CA1164529A - Nuclear magnetic resonance gyro - Google Patents
Nuclear magnetic resonance gyroInfo
- Publication number
- CA1164529A CA1164529A CA000379449A CA379449A CA1164529A CA 1164529 A CA1164529 A CA 1164529A CA 000379449 A CA000379449 A CA 000379449A CA 379449 A CA379449 A CA 379449A CA 1164529 A CA1164529 A CA 1164529A
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- Canada
- Prior art keywords
- nuclear
- cell
- magnetic
- moment
- optically
- Prior art date
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
- G01C19/58—Turn-sensitive devices without moving masses
- G01C19/60—Electronic or nuclear magnetic resonance gyrometers
- G01C19/62—Electronic or nuclear magnetic resonance gyrometers with optical pumping
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Gyroscopes (AREA)
- Measuring Magnetic Variables (AREA)
- Magnetic Resonance Imaging Apparatus (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A nuclear magnetic resonance gyro using two nuclear magnetic resonance gases, preferably xenon 129 and xenon 131, together with two alkaline metal vapors, preferably rubidium and cesium, one of the two alkaline metal vapors being pumped by light which has wavelengths of that alkaline metal vapor, and the other alkaline vapor being illuminated by light which has wavelengths of that other alkaline vapor.
A nuclear magnetic resonance gyro using two nuclear magnetic resonance gases, preferably xenon 129 and xenon 131, together with two alkaline metal vapors, preferably rubidium and cesium, one of the two alkaline metal vapors being pumped by light which has wavelengths of that alkaline metal vapor, and the other alkaline vapor being illuminated by light which has wavelengths of that other alkaline vapor.
Description
29 .~
GCD 80-1 ~
I' NUCLEAR ~GNETIC XESONANCE GYRO f' Cross-Re~erence to a Related Paten _~pplication ....
APPLICATION
'~',' '.
This is an improvement o~ the invention in U. S. Patent . . i.
4,157,495 which issued June 5, 1~79 to Bruce C. Grover, Edward Kanegsberg, John G. Mark and Roger L. Meyer for a Nuclear Magnetic Resonance Gyro, which patent is assigned to Litton Systems, Inc., the assignee of this application.
:-- ; . . . ::
~ - BACKGROUND OF THE INVENTION
~ ' ' - ' ,, ' ' ' ' - .:
~O This invention relates to the creation and detectior. o --nuclear magnetic resonance. More particularly this invention relates to the a~plication of nuclear magnetic resonance in an - angular rate sens~r.
:, . , . . ;:
. .
- A number of approaches have been suggested in the prior 1~ art ~or implementing the basic concept o~ a n~clear magnetic resonance NMR gyroscope. In general, they utiliæe a nuclear magnetic resonance controlled oscillator and derive rotational information from the phases of the nuclear moment Larmor prccession signal~ by means of suitable phase comparison and zo magnetic ~ield control circuitry.
' ,.
.
Page l . , ~
3L6aJ5~9 These devices contain significant deficiencies which limit the development o a useful instrument. For instance, such devices have been lirnited by relatively short relaxation times of the gases which have been employed. Also, the strong direct 5 coupling ~etween these gases and the light which is employed as the means of magnetic moment ali~nmert or magnetic momen~
detection can limit both the relaxation times and the signal-to-noise ratio, and thererore can also limit the potentlal usefulness of such instruments.
In U.S. Patent 4,157,495 a nuclear magnetic resonance (hereinafter referred to as "NMR") angular rate sensor or gyroscope is disclosed that operates on the principle of sensing inertial angular rotation rste os~ sr7~ nt about a sensitive axis of the device as a shl~t in the Larmor precession 15 frequency or phase, respectively, of one or more isotopes that possess nuclear magnetic moments. The gyroscope is composed of an angular rotation sensor and associated electronics. The - -principal elements of the sensor are a light source, an NMR cell, a photodetector, a set of magnetic shields and a set of magnetic 20 field coils. The principal elements of the electronic.s are signal proc~ssing circuits for extracting the Larmor precession frequency and phase information as well as circuits for gen~rating and controlling various magnetic fields, both steady and varying sinusoidally with time, that are necessary for the
GCD 80-1 ~
I' NUCLEAR ~GNETIC XESONANCE GYRO f' Cross-Re~erence to a Related Paten _~pplication ....
APPLICATION
'~',' '.
This is an improvement o~ the invention in U. S. Patent . . i.
4,157,495 which issued June 5, 1~79 to Bruce C. Grover, Edward Kanegsberg, John G. Mark and Roger L. Meyer for a Nuclear Magnetic Resonance Gyro, which patent is assigned to Litton Systems, Inc., the assignee of this application.
