CN102830381A - Nuclear magnetic resonance (NMR) device and measurement method based on laser atomic magnetometer - Google Patents

Nuclear magnetic resonance (NMR) device and measurement method based on laser atomic magnetometer Download PDF

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CN102830381A
CN102830381A CN2012102911503A CN201210291150A CN102830381A CN 102830381 A CN102830381 A CN 102830381A CN 2012102911503 A CN2012102911503 A CN 2012102911503A CN 201210291150 A CN201210291150 A CN 201210291150A CN 102830381 A CN102830381 A CN 102830381A
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nmr
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caesium
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CN102830381B (en
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周欣
刘国宾
孙献平
刘买利
叶朝辉
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Wuhan Institute of Physics and Mathematics of CAS
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Wuhan Institute of Physics and Mathematics of CAS
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Abstract

The invention discloses a nuclear magnetic resonance (NMR) device based on a laser atomic magnetometer, and the NMR device comprises a cesium atom vapor bubble, a magnetic shielding bushing which is sleeved on the cesium atom vapor bubble, three groups of Helmholtz coils which are arranged inside the magnetic shielding bushing, a polarization device which is used for polarizing cesium atoms inside the cesium atom vapor bubble, a laser transmitting device which is used for transmitting detection laser to the cesium atom vapor bubble, a detection device which is used for detecting an NMR signal of the detection laser penetrating the cesium atom vapor bubble and a pneumatic sample feeding device which is used for pre-polarizing a sample to be detected and can place the pre-polarized sample on the cesium atom vapor bubble. The invention also discloses a measurement method of an NMR based on the laser atomic magnetometer. The device and the method are high in detection sensitivity, free from needing low-temperature refrigeration, low in running cost and lower in working temperature.

Description

A kind of NMR device and measuring method based on laser atomic magnetic force meter
Technical field
The invention belongs to nuclear magnetic resonance (Nuclear magnetic resonance; NMR) spectrum; More specifically relate to a kind of NMR device, also relate to the measuring method of a kind of NMR based on laser atomic magnetic force meter, be applicable to (1uT=10 at 100uT ~ 1nT based on laser atomic magnetic force meter -6T, 1nT=10 -9T) the NMR signal is detected in magnetic field down.u
Background technology
NMR is a kind of be used for obtaining the molecular structure that relevant atom and atom form and technology of dynamic information.NMR works to atomic nucleus, and only the atomic nucleus with non-vanishing spin is worked, and these non-vanishing nuclear spins have magnetic moment just as the small magnet that has south poles one by one, thereby can be used to NMR research.
When these magnetic moments are in the outside static magnetic field; Because there is angle in magnetic moment with outer static magnetic field; Because the generation precession, when examining with the RF magnetic field irradiated atoms, atomic nucleus absorbs RF energy; And launch the radiofrequency signal corresponding, the characteristic information that this radiofrequency signal can reaction of atomic nuclear with precession speed.Atomic nucleus is in certain environment; Interaction in various degree takes place in these environment and atomic nucleus; Be reflected on the radiofrequency signal that emits; Can cause it that relaxation phenomenon is arranged in strength, should the decay behavior through research, can obtain circumnuclear space structure of atom and dynamic behaviour information.
In the NMR wave spectrum; Change the frequency of RF magnetic field; Measure absorption and the emissive porwer of atomic nucleus to the different frequency RF magnetic field, can obtain resonance spectrum, this NMR wave spectrum can disclose the elemental composition and the content of material; Combine with correlation theory, even can obtain the structure and the movable information of each element atom.
NMR invented before and after the 1950's; In the developing history of its decades; For obtaining higher NMR spectral resolution, magnetic field intensity and RF field frequency are increasing always, from Larmor (Larmor) frequency of initial 10MHz magnitude; 900MHz up till now, even the NMR spectrometer of producer at development GHz radio-frequency field arranged.
