PROGRESS ON ATOMIC GYROSCOPE

Y. LiuBeijing Institute

of Aerospace Control Devices,Beijing, China

M. ShiBeijing Institute

of Aerospace Control Devices,Beijin, China

X. WangBeijing Institute of Aerospace Control

DevicesBeijin, China

Atomic gyroscopes can be used to measure carrier's rotationinformation by atomic spin or Sagnac interference effect, whichhave the characteristics of high precision, small volume, and soon. In the first part, atomic gyroscopes are discussed with theirprinciples, and recent research statues. In the second part, it ispresented that the progress of nuclear magnetic resonance gyro(NMRG), spin-exchange relaxation free gyro (SERFG) and coldatomic interferometer gyro (CAIG) have been achieved in Beijinginstitute of control devices (BICD). For the NMRG, the keytechnologies are introduced, which include long relaxation timeof small sized vapor cell manufacture, non-magnetic electronicheating system, static magnetic field stabling with doubleworking materials, and the frequency of the laser stabling. Theresearch achievements of NMRG in BICD are presented that, theEarth's Rotary Rate (ERR) has been sensed, the bias drift isbetter than 3°/h(1 ). For the SERFG, the key technologies areintroduced about high pressure vapor cell manufacture, andnuclear magnetic field compensation. The SERFG prototype inBICD is shown. For the CAIG, the key technologies areintroduced about cold atoms maintaining in free space, chip foratoms manufacture, Raman pulse preparation, and cold atomsinterference. The research achievements of CAIG in BICD arepresented that the temperature of the cold atomic clusterachieved to 3 K, the number of the atoms in the cluster reaches107. At last, the future applications and the development trends ofatomic inertial systems are prospected with the remarkableperformance of NMRG, SERFG, and CAIG.

Keywords: atomic gyroscope; atomic interference; Nuclearmagnetic resonance; Spin exchange relaxation free.

I. INTRODUCTION

Gyroscope can build the inertial frame for navigationsystems, which are used to measure carrier’s rotationinformation. It is the key device in the inertial unit for modernaerospace, aviation and national defense industry [1]. Thedevelopment of gyroscope experienced the rotor gyroscopebased on Newton mechanism [2], the optical-gyroscope basedon Sagnac effect [3-4], the MEMS gyroscope based on MEMStechnique [5] and the atomic gyroscope based on atomicinterference or spin effect [6-8]. The rotor and opticalgyroscopes are used in ship, airplane, rocket, and satellite forautomatic navigation or state controlling, which are extensivelyused even today. The MEMS gyroscope refers to the smallsized gyroscopes based on the MEMS technique, which is usedto the state controlling for the small sized aerial vehicle andconsumer electronics.

Atomic gyroscopes are the new type of gyroscopes usingthe atomic interference and spin effect to sense the carrier’srotation information, which have high sensitive and smallsized. For example the theoretical bias drift of the cold atomicinterference gyroscope can be reached about10-10°/h [6,7], andthe nuclear magnetic resonance gyroscope has realized theengineering prototype with volume of 5 cm3 and bias drift of0.01°/h [8]. As the attentions have been put on the atomicgyroscope by domestic and abroad, it can lead to the newgeneration of the navigation system for modern navigationequipments.

TABLE I. THE CHARACTERISTICS OF THE ATOMIC GYROSCOPES

Type Name Principle Characteristics

Theoreticalbiasdrift°/h

Realizedbias drift

°/hStatus

Ato

mic

Gyr

osco

pe Ato

mic

spin

NuclearMagnetic

ResonanceGyroscope(NMRG)

Nuclear spinis used to sense

carrier’srotation

information

Highsensitivity,small size,

andlow

consumption

10-4

10-2

Engi

neer

ing

Prot

otyp

e

SpinExchangeRelaxation

FreeGyroscope(SERFG)

Electronicspin

is used tosense

carrier’srotation

information

Highsensitivity,and small

Size10

-8

10-4

Prot

otyp

e

Inte

rfer

ence Atomic

InterferenceGyroscope

(AIG)

