CN117148233B - Weak magnetic measurement device and method for non-uniform broadening of ESR - Google Patents
Weak magnetic measurement device and method for non-uniform broadening of ESR Download PDFInfo
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Abstract
The invention discloses a weak magnetic measurement device aiming at non-uniform spreading of ESR, and also discloses a weak magnetic measurement method aiming at non-uniform spreading of ESR. The method comprises the following steps: setting a system working time sequence; configuring radio frequency excitation parameters; polarizing the sample; signal receiving and preprocessing; frequency measurement, magnetic field conversion and data storage; and starting the next measurement according to the measurement period waiting interval time. The invention can overcome the defect of low electron excitation rate caused by time-frequency excitation in the magnetic field measurement in the prior art, thereby effectively relieving the problem of limited polarization enhancement caused by the low electron excitation rate, improving the initial signal-to-noise ratio of the FID signal and further improving the magnetic field measurement precision and sensitivity index.
Description
Technical Field
The invention belongs to the field of weak magnetic field measurement, and particularly relates to a weak magnetic measurement device for non-uniform broadening of ESR and a weak magnetic measurement method for non-uniform broadening of ESR.
Background
The Overhauser magnetometer is widely used for measuring weak magnetic fields, particularly field geomagnetic fields, and based on the Overhauser effect of Dynamic Nuclear Polarization (DNP), free electrons in a polarizer sample are saturated and excited under the action of a radio frequency field to obtain high polarization, and the high polarization of the electrons is transferred to a solvent core through the coupling effect between the electrons and the solvent core, so that the sensitivity of weak magnetic FID signals is greatly improved. The Overhauser magnetometer consists of a magnetic measurement probe, a direct current polarization and radio frequency excitation module, a signal receiving and processing circuit, a main control system and the like, wherein a sample in the probe is an initial source of an FID signal, and the excited degree of the sample directly determines the signal-to-noise ratio of the initial signal.
Nitroxide radicals are commonly used DNP polarizers, which are also used as polarizers in probes in the Overhauser magnetometer because of their high stability, non-reactivity and high coupling factor due to short correlation times. In the Overhauser magnetometer magnetic field measurement process, a static magnetic field perpendicular to the measured magnetic field needs to be artificially applied to the sample area to deflect the macroscopic magnetization vector so that it can be detected by the probe, called the pre-polarized magnetic field. Due to the non-uniformity inherent in the pre-polarized magnetic field and the anisotropic inherent in the free electron Landset factor in the nitroxide free radical, the non-uniform broadening of the excitation frequency band of electron paramagnetic resonance (ESR) can be caused, so that the free electrons in the sample can be dispersed in a relatively wide excitation frequency range. Most of the prior schemes are based on single-frequency excitation of a fixed mode, and the schemes can only excite free electrons in partial samples corresponding to the set frequency in a saturated manner, so that the utilization rate of the polarizer samples is low, the maximum saturation factor is reduced, the enhancement multiple of weak magnetic signals is reduced, and the sensitivity and the precision of final magnetic field measurement are influenced.
Disclosure of Invention
The invention aims to solve the problems in the prior art, and provides a weak magnetic measurement device for non-uniform stretching of ESR and a weak magnetic measurement method for non-uniform stretching of ESR, so as to solve the problem of limited polarization enhancement caused by low electron excitation rate in the prior art.
The above object of the present invention is achieved by the following technical solutions:
a weak magnetic measuring device aiming at non-uniform spreading of ESR comprises a control module, a transmitting module, a probe, an electronic polarizer tuning circuit, a receiving module and a calculation storage module,
the transmitting module comprises a DDS, a combiner, a radio frequency switch and a radio frequency power amplifier which are sequentially connected, the transmitting module also comprises a direct current polarization circuit,
the probe comprises a direct current polarization detection coil and an electronic polarizer,
the control module is respectively connected with the DDS, the radio frequency switch, the direct current polarization circuit, the electronic polarizer tuning circuit and the calculation storage module,
the radio frequency power amplifier is connected with the electronic polarizer, the direct current polarization circuit is connected with the direct current polarization detection coil, the electronic polarizer tuning circuit is connected with the electronic polarizer, the receiving module is connected with the direct current polarization detection coil, and the calculation storage module is connected with the receiving module.
The receiving module comprises a tuning circuit, a filtering and amplifying circuit and a sampling circuit which are sequentially connected, the sampling circuit is connected with the calculation storage module, and the tuning circuit is connected with the direct current polarization detection coil.
