Seismic isolation of optical tables using piezo actuators

Seismic isolation is crucial for gravitational wave detectors as it minimizes ground vibrations, enabling the detection of faint gravitational wave signals. An active seismic isolation platform for precision measurement experiments is described. The table features piezo actuation along five degrees of freedom: three translation and two tip-tilt degrees of freedom. It is stiff in rotation about the vertical axes. A seismometer is used to sense table motion. Piezo actuators are used to suppress seismic noise with feedback control bandwidth of 0.3-3 Hz. Suppression levels ranging from 21 to 36 dB of seismic noise within the frequency range of 0.5-1.3 Hz are demonstrated, as measured by a witness seismometer on the table, with the suppression direction along the optic axis of the suspended mirror on the table. The suppression results in 1 nm/Hz residual horizontal motion at 1 Hz. Limitations such as tilt-to-translation coupling that prevent actuation over the desired frequency range are discussed.