Sagnac effectof atomic

wave-packetis used to sense

carrier’srotation

information

Super highsensitivity 10

-10

10-5

Prot

otyp

e

A. Nuclear Magnetic Resonance Gyroscope1) PrincipleThe precession of nuclear spin magnetic moment along the

static magnetic field is used to sense carrier’s rotationinformation. The output of NMRG is obtained by measuringthe variation of the precession frequency. The Larmorfrequency of nuclear spin precession is proportional to themagnitude of the static magnetic field. The precessionfrequency is satisfied by the formula of ωL=γB0，where B0 isthe magnitude of the static magnetic field. When the carrierhas a rotation rate with Ω，the precession frequency will be

ωL=γB0±Ω. （1）

The carrier’s rotation rate system can be obtained bycomparing L with γB0 [9].

Fig. 1. The principle of NMRG

Three steps have been prepared for NMRG. Step one is toprepare the polarization of the nuclear spin. The noble gasatoms are chosen with odd number nuclei, which are polarizedby collided with alkali metal atoms. The alkali metal arevaporized by heating and polarized by pump laser with circularpolarized light. The nuclei form the macro magnetic moment[10, 11]. Step two is to prepare a transverse driving magneticfield, which has the same frequency with atomic Larmorprecession. The nuclei reach the resonant state. Step three is toprepare a transverse linear polarized light. The polarizationplane rotates an angular due to Faraday effects, which is relatedto the precession of nuclear magnetic moment. The nuclearspin precession frequency is measured by the variation of therotation angular. When the carrier has a rotation rate along thedirection of static magnetic field, the detecting frequencychanges the same rate, which is measured by the linear light.

B. Recent research statusThe USA began the research on the NMRG by 70s’.

Kearfott and Litton adopted different materials and detectingmethods in 1979, which made two different NMRG prototypes.The bias stabilities reaches 0.05°/h（1σ）and 0.1°/h（1σ）,respectively [12,13]. Unfortunately, the research on NMRGremained stagnant due to the rapid development of optical fibergyroscope and ring laser gyroscope at the same time. In 21century, MPNT project has been proposed by USA DARPA. Itis aimed to solve the automation navigation when the GPSnavigation is not be used in some conditions. The NMRGbecame a hot research point after that. The Northrop GrummanCompany continued this research, and it succeed on developinga prototype of the NMRG since 2005, which is 5cm3 withoutthe electronics, the bias stability is 0.01°/h (1σ), the ARW is0.005°/√h(1σ), the bandwidth is 300Hz, the measurement rangeis ±2500°/s, and the nonlinearity of the scale factor is 50ppm,which represents the highest technology in the world. Theprototype is shown in Fig. 2.

Fig. 2. The prototype of NMRG by NGC in 2014

C. SERF Gyroscope1) PrincipleThe principle of the SERF gyroscope is shown in Fig 3.

The alkali metal, noble gas and high pressure buffer gas arefilled in a vapor cell. When the temperature of the vapor cellreaches the working point, the alkali metal atoms arevaporized. The spin of the atoms are polarized by a circularpolarization pumping light, and the nuclei of the noble gasatoms are also polarized by collided with the alkali atoms. Inthe static magnetic field, the alkali atoms begin precessionalong it. When a linear polarized light goes through the vaporcell, the polarization plane rotates an angular, which isproportional to the projection of the alkali atomic spin on thelight.

Fig. 3. The principle of the SERF gyroscope, ESMM is the electronic spinmagnetic moment, and NSMM is the nuclear spin magnetic moment

The static magnetic field is parallel to the pump light. Thenuclear spin of the noble gas atoms form a macro magneticmoment of nM

, and it generates an effective magnetic field

n nB M

, where is the coefficient. The effectivemagnetic field can be cancelled by the external magnetic field,which satisfies the formula by 0 0nB M

. Nuclear spin

magnetic field will change along the static magnetic field, andthe electronic spin of the alkali atoms can keep unchangeable.In high pressure condition, the collision among the alkali atomsbecome frequent, the electronic spin goes into SERF regime,where the collision is far more rapid than the Larmorprecession frequency. In the moment, the alkali atoms aresensitive to the rotation of the system, which can be detectedby the linear polarized detecting light.