:-- ; . . . ::
~ - BACKGROUND OF THE INVENTION
~ ' ' - ' ,, ' ' ' ' - .:
~O This invention relates to the creation and detectior. o --nuclear magnetic resonance. More particularly this invention relates to the a~plication of nuclear magnetic resonance in an - angular rate sens~r.
:, . , . . ;:
. .
- A number of approaches have been suggested in the prior 1~ art ~or implementing the basic concept o~ a n~clear magnetic resonance NMR gyroscope. In general, they utiliæe a nuclear magnetic resonance controlled oscillator and derive rotational information from the phases of the nuclear moment Larmor prccession signal~ by means of suitable phase comparison and zo magnetic ~ield control circuitry.
' ,.
.
Page l . , ~
3L6aJ5~9 These devices contain significant deficiencies which limit the development o a useful instrument. For instance, such devices have been lirnited by relatively short relaxation times of the gases which have been employed. Also, the strong direct 5 coupling ~etween these gases and the light which is employed as the means of magnetic moment ali~nmert or magnetic momen~
detection can limit both the relaxation times and the signal-to-noise ratio, and thererore can also limit the potentlal usefulness of such instruments.
In U.S. Patent 4,157,495 a nuclear magnetic resonance (hereinafter referred to as "NMR") angular rate sensor or gyroscope is disclosed that operates on the principle of sensing inertial angular rotation rste os~ sr7~ nt about a sensitive axis of the device as a shl~t in the Larmor precession 15 frequency or phase, respectively, of one or more isotopes that possess nuclear magnetic moments. The gyroscope is composed of an angular rotation sensor and associated electronics. The - -principal elements of the sensor are a light source, an NMR cell, a photodetector, a set of magnetic shields and a set of magnetic 20 field coils. The principal elements of the electronic.s are signal proc~ssing circuits for extracting the Larmor precession frequency and phase information as well as circuits for gen~rating and controlling various magnetic fields, both steady and varying sinusoidally with time, that are necessary for the
2~proper operation o~ the device.
1 164529 GCD ~0-I
lhe NMR cell is mounted within a set of magnetic shields in order to attenuate external magnetic ~ields to acceptably low levels. Magnetic field coils are used to apply very uni~orm magnetic fields t~ the NMR cell. Both a steady field and an AC
5 carrier field are applied along the sensitive axis oF the device L
and AC feedback fields are applied along one of the transverse axes. The DC magnetic fields along both transverse axes are controlled to be substantially zero. The N~IR cell con~ains a single alkali metal vapor, such as rubidium, together with two 10 isotopes of one or ~ore noble gases, such as krypton-83, and xenon-129, or xenon l31. A buffer gas such as helium may also be contained in the cell.
The NMR cell is illuminated ~y a beam~o~ circularly polarized light that originates from a source such as a rubidium 15 lamp or a rubidium solid state laser and which passes througn the cell at an angle with respect to the steady magnetic fieldc Absorption o~ some o~ this light causes the atomic magnetic ~oments of the rubidium atoms to be partly aligned in the direction of the steady magnetic field. This alignment is partly 20 trans~erred to the nuclear magnetic moments of the noble gases, and these moments are caused to precess about the direction of the steady magnetic field, which in turn creates magnetic fields tha~ rotate at the respective Larmor precession frequencies of the two noble gases. These rotating fields modulate the 25 precessional motions o~ the rubidium magnetic moments, which in 1164529 GCD BO~
turn prodllces corresponding modulations of the transmitted light, therehy making is possible optically to detect the Larrnor precession frequencies of the two noble gases.
. .
The modulations of the light intensity are converted into electrical signals by a photodetector, and these signals are then electronically demodulated and filtered to provide signals-at the Larmor precession frequencies of the two noble gases. The dif~erence between the t~o precession frequencies is used accurately to control the steady magnetic field so that it is constant. One of the noble gas precession frequencies is compared to a precision reference frequency, and the resul~ing difference ~requency is a measure of the angular rotation rate of ~ -the g~roscope~
The two detected noble gas precession signals are also 15 ~sed to generate two AC feedback magnetic ~ields at the Larmor ~ . - . . ...... . . .... . . . .
precession frequencies of the noble gases, and these are responsible for sustaining the precession of the nuclear magnetic moments of the noble gases. The use of an AC carrier magnetic field facilitates the optical detection of the precessing noble 20 gas moments,and it provides means for controlling the DC magnetic fields along the two ~ransverse axes of the gyroscope.