A method of flux weakening measurement for non-uniform broadening of ESR comprising the steps of:
step S201, setting a system working time sequence, including the starting time and the duration time of the application of a radio frequency power signal and a direct current polarized current signal, the starting time and the duration time of the reception of an FID signal and the interval time of repeated measurement;
step S202, configuring radio frequency excitation parameters including sample excitation bandwidth B and sweep frequency steppingProbe tuning steppingRadio frequency channel number and sweep Rate V S ；
Step S203, a control module controls each channel of the DDS to output corresponding sweep frequency signals according to radio frequency excitation parameters, the multi-channel sweep frequency signals output by the DDS are subjected to signal combination through a combiner to generate combined sweep frequency signals, power amplification is carried out through a radio frequency power amplifier to output radio frequency power signals to an electronic polarizer, a radio frequency magnetic field for exciting electronic transition is generated in a sample area, a direct current polarization circuit outputs a direct current polarization current signal to a direct current polarization detection coil, a static magnetic field for deflecting a magnetization vector is generated in the sample area, and the sample is polarized under the action of the radio frequency magnetic field and the static magnetic field;
step S204, in the signal receiving stage, the direct current polarization detection coil outputs an FID signal, and the receiving module filters and amplifies the FID signal and then samples the FID signal to obtain signal sampling data;
step S205, the receiving module sends the signal sampling data to the calculating and storing module for frequency calculation, and converts the signal sampling data into the magnetic field strength B to be measured m ；
，
Wherein B is m For the intensity of the magnetic field to be measured,for the measured FID signal frequency, < >>Gyromagnetic ratio as solvent nuclei;
step S206, waiting interval time t r Then, the process goes to step S203 to start the next measurement.
In step S201, the DC polarized current signal and the RF power signal are turned on and off synchronously, and the duration t of the DC polarized current signal dc Equal to the duration t of the radio frequency power signal rf In step S203, after the DC polarized current signal and the RF power signal are turned off, waiting for the dead time t d Then, step S204 and step S205 are performed, and the FID signal reception duration is t m Then wait for an interval t r The process returns to step S203 to perform the next measurement cycle.
In step S202 as described above, the sample excitation bandwidth B is determined by a dot frequency excitation boost experiment, which includes the steps of:
setting a frequency band, traversing from the lower limit frequency to the upper limit frequency of the set frequency band, sequentially selecting frequencies in the frequency band as selected excitation frequencies according to set steps, utilizing a transmitting module to output single-frequency radio frequency power signals under each selected excitation frequency to excite electronic transition, utilizing a calculation storage module to measure and record signal amplitude values output by a receiving module, obtaining signal amplitude values corresponding to each selected excitation frequency in the set frequency band, controlling an electronic polarizer tuning circuit to enable the electronic polarizer to resonate all the time under the selected excitation frequency in the traversing process, finally drawing an enhanced signal amplitude change curve according to the recorded signal amplitude values, and selecting a 3dB attenuation bandwidth of the enhanced signal amplitude change curve as a sample excitation bandwidth B.
And also includes probe available bandwidthIs determined by the following steps:
measuring S of the electronic polarizer at the center frequency of the excitation bandwidth B of the sample by a vector network analyzer when the probe is filled with the sample 11 Parameter curve, select S 11 The frequency range corresponding to-10 dB on the parameter curve is used as the available bandwidth of the probe。
In step S203 as described above, as a first embodiment; the control module controlling each channel of the DDS to output corresponding sweep frequency signals according to the radio frequency excitation parameters comprises: m times the traversing sweep within the sample excitation bandwidth B,wherein, the method comprises the steps of, wherein,time of RF power signal application, T, for single magnetic field measurement B To complete the corresponding sweep excitation period of the whole sample excitation bandwidth B at a time.
For the traversing sweep frequency in the single sample excitation bandwidth B, the specific steps are as follows:
the excitation bandwidth B of the sample is based on the available bandwidth of the probeEvenly dividing the probe into a plurality of frequency intervals which are distributed in sequence, so that the range of each frequency interval and the available bandwidth of the probe are +.>Equal, while probe tuning step +.>Also set the available bandwidth with the probeEqually, each frequency interval is divided into a plurality of frequency sweep subintervals according to channels in turn, and in the frequency sweep of each frequency sweep subinterval, the channel of the corresponding DDS scans the frequency according to the frequency sweep starting frequency and the frequency sweep stopping frequency of the following formula:
，
，
wherein,and->Representing the corresponding sweep excitation period T over the entire sample excitation bandwidth B at one time B In the DDS, the ith channel of the DDS is provided with a sweep frequency starting frequency and a sweep frequency stopping frequency in 1 sweep frequency period corresponding to the jth probe tuning period, < >>Represents the sweep range of the ith channel, +.>Representing the lower frequency limit corresponding to the excitation bandwidth B of the sample,
sweep frequency stepping as described aboveCalculated based on the following formula:
，
wherein,the number of sweep cycles to be completed in a single tuning for each channel, N being the number of channels, T B To complete the corresponding sweep excitation period of the whole sample excitation bandwidth B at a time, B is the sample excitation bandwidth, < ->For the DDS sweep minimum dwell time,
the sweep rate V S Calculated based on the following formula:
，
wherein,the steps are tuned for the probe.
As described above in step S203, as a second embodiment, the control module (101) controlling each channel of the DDS (102 a) to output a corresponding sweep frequency signal according to the radio frequency excitation parameter includes: m times the traversing sweep within the sample excitation bandwidth B,
，
wherein,time of RF power signal application, T, for single magnetic field measurement B To finishThe sweep frequency excitation period corresponding to the whole sample excitation bandwidth B is formed at one time.