Though High-Field NMR has high resolving power, from practical application, high field intensity and high RF frequency are restricted on some are used.Along with the raising in magnetic field, the unevenness that the magnetic sample conductance distributes can be aggravated, thereby makes signal broadening, especially comprises the sample of ferromagnetic element such as iron-cobalt-nickel, normally can't use the NMR technology to analyze.Another FAQs is magnetic resonance imaging (Magnetic resonance imaging, the magnetic susceptibility artifact in MRI).When variety classes sample or similar sample with higher susceptibility gradient were in the magnetic field, the sample composition of different magnetic susceptibility can produce parasitic gradient magnetic.When these parasitic gradient fields are suitable with the gradient fields that is used to encode, the image serious distortion of MRI.In medical imaging, the existence of metal dental filling or jewellry can destroy MRI; The saltus step of body interior solid-liquid and solid-air interface place magnetic susceptibility produces trickle distortion.
From scientific research; Usually the true environment of chemical example and biological tissue is terrestrial magnetic field (40 ~ 50uT); For obtaining branch subsample and tissue structure and the dynamic information under actual environment as far as possible, need be used in the original position research of carrying out NMR and MRI under low (terrestrial magnetic field and following) condition; Yet, traditional RF coil Detection Techniques because of its in low muting sensitivity after the match, when carrying out this type of research, have certain limitation.
Though based superconductive quantum interference device (Superconducting quantum interference device; SQUID) magnetometer; Also can realize very high detection of magnetic field sensitivity after the match, and be applied to low NMR research, but it is the same with the NMR spectrometer low; Be operated in the required low temperature environment of superconduction, still limit to some extent in application facet.
In sum; Though NMR has obtained widespread use as a kind of powerful nuclear spin analytical technology in each field; But NMR technology used RF (Radio Frequency) coil is relatively poor in low detection sensitivity after the match at present, still can not satisfy the requirement of some application.
Therefore, we need some low high sensitivity NMR instrument and technology after the match.Development in recent years has gone out several kinds low NMR instruments, and these technology have remedied traditional NMR in low muting sensitivity defective after the match.I. people such as M. Savukov is at " NMR Detection with an Atomic Magnetometer " (Phys. Rev. Lett. 94; 123001 (2005)) carrying out NMR with laser atomic magnetic force meter in detects; This laser atomic magnetic force meter uses potassium (K) atom that is in 180 ℃ as actuating medium, on the frequency range of hundreds of Hz, has 20fT/Hz at direct current 1/2Sensitivity, (Signal to noise ratio SNR) is the NMR signal that 10 unitary sampling records water with signal to noise ratio (S/N ratio).People such as V. Yashchuk in " Hyperpolarized Xenon Nuclear Spins Detected by Optical Atomic Magnetometry " (Phys. Rev. Lett. 93,160801 (2004)) with atomic magnetic force instrumentation amount the T of hyperpolarization Xe atom 1Constant.M. people such as P. Ledbetter in " Optical detection of NMR J-spectra at zero magnetic field " with laser atomic magnetic force instrumentation amount the C-H J coupling spectrum of ethanol (NMR spectrum a kind of; Can be used for confirming the structure in the chemical molecular), and this measurement is carried out under zero magnetic field.
Laser atomic magnetic force meter is based on a kind of non-linear magneto-optical rotation (Nonlinear magneto-optical rotation, quantum-mechanical phenomenon NMOR) of being called as of atom and laser interaction generation.Because the NMOR signal that this phenomenon produces has extremely narrow live width, and to magnetic-field-sensitive, therefore natural have a highly sensitive magnetic field detection ability, and in addition, even under like 100uT ~ 1nT magnitude even lower utmost point low-intensity magnetic field, this sensitivity can variation yet.
The above-mentioned method of utilizing laser atomic magnetic force meter to detect the NMR signal; Also has certain defective; Probe such as laser atomic magnetic force meter is an atomic vapour bubble that works in about 170 ~ 210 ℃, and its temperature is too high, the NMR sample is had the influence of spectral line broadening; The present invention will propose a kind of new method to this problem.
Summary of the invention
The objective of the invention is to be the problems referred to above to the prior art existence; A kind of NMR device based on laser atomic magnetic force meter is provided; The measuring method of a kind of NMR based on laser atomic magnetic force meter also is provided; Thereby solve low existing after the match radio-frequency coil method under-sensitive difficulty, and solve the too high problem of emerging atomic vapour bubble temperature.
