Speaker
Description
In order to extend the detection bandwidth at low frequency, the Einstein Telescope will require to use large cryogenic mirrors, mounted on a ultralow frequency seismic isolation stage. ET-CRISTAL is developing a full scale prototype of large silicon mirror isolated from low frequeny seismic motion. The isolation strategy proposed uses a hybrid approach, combining an active isolation platform, on which is installed a large inverted pendulum. It results in a compact design, which has been shown to fulfill ET-LF DARM specifications.
This unique configuration actually takes the best of existing gravitational wave detectors seismic isolation systems, and provide a number of key features. Thanks to the active platform, the residual RMS noise can be decreased in the sub-Hertz frequency range without compromising the compliance. On one hand, the interted pendulum is an excellent reference allowing to keep the alignment of the active platform. On the other hand, the active platform helps to align the inverted pendulum, and to control its resonances.
The presentation starts with an explanation of the basic principle of this hybrid isolation concept, and then continues with some details about the mechatronic architecture and control design specificities. Finally, latest performance obtained so far will be presented, and correleted with theoretical predictions.