The search for and registration of the superweak angular ground motions

JINR: J. Budagov, M. Lyablin., G. Shirkov.CERN: J-Ch. Gayde, D. Mergelkuhl

2

Main principle : use reflected laser beam from horizontal surface liquid

θ

ψ

LaserQPR

Original direction of the reflected beam

BaseCuvette with a liquid The surface of the liquidin case of horizontal basis The surface of the liquid

with tilt base

Directionthe reflected beamafter tilt base

The principle of construction of the registration device to measure the seismic slope of the Earth’s surface.

3

Experimental set-up

L

QPr

C

О1

О2

Sensor S

О

SMCF

50 cm

50 cm

•L-laser•QPr-quadrant photodiode•O,O1,O2- bases•SM-semitransparent mirror •C-calibration screw•CF- collimator with changeable focus

frequency internal of 10-4Hz÷1HzThe achieved inclinometer angular precision is 5 10-9 rad

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The inclinometer testsThe angular component of the Earth quake

7,7 7,8 7,9 8,0 8,1 8,2 8,38,0

8,5

9,0

9,5

10,0

10,5Beginning of earthquake7h 50min (Geneva time):26 February 2011

B

Earthquake In Sibiria 26 February 2011; 6h 17min (World time)

A

(r

ad)

Geneva time(h)

0 1 2 3 4 5 6 7 8 9 10 11 12

8,0

8,5

9,0

9,5

10,0

10,5

2rad

(ra

d)

Time(min)

•The Earth quake in Siberia on February 26, 2011•Average amplitude of quake in Siberia was 6.5 units•The distance to Geneva (on the Earth surface) was determined: L=6160km•Calculation time of Earth quake begin Tcalc=6h 21 min in Siberia (world time) practically coincides with the published Tpub=6h 17min (world time)•Amplitude angular oscillations consisted 2 10-6 rad

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Earth surface single oscillation.

0 1 2 32,4

2,6

2,8

3,0

3,2

3,4

3,6

3,8

4,0

4,2

4,4 Measurement 28 Febr. 2012 3h 17min AM

Dev

(rad)

Time (min)

•The observation of an earth surface “single inclination” effect•Amplitude consisted few μrad

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Earth surface oscillations of an industrial noise origin

11 12 131

2

3

4

5

6

7

DC

BA

Dinner time

Dev

(rad)

Time (h)

Industrial origin noise: high activity of auto– traffic,works in the neighboring (with our set-up) Lab room,people movement close to detecting set-up etc.

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Calculation sigma value angular ground motion from industrial noise

-0,8 -0,6 -0,4 -0,2 0,0 0,2 0,40

20

40

60

80

Dev(rad)

N

Mean sd-0,32 0,17

-3,35 -3,30 -3,25 -3,200

10

20

30

Dev()

N

Mean sd-3,28 0,038

Amplitude consisted in work period 0.3 μrad

Amplitude consisted In dinner time 0.04 μrad

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Measurement deformation value concrete floor

0 1 2 311,4

11,5

11,6

11,7

11,8

11,9

12,0

12,1

12,2

12,3

12,4

12,5

0.3 radDev

(rad

)

Time (min)

Concrete floor inclination due to man presence in 3 meters distance from the experimental set-upAmplitude consisted 0.3μrad

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The microseismic peak observation by ground angular motion

0 10 20 30 40 50 60 70 80 90 100 110 1200,04

0,06

0,08

0,10

0,12

0,14

0,16

Dev

(rad)

Time(sek)

The seismogram of an earth surface angular oscillation at the “microseismic peak” frequency

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Fourier analyses oscillation at the “microseismic peak”

0,01 0,1 10,00

0,01

0,02

0,03

0,04

0,05

fd

BA

Am

plitu

de (

rad)

Frequency (Hz)

Amplitude Earth surface oscillation at the “microseismic peak” frequency consist 0.03μrad with frequency fd=0.13HzInclinometer sensitivity estimate on the level of ≈5·10-9 rad

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The long experimental setups space location stability and an earth surface angular oscillations

θmpθmp

Linear accelerator-colliderExperimental Hall

The Earth surface fixed time picture:

surface deformation induced by the standing waves originated by the interference of “microseicmic peak”

Line of horizon

The accelerator-collider positioning on the earth surface deformed by the microseismic peak wave

Different accelerator parts are inclined relative to the ”basic” horizontal

line and consequently particle beams going through the focusing elements

leave them with some angular spread θmp relative to the nominal. As a result it leads to random motion position focus es accelerators

If we can stabilize the angular movements of the accelerator with an accuracy of 10-9nrad we will be able to stabilize position its focuses to within 50 nm

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Conclusion The ground motion was studied by the detection of an earth surface

angular oscillation. Instrumentally method is based on the conceptually new design laser inclinometer using the reflecting surface liquid, as a space stable (horizontal) reference level. The achieved inclinometer measurement precision was experimentally proved to be ≈5·10-9 rad.

The achieved laser inclinometer sensitivity was proved by observation (in Geneva) of:

•Ground 2µrad oscillation caused by the Siberian earth quake (6160 km);

•Single 1÷2 µrad oscillation of origin to be studied;•Industrial origin noise of about 10-7 rad amplitude;•Microseismic peak for the first time recognized as a ground ≈ 10-8rad

angular oscillation at 0.13Hz frequency.The last observed effect if properly “compensated” by adequate

instrumental method could give significant colliders luminosity increase by reduction of beams intersection area to about 50µ level (an estimate) due to some suppression of the lateral focus effect.

The instrument of this sort may happen to be useful for modern high precision research equipment stabilization, for example, of large telescope to reach an extreme resolution with them.