input and detection signal output, and form an electromagnetic shielding structure with the internal signal ground (electrical ground) through a non-magnetic metal shielding shell to suppress external electromagnetic noise coupling.

[0038] The fluorescence photoelectric conversion and signal processing module includes: a photodiode (or avalanche photodiode), a transimpedance amplifier, a high-frequency low-noise PCB, and a non-magnetic metal shielding cavity; The output terminal of the photodiode is electrically connected to the input terminal of the transimpedance amplifier; the output terminal of the transimpedance amplifier is electrically connected to the signal conditioning circuit on the high-frequency, low-noise PCB. In this embodiment, the photodiode is a Hamamatsu S5973, the transimpedance amplifier is an ADIADA4817-1, and the high-frequency, low-noise PCB uses Rogers RO4350B board material. The photocurrent is converted into a voltage signal by the transimpedance amplifier and then processed by the low-pass filter and phase-locked loop synchronous demodulation circuit integrated in the PCB to improve the signal-to-noise ratio and suppress laser intensity noise.

[0039] The coupled fluorescent signal is processed by the fluorescence photoelectric conversion and signal processing module to obtain the detection signal. Specifically, the photodiode receives the coupled fluorescent signal and converts it into an electrical signal. The electrical signal is then converted into a voltage signal by a transimpedance amplifier. The voltage signal is then processed by a low-pass filter and phase-locked synchronous demodulation circuit in a high-frequency low-noise PCB to obtain the detection signal. The fluorescence photoelectric conversion and signal processing module is connected to the system interface module via a ribbon cable and signal output.

[0040] The fluorescence photoelectric conversion and signal processing module is threadedly connected to the inner wall of the detection probe through a non-magnetic metal shielding cavity, which is made of aluminum alloy 6061.

[0041] The outer wall of the non-magnetic metal shielding cavity is provided with a standard metric thread (e.g., M18×1), and the inner wall of the detection probe is provided with a matching internal thread at the corresponding position. During installation, the shielding cavity is screwed into the threaded hole on the inner wall of the probe, and axial positioning and locking are achieved through the stepped surface at the bottom of the thread or the elastic washer. This connection method simultaneously achieves mechanical fixation, grounding conduction and electromagnetic shielding of the module.

[0042] The microwave control module includes: a microwave signal source, a voltage-controlled oscillator, a power regulation circuit, a loop microwave antenna (or copper microstrip line), and an impedance matching unit; The output of the microwave signal source is connected to the reference input of the voltage-controlled oscillator; the RF output of the voltage-controlled oscillator is connected to the input of the power regulation circuit; the output of the power regulation circuit is connected to the input of the impedance matching unit; the output of the impedance matching unit is connected to the feed port of the loop microwave antenna; the loop microwave antenna is arranged around the NV quantum magnetic sensing chip assembly.

[0043] The microwave control module generates a microwave signal according to the control signal and outputs it to the NV quantum magnetic sensing chip assembly. Specifically, the microwave signal source receives the control signal and outputs a radio frequency reference signal. The voltage-controlled oscillator outputs a carrier signal according to the radio frequency reference signal. The power adjustment circuit outputs a radio frequency signal according to the carrier signal. The impedance matching unit outputs a matched radio frequency signal according to the radio frequency signal. The loop microwave antenna radiates the microwave signal to the NV quantum magnetic sensing chip assembly according to the matched radio frequency signal to drive the NV quantum magnetic sensing chip assembly to resonantly transition.

[0044] In this embodiment, the microwave signal source is a DSG5206 microwave signal generator, the voltage-controlled oscillator is a VCO core integrated using 65-nm CMOS technology, the power adjustment circuit is a programmable power gain control unit integrated into an ASIC, the loop microwave antenna is an aluminum nitride (AlN) substrate loop antenna, and the impedance matching unit is a multi-section Chebyshev impedance transformer balun structure.