According to ~he patent, the NMR gyroscope includes means for the simul~aneous alignment of ~he nuclear magnetic moments of at least two nuci~ar moment gases, thereby constituting a nuclear 116~529 ~ GCD ~0-l , ma~netic momen~ alignment device; the means for achieving sustained precession of these moments, thereby constituting a nuclear magnetic resonsnce oscillator capable of sustained oscillations, the means for ~he optical detection of these precessing nuclear moments thereby constituting a nuclear magnetic resonance detection device; the ~eans for accurately controlling the internal magnetic field of the device; and the ~ '-means for the accurate measurement of ~he frequency or phase of.
the detected nuclear moment precession signal of at least one of the nuclear moment gases to provide a measurement of the angular rotation rate or angular displacement, respectively, o~ the device with respect to inertial space, thereby constituting an NMR gyroscope~ . .
- ` . ;.
More particularly, a steady magnetic field is applied to an NMR cell which is substantially shielded from other steady magnetic fields The NMR cell contains a gas or vapor of a substance that possesses a magnetic moment that can be aligned by optical p~mping, together with one or more additional gases, each of which possesses a nuclear magnetic moment~ The NMR cell is 1.
illuminated by optical pumping liqnt whicA has a directional component that is parallel to the direction of the steady magnetic field and which has the proper wavelen~th to be absorbed by the optically pumpable substance and partially align the , I .
magnetic momen~s o~ that substance~ The nuclear moments of the 2~ nuclear moMent gases are ca~sed to become aligned and are caused to precess at their respective Larmor precession ~requencies D~ 5 ~ 4 5 2 9 GCD 80-1 about the direction o~ the steady magnetic field. An AC magnetic field at a suitable carrier ~requency is also applied to the NMR
cell, and the cell .is illuminated by detection light ~hich has a directional component that is orthogonal to the c~irection of the AC carrier magnetic field and which has a wavelength that is essentially the s~me as that of the op~icai p~ping light. The intensity of the part of the detection light that is trans~itted ~.
by the cell is modulated in accordance with the totality of the magnetic fields present in the cell, including the magnetic fields that are generated by the precessing nuclear maynetic moments. These modulations of the trans.nitted light intensity are detected by a photodetector, after which they are ; electronically demodulated to obtain signals at the Larmor ~ precession frequencies of the nuclear momen~ gasPsS.-:
.' , 1~ In one embodiment of the patented invention, the alignment of the nuclear magnetic moments of each nuclear moment gas is accomplished by collisional interactions between the atoms of the optically pompable substance and the atoms of the nuclear moment gas or gases. Sustained precession of the nuclear magnetic moments o~ each nuclear moment gas is accomplished by the application of an AC feedback magnetic field at the Larmor precession frequency of the nuclear moment gas in a direction that is ortho~onal to the direction of the steady magnetic field.
The AC carrier magnetic ~ield is applied at substantially the Larmor precession frequency o~ the optically p~npable substance and in a direction that is substantially parallel to the Page 6 .
~ 4 ~ 2 9 ~CD 80-1 , direction of the steady magnetic field, thereby permittiny the device to be operated at higher values of the steady rbagnetic field strength and with correspondingly hi~her Larmor precession frequencies for the nuclear moment gases.
. . , In the preferred embodiment, an optically pumpable substance such as a single alkali metal vapor is placed in an N~lR
cell together wi~h two noble gases, and the nuclear magnetic moments of both noble gases are aligned simultaneously by collisional interactions between the atoms of the sing:le alkaIi ~etal atoms and the atoms of the two noble gases. In this pre~erred embodiment of the invention, the alkali me~al is rubidium and the noble gases are xenon-129 ! and xenon 131.
. Another feature of the patent invo].ves the use of at least one buffer gas in substantial quantities ;.n the NMR cell~.
' ' ' ' - ' In accordance with still another feature of the paten~, the magnitude of the steady magnetic field is ca~sed to remai.n constant by feedback control of the field in such a way that the difference between the Larmor precession frequencies of the two noble yases in the N~lR cell is caused to be equal to a predetermined constant value.
In accordance with yeL another ~eature of the patent, one .
of the Larmor ~recession frequencies is compared to a precision reerence ~requency and the resulting difference ~requency is utilized to provide a measuremen~ of angu:Lar displacement or an~ular rate of the device about the direction of the steady ,, magnetic field. !:
SU~ RY OF T~JE INVENTION
'; - ' ~, It is contemplated b,y this invention to include ~wo rather than one alkali metal vapors within the MMR en~elope. Oné of the vapors, for example rubidium, is used because it is easily excited or pumped by light from a rubidium lamp or a laser at the rubidium wavelength~ The other alkali metal vapor, for example cesium, is easily pumped by a cesium lamp or laser at the cesium ; 15 wavelength. The cesium within the NMR enclosure,is modulated at the Larmor precession frequencies of the two nuclear magnetic moment gases such as xenon 129 and xenon 131. The cesium vapor ;' is illuminated, for example, by a cesium lamp or a laser, and the transmitted cesium radiation is modulated at the Larmor 20 precession frequencies of the two nuclear moment gases. The ', transmitted light is detected, and the detected signals are used in a manner identical to that déscribed in patent 4,157,495.
