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. Harms, J. Driggers, D. J. McManus, N. Mukund, M. P. Ross, B. J. J. Slagmolen and K. Venkateswara September 4, 2018 1 / 16
Newtonian Noise Implications of Newtonian noise or “gravity-gradient noise” arises from fluctuating dedicated seismometer seismic fields and atmospheric disturbances such as pressure and measurements on Newtonian-noise temperature fluctuations leading to a direct gravitational force on the cancellation for Advanced LIGO test masses. M. Coughlin 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. 2 / 16
Flowchart Implications of dedicated Data (Seismic seismometer measurements on and Tilt) Newtonian-noise cancellation for Advanced LIGO M. Coughlin Seismic Field Newtonian Noise Wiener Filters Newtonian Noise Sub- traction 3 / 16
LHO Corner Station Array Implications of dedicated seismometer measurements on 10 -7 Newtonian-noise cancellation for 17 2 Advanced LIGO Hz] 10 M. Coughlin 11 30 Ground Z, 12.4Hz [(m/s)/ 18 1.5 14 Y-coord [m] 5 13 3 12 19 10 9 6 20 4 1 16 15 0 5 8 27 29 28 22 2 0.5 1 -5 26 23 24 25 -10 -5 0 5 10 15 X-coord [m] 4 / 16
LHO Corner Station Array Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Advanced LIGO M. Coughlin 5 / 16
Flowchart Implications of dedicated Data (Seismic seismometer measurements on and Tilt) Newtonian-noise cancellation for Advanced LIGO M. Coughlin Seismic Field Newtonian Noise Wiener Filters Newtonian Noise Sub- traction 6 / 16
Seismic Velocity Histogram Implications of dedicated seismometer measurements on Newtonian-noise 0.4 cancellation for 10 Hz Advanced LIGO 15 Hz M. Coughlin Probability Density Function 20 Hz 0.3 0.2 0.1 0 0 200 400 600 800 1000 Seismic speed [m/s] 7 / 16
Coherence of the array (all possible pairs) Implications of dedicated seismometer measurements on Newtonian-noise 25 1 cancellation for Advanced LIGO 20 0.8 M. Coughlin 15 0.6 10 0.4 5 0.2 Position [m] < ( . (15Hz)) 0 0 -5 -0.2 -10 -0.4 -15 -0.6 -20 -0.8 -25 -1 -30 -20 -10 0 10 20 30 Position [m] 8 / 16
Flowchart Implications of dedicated Data (Seismic seismometer measurements on and Tilt) Newtonian-noise cancellation for Advanced LIGO M. Coughlin Seismic Field Newtonian Noise Wiener Filters Newtonian Noise Sub- traction 9 / 16
Tiltmeters?!? Implications of dedicated Single horizontal sensor beneath test mass: Seismic sensors are seismometer measurements on sensitive to Rayleigh waves... and Love (shear) waves (non-NN Newtonian-noise cancellation for contributing). Advanced LIGO M. Coughlin 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). 10 / 16
Optimal Tiltmeter Subtraction Implications of dedicated seismometer measurements on Newtonian-noise 0 cancellation for 25 log10(Residual Spectrum / Original Spectrum) Advanced LIGO M. Coughlin 20 -0.5 Number of sensors 15 -1 10 -1.5 5 -2 10 12 14 16 18 20 Frequency [Hz] 11 / 16
Actual Tiltmeter Subtraction Implications of dedicated seismometer measurements on Newtonian-noise 10 0 cancellation for Residual Spectrum / Original Spectrum Advanced LIGO M. Coughlin 10 -1 All Channels Best Channel 10 -2 10 12 14 16 18 20 Frequency [Hz] 12 / 16
Wiener Filter Bode Plots Implications of dedicated seismometer measurements on Newtonian-noise 2 cancellation for Advanced LIGO 4 M. Coughlin 1 5 6 8 Phase [rad] 0 14 19 20 -1 22 23 27 28 -2 29 -3 10 12 14 16 18 20 Frequency [Hz] 13 / 16
Flowchart Implications of dedicated Data (Seismic seismometer measurements on and Tilt) Newtonian-noise cancellation for Advanced LIGO M. Coughlin Seismic Field Newtonian Noise Wiener Filters Newtonian Noise Sub- traction 14 / 16
Tiltmeter-DARM Transfer Function Implications of dedicated seismometer measurements on Newtonian-noise cancellation for Measured Advanced LIGO Tilt to h(t), magnitude [1/rad] NN model 10 -10 M. Coughlin Noise Sus L/P (meas.) Sus L (quad) 10 -12 10 -14 10 -16 5 10 15 20 25 Frequency [Hz] 15 / 16
Other to-dos and conclusions Implications of Highlights: dedicated seismometer We used dedicated measurements at the LIGO Hanford site to measurements on Newtonian-noise predict NN cancellation levels. cancellation for Advanced LIGO We showed how we were able to achieve significant subtraction M. Coughlin 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. 16 / 16
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