2) Recent research statusSERF gyroscope is firstly made by the research group in

Princeton University in 2002. It can also be used to investigatethe Lorentz violation [14-18]. The prototype of the SERFgyroscope is shown in Fig. 4. After then, the research groupestablished a company named Twinleaf, which continued to theresearch on the SERF gyroscope, and they are founded by USADARPA. HoneyWell Company has also proposed a scheme ofchip scale SERF gyroscope [19-21].

Fig. 4. The prototype of the SERF gyroscope by Princeton University

D. Atomic Interference Gyroscope1) PrincipleIn the end of the 20th, the clod atomic interferometer

developed rapidly, since the development of the technology ofmanipulation of laser and clod atom. At the same time, theatomic interferometer gyroscope became a hot research due toits super high sensitivity. The Sagnac effect of atomic wavepacket is adopt to sense the carrier’s rotation information inAIG. The principle of the AIG is shown in Fig. 5. The atomsare divided into two beams, and they separate at the left andcombine at the right. The two beams generate interferencestrips. When the system has an angular rate of , the stripsmoves down.

a) b)

Fig. 5. The principle of the atomic interferometer gyroscope

The AIG manipulates the atoms in very low temperature[22, 23]. First, the atoms are prepared to expected energy statein low temperature. Second, the atoms are separated, reflected,and combined by a Raman pulse sequence of

/ 2 / 2 . Last, the strips are measured by a laser.The process is shown in Fig. 5, b. When the system has an

angular rate, the phase of the strips changes because of theSagnac effect,

4atom

m Ah

， （2）

where m is the mass of the atom, h is the Plank constant,

is the carrier’s rotation rate, and A

is the area of atomicinterference ring. With the same area, the sensitivity of AIG ishigher than the optical gyroscope by 10 order of magnitude,because the atom mass is higher than photon mass by 10 orderof magnitude.

Fig. 6. The prototype of AIG by Stanford University

2) Recent research statusThe development of AIG began in 1991. Germany, France,

and USA started to investigate AIG based on the Sagnac effect.In 2006, Pairs astronomical station realized an AIG with threeaxes measurement, and the short term sensitivityreached 7 1/22.4 10 / /rad s Hz , and the long term

sensitivity reached8 1/210 / /rad s Hz

[24].

In 2008, Hanover University in Germany built a small sizeddouble interference AIG, and the short term sensitivity reached

7 1/26.1 10 / /rad s Hz [25, 26]. In 2011, StanfordUniversity built a prototype of AIG with the ARW 2.95×10-4

o/h1/2. The prototype is shown in Fig. 6. Although the prototypehas been realized, it is far away from the engineeringapplication.

II. PROGRESS IN BICD

A. Nuclear Magnetic Resonance Gyroscope1) Small sized vapor cell with long relaxation timeVapor cell is the heart of NMRG. The first key factor is the

relaxation time, which decides the performance of NMRG. Forexample, the long the relaxation time, the better the bias drift.Now, the relaxation time of 129Xe is up to 20 s in our lab. Theother key factor is the size of vapor cell, which decides thevolume of NMRG. Now, the small vapor cell with the size of3mm has been made in our lab.

2) Non-magnetic electronic heating systemBecause the gyro system measures the angular rate of the

carrier by measuring the spin magnetic moment of the nucleus,the internal magnetic field of the system has a great influenceon the measuring results. So the non-magnetic electronicheating system is in crying needs for the development ofNMRG. In order to create a high precision non-magneticenvironment, in the structure, highly fitting flexible heatingpiece has been applied to increase the contact heating area. Atthe same time, other two measures are also adopted to decreasethe heating field. The first one is double superposition withinstead current. The second one is reciprocating the line backand forth. These two measures can counteract the magneticfield produced by the heating line, so the total heating field canbe reduced for the maximum limit. After repeatedlyimprovement and adjustment, the heating magnetic field hasbecome nT order from the μT order.

