Apparatus and method for segmenting compensation of magnetic field gradients in dDNP polarization systems

Abstract

The application discloses a device and method for compensating magnetic field gradient of a segmented dDNP polarization system, which comprises a gradient monitoring module and a dynamic compensation module. The gradient monitoring module comprises a magnetic sensor combination, which comprises at least two magnetic sensors distributed along the transfer path direction of a sample, and the magnetic sensors are used for detecting a first gradient magnetic field corresponding to the transfer path of the sample. The dynamic compensation module comprises a segmented gradient coil, which is arranged along the transfer path of the sample to form multiple independent coil units. The current of each independent coil unit is independently adjusted according to the first gradient magnetic field, so that the segmented adjustment and overall homogenization of the magnetic field gradient of the transfer path are realized. The dynamic magnetic field gradient inside the polarizer is measured in real time by using the magnetic sensor combination, and the precise compensation of the gradient magnetic field is realized through the reverse compensation of the segmented gradient coil, so that the high polarization fidelity of the sample in the transfer process is ensured.

Description

Technical Field

[0001] This invention relates to the field of nuclear magnetic resonance technology, specifically to a device and method for segmented compensation of the magnetic field gradient in a dDNP polarization system. Background Technology

[0002] Dissolution-dependent nuclear magnetic resonance (dDNP) technology involves polarizing free radicals (unpaired electrons) at ultra-low temperatures and under a high magnetic field. The high spin polarizability of electrons is then transferred to the nucleus through electron-nuclear coupling, enhancing the nuclear spin polarizability of the low-temperature sample. After polarization at low temperatures, the sample is rapidly melted into a liquid using a high-temperature solvent and quickly transferred to room temperature for detection. This technique can ultimately enhance the NMR signal intensity of the relevant nuclei by 3-5 orders of magnitude, enabling real-time monitoring of in vivo metabolic processes, chemical reactions, and real-time imaging. A key challenge of dDNP is balancing the need for rapid transfer to limit signal loss due to nuclear spin relaxation with ensuring a uniform and stable magnetic field during the transfer process. The magnetic field plays a crucial role during sample transfer within the polarizer, influencing the relaxation process of electrons and nuclear spins. Changes in the magnetic field affect the spin distribution and polarization characteristics. Especially under unstable or highly variable magnetic fields, decoherence and polarization distortion can occur, reducing polarization fidelity.

[0003] The current main method involves tightly winding a 1mm diameter insulated copper wire around the sample transfer tube to form a solenoid during the transfer process. When energized, the solenoid generates a stable magnetic field, ensuring the magnetic field strength remains ≥75mT throughout the transfer. This design primarily aims to reduce spin decoherence and rapid polarization decay by applying an additional magnetic field outside the polarization system. However, the magnetic field of the superconducting magnet inside the polarization system exhibits significant axial variations. Due to the lack of a real-time magnetic field gradient monitoring system, the aforementioned method struggles to accurately model and compensate for these magnetic field variations within the transfer path. The fixedly wound solenoid only provides a static reference field strength (≥75mT), failing to provide accurate dynamic compensation for nonlinear, spatially varying gradient magnetic fields. Therefore, new methods are needed to improve the magnetic field uniformity within the transfer path of the polarization system. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a device and method for segmented compensation of the magnetic field gradient in a dDNP polarization system. This method employs a combination of magnetic sensors to measure the dynamic magnetic field gradient inside the polarizer in real time and generates a reverse compensation field through segmented gradient coils to achieve precise compensation of the gradient magnetic field, thereby ensuring high polarization fidelity of the sample during the transfer process.

[0005] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0006] According to a first aspect of this application, a device for segmented compensation of the magnetic field gradient of a dDNP polarization system is provided, comprising:

[0007] A gradient monitoring module includes a magnetic sensor assembly disposed above the sample in a polarizer. The magnetic sensor assembly includes at least two magnetic sensors distributed along the transfer path direction of the sample. The at least two magnetic sensors are used to detect the first gradient magnetic field corresponding to the transfer path of the sample.

[0008] The dynamic compensation module includes a segmented gradient coil, which comprises multiple independent coil units arranged along the sample transfer path. By adjusting the current of each independent coil unit, a second gradient magnetic field is generated to reduce or eliminate the magnetic field gradient in different sections of the first gradient magnetic field corresponding to the transfer path.

