Magnetic moment comparator apparatus and method of measurement

Abstract

The application discloses a magnetic moment comparator device and a measuring method. The magnetic moment of a current-carrying standard coil is proportional to the magnetic field generated at a fixed distance on the axis, and according to the principle of equivalence between the magnetic dipole layer and the current-carrying coil in electromagnetism, the magnetic moment of the magnetic sample at the same position can be measured by the current-carrying standard coil when the spatial magnetic field can be accurately measured. The application designs a magnetic moment comparator in a magnetic shielding cylinder, uses an atomic magnetometer to measure the absolute magnetic field with high sensitivity, places a current-carrying standard coil at a distance r0 on one side of the atomic chamber along the background magnetic field direction, and the axis is parallel to the background magnetic field direction; the magnetic moment direction of the magnetic sample is parallel to the background magnetic field direction, when the magnetic sample is moved to the position of the atomic chamber at a distance r0 on the other side of the atomic chamber by a sample transmission rod, the current flowing into the standard coil is changed in real time under the condition that the background magnetic field remains unchanged, and then the magnetic moment of the magnetic sample is equal in size and opposite in direction to the magnetic moment of the current-carrying standard coil.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the field of precision measurement, and particularly relates to a magnetic moment comparator device and a measurement method. BACKGROUND

[0002] In electromagnetism, a magnetic dipole layer is equivalent to a current-carrying coil, so the magnetic field generated by a magnetic sample in space can be equivalent to the magnetic field generated by a current-carrying coil on its axis. When the magnetic moment of the magnetic sample and the current-carrying coil is equal in size and opposite in direction, the magnetic fields generated by the two at the midpoint of the distance between them theoretically cancel each other out. The present application utilizes this feature to place a high-sensitivity magnetic sensor at the midpoint of the distance between the magnetic sample and the current-carrying coil, forming a magnetic moment comparator, and realizing the measurement of the magnetic moment of the magnetic sample using the magnetic moment of the current-carrying standard coil. SUMMARY

[0003] Therefore, the present application provides a magnetic moment comparator device and a measurement method. The background magnetic field remains unchanged as the determination condition, and the current flowing into the standard coil is changed in real time. Then the magnetic moment of the magnetic sample and the magnetic moment of the current-carrying standard coil are equal in size and opposite in direction, so as to measure the magnetic moment of the magnetic sample by using the magnetic moment of the current-carrying standard coil.

[0004] Further, in order to verify the effectiveness of the magnetic moment comparator measurement method, the magnetic sample can be replaced by another current-carrying standard coil.

[0005] The magnetic moment comparator device of the present application comprises a background magnetic field generating assembly, an atomic magnetometer for measuring absolute magnetic field, a first current-carrying standard coil assembly, a magnetic sample and a measurement module.

[0006] The background magnetic field generating assembly comprises a magnetic shielding cylinder with a magnetic shielding coefficient better than 10 -3 and a background magnetic field coil placed inside the magnetic shielding cylinder. The magnetic shielding cylinder is used to realize geomagnetic shielding, and the background magnetic field coil is used to generate a background magnetic field in the magnetic shielding cylinder. The background magnetic field is in the range of 200nT to 20000nT.

[0007] The atomic magnetometer is located inside the magnetic shielding cylinder, and the direction of the circularly polarized pumping light is parallel to the direction of the background magnetic field, and the direction of the linearly polarized probe light is perpendicular to the direction of the background magnetic field. The atomic magnetometer is used to measure the magnetic field at the spatial position of the atomic chamber. The atomic magnetometer preferably adopts a pumping-detection type rubidium atomic magnetometer, which has the characteristics of high sensitivity and wide range, and the range is 100nT to 100000nT.

[0008] The first current-carrying standard coil assembly comprises a first standard coil and a first current source, the axis direction of the first standard coil is parallel to the background magnetic field, the first current source is used for passing current to the first standard coil, and the output of the first current source is controlled by the measurement module.

