Figure 1

The first three graphics (a-c) show the residual Amplitude Spectral Density (ASD) of displacement in length and angle of the AEI-SAS platforms. All data was measured with the sensors of the SPI. Graphic (a) shows the residual length fluctuations between two platforms, graphic (b) shows the pitch of an individual platform, and graphic (c) shows the yaw of one platform. The AEI-SAS can be used without active control, and its passive performance is shown in blue. It is equipped with inertial and relative displacement sensors to the ground. The residual displacement with feedback control with the internal sensors and actuators applied is represented by the red lines. The feedback control with the SPI sensor input is represented by the yellow lines. An additional SPI sensor is used for an independent measurement and is shown in green and the Root-Mean-Square of it is shown in the dashed green curve. (d) Shows the projection of the suspension point motion for the suspended optical resonator, in the direction of its optical axis, extrapolated from the seismic platform motion. The blue curve shows the expected suspension point motion without a SPI and the purple curve with a SPI. The red, yellow, and green curves show the effects of pitch, yaw, and length of the seismic isolation platforms on the suspension point displacement.