For a traversing sweep within the single sample excitation bandwidth B, the steps are based on the following formula:
，
，
，
wherein,and->Respectively represents the corresponding sweep excitation period T of the whole sample excitation bandwidth B at one time B In, the sweep frequency starting frequency and the sweep frequency ending frequency of each channel of the DDS are>Indicates the channel number, N is the channel number, +.>And->Respectively representing the lower limit frequency and the upper limit frequency of the sample excitation bandwidth B, V S Indicating the sweep rate required to be set for each channel.
Compared with the prior art, the invention has the following beneficial effects:
the invention solves the problems of low electron excitation rate and limited polarization enhancement caused by frequency excitation when measuring a magnetic field in the prior art, improves the initial signal-to-noise ratio of the FID signal, and further improves the magnetic field measurement precision and sensitivity index.
Drawings
FIG. 1 is a schematic diagram of a weak magnetic measurement device for non-uniform broadening of ESR according to the present invention.
FIG. 2 is a flow chart of a method of measuring Weak magnetic flux for non-uniform broadening of ESR in accordance with the present invention.
FIG. 3 is a schematic diagram of the system operation sequence of the present invention.
Fig. 4 is a schematic diagram of the sweep excitation in the first embodiment of example 4.
Fig. 5 is a schematic diagram of a single channel single tuning sweep of mode one of example 4.
Fig. 6 is a schematic diagram of the swept excitation of mode two in example 4.
Fig. 7 is a schematic diagram of a single channel single tuning sweep for mode two in example 4.
Detailed Description
The invention will now be described in further detail with reference to the following examples, which are given by way of illustration and explanation only, and are not intended to be limiting, for the understanding and practice of the invention by those of ordinary skill in the art.
Example 1
As shown in fig. 1, in the present embodiment, a weak magnetic measurement device for ESR non-uniform broadening is provided, which mainly includes a control module 101, a transmitting module 102, a probe 103, an electronic polarizer tuning circuit 104, a receiving module 105, and a calculation storage module 106.
As a preferred embodiment of the present invention, the transmitting module 102 includes a DDS (direct digital frequency synthesizer) 102a, a combiner 102b, a radio frequency switch 102c, a radio frequency power amplifier 102d and a dc polarization circuit 102e, the probe 103 includes a dc polarization detecting coil 103a and an electronic polarizer 103b, and the receiving module 105 includes a tuning circuit 105a, an amplifying and filtering circuit 105b and a sampling circuit 105c. The modules or components are described in detail below.
The control module 101 is configured to control a working sequence of each module of the device, and in a transmitting stage of magnetic field measurement, control the DDS102a to output a corresponding sweep frequency signal, control the dc polarization circuit 102e to output a corresponding dc polarization current signal, and control the electronic polarizer tuning circuit 104 to tune and match the electronic polarizer 103b, so that the electronic polarizer 103b has good power transmission at each excitation frequency, thereby ensuring efficiency of a radio frequency power signal and safety of a preceding stage radio frequency device. In the transmitting module 102, the DDS102a, the combiner 102b, the radio frequency switch 102c and the radio frequency power amplifier 102d form a radio frequency transmitting circuit, where the DDS102a may provide a multi-channel radio frequency signal output; the combiner 102b combines the multichannel sweep frequency signals to obtain a combined sweep frequency signal, and the combined sweep frequency signal is output to the radio frequency power amplifier 102d through the radio frequency switch 102 c; the radio frequency switch 102c and the direct current polarization circuit 102e are turned on and off under the control of the control module 101, so that the required system working time sequence can be completed; the rf power amplifier 102d power amplifies the combined swept frequency signal from the combiner 102b to obtain an rf power signal to provide a sufficient power output. In the probe 103, as a preferred scheme, an electronic polarizer 103b and a direct current polarization detection coil 103a are coaxially arranged, and the electronic polarizer 103b is responsible for receiving the radio frequency power signal from the radio frequency power amplifier 102d, so as to generate a radio frequency magnetic field to excite electronic transitions in a sample area; the dc polarization detection coil 103a is responsible for receiving the dc polarization current signal from the dc polarization circuit 102e to generate a static magnetic field of the deflection magnetization vector in the sample region, and also responsible for receiving the FID signal from the sample in the signal receiving stage. The receiving module 105 is responsible for filtering, amplifying, sampling, etc. the weak FID signal from the dc polarization detection coil 103 a. The calculation storage module 106 performs voltage measurement, frequency calculation, and magnetic field strength conversion on the FID signal from the reception module 105 and performs a data storage function.
Example 2
Based on the weak magnetic measurement device, a weak magnetic measurement method for non-uniform broadening of ESR, using a weak magnetic measurement device for non-uniform broadening of ESR described in embodiment 1, as shown in fig. 2, comprises the following steps:
step S201, setting a system operation time sequence, including the start and duration of the application of the rf power signal and the dc polarized current signal, the start and duration of the reception of the FID signal, and the interval time of repeated measurement, etc., where the control module 101 controls other modules according to the set system operation time sequence.