[0009] In some embodiments of this application, based on the foregoing scheme, a control system and a current drive system are further included, wherein the current drive system is electrically connected to the control system, and the segmented gradient coil is electrically connected to the current drive system, wherein...

[0010] The control system is used to generate a steady-state current signal of a specific magnitude and direction based on the first gradient magnetic field;

[0011] The current drive system outputs a steady-state current of a specific magnitude and direction to the segmented gradient coil based on a steady-state current signal. The segmented gradient coil generates a second gradient magnetic field through the steady-state current of a specific magnitude and direction.

[0012] In some embodiments of this application, based on the foregoing scheme, when the magnetic field gradient of the transfer path is linear or nonlinear, the magnetic sensor assembly includes at least two magnetic sensors, and the at least two magnetic sensors are uniformly distributed along the transfer path direction of the sample.

[0013] In some embodiments of this application, based on the foregoing scheme, it further includes at least two channels and at least two signal conditioning systems and a digital platform. Each magnetic sensor is electrically connected to one of the channels, each channel is electrically connected to one of the signal conditioning systems, and all the signal conditioning systems are electrically connected to the digital platform.

[0014] After the channel acquires the magnetic field direction and magnetic field strength of the magnetic sensor electrically connected to the channel, the signal conditioning system electrically connected to the channel is used to preprocess the magnetic field direction and magnetic field strength;

[0015] The digital platform is used to acquire the signal and direction of the first gradient magnetic field based on the magnetic field direction and magnetic field strength of all the magnetic sensors.

[0016] In some embodiments of this application, based on the foregoing scheme:

[0017] If the magnetic sensor is a nuclear magnetic resonance magnetic sensor, it includes an excitation system, which is used to excite the sample by radio frequency.

[0018] If the magnetic sensor is a Hall effect sensor, an anisotropic magnetoresistive sensor, or a giant magnetoresistive sensor, then an excitation system is not required.

[0019] In some embodiments of this application, based on the foregoing scheme, the geometry of the independent coil unit includes, but is not limited to, circular coil, rectangular coil, saddle-shaped coil, or spiral coil; by passing a controllable steady-state or time-varying current through the independent coil unit, the required second gradient magnetic field is formed, thereby reducing or eliminating the magnetic field gradient in different sections of the first gradient magnetic field corresponding to the transfer path.

[0020] In some embodiments of this application, based on the foregoing scheme, the control system outputs a compensation current command signal to the segmented gradient coil through a controller, and the steady-state current signal is the compensation current command signal.

[0021] According to a second aspect of this application, a method for segmented compensation of the magnetic field gradient in a dDNP polarization system is provided, comprising:

[0022] A magnetic sensor assembly is set above the sample in the polarizer. The magnetic sensor assembly includes at least two magnetic sensors, which are distributed along the transfer path of the sample. The first gradient magnetic field corresponding to the transfer path of the sample is detected by the at least two magnetic sensors.

[0023] A segmented gradient coil is provided, comprising multiple independent coil units arranged along the sample transfer path. By adjusting the current of each independent coil unit, a second gradient magnetic field is generated to reduce or eliminate the magnetic field gradient in different sections of the first gradient magnetic field corresponding to the transfer path.

[0024] In some embodiments of this application, based on the foregoing scheme, the following further methods are also included:

[0025] Along the transfer path of the sample in the polarizer, the axial magnetic field gradient value at the current position is obtained based on the first gradient magnetic field.

[0026] A steady-state current signal of a specific magnitude and direction is generated based on the axial magnetic field gradient value at the current location;

[0027] Based on the segmented gradient coil outputting a steady-state current of a specific magnitude and direction, the segmented gradient coil generates a second gradient magnetic field through the steady-state current of a specific magnitude and direction.

[0028] In some embodiments of this application, based on the foregoing scheme, the formula for calculating the axial magnetic field gradient value at the current position is as follows:

[0029] The formula for calculating the axial magnetic field gradient at the current location is:

[0030]

[0031] in, Let be the magnetic field strength measured by the i-th magnetic sensor; Let be the axial position coordinates of the i-th magnetic sensor; Let be the local gradient value in the segment between the i-th and i+1-th magnetic sensors.