' ' , It is therefore an object of this invention to provide an N~R gyroscope usin~ one pumpable vapor and a different sensing vapor. The words "different vapor" are defined herein to include di~ferent isotopes o~ the same vapor, particularly where the vapor is an alkali metal vapor.
.
. Page 8 ~CD ~0-l ~
~ ~452~ I~
It is a more specific object of this invention to use two - alkaline vapors in an NilR gyro.
It is still a more speciic object of this invention to use rubidium vapor as a pumping vapor and cesium vapor as a 5 detection vapor in an ~MR gyro which uses two aligned nuclear ,;
moment gases precessing at their Larmor precession frequencies.
. .
- DESC~IPTION OF THE DRAWINGS
The only figure i5 a conceptual diagram illustrating the p~ocesses of optical pumping and of modulation of ~he itensity of the light that is transmitted by the NMR cell.
' " .'.
DETAILED DESC~IPTIG~ E
PREFER~ED E~ODI~
The figure is a conceptual diagram illustrating for each of the noble gases the process of optical p~nping and of modulation of the intensity of the light that is transmitted 5 through the NIIR cell 28. Because these processes are so similar for the two noble gases, they are illustrated and descrihed ~or only one of the two noble gases. The circularly polarized plunping light, ~or example from a laser at the rubidium wavelength, which enters the NMR cell 28 has a component 64 along the z-axis. Through the interactions of the opticai pumping light 64 and the steady magnetic field 68, the rubidium atoms ~0 have their magnetic moments aligned preferentially in the z-direction; ~y interatomic collisions, this magnetic moment ` ~
, - GCD 80-1 ~ 164~29 alignment is transferred rom the rubidium atoms 60 to the noble gas nuclei 62 and to the cesium atoms 61.
' A sinusoidal AC feedback magnetic field 70 that is matched in frequency and phase to the Larmor precession frequency of the coliective magnetic moment of the noble gas nuclei 62 is applied in the x-direction and serves to torque the magnetic moment of these nuclei to the X-y plane. This component of noble gas . ', nuclear magnetic mom~nt then precesses in the x-y plane at the noble gas Larmor precession frequency abou~ the s~eady magnetic field 68. This preces~ing ,nuclear magnetic moment component creates a nuclear precession magnetic field that rotates'in the x-y plane.
, The detection light 66 at cesium wavelength, for example~
from a cesîum l~mp or a laser, interacts ~7ith the cesium atoms 1~ which are under the influence of the steady magnetic field 68, a superimposed AC carrier magnetic field 69, and the y-component of the nucle~r precession field. This interaction causes the intensity of the x-component of the transmitted cesium light 72 - to be modulated at the carrier frequency, with a modulation 20 envelope 7~ at the nuclear precession frequency, These llght modùlations are then converted into electrical signals by the photodetector 40. The electrical signals may be used by an electronic circuit to crea~e signals which are measures o~
angular velocity o~ khe gyro as in patent 9,157,495.
;
~ ~4~19 GCD ~0-1 ;
.
RELATED PATENTS
PATENT NO. INVENTOR TITLE ISSUED
. . . _ _ ,~ --_ _ _ __ _ 4,157,495 B.C.Grover, et al. Nuclear Magnetic 6/5/79 Resonance Gyro
1 164529 GCD ~0-I
lhe NMR cell is mounted within a set of magnetic shields in order to attenuate external magnetic ~ields to acceptably low levels. Magnetic field coils are used to apply very uni~orm magnetic fields t~ the NMR cell. Both a steady field and an AC
5 carrier field are applied along the sensitive axis oF the device L
and AC feedback fields are applied along one of the transverse axes. The DC magnetic fields along both transverse axes are controlled to be substantially zero. The N~IR cell con~ains a single alkali metal vapor, such as rubidium, together with two 10 isotopes of one or ~ore noble gases, such as krypton-83, and xenon-129, or xenon l31. A buffer gas such as helium may also be contained in the cell.