[0045] The microwave control module is based on the photodetector magnetic resonance effect of the NV color center. It generates a microwave magnetic field with precise frequency and stable power in the NV chip region to drive the resonant transition of the electron spin at the NV center and realize coherent control of the spin state.

[0046] A microwave signal source provides a high-stability frequency reference; a voltage-controlled oscillator generates a carrier signal of 2.87 GHz ± Δf, where f ranges from ±5 MHz to ±20 MHz in this embodiment; a power regulation circuit controls the stable output of microwave power; an impedance matching unit achieves broadband impedance matching and reduces reflection loss; and a loop microwave antenna efficiently radiates microwave energy to the NV chip area, forming a uniform microwave magnetic field.

[0047] Through the above collaborative work, this module can achieve the following technical effects: (1) Supports ODMR measurements from zero magnetic field to high bias magnetic field; (2) With a pull-down ratio of 6.17~8.06 MHz at 1W input power, the spin control speed is improved; (3) The aluminum nitride substrate antenna enhances the fluorescence signal by 2 times, reduces the ODMR bandwidth by 33%, and increases the detection sensitivity from 8.7 nT / Hz¹ / ² to 2.9 nT / Hz¹ / ². (4) Compact integration, adapting to the limited installation space of high-speed trains.

[0048] The optical excitation and fluorescence acquisition module includes: a semiconductor laser (or a high-stability LED), a quartz collimating lens, an optical fiber coupling structure, and a bandpass filter; The semiconductor laser's output port is aligned with a quartz collimating lens; the output end of the quartz collimating lens is connected to the input end of the fiber optic coupling structure; the output fiber end face of the fiber optic coupling structure faces the NV quantum magnetic sensing chip assembly; a bandpass filter is placed in the optical path between the fiber optic coupling structure and the fluorescence photoelectric conversion and signal processing module.

[0049] In this embodiment, the semiconductor laser is a Cobolt 05-01 series 532nm laser, the quartz collimating lens is a 74-UV aspherical quartz collimating lens, the fiber coupling structure is an F-CPL-532 Y-type quartz fiber coupler, and the bandpass filter is a FELH0650 650nm long-pass filter.

[0050] The optical excitation and fluorescence acquisition module is used to provide excitation light to the NV chip and efficiently collect fluorescence signals, while separating the excitation light and fluorescence spectra.

[0051] The optical excitation and fluorescence acquisition module generates excitation light according to the control signal and outputs it to the NV quantum magnetic sensing chip assembly. Specifically, the semiconductor laser receives the control signal and outputs initial excitation light. The quartz collimating lens outputs a collimated beam according to the initial excitation light. The fiber optic coupling structure outputs excitation light transmitted through the fiber optic cable according to the collimated beam. The excitation light transmitted through the fiber optic cable is then filtered by a bandpass filter to remove stray light and background scattered light before being output to the NV quantum magnetic sensing chip assembly (generally, no filter processing is required). The mixed fluorescence signal is converted into a coupled fluorescence signal by the optical excitation and fluorescence acquisition module. Specifically, the mixed fluorescence signal is filtered by a bandpass filter to remove residual excitation light and background scattered light to obtain a filtered fluorescence signal. The filtered fluorescence signal is then coupled by an optical fiber coupling structure to obtain a coupled fluorescence signal, which is then transmitted to the fluorescence photoelectric conversion and signal processing module.

[0052] The optical excitation and fluorescence acquisition module receives 532nm excitation light, which is shaped by a quartz collimating lens and transmitted to the NV chip via an optical fiber coupling structure, exciting the NV center to generate red fluorescence. The fluorescence returns through the same optical fiber, and a bandpass filter removes residual excitation light, enabling detection based solely on the fluorescence signal.

[0053] This module achieves efficient transmission of excitation light and highly sensitive collection of fluorescence. The Y-shaped fiber structure improves the collection efficiency by more than 3 times. The OD6 filter deeply suppresses excitation light crosstalk, improving the signal-to-noise ratio by about 20dB. The all-fiber structure has strong vibration resistance and is suitable for integration with the detection probe.