[0032] The beneficial effects of this application are as follows:

[0033] This application provides a device and method for segmented compensation of magnetic field gradient in a dDNP polarization system. The method detects the first gradient magnetic field corresponding to the transfer path of the sample using a magnetic sensor, and then generates a second gradient magnetic field using a segmented gradient coil. The magnitudes of the first gradient magnetic field and the second gradient magnetic field are approximately equal and their directions are opposite. The first gradient magnetic field and the second gradient magnetic field are superimposed, which significantly reduces or reduces the net magnetic field gradient along the transfer path of the sample in the polarizer to zero, thereby achieving magnetic field homogenization.

[0034] This application provides a device and method for segmented compensation of the magnetic field gradient in a dDNP polarization system. The device comprises a gradient monitoring module and a dynamic compensation module working in concert to achieve real-time modeling and suppression of the gradient field along the transfer path. When the sample is transferred inside the polarizer, the system uses a combination of magnetic sensors to accurately measure the gradient magnetic field above the sample region. Subsequently, based on the measurement results, the dynamic compensation module applies a specific steady-state current to the segmented gradient coils to generate a precise compensation magnetic field. This process effectively ensures the uniformity of the magnetic field during sample transfer, thereby significantly improving the polarization fidelity of the sample.

[0035] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0036] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and are intended to explain the invention, but do not constitute an undue limitation thereof. In the drawings:

[0037] Figure 1 This is a schematic diagram of a device for segmented compensation of the magnetic field gradient of a dDNP polarization system according to the present invention.

[0038] Figure 2 This is a flowchart of a method for segmented compensation of the magnetic field gradient in a dDNP polarization system according to the present invention. Detailed Implementation

[0039] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] It should be understood that the terms "comprising" and other similar expressions in the specification, claims, and accompanying drawings of this invention are intended to cover a non-exclusive inclusion, such as a process, method, system, or apparatus that includes a series of steps or units and is not limited to the listed steps or units. Furthermore, "first" and "second" are used to distinguish different objects and are not intended to describe a specific order.

[0041] Please see Figure 1 A schematic diagram of a device for segmented compensation of the magnetic field gradient in a dDNP polarization system is shown. This embodiment provides a device for segmented compensation of the magnetic field gradient in a dDNP polarization system, comprising:

[0042] The gradient monitoring module includes a magnetic sensor assembly positioned above the sample in the polarizer. The magnetic sensor assembly includes at least two magnetic sensors distributed along the transfer path of the sample. The at least two magnetic sensors are used to detect the first gradient magnetic field corresponding to the transfer path of the sample. The magnetic sensors are configured as fluxgate sensors.

[0043] The dynamic compensation module includes a segmented gradient coil, which comprises multiple independent coil units arranged along the sample transfer path. By adjusting the current of each independent coil unit, a second gradient magnetic field is generated to reduce or eliminate the magnetic field gradient in different sections of the first gradient magnetic field corresponding to the transfer path, thereby achieving segmented adjustment and overall homogenization of the magnetic field gradient of the transfer path.

[0044] In this embodiment, the magnetic field gradient of each segment of the sample transfer path in the polarizer is different. In order to accurately control the magnetic field gradient compensation of each segment, this embodiment provides a segmented compensation device for the magnetic field gradient of the dDNP polarization system. The device detects the first gradient magnetic field corresponding to the sample transfer path through a magnetic sensor, and then generates a second gradient magnetic field through a segmented gradient coil. The magnitudes of the first gradient magnetic field and the second gradient magnetic field are approximately equal and opposite in direction. The first gradient magnetic field and the second gradient magnetic field are superimposed, so that the net magnetic field gradient along the sample transfer path in the polarizer is significantly reduced or returns to zero, thereby achieving magnetic field homogenization.

[0045] In this embodiment, the device consists of a gradient monitoring module and a dynamic compensation module working in tandem to achieve real-time modeling and suppression of the gradient field along the transfer path. The core technology lies in the precise measurement of the gradient magnetic field generated above the sample region of the polarizer using a combination of magnetic sensors during sample transfer. Subsequently, the dynamic compensation module performs precise compensation by applying a specific steady-state current to the segmented gradient coils. This process effectively ensures the uniformity of the magnetic field during sample transfer, thereby significantly improving the polarization fidelity of the sample.

[0046] In this embodiment, two adjacent magnetic sensors are rigidly mounted on the sample transfer device with a fixed spacing. The sample transfer device is located inside the polarizer and has a transfer path. The magnetic sensors are precisely arranged along the direction of the main magnetic field (Z-axis). During the sample transfer process, the magnetic sensors measure the absolute magnetic field strength of their respective positions in real time and synchronously.

