Melting DNP cross polarization probe

Abstract

The invention relates to a melting DNP cross polarization probe which comprises a resonant cavity, an intra-cavity assembly, a flange plate, a double-resonant circuit and a radio frequency rod. The resonant cavity is of a hollow cylindrical structure with an upper opening; the intra-cavity assembly is arranged in the resonant cavity and comprises a coil unit arranged in the middle of the resonant cavity and a reflector unit arranged on the outer side of the coil unit; the flange plate is buckled at the upper end of the resonant cavity, a first through hole is formed in the middle of the flange plate, a second through hole is formed in the outer side of the first through hole, and the double-resonant circuit is arranged at the upper end of the flange plate; the radio frequency rod passes through the second through hole and is connected with the coil unit in the resonant cavity. According to the invention, the application of the cross polarization technology means in the melting dynamic nuclear polarization technology is successfully realized, and the technical problems of low detection nuclear polarization degree and long polarization time are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of dynamic nuclear polarization devices, and particularly to a molten DNP cross-polarization probe. Background Art

[0002] Applying cross-polarization technology to improve the sensitivity of a probe for detecting target nuclei is a technical means that can be adopted in the dynamic nuclear polarization method (DNP). Specifically, a DNP cross-polarization probe utilizes the principle of electron-proton-target nucleus triple resonance to achieve the transfer of electron polarization to protons and then to target nuclei, thereby increasing the polarization degree of the target nuclei and shortening the polarization establishment time. Among them, the realization of electron-proton-target nucleus triple resonance requires the use of basic components of a microwave resonator and a radio frequency double-resonant circuit. On this basis, in order to adapt to different application scenarios, the DNP cross-polarization probe also has different structural designs.

[0003] At the same time, dissolution dynamic nuclear polarization (dDNP) is a method for further improving the detection sensitivity by applying the DNP principle. Different from the conventional DNP method, dDNP needs to polarize a frozen solid microbead sample under ultra-low temperature (<2K) and strong magnetic field (3-7T). After the sample is polarized, a high-temperature and high-pressure solvent is injected into the sample area to melt it to obtain a target test solution with a high polarization degree.

[0004] Applying cross-polarization technology in dDNP can increase the polarization degree of the detected nuclei, shorten the polarization time, and significantly reduce the consumption of liquid helium in a single experiment. However, conventional DNP cross-polarization probes cannot meet the experimental requirements of dDNP: a resonator suitable for high-frequency microwave in a strong magnetic field; a double-resonant circuit that can provide a high radio frequency field in an ultra-low temperature environment; a spatial structure compatible with a melting device, etc. For the above reasons, for the realization of the application of cross-polarization technology in molten DNP, the design of the molten DNP cross-polarization probe is particularly important. Summary of the Invention

[0005] In view of the above problems, the present invention provides a molten DNP cross-polarization probe. The technical solution of the present invention for solving the above technical problems is as follows:

[0006] A molten DNP cross-polarization probe, which includes a resonator, an intracavity component, a flange, a double-resonant circuit, and a radio frequency rod;

[0007] The resonator is a hollow cylindrical structure with an open upper part;

[0008] The intracavity component is disposed inside the resonant cavity. The intracavity component includes a coil unit disposed in the middle of the resonant cavity and a mirror unit disposed outside the coil unit.

[0009] The flange is buckled to the upper end of the resonant cavity. A first through hole is formed in the middle of the flange, and a second through hole is formed outside the first through hole.

[0010] The double resonant circuit is disposed on the upper end of the flange.

[0011] The RF rod passes through the second through hole and is connected to the coil unit inside the resonant cavity.