[0009] The magnetic moment direction of the magnetic sample is parallel to the direction of the background magnetic field, and the magnetic sample is moved into the magnetic shielding cylinder by using a sample transfer rod.

[0010] The first standard coil, the atomic gas chamber of the atomic magnetometer and the magnetic sample are sequentially placed on the center line of symmetry of the background magnetic field coil, the distance between the first standard coil and the atomic gas chamber is equal to the distance between the magnetic sample and the atomic gas chamber, when the magnetic field generated by the first standard coil and the magnetic sample at the position of the rubidium bubble is equal in size and opposite in direction, the magnetic moment comparator reaches an equilibrium state. According to this feature, the magnetic sample can be transferred to a position where the distance between the magnetic sample and the atomic gas chamber is equal to the distance between the first standard coil and the atomic gas chamber; the measurement module adjusts the current size of the first standard coil to keep the background magnetic field unchanged, the magnetic moment comparator reaches an equilibrium state, the magnetic moment generated by the magnetic sample at the position of the atomic gas chamber is equal in size and opposite in direction to the magnetic field generated by the first standard coil at the position of the atomic gas chamber, and a magnetic moment measurement result is obtained.

[0011] Preferably, the diameter of the magnetic shielding cylinder is φ500mm, and the length is greater than or equal to 700mm.

[0012] Preferably, the magnetic field gradient of the background magnetic field generated by the background magnetic field generating assembly is less than 1%.

[0013] Preferably, the size ratio of the first standard coil and the magnetic sample is not more than 5 times.

[0014] Preferably, the device can also be used for verification. The magnetic sample can be replaced by a second current-carrying standard coil assembly composed of a second standard coil and a second current source, the second current-carrying standard coil assembly can generate a magnetic moment to be measured, the second standard coil and the first standard coil are arranged to have a distance equal to that between the atomic gas chamber, and the effectiveness of the magnetic moment comparator measurement method is verified.

[0015] The application also provides a magnetic moment measurement method, which is measured by using the above measurement device and comprises the following steps:

[0016] Step 1, start the pumping-detection type rubidium atomic magnetometer, adjust the current size passed to the background magnetic field coil according to the magnetic field value measured by the pumping-detection type rubidium atomic magnetometer, so that the background magnetic field is stabilized on a background magnetic field in the range of 200nT-20000nT; and the distance between the first standard coil and the rubidium bubble is set as r0.

[0017] Step 2, move the magnetic sample into the magnetic shielding cylinder by using the sample transfer rod, so that the distance between the magnetic sample and the rubidium bubble is r0; change the output current of the first current source in real time by using the measurement module during the movement of the magnetic sample, so that the background magnetic field remains unchanged;

[0018] Step 3, calculate the magnetic moment of the first standard coil according to the expression wherein n1, I1 and R1 are the number of turns, current and radius of the first standard coil respectively; according to the fact that the magnetic moment of the magnetic sample is equal in magnitude and opposite in direction to the magnetic moment of the first standard coil, the magnetic moment of the magnetic sample can be obtained;

[0019] The method further comprises a verification process:

[0020] Step 4A: replace the magnetic sample with a second current-carrying standard coil assembly composed of a second standard coil and a second current source; set the distance between the second standard coil and the rubidium bubble to r0, and use the second current source to pass current to the second standard coil to generate a to-be-measured magnetic moment; change the output current of the first current source in real time by using the measurement module, so that the background magnetic field remains unchanged;

[0021] Step 4B: calculate the magnetic moments of the current-carrying first standard coil and the current-carrying second standard coil according to the expressions and respectively, wherein n2, I2 and R2 are the number of turns, current and radius of the second standard coil respectively; verify the effectiveness of the magnetic moment comparator measurement method by m1=m2.