Step S202, configuring radio frequency excitation parameters including sample excitation bandwidth B and sweep frequency steppingProbe tuning steppingRadio frequency channel number and sweep Rate V S Etc.
In step S203, the control module 101 controls each channel of the DDS102a to output a corresponding sweep frequency signal according to the set radio frequency excitation parameters. The multi-channel sweep frequency signal output by the DDS102a is subjected to signal combination by the combiner 102b to generate a combined sweep frequency signal, and is subjected to power amplification by the radio frequency power amplifier 102d to output a radio frequency power signal with certain power to the electronic polarizer 103b in the probe 103, a radio frequency magnetic field capable of exciting electronic transition is generated in a sample area, meanwhile, under the system operation time sequence constraint set in the step S201, a direct current polarization circuit 102e outputs a proper direct current polarization current signal to a direct current polarization detection coil 103a in the probe 103, a static magnetic field for deflecting a magnetization vector is generated in the sample area, and the sample is sufficiently polarized under the action of the radio frequency magnetic field and the static magnetic field.
In step S204, the signal receiving and preprocessing, during the signal receiving stage, the direct current polarization detection coil 103a outputs the FID signal, and the receiving module 105 performs filtering, amplifying and other processes on the FID signal, so that the FID signal can be better sampled and further processed, and samples the filtered and amplified FID signal to obtain signal sampling data.
Step S205, frequency measurement and data storage, the signal sampling data are sent to the calculation storage module 106 for frequency calculation, converted into the magnetic field strength to be measured according to the formula 1, and then data storage is carried out according to the requirement.
（1）
Wherein B is m For the strength of the magnetic field to be measured,for the measured FID signal frequency, < >>Gyromagnetic ratio is the solvent nucleus (typically proton).
Step S206, waiting interval time t r Then, the process goes to step S203 to start the next measurement cycle.
Example 3
As shown in FIG. 3, as an optional system operation sequence, in step S201, the applied DC polarized current signal and the RF power signal are synchronously turned on and off, and the durations of the two signals are the same, namely, the duration t of the DC polarized current signal dc Equal to the duration t of the radio frequency power signal rf Step S203 is performed to wait for dead time t after the DC polarized current signal and the RF power signal are turned off d Then, the steps S204 and S205 are performed, the FID signal reception and the frequency measurement are performed, and the FID signal reception duration is t m Then wait for an interval time T according to the measurement period T as shown in FIG. 3 r The process returns to step S203 to perform the next measurement. Otherwise, the same as in example 2 was used.
Example 4
On the basis of example 3, the excitation bandwidth of the sample is defined as B, and the available bandwidth of the probe is defined asThe number of the sweep frequency channels is N, and the tuning steps of the probe are +.>. Further, the sample excitation bandwidth B can be determined by point frequency excitation enhancement experiments, specifically, a wider frequency band is set, and the frequency band is stepped from the lower limit frequency to the upper limit frequency of the set frequency bandSequentially traversing the frequencies in the selected frequency band as the selected excitation frequency. According to the operation sequence shown in fig. 3, the emission module 102 is used to output a single-frequency radio frequency power signal at each selected excitation frequency to excite electronic transition, and then the calculation storage module 106 is used to measure and record the signal amplitude output by the receiving module 105, so as to complete measurement of one frequency point and obtain the signal amplitude corresponding to each selected excitation frequency in the set frequency band. In the traversal process, the electronic polarizer 103b is always resonated at the selected excitation frequency by controlling the electronic polarizer tuning circuit 104, and finally, an enhanced signal amplitude variation curve is drawn according to the recorded signal amplitude. The sample excitation bandwidth is determined according to the enhancement signal amplitude variation curve, preferably, the 3dB attenuation bandwidth is selected as the sample excitation bandwidth, namely, the frequency corresponding to the highest amplitude of the enhancement signal amplitude variation curve is used as the center frequency, the center frequency is used as the starting point to search towards the two sides of the enhancement signal amplitude variation curve, and the frequency that the amplitude of the enhancement signal amplitude variation curve is reduced to the highest amplitude is found>The frequency corresponding to the time of the multiplication is used as an upper limit of the excitation frequency and a lower limit of the excitation frequency.
Further, probe available bandwidthBased on the on-load Q value of the electronic polarizer 103B, when the probe 103 is filled with a sample, the S of the electronic polarizer 103B at the center frequency of the excitation bandwidth B of the sample is measured by a vector network analyzer 11 Parameter profile, preferably, select S 11 The frequency range corresponding to-10 dB on the parameter curve is used as the available bandwidth of the probe>I.e., greater than 90% of the incident power is delivered to the electron polarizer 103b for exciting electrons.