3) Static magnetic field stabling with double workingmaterials

The perturbation of the static magnetic field affects the biasstability of the gyroscope. To suppress this effect, double noblegases are adopt, and the output is

1 1 1

2 2 2

Rz L

Rz L

B

B

(3)

where 1R , 2

R are the frequencies of the two driving field for

the two gases, respectively, γ1 and γ2 is the gyromagnetic ratiosof the two noble gases, respectively, Bz is the static magneticfield, 1L and 2L are the differences of the frequency ofthe two noble gases between their inertial frame and Larmorfrequency. The output of the closed loop is obtained from Eq.(7),

2 1 1 2 2 1 1 2

2 1 2 1

R RL L

out

.

(4)

Because of the error in the controlling system, 1L and

2L are not zero exactly. The fluctuation of zB affects

1L and 2L indirectly, and it causes bias error.

4) Frequency of the pump laser stablingThe frequency fluctuation of pump laser makes the pump

rate change, and the macro magnetic moment cannot keepsteady, which has a great influence on the zero-bias stability ofthe NMRG. The wavelength modulation method is used tomake the frequency of the pump laser stabilized at the atomictransition frequency of 87Rb. As shown in Fig. 7, the zero-biasstability of NMRG decreases from 889°/h(1σ) to 98°/h(1σ)when the frequency fluctuation of pump laser is controlled.

Fig. 7. The development history of NMRG by BICD

In China, Beijing institute of control devices (BICD) hasalso developed a principle prototype of NMRG. Thedevelopment history is shown in Fig. 8. A prototype with thevolume of 20000 cm3 has been made in 2014, while its volumehas been down to 2000 cm3, and the bias drift reaches200°/h(1σ) in 2015. Now, the bias drift of NMRG is better than3°/h(1σ), with a volume of 120 cm3.

Fig. 8. The development history of NMRG by BICD

Fig. 9. Bias drift of NMRG

The bias of NMRG in BICD is about -26°/h, and the biasstability is 2.2°/h, which is shown in Fig. 9. The earth’s rotaryrate is also measured, which is shown in Fig.10. The rate ofrotating platform is 0.3°/s and the curve with 100 s smoothing.When the static magnetic field is locked by the closed loopmethod, the measurement rate is close to the earth’s rotary rate.The output of the voltage peak-peak of the static magnetic fielddecreases to 0.0014 V. The measurement rate is 23.18°/h. Themeasurement error is 0.22°/h compared to the nature value22.96°/h in Beijing.

Fig. 10. The earth’s rotary rate measurement in BICD

B. SERF Gyroscope1) High pressure vapor cell manufactureThe relaxation time of electronic spin and nuclear spin are

related to the precision of the SERF gyroscope. Longerrelaxation time of them means less sensitive to the noise of thegyroscope. The relaxation rate from the cell wall is the mainfactor to the relaxation time in the SERF regime, which needshigh pressure buffer gas to decrease the relaxation rate.Usually, the vapor cell is filled with 2 to 3 atm. buffer gas,which makes it hard to manufacture. In BICD, the highpressure vapor cell equipment has been built. The high pressurevapor cell will be made recently.

2) Nuclear magnetic field compensationThe principle of the SERF gyroscope is that the external

magnetic field is compensated by the nuclear spin magneticfield, therefore electronic spin can keep its orientation in theinertial frame. The nuclear magnetic field compensationprocess is the key technology to realize the high precisiongyroscope. In BICD, we have realized the nuclear magneticfield compensation.

When the system is steady, generate a square wavemagnetic field on the y direction. As shown in Fig.11, thesignal has different outputs as zB in different regions.

Whenn

zB B , the signal is steady, which is unaffected bythe input magnetic field. The nuclear spin magnetic fieldcompensates the change of the magnetic field. It can be seen inFig. 11.

Fig. 11. Red line is yB , and black line is S. Left figure, nzB B , S and

yB are in phase; middle figure, nzB B , S is zero; right figure,

nzB B , S and yB are in opposite phase

BICD in China investigated the SERF gyroscope since2015. It succeeded realizing the SERF effect and made aprototype of the SERF gyroscope. The prototype is near4000cm3, and the measurement range is 0.1o/s to 50o/s. Fig.12shows the development history of the SERF gyroscope inBICD.