[0022] Advantages:

[0023] The application discloses a magnetic moment comparator device and a measurement method, which measures an absolute magnetic field with high sensitivity by using a pumping-detection type rubidium atomic magnetometer, places a current-carrying first standard coil and a magnetic sample at positions equidistant from the rubidium bubble, takes the background magnetic field remaining unchanged as a balance condition, changes the current passed to the first standard coil in real time, and measures the magnetic moment of the magnetic sample by using the magnetic moment of the current-carrying first standard coil. In order to verify the effectiveness of the magnetic moment comparator measurement method, the magnetic sample is replaced by a current-carrying second standard coil, and the magnetic moment of the current-carrying second standard coil is measured by using the magnetic moment of the current-carrying first standard coil. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings are used to provide a further understanding of the technical solutions of the application and constitute a part of the specification. The drawings accompanying the embodiments of the application are used to explain the technical solutions of the application, but do not constitute a limitation on the technical solutions of the application.

[0025] Figure 1 FIG. 1 is a structural schematic diagram of a magnetic moment comparator device comprising a magnetic sample according to the application;

[0026] Figure 2 is a structural schematic diagram of a magnetic moment comparator device comprising a second current source and a second standard coil provided by an embodiment of the present application;

[0027] Figure 3 is a first standard coil physical schematic diagram provided by an embodiment of the present application;

[0028] Figure 4 is a second standard coil physical schematic diagram provided by an embodiment of the present application;

[0029] Figure 5 is a schematic diagram of the output magnetic field value of a pump-probe type rubidium atomic magnetometer when measuring the magnetic moment of a second standard coil by a first standard coil provided by an embodiment of the present application;

[0030] Figure 6 is a schematic diagram of the output current value of a first current source when measuring the magnetic moment of a second standard coil by a first standard coil provided by an embodiment of the present application;

[0031] The reference signs: 1 - magnetic shielding cylinder, 2 - background magnetic field coil, 3 - Helmholtz coil, 4 - rubidium bubble heating module, 5 - rubidium bubble, 6 - magnetic sample, 7 - sample transmission rod, 8 - first standard coil, 9 - first current source, 10 - circularly polarized pump laser, 11 - linearly polarized probe laser, 12 - second standard coil, 13 - second current source. DETAILED DESCRIPTION

[0032] The embodiments of the present application and the various features in the embodiments can be combined with each other on the premise of no conflict, and the formed technical solutions are all within the protection scope of the present application, which can be fully understood and implemented by the following detailed description of the embodiments of the present application combined with the accompanying drawings and embodiments.

[0033] Embodiment one

[0034] Figure 1 A structural schematic diagram of a magnetic moment comparator device comprising a magnetic sample according to an embodiment of the present application is shown, and the device comprises a magnetic shielding cylinder 1, a background magnetic field coil 2, a Helmholtz coil 3, a rubidium bubble heating module 4, a rubidium bubble 5, a magnetic sample 6, a sample transmission rod 7, a first standard coil 8, a first current source 9, a circularly polarized pump laser 10, and a linearly polarized probe laser 11.

[0035] A magnetic moment comparator device comprises a background magnetic field generating assembly, a pump-probe type rubidium atomic magnetometer, a first current-carrying standard coil assembly, a magnetic sample 6, and a measuring module.

[0036] The background magnetic field generating assembly comprises a magnetic shielding cylinder 1 and a background magnetic field coil 2 placed inside the magnetic shielding cylinder 1; the magnetic shielding cylinder 1 is used to realize geomagnetic shielding, and the background magnetic field coil 2 is used to generate a background magnetic field in the magnetic shielding cylinder 1; the background magnetic field is in the range of 200 nT to 20000 nT; the value needs to be in the range of the measurement range of various atomic magnetometers. The set value of the background magnetic field is designed in combination with the magnetic shielding cylinder to prevent the background magnetic field coil from magnetizing the magnetic shielding cylinder and causing the drift of the measurement result.

