Quantum current sensing system and method based on hyperpolarization nuclear spinning magnetic field measurement

Abstract

The invention discloses a quantum current sensing system and method based on hyperpolarization nuclear spin magnetic field measurement, the system comprises a nuclear spin quantum magnetic field sensor and a nuclear spin control and precession signal board card, the nuclear spin quantum magnetic field sensor comprises an atom magnetometer probe and a light source system, an alkali metal gas chamber is arranged in the atom magnetometer probe, a signal pickup coil is arranged on the periphery of the alkali metal gas chamber, and 3He atoms and alkali metal atoms are filled in the alkali metal gas chamber; the light source system is used for heating the alkali metal gas chamber and hyperpolarized 3He nuclear spinning; the nuclear spin control and precession signal board card is used for generating a variable-length radio frequency pulse signal and loading the variable-length radio frequency pulse signal into the signal pickup coil so as to carry out space angle deviation on nuclear spin; a signal pickup coil picks up a magnetic field signal of precession frequency generated by nuclear spin magnetic moment to calculate a to-be-measured strong magnetic field; the system can be used for accurately measuring the strong current of the high-voltage transmission line.

Description

Technical Field

[0001] The invention relates to the technical field of strong current sensing measurement, and in particular to a quantum current sensing system and method based on hyperpolarized nuclear spin magnetic field measurement. Background Art

[0002] The transmission current in UHV transmission lines is generally in the order of 10KA. Large currents generally generate strong magnetic fields around the transmission lines. By measuring the strong magnetic fields, the magnitude of the current in the transmission lines can be inferred. Traditional methods of measuring current using optical fiber mutual inductors are easily affected by environmental interference, have reliability issues, and have limited measurement accuracy. It is urgent to invent new methods for non-contact measurement of high currents.

[0003] With the development of quantum science and technology, the precession effect of hyperpolarized nuclear spins in external magnetic fields can be used to measure strong magnetic fields. By making full use of the quantum effect of spins, the information of magnetic field intensity can be converted into the frequency information of nuclear spin precession. The detection is not affected by external temperature, light power fluctuations and light polarization state, and has the characteristics of high precision and high stability. In particular, the use of nuclear spins instead of electron spins can limit the precession frequency of the magnetic field of about 10mT generated by the power grid to the MHz level, leaving the microwave frequency band, and has the advantage of low power consumption. Therefore, the research on hyperpolarized nuclear spin quantum current sensing system is of great significance for realizing the detection of strong currents in ultra-high voltage transmission lines.

[0004] The measurement process of hyperpolarized nuclear spin quantum current sensing is as follows: (1) First, the nuclear spin is hyperpolarized by optical methods. The high nuclear spin polarization rate directly determines the size of the measurement signal, thereby improving the measurement sensitivity and accuracy of the sensor. However, in traditional nuclear spin hyperpolarization, a single alkali metal atom is used. 3 For nuclear spins that are difficult to polarize, such as He, the polarization rate is low; (2) A transverse radio frequency magnetic field is then applied to deflect the polarization direction of the nuclear spin and collect the nuclear spin free induced decay signal to obtain the magnitude of the magnetic field to be measured. However, although traditional nuclear magnetic resonance technology, such as the nuclear precession magnetic field detection method disclosed in the patent application document with publication number CN116359806A, has achieved the detection of precession signals, the nuclear spin direction cannot be controlled 360 degrees due to the limitations of radio frequency pulse width and pulse time; (3) Finally, the alternating electromagnetic field generated by the nuclear spin precession can be sensed by the pickup coil, thereby detecting the weak spin precession signal.

[0005] In addition, the core unit of the hyperpolarized nuclear spin quantum current sensor measurement is the measurement probe, which needs to have the characteristics of miniaturization and simple structure. However, most of the current optically pumped magnetometers are used for extremely weak magnetic field measurements and magnetic field measurements within the earth. For example, the patent application document with publication number CN116819407A proposes an atomic magnetometer system to achieve the use of131 Xe nuclear spin is used for weak magnetic field measurement. The atomic magnetometer uses a specific wavelength laser to polarize the atomic spin direction to achieve precise measurement of weak magnetic fields. It is sensitive to the weak magnetic field of the photodetector itself. Therefore, a magnetic field shielding barrel is needed to shield the influence of the Earth's magnetic field on the magnetometer. In addition, additional optical path elements are needed to change the optical path to arrange the photodetector away from the alkali metal atomic gas chamber. This makes the magnetometer system unable to have the characteristics of miniaturization and portability, limiting its application in natural environments. Summary of the invention

[0006] The technical problem to be solved by the present invention is how to achieve accurate measurement of high current in high-voltage transmission lines.

[0007] The present invention solves the above technical problems by the following technical means: The present invention proposes a quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement, the system comprising: a nuclear spin quantum magnetic field sensor and a nuclear spin manipulation and precession signal board, the nuclear spin quantum magnetic field sensor comprising an atomic magnetometer probe and a light source system, an alkali metal gas chamber is arranged in the atomic magnetometer probe, a signal pickup coil is arranged around the alkali metal gas chamber, and the alkali metal gas chamber is filled with 3 He atoms and alkali metal atoms; The light source system is used to heat and hyperpolarize the alkali metal gas chamber. 3 He nuclear spin; The nuclear spin manipulation and precession signal board is used to generate a variable-length radio frequency pulse signal to be loaded into the signal pickup coil to perform spatial angle shift on the nuclear spin; and to pick up the nuclear spin magnetic moment through the signal pickup coil to generate a magnetic field signal of precession frequency to calculate the strong magnetic field to be measured.

[0008] Further, the atomic magnetometer probe comprises a probe body, a pump laser optical path, a heating laser optical path and the alkali metal gas chamber, a cavity for accommodating the alkali metal gas chamber is provided in one end of the probe body, a pump light hole and a detection hole corresponding to the position are respectively provided on two side walls of the cavity, a right-angle prism is arranged corresponding to the pump light hole, a photodetector is arranged corresponding to the detection hole, and the signal pickup coil is provided on the upper surface and the lower surface of the cavity; A heating fiber hole and a pump fiber hole are provided at the other end of the probe body, a pump laser optical path and a heating laser optical path are integrated between the two ends of the probe body, one end of the pump laser optical fiber is inserted into the pump fiber hole, the other end of the pump laser optical fiber is connected to the pump laser, one end of the heating laser optical fiber is inserted into the heating fiber hole, and the other end of the heating laser optical fiber is connected to the heating laser; The pump light emitted by the pump laser passes through the pump laser optical path and the right-angle prism and then enters the alkali metal gas chamber for hyperpolarization. 3 He nuclear spin, the infrared laser emitted by the heating laser is incident on the alkali metal gas chamber through the heating laser optical path to heat the alkali metal gas chamber.

[0009] Furthermore, the signal pickup coil adopts a radio frequency magnetic field double-plane coil.

[0010] Further, the pump laser optical path includes a λ / 2 wave plate, a polarization beam splitter prism and a first fiber coupler in a coaxial state, the first fiber coupler is connected to a second fiber coupler via an optical fiber, an optical lens is arranged on the outgoing light path of the second fiber coupler, and a λ / 4 wave plate is arranged on the outgoing light path of the optical lens; The outgoing light of the λ / 4 wave plate is incident on the pump light hole and the detection hole through the right-angle prism and propagates to the photodetector.

[0011] Furthermore, the heating laser optical path includes a third fiber coupler and a fourth fiber coupler connected via optical fibers, the third fiber coupler is arranged on the output light path of the heating laser, and the output light of the fourth fiber coupler is incident on the alkali metal gas chamber.

[0012] Furthermore, the probe body is also provided with an optical lens hole bracket, a λ / 4 wave plate hole bracket and a prism base, the optical lens is arranged on the optical lens hole bracket, the λ / 4 wave plate is arranged on the λ / 4 wave plate hole bracket, and the right-angle prism is arranged on the prism base.

