An ultra-low temperature electron paramagnetic resonance probe and its Q-switching mechanism

Abstract

The present invention discloses an ultra-low temperature electron paramagnetic resonance probe and a Q-switching mechanism thereof, wherein the ultra-low temperature electron paramagnetic resonance probe comprises a cavity guide structure fixed in a dewar flask through a hollow pipe extending from the top of the dewar flask, a cavity shell with a grating structure arranged in the cavity guide structure, an annular sapphire crystal arranged in the cavity shell, and a coil fixed on the shell of the cavity guide structure, wherein the cavity guide structure is relatively fixed to the bottom of the hollow pipe, and a microwave signal cable extending from the top of the dewar flask is fixedly connected to the back wall of the cavity shell, and the microwave signal cable drives the cavity shell to move up and down relative to the cavity guide structure under the control of a precision lifting mechanism arranged outside the dewar flask, so as to adjust the Q value of the resonant cavity. The present invention only needs to fine-tune the resonant cavity structure, and a precision lifting mechanism is arranged outside the dewar flask, which is not only easy to implement, but also easy to operate.

Description

Technical Field

[0001] The invention relates to the technical field of electron paramagnetic resonance, in particular to an ultra-low temperature electron paramagnetic resonance probe and a Q-switching mechanism thereof. Background Art

[0002] Electron paramagnetic resonance (EPR) is a magnetic resonance technique originated from the magnetic moment of unpaired electrons. It can be used to detect the unpaired electrons contained in atoms or molecules of substances from qualitative and quantitative aspects and explore the structural characteristics of their surrounding environment.

[0003] The resonant cavity is the core component of the EPR device. In the continuous wave EPR experiment, we hope that the resonant cavity has a higher Q value, so that the system test sensitivity is higher and the low signal detection capability is stronger; in the pulsed EPR experiment, we hope that the resonant cavity has a lower Q value, because the higher the Q value, the longer the dead time, and the more easily the echo signal is interfered by the input signal. However, the Q value is low when over-coupled. If a higher microwave magnetic field is needed to increase the signal strength, the resonant cavity needs to have a higher filling factor. The dielectric cavity is one of the many resonant cavities with the characteristics of a high filling factor. If a special coupling structure is used, it can be tuned to a high Q value, and it can also be tuned to a low Q value in the over-coupled state, which can meet the above requirements.

[0004] The Q value of the dielectric resonant cavity reflects the energy consumption of electromagnetic waves. The larger the Q value, the higher the signal peak. When using an electron paramagnetic resonance spectrometer to perform EPR testing on samples, the stability of the Q value should be ensured, otherwise the concentration of free radicals in the sample cannot be accurately reflected. Under normal circumstances, Q-switching can be achieved by setting a tuning screw and adjusting the insertion depth of the tuning screw. For example, the invention patent application CN 110658226 A published on January 7, 2020 discloses such a Q-switching mechanism.

[0005] However, the ultra-low temperature environment required by the ultra-low temperature electron paramagnetic resonance spectrometer is created by placing the dielectric resonant cavity through a long tube into a liquid nitrogen / liquid helium Dewar flask, which brings inconvenience to the Q value adjustment of the dielectric resonant cavity. Summary of the invention

[0006] In view of the above problems, the present invention provides an ultra-low temperature electron paramagnetic resonance probe and a Q-switching mechanism thereof, which can conveniently and quickly adjust the Q value of the resonant cavity in a Dewar flask.

[0007] The present invention protects an ultra-low temperature electron paramagnetic resonance probe, comprising a cavity guide structure fixed in a Dewar flask through a hollow pipe extending from the top of the Dewar flask, a cavity shell with a grating structure arranged in the cavity guide structure, an annular sapphire crystal arranged in the cavity shell, and a coil fixed on the cavity guide structure, wherein the annular sapphire crystal is relatively fixed to the bottom of the hollow pipe, a microwave signal cable extending from the top of the Dewar flask is fixedly connected to the back wall of the cavity shell, and the microwave signal cable drives the cavity shell to move up and down relative to the annular sapphire crystal under the control of a precision lifting mechanism arranged outside the Dewar flask, so as to achieve the Q value adjustment of the resonance cavity.

[0008] Furthermore, an elastic supporting member is provided at the bottom of the cavity shell, which is used to ensure that the annular sapphire crystal always abuts against the hollow tube during the upward and downward movement of the cavity shell.