[0037] In the embodiment, the magnetic shielding cylinder 1 is cylindrical, with a diameter of φ500 mm and a length greater than or equal to 700 mm, and the background magnetic field is set to 500 nT; the magnetic field gradient of the background magnetic field generated at the position of the rubidium bubble is less than 1%.

[0038] The composition and working principle of the pumping-detection type rubidium atomic magnetometer are shown in the authorized invention patent “Rubidium Atomic Magnetometer and Magnetic Field Measurement Method Thereof” (Patent No. 201710270545.8), and the present application Figure 1 In the pumping-detection type rubidium atomic magnetometer, only a Helmholtz coil 3, a rubidium bubble heating module 4, a rubidium bubble 5, circularly polarized pumping laser 10 and linearly polarized detection laser 11 are listed, and components related to timing control, differential detection and data acquisition are omitted; wherein the Helmholtz coil 3, the rubidium bubble heating module 4 and the rubidium bubble 5 are placed in the magnetic shielding cylinder 1 of the background magnetic field generating assembly and are placed in the magnetic field uniform region of the background magnetic field coil 2; the direction of the circularly polarized pumping light is parallel to the direction of the background magnetic field, and the direction of the linearly polarized detection light is perpendicular to the direction of the background magnetic field; the pumping-detection type rubidium atomic magnetometer is used to measure the magnetic field of the spatial position of the rubidium bubble 5 in the pumping-detection type rubidium atomic magnetometer; the measurement range of the pumping-detection type rubidium atomic magnetometer is 100 nT to 100000 nT.

[0039] The first current-carrying standard coil assembly comprises a first standard coil 8 and a first current source 9; the axis direction of the first standard coil 8 is parallel to the background magnetic field, and the first current source 9 is used to pass current to the first standard coil 8; the output of the first current source 9 is controlled by a measurement module in the computer; in the embodiment of the present application, the first current source 9 is a precision current source of B2912A type of Keysight Technology Company.

[0040] The magnetic moment direction of the magnetic sample 6 is parallel to the direction of the background magnetic field, and the magnetic sample 6 is moved into the magnetic shielding cylinder by using a sample conveying rod 7;

[0041] The first standard coil 8, the rubidium bubble 5 and the magnetic sample 6 are placed on the axis of the background magnetic field coil 2 in sequence, the distance between the first standard coil 8 and the rubidium bubble 5 is equal to the distance between the magnetic sample 6 and the rubidium bubble 5, and the size ratio of the first standard coil 8 and the magnetic sample 6 should not exceed 5 times to meet the condition; when the magnetic field generated by the current-carrying first standard coil 8 and the magnetic sample 6 at the position of the rubidium bubble 5 is equal in size and opposite in direction, the magnetic moment comparator reaches the balance state. By using this feature, the magnetic sample can be transmitted to a position where the distance between the magnetic sample and the rubidium bubble 5 is equal to the distance between the first standard coil and the rubidium bubble 5; the measurement module adjusts the current size of the first standard coil to keep the background magnetic field unchanged, the magnetic moment comparator reaches the balance state, the magnetic field generated by the magnetic sample at the position of the rubidium bubble 5 is equal in size and opposite in direction to the magnetic field generated by the first standard coil at the position of the rubidium bubble 5, and the magnetic moment measurement result is obtained.

[0042] The embodiment specifically illustrates a magnetic moment measurement method using the magnetic moment comparator device, and the method comprises the following steps:

[0043] Step 1, start the pumping-detection type rubidium atomic magnetometer, adjust the current size flowing into the background magnetic field coil according to the magnetic field value measured by the pumping-detection type rubidium atomic magnetometer, set the background magnetic field to 500 nT, and set the distance r0 between the first standard coil and the rubidium bubble to 20 cm.

