Ho Jung PaikDepartment of Physics, University of Maryland

8th Japan-Korea Joint WorkshopJune 27, 2015

Newtonian Noise Mitigationwith Tensor Gravitational Wave

Detector

Paik 2

Superconducting tensor gravitational wave detector

SOGRO (Superconducting Omni-directional Gravitational Radiation Observatory)

Rayleigh NN must be mitigated by 102 at 0.1 Hz for SOGRO 1 Infrasound NN must be mitigated by 103 at 0.1 Hz for SOGRO 1.

Paik 3

Newtonian gravity noise Seismic and atmospheric density

modulations cause Newtonian gravity gradient noise.

At 0.1 Hz, s ~ 35 km >> L. Gravity gradient noise L. Detecting and removing the gravity gradient noise appears to be very challenging.

GWs are transverse and cannot have longitudinal components whereas the Newtonian gradient does.

GW could be distinguished from near-field gradients, if all the tensor components are detected.

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Paik 4

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NN due to Rayleigh waves Metric perturbation tensor in the source frame:

Paik 5

Removal of Rayleigh NN

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With tensor + vertical CM (0 noise)

With tensor (SNR 103)+ vertical CM (SNR 106)+ 7 seism (5 km, SNR 103)

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Paik 6

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With tensor + 15 mikes (0, 0.6, 1 km, SNR 104)

Is there any way that we can mitigate NN by using the tensor channels alone?

Infrasound waves come from half space with an additional unknown: polar angle of incidence .

Microphones are required to measure the air density fluctuations.

Satisfies SOGRO 1 requirement

Paik 7

NN mitigation by correlation? Rayleigh and infrasound waves incident in different angles

are uncorrelated with each other and with the GW signal. This allows us to determine autocorrelations of h+() and h()

by combining correlations of various tensor outputs.

Fourier transform of autocorrelation is power spectral density.

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Problem: It takes a long time to mitigate the NN by using correlation method.

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Paik 8

Could SOGRO help advanced detectors mitigate NN? (HW from R.

Weiss)

Newtonian noise

Worthy mitigation goal: A factor of ~10 to 10-23 Hz-1/2 at 10 Hz and 10-21 Hz-1/2 at 1 Hz.

Worthy mitigation goal

Paik 9

KAGRA sensitivity curve

The low-frequency noise of KAGRA could benefit from a similar NN rejection.

Paik 10

Sensitivities to GW and NN

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Paik 11

Incomplete correlation of NN Mitigation factor S is given by the correlation CSN between

the detector and the NN sensor:

Beker et al., GRG 43, 623 (2011)

It is much more challenging to mitigate the NN of ground detectors.

Paik 12

Mini-SOGRO with 5-m arm length

Mini-SOGRO with L = 5 m, M = 1 ton, T = 0.1 K could mitigate the NN at 1-10 Hz by a factor 5. NN mitigation appears very challenging but not impossible.

L = 5 m, M = 1 t, T = 0.1 K, Q = 109, n = 2, fD = 1 Hz