[0012] Compared with the prior art, the technical solution of the present application has the following beneficial technical effects:

[0013] The melting DNP cross-polarization probe provided by the present application, through the design of the resonant cavity, ensures the transmission and focusing of microwave energy in the required frequency band during the dDNP experiment, ensures that the microwave is effectively transmitted to the sample area, saturates the electron EPR transition, so as to realize the subsequent efficient electron-proton polarization transfer; with the cooperation of the double resonant circuit and related structures, a high RF field is provided to realize the cross-polarization of protons and target nuclei, and at the same time effectively avoid the problems of discharge and breakdown of the RF circuit at ultra-low temperature; by using the design of the overall mechanical structure of the probe, the special requirements of the melting link of the dDNP experiment are met; finally, the application of the cross-polarization technical means in melting DNP is successfully realized, and the technical problems of low nuclear polarization degree and long polarization time in detection are solved.

[0014] On the basis of the above technical solution, the present invention can be further improved as follows.

[0015] Further, the coil unit includes a coil and a fixing member. The lower end surface of the fixing member is limited and fixed to the inner bottom surface of the resonant cavity, and the coil is fixed outside the fixing member.

[0016] Further, an annular groove is formed on the inner bottom surface of the resonant cavity, and an annular protrusion matching with the annular groove is formed at the lower end of the fixing member.

[0017] The design of the annular protrusion and the annular groove can isolate the resonant cavity and the coil to prevent the two from being short-circuited.

[0018] Further, the fixing member includes a hollow cylinder and a disc. The disc is located outside the hollow cylinder and is disposed near the lower end of the hollow cylinder. The coil is disposed outside the hollow cylinder, and the upper end of the hollow cylinder is fixed to the bottom of the flange.

[0019] Further, the coil is a single-layer radio frequency coil, and the coil applies a Hartmann-Hahn matching condition pulse sequence to achieve polarization transfer from highly polarized protons to the target nucleus.

[0020] Further, a boss is formed at the lower end of the flange, and the inner shape of the opening of the resonant cavity is adapted to the outer contour of the boss.

[0021] Further, the mirror unit includes an upper thin sheet and a microwave mirror. The upper end of the upper thin sheet is limited and fixed by the boss and the resonant cavity. The microwave mirror faces the gap of the coil and acts on the sample area at the center of the hollow cylinder.

[0022] Through the coil structure setting, cooperating with the microwave mirror, the irradiation efficiency of the microwave on the sample is improved, the focusing effect of the microwave magnetic field in the sample is enhanced, the intensity of the microwave magnetic field in the sample area is increased, the Q value of the resonant cavity is increased, the polarization degree of the sample is increased, and the polarization time is further shortened.

[0023] Further, a grounding plate is vertically arranged at the upper end of the flange. The grounding plate is a conductor and is arranged close to the outer side of the flange. The double-resonant circuit is arranged on the inner side wall of the grounding plate.

[0024] Further, the outer arc of the grounding plate is consistent with the outer wall arc of the resonant cavity, and the lower end of the grounding plate is in close contact with the resonant cavity.

[0025] The grounding plate provides a stable grounding loop for the radio frequency double-resonant circuit.

[0026] Further, a third through hole for fixing the microwave waveguide is formed on the flange, so that the microwave is fed into the resonant cavity along the third through hole, and the number of the third through holes is two.

[0027] The radio frequency rod passes through the first through hole and is connected to the coil in the resonant cavity. The setting of the two third through holes can meet the requirements of single-end input and double-end input. Description of the Drawings

[0028] Figure 1 It is a schematic structural diagram of a molten DNP cross-polarization probe provided by an embodiment of the present invention;

[0029] Figure 2 It is an external structural diagram of the resonant cavity in the embodiment of the present invention;

[0030] Figure 3 It is an internal structural diagram of the resonant cavity in the embodiment of the present invention;

[0031] Figure 4 It is a schematic structural diagram of the components in the cavity in the embodiment of the present invention;

[0032] Figure 5 Schematic diagram of the fixing part in the cavity component in the embodiment of the present invention

[0033] Figure 6 Schematic diagram of the connection structure between the flange and the double-resonant circuit in the embodiment of the present invention;

[0034] Figure 7 is Figure 5 Another perspective schematic diagram;

[0035] Figure 8 Schematic diagram of the circuit of the double-resonant circuit in the embodiment of the present invention;

[0036] Figure 9 Schematic diagram of the usage state in the embodiment of the present invention. Detailed implementation manners

[0037] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0038] As Figures 1-4 shown, the present application discloses a molten DNP cross-polarization probe, which includes a resonant cavity 10, a cavity component 20, a flange 30, a double-resonant circuit 40, and a radio frequency rod 50.

