LIGO Document P1800038-v4

Towards windproofing LIGO: Reducing the effect of wind-driven floor tilt by using rotation sensors in active seismic isolation.

Document #:
LIGO-P1800038-v4
Document type:
P - Publications
Other Versions:
LIGO-P1800038-v1
13 Nov 2018, 16:34
Abstract:
Modern gravitational-wave observatories require robust lowfrequency active seismic isolation in order to keep the interferometer at ideal
operating conditions. Seismometers are used to measure both the motion of the
ground and isolated platform. These devices are susceptible to contamination
from ground tilt at frequencies below 0.1 Hz, particularly arising from windpressure acting on building walls. Consequently, both LIGO observatories suffered significant downtime when wind-speeds were above 7 m/s during LIGO’s
first observation run. We describe the use of ground rotation sensors at LIGO
Hanford Observatory to correct nearby ground seismometers to produce tilt-free
ground displacement signals. The use of these signals for feedforward isolation
enables a robust low-frequency seismic isolation. This allowed the observatory to
operate under wind speeds as high as 15 − 20 m/s during the second observation
run.
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