Fig. 12. The development history of SERF gyroscope in BICD

C. Atomic Interference Gyroscope1) Cold atom trapping and its state manipulationWe build an experimental platform which includes laser

system, magnetic system, and electric system, and prepare anensemble of cold atoms with the temperature of 4µK and thenumber of 107 in a MOT by laser cooling technique in our lab.The atoms can be prepared in any of the two hyperfine splittingenergy states as the initial internal state.

2) Raman pulse preparationRaman pulse sequence consists of two laser beams which

have fixed frequency difference and stable phase difference inour lab. We have implemented Raman laser using optical phaselock loop, the beating frequency bandwidth is less than 1Hz,We also demonstrate the Raman π pulse as atomic beamreflector, andπ/2 pulse as atomic beam splitter.

3) Cold atoms interferenceWe set up the florescence image system which can detect

the atomic numbers in particular atomic internal state, andinject the Raman pulseπ/2-π-π/2 sequence on the cold atom.We have observed the interference fringe by modulating one ofthe Raman pulse, the contrast of this fringe is greater than 60%.

Fig. 13 shows the research platform in BICD, whichconsists of cooling laser, re-pump laser, Raman laser, magneticcoils and some optical elements. We demonstrate cold atominterferometer which is the milestone step to AIG in our lab.

Fig. 13. Research platform of AIG in BICD

Fig. 13 shows the development history of AIG in BICD.We began this project in 2011, and observed the cold atomwith the temperature of 200µK in the MOT in 2013. Then wefurther cooled the atoms below 10µK using the Sub-Dopplerlaser cooling technique. The top two pictures show theexperimental results of atom cooling. The left picture is imagedby general CCD and the right picture shows the evolution ofthe released cold atoms imaged by EM-CCD. Then we lockedthe two laser phases and prepared Ramanπ pulse in 2015. Theexperimental results are showed on the middle two pictures ofFig 13. The left shows the spectrum of two Raman laserbeating signal, and the right shows the Rabi oscillations of coldatoms driven by Raman pulse. At the end of 2016, we observedthe interference fringe shown in the bottom of Fig. 14.

Fig. 14. The development history of AIG in BICD

III. FUTURE APPLICATIONS

A. Strap down navigation systemIn strap down navigation system, the gyroscope is fixed to

the system. The working environment is unexpected, whichrequired the gyroscope to be large measurement range andbandwidth, stable scale factor, insensitive to vibration andcollision. The NMRG has no moving parts, which has thecharacteristics of large bandwidth, insensitive to vibration andcollision. It suits to the strap down navigation system. Itdevelops very rapidly in the recent decade. In 2015, NGC hasmade a NMRG with navigation level bias stability 0.01°/h(1σ),measurement range ±2500°/s, bandwidth 300Hz, and it has alsofinished the acceleration and vibration experiments. It has thepotential to be the first one in engineering application. Themain application fields include rocket, satellite, ship,unmanned plane, automatic vehicle, etc.

B. Platform navigation systemIn the platform navigation system, the framework isolates

the vibration for gyroscopes. The gyroscope can work in smalldynamic range and bandwidth, lower stability of the scalefactor than using in the strap down navigation system. BothSERF gyroscope and AIG are high bias drift, small bandwidth.They are suited to the platform navigation system because oftheir large volumes and small bandwidths. A long termdevelopment should be planed. The main application fieldsinclude submarine, strategic missile, deep ocean exploration,space exploration, etc.

IV. CONCLUSIONS

Atomic gyroscope attracts more and more attentions in theworld. The NMRG has high bias drift, small size, which is themost developed gyroscope in atomic gyroscopes. SERFgyroscope has higher bias drift than NMRG, but it is harder torealize the small size. The cold atomic interferometergyroscope has super high bias drift, but there are also manyproblems to solve. NMRG is suited to the strap downnavigation system, which can be firstly used in engineeringapplication. SERF gyroscope and AIG can be used with theplatform navigation systems, which should be planned in longterm.

REFERENCES

[1] Liu, Y.X., Wang, W.， Wang ,X.F., Key technology and developmenttendency of micro nuclear magnetic resonance gyroscope, Navigationand Control. 2014,13(4).

