Suspension design for GEO 600-an update

Abstract

The GEO 600 gravitational wave detector is currently under construction at Ruthe, near Hannover in Germany. The design of the suspension system for the main mirrors in the detector has been chosen such that thermal noise due to the internal modes of the mirrors is expected to set the sensitivity limit from 50 Hz to ~200 Hz. Thus the design must be such that the effects of seismic noise and thermal noise from the suspensions are lower than the "internal" thermal noise at and above 50 Hz. To achieve this, a triple pendulum suspension incorporating fused silica fibres in the lowest stage forms the major part of the overall suspension and isolation system. In this paper, recent work on developing several aspects of the triple pendulum design is discussed.