CN1011352B - Tracking helium (he4) optical pump megnetic instrument - Google Patents
Tracking helium (he4) optical pump megnetic instrumentInfo
- Publication number
- CN1011352B CN1011352B CN 88100010 CN88100010A CN1011352B CN 1011352 B CN1011352 B CN 1011352B CN 88100010 CN88100010 CN 88100010 CN 88100010 A CN88100010 A CN 88100010A CN 1011352 B CN1011352 B CN 1011352B
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- Prior art keywords
- frequency
- magnetic field
- tracking
- helium
- absorption chamber
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Abstract
The present invention relates to a tracking helium (He4) optical pump magnetometer for detecting the change of the geomagnetic field. The main points comprise: 1. a high-frequency pumping system in a probe, a helium lamp and the magnetic field system in an absorbing chamber are newly designed to enhance a signal/noise ratio and the sensitivity of the instrument. 2. Via a double frequency signal in error signals, an automatic control circuit is arranged for rapidly tracking the change of an external magnetic field. 3. A self high order locking frequency multiplier is arranged in a tracking loop circuit, so that a frequency multiplying circuit is simplified to enhance the reliability and the display sensitivity of the circuit. 4. The display sensitivity of the present invention is 0.02nT for 0.5 second sampling and 0.01nT for 1 second sampling.
Description
The present invention is a kind of instrument that the magnetic field of the earth changes that detects.
It is that Karst drew (Kastlar) to put forward (" Optical methode of atomic orcentation and of magnetic resonance " J.opti in 1956 that " optical pumping " technology of utilization constitutes magnetometer, soc, Am, 47,4.60-4.65).
According to this principle, Texas ,Usa (Texas) instrument company made tracking helium (He in 1967
4) optically pumped magnetometer.（A.R.Keyser，J.A.Rice，L.D.Schearer“Ametastable Helium magnetometer for observing small geomagnetic fluctuations”）。From designing summary (Bernard Kovit " Ulra-Precise magnetometer for underser or spece " DESIGN DIGEST 1961) its basic functional principle as can be known.
By the probe that high frequency power source, helium lamp, convex lens, circular polarizing disk, the absorption chamber that is wound with resonance coil and photoelectric detector are formed, be to produce optical action, the parts of error signal are provided.The height of its signal to noise ratio is the key point of decision instrumental sensitivity.
Formed track loop by resonance coil (rf magnetic field coil), absorption chamber, photoelectric detector, phase-sensitive detector (PSD) and voltage controlled oscillator.Instrument is entered from motion tracking, and probe must be exported the fundamental frequency error signal (modulating frequency) with certain amplitude.Because near tracing area, the relation of fundamental frequency error signal and external magnetic field as Fig. 11 shown in.Exceeded the normal tracing area 3 of magnetic resonance in case work as the variation of external magnetic field, the fundamental frequency error signal can not normally follow the tracks of instrument with regard to becoming very little.This will be unconformable to the system that need carry out continuous coverage and sampling with very fast speed.By following principle as can be known, tested magnetic field value Hr can be that Larmor frequency (Larmar) is represented with the resonant frequency fr under the tracking mode, and the display sensitivity S that the rapid pulse of using tricks is brought expression is determined by formula (1):
S＝ 2/(rpmT) （1）
Rp is helium (He in the formula
4) gyromagnetic ratio of optically pumped magnetometer, about 28Hz/nT.
M carries out the frequency of frequency multiplication for improving display sensitivity to resonant frequency fr.
T is the cycle (second) of each sampling.
Be in quick sampling, to improve the display sensitivity of instrument, need to resonant frequency fr carry out high order frequency (Jap.P. clear and-enter counter again after 55-151275).This method is higher and need under the bigger situation of variation range in frequency, and its circuit is that more complicated and reliability are not high.