[2] Yang, H. Yu, T. C., Rigas ,D., et al., Modeling and control of magneticsuspension systems, In: Proc. of the 2002 IEEE International Conferenceon Control Applications. Glasgow, UK: IEEE, 2002, pp. 944-949

[3] Wang, W., Technologies of IFOG, Chinese Astronautics Publication.Beijing. 2013.

[4] Zeng, Q.H., Liu, J. Y., et al., Newest developments of ring laser gyro,Journal of Transducer Technology. 2004, 23(11)

[5] Olivier, B., The SiREUS MEMS rate sensor program, In: Proc. of the59th IAC International Astronautical Congress. Glasgow, Scotland, UK,2008

[6] Wang, W., Wang, X.F., Ma, J.L., et al., Research progress and keytechnologies of interferometric atom gyroscope, Navigation and Control.2011, 10(2).

[7] Fang, J. and Qin, J., Advances in atomic gyroscopes: A View fromInertial Navigation Applications, Sensors . 2012, 12(5), pp.6331-6346.

[8] Meyer, D., and Larsen, M., Nuclear magnetic resonance gyro for inertialnavigation, Gyroscopy and Navigation. 2014, no 1, pp. 3-13.

[9] EKlund ,E.,Microgyroscope based on spin-polarized nuclei.PhD.Thesis， University of California， Irvine. 2008.

[10] Bouchiat, M.A., Carver, T.R., and Varnum C.M., Nuclear polarization inHe3 gas induced by optical pumping and dipolar exchange, Phys.Rev.Lett., 1960, vol. 5, pp. 373-5.

[11] Walker, T.G., and Happer, W., Spin-exchange optical pumping ofNoble-Gas Nuclei[J], Rev. Mod. Phys., vol. 69,pp. 629-42, 1997.

[12] Greenwood, I., NMRG with unequal fields.US patent.No.4147974.1979.[13] Gabrera, B., Kanegsburg, E., Mark, J., et al., Nuclear magnetic

resonance gyroscope. US patent.No.4151495. 1979.[14] Kornack, T.W., Ghosh, R.K., Romalis, M.V., Nuclear spin gyroscope

based on an atomic comagnetometer, Phys.Rev.Lett. 2005,95,230801,pp.1-4.

[15] Kornack, T.W., A test of CPT and Lorentz Symmetry using a K-3Hecomagnetometer. Ph.D. Thesis, Princeton University, Princeton, NJ,USA, 2005.

[16] Seltzer, S.J., Developments in alkali-metal atomic magnetometry. Ph.D.Thesis, Princeton University, Princeton, NJ, USA, 2008.

[17] Kornack, T., Ghosh ,R., and Romails, M., Nuclear spin gyroscope basedon an atomic comagnetometer, IEEE Sensors. 2010,17-22.

[18] Smiciklas, M., Brown, J.M., Cheuk, L.W., Smulin, S.J., Romalis, M.V.,New test of local Lorentz invariance using a 21Ne-Rb-Kcomagnetometer, Phys. Rev. Lett. 2010, 105,151604, pp.1-4.

[19] Lust, L.M., Youngner, D.W., Chip scale atomic gyroscope, U.S. PatentNo. 7,359,059, 2008.

[20] Kitching, J.et al. , Chip-scale Atomic Devices: Precision AtomicInstruments Based on MEMS[J], Proc. 2008 Symp.Freq.Stds.Metrology,pages 445-53, 2008.

[21] Romalis, M.V., Chip-scale magnetometers[J]. Nature Photonics, 2007,1(11), pp. 613-614.

[22] Jekeli ,C., Navigation error analysis of atom interferometer inertialsensor, Navigation, 2005, 52(1), pp. 1-14.

[23] Takase, K., Precision rotation rate measurements with a mobile atominterferometer, California:Stanford University, 2008.

[24] Canuel, B., Leduc, F., Holleville, D., et al., Six-axis inertial sensor usingcold-atom interferometry, Phys. Rev. Lett. 2006. 97:101402,1-4.

[25] Muller ,T., Gilowski, M., Zaiser, M., et al., A compact dual atominterferometer gyroscope based on laser-cooled rubidium, Eur. Phys.J.D.53,273-281.(2009).

[26] Tackmannl, G., Berg ,P., Schubert ,C., et al., New Journal of Physics 14,015002. (2012).

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