[0054] The multi-physics isolation module includes: a fluororubber damping layer, a ceramic thermal insulation support component, and a non-magnetic elastic metal frame; In the multi-physics isolation module, a non-magnetic elastic metal frame serves as the outer support structure, with a fluororubber damping layer attached to its inner side; ceramic thermal insulation support components are embedded inside the fluororubber damping layer; the entire multi-physics isolation module is clamped and fixed between the non-magnetic bracket and the magnetic shielding and magnetic flux orientation module.

[0055] Through the above structural connection, this module can achieve the following technical effects: (1) The fluororubber damping layer absorbs mechanical vibrations of 20Hz–5kHz, and the vibration transmissibility is ≤0.1; (2) The ceramic thermal insulation support blocks heat conduction, with a thermal resistance ≥1K / W and chip temperature drift ≤±0.1℃; (3) Both the titanium alloy frame and the ceramic are non-magnetic, which blocks the coupling path of stray magnetic fields.

[0056] This module ensures stable output of the device under high vibration and temperature fluctuation environments, adapting to the operating conditions of high-speed trains.

[0057] In this embodiment, the fluororubber damping layer is model FKM-70, the ceramic thermal insulation support is made of alumina ceramic, model Al2O3-995, and the non-magnetic elastic metal frame is model titanium alloy TC4. Multiphysics isolation modules are used to attenuate external mechanical vibrations, isolate temperature gradients, and block non-target coupling of magnetic fields along the structural path; The multi-physics isolation module is clamped and fixed between the non-magnetic bracket and the magnetic shield and magnetic flux orientation module.

[0058] The magnetic shielding and flux orientation module includes: a high permeability alloy shielding layer, an asymmetric flux orientation backplate, and a non-magnetic support structure; A non-magnetic support structure serves as a mounting base and is fixed to the inner wall of the detection probe. A high permeability alloy shielding layer is assembled inside the non-magnetic support structure. An asymmetric magnetic flux orientation backplate is installed at the bottom of the high permeability alloy shielding layer and on the side closest to the bearing being tested. Together with the high permeability alloy shielding layer, they form a semi-enclosed cavity. The high permeability alloy shielding layer only forms a circular magnetic flux opening at the end closest to the bearing being tested. A flux shaping and current limiting component is located between the flux opening and the asymmetric flux orientation backplate. This component is installed in the central region of the asymmetric flux orientation backplate and is coaxially arranged with the flux opening. The flux opening and the flux shaping and current limiting component together form a flux opening assembly.

[0059] The flux shaping and current limiting component is a conical or stepped cylindrical magnetic permeable structure, preferably made of a high-permeability soft magnetic material (such as permalloy or 1J85 alloy), used to further concentrate and shape the magnetic lines of force entering the flux opening.

[0060] The structural dimensions of the flux shaping and current limiting component are: Diameter of the upper end (near the asymmetric flux orientation backplate): Φ1.5~Φ2.0 mm; Lower end diameter: Φ2.5~Φ3.0 mm; Height: 1.5–2.0 mm; A 0.2–0.5 mm flux gap is maintained between the flux shaping and current limiting component and the flux opening. This gap forms a flux sampling window, causing the magnetic field lines from the bearing direction to form a local flux contraction effect before entering the NV quantum magnetic sensing chip assembly area, thereby increasing the flux density and suppressing the transverse stray magnetic field. The non-magnetic support structure is made of 7075 aluminum alloy and has a conductive oxidation treatment on the surface, which combines structural strength and non-magnetic properties. The asymmetric flux-oriented backplate has a circumferentially non-uniform thickness, being thinnest (0.5 mm) near the probe's central axis and thickest (2.0 mm) further away. This causes the flux to preferentially converge axially towards the NV chip region, suppressing lateral stray magnetic field coupling. This structure creates a radial magnetoresistance gradient distribution. Thicker outer side → higher magnetic permeability → magnetic flux preferentially closes at the periphery; Thin in the center → Relatively large magnetic resistance → Magnetic flux is forced to concentrate axially; Therefore, magnetic field lines from the bearing direction are guided to the central region of the magnetic flux opening and enter the sensitive area of ​​the NV quantum magnetic sensing chip component, achieving magnetic flux convergence, transverse magnetic field suppression, and magnetic field gradient enhancement, thereby increasing the effective magnetic flux density of the NV quantum magnetic sensing chip component region by approximately 3 to 5 times. The high permeability alloy shielding layer is obtained by CNC machining a high permeability alloy material (1J85 iron-nickel alloy) followed by annealing. The specific process includes the following steps; 1. CNC machining of 1J85 alloy billet; 2. Vacuum annealing: Heat to 1100℃±20℃ and hold for 4 hours; 3. Slowly cool to below 200℃ at a rate of ≤50℃ / hour before removing from the furnace; 4. After annealing, cold working or impact is prohibited to prevent deterioration of magnetic properties.

