Compact and PortableAtom Gravimeter

Shuai ChenUniversity of Science and Technology of China

Shanghai, China / June 7th, 2019

ITU symposium on Quantum Information and Technology

Outline

• The Importance of gravity measurement

• Compact and potable atom gravimeter in USTC

• Calibration of USTC-AG02 and USTC-AG12 at NIM in 2019

• Outlook

The Earth Gravity

Latitude Altitude Solid Tide Ocean Tide & Air pressure

Internal mass distribution

Oil&Gas field

Why measure gravitational acceleration?Measurement of h& Definition of kg

Kibble balance

Outline

• The Importance of gravity measurement

• Compact and potable atom gravimeter in USTC

• Calibration of USTC-AG02 and USTC-AG12 at NIM in 2019

• Outlook

Atom Interferometer for Forces

The particle-wave duality makes the atoms ideal candidate for interferometry

𝜆𝑑𝐵 = ℎ

𝑚𝑣Δ𝜑𝑎𝑡𝑜𝑚

Δ𝜑𝑝ℎ𝑜𝑡𝑜𝑛~(

𝑐

𝑣𝑎𝑡𝑜𝑚)2= 1011~1017

Atom Gravimeter Working Process

Atom Interferometer

Φ 𝑡 = 𝑘𝑒𝑓𝑓 Ԧ𝑧 𝑡 = 𝑘𝑒𝑓𝑓𝑔

2𝑡2

Atom interference path

Φ1 = ΦΙ

Φ2A = ΦΙΙ +𝑘𝑒𝑓𝑓 Ԧ𝑣𝑟𝑒𝑐𝑇 − 𝑘𝑒𝑓𝑓

𝑔

2𝑇2

Φ2B = ΦΙΙ −𝑘𝑒𝑓𝑓

𝑔

2𝑇2

Φ3 = ΦΙΙΙ + 𝑘𝑒𝑓𝑓 Ԧ𝑣𝑟𝑒𝑐𝑇 − 𝑘𝑒𝑓𝑓Ԧ𝑔

2(2𝑇)2

ΔΦ = (Φ1−Φ2A) − (Φ2

B −Φ3)

= −𝒌𝒆𝒇𝒇𝒈𝑻𝟐 +ΦΙ − 2ΦΙΙ +ΦΙΙΙ

= −𝒌𝒆𝒇𝒇𝒈𝑻𝟐 + 𝛼𝑻𝟐

𝑃|2> =1

2(1 + cosΔΦ)

Development of Atom Gravimeters in USTC

• Running with free falling cold atoms

• Interrogation time, T=80ms• Repeatation rate: 3Hz

2015 -> Beginning, optical table based atom gravimeter

Development of Atom Gravimeters in USTC

Controller Sensor

Controller

2016 -> Prototype of the portable atom gravimeter

2017 -> The 1st generation of compact and portable atom gravimeter(USTC-AG01 & 02)

Sensor

0.6

5m

0.30 mVolume： 0.30×0.30×0.65 m3

Mass： ~40 kg

2018，USTC-AG11 & 12

Rb atom source

Interference zone

MOT & Molasses

Raman laser

Detection zone

Magnetic shield

Pump

谢宏泰等，一种原子布居数探测系统，ZL 2018 2 0133804.2杨胜军等，一种用于原子干涉重力仪探头的磁场系统，ZL 2018 2 0236129.6陈帅等， 一种适用于小型化原子干涉仪的真空结构，201711439186

Sensor Head

Volume： 0.56×0.68×0.72 m3

Mass： ~80 kg

Control and Data acquisition system

Electronic system(magnetic field & optical control,power supplies)

Cooling Repumper Pump Blowing Raman Probe …

Laser system(Two lasers)

J. –B. Long, S. –J. Yang, S. Chen and J. –W. Pan, Optics Express 26, 27773 (2018)J. –B. Long, et.al, compact laser system for atom interferometry, in preparation.龙金宝等，一种适用于冷原子干涉精密测量的双激光器系统，201711439114.7