[0013] Furthermore, an air chamber fixing hole is arranged in the cavity, and the alkali metal air chamber is installed in the air chamber fixing hole.

[0014] Furthermore, the cavity is a thermal insulation chamber, and an air chamber cover is provided on the thermal insulation chamber.

[0015] Furthermore, a temperature sensor is arranged on the air chamber cover plate.

[0016] Furthermore, the atomic magnetometer probe is formed by 3D printing and the material is PEEK plastic.

[0017] Furthermore, the nuclear spin control and precession signal board includes a signal processing module, a radio frequency signal generation module, a time reference module, a switch module and a DAQ data acquisition system, wherein: The RF signal generating module is used to load the RF pulse signal to the signal pickup coil through the switch module, so that the signal pickup coil can be controlled. 3The He atomic nucleus spin deviates from the direction of the magnetic field to be measured by a certain angle, and the nuclear spin magnetic moment generates a magnetic field signal with a precession frequency; The signal processing module is used to connect to the signal pickup coil through the switch module after the RF pulse signal is loaded, and transmit the free induction attenuation signal of the magnetic field signal to the DAQ data acquisition system after processing; The DAQ data acquisition system is used to collect the processed free induction decay signal and store it in a host computer in a numerical form, and output a multi-channel TTL signal to control the timing and working duration of the switch module, the radio frequency signal generating module, and the time reference module; The time reference module is used to synchronize the signal references of the radio frequency signal generating module and the signal processing module.

[0018] Furthermore, the RF signal generating module includes: an RF generator and an RF amplifier, the RF generator is connected to the RF amplifier, and the TTL control end of the DAQ data acquisition system is connected to the RF amplifier; the time reference module is respectively connected to the DAQ data acquisition system, the signal processing module and the RF generator, and the RF amplifier, the signal pickup coil and the signal processing module are all connected to the switch module.

[0019] Furthermore, the time reference module includes a signal generator and a rubidium clock. The signal generator receives a clock synchronization signal output by a DAQ data acquisition system. The signal generator is connected to the rubidium clock, and the rubidium clock is connected to a radio frequency generator.

[0020] Furthermore, the signal processing module includes a bandpass filter, an amplifier, a mixer and a preamplifier connected in sequence, the preamplifier is connected to the signal acquisition port of the DAQ data acquisition system, and the bandpass filter is connected to the switch module; the mixer is connected to the signal generator in the time reference module, and the signal generator generates a trigger signal as a local oscillator signal input of the mixer.

[0021] Furthermore, the switch module includes a single-pole single-throw switch and a single-pole double-throw switch, the single-pole single-throw switch is connected to the single-pole double-throw switch, the single-pole double-throw switch is connected to the signal pickup coil, the single-pole single-throw switch is connected to the bandpass filter in the signal processing module, and the TTL control end of the DAQ data acquisition system is respectively connected to the single-pole single-throw switch and the single-pole double-throw switch.

[0022] Furthermore, the alkali metal gas chamber is filled with two alkali metal atoms and nuclear spin gas atoms. 3 He, and the densities of the two alkali metal atoms are different.

[0023] Furthermore, the two alkali metal atoms filled in the alkali metal gas chamber are Rb atoms and Cs atoms, respectively, and the density ratio of the Rb atoms to the Cs atoms is between 0.02 and 0.2.

[0024] Furthermore, the heating temperature of the alkali metal gas chamber is between 130 degrees Celsius and 180 degrees Celsius.

[0025] In addition, the present invention also proposes a quantum current measurement method based on hyperpolarized nuclear spin magnetic field measurement, using the quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement as described above to measure the current in the high-voltage current transmission line, the method comprising: Arrange a number of said nuclear spin quantum magnetic field sensors at equal intervals on the circumference of the high-voltage current transmission line, and the magnetic field generated by the current in the high-voltage current transmission line is perpendicular to the current transmission direction; The alkali metal gas chamber is heated and hyperpolarized by the light source system. 3 He nuclear spin; The nuclear spin manipulation and precession signal board generates a variable-length radio frequency pulse signal which is loaded into the signal pickup coil to perform spatial angle shift on the nuclear spin; and after the radio frequency pulse signal is loaded, the signal pickup coil picks up the magnetic moment of the nuclear spin to generate a magnetic field signal of the precession frequency, which is used to calculate the strong magnetic field to be measured.

[0026] Furthermore, the light source system is used to heat and hyperpolarize the alkali metal gas chamber. 3 He nuclear spins, including: The pump laser light path is used to emit a pump laser to irradiate the alkali metal gas chamber to cause spin exchange collision hyperpolarization between the two alkali metals. 3 He nuclear spin, the wavelength of the pump laser is the absorption wavelength of the alkali metal atom with higher density among the two alkali metal atoms; The heating laser emitted by the heating laser optical path is used to irradiate the alkali metal gas chamber, so that the heating temperature of the alkali metal gas chamber reaches the set working temperature.

[0027] Furthermore, the pump laser light path is used to emit a pump laser to irradiate the alkali metal gas chamber to cause spin exchange collision hyperpolarization between the two alkali metals. 3 He nuclear spins, including: The pump laser light path is used to emit a pump laser to irradiate the alkali metal gas chamber so that the spins of two alkali metal atoms in the gas chamber are exchanged and collided to polarize the low-density alkali metal atoms; Through the low density of alkali metal atoms and 3 He collision hyperpolarization 3 And nuclear spin.

[0028] Furthermore, the use of the nuclear spin manipulation and precession signal board to generate a variable-length radio frequency pulse signal and load it into the signal pickup coil to perform spatial angle shift on the nuclear spin includes: A magnetic field in the stationary coordinate system is applied to the signal pickup coil. Vertical RF pulsed magnetic field , so that 3 The He atom moves at an angular velocity in the stationary coordinate system. Rotation, where the magnetic field in the stationary coordinate system is the magnetic field to be measured, and the magnetic field to be measured is defined as along the z-axis direction of the stationary coordinate system: =B0 , B0 is the absolute value of the magnetic field to be measured, is the direction of the magnetic field to be measured. Generally, in current measurement, the direction of the magnetic field generated by the current is fixed. Assume that the direction of the magnetic field generated by the current is The coordinate axes of the stationary coordinate system are x, y, and z; Let the rotating coordinate system be relative to the stationary coordinate system at an angular velocity Rotation and RF magnetic field Direction along The effective field in the rotating coordinate system is obtained, where the rotating coordinate system The coordinate axis is , The z-axis coincides, The plane rotates around the z axis; According to the combination of the rotation angular velocity between the stationary coordinate system and the rotating coordinate system, the magnetic moment in the stationary coordinate system is determined. The precession frequency.

[0029] Furthermore, the duration of the radio frequency pulse signal The angle of nuclear spin deviation The relationship between them is:

[0030] In the formula, is the rotary magnetic ratio, Radio frequency pulse magnetic field The amplitude of .

[0031] The advantages of the present invention are: (1) In the present invention, a variable length radio frequency pulse signal is applied to the signal pickup coil by a nuclear spin control and precession signal board to control 3The spatial angle shift of He nuclear spin greatly increases the rotation angle range of the polarized nuclear spin, thereby improving the extraction efficiency of collecting free induction decay signals and the superposition efficiency of radio frequency signals, which helps to achieve accurate high current measurement.

[0032] (2) Traditional optically pumped magnetometer probes require additional optical path elements to change the optical path and place the photodetector away from the alkali metal atom gas chamber. Due to the presence of various optical components, the size of the probe cannot be reduced along the pump light direction, resulting in the application scenario being not suitable for magnetic field measurement in a small space. The present invention further optimizes various optical elements while ensuring the specific polarization state and spot size of the pump laser. By changing the optical path structure, such as adding a right-angle prism to change the propagation direction of the pump light, rearranging the polarization element, heating the laser fiber, etc., and reducing a right-angle prism optical component, the size of the probe in the pump light direction is further compressed, so that the size of the improved probe in the pump polarization direction is reduced by more than 2 times compared with the traditional probe.