[0009] Furthermore, the elastic supporting member is a non-magnetic compression spring; an upper limit member is provided at the top of the annular sapphire crystal, a lower limit member is provided at the bottom, and a compression spring fixing member is provided at the bottom of the lower limit member; the top of the non-magnetic compression spring is sleeved on the compression spring fixing member, and the bottom is tightened by a hand-tightened nut that is detachably fixed to the bottom of the cavity shell.

[0010] Furthermore, a cable guide groove is provided on one side of the cavity shell for introducing the microwave signal cable vertically extending into the Dewar flask therein, and a fixed cover plate is threadedly connected to the outer side of the cable guide groove.

[0011] Furthermore, the cavity guide structure has a winding groove made of non-metallic material detachably fixed on the cavity wall on both sides of the cavity shell, and a coil baffle made of non-metallic material is provided outside the winding groove.

[0012] The present invention also protects the Q-switching mechanism of the ultra-low temperature electron paramagnetic resonance probe, and the Q-switching operation is achieved by the precision lifting mechanism driving the microwave signal cable and the cavity housing to move up and down relative to the annular sapphire crystal.

[0013] The precision lifting mechanism includes a clamping part fixed on the microwave signal cable, a fixing part and an adjusting part arranged on both sides of the clamping part, and an adjusting support rod passing through the fixing part, the clamping part and the adjusting part; the adjusting support rod is hinged with the fixing part, the clamping part and the adjusting part, and when the adjusting part is moved up and down, the adjusting support rod rotates around the hinge axis with the fixing part, thereby driving the clamping part to move up and down, thereby realizing the lifting and lowering action of the microwave signal cable.

[0014] Furthermore, the fixing member and the adjusting member are fixed on a sealing seat at the top of the Dewar flask.

[0015] Furthermore, the adjusting member is moved up and down by a threaded lifting mechanism; specifically, the adjusting member is mainly composed of an internal threaded pin fixed to one side of the sealing seat, an adjusting screw passing through the internal threaded pin, and an adjusting support rod hinge seat arranged on the top of the adjusting screw; preferably, a hand-tightened turntable is provided on the fixing sleeve of the adjusting screw.

[0016] The present invention controls the lifting and lowering of a microwave signal cable originally used to access microwave signals, thereby driving a cavity shell fixed thereto to move up and down, thereby forming a relative movement with the annular sapphire crystal and realizing the Q value adjustment of the resonant cavity. It is only necessary to fine-tune the resonant cavity structure and to set a precise lifting mechanism outside the Dewar flask, which is not only easy to implement but also easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the overall structure of the ultra-low temperature electron paramagnetic resonance probe;

[0018] Figure 2 This is a schematic diagram of the explosion of the resonant cavity;

[0019] Figure 3 This is a schematic diagram of the installation position of the ring-shaped sapphire crystal;

[0020] Figure 4 It is a schematic diagram of the winding slot;

[0021] Figure 5 It is a schematic diagram of the structure of the precision lifting mechanism. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention are provided for the purpose of illustration and description, and are not intended to be exhaustive or to limit the present invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention, and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

[0023] Example 1

[0024] An ultra-low temperature electron paramagnetic resonance probe, such as Figure 1 , Figure 2 As shown, it includes a cavity guide structure 2 fixed in the Dewar flask through a hollow pipe 1 extending from the top of the Dewar flask, a cavity shell 3 with a grating structure arranged in the cavity guide structure, a ring-shaped sapphire crystal 4 arranged in the cavity shell, and a coil fixed on the cavity guide structure. The Dewar flask mentioned in this application refers to a liquid nitrogen / liquid helium Dewar flask.

[0025] In the prior art, the Q value of the resonant cavity is usually adjusted by controlling the coupling degree. For example, the invention patent application CN 110658226 A mentioned in the background technology adjusts the coupling degree by adjusting the insertion depth of the tuning screw. Since it is not convenient to adjust the Q value by a structure similar to a tuning screw in the Dewar flask, the present application creatively realizes the Q value adjustment by inserting a microwave signal cable from the outside of the Dewar flask. The specific implementation structure is as follows.

[0026] The annular sapphire crystal 4 is relatively fixed to the bottom of the hollow tube 1, and the back wall of the cavity shell 3 is fixedly connected with a microwave signal cable 5 extending from the top of the Dewar flask. The microwave signal cable 5 is controlled by a precision lifting mechanism arranged outside the Dewar flask to drive the cavity shell 3 to move up and down relative to the annular sapphire crystal 4, thereby realizing the tuning of the coupling degree and further realizing the Q value adjustment of the resonant cavity.

