The Seismic Attenuation System (SAS) for the Advanced LIGO gravitational wave interferometric detectors

New seismic pre-isolation systems will have to be included in the forthcoming gravitational wave interferometers of Advanced LIGO as part of the strategy to increase the sensitivity in the entire frequency range. In this perspective the LIGO Seismic Attenuation System (SAS) Group designed a new kind of seismic attenuation platforms for the Horizontal Access Module (HAM) and Basic Symmetric Chamber (BSC) vacuum chambers of the interferometers. HAM-SAS, a specific prototype for the HAM chambers, was constructed and installed in a test-bench laboratory. At the end of the commissioning time the prototype achieved many of the Advanced LIGO requirements about seismic isolation, stability and reliability. The lab experience also enabled us to finalize the design and indicated SAS as a solution worth considering for the seismic isolation of the advanced detectors.