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| ====Optical Gyroscopes for Ground Tilt Sensing in Advanced LIGO==== | == Optical Gyroscopes for Ground Tilt Sensing in Advanced LIGO == === Introduction === The low frequency isolation of suspensions for Advanced LIGO will be achieved using seismometers, whose signals are fed forward into active hydraulic units (HEPI). The sensitivity of the seismometers to horizontal displacements is good enough to achieve the required isolation. However at very low frequencies, couplings of rotation or ground tilt, into horizontal seismometer signals, become problematic. For a horizontal seismometer the ratio of sensitivity to rotation to sensitivity to horizontal motion is given by: attachment:equation1.png Below some frequency we may expect that the response of the seismometers will become dominated by tilt. |
Optical Gyroscopes for Ground Tilt Sensing in Advanced LIGO
Introduction
The low frequency isolation of suspensions for Advanced LIGO will be achieved using seismometers, whose signals are fed forward into active hydraulic units (HEPI). The sensitivity of the seismometers to horizontal displacements is good enough to achieve the required isolation. However at very low frequencies, couplings of rotation or ground tilt, into horizontal seismometer signals, become problematic.
For a horizontal seismometer the ratio of sensitivity to rotation to sensitivity to horizontal motion is given by: attachment:equation1.png Below some frequency we may expect that the response of the seismometers will become dominated by tilt.