[0047] In some embodiments of this example, a control system and a current driving system are also included. The current driving system is electrically connected to the control system, and the segmented gradient coil is electrically connected to the current driving system. The control system is used to generate a steady-state current signal of a specific magnitude and a specific direction based on the first gradient magnetic field.

[0048] The current-driven system outputs a steady-state current of a specific magnitude and direction to a segmented gradient coil based on a steady-state current signal. The segmented gradient coil generates a second gradient magnetic field through the steady-state current of a specific magnitude and direction.

[0049] In this embodiment, because the magnetic field gradient of each segment of the sample transfer path inside the polarizer is different, different currents are applied to the segmented gradient coil to accurately control the magnetic field gradient compensation of each segment.

[0050] In some embodiments of this example, when the magnetic field gradient of the transfer path is linear or nonlinear, the magnetic sensor assembly includes at least two magnetic sensors, and the at least two magnetic sensors are uniformly distributed along the transfer path direction of the sample.

[0051] In some embodiments of this example, each magnetic sensor is controlled by a separate channel, and each channel has its own independent signal conditioning system. During measurement, the digital platform controls each channel to maintain synchronous excitation, acquisition, and frequency measurement to ensure the validity of the magnetic gradient data.

[0052] Specifically, the device for segmented compensation of the magnetic field gradient of a dDNP polarization system provided in this embodiment further includes at least two channels, at least two signal conditioning systems, and a digital platform. Each magnetic sensor is electrically connected to one channel, each channel is electrically connected to one signal conditioning system, and all signal conditioning systems are electrically connected to the digital platform.

[0053] After the channel acquires the magnetic field direction and magnetic field strength of the magnetic sensor electrically connected to the channel, the signal conditioning system electrically connected to the channel is used to preprocess the magnetic field direction and magnetic field strength.

[0054] The digital platform is used to acquire the signal and direction of the first gradient magnetic field based on the magnetic field direction and magnetic field strength of all magnetic sensors.

[0055] In some embodiments of this example, the magnetic sensor may be a nuclear magnetic resonance sensor or other types (such as Hall effect, anisotropic magnetoresistive, and giant magnetoresistive sensors). If it is a nuclear magnetic resonance sensor, an excitation system is required; this subsystem is responsible for applying radio frequency excitation to the sample and is an essential component for its normal operation. In contrast, sensors based on solid-state effects, such as the Hall effect, can operate without such an excitation system, resulting in a simpler system configuration.

[0056] In some embodiments of this example, the segmented gradient coil includes multiple independent coil units, the geometry of which includes, but is not limited to, circular coils, rectangular coils, saddle-shaped coils, or spiral coils; by passing a controllable steady-state or time-varying current through the independent coil units, the desired second gradient magnetic field is formed, thereby reducing or eliminating the magnetic field gradient in different sections of the first gradient magnetic field corresponding to the transfer path.

[0057] In one specific embodiment, the independent coil unit includes a pair of parallel, coaxial circular coils with the same radius, and the two circular coils are supplied with steady-state currents of equal magnitude and opposite direction, wherein the circular coils are Maxwell coils.

[0058] The segmented gradient coil includes multiple Maxwell coils. Each Maxwell coil consists of a pair of parallel, coaxial circular coils with the same radius. Both circular coils are supplied with steady-state currents of equal magnitude and opposite direction.

[0059] The key feature of multiple Maxwell coils lies in their ability to generate a highly linear and controllable gradient magnetic field within a specific region. The control unit commands the power supply to the Maxwell coils, injecting specific steady-state compensation currents into each of the multiple Maxwell coils. This current value is precisely set and maintained stable, ensuring the generation of a second gradient magnetic field along the Z-axis that precisely cancels out the detected first gradient magnetic field within its effective region. Throughout the sample transfer within the dDNP polarization system, the system continuously operates, monitoring any minute changes in the magnetic field gradient in real time and maintaining a high degree of magnetic field uniformity in the target region by dynamically adjusting the current in the Maxwell coils.

[0060] In this way, different currents are applied to each group of Maxwell coils, and each group of Maxwell coils is independently controlled, precisely controlling the magnetic field gradient for compensation in each path segment.

[0061] In the sample transfer path in the polarizer, the magnetic field gradient is different for each segment. Only by passing different currents through each Maxwell coil can the compensated magnetic field gradient for each segment be precisely controlled.