To achieve these goals, the present invention adopts following technical scheme:
A kind of NMR device based on laser atomic magnetic force meter; Comprise the caesium atomic vapour bubble, comprise the magnetic shielding sleeve that is set on the caesium atomic vapour bubble, be arranged on three groups of Helmholtz coilss in the magnetic shielding sleeve, in the caesium atomic vapour bubble that is used to polarize the caesium atom the laser-polarization device, be used for to caesium atomic vapour bubble emission detection laser laser beam emitting device, be used to detect the NMR signal supervisory instrument of the exploring laser light that passes the caesium atomic vapour bubble and be used for sample is polarized in advance and can the sample after polarizing in advance be placed into the pneumatic sampling device of caesium atomic vapour bubble top.
Aforesaid laser-polarization device comprises that optically pumped laser converts the laser that optically pumped laser sends into be sent to the caesium atomic vapour bubble behind the circularly polarized light quarter-wave plate with being used for.
Aforesaid laser beam emitting device comprises that detecting laser converts the laser that detecting laser sends to be sent to the caesium atomic vapour bubble behind the linear polarization exploring laser light polarizing prism with being used for.
Aforesaid NMR signal supervisory instrument comprises and is used for polarization beam splitter prism that the linear polarization exploring laser light that passes the caesium atomic vapour bubble is carried out beam splitting; Be used to detect the linear polarization exploring laser light after the beam splitting and detection signal sent to the photodetector of multiplier; Be used to adjust the output frequency of optically pumped laser and export the signal generator of square wave synchronizing signal to multiplier; The multiplier that is used for detection signal and square wave synchronizing signal are carried out multiplying carries out filtering and is sent to the low-pass filter of host computer the output of multiplier with being used for.
Aforesaid pneumatic sampling device comprises cylinder, be arranged in the cylinder and an end is provided with the sample hose of the piston of fitting with cylinder inner wall, the annular polarized magnets and be used to control sample hose reciprocating drive unit in cylinder in advance that is set in cylinder one end; Offer through hole on the described magnetic shielding sleeve, cylinder one end passes through hole and is arranged on caesium atomic vapour bubble top.
Aforesaid cylinder one end is arranged with the guiding coil, and the other end is arranged with the low-angle pulsed coil, and described drive unit comprises the air compressor that pneumatic supply is provided and is used to switch the solenoid valve that air compressor is input to the airflow direction of cylinder.
Aforesaid three groups of Helmholtz coilss comprise the Helmholtz coils of three pairs of annulars; The central lines of every pair of Helmholtz coils; The center line of three pairs of Helmholtz coilss is vertical each other, and wherein the center line of a pair of Helmholtz coils is parallel with the beam direction of exploring laser light.
The measuring method of a kind of NMR based on laser atomic magnetic force meter may further comprise the steps:
Step 1, control caesium atomic vapour bubble temperature rise to 20-60 ℃; The output laser frequency of control optically pumped laser and alkaline metal caesium atom D1 line transition F=4-F '=3 resonance; And the output laser frequency of control detecting laser departs from this resonant frequency 100MHz ~ 100GHz; Electric current to optically pumped laser is modulated, and realizes the synchronizable optical pumping;
The angle of step 2, adjustment polarizing prism and quarter-wave plate obtains linear polarization exploring laser light and circularly polarized light;
The angle of step 3, adjustment polarization beam splitter prism, the signal of exporting until photodetector is zero;
Step 4, through the electric current of three groups of Helmholtz coilss of adjustment, make residual magnetic field in the magnetic shielding sleeve for minimum, obtain the adjustment electric current of three groups of Helmholtz coilss;
Electric current in center line in step 5, the three groups of Helmholtz coilss of the scanning a pair of Helmholtz coils parallel with exploring laser light; The positive current values that equates with the negative current magnitude of setting from negative current magnitude to an absolute value of setting; Be superimposed upon on the adjustment electric current described in the step 4, obtain the magnetic field distinguishing signal of low-pass filter output;
Step 6, repeating step 2 ~ step 5 are when the unit changes of magnetic field, and the changing value of low-pass filter output voltage response is maximum, and the B value of setting range of linearity center, magnetic field is a bias magnetic field;
Step 7, get the appropriate amount of fluid sample and pour sample hose into, put into cylinder;
Step 8, host computer be through the relay control electromagnetic valve, and then the control air compressor is blown into the direction in the cylinder, makes sample hose float to the inside center of the preparatory polarized magnets of annular;
Step 9, keep sample hose suspension setting-up time, make its polarization fully in advance, host computer is through the relay control electromagnetic valve, and then changes air compressor and be blown into the direction in the cylinder, makes sample hose be passed down through the guiding coil, arrives the top of caesium atomic vapour bubble;
Electric current in step 10, the control low-angle pulsed coil produces direct current or alternating-current pulse, changes the sample magnetic moment direction;
There is the little angle of 5 ~ 15 degree in the direction of step 11, sample magnetic moment and bias magnetic field, and the sample magnetic moment is done precession physically receiving the effect of a moment around bias magnetic field, and magnetic field is applied disturbance, obtains the NMR signal of time domain;
Step 12, the NMR signal through time domain obtain the NMR spectrum signal of frequency field.