The NMR cell is illuminated ~y a beam~o~ circularly polarized light that originates from a source such as a rubidium 15 lamp or a rubidium solid state laser and which passes througn the cell at an angle with respect to the steady magnetic fieldc Absorption o~ some o~ this light causes the atomic magnetic ~oments of the rubidium atoms to be partly aligned in the direction of the steady magnetic field. This alignment is partly 20 trans~erred to the nuclear magnetic moments of the noble gases, and these moments are caused to precess about the direction of the steady magnetic field, which in turn creates magnetic fields tha~ rotate at the respective Larmor precession frequencies of the two noble gases. These rotating fields modulate the 25 precessional motions o~ the rubidium magnetic moments, which in 1164529 GCD BO~
turn prodllces corresponding modulations of the transmitted light, therehy making is possible optically to detect the Larrnor precession frequencies of the two noble gases.
. .
The modulations of the light intensity are converted into electrical signals by a photodetector, and these signals are then electronically demodulated and filtered to provide signals-at the Larmor precession frequencies of the two noble gases. The dif~erence between the t~o precession frequencies is used accurately to control the steady magnetic field so that it is constant. One of the noble gas precession frequencies is compared to a precision reference frequency, and the resul~ing difference ~requency is a measure of the angular rotation rate of ~ -the g~roscope~
The two detected noble gas precession signals are also 15 ~sed to generate two AC feedback magnetic ~ields at the Larmor ~ . - . . ...... . . .... . . . .
precession frequencies of the noble gases, and these are responsible for sustaining the precession of the nuclear magnetic moments of the noble gases. The use of an AC carrier magnetic field facilitates the optical detection of the precessing noble 20 gas moments,and it provides means for controlling the DC magnetic fields along the two ~ransverse axes of the gyroscope.
According to ~he patent, the NMR gyroscope includes means for the simul~aneous alignment of ~he nuclear magnetic moments of at least two nuci~ar moment gases, thereby constituting a nuclear 116~529 ~ GCD ~0-l , ma~netic momen~ alignment device; the means for achieving sustained precession of these moments, thereby constituting a nuclear magnetic resonsnce oscillator capable of sustained oscillations, the means for ~he optical detection of these precessing nuclear moments thereby constituting a nuclear magnetic resonance detection device; the ~eans for accurately controlling the internal magnetic field of the device; and the ~ '-means for the accurate measurement of ~he frequency or phase of.
the detected nuclear moment precession signal of at least one of the nuclear moment gases to provide a measurement of the angular rotation rate or angular displacement, respectively, o~ the device with respect to inertial space, thereby constituting an NMR gyroscope~ . .
- ` . ;.
More particularly, a steady magnetic field is applied to an NMR cell which is substantially shielded from other steady magnetic fields The NMR cell contains a gas or vapor of a substance that possesses a magnetic moment that can be aligned by optical p~mping, together with one or more additional gases, each of which possesses a nuclear magnetic moment~ The NMR cell is 1.
illuminated by optical pumping liqnt whicA has a directional component that is parallel to the direction of the steady magnetic field and which has the proper wavelen~th to be absorbed by the optically pumpable substance and partially align the , I .
magnetic momen~s o~ that substance~ The nuclear moments of the 2~ nuclear moMent gases are ca~sed to become aligned and are caused to precess at their respective Larmor precession ~requencies D~ 5 ~ 4 5 2 9 GCD 80-1 about the direction o~ the steady magnetic field. An AC magnetic field at a suitable carrier ~requency is also applied to the NMR
cell, and the cell .is illuminated by detection light ~hich has a directional component that is orthogonal to the c~irection of the AC carrier magnetic field and which has a wavelength that is essentially the s~me as that of the op~icai p~ping light. The intensity of the part of the detection light that is trans~itted ~.
by the cell is modulated in accordance with the totality of the magnetic fields present in the cell, including the magnetic fields that are generated by the precessing nuclear maynetic moments. These modulations of the trans.nitted light intensity are detected by a photodetector, after which they are ; electronically demodulated to obtain signals at the Larmor ~ precession frequencies of the nuclear momen~ gasPsS.-:
.' , 1~ In one embodiment of the patented invention, the alignment of the nuclear magnetic moments of each nuclear moment gas is accomplished by collisional interactions between the atoms of the optically pompable substance and the atoms of the nuclear moment gas or gases. Sustained precession of the nuclear magnetic moments o~ each nuclear moment gas is accomplished by the application of an AC feedback magnetic field at the Larmor precession frequency of the nuclear moment gas in a direction that is ortho~onal to the direction of the steady magnetic field.
The AC carrier magnetic ~ield is applied at substantially the Larmor precession frequency o~ the optically p~npable substance and in a direction that is substantially parallel to the Page 6 .
~ 4 ~ 2 9 ~CD 80-1 , direction of the steady magnetic field, thereby permittiny the device to be operated at higher values of the steady rbagnetic field strength and with correspondingly hi~her Larmor precession frequencies for the nuclear moment gases.