[0062] In this embodiment, the response time of the entire closed loop, from gradient measurement, transmission, calculation to current output and activation, is 1.5ms-2.5ms.

[0063] In some embodiments of this example, the control system outputs a compensation current command signal to the segmented gradient coil through a PID controller.

[0064] Specifically, the control system receives real-time gradient data from the gradient monitoring module, calculates the gradient data, inputs it into the PID controller, compares it with the preset gradient target value (0T / m), and outputs a compensation current command signal. The current drive system receives the compensation current command signal (I_set command) from the control system and quickly and accurately outputs a steady-state current of a specific magnitude and direction to multiple sets of Maxwell coils. This current source has high stability, low ripple, and fast response characteristics. After the calculated I_set is applied to the multiple sets of Maxwell coils, a second magnetic field gradient is generated in their internal space (i.e., the transfer path region), which is approximately equal in magnitude to the first magnetic field gradient but opposite in direction. The second magnetic field gradient is superimposed on the magnetic field inside the polarizer, causing the net magnetic field gradient at the current position to be significantly reduced or reduced to zero, thereby achieving magnetic field homogenization.

[0065] According to the second aspect of this application, such as Figure 2 As shown, this embodiment provides a method for segmented compensation of the magnetic field gradient in a dDNP polarization system, including:

[0066] Step S1: Set up a magnetic sensor assembly. The magnetic sensor assembly is located above the sample in the polarizer. The magnetic sensor assembly includes at least two magnetic sensors. The at least two magnetic sensors are distributed along the transfer path of the sample. The first gradient magnetic field corresponding to the transfer path of the sample is detected by the at least two magnetic sensors.

[0067] Step S2: Set up a segmented gradient coil, which includes multiple independent coil units set along the sample transfer path. By adjusting the current of each independent coil unit, a second gradient magnetic field is generated to reduce or eliminate the magnetic field gradient of different sections in the first gradient magnetic field corresponding to the transfer path, thereby realizing the segmented adjustment and overall homogenization of the magnetic field gradient of the transfer path.

[0068] In some embodiments of this example, the method for segmented compensation of the magnetic field gradient of a dDNP polarization system provided in this example further includes:

[0069] Along the transfer path of the sample in the polarizer, the axial magnetic field gradient value at the current position is obtained based on the first gradient magnetic field.

[0070] A steady-state current signal of a specific magnitude and direction is generated based on the axial magnetic field gradient value at the current location;

[0071] Based on the segmented gradient coil outputting a steady-state current of a specific magnitude and direction, the segmented gradient coil generates a second gradient magnetic field through the steady-state current of a specific magnitude and direction.

[0072] During sample transfer within the polarizer, the sensor spacing and real-time magnetic field strength difference at the current sample position are measured in real time, and the axial magnetic field gradient value at the current position is calculated and output in real time. Subsequently, the calculated axial magnetic field gradient value is transmitted in real time to the control system of the dynamic compensation module via a high-speed data interface (such as Ethernet or CAN bus).

[0073] In some embodiments of this example, the formula for calculating the axial magnetic field gradient value at the current position is as follows:

[0074]

[0075] in, Let be the magnetic field strength measured by the i-th magnetic sensor; Let be the axial position coordinates of the i-th magnetic sensor; Let be the local gradient value in the segment between the i-th and i+1-th magnetic sensors.

[0076] The dynamic compensation module accurately compensates for the axial magnetic field gradient value at the current position by applying a specific steady-state current to the segmented gradient coil at the current position.

[0077] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0078] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for segmented compensation of the magnetic field gradient in a dDNP polarization system, characterized in that, include: A gradient monitoring module includes a magnetic sensor assembly positioned above the sample in the polarizer. The magnetic sensor assembly comprises at least two magnetic sensors distributed along the sample transfer path. These at least two magnetic sensors detect a first gradient magnetic field corresponding to the sample transfer path. Along the sample transfer path in the polarizer, the axial magnetic field gradient value at the current position is obtained based on the first gradient magnetic field, calculated using the following formula: in, Let be the magnetic field strength measured by the i-th magnetic sensor; Let be the axial position coordinates of the i-th magnetic sensor; Let be the local gradient value in the segment between the i-th and i+1-th magnetic sensors; A steady-state current signal of a specific magnitude and direction is generated based on the axial magnetic field gradient value at the current location; The dynamic compensation module includes a segmented gradient coil, which comprises multiple independent coil units arranged along the sample transfer path. By adjusting the current of each independent coil unit, a steady-state current of a specific magnitude and direction is output based on the segmented gradient coil. The segmented gradient coil generates a second gradient magnetic field through the steady-state current of a specific magnitude and direction, thereby reducing or eliminating the magnetic field gradient in different segments of the first gradient magnetic field corresponding to the transfer path.