The present invention compared with prior art has the following advantages and effect:
1, under downfield, compare with existing coil Detection Techniques, have higher detection sensitivity;
2, utilize SQUID to survey the NMR compared with techniques with existing low field, do not need cryogenic refrigeration, practice thrift operating cost;
3, compare with existing NMR sniffer, have lower working temperature based on the atomic magnetic force meter.
Description of drawings
Fig. 1 is a general structure synoptic diagram of the present invention;
Fig. 2 is the principle schematic of high sensitivity laser atomic magnetic force of the present invention test section;
Fig. 3 is the principle schematic of preparatory polarization of the present invention and pneumatic sample introduction part.
Among the figure: the 1-detecting laser; The 2-optically pumped laser; The 3-polarizing prism; The 4-quarter-wave plate; 5-magnetic shielding sleeve; Three groups of Helmholtz coilss of 6-; 7-caesium atomic vapour bubble; The 8-polarization beam splitter prism; The 9-photodetector; The 10-multiplier; The 11-signal generator; The 12-low-pass filter; The 13-host computer; The 14-air compressor; The 15-solenoid valve; The 16-relay; The 17-sample hose; The 18-cylinder; The 19-annular is polarized magnets in advance; 20-guides coil; 21-low-angle pulsed coil; The a-sample is polarization and pneumatic sampling device in advance; B-laser atomic magnetic force counter device.
Embodiment
Below in conjunction with accompanying drawing the present invention is described in further detail:
Embodiment:
A kind of NMR device based on laser atomic magnetic force meter; Comprise caesium atomic vapour bubble 7, comprise the magnetic shielding sleeve 5 that is set on the caesium atomic vapour bubble 7, be arranged on three groups of Helmholtz coilss 6 in the magnetic shielding sleeve 5, in the caesium atomic vapour bubble 7 that is used to polarize the caesium atoms the laser-polarization device, be used for to caesium atomic vapour bubble 7 emission detection laser laser beam emitting device, be used to detect the NMR signal supervisory instrument of the exploring laser light that passes caesium atomic vapour bubble 7 and be used for sample is polarized in advance and can the sample after polarizing in advance be placed into the pneumatic sampling device of caesium atomic vapour bubble 7 tops.
The laser-polarization device comprises that optically pumped laser 2 converts the laser that optically pumped laser 2 sends into be sent to caesium atomic vapour bubble 7 behind the circularly polarized light quarter-wave plate 4 with being used for.
Laser beam emitting device comprises that detecting laser 1 converts the laser that detecting laser 1 sends to be sent to caesium atomic vapour bubble 7 behind the linear polarization exploring laser light polarizing prism 3 with being used for.
The NMR signal supervisory instrument comprises the polarization beam splitter prism 8 that is used for the linear polarization exploring laser light that passes caesium atomic vapour bubble 7 is carried out beam splitting; Be used to detect the linear polarization exploring laser light after the beam splitting and detection signal sent to the photodetector 9 of multiplier 10; Be used to adjust the output frequency of optically pumped laser 2 and export the signal generator 11 of square wave synchronizing signal to multiplier 10; The multiplier 10 that is used for detection signal and square wave synchronizing signal are carried out multiplying carries out filtering and is sent to the low-pass filter 12 of host computer 13 output of multiplier 10 with being used for.