[0061] A magnetic flux opening is provided at one end of the high permeability alloy shielding layer near the bearing under test, which forms a spatially selective entrance to the magnetic field.

[0062] The structural parameters of the magnetic flux opening are: Opening shape: circular; Opening diameter: Φ5 ± 0.1 mm; Opening depth: 2–3 mm; The magnetic flux opening is coaxially arranged with the sensitive area (approximately Φ3 mm) of the NV quantum magnetic sensing chip assembly, and its functions include: 1. Allow target magnetic flux in the bearing direction to enter the detection area; 2. Restrict the entry path of magnetic fields from non-target directions; 3. Together with the asymmetric flux orientation backplate and flux shaping and current limiting components, it forms a flux focusing structure; 4. Improve the detection sensitivity of NV quantum magnetic sensing chip for axial magnetic fields.

[0063] The magnetic shielding and flux orientation module is used to shield stray magnetic fields in non-target directions and guide the magnetic field signal in the direction of the bearing under test into the NV quantum magnetic sensing chip component area.

[0064] In the magnetic shielding and flux orientation module, the high permeability alloy shielding layer provides a low magnetic reluctance bypass for stray magnetic fields, suppressing the ambient magnetic field by ≥40dB; the asymmetric backplane (PC-5AS) uses the thickness difference to guide the magnetic flux in the bearing direction into the NV chip area along the axis, increasing the magnetic flux density in the target direction by 3 to 5 times; the non-magnetic support structure (aluminum alloy 7075) avoids generating additional magnetic coupling paths, ensuring that the shielding and orientation functions are independent and effective; through the above synergy, the magnetic shielding and flux orientation module achieves selective enhancement of the magnetic field in the bearing direction and efficient suppression of the ambient stray magnetic field, with a signal-to-noise ratio significantly better than the traditional Hall / magnetoresistive scheme.

[0065] The NV quantum magnetic sensing chip assembly includes: an NV central functional layer and an aluminum nitride (or aluminum nitride) ceramic substrate; The NV central functional layer is passed through. The NV central functional layer is passed through. For a type IIa single crystal diamond substrate (Element Six electronic grade single crystal diamond, 3mm×3mm×0.5mm, (100) crystal plane), nitrogen vacancy structure is formed by ion implantation and then annealed. Nitrogen ion implantation (energy 10~30keV, dose 10) 8 ~10 9 (ions / cm²) → Ultra-high vacuum annealing (800℃~1000℃, 2~4 hours) → Surface optical polishing and cleaning; those skilled in the art can prepare the NV central functional layer according to the above steps.

