Seismic Isolation of Optical Tables Using Piezo Actuators

TL;DR

This paper presents an active seismic isolation platform for optical tables using piezo actuators, achieving significant noise suppression in the 0.5 to 1.3 Hz range to enhance precision measurements like gravitational wave detection.

Contribution

It introduces a novel active seismic isolation system with piezo actuators along five degrees of freedom, demonstrating effective seismic noise suppression in a relevant frequency range.

Findings

Achieved 21 to 36 dB seismic noise suppression between 0.5 and 1.3 Hz.

Residual horizontal motion of 1 nm/√Hz at 1 Hz was measured.

Identified limitations due to tilt-to-translation coupling affecting actuation range.

Abstract

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 translational actuations and two tip-tilt degrees of freedom along the horizontal axes. 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 to 3 Hz. Suppression levels ranging from 21 to 36 dB of seismic noise within the frequency range of 0.5 to 1.3 Hz are demonstrated, as measured by a witness seismometer on the table, with the suppression direction along the axis of the longitudinal translation of the suspended mirror on the table. The suppression results in 1 $\mathrm{\mathrm{nm/\sqrt{Hz}}}$ residual horizontal motion at 1 Hz. Limitations such as tilt-to-translation coupling that prevent actuation over the desired range of 0.03 to 3 Hz are discussed.