Further, the number N of the sweep frequency channels is based on the available bandwidth of the probeSetting, usually probingHead available bandwidth +.>The larger the number of channels is, the more channels are, and the sweep initial frequency of each channel is uniformly distributed in the available bandwidth of the probe>And setting the sweep rate and the sweep step of each channel to be the same parameters.
Further, the probe tunes the stepAnd the method is specifically determined according to the frequency sweep mode. As an alternative to the frequency sweep, namely, the frequency sweep one, as shown in FIG. 4, the sample excitation bandwidth B is divided into a plurality of frequency intervals and the frequency intervals are sequentially subjected to frequency sweep excitation, preferably, the sample excitation bandwidth B can be determined according to the available bandwidth of the probe +.>Evenly dividing the probe into a plurality of frequency intervals which are distributed in sequence, so that the range of each frequency interval and the available bandwidth of the probe are +.>Equal, while probe tuning step +.>Also set the available bandwidth of the probe +.>Equal, i.e. probe available bandwidth +.>In the single tuning period, just covering a frequency interval, each frequency interval is divided into a plurality of frequency sweep subintervals according to channels in turn, in the frequency sweep of each frequency sweep subinterval, the corresponding frequency sweep starting frequency and frequency sweep stopping frequency of the channel of the DDS102a are carried out according to the frequency sweep starting frequency and frequency sweep stopping frequency of the formula 3, so that the N-channel frequency sweep of the electronic polarizer 103B in the whole sample excitation bandwidth B range has good matching, thereby ensuring high efficiencyIncident power transmission. In the single tuning of the probe in the sweep frequency mode, the scanning frequency of the DDS signals of each channel is uniformly distributed in the available bandwidth of the probe +.>On the ith channel of DDS102a, sweep frequency range S i Occupy only the available bandwidth of the probe +.>Satisfying the characteristics described in equation 2, each channel needs to complete several cycles of frequency sweep in each allocated frequency range when sweeping a certain frequency range.
（2）
Specifically, in one probe tuning period, the sweep mode of each channel of the DDS102a is shown in fig. 5, and the characteristics thereof are described by equation 3.
（3）
Wherein,and->Representing the corresponding sweep excitation period T over the entire sample excitation bandwidth B at one time B In the DDS, the ith channel of the DDS is provided with a sweep frequency starting frequency and a sweep frequency stopping frequency in 1 sweep frequency period corresponding to the jth probe tuning period, < >>Represents the sweep range of the ith channel, +.>Representing the lower frequency limit corresponding to the excitation bandwidth B of the sample. The sweep pattern described by equation 3 may be further supplemented as: corresponding to the whole sample excitation bandwidth B after completing one timeIs of sweep excitation period T B In the step, after the sweep excitation of the current probe tuning period is completed, the control module 101 controls the electronic polarizer tuning circuit 104 to step the electronic polarizer 103b to +.>Enters the next probe tuning period, at which time each channel of the DDS will directly add probe tuning steps +.>And (3) carrying out frequency sweep, carrying out the same operation on subsequent probe tuning until the whole sample excitation bandwidth B is traversed, then jumping to the initial frequency under the first probe tuning, repeating the steps for M times, and calculating the M value according to the formula 4.
（4）
Wherein,time of RF power signal application, T, for single magnetic field measurement B To complete the corresponding sweep excitation period of the whole sample excitation bandwidth B at a time. Further, sweep step for each channel>Which is limited by the performance of the DDS device, in order to improve the linearity of the frequency sweep, the frequency sweep should be stepped as much as possible>Near the minimum allowed by DDS device performance, assume that each channel requires N number of sweep cycles to be completed in a single tuning S The minimum residence time of the DDS frequency sweep is +.>Sweep frequency step +.>Can be represented by equation 5.
（5）
Wherein,tuning the step for the probe +.>The number of sweep cycles to be completed in a single tuning for each channel, N being the number of channels, T B To complete the corresponding sweep excitation period of the whole sample excitation bandwidth B at a time, B is the sample excitation bandwidth, < ->The minimum residence time is swept for the DDS.
According to the above parameter configuration, the sweep rate V required to be set for each channel S Can be calculated by equation 6
（6）
As an alternative to the frequency sweep, namely frequency sweep two, as shown in FIG. 6, to achieve both linearity of the frequency sweep and complexity of the electronic polarizer tuning circuit 104, the probe tunes the stepShould take the value properly, optionally, let. In this sweep mode, the probe tuning and the sweep frequency switching are performed synchronously, and a schematic diagram of the sweep mode of each channel in the whole sample excitation bandwidth B range is shown in fig. 7, and can be described by equation 7:
（7）
wherein,and->Respectively represents the corresponding sweep excitation period T of the whole sample excitation bandwidth B at one time B In, the sweep frequency starting frequency and the sweep frequency ending frequency of each channel of the DDS are>Indicates the channel number,/-, and>and->Respectively representing the lower limit frequency and the upper limit frequency of the sample excitation bandwidth B, V S Indicating the sweep rate required to be set for each channel. The sweep pattern described by equation 3 may be further supplemented as: the starting frequencies of the DDS102a channels are uniformly distributed in the available bandwidth of the probe>In each channel from the respective start frequency +.>When the frequency sweep is started and the channel frequency is switched, all channels are synchronized to be in frequency sweep step +>Frequency switching is performed and electronic polarizer tuning circuit 104 synchronizes the probe tuning step for electronic polarizer 103b>Tuning, frequency sweep step->Equal to the probe tuning step +.>The output frequency of each channel is stepped according to the sweep frequency>Increment until proceeding to the respective termination frequency +.>And finally, completing the sweep excitation in the whole sample excitation bandwidth B once, and then jumping each channel to the respective initial frequency +.>The next cycle of sweep is performed, and the number of cycles for each measurement is M (see formula 4), during which the probe tuning and the sweep of each channel are performed synchronously, and the steps of the two are kept consistent.