Based on above-mentioned tracking helium (He
4) principle and the prior art of optically pumped magnetometer, the invention provides a kind of tracking helium (He
4) optically pumped magnetometer, its purpose is:
(1) for improving the sensitivity of instrument as far as possible, new design has been proposed for radio-frequency (RF) magnetic field and modulated magnetic field around the high frequency pumping system in the probe, helium lamp, the absorption chamber, from the signal to noise ratio that improves probe to improve the sensitivity of instrument.
(2) utilize 2 among characteristics that the two frequency multiplication error signal amplitudes that exist in the error signal change such as Fig. 1, the automatic control that can have quick tracking when big external magnetic field rate of change, the circuit that prevents missing ability are provided.
(3) utilize track loop self that the frequency of radio frequency resonant field has been carried out high order locking frequency multiplication, to improve by the display sensitivity of measuring magnetic field.
The present invention is according to above-mentioned 3 the tracking helium (He that provide
4) optically pumped magnetometer, the probe and the track loop system that are made up of high frequency power excitation system (4-9), optical system (10-19), absorption chamber field system (18,19) are formed.As shown in Figures 2 and 3.
High frequency oscillator 4 produces HF voltage, supplies power amplifier 6 to improve output power through transformer 5, passes to resonant tank 8 by transformer 7 outputs through transmission cable again and excites absorption chamber 14 with excitation helium lamp 10 and with exciting electrode 9.
The light that sends 1.083 μ m after helium lamp 10 is energized forms directional light through convex lens 11, becomes circularly polarized light by polaroid 12 and 1/4 wavelength sheet 13, and the effect that this light is incident upon absorption chamber 14 outside magnetic field Hr produces optical action down.Be wound with coil 18 that radio-frequency (RF) magnetic field is provided and the magnetic field that the coil 19 that produces modulated magnetic field is produced around the absorption chamber 14 and produce magnetic resonance with it in absorption chamber 14.Magnetic resonance makes by the light of absorption chamber 14 the most weak.This light focuses on photosensitive device 16 through convex lens 15 and produces the photocurrent of band modulation.This photocurrent amplifies and enters through transmission cable 20 the fundamental frequency error signal frequency-selecting amplifier 21 of apparatus subject promptly with modulated Field frequency output error signal through prime amplifier 17.Fundamental frequency error signal after frequency-selecting is amplified produces direct-current control voltage in phase sensitive detector 22 demodulation detections, the oscillation frequency fv of this voltage control voltage controlled oscillator 24 behind the noise of controllable filter 23 inhibition upper frequencies, this frequency is counted to show the intensity level Hr of external magnetic field for counter.This frequency is put frequency divider 25 frequency divisions m time through giving in addition, obtain the Larmor frequency that frequency is fr (fr=fv/m), supply with rf magnetic field coil 18, thereby formed track loop, make voltage controlled oscillator 24, the frequency that provides can be from the variation of motion tracking external magnetic field Hr.
The signal of prime amplifier 17 output is except that the fundamental frequency error signal of modulating frequency, also with two frequency multiplication error signals of modulating frequency.After it enters apparatus subject, remove to control controlled loop filter 23 through two frequency multiplication error signal frequency-selecting amplifiers, 26, two frequency multiplication error signal amplitude Discr.s 27 and triggering controller 28.
Modulating signal generator 29 provides the modulation signal.
Characteristics of the present invention are:
(1) helium lamp 10 is light sources that absorption chamber 14 produces optical action in the optical system.For making it to form the strong pump spectrum light that is similar to pointolite, helium lamp 10 of the present invention is the tubbiness dumbbell shaped, and two end diameter is 14-20mm, and neck length is 3-7mm, and neck slightly is not more than 5mm.This form is subject to high frequency power most and excites, so can obtain the light intensity of needs under lower exciting power, helium lamp 10 of the present invention generally bar-shaped or dumbbell shaped helium lamp can reduce by 30% exciting power at least.This has just effectively reduced noise, has improved the signal to noise ratio of probe.