[0066] The NV quantum magnetic sensing chip assembly receives microwave signals, excitation light, and magnetic field signals from the bearing under test, generating a mixed fluorescence signal. Specifically, under the combined action of excitation light, microwave signals, and magnetic field signals from the bearing under test, the electron spin of the NV central functional layer undergoes resonant transition, and Zeeman splitting occurs simultaneously, generating a mixed fluorescence signal. The NV central functional layer adopts a vacuum eutectic bonding process, which connects the lower surface of the NV central functional layer to the metallization layer (titanium / platinum / gold multilayer film) on the upper surface of the aluminum nitride ceramic substrate by welding and fixing them at 320℃±10℃ with gold-tin solder (Au80Sn20). The thickness of the solder layer is ≤5μm, which ensures high bonding strength, low thermal resistance and good long-term stability. It is then connected to the inner wall of the detection probe by a non-magnetic structural component.

[0067] The non-magnetic structural component refers to a circular pressure ring made of titanium alloy TC4. The inner diameter of the ring is slightly smaller than that of the NV chip (NV central functional layer). The ring is threaded to the inner wall of the probe through a threaded hole on its edge. The lower edge of the pressure ring presses the edge of the NV chip evenly against the base surface, achieving a mechanical fixation that is glue-free, detachable, and free from magnetic interference.

[0068] The NV center functional layer is based on the principle of photodetector magnetic resonance of the NV color center: 532nm excitation light causes the electrons of the NV center to transition from the ground state to the excited state, and emit 637~800nm ​​red fluorescence when de-excited; when a microwave field of 2.87GHz±Δf is applied, the electron spin undergoes a resonant transition, and the fluorescence intensity changes; the external magnetic field causes Zeeman splitting, and the resonant frequency shift is linearly related to the magnetic field strength.

[0069] High-sensitivity magnetic field detection can be achieved by measuring resonant frequency shifts or fluorescence intensity changes. This chip component outputs a fluorescence signal correlated with local magnetic field changes under 532nm excitation, which is then converted into an electrical signal by subsequent modules, enabling nanotesla-level magnetic field measurement.

[0070] The probe end protection and mounting module includes: a ceramic end cap (or non-magnetic metal), a sealing ring, and a flange structure (or threads). The probe end protection and installation module provides mechanical protection, dustproofing, moisture protection, and installation positioning functions. Those skilled in the art can adjust the internal connection method of the probe end protection and installation module according to actual conditions. This embodiment provides one connection method: within the probe end protection and installation module, a flange structure is fixedly connected to the lower outer peripheral wall of the detection probe; a ceramic end cap is installed on the lower end face of the flange structure, covering the end opening of the detection probe; a sealing ring is embedded in the annular groove between the ceramic end cap and the flange structure, forming a seal through circumferential compression; the probe end protection and installation module is mechanically connected to the bearing seat or monitoring system bracket through the mounting holes on the flange structure to achieve probe fixation.

[0071] In this embodiment, the ceramic end cap is a zirconia ceramic end cap, model ZrO2-YSZ, the sealing ring is a fluororubber O-ring, model FKM-75, and the flange structure is an aluminum alloy 7075 flange with a conductive oxidation treatment on the surface.

[0072] The probe end protection and installation module provides mechanical protection, dust protection, moisture protection, and installation positioning functions; The probe end protection and installation module is fixed at the end of the detection probe that is close to the bearing being tested.

[0073] This module implements three functions: (1) The ceramic end cap serves as a protective layer at the front end of the probe, resisting the erosion of lubricating oil, dust, and microparticles near the bearing, and protecting the internal NV chip and optical components; (2) The sealing ring achieves IP67 dustproof and waterproof sealing, adapting to the humid and oily environment at the bottom of high-speed trains; (3) The flange structure provides a standardized mechanical interface, enabling quick disassembly and precise positioning of the probe and bearing housing or monitoring system, and ensuring that it does not loosen during long-term operation.