. . , In the preferred embodiment, an optically pumpable substance such as a single alkali metal vapor is placed in an N~lR
cell together wi~h two noble gases, and the nuclear magnetic moments of both noble gases are aligned simultaneously by collisional interactions between the atoms of the sing:le alkaIi ~etal atoms and the atoms of the two noble gases. In this pre~erred embodiment of the invention, the alkali me~al is rubidium and the noble gases are xenon-129 ! and xenon 131.
. Another feature of the patent invo].ves the use of at least one buffer gas in substantial quantities ;.n the NMR cell~.
' ' ' ' - ' In accordance with still another feature of the paten~, the magnitude of the steady magnetic field is ca~sed to remai.n constant by feedback control of the field in such a way that the difference between the Larmor precession frequencies of the two noble yases in the N~lR cell is caused to be equal to a predetermined constant value.
In accordance with yeL another ~eature of the patent, one .
of the Larmor ~recession frequencies is compared to a precision reerence ~requency and the resulting difference ~requency is utilized to provide a measuremen~ of angu:Lar displacement or an~ular rate of the device about the direction of the steady ,, magnetic field. !:
SU~ RY OF T~JE INVENTION
'; - ' ~, It is contemplated b,y this invention to include ~wo rather than one alkali metal vapors within the MMR en~elope. Oné of the vapors, for example rubidium, is used because it is easily excited or pumped by light from a rubidium lamp or a laser at the rubidium wavelength~ The other alkali metal vapor, for example cesium, is easily pumped by a cesium lamp or laser at the cesium ; 15 wavelength. The cesium within the NMR enclosure,is modulated at the Larmor precession frequencies of the two nuclear magnetic moment gases such as xenon 129 and xenon 131. The cesium vapor ;' is illuminated, for example, by a cesium lamp or a laser, and the transmitted cesium radiation is modulated at the Larmor 20 precession frequencies of the two nuclear moment gases. The ', transmitted light is detected, and the detected signals are used in a manner identical to that déscribed in patent 4,157,495.
' ' , It is therefore an object of this invention to provide an N~R gyroscope usin~ one pumpable vapor and a different sensing vapor. The words "different vapor" are defined herein to include di~ferent isotopes o~ the same vapor, particularly where the vapor is an alkali metal vapor.
.
. Page 8 ~CD ~0-l ~
~ ~452~ I~
It is a more specific object of this invention to use two - alkaline vapors in an NilR gyro.
It is still a more speciic object of this invention to use rubidium vapor as a pumping vapor and cesium vapor as a 5 detection vapor in an ~MR gyro which uses two aligned nuclear ,;
moment gases precessing at their Larmor precession frequencies.
. .
- DESC~IPTION OF THE DRAWINGS
The only figure i5 a conceptual diagram illustrating the p~ocesses of optical pumping and of modulation of ~he itensity of the light that is transmitted by the NMR cell.
' " .'.
DETAILED DESC~IPTIG~ E
PREFER~ED E~ODI~
The figure is a conceptual diagram illustrating for each of the noble gases the process of optical p~nping and of modulation of the intensity of the light that is transmitted 5 through the NIIR cell 28. Because these processes are so similar for the two noble gases, they are illustrated and descrihed ~or only one of the two noble gases. The circularly polarized plunping light, ~or example from a laser at the rubidium wavelength, which enters the NMR cell 28 has a component 64 along the z-axis. Through the interactions of the opticai pumping light 64 and the steady magnetic field 68, the rubidium atoms ~0 have their magnetic moments aligned preferentially in the z-direction; ~y interatomic collisions, this magnetic moment ` ~
, - GCD 80-1 ~ 164~29 alignment is transferred rom the rubidium atoms 60 to the noble gas nuclei 62 and to the cesium atoms 61.
' A sinusoidal AC feedback magnetic field 70 that is matched in frequency and phase to the Larmor precession frequency of the coliective magnetic moment of the noble gas nuclei 62 is applied in the x-direction and serves to torque the magnetic moment of these nuclei to the X-y plane. This component of noble gas . ', nuclear magnetic mom~nt then precesses in the x-y plane at the noble gas Larmor precession frequency abou~ the s~eady magnetic field 68. This preces~ing ,nuclear magnetic moment component creates a nuclear precession magnetic field that rotates'in the x-y plane.
, The detection light 66 at cesium wavelength, for example~
from a cesîum l~mp or a laser, interacts ~7ith the cesium atoms 1~ which are under the influence of the steady magnetic field 68, a superimposed AC carrier magnetic field 69, and the y-component of the nucle~r precession field. This interaction causes the intensity of the x-component of the transmitted cesium light 72 - to be modulated at the carrier frequency, with a modulation 20 envelope 7~ at the nuclear precession frequency, These llght modùlations are then converted into electrical signals by the photodetector 40. The electrical signals may be used by an electronic circuit to crea~e signals which are measures o~
angular velocity o~ khe gyro as in patent 9,157,495.