Pneumatic sampling device comprises cylinder 18, be arranged in the cylinder 18 and an end is provided with the sample hose 17 of the piston of fitting with cylinder 18 inwalls, the annular polarized magnets 19 and be used to control sample hose 17 reciprocating drive unit in cylinder 18 in advance that is set in cylinder 18 1 ends; Offer through hole on the described magnetic shielding sleeve 5, cylinder 18 1 ends pass through hole and are arranged on caesium atomic vapour bubble 7 tops.
Cylinder 18 1 ends are arranged with guiding coil 20, and the other end is arranged with low-angle pulsed coil 21, and described drive unit comprises the air compressor 14 that pneumatic supply is provided and is used to switch the solenoid valve 15 that air compressor 14 is input to the airflow direction of cylinder 18.
Three groups of Helmholtz coilss 6 comprise the Helmholtz coils of three pairs of annulars; The central lines of every pair of Helmholtz coils; The center line of three pairs of Helmholtz coilss is vertical each other, and wherein the center line of a pair of Helmholtz coils is parallel with the beam direction of exploring laser light.
The measuring method of a kind of NMR based on laser atomic magnetic force meter may further comprise the steps:
Step 1, control caesium atomic vapour bubble 7 temperature rise to 20-60 ℃; The output laser frequency of control optically pumped laser 2 and alkaline metal caesium atom D1 line transition F=4-F '=3 resonance; And the output laser frequency of control detecting laser 1 departs from this resonant frequency 100MHz ~ 100GHz; Electric current to optically pumped laser 2 is modulated, and realizes the synchronizable optical pumping;
The angle of step 2, adjustment polarizing prism 3 and quarter-wave plate 4 obtains linear polarization exploring laser light and circularly polarized light;
The angle of step 3, adjustment polarization beam splitter prism 8, the signal of exporting until photodetector 9 is zero;
Step 4, through the electric current of three groups of Helmholtz coilss 6 of adjustment, make residual magnetic fields in the magnetic shielding sleeve 5 for minimum, obtain the adjustment electric current of three groups of Helmholtz coilss 6;
Electric current in center line in step 5, the three groups of Helmholtz coilss of the scanning a pair of Helmholtz coils parallel with exploring laser light; The positive current values that equates with the negative current magnitude of setting from negative current magnitude to an absolute value of setting; Be superimposed upon on the adjustment electric current described in the step 4, obtain the magnetic field distinguishing signal of low-pass filter 12 outputs;
Step 6, repeating step 2 ~ step 5 are when the unit changes of magnetic field, and the changing value of low-pass filter 12 output voltages response is maximum, and the B value of setting range of linearity center, magnetic field is a bias magnetic field;
Step 7, get the appropriate amount of fluid sample and pour sample hose 17 into, put into cylinder 18;
Step 8, host computer 13 be through relay 16 control electromagnetic valve 15, and then control air compressor 14 is blown into the direction in the cylinder 18, makes sample hose 17 float to the inside center of the preparatory polarized magnets 19 of annular;
Step 9, maintenance sample hose 17 suspension setting-up times; Make its polarization fully in advance, host computer 13 is through relay 16 control electromagnetic valve 15, and then change air compressor 14 is blown into the direction in the cylinder 18; Make sample hose 17 be passed down through guiding coil 20, arrive the top of caesium atomic vapour bubble 7;
Electric current in step 10, the control low-angle pulsed coil 21 produces direct current or alternating-current pulse, changes the sample magnetic moment direction;
There is the little angle of 5 ~ 15 degree in the direction of step 11, sample magnetic moment and bias magnetic field, and the sample magnetic moment is done precession physically receiving the effect of a moment around bias magnetic field, and magnetic field is applied disturbance, obtains the NMR signal of time domain;
Step 12, the NMR signal through time domain obtain the NMR spectrum signal of frequency field.
The present invention is a kind of through polarization in advance in tesla magnetic field, uses laser atomic magnetic force meter to detect, and obtains liquid NMR spectrum in the tesla magnetic field receiving, thereby detects the method and apparatus of NMR signal.Because the sensitivity and the frequency-independent of laser atomic magnetic force meter through in extremely low magnetic field, detecting NMR, can increase the resolution of SNR and spectrum simultaneously, even for very uneven magnetic field, the NMR spectral line is also enough narrow.