2. The device for segmented compensation of the magnetic field gradient of a dDNP polarization system according to claim 1, characterized in that: It also includes a control system and a current drive system, wherein the current drive system is electrically connected to the control system, and the segmented gradient coil is electrically connected to the current drive system. The control system is used to generate a steady-state current signal of a specific magnitude and direction based on the first gradient magnetic field; The current drive system outputs a steady-state current of a specific magnitude and direction to the segmented gradient coil based on a steady-state current signal. The segmented gradient coil generates a second gradient magnetic field through the steady-state current of a specific magnitude and direction.

3. The device for segmented compensation of the magnetic field gradient of a dDNP polarization system according to claim 1, characterized in that: When the magnetic field gradient of the transfer path is linear or nonlinear, the magnetic sensor assembly includes at least two magnetic sensors, which are uniformly distributed along the transfer path of the sample.

4. The device for segmented compensation of the magnetic field gradient of a dDNP polarization system according to claim 1, characterized in that: It also includes at least two channels, at least two signal conditioning systems, and a digital platform. Each magnetic sensor is electrically connected to one of the channels, each channel is electrically connected to one of the signal conditioning systems, and all the signal conditioning systems are electrically connected to the digital platform. After the channel acquires the magnetic field direction and magnetic field strength of the magnetic sensor electrically connected to the channel, the signal conditioning system electrically connected to the channel is used to preprocess the magnetic field direction and magnetic field strength; The digital platform is used to acquire the signal and direction of the first gradient magnetic field based on the magnetic field direction and magnetic field strength of all the magnetic sensors.

5. The device for segmented compensation of the magnetic field gradient of a dDNP polarization system according to claim 4, characterized in that: If the magnetic sensor is a nuclear magnetic resonance magnetic sensor, it includes an excitation system, which is used to excite the sample by radio frequency. If the magnetic sensor is a Hall effect sensor, an anisotropic magnetoresistive sensor, or a giant magnetoresistive sensor, then an excitation system is not required.

6. The device for segmented compensation of the magnetic field gradient of a dDNP polarization system according to claim 2, characterized in that: The geometry of the independent coil unit includes circular coils, rectangular coils, saddle-shaped coils, or spiral coils; by passing a controllable steady-state or time-varying current through the independent coil unit, the required second gradient magnetic field is formed, thereby reducing or eliminating the magnetic field gradient in different sections of the first gradient magnetic field corresponding to the transfer path.

7. The device for segmented compensation of the magnetic field gradient of a dDNP polarization system according to claim 2, characterized in that: The control system outputs a compensation current command signal to the segmented gradient coil through the controller, and the steady-state current signal is the compensation current command signal.

8. A method for segmented compensation of the magnetic field gradient in a dDNP polarization system, characterized in that, include: A magnetic sensor assembly is configured, positioned above the sample in the polarizer. The assembly includes at least two magnetic sensors distributed along the sample transfer path. The at least two magnetic sensors detect a first gradient magnetic field corresponding to the sample transfer path. The axial magnetic field gradient value at the current position is obtained based on the first gradient magnetic field along the sample transfer path in the polarizer, calculated using the following formula: in, Let be the magnetic field strength measured by the i-th magnetic sensor; Let be the axial position coordinates of the i-th magnetic sensor; Let be the local gradient value in the segment between the i-th and i+1-th magnetic sensors; A steady-state current signal of a specific magnitude and direction is generated based on the axial magnetic field gradient value at the current location; A segmented gradient coil is provided, comprising multiple independent coil units arranged along the sample transfer path. By adjusting the current of each independent coil unit, a steady-state current of a specific magnitude and direction is output based on the segmented gradient coil. The segmented gradient coil generates a second gradient magnetic field through the steady-state current of a specific magnitude and direction, thereby reducing or eliminating the magnetic field gradient in different sections of the first gradient magnetic field corresponding to the transfer path.

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