[0033] (3) Targeting 3 He is difficult to polarize nuclear spins and has a low polarization rate. The present invention uses hybrid optical pumping to fill two alkali metal atoms in the alkali metal gas chamber. The hybrid optical pumping is achieved by combining the two alkali metal atoms. 3 The hyperpolarization of He nuclear spin and hybrid optical pumping can directly increase the overall density of alkali metal atoms inside the alkali metal gas chamber, so that the nuclear spin can be hyperpolarized by the high-density alkali metal electron spins, ultimately increasing the polarization rate of the nuclear spin and laying the foundation for a high signal-to-noise ratio nuclear spin precession signal.

[0034] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic diagram of the overall structure of an atomic magnetometer probe in one embodiment of the present invention; Figure 2 is a schematic structural diagram of an atomic magnetometer probe body in one embodiment of the present invention; Figure 3 is a schematic diagram of the optical path of an atomic magnetometer probe in one embodiment of the present invention; Figure 4 is a schematic diagram of signal acquisition of an atomic magnetometer probe in one embodiment of the present invention; Figure 5 Schematic diagram of the atomic species filled into the alkali metal gas chamber in one embodiment of the present invention; Figure 6 It is a schematic diagram of the structure of a nuclear spin control and precession signal board card in one embodiment of the present invention; Figure 7 This is a timing diagram of nuclear magnetic resonance pulse control realized by a nuclear spin control and precession signal board in one embodiment of the present invention; Figure 8 is a graph of free induction decay signals corresponding to a nuclear spin pointing angle of 45 degrees under different RF pulse signal durations in one embodiment of the present invention; Fig. 9 is a graph of free induction decay signals corresponding to a nuclear spin pointing angle of 90 degrees under different RF pulse signal durations in one embodiment of the present invention; Fig.10 is the free induction decay signal distribution corresponding to the nuclear spin pointing angle of 135 degrees under different radio frequency pulse signal durations in one embodiment of the present invention; Fig.11 It is a schematic flow chart of a quantum current measurement method based on hyperpolarized nuclear spin magnetic field measurement in one embodiment of the present invention; Fig.12 It is a schematic diagram of current measurement in a high-voltage current transmission line according to an embodiment of the present invention.

[0036] In the figure: 1-heating laser fiber, 2-pumping laser fiber, 3-photodetector, 4-signal pickup coil, 5-gas chamber cover, 6-probe body, 7-heating fiber hole, 8-pumping fiber hole, 9-optical lens hole bracket, 10-λ / 4 wave plate hole bracket, 11-prism base, 12-pumping light hole, 13-cover buckle, 14-gas chamber fixing hole, 15-detection hole, 16-host computer, 17-nuclear spin control and precession signal board, 18-cavity, 19-alkali metal gas chamber, 20-right angle prism, 21-first fiber coupler, 22-polarization beam splitter prism, 23-λ / 2 wave plate, 24-pumping laser, 25-heating laser, 26-third fiber coupler, 27-λ / 4 wave plate, 28-optical lens, 29-second fiber coupler, 30-fourth fiber coupler; 31-nuclear spin quantum magnetic field sensor. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1 like Figure 1 , Fig.12As shown, the first embodiment of the present invention proposes a quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement, the system includes a nuclear spin quantum magnetic field sensor 31 and a nuclear spin manipulation and precession signal board 17, the nuclear spin quantum magnetic field sensor includes an atomic magnetometer probe and a light source system, an alkali metal gas chamber 19 is provided in the atomic magnetometer probe, a signal pickup coil 4 is provided on the periphery of the alkali metal gas chamber 19, and the alkali metal gas chamber 19 is filled with 3 He atoms and alkali metal atoms; The light source system is used to heat and hyperpolarize the alkali metal gas chamber. 3 He nuclear spin; The nuclear spin manipulation and precession signal board 17 is used to generate a variable length radio frequency pulse signal to be loaded into the signal pickup coil 4 to perform spatial angle shift on the nuclear spin; and to pick up the nuclear spin magnetic moment through the signal pickup coil 4 to generate a magnetic field signal of precession frequency for calculating the strong magnetic field to be measured.

[0039] It should be noted that in this embodiment, a variable length radio frequency pulse signal is applied to the signal pickup coil by the nuclear spin control and precession signal board to control the 3 The spatial angle shift of He nuclear spin greatly increases the rotation angle range of the polarized nuclear spin, thereby improving the extraction efficiency of collecting free induction decay signals and the superposition efficiency of radio frequency signals, which helps to achieve accurate high current measurement.

[0040] As a further preferred technical solution, Figure 1 to Figure 2 As shown, the atomic magnetometer probe comprises a probe body 6, one end of which is provided with a cavity 18 for accommodating an alkali metal gas chamber 19, wherein the alkali metal gas chamber 19 is filled with 3 He atoms and alkali metal atoms, the two side walls of the cavity 18 are respectively provided with corresponding pump light holes 12 and detection holes 15, the right angle prism 20 is arranged corresponding to the pump light holes 12, the photodetector 3 is arranged corresponding to the detection holes 15, and the upper and lower surfaces of the cavity 18 are both provided with signal pickup coils 4; A heating fiber hole 7 and a pumping fiber hole 8 are provided at the other end of the probe body 6, one end of the pumping laser fiber 2 is inserted into the pumping fiber hole 8, and the other end of the pumping laser fiber 2 is connected to the pumping laser 24, one end of the heating laser fiber 1 is inserted into the heating fiber hole 7, and the other end of the heating laser fiber 1 is connected to the heating laser 25; the pumping light emitted by the pumping laser 24 is incident on the right-angle prism 20 through the first optical path structure, and the laser light emitted by the heating laser 25 is incident on the alkali metal gas chamber 19 through the second optical path structure.

[0041] It should be noted that in this embodiment, a signal pickup coil 4 is arranged on the upper and lower surfaces of the alkali metal gas chamber 19, and a pulse magnetic field is applied to the signal pickup coil 4 to excite the 3 The He nuclear spin deviates from the direction of the strong magnetic field to be measured, and the electric field signal is picked up and processed to read the information of the strong magnetic field to be measured. Since the current generated in the coil is detected, it is not sensitive to the weak current of the photodetector 3. Therefore, there is no need to put the probe into the magnetic shielding barrel, and there is no need to set up additional optical path elements to change the optical path to arrange the photodetector 3 away from the alkali metal atom gas chamber; therefore, this embodiment can further optimize various optical elements under the premise of ensuring the specific polarization state and spot size of the pump laser, and change the propagation direction of the pump light, rearrange the polarization element, heat the placement of the laser fiber 1, etc. by changing the optical path structure, such as designing and adding a right-angle prism 20 to change the direction of pump light propagation, rearrange the polarization element, and reduce the placement of a right-angle prism 20 optical components to further compress the size of the probe light in the pumping direction, so that the size of the improved probe in the pump polarization direction is reduced by more than 2 times compared with the traditional probe.

[0042] As a further preferred technical solution, Figure 3 to Figure 4 As shown, the first optical path structure includes a λ / 2 wave plate 23 in a coaxial state, a polarization beam splitter prism 22 and a first fiber coupler 21, the first fiber coupler 21 is connected to a second fiber coupler 29 via an optical fiber, an optical lens 28 is arranged on the outgoing light path of the second fiber coupler 29, and a λ / 4 wave plate 27 is arranged on the outgoing light path of the optical lens 28; The outgoing light of the λ / 4 wave plate 27 is incident on the right-angle prism 20 and propagates through the pump light hole 12 and the detection hole 15 to the photodetector 3 .