[0027] The microwave signal cable was originally used to access microwave signals (X-band). This application controls the lifting of the cable to drive the fixed cavity shell to move up and down, forming a relative movement with the annular sapphire crystal to achieve the Q value adjustment of the resonant cavity. This implementation method only requires fine-tuning the resonant cavity structure and setting a precision lifting mechanism outside the Dewar flask. It is not only easy to implement, but also easy to operate.

[0028] In order to ensure that the position of the annular sapphire crystal is relatively fixed, an elastic supporting member is provided at the bottom of the cavity shell 3 to ensure that the annular sapphire crystal 4 is always against the hollow tube 1 during the up and down movement of the cavity shell 3.

[0029] Specifically, in this embodiment, the elastic supporting member is a non-magnetic compression spring 6; the annular sapphire crystal 4 is provided with an upper limiter 7 at the top and a lower limiter 8 at the bottom, and the bottom of the lower limiter 8 is provided with a compression spring fixing member 9. The upper and lower limiters here are the same as the annular sapphire crystal, and the interior is hollow for the sample to be tested to be placed; the top of the non-magnetic compression spring 6 is sleeved on the compression spring fixing member 9, and the bottom is tightened by a hand-tightened nut 10 that is detachably fixed to the bottom of the cavity shell, as shown in FIG. Figure 3 As shown (without magnetic compression spring Figure 3 The whole structure is easy to install and disassemble. When installing, after the annular sapphire crystal and its upper and lower limiters are assembled, it is inserted from the bottom of the cavity shell, and then the non-magnetic compression spring is inserted, and finally the hand-tightening nut is screwed on; disassembly is the opposite.

[0030] In order to ensure the stability of the microwave signal cable and the cavity shell and prevent it from loosening, a cable guide groove 11 is provided on one side of the cavity shell 3 for introducing the microwave signal cable 5 vertically extending into the Dewar flask, and a fixed cover plate 12 is threadedly connected to the outer side of the cable guide groove 11. After the microwave signal cable is completed, the empty gap in the cable guide groove can be filled with glue.

[0031] In order to save space, the cavity guide structure 2 corresponds to the cavity wall on both sides of the cavity shell and is detachably fixed with a winding groove 13 made of non-metallic material, such as Figure 4 As shown, the coil baffle 14 made of non-metallic material is provided outside the winding groove 14. Compared with the coil setting method in the prior art, this structure greatly saves the resonant cavity space. The non-metallic material can be Teflon. The electrical signal for energizing the coil is connected from the sealing seat 19, referring to Figure 1 The sealing seat 19 is provided with two electrode line interfaces, the electrode line 21 ( Figure 1 Only one electrode is shown in the figure) passes through the bottom of the sealing seat 19 and extends to the top of the cavity guide structure 2 to connect with one end of the coil. The cavity guide structure is provided with a through hole for the coil to pass through, which plays a role in stabilizing the coil / electrode wire. A clamp for clamping the sample to be tested is provided inside the hollow tube body. During the test, the sample is vertically inserted into the annular sapphire crystal.

[0032] Example 2

[0033] A Q-switching mechanism for an ultra-low temperature electron paramagnetic resonance probe, such as Figure 5 As shown, the microwave signal cable 5 and the cavity housing 3 are driven by the precision lifting mechanism to move up and down relative to the annular sapphire crystal 4.

[0034] The precision lifting mechanism includes a clamping member 15 fixed on the microwave signal cable, a fixing member 16 and an adjusting member 17 arranged on both sides of the clamping member, and an adjusting support rod 18 penetrating the fixing member 16, the clamping member 15 and the adjusting member 17; the adjusting support rod 18 is hinged with the fixing member 16, the clamping member 15 and the adjusting member 17, and when the adjusting member 17 is moved up and down, the adjusting support rod 18 rotates around the hinge axis with the fixing member 16, thereby driving the clamping member 15 to move up and down, thereby realizing the lifting and lowering action of the microwave signal cable 5. The fixing member 16 and the adjusting member 17 are fixed on the sealing seat 19 at the top of the Dewar flask. This lifting mechanism is arranged outside the Dewar flask to realize the Q value adjustment of the resonant cavity inside the Dewar flask, and has strong stability, convenient operation and easy implementation.