(2) produce magnetic resonance equably along length in the absorption chamber 14 and obtain higher signal to noise ratio for making, rf magnetic field coil 18 and modulated magnetic field coil 19 that the absorption chamber field system is made up of last of the twelve Earthly Branches nurse hertz (Helmholtz) coil are separate mutually orthogonal again.The central point of these two groups of coils overlaps with the central point of absorption chamber 14, obtains uniform magnetic field and improves signal to noise ratio around making absorption chamber 14.
(3) provide through giving the resonance signal of putting frequency divider 25 frequency divisions by voltage controlled oscillator 24 and be added on the rf magnetic field coil 18, when this signal is more weak, resonance zone 3 narrows down, this is favourable to improving signal to noise ratio, but because the reducing and signal to noise ratio is descended of its signal strength, vice versa, therefore the necessary suitably intensity of selective reaonance signal, in the hope of obtaining best signal to noise ratio, same, the size of modulated magnetic field also directly influences the resonance zone width 3 and the strength of resonance.So there is an optimal proportion between the two magnetic field.The present invention is designed to form in absorption chamber 14 zones the radio-frequency (RF) magnetic field of 150-200nT, and the strength ratio of radio-frequency (RF) magnetic field and modulated magnetic field is 1: (0.6-1.2).
(4) high frequency oscillator 4 adopts the high stable oscillator, and to improve stability of light source, its oscillation frequency is 15-60MHZ, is 3-5W through power amplifier 6 output powers.
Because helium lamp 10 and absorption chamber 14 all belong to high impedance load, and its impedance is relevant with multiple factor again, so the transformer 5 that power delivery is used and 7 adopts the wideband transmit transformer to improve adaptive faculty.Resonant tank is tuned near the oscillation frequency of high frequency oscillator 4, realizes the coupling of impedance and high Q value.
Exciting electrode 9 is the plate electrode that a pair of its length is formed greater than the rectangle copper sheet of absorption chamber 14 length, makes it to form uniform high frequency pumping electric field in the zone of absorption chamber 14, to increase magnetic resonance signals intensity.
Has high signal to noise ratio according to above 4 probes of making.
(5) find out fundamental frequency error signal 1 and the amplitude of two frequency multiplication error signals 2 and the relation of external magnetic field near tracing area 3 by shown in Figure 1.By following principle as can be known, have only when 1 existence of fundamental frequency error signal, and when satisfying certain amplitude, instrument just can be followed the tracks of normally, and two frequency multiplication error signals 2 are to be suppressed by fundamental frequency error signal frequency-selecting amplifier 21 as useless signal in track loop.From Fig. 1 also as can be known, when external magnetic field changes when exceeding normal tracing area 3, fundamental frequency error signal 1 can not normally follow the tracks of instrument with regard to diminishing rapidly, and meanwhile, two frequency multiplication error signals 2 also become very little.
The present invention utilizes near the variation characteristic of this two frequencys multiplication error signal 2 amplitude tracing area 3, provides one to follow the tracks of the automatic control circuit that external magnetic field changes fast.Form by two frequency multiplication error signal frequency-selecting amplifiers, 26, two frequency multiplication error signal amplitude Discr.s 27, triggering controller 28 and controlled loop filter 23.In tracing area 3, two frequency multiplication error signals, 2 amplitudes are bigger, are higher than the threshold voltage that amplitude Discr. 27 is set, and trigger controller 28 outputs one controlling signal this moment, controlled loop filter 23 is under the normal design point works.In case the variation of external magnetic field exceeds normal tracing area 3 suddenly, the fundamental frequency error signal becomes very little, and instrument can not be followed the tracks of normally.Meanwhile, the amplitude of two frequency multiplication error signals 2 also descends, when its amplitude is lower than the threshold voltage that amplitude Discr. 27 sets, trigger controller 28 another controlling signal of output, the bandwidth that makes controlled loop filter 23 immediately broadening (broadening of controlled loop filter 23 bandwidth is wanted the signal to noise ratio of lowering apparatus, and sensitivity is descended), quickened the control rate of voltage controlled oscillator 24, thereby made instrument be in tracking mode again immediately.When in case instrument enters tracing area 3, two frequency multiplication error signals, 2 amplitudes will be higher than the threshold voltage that amplitude Discr. 27 is set again, send a controlling signal again so trigger controller 28, controlled loop filter 23 is returned to again under the normal design point work, keep original signal to noise ratio of instrument and sensitivity.
