Development of optimal combination of passive and active vibration damping
Ground vibrations are a major source of noise in laser interferometer gravity wave detectors located at or in the Earth's surface. Seismic environmental noise, caused by natural micro-seismicity and human activities, is thought to cause displacements of the interferometer optics ten orders of magnitude greater than the effect expected from gravitational wave signals. For this reason, seismic isolation systems are used as a mechanical interface between the environment and the detector optics.
Go to the description of the R&D issue (December 2023, in Dutch)
Seismic isolators are Ultra-High Vacuum (UHV)-compatible complex mechatronic systems that perform the main functions: Slow large-scale positioning and alignment; suppressing vibration noise below sensitivity requirements in the detector observation band (10 Hz-10 kHz for current-generation interferometers such as LIGO and VIRGO); reducing the overall RMS motion of each suspended optical element, particularly the contributions from suspension resonances and oceanic micro-seismic peaks.
Go to the R&D opening text vibration damping (in Dutch, April 2024)
In the Einstein Telescope, extending the observation band of gravitational waves to 3 Hz poses serious technological challenges by requiring a performance improvement of several orders of magnitude over state-of-the-art low-frequency vibration isolation techniques. Crucial to reducing excess coupling noise - when controlling the interferometer's global degrees of freedom (longitudinal and angular alignment) - is the suppression of the residual RMS motion of the detector's core optics down to the nanometer level.
Achieving the requirements for the ET suspensions will be achieved through new mechanical designs/configurations of seismic isolators, the development of improved inertial and relative motion sensors, and the implementation of advanced control systems.
Key challenges in a nutshell:
- Optimization of residual RMS motion values by applying advanced control methods and algorithms, designs for production;
- Relative motion sensors with ultra-low noise for damping resonances in the suspension system;
- Rotational inertial sensors with ultra-low noise for active rotation isolation;
- Seismic isolators for auxiliary optics: development of a standardized modular technical design, prototyping;
- Interferometric optical links to implement low-frequency tracking between supporting auxiliary and core optics and for stray light suppression;
- Active vibration isolation systems for in-air laser optical benches.
Goals:
Einstein Telescope use purpose:
Extending the gravitational wave observation band to 3 Hz!
(10Hz-10kHz for current generation interferometers such as LIGO and VIRGO)
Engineering goal | Seismic isolation systems:
Proposed direction; slow large-scale positioning and alignment;
- New mechanical designs/configurations of seismic isolators;
- Development of improved inertial and relative motion sensors;
- Implementation of advanced control systems.
Wanted results:
- Suppressing vibration noise below sensitivity requirements in the desired detector observation band. (A few orders of magnitude better than currently known low-frequency vibration isolation techniques);
- Reducing the overall residual RMS motion of any suspended optical element, particularly the contributions of suspension resonances and oceanic micro-seismic peaks.