The first frequency sweeping mode and the second frequency sweeping mode can solve the problem of non-uniform spread of ESR caused by non-uniform pre-polarized magnetic field and g factor anisotropy through radio frequency excitation in a wide frequency range, and the utilization rate of free electrons in a space scale is improved; meanwhile, the adopted multi-channel sweep frequency signal can ensure that electrons with N (channel number) frequencies are excited at any time and shorten the sweep frequency period T under the limited sweep frequency rate caused by hardware limitation B Thereby overcoming the adverse effect of the ultra-fast relaxation of electrons at normal temperature on the utilization rate of free electrons in time dimension.
It should be noted that the specific embodiments described in this application are merely illustrative of the spirit of the invention. Those skilled in the art may make various modifications or additions to the described embodiments or substitutions thereof without departing from the spirit of the invention or its scope as defined in the accompanying claims.
Claims (9)
1. The weak magnetic measurement device for the non-uniform broadening of the ESR comprises a control module (101), and is characterized by further comprising a transmitting module (102), a probe (103), an electronic polarizer tuning circuit (104), a receiving module (105) and a calculation storage module (106),
the transmitting module (102) comprises a DDS (102 a), a combiner (102 b), a radio frequency switch (102 c) and a radio frequency power amplifier (102 d) which are sequentially connected, the transmitting module (102) also comprises a direct current polarization circuit (102 e),
the probe (103) comprises a DC polarization detection coil (103 a) and an electronic polarizer (103 b),
the control module (101) is respectively connected with the DDS (102 a), the radio frequency switch (102 c), the direct current polarization circuit (102 e), the electronic polarizer tuning circuit (104) and the calculation storage module (106),
the radio frequency power amplifier (102 d) is connected with the electronic polarizer (103 b), the direct current polarization circuit (102 e) is connected with the direct current polarization detection coil (103 a), the electronic polarizer tuning circuit (104) is connected with the electronic polarizer (103 b), the receiving module (105) is connected with the direct current polarization detection coil (103 a), the calculation storage module (106) is connected with the receiving module (105),
the control module (101) controls each channel of the DDS (102 a) to output corresponding sweep frequency signals according to the radio frequency excitation parameters to carry out traversing sweep frequency in the sample excitation bandwidth B for M times,
in the traversal sweep within single sample excitation bandwidth B: the channel of the DDS (102 a) scans the frequency according to the sweep start frequency and sweep stop frequency of the following formula:
，
，
wherein,and->Representing the corresponding sweep excitation period T over the entire sample excitation bandwidth B at one time B In the DDS (102 a), the ith channel has a sweep start frequency and sweep frequency in 1 sweep period corresponding to the jth probe tuning periodFrequency stop frequency, ++>Represents the sweep range of the ith channel, +.>Represents the lower frequency corresponding to the excitation bandwidth B of the sample, < >>Tuning the step for the probe +.>For the available bandwidth of the probe, N is the number of channels.
2. The device for measuring ESR non-uniform broadening of a weak magnetic field according to claim 1, wherein the receiving module (105) comprises a tuning circuit (105 a), a filtering and amplifying circuit (105 b) and a sampling circuit (105 c) which are sequentially connected, the sampling circuit is connected with a calculation storage module (106), and the tuning circuit (105 a) is connected with a dc polarization detection coil (103 a).