[0043] Specifically, the pump laser 24 emits a laser of corresponding wavelength, and adjusts the laser power and polarization state through the λ / 2 wave plate 23 and the polarization splitter prism 22 in turn. Then, the laser is loaded onto the probe through the first fiber coupler 21 and the second fiber coupler 29. The beam size and circular polarization state of the pump laser are adjusted through the optical lens 28 and the λ / 2 wave plate 23 on the probe. Then, the pump laser changes its propagation direction through the right-angle prism 20 and is incident on the alkali metal gas chamber 19 to polarize the 3He atoms. The transmitted pump light detects the laser power fluctuation through the photodetector 3.

[0044] As a further preferred technical solution, Figure 3 to Figure 4 As shown, the second optical path structure includes a third fiber coupler 26 and a fourth fiber coupler 30 connected via optical fibers. The third fiber coupler 26 is arranged on the outgoing light path of the heating laser 25 , and the outgoing light of the fourth fiber coupler 30 propagates to the alkali metal gas chamber 19 .

[0045] Specifically, the heating laser 25 injects the heating laser into the alkali metal gas chamber 19 through the third fiber coupler 26 and the fourth fiber coupler 30, so that the alkali metal gas chamber 19 reaches the required working temperature. Compared with the traditional heat convection conduction heating, the present embodiment adopts the laser heating gas chamber, which reduces the complexity of the system and only needs to add a deep hole corresponding to the size of the heating fiber on the probe.

[0046] As a further preferred technical solution, the probe body 6 is also provided with an optical lens 28 hole bracket 9, a λ / 4 wave plate 27 hole bracket 10 and a prism base 11, the optical lens 28 is arranged on the optical lens 28 hole bracket 9, the λ / 4 wave plate 27 is arranged on the λ / 4 wave plate 27 hole bracket 10, and the right-angle prism 20 is arranged on the prism base 11.

[0047] As a further preferred technical solution, an air chamber fixing hole 14 is arranged in the cavity 18 , and the alkali metal air chamber 19 is installed in the air chamber fixing hole 14 .

[0048] In this embodiment, two apertures are designed on the probe body 6 located below the right-angle prism 20 to fix the wave plate and the optical lens 28 to adjust and maintain the polarization state of the pump light, and the diameter of the pump light spot can be adjusted by replacing the optical lens 28 with different focal lengths.

[0049] Specifically, in this embodiment, one end of the heating laser fiber 1 is connected to the heating laser 25, and the other end is inserted into the heating fiber hole 7. Similarly, one end of the pump laser fiber 2 is connected to the pump laser 24, and the other end is inserted into the pump fiber hole 8. The designed aperture corresponds to the fiber diameter. The photodetector 3 is installed near the pump light hole 12, and the pump light is incident on the photodetector 3 through the light hole to realize real-time monitoring of the pump light power. Then, the optical lens 28 and the λ / 4 wave plate 27 are installed on the corresponding optical lens 28 hole bracket 9 and the λ / 4 wave plate 27 hole bracket 10. The polarization axis of the pump light can be adjusted by rotating the wave plate, so that the angle between the polarization axis of the pump light and the fast axis or slow axis of the glass slide is 45 degrees. The optical lens 28 with different focal lengths can be replaced to control the pump light spot diameter. The right-angle prism 20 can be fixed to the prism base 11 by gel to change the pump light propagation path. The alkali metal gas chamber 19 is installed on the gas chamber fixing hole 14, and its position is adjusted so that the pump light is incident on the central area of ​​the gas chamber, and then fixed by gel. Finally, the gas chamber cover 5 is snapped onto the cover buckle 13 to seal the gas chamber space and reduce the temperature loss in the gas chamber area.

[0050] In actual use, the atomic magnetometer probe is set in the strong magnetic environment to be measured for high-resolution measurement of strong magnetic fields. Signal pickup coils 4 are installed at the front and back of the gas chamber to control the nuclear spin so that the nuclear spin deviates from the direction of the magnetic field to be measured by a certain angle. The nuclear spin will precess in the external magnetic field, and the nuclear spin magnetic moment will generate a magnetic field signal of the precession frequency. Then the signal pickup coil 4 will take into account the function of the pickup coil to measure the nuclear spin precession signal. The data transceiver system board 17 connects the signal pickup coil 4 on the probe to the data processing system outside the strong magnetic field environment through a data line, and measures the precession frequency by demodulating the signal. The upper computer 16 is controlled to realize the measurement of the magnetic field size of the strong magnetic environment, and the magnetic field gradient measurement is realized by moving the probe.

[0051] In this embodiment, the electric field signal is picked up by the pickup coil and then processed to read the magnetic field information to be measured, and the laser power fluctuation of the pump laser 24 is monitored by the photodetector 3, thereby reducing the error introduced by the optical signal fluctuation. Therefore, the magnetism of the photodetector 3 itself does not affect the measurement accuracy, and the limitation of the shielding barrel required for the probe can be removed. There is no need for additional optical path elements to change the optical path to move the photodetector 3 away from the air chamber, which can greatly reduce the size of the probe. In addition, by integrating the heating laser, the pump laser, and the signal pickup coil 4, the polarized atoms are pumped to achieve hyperpolarization of the nuclear spin. Without affecting the magnetic field measurement accuracy of the magnetometer, the probe size is further reduced, so that the application scenarios of the probe are further expanded.

[0052] As a further preferred technical solution, the cavity 18 is a thermal insulation chamber, and an air chamber cover plate 5 is provided on the thermal insulation chamber.

[0053] It should be noted that after the air chamber is installed, the cover plate above the air chamber seals the cavity 18 where the air chamber is located through the buckle designed on the probe, thereby improving the thermal insulation of the air chamber cavity 18. Subsequently, a temperature sensor can still be placed on the cover plate to realize real-time monitoring of the air chamber temperature.

[0054] As a further preferred technical solution, the probe is formed by 3D printing, and the material is PEEK plastic.

[0055] It should be noted that the overall structure of the probe is formed through 3D printing and the material is PEEK plastic, which greatly improves the temperature resistance and structural strength of the probe.

[0056] Example 2 against 3 He is difficult to polarize nuclear spins and has a low polarization rate. Based on the disclosure of the above embodiment 1, this embodiment uses mixed light pumping to fill the alkali metal gas chamber with two alkali metal atoms and nuclear spin gas atoms. 3 He, and the densities of the two alkali metal atoms are different, e.g. Figure 5 shown.

[0057] Specifically, if it is a single alkali metal, as the temperature of the alkali metal gas chamber 19 increases, the saturated vapor pressure of the alkali metal atoms inside the gas chamber will increase, and the pump laser incident on the gas chamber will be strongly absorbed, resulting in the alkali metal atoms being mostly absorbed before they leave the gas chamber, resulting in the inability to effectively pump the alkali metal. The hybrid optically pumped hyperpolarized nuclear spin system proposed in this embodiment uses two alkali metal atoms to work simultaneously to hyperpolarize the nuclear spins, and controls the optical properties of the entire alkali metal gas chamber 19 by controlling the density ratio of the two alkali metal atoms. If two alkali metal atoms are filled into the gas chamber, the density of one alkali metal atom can be controlled to be low, while the density of the other alkali metal atom can be controlled to be very high, which is equivalent to the alkali metal in the entire gas chamber being an optically rarefied gas, and light can easily pass through the alkali metal gas chamber 19. In this process, since the density of the second alkali metal atom is quite high, the polarization process is completed through spin exchange collisions between the two alkali metals. Since the spin exchange collision rate is very large, the transfer of angular momentum can be carried out effectively in this process, thereby increasing the polarization rate of the nuclear spin, so that 3 When the He nuclear spin precesses, a larger spatial magnetic field is generated, which will induce a larger electromotive force signal in the signal pickup coil 4, thereby improving the signal-to-noise ratio of the measurement signal.

[0058] Furthermore, in this embodiment, the nuclear spin gas atoms are preferably 3 He atoms, because it is difficult to make a gas chamber with a pressure exceeding 3 atmospheres, 3 The gas pressure of He atoms is preferably around 3 atmospheres.