[0039] Among them, as shown in combination with Figure 2 and Figure 3 , the resonant cavity 10 is a hollow cylindrical structure with an open upper part; a screw hole is left at the upper part of the resonant cavity 10 for fixing with the upper flange 30.

[0040] In the embodiment of the present application, a cylinder 101 extending outward is formed on the bottom end surface of the resonant cavity 10, and a threaded hole is formed inside the cylinder 101 for fixing the lower end of the resonant cavity 10. Specifically, a limiting plastic plate can be connected to the bottom of the resonant cavity with screws later; preferably, the resonant cavity 10 is made of red copper to ensure a certain wall thickness, and the surface is gold-plated to be suitable for the ultra-low temperature environment during the molten DNP experiment.

[0041] As shown in combination with Figure 4 , the cavity component 20 is arranged inside the resonant cavity 10, and the cavity component 20 includes a coil unit 11 arranged in the middle of the resonant cavity 10 and a mirror unit 12 arranged outside the coil unit 11.

[0042] Specifically, the coil unit 11 includes a coil Ls and a fixing member 112. The lower end surface of the fixing member 112 is limited and fixed to the inner bottom surface of the resonant cavity 10, and the coil Ls is fixed outside the fixing member 112.

[0043] In an alternative embodiment of the present application, the inner bottom surface of the resonant cavity 10 has a limiting structure that cooperates with the lower end surface of the fixing member 112, which can isolate the resonant cavity and the coil Ls to prevent short - circuiting between the two.

[0044] For example, in some embodiments, an annular groove 10a is formed on the inner bottom surface of the resonant cavity 10, and an annular protrusion 1123 that cooperates with the annular groove 10a is formed at the lower end of the fixing member 112. In other embodiments, it can also be in the form that a protrusion is formed on the inner bottom surface of the resonant cavity 10 and a groove is formed at the lower end of the fixing member 112. Moreover, the groove and the protrusion are not limited to being annular, and can also be any other optional shapes, such as square or triangular.

[0045] The coil Ls is a single - layer radio - frequency coil. Different types of coils can be used according to actual usage requirements, and its appearance is a hollow cylindrical column.

[0046] For a conventional NMR detection radio - frequency coil, its main functions are to excite the target nuclear spin and receive nuclear magnetic resonance signals. Specifically, the coil acts as an excitation coil in combination with a single - port single - resonant circuit to generate a radio - frequency field perpendicular to the main magnetic field to excite the target nucleus, and then acts as a receiving coil to capture the change in the magnetization vector during the nuclear spin relaxation process.

[0047] The coil Ls in this design is a radio - frequency coil that undertakes the cross - polarization function, which is different from the above - mentioned conventional NMR coil. In the CP experiment, the radio - frequency coil is connected to a specially designed single - port / double - port radio - frequency double - resonant circuit to achieve the excitation of two resonance - frequency radio - frequency fields corresponding to protons and target nuclei. Specifically, during the experiment, the coil applies the Hartmann - Hahn matching condition pulse sequence to achieve the polarization transfer from highly polarized protons to target nuclei.

[0048] The formula expression of the Hartmann - Hahn matching condition is:

[0049] γ I B 1I =γ S B 1S

[0050] Among them, γ I and γ S are the gyromagnetic ratios of two different nuclei (such as 1 H and 13 C); B 1I and B 1SThey are the intensities of the radio frequency fields applied to these two nuclei respectively.

[0051] It describes the condition for the spin lock frequencies of two different nuclei (such as 1 H and 13 C) to match through a radio frequency field in a cross-polarization experiment. To achieve polarization transfer, the ratio of the radio frequency field frequencies of the two nuclei must be equal to the ratio of their gyromagnetic ratios, that is, the spin lock frequencies match. This matching condition can effectively transfer polarization from a nucleus with high abundance and high sensitivity (such as 1 H) to a nucleus with low abundance and low sensitivity (such as 13 C), thereby enhancing the signal of the low-sensitivity nucleus.