In geophysical survey of aviation, run into big changes of magnetic field, adopt fast automatic tracking of the present invention system will make instrument obtain effectively tracking power fast through regular meeting.
(6) as seen from formula (1), obtain high display sensitivity S, need carry out high order frequency resonant frequency fr.
The present invention is different with the method for prior art frequency multiplication beyond loop, but is provided with loop self high order locking frequency multiplication in track loop, and it is to have set up to give in track loop to put frequency divider 25.The oscillation frequency fv that has improved m voltage controlled oscillator 24 doubly by give put m frequency division of frequency divider after, obtain the radioresonance coil 18 that needed resonant frequency fr is fed to probe.Can give the divider ratio m that puts frequency divider is 2-16 or higher.At this moment, m the frequency multiplication of using for rolling counters forward that promptly equals resonant frequency fr from the frequency f v of voltage controlled oscillator 24 outputs.This method had both been simplified frequency multiplier circuit, had improved the reliability of frequency multiplier again.
Description of drawings of the present invention:
Near Fig. 1: the relation curve that tracking error signal therein and two frequency multiplication error signal amplitudes change with external magnetic field normal tracing area
1-error signal amplitude curve
2-two frequency multiplication error signal amplitude curves
The normal tracing area of 3-
Fig. 2: the high frequency pumping system chart among the embodiment
The 4-high frequency oscillator
The 5-transformer
The 6-power amplifier
The 7-transformer
The 8-resonant tank
9-absorption chamber exciting electrode
The circuit block diagram of Fig. 3: embodiment
(4-9)-the high frequency pumping system
The 10-helium lamp
The 11-convex lens
The 12-circular polarizing disk
13-1/4 wavelength sheet
The 14-absorption chamber
The 15-convex lens
The 16-photosensitive device
The 17-prime amplifier
The 18-rf magnetic field coil
19-modulated magnetic field coil
The 20-transmission cable
21-fundamental frequency error signal frequency-selecting amplifier
The 22-phase-sensitive detector (PSD)
The controlled loop filter of 23-
The 24-voltage controlled oscillator
25-can give and put frequency divider
26-two frequency multiplication error signal frequency-selecting amplifiers
27-two frequency multiplication error signal amplitude Discr.s
28-triggers controller
29-modulating signal source
Fig. 4: HC-85 type aviation tracking helium optically pumped magnetometer external form photo of the invention process
(comprising probe, transmission cable and apparatus subject)
HC-85 aviation tracking helium optically pumped magnetometer of the invention process, its main design parameters is:
(1) oscillation frequency of high frequency oscillator 4 is 25MHz
(2) output power of power amplifier 6 is 4W
(3) neck length of helium lamp 10 is 6mm, and neck slightly is not more than 5mm, and end diameter is 16mm.