[0035] To ensure the accuracy of Q value adjustment, the adjusting member 17 is moved up and down by a threaded lifting mechanism. Specifically, in this embodiment, the adjusting member 17 is mainly composed of an internal thread pin 1701 fixed to one side of the sealing seat, an adjusting screw 1702 penetrating the internal thread pin, and an adjusting support rod hinge seat 1703 arranged at the top of the adjusting screw. The more precise the threads of the adjusting screw and the internal thread pin, the higher the Q value adjustment accuracy. In order to make the adjustment more convenient, a hand-tightening dial 1704 is fixedly sleeved on the adjusting screw 1702.

[0036] Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Those skilled in the art of the present invention may make various modifications or additions to the described specific embodiments or replace them in a similar manner, but they will not deviate from the spirit of the present invention or exceed the scope defined by the attached claims. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art and related fields without creative work shall fall within the scope of protection of the present invention.

Claims

1. An ultra-low temperature electron paramagnetic resonance probe, comprising a cavity guide structure fixed in a Dewar flask through a hollow pipe extending from the top of the Dewar flask, a cavity shell with a grating structure arranged in the cavity guide structure, a ring-shaped sapphire crystal arranged in the cavity shell, and a coil fixed on the cavity guide structure, characterized in that: The annular sapphire crystal is relatively fixed to the bottom of the hollow tube, and the back wall of the cavity shell is fixedly connected with a microwave signal cable extending from the top of the Dewar flask. The microwave signal cable drives the cavity shell to move up and down relative to the annular sapphire crystal under the control of a precision lifting mechanism arranged outside the Dewar flask, so as to achieve the Q value adjustment of the resonant cavity; An elastic supporting member is provided at the bottom of the cavity shell, which is used to ensure that the annular sapphire crystal always abuts against the hollow tube during the upward and downward movement of the cavity shell; The elastic supporting part is a non-magnetic compression spring; an upper limit part is provided at the top of the annular sapphire crystal, a lower limit part is provided at the bottom, and a compression spring fixing part is provided at the bottom of the lower limit part; the top of the non-magnetic compression spring is sleeved on the compression spring fixing part, and the bottom is tightened by a hand-tightened nut that is detachably fixed to the bottom of the cavity shell.

2. The ultra-low temperature electron paramagnetic resonance probe according to claim 1, characterized in that: A cable guide groove is provided on one side of the cavity shell for introducing a microwave signal cable vertically extending into the Dewar flask therein, and a fixed cover plate is threadedly connected to the outer side of the cable guide groove.

3. The ultra-low temperature electron paramagnetic resonance probe according to claim 1, characterized in that: The cavity guide structure has a cavity wall on both sides of the cavity shell corresponding to which a winding groove made of non-metallic material is detachably fixed, and a coil baffle made of non-metallic material is arranged outside the winding groove.

4. A Q-switching mechanism for an ultra-low temperature electron paramagnetic resonance probe according to any one of claims 1 to 3, characterized in that: The precision lifting mechanism drives the microwave signal cable and the cavity housing to move up and down relative to the annular sapphire crystal; The precision lifting mechanism includes a clamping part fixed on the microwave signal cable, a fixing part and an adjusting part arranged on both sides of the clamping part, and an adjusting support rod passing through the fixing part, the clamping part and the adjusting part; the adjusting support rod is hinged with the fixing part, the clamping part and the adjusting part, and when the adjusting part is moved up and down, the adjusting support rod rotates around the hinge axis with the fixing part, thereby driving the clamping part to move up and down, thereby realizing the lifting and lowering action of the microwave signal cable.

5. The Q-switching mechanism of the ultra-low temperature electron paramagnetic resonance probe according to claim 4, characterized in that: The fixing part and the adjusting part are fixed on the sealing seat at the top of the Dewar flask.

6. The Q-switching mechanism of the ultra-low temperature electron paramagnetic resonance probe according to claim 5, characterized in that: The adjusting member is moved up and down by a thread lifting mechanism.

7. The Q-switching mechanism of the ultra-low temperature electron paramagnetic resonance probe according to claim 6, characterized in that: The adjusting member is mainly composed of an internal thread pin fixed to one side of the sealing seat, an adjusting screw rod penetrating the internal thread pin, and an adjusting support rod hinge seat arranged on the top of the adjusting screw rod.

8. The Q-switching mechanism of the ultra-low temperature electron paramagnetic resonance probe according to claim 7, characterized in that: The upper fixed sleeve of the adjusting screw is provided with a hand-twisted rotating disk.

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