Newtonian-noise reassessment for the Virgo gravitational-wave observatory including local recess structures

Abstract

The LIGO and Virgo scientific collaborations have cataloged ten confident detections from binary black holes and one from binary neutron stars in their first two observing runs, which has already brought up an immense desire among the scientists to study the universe and to extend the knowledge of astrophysics from these compact objects. One of the fundamental noise sources limiting the achievable detector bandwidth is given by Newtonian noise arising from terrestrial gravity fluctuations. It is important to model Newtonian noise spectra very accurately as it cannot be monitored directly using current technology. In this article, we show the reduction in the Newtonian noise curve obtained by more accurately modelling the current configuration of the Virgo observatory. In Virgo, there are clean rooms or recess like structures underneath each test mirror forming the main two Fabry-Perot arm cavities of the detector. We compute the displacements originating from an isotropic Rayleigh field including the recess structure. We find an overall strain noise reduction factor of 2 in the frequency band from 12 to about 15 Hz relative to previous models. The reduction factor depends on frequency and also varies between individual test masses.

Application of Spatio-Temporal Spectral Analysis for Detection of Seismic Waves in Gravitational-Wave Interferometer

“…of a wave that passed through the measuring system during the considered time period. Notably, Rayleigh surface waves are expected to prevail in the seismic wavefield in the vicinity of the Virgo west-end building [32]. Therefore, we can neglect vertical differences between the spatial positions of the seismometers (z axis).…”

Application of space-time spectral analysis for detection of seismic waves in gravitational-wave interferometer

“…Thanks to that we can obtain length, direction, frequency and amplitude 4 of every wave that passed through the measuring system during the considered time period. Notably, Rayleigh surface waves are expected to prevail in the seismic noise in the vicinity of the Virgo building [38]. Therefore, we can neglect vertical differences between the spatial positions of the seismometers (z axis).…”

Advanced Virgo: Status of the Detector, Latest Results and Future Prospects

“…Accurate measurements from seismometer arrays and tiltmeters are needed to model the seismic motion in order to perform an effective noise cancellation [93,94]. A recent work [95] shows that NN in Virgo is suppressed by about a factor of two at 15 Hz by clean rooms and recesses underneath the test masses, suggesting that the infrastructural design could have a strong impact in NN mitigation. In Advanced LIGO and Advanced Virgo the NN starts to be relevant only under 20 Hz just near the lower limit of the detector band, nevertheless NN suppression will be mandatory both for the next version of the current detectors and for the next detector generations which will extend the frequency range towards the 1 Hz region [96].…”