Passive-performance, analysis, and upgrades of a 1-ton seismic attenuation system

TL;DR

This paper analyzes the performance of a 1-ton seismic attenuation system at AEI, demonstrating its passive isolation capabilities and improvements through tuned dampers to reduce motion across multiple frequencies.

Contribution

It provides a detailed analysis of the AEI seismic attenuation system and introduces tuned dampers to enhance its passive isolation performance.

Findings

Achieves horizontal isolation factor of 400 at 4Hz

Reduces RMS motion between 10-100Hz with dampers

Provides substantial passive isolation at mirror-suspension resonances

Abstract

The 10m Prototype facility at the Albert-Einstein-Institute (AEI) in Hanover, Germany, employs three large seismic attenuation systems to reduce mechanical motion. The AEI Seismic-Attenuation-System (AEI-SAS) uses mechanical anti-springs in order to achieve resonance frequencies below 0.5Hz. This system provides passive isolation from ground motion by a factor of about 400 in the horizontal direction at 4Hz and in the vertical direction at 9Hz. The presented isolation performance is measured under vacuum conditions using a combination of commercial and custom-made inertial sensors. Detailed analysis of this performance led to the design and implementation of tuned dampers to mitigate the effect of the unavoidable higher order modes of the system. These dampers reduce RMS motion substantially in the frequency range between 10 and 100Hz in 6 degrees of freedom. The results presented here demonstrate that the AEI-SAS provides substantial passive isolation at all the fundamental mirror-suspension resonances.