The present invention works in the ultralow magnetic fields and detects, and is about 100uT ~ 1nT usually, and uses 0.1T to polarize in advance to the magnetic field of 2T, and sample volume is very little, from 1cm 3Magnitude is to 1mm 3Magnitude.Pick-up unit can be designed to a kind of miniature laser atomic magnetic force meter, is that detection probe can be very near the sample under the room temperature.
Laser atomic magnetic force meter uses the caesium atom as probe bubble actuating medium, and it works near room temperature (20 ~ 60 ℃), and is therefore very little to the influence of chemistry or biological sample because probe and sample to be detected spatially have distance, can ignore.Therefore; Sample can lean on very closely with laser atomic magnetic force meter probe, and the probe of general laser atomic magnetic force meter can be accomplished the 1cm size, and sample and probe distance can arrive 1cm; To accomplish the 1mm size as the atomic vapour bubble of probe if utilize micro-processing technology; Then this distance also can narrow down to 1mm, with the coupling effect that improves sample magnetic field and laser atomic magnetic force meter probe, improves the detection sensitivity of NMR signal.Simultaneously, the sensitivity of laser atomic magnetic force meter and the frequency-independent of signal to be detected can be that several Hz detect it during to hundreds of Hz in Larmor frequency.The magnetic field corresponding with this magnitude Larmor frequency is only in the 1mT level, even the relative homogeneity in this magnetic field (as 1 ‰ ~ 1%) is far below the homogeneity (10 of traditional NMR superconducting magnet -8~10 -6), the NMR signal live width of being obtained is also very narrow, near the intrinsic linewidth of nuclear spin resonance.Nuclear chemical shift information can not show in low, have only the scalar coupling irrelevant with magnetic field (like the J coupling etc.) information to stay, and these information can provide the characteristic parameter of covalent bond.In a word, the present invention can realize a kind of " key detecting device " that simply utilizes laser atomic magnetic force meter, in the magnetic field of 100uT to 1nT, produces the precise information of relevant heteronuclear scalar coupling.
The existing relevant programme that partly proposes with background content is different, and the present invention uses a kind of new actuating medium, utilizes its physical characteristics; The probe working temperature of laser atomic magnetic force meter is reduced greatly; Near room temperature, thereby eliminate the spectral line broadening effect to NMR sample to be detected, this working temperature and human body temperature are approaching in addition; Be expected to be used for living body biological and use, like human body surface or organ imaging etc.
Present invention includes the two large divisions: a non-linear magneto-optical rotation (Nonlinear magnetic-optical rotation who is based on laser and the generation of alkaline metal caesium (Cs) atomic interaction; NMOR) the highly sensitive laser atomic magnetic force counter device part that is made of phenomenon, one is the preparatory polarization and the pneumatic sampling device of sample; Respectively these two devices are carried out the explanation of operation steps below.
Apparatus of the present invention are by detecting laser 1 and optically pumped laser 2; Polarizing prism 3 and quarter-wave plate 4; Magnetic shielding sleeve 5 and three groups of Helmholtz coilss 6; Caesium atomic vapour bubble 7; Polarization beam splitter prism 8 and photodetector 9; Multiplier 10 and signal generator 11; Low-pass filter 12 and host computer 13; Air compressor 14; Solenoid valve 15 and relay 16; Sample hose 17 and cylinder 18; Annular is polarized magnets (Nd-Fe-B permanent magnet) 19 in advance; Guiding coil 20 is formed with low-angle pulsed coil 21.Optically pumped laser 2 is through after the quarter-wave plate 4, with atom effect in the caesium atomic vapour bubble 7 it polarized, and signal generator 11 sine wave output signals are modulated its output frequency to optically pumped laser 2; Magnetic shielding sleeve 5 is that it is wrapped up in the center with caesium atomic vapour bubble 7, and the remnant field of 1nT level is provided, three groups of Helmholtz coilss 6 with add the current source that resistance forms by dry cell and link to each other, produce the remnant field of field compensation magnetic shielding; Detecting laser 1 produces laser and acts on it through getting into caesium atomic vapour bubble 7 after the polarizing prism 3; The transmitted light that passes vapour bubble arrives polarization beam splitter prism 8; Shone after the beam splitting above the photodetector 9, produce output