3. A method for measuring weak magnetic field for non-uniform spreading of ESR using a weak magnetic field measuring device for non-uniform spreading of ESR according to claim 1, comprising the steps of:
step S201, setting a system working time sequence, including the starting time and the duration time of the application of a radio frequency power signal and a direct current polarized current signal, the starting time and the duration time of the reception of an FID signal and the interval time of repeated measurement;
step S202, configuring radio frequency excitation parameters including sample excitation bandwidth B and sweep frequency steppingProbe tuning step->Radiation and fireFrequency channel number and sweep Rate V S ；
Step S203, a control module (101) controls each channel of a DDS (102 a) to output corresponding sweep frequency signals according to radio frequency excitation parameters, the multi-channel sweep frequency signals output by the DDS (102 a) are subjected to signal combination by a combiner (102 b) to generate combined sweep frequency signals, a radio frequency power amplifier (102 d) is used for carrying out power amplification to output radio frequency power signals to an electronic polarizer (103 b), a radio frequency magnetic field for exciting electronic transition is generated in a sample area, a direct current polarization circuit (102 e) outputs a direct current polarization current signal to a direct current polarization detection coil (103 a), a static magnetic field for deflecting a magnetization vector is generated in the sample area, and a sample is polarized under the action of the radio frequency magnetic field and the static magnetic field;
step S204, in the signal receiving stage, the direct current polarization detection coil (103 a) outputs an FID signal, and the receiving module (105) filters and amplifies the FID signal and then samples the FID signal to obtain signal sampling data;
step S205, the receiving module (105) sends the signal sampling data to the calculating and storing module (106) for frequency calculation, and converts the signal sampling data into the magnetic field strength B to be measured m ；
，
Wherein B is m For the intensity of the magnetic field to be measured,for the measured FID signal frequency, < >>Gyromagnetic ratio as solvent nuclei;
step S206, waiting interval time t r Then, the process goes to step S203 to start the next measurement.
4. A weak magnetic measurement method for non-uniform broadening of ESR according to claim 3, wherein, in step S201,the direct current polarized current signal and the radio frequency power signal are synchronously turned on and off, and the duration t of the direct current polarized current signal dc Equal to the duration t of the radio frequency power signal rf In step S203, after the DC polarized current signal and the RF power signal are turned off, waiting for the dead time t d Then, step S204 and step S205 are performed, and the FID signal reception duration is t m Then wait for an interval t r The process returns to step S203 to perform the next measurement cycle.
5. The method of claim 3, wherein in the step S202, the sample excitation bandwidth B is determined by a point frequency excitation boost experiment, and the point frequency excitation boost experiment includes the steps of:
setting a frequency band, traversing from the lower limit frequency to the upper limit frequency of the set frequency band, sequentially selecting frequencies in the frequency band as selected excitation frequencies according to set steps, utilizing a transmitting module (102) to output single-frequency radio frequency power signals under each selected excitation frequency to excite electronic transition, utilizing a calculation storage module (106) to measure and record signal amplitude values output by a receiving module (105), obtaining signal amplitude values corresponding to each selected excitation frequency in the set frequency band, enabling an electronic polarizer (103B) to resonate all the time under the selected excitation frequency in the traversing process, finally drawing an enhanced signal amplitude change curve according to the recorded signal amplitude values, and selecting a 3dB attenuation bandwidth of the enhanced signal amplitude change curve as a sample excitation bandwidth B.
6. The method of claim 3, further comprising a probe usable bandwidthIs determined by the following steps:
measuring S of the electronic polarizer (103B) at the center frequency of the excitation bandwidth B of the sample by a vector network analyzer when the probe (103) is filled with the sample 11 Parameter curve, select S 11 The frequency range corresponding to-10 dB on the parameter curve is used as the available bandwidth of the probe。
7. A method for measuring weak magnetic field for non-uniform broadening of ESR according to claim 3, wherein in step S203, the control module (101) controls each channel of the DDS (102 a) to output a sweep signal with a corresponding frequency according to the radio frequency excitation parameter, and the method comprises: m times the traversing sweep within the sample excitation bandwidth B,
，
wherein,time of RF power signal application, T, for single magnetic field measurement B In order to complete the sweep frequency excitation period corresponding to the whole sample excitation bandwidth B at a time, the steps of traversing the sweep frequency in the single sample excitation bandwidth B are as follows:
the excitation bandwidth B of the sample is based on the available bandwidth of the probeEvenly dividing the probe into a plurality of frequency intervals which are distributed in sequence, so that the range of each frequency interval and the available bandwidth of the probe are +.>Equal, while probe tuning step +.>Also set the available bandwidth of the probe +.>Equally, each frequency interval is divided into a plurality of frequency sweeping subintervals according to channels in turn, and each frequency sweeping subinterval is divided into a plurality of frequency sweeping subintervalsIn the frequency sweep of the subinterval, the corresponding channel of the DDS (102 a) carries out frequency sweep according to the frequency sweep starting frequency and the frequency sweep stopping frequency of the following formula:
，
，
wherein,and->Representing the corresponding sweep excitation period T over the entire sample excitation bandwidth B at one time B In the DDS (102 a), the ith channel has a frequency sweep starting frequency and a frequency sweep stopping frequency in 1 frequency sweep period corresponding to the jth probe tuning period, < + >>Represents the sweep range of the ith channel, +.>Representing the lower frequency limit corresponding to the excitation bandwidth B of the sample.
8. The method of claim 7, wherein the sweep step is performed byCalculated based on the following formula:
，
wherein,the number of sweep cycles to be completed in a single tuning for each channel, N being the number of channels, T B To complete the corresponding sweep excitation period of the whole sample excitation bandwidth B at a time, B is the sample excitation bandwidth, < ->For the DDS sweep minimum dwell time,
the sweep rate V S Calculated based on the following formula:
，
wherein,the steps are tuned for the probe.