;
~ ~4~19 GCD ~0-1 ;
.
RELATED PATENTS
PATENT NO. INVENTOR TITLE ISSUED
. . . _ _ ,~ --_ _ _ __ _ 4,157,495 B.C.Grover, et al. Nuclear Magnetic 6/5/79 Resonance Gyro
3,103,623 I.A. Greenwood, Jr. Nuclear Gyroscope 9/10/63 3,103,624 I A. Greenwood, Jr. Nuclear ~yroscope 9/10~63 e a .
3,396,329 A. Salvi Magnetic Resonance 8/6/68 Magnetometers for Measuring ~eak Mag-netic Fields From Aboard a Moving Vehicle ; as a Plane 3,404,332 A.Abragam, et al. Magnetic Resonance ~evices for Accurately ~easuring Magnetic Fields in Particular Low Magnetic Fields, on Board of a Movable Body 3,500,176 A. Xastler, et al. Method and Apparatus 3/10/70 for Controlling a l~ag- ~-netic Fiel~ E~lploying Optically P~mped Nuclear Resonance 3,S13,381 ~. Ha2per, Jr. Off-Resonant Light as /19/70 Probe of Optically Pumped Alkali Vapors 3,729,674 J.R.Lowdenslager Digital Nuclear Gyro- /24/73 scopic Instrumentation and Di~ital Phase Locked Loop Therefore ~_ ~__ ....................... _ ...... _. . _ .. .
Pago 11 ~ 18~52~
', In conclusion, the present invention has been described in terms of particular elements and particular physical arrange-ments, but it is clear that reasonable alternatives, such as the use of different optical paths accomplishing the sarne results, o~
the use of different combinations of the noble yases or the use of a different pumpable substance than rubidium and cesium, or the use of other va].ues for the freq~encies or magnetic fields mentioned in the foregoing specification, may a].l be within the . scope of the present invention.
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: , "' ' ' ' ' ~
. . .
3,396,329 A. Salvi Magnetic Resonance 8/6/68 Magnetometers for Measuring ~eak Mag-netic Fields From Aboard a Moving Vehicle ; as a Plane 3,404,332 A.Abragam, et al. Magnetic Resonance ~evices for Accurately ~easuring Magnetic Fields in Particular Low Magnetic Fields, on Board of a Movable Body 3,500,176 A. Xastler, et al. Method and Apparatus 3/10/70 for Controlling a l~ag- ~-netic Fiel~ E~lploying Optically P~mped Nuclear Resonance 3,S13,381 ~. Ha2per, Jr. Off-Resonant Light as /19/70 Probe of Optically Pumped Alkali Vapors 3,729,674 J.R.Lowdenslager Digital Nuclear Gyro- /24/73 scopic Instrumentation and Di~ital Phase Locked Loop Therefore ~_ ~__ ....................... _ ...... _. . _ .. .
Pago 11 ~ 18~52~
', In conclusion, the present invention has been described in terms of particular elements and particular physical arrange-ments, but it is clear that reasonable alternatives, such as the use of different optical paths accomplishing the sarne results, o~
the use of different combinations of the noble yases or the use of a different pumpable substance than rubidium and cesium, or the use of other va].ues for the freq~encies or magnetic fields mentioned in the foregoing specification, may a].l be within the . scope of the present invention.
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: , "' ' ' ' ' ~
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Claims (4)
1. In a nuclear magnetic resonance detection device including a nuclear magnetic resonance cell, a gas vapor of a first optically pumpable substance that possesses a magnetic moment and is capable of being optically pumped, said pumpable substance being contained in said cell, at least one nuclear moment gas each having a nuclear magnetic moment also contained in said cell, the nuclear magnetic moments of each said nuclear moment gas being at least partly aligned, means for applying a steady magnetic field to said cell, first means for illuminating said cell with pumping light capable of partly aligning the magnetic moments of said optically pumpable substance in one direction by absorption of said light, means for precessing said aligned nuclear magnetic moments of each said nuclear moment gas about the direction of the steady magnetic field at the respective Larmor precession frequencies of each said nuclear moment gas, means for applying an AC carrier magnetic field to said cell, the improvement comprising:
a gas vapor of a second optically pumpable substance that possess a magnetic moment and is capable of being optically pumped, said second optically pumpable substance being contained in said cell;
second means for illuminating said cell with detection light of a wavelength approximately equal to a wavelength which can be absorbed by said second optically pumpable substance means for applying said detection light orthogonal to the direction of said AC carrier magnetic field to produce modulations in the intensity of the transmitted part of said detection light substantially at the frequency of at least one harmonic, including the fundamental of said AC carrier magnetic field; and means for detecting at least one of said modulations in the intensity of the transmitted part of said detection light.