Claims

1. A single-probe, fully encapsulated NV quantum magnetic field detection device, characterized in that, The device is integrated inside a single detection probe, with the end of the device closer to the bearing being tested as the lower end and the end farther from the bearing being tested as the upper end. The device is arranged sequentially from top to bottom along the central axis of the detection probe: a signal output and system interface module, a fluorescence photoelectric conversion and signal processing module, a multi-physics field isolation module, an NV quantum magnetic sensing chip assembly, and a probe end protection and installation module. The multi-physics isolation module includes: a fluororubber damping layer, a ceramic thermal insulation support component, and a non-magnetic elastic metal frame; In the multi-physics isolation module, a non-magnetic elastic metal frame serves as the outer support structure, fixed to the inner wall of the detection probe, with a fluororubber damping layer attached to its inner side; a ceramic thermal insulation support is embedded within the fluororubber damping layer. Multiphysics isolation modules are used to attenuate external mechanical vibrations, isolate temperature gradients, and block non-target coupling of magnetic fields along the structural path; The multi-physics isolation module is clamped and fixed between the non-magnetic bracket and the magnetic shield and magnetic flux orientation module; Between the fluorescence photoelectric conversion and signal processing module and the multi-physics field isolation module, the microwave control module and the optical excitation and fluorescence acquisition module are positioned side by side via a non-magnetic bracket. The device also includes a magnetic shielding and magnetic flux orientation module, which surrounds the NV quantum magnetic sensing chip assembly and forms a circular magnetic flux opening only at one end near the bearing being tested. The magnetic shielding and flux orientation module includes: a high permeability alloy shielding layer, an asymmetric flux orientation backplate, and a non-magnetic support structure; A non-magnetic support structure serves as the mounting base and is fixed to the inner wall of the detection probe. A high permeability alloy shielding layer is assembled inside the non-magnetic support structure. An asymmetric magnetic flux orientation backplate is installed at the bottom of the high permeability alloy shielding layer and on the side closest to the bearing under test. Together with the high permeability alloy shielding layer, they form a semi-enclosed cavity. The high permeability alloy shielding layer only forms a circular magnetic flux opening at the end closest to the bearing under test. The thickness of the asymmetric flux orientation backplate is non-uniformly distributed circumferentially, being thinnest on the side closest to the central axis of the probe and thickest on the side furthest from the central axis of the probe. The magnetic shielding and flux orientation module is used to shield stray magnetic fields in non-target directions and guide the magnetic field signal in the direction of the bearing under test into the NV quantum magnetic sensing chip component area. The device also includes an external detection system and a power supply.

2. The single-probe fully encapsulated NV quantum magnetic field detection device according to claim 1, characterized in that, The operation of the device includes the following steps: S1. The external detection system generates a control signal, which is output to the fluorescence photoelectric conversion and signal processing module through the signal output and system interface module. S2, the fluorescence photoelectric conversion and signal processing module transmits the control signal to both the microwave control module and the optical excitation and fluorescence acquisition module. S3. The microwave control module generates a microwave signal according to the control signal and outputs it to the NV quantum magnetic sensing chip assembly. The optical excitation and fluorescence acquisition module generates excitation light according to the control signal and outputs it to the NV quantum magnetic sensing chip assembly. The S4 and NV quantum magnetic sensing chip components receive microwave signals, excitation light, and magnetic field signals from the bearing under test, generating a mixed fluorescence signal. S5. The mixed fluorescence signal is converted into a coupled fluorescence signal by the optical excitation and fluorescence acquisition module; S6. The coupled fluorescence signal is processed by the fluorescence photoelectric conversion and signal processing module to obtain the detection signal; S7. The detection signal is then output to the external detection system via the signal output and system interface module.

3. The single-probe fully encapsulated NV quantum magnetic field detection device according to claim 2, characterized in that, The signal output and system interface module includes a sealed electrical connector and a shielded wire. One end of the sealed electrical connector is connected to the power supply through the shielded wire, and the other end is connected to an external detection system through the shielded wire to receive control signals and output detection signals.