2018，USTC-AG11 & 12

Controller

Continuous Measurement of g @Shanghai Gravimeter

USTC-AG12

32s /each g value

Sensitivity: 𝟏𝟎𝟎μGal/ 𝐻𝑧Stability: 𝟑. 𝟐μGal@2000s

Shanghai Lab, USTC2018-09-23 to 10-09

Sensitivity: 𝟔𝟎μGal/ 𝐻𝑧Stability: 𝟐. 𝟓μGal@2000s

At night

Overall

(1 μGal = 10−8 Τ𝑚 𝑠2)

Outline

• The Importance of gravity measurement

• Compact and potable atom gravimeter in USTC

• Calibration of USTC-AG02 and USTC-AG12 at NIM in 2019

• Outlook

Transportable Atom Gravimeters

Shanghai Lab, USTC NIM, Changping, Beijing

Two transportable atom gravimeters in one IVECO truck

(NIM: the national institute of metrology , China)

January 7, 2019

Calibrate Atom Gravimeters in

3D active vibration isolator

Sensor

USTC-AG02

Controller

Sensor

USTC-AG12

Controller

Measure g in Building 21, NIM@Changping (重力精测实验室II)

Continuous Measurement of g @NIM

Averaging time (s)

All

an d

evi

atio

n (𝛍

Gal

)

Averaging time (s)

All

an d

evia

tio

n (𝛍

Gal

)

Gravimeter

USTC-AG12

Gravimeter

USTC-AG02

8s /each g value

32s /each g value

Sensitivity: 𝟒𝟐 μGal/ 𝐻𝑧Stability: 𝟏. 𝟑 μGal@1000s

Sensitivity: 35 μGal/ 𝐻𝑧Stability: 𝟎. 𝟗 μGal@1000s

Tide

0 2 4 6 8

100

50

0

50

100

150

Gal

)

0 2 4 6 860

0

60

T(hour)

Res

idu

eG

al)

Tide

0 2 4 6 8

200

150

100

50

0

0 2 4 6 860

0

60

Gal

)

T(hour)

Res

idu

eG

al)

Systematic Errors Overall

Systematic effect Bias /μGal Uncertainty /μGal

𝑘𝑒𝑓𝑓 independent 0 1.4

Tilt 0 0.5

Two-photon light shift 66.2 2.6

Coriolis 13.2 3.9

Self gravity -0.1 0.1

Laser frequency 0 0.026

Wave front 0 6

Total 79.3 7.7

Systematic effect Bias /μGal Uncertainty /μGal

𝑘𝑒𝑓𝑓 independent 0 1.8

Tilt 0 0.5

Two-photon light shift 84.3 4.3

Coriolis -17.0 3.9

Self gravity -0.1 0.1

Laser frequency 0 0.026

Wave front 0 6

Total 67.2 8.6

Gravimeter

USTC-AG12

Gravimeter

USTC-AG02

H. –T. Xie, et.al, Analysis of noise and systematic error for a compact and potable atom gravimeter, in preparation

GravimeterTime

(UTC+8)Result(μGal)

Uncertainty(μGal)

Height(m)

ReferenceValue(μGal)

Difference(μGal)

USTC-AG12

2019-01-1700:00

Reported value 980121269.9

15.4 0.957 980121385.9

-116

Corrected value 980121371.3 -14.6

USTC-AG02Reported value 980121268.5

17.0 1.027 980121365.5-97

Corrected value 980121369.9 4.4

• The results with the correction of keff and environmental effects were the corrected values

• The reference values of g were provided by NIM

Corrected Calibration Result

Certificate of Calibration

Outlook

Performance improvement Decrease noise for higher sensitivity Decrease drift for better stability Further evaluate systematic error to reduce uncertainty Build more robust system to improve reproducibility

Engineering improvement Reduce size Decrease weight Lower power consumption Make it easy to use

Thanks for your attention!