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Nov 23, 2023 32 likes •196 views

Implications of dedicated seismometer measurements on Newtonian-noise Implications of dedicated seismometer cancellation for Advanced LIGO M. Coughlin measurements on Newtonian-noise cancellation for Advanced LIGO M. W. Coughlin, J.

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Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. W. Coughlin, J. Harms, J. Driggers, D. J. McManus, N.

Mukund, M. P. Ross, B. J. J. Slagmolen and K. Venkateswara September 4, 2018

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SLIDE 2

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Newtonian Noise

Newtonian noise or “gravity-gradient noise” arises from fluctuating seismic fields and atmospheric disturbances such as pressure and temperature fluctuations leading to a direct gravitational force on the test masses. LIGO Hanford → Caltech/Hanford/GSSI. Virgo WEB → Poland/GSSI. Homestake (3D array) → Caltech/Minnesota. Seismic NN modeling → Nikhef/GSSI. Atmospheric NN modeling → APC/GSSI. I am only worried about the seismic field portion in the following.

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SLIDE 3

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Flowchart

Data (Seismic and Tilt) Seismic Field Newtonian Noise Wiener Filters Newtonian Noise Sub- traction

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SLIDE 4

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

LHO Corner Station Array

1 2 3 4 5 6 8 9 10 11 12 13 14 15 16 17 18 19 20 22 23 24 25 26 27 28 29 30

5 10 15

X-coord [m]

5 10

Y-coord [m]

0.5 1 1.5 2 Ground Z, 12.4Hz [(m/s)/ Hz] 10-7

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SLIDE 5

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

LHO Corner Station Array

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SLIDE 6

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Flowchart

Data (Seismic and Tilt) Seismic Field Newtonian Noise Wiener Filters Newtonian Noise Sub- traction

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SLIDE 7

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Seismic Velocity Histogram

Seismic speed [m/s]

200 400 600 800 1000

Probability Density Function

0.1 0.2 0.3 0.4

10 Hz 15 Hz 20 Hz

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SLIDE 8

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Coherence of the array (all possible pairs)

Position [m]

10 20 30

Position [m]

5 10 15 20 25

<(.(15Hz))

0.2 0.4 0.6 0.8 1 8 / 16

SLIDE 9

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Flowchart

Data (Seismic and Tilt) Seismic Field Newtonian Noise Wiener Filters Newtonian Noise Sub- traction

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SLIDE 10

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Tiltmeters?!?

Single horizontal sensor beneath test mass: Seismic sensors are sensitive to Rayleigh waves... and Love (shear) waves (non-NN contributing). Multiple vertical sensors: Requires an array some distance from test-mass with relatively weak correction with test-mass acceleration Single tiltmeter beneath test mass: Not sensitive to Love waves so... no problem (theoretically).

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SLIDE 11

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Optimal Tiltmeter Subtraction

Frequency [Hz]

10 12 14 16 18 20

Number of sensors

5 10 15 20 25

log10(Residual Spectrum / Original Spectrum)

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SLIDE 12

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Actual Tiltmeter Subtraction

Frequency [Hz]

10 12 14 16 18 20

Residual Spectrum / Original Spectrum

10 -2 10 -1 10 0

All Channels Best Channel

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SLIDE 13

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Wiener Filter Bode Plots

Frequency [Hz]

10 12 14 16 18 20

Phase [rad]

1 2

4 5 6 8 14 19 20 22 23 27 28 29

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SLIDE 14

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Flowchart

Data (Seismic and Tilt) Seismic Field Newtonian Noise Wiener Filters Newtonian Noise Sub- traction

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SLIDE 15

Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Tiltmeter-DARM Transfer Function

5 10 15 20 25

Frequency [Hz]

10-16 10-14 10-12 10-10

Tilt to h(t), magnitude [1/rad]

Measured NN model Noise Sus L/P (meas.) Sus L (quad)

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Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO

M. Coughlin

Other to-dos and conclusions

Highlights: We used dedicated measurements at the LIGO Hanford site to predict NN cancellation levels. We showed how we were able to achieve significant subtraction in line with expectations based on correlation measurements. We showed that significant subtraction is achievable with only a few seismometers. Future extensions: Calculation of optimized arrays in inhomogeneous seismic fields without constraints on seismometer locations. Calculate the best sensor locations from correlation measurements (to reach ultimate cancellation limits for a given number of sensors) Devise the strategy to optimally pick sensors in a large underground array.

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