9. A method for measuring weak magnetic field for non-uniform broadening of ESR according to claim 3, wherein in step S203, the controlling module (101) controlling each channel of the DDS (102 a) to output a corresponding sweep frequency signal according to the radio frequency excitation parameter comprises: m times the traversing sweep within the sample excitation bandwidth B,
，
wherein,time of RF power signal application, T, for single magnetic field measurement B To complete the corresponding sweep excitation period for the entire sample excitation bandwidth B at one time,
for a traversal sweep within the single sample excitation bandwidth B, the frequency signal traversal step is based on the following formula:
，
，
，
wherein,and->Respectively represents the corresponding sweep excitation period T of the whole sample excitation bandwidth B at one time B In, the sweep frequency starting frequency and the sweep frequency ending frequency of each channel of the DDS are>Indicates the channel number, N is the channel number, +.>And->Respectively representing the lower limit frequency and the upper limit frequency of the sample excitation bandwidth B, V S Indicating the sweep rate required to be set for each channel.
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3376499A (en) * | 1965-01-27 | 1968-04-02 | Varian Associates | Signal processing apparatus for facilitating the display of fine structure in gyromagnetic resonance signals |
| US6008644A (en) * | 1996-07-05 | 1999-12-28 | Picker Nordstar Oy | Nuclear Polarization Enhanced Nuclear Magnetic Resonance Imaaging |
| CN105717153A (en) * | 2016-01-28 | 2016-06-29 | 中国科学院武汉物理与数学研究所 | Parallel magnetic resonance method based on dynamical nuclear polarization multinuclear simultaneous enhancement |
| CN110618464A (en) * | 2019-06-28 | 2019-12-27 | 中国地质大学（武汉） | System and method for improving Larmor precession signal-to-noise ratio of Overhauser magnetic sensor |
| CN114002258A (en) * | 2021-10-31 | 2022-02-01 | 中国科学院精密测量科学与技术创新研究院 | Method for rapidly measuring two-dimensional relaxation by using dynamic nuclear polarization enhancement build time |
| CN114487954A (en) * | 2022-04-14 | 2022-05-13 | 中国科学院精密测量科学与技术创新研究院 | Multichannel receiving and transmitting NMR method for accurately measuring field intensity and distribution of electromagnet |
| CN114609557A (en) * | 2022-03-22 | 2022-06-10 | 中国科学技术大学 | Quantum-based multi-frequency magnetic field simultaneous amplification measurement method |
| CN115656901A (en) * | 2022-10-24 | 2023-01-31 | 重庆大学 | Magnetic resonance magnetometer device for millitesla-level magnetic field measurement |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102014218873B4 (en) * | 2014-09-19 | 2019-02-21 | Forschungszentrum Jülich GmbH | Measuring device for weak electromagnetic signals of a sample at low frequencies and methods |
-
2023
- 2023-10-31 CN CN202311430848.3A patent/CN117148233B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3376499A (en) * | 1965-01-27 | 1968-04-02 | Varian Associates | Signal processing apparatus for facilitating the display of fine structure in gyromagnetic resonance signals |
| US6008644A (en) * | 1996-07-05 | 1999-12-28 | Picker Nordstar Oy | Nuclear Polarization Enhanced Nuclear Magnetic Resonance Imaaging |
| CN105717153A (en) * | 2016-01-28 | 2016-06-29 | 中国科学院武汉物理与数学研究所 | Parallel magnetic resonance method based on dynamical nuclear polarization multinuclear simultaneous enhancement |
| CN110618464A (en) * | 2019-06-28 | 2019-12-27 | 中国地质大学（武汉） | System and method for improving Larmor precession signal-to-noise ratio of Overhauser magnetic sensor |
| CN114002258A (en) * | 2021-10-31 | 2022-02-01 | 中国科学院精密测量科学与技术创新研究院 | Method for rapidly measuring two-dimensional relaxation by using dynamic nuclear polarization enhancement build time |
| CN114609557A (en) * | 2022-03-22 | 2022-06-10 | 中国科学技术大学 | Quantum-based multi-frequency magnetic field simultaneous amplification measurement method |
| CN114487954A (en) * | 2022-04-14 | 2022-05-13 | 中国科学院精密测量科学与技术创新研究院 | Multichannel receiving and transmitting NMR method for accurately measuring field intensity and distribution of electromagnet |
| CN115656901A (en) * | 2022-10-24 | 2023-01-31 | 重庆大学 | Magnetic resonance magnetometer device for millitesla-level magnetic field measurement |
Non-Patent Citations (2)
| Title |
|---|
| Optimization of Overhauser magnetometer based on multi-channel frequency measurement algorithm;Guanzhong Wang等;Guanzhong Wang等;第10315-10319页 * |
| Overhauser 磁力仪探头激发频率测试仪研制;刘欢 等;电子学报;第45卷(第5期);第1272-1280页 * |
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