4. The single-probe fully encapsulated NV quantum magnetic field detection device according to claim 3, characterized in that, The fluorescence photoelectric conversion and signal processing module includes: a photodiode, a transimpedance amplifier, and a high-frequency, low-noise PCB. The coupled fluorescent signal is processed by the fluorescence photoelectric conversion and signal processing module to obtain the detection signal. Specifically, the photodiode receives the coupled fluorescent signal and converts it into an electrical signal. The electrical signal is then converted into a voltage signal by a transimpedance amplifier. The voltage signal is then processed by a low-pass filter and phase-locked synchronous demodulation circuit in a high-frequency low-noise PCB to obtain the detection signal.

5. A single-probe fully encapsulated NV quantum magnetic field detection device according to claim 4, characterized in that, The microwave control module includes: a microwave signal source, a voltage-controlled oscillator, a power regulation circuit, a loop microwave antenna, and an impedance matching unit; The microwave control module generates a microwave signal according to the control signal and outputs it to the NV quantum magnetic sensing chip assembly. Specifically, the microwave signal source receives the control signal and outputs a radio frequency reference signal. The voltage-controlled oscillator outputs a carrier signal according to the radio frequency reference signal. The power adjustment circuit outputs a radio frequency signal according to the carrier signal. The impedance matching unit outputs a matched radio frequency signal according to the radio frequency signal. The loop microwave antenna radiates the microwave signal to the NV quantum magnetic sensing chip assembly according to the matched radio frequency signal to drive the NV quantum magnetic sensing chip assembly to resonantly transition.

6. The single-probe fully encapsulated NV quantum magnetic field detection device according to claim 5, characterized in that, The optical excitation and fluorescence acquisition module includes: a semiconductor laser, a quartz collimating lens, an optical fiber coupling structure, and a bandpass filter; the bandpass filter is disposed in the optical path between the optical fiber coupling structure and the fluorescence photoelectric conversion and signal processing module. The optical excitation and fluorescence acquisition module generates excitation light according to the control signal and outputs it to the NV quantum magnetic sensing chip assembly. Specifically, the semiconductor laser receives the control signal and outputs initial excitation light. The quartz collimating lens outputs a collimated beam according to the initial excitation light. The fiber optic coupling structure outputs excitation light transmitted through the fiber optic cable according to the collimated beam. The excitation light transmitted through the fiber optic cable is then filtered by a bandpass filter to remove stray light and background scattered light before being output to the NV quantum magnetic sensing chip assembly. The mixed fluorescence signal is converted into a coupled fluorescence signal by the optical excitation and fluorescence acquisition module. Specifically, the mixed fluorescence signal is filtered by a bandpass filter to remove residual excitation light and background scattered light to obtain a filtered fluorescence signal. The filtered fluorescence signal is then coupled by an optical fiber coupling structure to obtain a coupled fluorescence signal, which is then transmitted to the fluorescence photoelectric conversion and signal processing module.

7. A single-probe fully encapsulated NV quantum magnetic field detection device according to claim 6, characterized in that, The NV quantum magnetic sensing chip assembly includes: the NV central functional layer and an aluminum nitride ceramic substrate; The NV central functional layer is obtained by ion implantation to form a nitrogen vacancy structure on a type IIa single crystal diamond substrate, followed by annealing. The NV quantum magnetic sensing chip assembly receives microwave signals, excitation light, and magnetic field signals from the bearing under test, generating a mixed fluorescence signal. Specifically, under the combined action of excitation light, microwave signals, and magnetic field signals from the bearing under test, the electron spin of the NV central functional layer undergoes resonant transition, and Zeeman splitting occurs simultaneously, generating a mixed fluorescence signal. The NV central functional layer is fixed on an aluminum nitride ceramic base and is threaded to the inner wall of the detection probe via a non-magnetic structural component.

8. A single-probe fully encapsulated NV quantum magnetic field detection device according to claim 7, characterized in that, The probe end protection and installation module includes: a ceramic end cap, a sealing ring, and a flange structure; The probe end protection and installation module provides mechanical protection, dust protection, moisture protection, and installation positioning functions; The probe end protection and installation module is fixed at the end of the detection probe that is close to the bearing being tested.

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