Search

Correlated magnetic noise in the form of Schumann resonances could introduce limitations to the gravitational-wave background searches of future Earth-based gravitational-wave detectors. We consider recorded magnetic activity at a candidate site for the Einstein Telescope, and forecast the necessary measures to ensure that magnetic contamination will not pose a threat to the science goals of this third-generation detector. In addition to global magnetic effects, we study local magnetic noise and the impact it might have on co-located interferometers. We express our results as upper limits on the coupling function of magnetic fields to the interferometer arms, implying that any larger values of magnetic coupling into the strain channel would lead to a reduction in the detectors' sensitivity. For gravitational-wave background searches below $\sim 30$ Hz it will be necessary for the Einstein Telescope magnetic isolation coupling to be two to four orders of magnitude better than that measured in the current Advanced LIGO and Virgo detectors., Comment: May 30th 2022 - New version contains updated figures in agreement with erratum: https://doi.org/10.1103/PhysRevD.105.109904

The first twenty years of operation of gravitational-wave interferometers have shown that these detectors are affected by physical disturbances from the surrounding environment. These are seismic, acoustic, or electromagnetic disturbances that are mainly produced by the experiment infrastructure itself. Ambient noise can limit the interferometer sensitivity or potentially generate transients of non-astrophysical origin. Between 1 April 2019 and 27 March 2020, the network of second generation interferometers&mdash, LIGO, Virgo and GEO&mdash, performed the third joined observing run, named O3, searching for gravitational signals from the deep universe. A thorough investigation has been done on each detector before and during data taking in order to optimize its sensitivity and duty cycle. In this paper, we first revisit typical sources of environmental noise and their coupling paths, and we then describe investigation methods and tools. Finally, we illustrate applications of these methods in the hunt for environmental noise at the Virgo interferometer during the O3 run and its preparation phase. In particular, we highlight investigation techniques that might be useful for the next observing runs and the future generation of terrestrial interferometers.