(4) rf magnetic field coil 18 is 1: 0.9 at the ratio of the formed magnetic field intensity in absorption chamber 14 centers
(5) can give the divider ratio m=4 that puts frequency divider 24
Instrument characteristics according to above-mentioned design are:
（1）
Four differential noises of sampling time display sensitivity
0.5 second 0.02nT 0.01nT
1 second 0.01nT 0.008nT
When (2) the outside magnetic field rate of change reached 1000nT/S, instrument can reliably be followed the tracks of
(3) instrument normal operation region 200nT
(4) measuring the terrestrial magnetic field scope is 35000-75000nT
(5) weight:
Main frame: 4Kg
Probe: 1Kg
Cable: 4Kg/20m
6, power consumption: 28v1A
Claims (4)
1, a kind of tracking helium (He
4) optically pumped magnetometer, formed by probe, track loop system and counting output system that high frequency power excitation system, optical system, absorption chamber field system are formed, it is characterized in that:
(1) helium lamp (10) is the tubbiness dumbbell shaped in the optical system, and its two end diameter are 14-20mm, and neck length is 3-7mm, and neck slightly is not more than 5mm;
(2) the absorption chamber field system is formed rf magnetic field coil (18) and modulated magnetic field coil (19) by two independent mutually helmholtz coils of mutually orthogonal again, its central point all overlaps with the center of absorption chamber (14), and rf magnetic field coil (18) and modulated magnetic field coil (19) are 1 at the magnetic field intensity ratio that absorption chamber forms: (0.6-1.2);
(3) the high frequency power excitation system is made up of high frequency oscillator (4), transformer (5 and 7), power amplifier (6), resonant tank (8) and absorption chamber exciting electrode (9), and its oscillation frequency is 15-60MHz;
(4) track loop is provided with that quick tracking external magnetic field changes, by two frequency multiplication error signal frequency-selecting amplifiers (26), two frequency multiplication error signal amplitude Discr.s (27), trigger the automatic control circuit that controller (28) and controlled loop filter (23) are formed;
(5) track loop is provided with by giving and puts loop self the high order locking frequency multiplier circuit that frequency divider (25) is formed, and it can give the divider ratio m that puts frequency divider is 2-16 or higher.
2, according to the said tracking helium (He of claim (1)
4) optically pumped magnetometer, it is characterized in that transformer (5) and (7) in the high frequency pumping system are the broadband transmission transformers.
3, according to the said tracking helium (He of claim 1
4) optically pumped magnetometer, it is characterized in that resonant tank (8) is tuned near the oscillation frequency point of high frequency oscillator (4).
4, according to the said tracking helium (He of claim 1
4) optically pumped magnetometer, it is characterized in that the plate electrode that absorption chamber exciting electrode (9) is formed greater than the rectangle copper sheet of absorption chamber (14) length for a pair of its length.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 88100010 CN1011352B (en) | 1988-01-05 | 1988-01-05 | Tracking helium (he4) optical pump megnetic instrument |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 88100010 CN1011352B (en) | 1988-01-05 | 1988-01-05 | Tracking helium (he4) optical pump megnetic instrument |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1034069A CN1034069A (en) | 1989-07-19 |
| CN1011352B true CN1011352B (en) | 1991-01-23 |
Family
ID=4831117
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 88100010 Expired CN1011352B (en) | 1988-01-05 | 1988-01-05 | Tracking helium (he4) optical pump megnetic instrument |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1011352B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103869267A (en) * | 2012-12-12 | 2014-06-18 | 上海精密计量测试研究所 | Optical pumping magnetic measuring device |
| CN103257329B (en) * | 2013-04-27 | 2015-06-24 | 西安电子科大赛福电子技术有限责任公司 | Helium light pump gradient detector and method for achieving high-sensitivity gradient detection |
| CN103823245B (en) * | 2013-12-27 | 2017-03-01 | 杭州瑞声海洋仪器有限公司 | Omnidirectional's helium light pump magnetic apparatus |
| US9964604B2 (en) * | 2014-11-12 | 2018-05-08 | Seiko Epson Corporation | Magnetic field measurement method and magnetic field measurement device for measuring and offsetting original magnetic field |
| CN105866716B (en) * | 2016-06-23 | 2018-08-10 | 梁尚清 | A kind of novel Full-optical laser light pump magnetometer and its implementation |
| CN108562861B (en) * | 2018-03-30 | 2020-10-16 | 上海通用卫星导航有限公司 | Symmetrical cesium optical pump magnetometer for magnetic gradient measurement |
-
1988
- 1988-01-05 CN CN 88100010 patent/CN1011352B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| CN1034069A (en) | 1989-07-19 |
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