[0059] As a further preferred technical solution, the two alkali metal atoms filled in the alkali metal gas chamber 19 are Rb atoms and Cs atoms, or K atoms and Rb atoms, or K atoms and Cs atoms, or Rb atoms and K atoms, or Cs atoms and K atoms, and the density ratio of the Rb atoms to the Cs atoms is between 0.02 and 0.2. The density ratio in the atomic combination schemes such as K-Rb, K-Cs, Rb-K, and Cs-K is also preferably between 0.02 and 0.2.

[0060] It should be noted that if the density ratio of the two alkali metal atoms is too large, the polarization rate of the pump nuclear spin will be too low, thereby affecting the detection signal. If the density ratio is too small, the pump laser power requirement is high, which will cause excessive power consumption of the probe. This embodiment sets the density ratio of Rb atoms to Cs atoms between 0.02 and 0.2, which can well balance the polarization rate of nuclear spins and probe loss.

[0061] As a further preferred technical solution, the heating temperature of the alkali metal gas chamber 19 is between 130 degrees Celsius and 180 degrees Celsius.

[0062] It should be noted that since the two side walls of the alkali metal gas chamber 19 are made of glass, too low a temperature will affect the pumping effect and the probe sensitivity will be low, while too high a temperature will cause the alkali metal to corrode the glass and cause the alkali metal to be consumed. In this embodiment, the heating temperature of the alkali metal gas chamber 19 is controlled between 130 degrees Celsius and 180 degrees Celsius, which can ensure a relatively high sensitivity of the probe while avoiding the corrosion of the glass by the alkali metal.

[0063] Example 3 In view of the fact that the nuclear spin direction cannot be controlled 360 degrees due to the limitations of the radio frequency pulse width and pulse time in traditional nuclear magnetic resonance technology, this embodiment, based on the disclosure of the above embodiment 1, controls the nuclear spin by applying a variable length radio frequency pulse signal to the signal pickup coil through a specific design of the nuclear spin control and precession signal board. 3 The He nuclear spin undergoes spatial angle shift, which greatly increases the rotation angle range of the polarized nuclear spin, such as Figure 6 As shown, the nuclear spin control and precession signal board includes a signal processing module, a radio frequency signal generation module, a time reference module, a switch module and a DAQ data acquisition system, wherein: The RF signal generating module is used to load the RF pulse signal to the signal pickup coil through the switch module, so that the signal pickup coil can be controlled. 3 The He atomic nucleus spin deviates from the direction of the magnetic field to be measured by a certain angle, and the nuclear spin magnetic moment generates a magnetic field signal with a precession frequency; The signal processing module is used to connect to the signal pickup coil through the switch module after the RF pulse signal is loaded, and transmit the free induction attenuation signal of the magnetic field signal to the DAQ data acquisition system after processing; The DAQ data acquisition system is used to collect the processed free induction decay signal and store it in a host computer in a numerical form, and output a multi-channel TTL signal to control the timing and working duration of the switch module, the radio frequency signal generating module, and the time reference module; The time reference module is used to synchronize the signal references of the radio frequency signal generating module and the signal processing module.

[0064] As a further preferred technical solution, the RF signal generating module includes: an RF generator and an RF amplifier, the RF generator is connected to the RF amplifier, and the TTL control end of the DAQ data acquisition system is connected to the RF amplifier; the time reference module is respectively connected to the DAQ data acquisition system, the signal processing module and the RF generator, and the RF amplifier, the signal pickup coil and the signal processing module are all connected to the switch module.

[0065] As a further preferred technical solution, the time reference module includes a signal generator and a rubidium clock. The signal generator receives a clock synchronization signal output by a DAQ data acquisition system. The signal generator is connected to the rubidium clock, and the rubidium clock is connected to a radio frequency generator.

[0066] As a further preferred technical solution, the signal processing module includes a bandpass filter, an amplifier, a mixer and a preamplifier connected in sequence, the preamplifier is connected to the signal acquisition port of the DAQ data acquisition system, and the bandpass filter is connected to the switch module; the mixer is connected to the signal generator in the time reference module, and the signal generator generates a trigger signal as a local oscillator signal input of the mixer.

[0067] As a further preferred technical solution, the switch module includes a single-pole single-throw switch and a single-pole double-throw switch, the single-pole single-throw switch is connected to the single-pole double-throw switch, the single-pole double-throw switch is connected to the signal pickup coil, the single-pole single-throw switch is connected to the bandpass filter in the signal processing module, and the TTL control end of the DAQ data acquisition system is respectively connected to the single-pole single-throw switch and the single-pole double-throw switch.

[0068] In detail, the RF generator is used to generate a transverse (perpendicular to the z direction in the stationary coordinate system) RF signal to deflect the polarized nuclear spin direction. The RF generator is connected to the RF amplifier, which realizes public power amplification. The RF amplifier, the nuclear magnetic resonance coil and the signal processing module are all connected to the single-pole double-throw switch. The pulse signal amplified by the RF amplifier is output to the single-pole double-throw switch. The host computer is connected to the DAQ data acquisition system, and the pulse width, pulse time and switch control, the application of RF pulse signal to the nuclear magnetic resonance coil and the free induction decay signal acquisition control are realized through the host computer. The signal acquisition port of the DAQ data acquisition system is connected to the signal processing module, and the DAQ data acquisition system outputs TTL control signals to the signal processing module, the single-pole double-throw switch and the RF amplifier respectively, and the DAQ data acquisition system outputs clock synchronization signals to the time reference module.

[0069] The signal processing module includes a bandpass filter, an amplifier, a mixer and a preamplifier connected in sequence to complete the filtering, amplification, extraction and further amplification operations of the signal. By setting the preamplifier, the free induction decay signal is extracted and amplified from the collected signal to improve the signal-to-noise ratio. The single-pole single-throw switch is also connected to the single-pole double-throw switch and receives a TTL control signal output by the DAQ data acquisition system. The preamplifier is connected to the signal acquisition port of the DAQ data acquisition system to realize the digitization of the extracted free induction decay signal and transmit it to the host computer for storage and analysis. The signal generator is connected to the mixer, and the signal generator generates a trigger signal as the local oscillator signal input of the mixer, which further improves the time accuracy and reduces the introduction of additional system hardware.

[0070] The DAQ data acquisition system is used to collect the processed free induction decay signal and digitize it, store it on the host computer, and then output a multi-channel TTL signal to control the timing and working time of each module to avoid signal crosstalk between modules when working, and the system is synchronized to a rubidium clock time reference with ultra-high stability, so that the device still has high stability during long-term operation. This embodiment introduces an additional time reference signal in the data system through the clock reference module, so that the timing control and time control between the various modules of the system are based on the same reference, which greatly improves the stability and time accuracy of the system. The host computer controls each output end of the DAQ data acquisition system to output TTL signals to control each module, thereby improving the system integration and convenience.

[0071] The host computer is used for controlling the timing and sampling frequency of the entire device, as well as the working time control between various modules, the storage of collected signals, and data processing.