a gas vapor of a second optically pumpable substance that possess a magnetic moment and is capable of being optically pumped, said second optically pumpable substance being contained in said cell;
second means for illuminating said cell with detection light of a wavelength approximately equal to a wavelength which can be absorbed by said second optically pumpable substance means for applying said detection light orthogonal to the direction of said AC carrier magnetic field to produce modulations in the intensity of the transmitted part of said detection light substantially at the frequency of at least one harmonic, including the fundamental of said AC carrier magnetic field; and means for detecting at least one of said modulations in the intensity of the transmitted part of said detection light.
2. Apparatus as recited in Claim 1 in which said two optically pumpable substances are different alkali metal vapors.
3. Apparatus as recited in Claim 2 in which said first optically pumpable substance is rubidium vapor and said second optically pumpable substance is cesium vapor.
4. Apparatus as recited in Claim 3 in which said first means for illuminating is a laser at rubidium wavelength, and said second means for illuminating is a laser at cesium wavelength.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US16233780A | 1980-06-23 | 1980-06-23 | |
| US162,337 | 1980-06-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1164529A true CA1164529A (en) | 1984-03-27 |
Family
ID=22585197
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000379449A Expired CA1164529A (en) | 1980-06-23 | 1981-06-10 | Nuclear magnetic resonance gyro |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5729908A (en) |
| CA (1) | CA1164529A (en) |
| DE (1) | DE3123188A1 (en) |
| FR (1) | FR2485206A2 (en) |
| GB (1) | GB2078972B (en) |
| IT (1) | IT1142450B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104457730A (en) * | 2014-12-31 | 2015-03-25 | 中国电子科技集团公司第四十九研究所 | Micro-structure nuclear magnetic resonance gyroscope |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19928032C2 (en) * | 1999-06-18 | 2001-05-23 | Forschungszentrum Juelich Gmbh | Measuring device for measuring the absolute polarization of alkali atoms and method for operating the measuring device |
| US4525672A (en) * | 1983-03-30 | 1985-06-25 | Litton Systems, Inc. | Apparatus and method for laser pumping of nuclear magnetic resonance cell |
| US8159220B2 (en) * | 2009-08-03 | 2012-04-17 | Northrop Grumman Guidance And Electronics Company, Inc. | Nuclear magnetic resonance gyroscope mechanization |
| US9062973B2 (en) * | 2011-01-31 | 2015-06-23 | Northrop Grumman Guidance And Electronics Company, Inc. | Atom beam gyroscope |
| CN103528580A (en) * | 2013-10-23 | 2014-01-22 | 中国科学院电工研究所 | Method for measuring rotating angle of aircraft based on nuclear magnetic resonance |
| CN104407003A (en) * | 2014-12-26 | 2015-03-11 | 苏州露宇电子科技有限公司 | Novel nuclear magnetic resonance analysis meter |
| CN111060089B (en) * | 2018-10-17 | 2022-07-15 | 北京自动化控制设备研究所 | High-sensitivity nuclear spin precession detection method based on electron spin magnetic resonance difference |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3513381A (en) * | 1967-07-17 | 1970-05-19 | Varian Associates | Off-resonant light as a probe of optically pumped alkali vapors |
-
1981
- 1981-06-10 CA CA000379449A patent/CA1164529A/en not_active Expired
- 1981-06-11 DE DE19813123188 patent/DE3123188A1/en not_active Withdrawn
- 1981-06-22 FR FR8112216A patent/FR2485206A2/en active Granted
- 1981-06-22 IT IT48726/81A patent/IT1142450B/en active
- 1981-06-23 JP JP9607481A patent/JPS5729908A/en active Pending
- 1981-06-23 GB GB8119336A patent/GB2078972B/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104457730A (en) * | 2014-12-31 | 2015-03-25 | 中国电子科技集团公司第四十九研究所 | Micro-structure nuclear magnetic resonance gyroscope |
Also Published As
| Publication number | Publication date |
|---|---|
| IT1142450B (en) | 1986-10-08 |
| IT8148726A0 (en) | 1981-06-22 |
| FR2485206B2 (en) | 1985-01-11 |
| GB2078972B (en) | 1984-04-26 |
| JPS5729908A (en) | 1982-02-18 |
| GB2078972A (en) | 1982-01-13 |
| FR2485206A2 (en) | 1981-12-24 |
| DE3123188A1 (en) | 1982-04-22 |
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