[0044] Step 2A, move the magnetic sample into the magnetic shielding cylinder by using the sample transmission rod, so that the distance between the magnetic sample and the rubidium bubble is r0; change the output current of the first current source in real time by using the measurement module during the movement of the magnetic sample, so that the background magnetic field remains unchanged.

[0045] Step 2B, according to the expression m1=n1I1πR1 2 Calculate the magnetic moment of the first standard coil, wherein n1, I1 and R1 are the number of turns, the current and the radius of the first standard coil respectively; according to the fact that the magnetic moment of the magnetic sample is equal in size and opposite in direction to the magnetic moment of the current-carrying first standard coil, the magnetic moment of the magnetic sample can be obtained.

[0046] Example two

[0047] In order to verify the effectiveness of the magnetic moment comparator measurement method, the magnetic sample is replaced by a second standard coil in the embodiment of the application, an experiment for measuring the magnetic moment of the current-carrying second standard coil by using the magnetic moment of the current-carrying first standard coil is designed, and the structural schematic diagram of the experimental device is as shown in Figure 2As shown in the figure, the distance between the first standard coil 8 and the rubidium bubble 5 is set to 20 cm, and the distance between the second standard coil 12 and the rubidium bubble 5 is also set to 20 cm; the first standard coil 8 and the second standard coil 12 are both made by winding a single layer of copper wire with a diameter of 0.45 mm on a glass tube with a diameter of 11 mm, and the number of turns of the first standard coil 8 and the second standard coil 12 is 30 turns and 15 turns, respectively; the second current source 13 is a precision current source of B2962A type from DE Company.

[0048] This embodiment specifically illustrates the verification process of the above measurement scheme by using the magnetic moment comparator device.

[0049] Specifically includes:

[0050] Step 1: Start the pumping-detection type rubidium atomic magnetometer, adjust the current flowing into the background magnetic field coil 2 according to the magnetic field value measured by the pumping-detection type rubidium atomic magnetometer, so that the background magnetic field is stabilized on a background magnetic field in the range of 200 nT to 20000 nT; set the distance between the first standard coil 8 and the second standard coil 12 and the rubidium bubble 5 to be r0.

[0051] In an example, the distance between the second standard coil 12 and the rubidium bubble 5 can be set to r0 as 20 cm.

[0052] Step 2: Use the second current source 13 to pass current into the second standard coil 12 to generate a magnetic moment to be measured; use the measurement module to change the output current of the first current source 9 in real time, so that the background magnetic field remains unchanged.

[0053] In this step, the second current source 13 can be used to pass 100 mA, 200 mA, 300 mA, …, 1000 mA current into the second standard coil 12 in turn for 60 seconds, to generate a series of magnetic moments to be measured, and the direction of the magnetic field generated by the current-carrying second standard coil 12 at the position of the rubidium bubble 5 is opposite to that of the background magnetic field; the measurement module is used to change the output current of the first current source 9 in real time, so that the background magnetic field remains unchanged.

[0054] When the first standard coil 8 is used to measure the magnetic moment of the current-carrying second standard coil 12, the output magnetic field value of the pumping-detection type rubidium atomic magnetometer is as shown in the figure. Figure 5 As shown in the figure, when the current flowing into the second standard coil 12 increases, the magnetic field at the position of the rubidium bubble 5 measured by the pumping-detection type rubidium atomic magnetometer decreases, and the measurement software changes the output current of the first current source 9 in real time according to the measurement result of the pumping-detection type rubidium atomic magnetometer, so that the background magnetic field returns to 500 nT.

[0055] Step 3: According to the expressions and The magnetic moments of the first standard coil 8 and the second standard coil 12 are calculated respectively, where n1, I1 and R1 are the number of turns, current and radius of the first standard coil 8, respectively, and n2, I2 and R2 are the number of turns, current and radius of the second standard coil 12, respectively; the effectiveness of the magnetic moment comparator measurement method is verified by m1 = m2.