[0052] Since the coil Ls needs to be ensured to be at the center of the internal sample tube to obtain better detection effects and avoid contact with the resonator 10, the fixing member 112 needs to use an insulating material as the coil Ls fixing device.

[0053] Among them, as shown in Figure 5 , the fixing member 112 includes a hollow cylinder 1121 and a disc 1122. The disc 1122 is located outside the hollow cylinder 1121 and is arranged near the lower end of the hollow cylinder 1121. The coil Ls is arranged outside the hollow cylinder 1121, and the upper end of the hollow cylinder 1121 is fixed to the bottom of the flange 30.

[0054] That is, the upper and lower ends of the hollow cylinder 1121 are respectively clamped between the lower end of the flange 30 and the bottom of the resonator 10.

[0055] As a preferred embodiment, the coil Ls is a saddle-shaped coil, and the material is copper-plated with gold. The shape of this coil is similar to a saddle-shaped bend, and the inner diameter conforms to the outer diameter of the coil fixing column. Chamfers are made at the corners of each part to reduce radio frequency loss. In specific implementation, a capacitor is directly connected in parallel at both ends of the coil to perform the function of the proximal tuning capacitor.

[0056] As shown in Figure 1 , Figure 6 and Figure 7 , the flange 30 is buckled on the upper end of the resonator 10 to play the role of fixing the resonator 10 and other components of the probe.

[0057] Preferably, a boss 31 is formed at the lower end of the flange 30, and the shape of the inner side of the opening of the resonator 10 is adapted to the outer contour of the boss 31.

[0058] A first through hole 30a is formed in the middle of the flange 30. Considering that this design needs to be used in the experiment of melting DNP, the first through hole 30a is used for inserting the melting rod.

[0059] The flange 30 is provided with second through holes 30b for two radio frequency rods. The radio frequency rods 50 pass through the second through holes 30b and are connected to the coil Ls in the resonant cavity 10, which can meet the requirements of single-ended input and double-ended input.

[0060] The flange 30 is provided with third through holes 30c for fixing the microwave waveguide, and the microwave is fed into the resonant cavity 10 along the third through holes 30c.

[0061] The double-resonant circuit 40 is arranged at the upper end of the flange 30. The double-resonant circuit 40 needs to be placed close to the resonant cavity to reduce the loss of the high-frequency circuit. At the same time, it also needs to be stably grounded to ensure the stability of the circuit. Therefore, a fixed position for the ground plate 60 is also reserved on the flange 30.

[0062] The ground plate 60 is a conductor structure, preferably a good conductor, which is used to provide a stable grounding circuit for the double-resonant loop 40. Preferably, the bottom layer of the circuit board of the double-resonant circuit 40 is copper-plated and is in close contact with the platform of the ground plate 60 through screws to provide a stable grounding point for the circuit.

[0063] Preferably, both the flange 30 and the ground plate 60 are made of copper-plated with gold, which is suitable for the ultra-low temperature environment of the molten DNP experiment and can also meet the non-magnetic requirements of the NMR experiment.

[0064] Considering that this design needs to be used in the experiment of molten DNP, the ground plate also needs to take into account the experimental requirements of molten DNP. Specifically, on the one hand, since the entire polarization process of molten DNP needs to be completed at ultra-low temperature, a cryostat needs to be used, which limits the maximum outer diameter of the probe. At the same time, it is necessary to reduce the sharp protruding part of the probe to avoid scratching the inner wall of the cryostat when the probe is inserted into and removed from the cryostat.

[0065] Secondly, for the molten DNP experiment, after polarization is completed, a melting rod needs to be inserted vertically from top to bottom in the center of the probe to achieve the melting process. Therefore, enough space is required around the axis of the probe for subsequent rod insertion. So the design of the ground plate 60 needs to consider the space utilization rate. Therefore, the ground plate 60 has two platforms with a herringbone design inside, which are embedded in a tile-like shape on the side close to the flange 30. Preferably, the outer arc of the ground plate 60 is consistent with the outer wall arc of the resonant cavity 10, and the lower end is in close contact with the resonant cavity 10.