[0072] Specifically, the nuclear spin manipulation and precession signal board is used to generate a variable length radio frequency pulse signal to be loaded into the signal pickup coil, and the path of the magnetic field signal of the precession frequency generated by the nuclear spin magnetic moment is as follows: First, turn on the single-pole double-throw switch to connect the RF amplifier to the nuclear magnetic resonance coil. The RF generator sends an adjustable frequency RF wave to the RF amplifier for amplification. The output of the RF amplifier is turned on and off by the DAQ data acquisition system. The host computer controls the time of the RF amplifier output pulse signal to generate a pulse of variable length. The output of the RF amplifier is connected to the single-pole double-throw switch, and the single-pole double-throw switch outputs the pulse signal to the nuclear magnetic resonance coil to complete the loading of the pulse signal. After the pulse signal is recorded on the nuclear magnetic resonance coil, the nuclear magnetic resonance coil is perpendicular to the 3 A transverse pulse magnetic field is generated in the spin direction of the He atoms to stimulate 3 The He atom spin produces transverse precession.3 When the precession frequency of He nuclear spins is equal, 3 When He atoms absorb pulse energy, their spin direction will deflect toward the direction of the pulse magnetic field, and the deflection angle is controlled by the pulse time; the single-pole single-throw switch is in a closed state during the period when the RF generator transmits the pulse signal. When the pulse signal is loaded, the single-pole double-throw switch is closed, and the nuclear magnetic resonance coil probe is connected to the single-pole single-throw switch. At the same time, the single-pole single-throw switch is opened to connect the channel between the nuclear magnetic resonance coil and the signal processing module. 3 The He nuclear spin will relax back to the direction of the magnetic field to be measured (i.e. the direction of the geomagnetic field in reality). During this process, the nuclear magnetic resonance coil senses a change in magnetic flux, i.e. a free decay oscillation signal will be generated in the nuclear magnetic resonance coil. The free induction decay signal is extracted, amplified and denoised through a bandpass filter, an amplifier, a mixer and a preamplifier to obtain an FID signal related to the magnetic field strength information to be measured. At the same time, the processed FID signal is recorded and saved by the host computer so that the FID signal related to the magnetic field strength information to be measured can be used for data fitting to obtain the magnetic field strength information.

[0073] Furthermore, in order to improve the signal-to-noise ratio, the process of nuclear magnetic resonance pulse generation and free induction decay signal acquisition and recording is repeated multiple times, that is, the above process of nuclear magnetic resonance pulse generation and free induction decay signal acquisition and recording is repeated multiple times to remove additional environmental interference; for each cycle, the emitted pulse time and the time of the entire cycle are controlled by the host computer program, and an external synchronous clock is used as a reference. The read and write data rates can be determined by an external function generator, and all function signals used as triggers in the system are synchronized to the rubidium clock to ensure that all component times are based on the rubidium clock reference. The nuclear spin manipulation and precession signal board realizes the nuclear magnetic resonance pulse control timing diagram as shown in Figure 7 shown.

[0074] This embodiment adds an RF amplifier between the RF generator and the single-pole double-throw switch, so that the RF signal applied to the nuclear magnetic resonance coil is greatly enhanced, the rotation angle range of the polarized nuclear spin pointing is greatly improved, the extraction efficiency of collecting free induction decay signals is improved, the superposition efficiency of RF signals is improved, additional hardware equipment is reduced, and the convenience and compatibility of the system are improved. The RF amplifier is synchronized to the calibrated DAQ data acquisition system through the control port, and the time accuracy and stability are greatly improved, thereby achieving precise control within a range of 360 degrees. In addition, each functional component is modularized, and the sending and receiving signals are implemented in one system, realizing the integration of sending and receiving signals.

[0075] Example 4 like Figure 11 to Figure 12As shown, the fourth embodiment of the present invention proposes a quantum current measurement method based on hyperpolarized nuclear spin magnetic field measurement, using the quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement described in the above embodiment to measure the current in the high-voltage current transmission line, the method includes the following steps: S10, arranging a number of the nuclear spin quantum magnetic field sensors at equal intervals on the circumference of the high-voltage current transmission line, wherein the magnetic field generated by the current in the high-voltage current transmission line is perpendicular to the current transmission direction; S20, using the light source system to heat and hyperpolarize the alkali metal gas chamber 3 He nuclear spin; S30, using the nuclear spin manipulation and precession signal board to generate a variable-length radio frequency pulse signal and load it into the signal pickup coil to perform spatial angle shift on the nuclear spin; and after the radio frequency pulse signal is loaded, the signal pickup coil picks up the nuclear spin magnetic moment to generate a precession frequency magnetic field signal to calculate the strong magnetic field to be measured.

[0076] It should be noted that the high-voltage current transmission line transmits a large current in the power grid. On a circle R away from the transmission line, the magnetic field generated by the current is perpendicular to the current transmission direction, wherein the distance R is preferably about 30 cm. Nuclear spin quantum magnetic field sensors are arranged at equal intervals on this circle, and the nuclear spin quantum magnetic field sensors are used to measure the magnetic field generated by the current and to reverse the current in the transmission line. Among them, multiple nuclear spin quantum magnetic field sensors are used to eliminate current measurement errors, and the number of nuclear spin quantum magnetic field sensors is preferably 4. The nuclear spin control and precession signal board is placed on the ground, and the nuclear spin control and precession signal board and the nuclear spin quantum magnetic field sensor are transmitted by wires for signal transmission and optical transmission.

[0077] As a further preferred technical solution, the step S20: using the light source system to heat and hyperpolarize the alkali metal gas chamber 3 He nuclear spin, including the following steps: S21, using the pump laser optical path to emit a pump laser to irradiate the alkali metal gas chamber to achieve hyperpolarization through spin exchange collision between the two alkali metals 3 He nuclear spin, the wavelength of the pump laser is the absorption wavelength of the alkali metal atom with higher density among the two alkali metal atoms; S22, irradiating the alkali metal gas chamber with the heating laser emitted by the heating laser optical path, so that the heating temperature of the alkali metal gas chamber reaches a set working temperature.

[0078] As a further preferred technical solution, the step S21: using the pump laser optical path to emit a pump laser to irradiate the alkali metal gas chamber to hyperpolarize the spin exchange collision between the two alkali metals. 3He nuclear spins, including: The pump laser light path is used to emit a pump laser to irradiate the alkali metal gas chamber so that the spins of two alkali metal atoms in the gas chamber are exchanged and collided to polarize the low-density alkali metal atoms; Through the low density of alkali metal atoms and 3 He collision hyperpolarization 3 And nuclear spin.

[0079] As a further preferred technical solution, the step S22: using the heating laser emitted by the heating laser optical path to irradiate the alkali metal gas chamber so that the heating temperature of the alkali metal gas chamber reaches a set working temperature, specifically includes: The heating laser emitted by the heating laser optical path is used to irradiate the alkali metal gas chamber, and when the optical depth of the atomic absorption pump light in the alkali metal gas chamber is 1-3, it is determined that the heating temperature of the alkali metal gas chamber reaches the set working temperature.

[0080] It should be further explained that the hyperpolarized NMR technique is usually performed on alkali metal atomic gas chamber samples with a magnetization intensity of M = ρPµ, where is the magnetic moment of the nucleus. and magnetic moment The nuclei of are:

[0081] Where γ is the rotational magnetic ratio.

[0082] In magnetic field In the magnetic moment Experience a torque , which is equal to the rate of change of angular momentum, according to Newton's second law:

[0083] So we get the magnetic moment The equation of motion is:

[0084] The NMR form uses the technique of switching to a rotating coordinate system by defining a stationary coordinate system S and a new rotating coordinate system , the coordinate axes of the stationary coordinate system are x, y, and z, and the rotating coordinate system The coordinate axis is , The z-axis coincides, The angular velocity relative to S is , we get the magnetic moment in the rotating coordinate system The equation of motion is:

[0085] The equation of motion is the magnetic moment In the effective magnetic field = + The equation of motion in is the Larmor frequency.

[0086] The magnetic field in the stationary coordinate system, i.e. the magnetic field to be measured, is defined as along the z-axis: =B0 , then when When the effective field =0, B0 is the amplitude of the magnetic field generated by the current to be measured, is the direction of the magnetic field to be measured. This is called the Larmor frequency, where In the rotating coordinate system The equation of motion in the , indicating that the magnetic moment does not move in the rotating coordinate system. =B0 In the presence of In the stationary coordinate system, the Larmor frequency The power of NMR as an experimental technique lies in The Larmor frequency of a sample of nuclei with known γ can be measured to measure.