[0056] When measuring the magnetic moment of the second standard current-carrying coil 12 using the first standard current-carrying coil 8, the current value output by the first current source 9 is as follows: Figure 6 As shown, when the second current source 13 sequentially supplies currents of 100mA, 200mA, 300mA, 400mA, 500mA, 600mA, 700mA, 800mA, 900mA, and 1000mA to the second standard coil 12, in order to maintain the background magnetic field stable at 500nT, the average values ​​of the current supplied by the first current source 9 to the first standard coil 8 are 50.2mA, 100.7mA, 151.2mA, 201.8mA, 252.1mA, 302.3mA, 352.5mA, 402.5mA, 452.4mA, and 502.2mA, respectively. According to the expression m1=n1I1πR1 2 Calculations show that n1 is 30, R1 is 0.0055m, and the experimental magnetic moment value of the first standard current-carrying coil 8 is 0.143 × 10⁻⁶. -3 A·m 2 0.287×10 -3 A·m 2 0.431×10 -3 A·m 2 0.575×10 -3 A·m 2 0.719×10 -3 A·m 2 0.862×10 -3 A·m 2 1.005×10 -3 A·m 2 1.148×10 -3 A·m 2 1.290×10 -3 A·m 2 and 1.432×10 -3 A·m 2 According to the expression Calculations show that n2 is 15, R2 is 0.0055m, and the theoretical magnetic moment of the second standard current-carrying coil 12 is 0.143 × 10⁻⁶. -3 A·m 2 0.285×10 -3 A·m 2 0.428×10 -3 A·m2 0.570 x 10 -3 A·m 2 0.713 x 10 -3 A·m 2 0.855 x 10 -3 A·m 2 0.998 x 10 -3 A·m 2 1.140 x 10 -3 A·m 2 1.283 x 10 -3 A·m 2 1.425 x 10 - 3 A·m 2 According to m1 = m2, the results of "(experimental value - theoretical value) / theoretical value" of the current-carrying second standard coil 12 are all less than 1%, which indicates that the magnetic moment comparator device and the measurement method are effective.

[0057] In summary, the embodiments are only preferred embodiments of the present disclosure, and are not intended to limit the protection scope of the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A magnetic moment comparator apparatus, characterized by, The device comprises a background magnetic field generating component, an atomic magnetometer for measuring absolute magnetic field, a first current standard coil component, a magnetic sample (6) and a measuring module; The base magnetic field generating assembly comprises a magnetic shielding cylinder (1) with a magnetic shielding coefficient superior to 10 -3 and a base magnetic field coil (2) placed inside the magnetic shielding cylinder (1); the magnetic shielding cylinder (1) is used to realize geomagnetic shielding, and the base magnetic field coil (2) is used to generate a base magnetic field in the magnetic shielding cylinder (1); The atomic magnetometer is located in a magnetic shielding cylinder (1), the direction of the circularly polarized pumping light is parallel to the direction of the background magnetic field, and the direction of the linearly polarized probe light is perpendicular to the direction of the background magnetic field; the atomic magnetometer is used for measuring the magnetic field at the space position of the atomic gas chamber; The first current standard coil component comprises a first standard coil (8) and a first current source (9), the axis direction of the first standard coil (8) is parallel to the background magnetic field, the first current source (9) is used for passing current to the first standard coil (8), and the output of the first current source (9) is controlled by the measuring module; The magnetic moment direction of the magnetic sample (6) is parallel to the direction of the background magnetic field, and the magnetic sample (6) is moved into the magnetic shielding cylinder by using a sample conveying rod (7); The first standard coil (8), the atomic gas chamber of the atomic magnetometer and the magnetic sample (6) are sequentially placed on the center line of the background magnetic field coil (2), the magnetic sample (6) is conveyed to a position with a distance from the atomic gas chamber equal to the distance between the first standard coil (8) and the atomic gas chamber; the measuring module adjusts the current size of the first standard coil (8) to keep the background magnetic field unchanged, the magnetic moment comparator reaches an equilibrium state, and the magnetic moment generated by the magnetic sample (6) at the position of the atomic gas chamber is equal in size and opposite in direction to the magnetic field generated by the first standard coil (8) at the position of the atomic gas chamber.