[0066] This design can save space to a great extent. The ground plate 60 can be installed with the dual resonant circuit required for specific tests according to experimental needs. Specifically, electrical components can be soldered on the ground plate 60 to form the resonant circuit required in a specific experiment. For specific cross-polarization experiments, what is needed is a dual resonant circuit that can provide the resonant frequency corresponding to protons and the resonant frequency of the target nucleus. According to experience, the work of soldering electrical components for tuning is very time-consuming and cumbersome. Therefore, in this design, the platform of the ground plate 60 is equipped with a circuit board fixture. In the experiment, you can also choose to directly install the packaged circuit board instead of the traditional probe soldering component process, which can also simplify the experimental operation load.

[0067] Among them, the reflector unit 12 includes an upper thin sheet 121 and a microwave reflector 122. The upper end of the upper thin sheet 121 is fixed by the boss 31 and the resonant cavity 10. The microwave reflector 122 is facing the gap of the coil Ls and acts on the sample area in the center of the hollow cylinder. In order to ensure the fixation of the microwave reflector 122, a through-hole threaded hole is left in the middle of the inner wall of the resonant cavity 10 for the installation and fixation of the reflector.

[0068] Upper sheet 121 secures and coordinates with resonant cavity 10 and flange 30 to limit position. The tilted surface of microwave reflector 122 reflects microwaves introduced by the waveguide. It's important to note that during the experiment, the sample tube / cup containing the sample must be placed in the exact center of coil Ls. Therefore, the interior of the support also secures the sample, ensuring it remains stationary and centered during polarization and subsequent processes.

[0069] By setting the coil Ls and cooperating with the microwave reflector 122, the efficiency of microwave irradiation on the sample is improved, the focusing effect of the microwave magnetic field on the sample is enhanced, the intensity of the microwave magnetic field in the sample area is increased, the Q value of the resonant cavity is increased, the polarization degree of the sample is increased, and the polarization time is further shortened.

[0070] This example adopts a double-ended input double-resonance circuit, with two platforms connected to the ground plate 60. 1 H / 13 C dual-resonance circuit board. While achieving dual resonance, the design of the isolation circuit avoids mutual interference between the two frequencies.

[0071] Among them, the ports of the two circuit boards close to the resonant cavity are respectively connected with radio frequency rods passing through the flange 30 and connected to the two ends of the saddle coil Ls in the resonant cavity; at the same time, the upper ends of the two circuit boards are respectively connected with radio frequency rods and 1 H / 13 At the same time, the upper part of the grounding plate 60 is fitted with a circular fixing plate and fixedly connected through screw holes on the side of the supporting plate to ensure the stability of the entire device.

[0072] As an alternative embodiment, the dual-resonant circuit of the present application is as shown in Figure 8 In this circuit, a dual-resonant loop is formed by two inductors (L2, Ls) and corresponding capacitors.