[0087] Therefore, in addition to the magnetic field in the stationary coordinate system, this embodiment applies a radio frequency magnetic field perpendicular to the magnetic field in the stationary coordinate system to the signal pickup coil to perform spatial angle shift on the nuclear spin. Specifically, in step S30: using the nuclear spin manipulation and precession signal board to generate a radio frequency pulse signal of variable length and loading it into the signal pickup coil to perform spatial angle shift on the nuclear spin, the following steps are included: S31, applying a magnetic field in the stationary coordinate system to the signal pickup coil Vertical RF pulsed magnetic field , so that 3 The He atom moves at an angular velocity in the stationary coordinate system. Rotation: , where the magnetic field in the stationary coordinate system is is the magnetic field to be measured, and the magnetic field to be measured is defined as along the z-axis direction of the stationary coordinate system: =B0 , B0 is the amplitude of the magnetic field generated by the current to be measured, is the direction of the magnetic field to be measured, In the magnetic field to be measured 3 The Larmor precession frequency of He, is the amplitude of the RF pulse magnetic field, t is the time, and the coordinate axes of the stationary coordinate system are x, y, and z; S32, let the rotating coordinate system be relative to the stationary coordinate system S at an angular velocity Rotation and RF magnetic field Direction along The effective magnetic field in the rotating coordinate system is unchanged. , where the rotation coordinate system The coordinate axis is , The z-axis coincides, The plane rotates around the z-axis, , , , They represent the unit vectors of the x-axis and y-axis in the stationary frame and the unit vectors of the z-axis and x-axis in the new rotating coordinate system. The term is rotated from B0 to the rotating coordinate system produce; S33, determining the magnetic moment in the stationary coordinate system according to the combination of the rotation angular velocity between the stationary coordinate system and the rotating coordinate system The precession frequency.

[0088] It should be noted that Defined as the Larmor frequency associated with B1 (where B1 is always positive), the effective magnetic field The size is:

[0089] In the formula, is the rotation frequency of the rotating coordinate system relative to the stationary coordinate system, is the Larmor frequency associated with B1, It represents the magnitude of the equivalent magnetic field felt by the nuclear spin in the rotating coordinate system.

[0090] By Represents the rotation coordinate system The associated Larmor field, magnetic moment in the stationary coordinate system The precession is the angular velocity between the stationary coordinate system and the rotating coordinate system A combination of is the equivalent motion frequency of the nuclear spin in the rotating coordinate system.

[0091] Effective Field and the magnetic field to be measured The angle between It can be calculated as follows:

[0092] When this angle is static, the magnetic moment in the stationary coordinate system is The angle between B0 and B0 changes with time, which is determined by the assumed magnetic moment and B0 in = 0, the same as the stationary coordinate system Aligned, then:

[0093] In the formula, In pulsed radio frequency field The angle at which the nuclear spin points under the action of the force is the angle between the nuclear spin and the z direction.

[0094] In practice, the magnitude of B1 is much smaller than that of B0. Very small, Very small (with In other words, the magnetic moment is aligned with B0 along the z-axis, and when the frequency of the magnetic field B1 is near , which is the Larmor frequency of B0, which causes resonance, which means that by opening the frequency close to The field B1 for a period of time t can controllably rotate the magnetic moment from the z axis to a certain angle , at this time the magnetic moment rotates around the z-axis. Therefore, the nuclear spin pointing angle can be achieved by precisely controlling the RF pulse working time through the host computer Precise control.

[0095] As a further preferred technical solution, the duration of the radio frequency pulse signal is The angle of nuclear spin deviation The relationship between them is:

[0096] In the formula, is the rotary magnetic ratio, Radio frequency pulse magnetic field The amplitude of That is, any nuclear spin deviation angle.

[0097] For example, the rotation angle is When the B1(t) field is called a π / 2 pulse, the required pulse signal duration is t 1 / 2 for:

[0098] After rotating the precession into the transverse plane using such a π / 2 pulse, the induced current can be picked up from this precession using a pickup coil. The signal from the coil is called the free induction decay (FID) signal, and thus provides a measure of the B0 magnetic field. This process is called pulsed NMR, as Figures 8 to 10The different nuclear spin pointing angles and the corresponding free induction decay signal distributions generated by different pulse times are shown, where: Figure 8 , Fig. 9 , Fig.10 They represent the free induction decay signal distributions corresponding to nuclear spin pointing angles of 45, 90 and 135 degrees, respectively. Figure 8-Figure 10 It can be seen that the present invention can achieve the adjustment of different nuclear spin pointing angles, greatly increasing the rotation angle range of the polarized nuclear spin pointing.

[0099] Through the above technical solution, this embodiment adds an RF amplifier between the RF generator and the single-pole double-throw switch, so that the RF signal applied to the nuclear magnetic resonance coil is greatly enhanced, the rotation angle range of the polarized nuclear spin pointing is greatly improved, the extraction efficiency of collecting free induction decay signals is improved, the superposition efficiency of RF signals is improved, additional hardware equipment is reduced, and the convenience and compatibility of the system are improved. The RF amplifier is synchronized to the calibrated DAQ data acquisition system through the control port, and the time accuracy and stability are greatly improved, thereby achieving precise control within a 360-degree range, and each functional component is modularized, and the receiving and transmitting signals are implemented in one system, realizing the integration of the receiving and transmitting signals.

[0100] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0101] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0102] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement, characterized in that: The system includes a nuclear spin quantum magnetic field sensor and a nuclear spin control and precession signal board. The nuclear spin quantum magnetic field sensor includes an atomic magnetometer probe and a light source system. An alkali metal gas chamber is arranged in the atomic magnetometer probe. A signal pickup coil is arranged around the alkali metal gas chamber. The alkali metal gas chamber is filled with 3 He atoms and alkali metal atoms; The light source system is used to heat and hyperpolarize the alkali metal gas chamber. 3 He nuclear spin; The nuclear spin manipulation and precession signal board is used to generate a variable-length radio frequency pulse signal to be loaded into the signal pickup coil to perform spatial angle shift on the nuclear spin; And the magnetic field signal of the precession frequency generated by the nuclear spin magnetic moment is picked up by the signal pickup coil to calculate the strong magnetic field to be measured.

2. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 1, characterized in that: The atomic magnetometer probe comprises a probe body, a pump laser optical path, a heating laser optical path and the alkali metal gas chamber. A cavity for accommodating the alkali metal gas chamber is provided in one end of the probe body. Pump light holes and detection holes corresponding to the positions are provided on the two side walls of the cavity respectively. A right-angle prism is arranged corresponding to the pump light holes, and a photodetector is arranged corresponding to the detection holes. The signal pickup coil is provided on the upper and lower surfaces of the cavity. A heating fiber hole and a pump fiber hole are provided at the other end of the probe body, a pump laser optical path and a heating laser optical path are integrated between the two ends of the probe body, one end of the pump laser optical fiber is inserted into the pump fiber hole, the other end of the pump laser optical fiber is connected to the pump laser, one end of the heating laser optical fiber is inserted into the heating fiber hole, and the other end of the heating laser optical fiber is connected to the heating laser; The pump light emitted by the pump laser passes through the pump laser optical path and the right-angle prism and then enters the alkali metal gas chamber for hyperpolarization. 3 He nuclear spin, the infrared laser emitted by the heating laser is incident on the alkali metal gas chamber through the heating laser optical path to heat the alkali metal gas chamber.

3. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 1, characterized in that: The signal pickup coil adopts a radio frequency magnetic field double-plane coil.

4. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 2, characterized in that: The pump laser optical path includes a λ / 2 wave plate, a polarization beam splitter prism and a first fiber coupler in a coaxial state, the first fiber coupler is connected to a second fiber coupler via an optical fiber, an optical lens is arranged on the outgoing light path of the second fiber coupler, and a λ / 4 wave plate is arranged on the outgoing light path of the optical lens; The outgoing light of the λ / 4 wave plate is incident on the pump light hole and the detection hole through the right-angle prism and propagates to the photodetector.

5. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 2, characterized in that: The heating laser optical path includes a third fiber coupler and a fourth fiber coupler connected via optical fibers. The third fiber coupler is arranged on the outgoing light path of the heating laser, and the outgoing light of the fourth fiber coupler is incident on the alkali metal gas chamber.

6. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 4, characterized in that: The probe body is also provided with an optical lens hole bracket, a λ / 4 wave plate hole bracket and a prism base, the optical lens is arranged on the optical lens hole bracket, the λ / 4 wave plate is arranged on the λ / 4 wave plate hole bracket, and the right-angle prism is arranged on the prism base.

7. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 2, characterized in that: An air chamber fixing hole is arranged in the cavity, and the alkali metal air chamber is installed in the air chamber fixing hole.

8. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 2, characterized in that: The cavity is a heat-insulating chamber, and an air chamber cover is arranged on the heat-insulating chamber.

9. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 8, characterized in that: A temperature sensor is arranged on the air chamber cover plate.

10. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to any one of claims 1 to 9, characterized in that: The atomic magnetometer probe is formed by 3D printing and is made of PEEK plastic.

11. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 1, characterized in that: The nuclear spin control and precession signal board includes a signal processing module, a radio frequency signal generation module, a time reference module, a switch module and a DAQ data acquisition system, wherein: The RF signal generating module is used to load the RF pulse signal to the signal pickup coil through the switch module, so that the signal pickup coil can be controlled. 3 The He atomic nucleus spin deviates from the direction of the magnetic field to be measured by a certain angle, and the nuclear spin magnetic moment generates a magnetic field signal with a precession frequency; The signal processing module is used to connect to the signal pickup coil through the switch module after the RF pulse signal is loaded, and transmit the free induction attenuation signal of the magnetic field signal to the DAQ data acquisition system after processing; The DAQ data acquisition system is used to collect the processed free induction decay signal and store it in a host computer in a numerical form, and output a multi-channel TTL signal to control the timing and working duration of the switch module, the radio frequency signal generating module, and the time reference module; The time reference module is used to synchronize the signal references of the radio frequency signal generating module and the signal processing module.

12. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 11, characterized in that: The RF signal generating module comprises: an RF generator and an RF amplifier, the RF generator is connected to the RF amplifier, and the TTL control end of the DAQ data acquisition system is connected to the RF amplifier; the time reference module is respectively connected to the DAQ data acquisition system, the signal processing module and the RF generator, and the RF amplifier, the signal pickup coil and the signal processing module are all connected to the switch module.

13. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 12, characterized in that: The time reference module comprises a signal generator and a rubidium clock. The signal generator receives a clock synchronization signal output by a DAQ data acquisition system. The signal generator is connected to the rubidium clock, and the rubidium clock is connected to a radio frequency generator.

14. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 11, characterized in that: The signal processing module includes a bandpass filter, an amplifier, a mixer and a preamplifier connected in sequence, the preamplifier is connected to the signal acquisition port of the DAQ data acquisition system, and the bandpass filter is connected to the switch module; the mixer is connected to the signal generator in the time reference module, and the signal generator generates a trigger signal as a local oscillator signal input of the mixer.

15. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 11, characterized in that: The switch module includes a single-pole single-throw switch and a single-pole double-throw switch, the single-pole single-throw switch is connected to the single-pole double-throw switch, the single-pole double-throw switch is connected to the signal pickup coil, the single-pole single-throw switch is connected to the bandpass filter in the signal processing module, and the TTL control end of the DAQ data acquisition system is respectively connected to the single-pole single-throw switch and the single-pole double-throw switch.

16. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 1, characterized in that: The alkali metal gas chamber is filled with two alkali metal atoms and nuclear spin gas atoms. 3 He, and the densities of the two alkali metal atoms are different.

17. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 16, characterized in that: The two alkali metal atoms filled in the alkali metal gas chamber are Rb atoms and Cs atoms, respectively, and the density ratio of the Rb atoms to the Cs atoms is between 0.02 and 0.

2.

18. The quantum current sensing system based on hyperpolarized nuclear spin magnetic field measurement according to claim 16, characterized in that: The heating temperature of the alkali metal gas chamber is between 130 degrees Celsius and 180 degrees Celsius.

19. A quantum current measurement method based on hyperpolarized nuclear spin magnetic field measurement, characterized in that: The quantum current sensing system based on the measurement of the hyperpolarized nuclear spin magnetic field as claimed in any one of claims 1 to 18 is used to measure the current in the high-voltage current transmission line, the method comprising: Arrange a number of said nuclear spin quantum magnetic field sensors at equal intervals on the circumference of the high-voltage current transmission line, and the magnetic field generated by the current in the high-voltage current transmission line is perpendicular to the current transmission direction; The alkali metal gas chamber is heated and hyperpolarized by the light source system. 3 He nuclear spin; The nuclear spin manipulation and precession signal board generates a variable-length radio frequency pulse signal which is loaded into the signal pickup coil to perform spatial angle shift on the nuclear spin; and after the radio frequency pulse signal is loaded, the signal pickup coil picks up the magnetic moment of the nuclear spin to generate a magnetic field signal of the precession frequency, which is used to calculate the strong magnetic field to be measured.

20. The quantum current measurement method based on hyperpolarized nuclear spin magnetic field measurement according to claim 19, characterized in that: The light source system is used to heat and hyperpolarize the alkali metal gas chamber. 3 He nuclear spins, including: The pump laser is emitted from the pump laser optical path to irradiate the alkali metal gas cell to cause spin exchange collision hyperpolarization between the two alkali metals. 3 He nuclear spin, the wavelength of the pump laser is the absorption wavelength of the alkali metal atom with higher density among the two alkali metal atoms; The heating laser emitted by the heating laser optical path is used to irradiate the alkali metal gas chamber so that the heating temperature of the alkali metal gas chamber reaches the set working temperature.

21. The quantum current measurement method based on hyperpolarized nuclear spin magnetic field measurement according to claim 20, characterized in that: The pump laser light path is used to emit a pump laser to irradiate the alkali metal gas chamber to cause spin exchange collision hyperpolarization between the two alkali metals. 3 He nuclear spins, including: The pump laser light path is used to emit a pump laser to irradiate the alkali metal gas chamber so that the spins of two alkali metal atoms in the gas chamber are exchanged and collided to polarize the low-density alkali metal atoms; Through the low density of alkali metal atoms and 3 He collision hyperpolarization 3 And nuclear spin.

22. The quantum current measurement method based on hyperpolarized nuclear spin magnetic field measurement according to claim 19, characterized in that: The method of using the nuclear spin manipulation and precession signal board to generate a variable length radio frequency pulse signal and loading it into the signal pickup coil to perform spatial angle shift on the nuclear spin includes: A magnetic field in the stationary coordinate system is applied to the signal pickup coil. Vertical RF pulsed magnetic field , so that 3 The He atom moves at an angular velocity in the stationary coordinate system Rotation, where the magnetic field in the stationary coordinate system is the magnetic field to be measured, and the magnetic field to be measured is defined as along the z-axis direction of the stationary coordinate system: =B0 , B0 is the amplitude of the magnetic field generated by the current to be measured, is the direction of the magnetic field to be measured, and the coordinate axes of the stationary coordinate system are x, y, and z; Let the rotating coordinate system be relative to the stationary coordinate system at an angular velocity Rotation and RF magnetic field Direction along The effective field in the rotating coordinate system is obtained, where the rotating coordinate system The coordinate axis is , The z-axis coincides, The plane rotates around the z axis; According to the combination of the rotation angular velocity between the stationary coordinate system and the rotating coordinate system, the magnetic moment in the stationary coordinate system is determined. The precession frequency.

23. The quantum current measurement method based on hyperpolarized nuclear spin magnetic field measurement according to claim 19, characterized in that: The duration of the radio frequency pulse signal The angle of nuclear spin deviation The relationship between them is: In the formula, is the rotary magnetic ratio, Radio frequency pulse magnetic field The amplitude of .

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