2. The magnetic moment comparator apparatus of claim 1, wherein, The atomic magnetometer for measuring absolute magnetic field adopts a pumping-detection type rubidium atomic magnetometer to measure the magnetic field at the space position of a rubidium bubble (5) in the pumping-detection type rubidium atomic magnetometer; the first standard coil (8), the rubidium bubble (5) in the pumping-detection type rubidium atomic magnetometer and the magnetic sample (6) are sequentially placed on the axis of the background magnetic field coil (2); the range of the pumping-detection type rubidium atomic magnetometer is 100 nT to 100000 nT, and the background magnetic field is in the range of 200 nT to 20000 nT.

3. The magnetic moment comparator apparatus of claim 2, wherein, The diameter of the magnetic shielding cylinder (1) is φ500 mm, and the length is greater than or equal to 700 mm.

4. The magnetic moment comparator apparatus of claim 2, wherein, The magnetic field gradient of the background magnetic field generated by the background magnetic field generating component is less than 1%.

5. The magnetic moment comparator apparatus of claim 2, wherein, The size ratio of the first standard coil (8) and the magnetic sample (6) is not more than 5 times.

6. The magnetic moment comparator apparatus of claim 2, wherein, The magnetic sample (6) is replaced by a second current standard coil component composed of a second standard coil (12) and a second current source (13), the second current standard coil component can generate a magnetic moment to be measured, the second standard coil and the first standard coil are arranged to have a distance equal to that between the atomic gas chamber, and the effectiveness of the magnetic moment comparator measurement method is verified.

7. A measuring method based on a magnetic moment comparator, characterized in that The method is applied to the magnetic moment comparator device of any one of claims 2-6, and the method comprises: Step 1, starting the pumping-detection type rubidium atomic magnetometer, adjusting the current size passed to the background magnetic field coil (2) according to the magnetic field value measured by the pumping-detection type rubidium atomic magnetometer, so that the background magnetic field is stabilized on a background magnetic field in the range of 200 nT to 20000 nT; setting the distance between the first standard coil (8) and the rubidium bubble (5) as r0. Step 2, moving the magnetic sample (6) into the magnetic shielding cylinder by using the sample transfer rod (7) to make the magnetic sample (6) have a distance r0 from the rubidium bubble (5); changing the output current of the first current source (9) in real time by using the measurement module during the movement of the magnetic sample (6) to keep the background magnetic field unchanged; Step 3, according to the expression m1 = n1I1πR1 2 The magnetic moment of the first standard coil (8) is calculated, where n1, I1 and R1 are the number of turns, the current and the radius of the first standard coil (8) respectively; the magnetic moment of the magnetic sample (6) is obtained according to the fact that the magnetic moment of the magnetic sample (6) is equal in magnitude and opposite in direction to the magnetic moment of the first standard coil (8).

8. The method of claim 7, wherein, The method further comprises a verification process: Step 4A: replacing the magnetic sample (6) with a second current-carrying standard coil assembly composed of a second standard coil (12) and a second current source (13); the second standard coil (12) is arranged at a position with a distance r0 from the rubidium bubble (5), and the second current source (13) is used to pass current to the second standard coil (12) to generate a to-be-measured magnetic moment; the output current of the first current source (9) is changed in real time by using the measurement module to keep the background magnetic field unchanged; Step 4B: Calculate the magnetic moment of the first (8) and second (12) standard coils according to the expressions and respectively, where n2, I2, and R2 are the number of turns, current, and radius of the second standard coil (12); verify the validity of the magnetic moment comparator measurement method by m1 = m2.

Images