[0073] In the embodiment of the present application, this dual-resonant circuit is a heterodox dual-resonant circuit, which can achieve resonance at two frequency points (for the 5T polarization system in the embodiment and 1 H / 13 C nuclei, the dual-resonance frequencies are 211.7 MHz and 53.4 MHz respectively): Ports 1 and 2 in the figure are two RF input terminals, providing RF signals of 211.7 MHz and 53.4 MHz; in this embodiment, the components that appear from Port 1 to the left end of coil Ls are fixed on an inner plane of the ground plane 60 using a PCB board (hereinafter referred to as the left-end circuit). Similarly, the components that appear from Port 2 to the right end of coil Ls are fixed on another inner plane of the ground plane 60 using a PCB board (hereinafter referred to as the right-end circuit); the coil Ls at the center position in the figure is the above-mentioned saddle-shaped RF coil, which can be equivalently regarded as an inductor in the circuit. A proximal tuning capacitor, i.e., capacitor C9, is connected in parallel with the saddle-shaped coil, sharing part of the resonant function at the proximal end (the proximal end is near the sample), thereby reducing the power loss caused by the transmission line; capacitor C9, capacitor C5 in the left-end circuit, and capacitor C7 in the right-end circuit together with coil Ls form a resonant loop, which can generate 1 The resonance at the resonance frequency of 211.7 MHz of H. The series-connected capacitor C3 in the left-end circuit functions as a matching capacitor in this loop, adjusting the impedance matching at the 1 H frequency point; capacitor C9, capacitor C6 in the right-end circuit, and coil Ls form a resonant loop, which can generate 13 The resonance at the resonance frequency of 53.4 MHz of C. The series-connected capacitor C4 in the right-end circuit functions as a matching capacitor in this loop, adjusting the impedance matching at the 13 C frequency point; the left-end inductor L3 and capacitor C2 are connected in series to form a first notch filter loop, which resonates at the 13 Resonance frequency of 53.4 MHz of C, allowing the 13 Resonance frequency of C to pass through; correspondingly, the right-side inductor L2 and capacitor C1 are connected in parallel to form a second notch filter loop, which resonates at the 1 Resonance frequency of 211.7 MHz of H, allowing the 1 Resonance frequency of H to pass through while blocking the 13 C frequency from passing through; with the cooperation of the two notch filter loops, signal interference is avoided and the stability of signal transmission is ensured. The dual resonance is achieved by the cooperation of the above circuit elements.

[0074] It is understandable that the double-resonant circuit itself is a common technical means. Therefore, those skilled in the art can design a double-resonant circuit different from the above embodiments according to the design concept of this application. Therefore, this application does not limit the specific structure of the double-resonant circuit. However, as long as the design concept of using the resonant cavity and the double-resonant circuit to jointly achieve cross polarization is consistent with this application, it should fall within the protection scope of this application.

[0075] Combined with Figure 9 As shown, when the molten DNP cross-polarization probe provided by this application is used, the resonant cavity 10 is placed in the cavity of the cryostat 90. The cryostat 90 is placed in the polarization magnet, and the polarization magnet provides the main magnetic field, while the cryostat provides the ultra-low temperature environment required for the molten DNP experiment. The probe is externally connected to a microwave source 100 to generate microwaves, and the microwaves are introduced into the resonant cavity along the waveguide and concentrated in the sample area at the center of the coil under the focusing of the reflector. Under the combined action of the main magnetic field and the microwaves, the sample realizes electron paramagnetic resonance and the transfer of electron polarization to protons, thereby realizing the hyperpolarization of protons. The probe is externally connected to a radio frequency source 200 to provide the required frequency signal for the double-resonant circuit, thereby driving the double-resonant circuit to resonate at the frequency points of protons and target nuclei, realizing the cross polarization of protons and target nuclei, and thereby realizing the hyperpolarization of the target nuclei.

[0076] The molten DNP experiment relies on a high-intensity radio frequency field to achieve the excitation of nuclear spins. The embodiment of this application adopts a low-loss proximal resonant circuit design. The double-resonant circuit is placed on the resonant cavity flange 30 close to the coil Ls by using a ground plane 60, reducing cable loss and meeting the requirement for a high radio frequency field strength with high efficiency. At the same time, the low-pressure gaseous helium environment in the experiment easily causes the discharge and breakdown of the radio frequency circuit. In this design, the proximal resonant circuit is realized as close as possible to the detection coil, thereby reducing the voltage amplitude of the resonant circuit and effectively avoiding the discharge and breakdown phenomena of the radio frequency circuit. In addition, the design of the ground plane 60 provides a stable ground point for the overall circuit, further reducing circuit loss and ensuring the realization of a high radio frequency field.

[0077] In addition, the realization of double resonance of protons with low gyromagnetic ratio nuclei at low temperature requires a stable double-resonant circuit. Combined with the above, the double-resonant circuit in this embodiment includes a plurality of capacitors and inductance elements. Due to the limitation of the ultra-low temperature experimental conditions in this case, the position of the double-resonant circuit is limited near the resonant cavity 10. Therefore, in this case, a herringbone tile-shaped ground plane 60 is designed to increase the space utilization rate near the resonant cavity 10.