current through photoelectric effect and flow into multiplier 10, carried out multiplying with the synchronizing signal of coming automatic signal generator 11; Output to low-pass filter 12, produce desired signal by host computer 13 records.Sample polarization in advance keeps electrical isolation with pneumatic sampling device and laser atomic magnetic force counter device; But sample hose can arrive the top of caesium atomic vapour bubble 7 via pneumatic sampling device, and the sample magnetic moment Larmor precession signal that produces that polarizes in advance is detected by the induction of laser atomic magnetic force meter.Pneumatic sampling device connected mode is described below: air compressor 14 output gas flows are to solenoid valve 15; Host computer 13 pilot relays 16 are connected with solenoid valve 15 and make it switch the different working state, thereby the flow direction of air-flow in five two-way electromagnetic valves switched; The air-flow that comes out from solenoid valve arrives cylinder 18 through tracheae; Air-flow promotes sample hose 17 and in cylinder, moves up and down; There is a preparatory polarized magnets of annular (Nd-Fe-B permanent magnet) 19 the cylinder top; Sample by its in advance the polarization back under air-flow promotes, move downward reach caesium atomic vapour bubble 7 above about 1cm, its magnetic moment precession signal is surveyed.
A is sample polarization and pneumatic sampling device in advance among Fig. 1, and b is a laser atomic magnetic force counter device; Cylinder among a (18 among Fig. 3) is made up of two plexi-glass tubulars that are about 1m, the about 20mm of outer tube diameter wherein, and the about 15mm of diameter of inner pipe, very thin thickness is ignored.On magnetic shielding sleeve (5 among Fig. 2) wall of laser atomic magnetic force counter device b, beat the hole of external diameter 20mm; Make the cylinder of pneumatic sampling device can pass this hole; The bottom can be adjacent with the probe 7 of laser atomic magnetic force meter, and about 10mm can make laser atomic magnetic force meter probe fully interact with sample magnetic field like this; Make fill factor, curve factor maximum, even also the overall sensitivity of laser atomic magnetic force meter detection NMR signal is the highest.

Claims (8)

1. NMR device based on laser atomic magnetic force meter; Comprise caesium atomic vapour bubble (7), it is characterized in that: comprise the magnetic shielding sleeve (5) that is set on the caesium atomic vapour bubble (7), be arranged on three groups of Helmholtz coilss (6) in the magnetic shielding sleeve (5), the laser-polarization device of interior the caesium atom of caesium atomic vapour bubble (7) that is used to polarize, be used for laser beam emitting device to caesium atomic vapour bubble (7) emission detection laser, the NMR signal supervisory instrument that is used for detecting the exploring laser light that passes caesium atomic vapour bubble (7) polarizes in advance and can the sample after polarizing in advance be placed into the pneumatic sampling device above the caesium atomic vapour bubble (7) sample with being used for.
2. a kind of NMR device based on laser atomic magnetic force meter according to claim 1 is characterized in that: described laser-polarization device comprises optically pumped laser (2) and is used for converting the laser that optically pumped laser (2) sends into be sent to caesium atomic vapour bubble (7) behind the circularly polarized light quarter-wave plate (4).
3. a kind of NMR device based on laser atomic magnetic force meter according to claim 1 is characterized in that: described laser beam emitting device comprises detecting laser (1) and is used for converting the laser that detecting laser (1) sends to be sent to caesium atomic vapour bubble (7) behind the linear polarization exploring laser light polarizing prism (3).
4. a kind of NMR device based on laser atomic magnetic force meter according to claim 2 is characterized in that: described NMR signal supervisory instrument comprise be used for to the linear polarization exploring laser light that passes caesium atomic vapour bubble (7) carry out beam splitting polarization beam splitter prism (8), be used to detect after the beam splitting the linear polarization exploring laser light and with detection signal send to multiplier (10) photodetector (9), be used to adjust the output frequency of optically pumped laser (2) and export the square wave synchronizing signal to the signal generator (11) of multiplier (10), be used for detection signal and square wave synchronizing signal are carried out the multiplier (10) of multiplying and be used for the output of multiplier (10) is carried out filtering and is sent to the low-pass filter (12) of host computer (13).
