Narrow Results

The session on advanced detector research and development was principally focused on ideas and experiments investigating the reduction of thermal noise in suspensions and test masses for interferometric gravitational wave detectors. Recurring themes were the potential use of silicon, cryogenic operation, and methods of fabricating suspensions. With respect to the optical design of future detectors, we learnt about the potential advantages of using non-Gaussian beams, the possibility of optimizing signal-to-noise ratio by tuning the signal recycling cavity, and recent results on squeezing light at frequencies of interest for gravitational wave detection. We look forward to seeing many of these innovative ideas incorporated in future detectors.

In this chapter we describe the designs used for the suspension systems for Advanced LIGO and Advanced Virgo, which support the test masses that serve as the mirrors for the interferometers. These systems are attached to the last stage of the seismic isolation systems for the detectors. Their designs are chosen to minimize thermal noise, residual seismic noise and technical noise, while allowing control of position and orientation of the test masses, and enabling the interferometers to function. Advanced LIGO and Advanced Virgo differ in their approach to seismic isolation and control. Thus, although the final stages of the suspension systems have clear similarities, there are significant differences in the overall suspension systems. Hence we discuss the designs of the two systems separately. In a concluding section we compare the two systems and note that although the two projects have taken different approaches in certain areas, there are key concepts that show similarities and that both designs should meet their requirements.