[0078] In summary, the molten DNP cross-polarization probe provided by this application ensures the transmission and focusing of microwave energy during the dynamic polarization experiment through the design of the resonant cavity, realizes the control of the microwave mode and the selection of the reflection path, and ensures that the microwave energy can be effectively transmitted to the sample area during the experiment, acting on the electrons in the free radicals to cause the saturated electron EPR transition, so as to realize the subsequent efficient electron-nuclear polarization transfer; then, under the action of the double-resonant circuit and the coil, the cross-polarization of electrons-protons-target nuclei is realized, the polarization degree is improved, and the polarization time is shortened; at the same time, through the cross-polarization method, it is possible to select a sample to be polarized in which the target nucleus does not directly contact the free electrons. Therefore, it is possible to avoid the influence of the electron paramagnetic environment on the hyperpolarized solution obtained after melting, thereby extending the polarization retention time of the sample and meeting the requirements of long-distance inspection.

[0079] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A molten DNP cross-polarization probe, characterized in that, It includes a resonant cavity, an internal component in the cavity, a flange, a double-resonant circuit, and a radio-frequency rod; The resonant cavity is a hollow cylindrical structure with an open upper part; The internal component in the cavity is arranged inside the resonant cavity. The internal component in the cavity includes a coil unit arranged in the middle of the resonant cavity and a mirror unit arranged outside the coil unit; The flange is buckled on the upper end of the resonant cavity. A first through-hole is formed in the middle of the flange, and a second through-hole is formed outside the first through-hole; The double-resonant circuit is arranged on the upper end of the flange; The radio-frequency rod passes through the second through-hole and is connected to the coil unit inside the resonant cavity.

2. The molten DNP cross-polarization probe according to claim 1, characterized in that, The coil unit includes a coil and a fixing member. The lower end surface of the fixing member is limited and fixed to the inner bottom surface of the resonant cavity, and the coil is fixed outside the fixing member.

3. The molten DNP cross-polarization probe according to claim 2, characterized in that, An annular groove is formed on the inner bottom surface of the resonant cavity, and an annular protrusion matching the annular groove is formed at the lower end of the fixing member.

4. The molten DNP cross-polarization probe according to claim 3, characterized in that, The fixing member includes a hollow cylinder and a disc. The disc is located outside the hollow cylinder and is arranged close to the lower end of the hollow cylinder. The coil is arranged outside the hollow cylinder, and the upper end of the hollow cylinder is fixed to the bottom of the flange.

5. The molten DNP cross-polarization probe according to claim 4, characterized in that, The coil is a single-layer radio-frequency coil, and the coil applies the Hartmann-Hahn matching condition pulse sequence to realize the polarization transfer from highly polarized protons to the target nucleus.

6. The molten DNP cross-polarization probe according to claim 4, wherein A boss is formed at the lower end of the flange, and the shape of the inner side of the opening of the resonant cavity is adapted to the outer contour of the boss.

7. The molten DNP cross-polarization probe according to claim 6, characterized in that, The mirror unit includes an upper thin sheet and a mirror. The upper end of the upper thin sheet is limited and fixed by the boss and the resonant cavity. The mirror faces the gap of the coil and acts on the sample area at the center of the hollow cylinder.

8. The molten DNP cross-polarization probe according to claim 1, characterized in that, A grounding plate is vertically arranged on the upper end of the flange. The grounding plate is a conductor and is arranged close to the outside of the flange. The double-resonant circuit is arranged on the inner side wall of the grounding plate.

9. The molten DNP cross-polarization probe according to claim 8, characterized in that, The outer arc of the grounding plate is consistent with the outer arc of the resonant cavity, and the lower end of the grounding plate is in close contact with the resonant cavity.

10. The molten DNP cross-polarization probe according to claim 1, characterized in that, Two third through-holes for fixing a microwave waveguide are formed on the flange, so that microwaves are fed into the resonant cavity along the third through-holes.

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