5. a kind of NMR device according to claim 1 based on laser atomic magnetic force meter; It is characterized in that: described pneumatic sampling device comprises cylinder (18), be arranged in the cylinder (18) and an end is provided with the sample hose (17) of the piston of fitting with cylinder (18) inwall, the annular polarized magnets (19) and be used to control sample hose (17) reciprocating drive unit in cylinder (18) in advance that is set in cylinder (18) one ends; Offer through hole on the described magnetic shielding sleeve (5), cylinder (18) one ends pass through hole and are arranged on caesium atomic vapour bubble (7) top.
6. a kind of NMR device according to claim 5 based on laser atomic magnetic force meter; It is characterized in that: described cylinder (18) one ends are arranged with guiding coil (20); The other end is arranged with low-angle pulsed coil (21), and described drive unit comprises the air compressor (14) that pneumatic supply is provided and is used to switch the solenoid valve (15) that air compressor (14) is input to the airflow direction of cylinder (18).
7. a kind of NMR device according to claim 1 based on laser atomic magnetic force meter; It is characterized in that: described three groups of Helmholtz coilss (6) comprise the Helmholtz coils of three pairs of annulars; The central lines of every pair of Helmholtz coils; The center line of three pairs of Helmholtz coilss is vertical each other, and wherein the center line of a pair of Helmholtz coils is parallel with the beam direction of exploring laser light.
8. the measuring method based on the NMR of laser atomic magnetic force meter is characterized in that, may further comprise the steps:
Step 1, control caesium atomic vapour bubble (7) temperature rise to 20-60 ℃; The output laser frequency of control optically pumped laser (2) and alkaline metal caesium atom D1 line transition F=4-F '=3 resonance; And the output laser frequency of control detecting laser (1) departs from this resonant frequency 100MHz ~ 100GHz; Electric current to optically pumped laser (2) is modulated, and realizes the synchronizable optical pumping;
The angle of step 2, adjustment polarizing prism (3) and quarter-wave plate (4) obtains linear polarization exploring laser light and circularly polarized light;
The angle of step 3, adjustment polarization beam splitter prism (8), the signal of exporting until photodetector (9) is zero;
Step 4, through the electric current of three groups of Helmholtz coilss of adjustment (6), make residual magnetic field in the magnetic shielding sleeve (5) for minimum, obtain the adjustment electric current of three groups of Helmholtz coilss (6);
Electric current in center line in step 5, the three groups of Helmholtz coilss of the scanning a pair of Helmholtz coils parallel with exploring laser light; The positive current values that equates with the negative current magnitude of setting from negative current magnitude to an absolute value of setting; Be superimposed upon on the adjustment electric current described in the step 4, obtain the magnetic field distinguishing signal of low-pass filter (12) output;
Step 6, repeating step 2 ~ step 5 are when the unit changes of magnetic field, and the changing value of low-pass filter (12) output voltage response is maximum, and the B value of setting range of linearity center, magnetic field is a bias magnetic field;
Step 7, get the appropriate amount of fluid sample and pour sample hose (17) into, put into cylinder (18);
Step 8, host computer (13) be through relay (16) control electromagnetic valve (15), and then control air compressor (14) is blown into the direction in the cylinder (18), makes sample hose (17) float to the inside center of the preparatory polarized magnets of annular (19);
Step 9, maintenance sample hose (17) suspension setting-up time; Make its polarization fully in advance; Host computer (13) is through relay (16) control electromagnetic valve (15); And then change air compressor (14) and be blown into the direction in the cylinder (18), make sample hose (17) be passed down through guiding coil (20), arrive the top of caesium atomic vapour bubble (7);
Electric current in step 10, the control low-angle pulsed coil (21) produces direct current or alternating-current pulse, changes the sample magnetic moment direction;
There is the little angle of 5 ~ 15 degree in the direction of step 11, sample magnetic moment and bias magnetic field, and the sample magnetic moment is done precession physically receiving the effect of a moment around bias magnetic field, and magnetic field is applied disturbance, obtains the NMR signal of time domain;
Step 12, the NMR signal through time domain obtain the NMR spectrum signal of frequency field.
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