Electrostatic Actuators

View of the capacitor combs of the electrostatic actuator of GEO600 before assembly.

For calibration and alignment and control purposes one must move the mirrors in interferometric gravitational-wave detectors from random starting positions with very small forces. GEO600 demonstrated the use of electrostatic actuators to drive the main mirrors. An identical three-stage reaction chain 3 millimeters behind the main mirrors carries an interleaving sets of conductive fingers connected to a low-noise electric voltage source. 

The electrostatic actuators used in advanced LIGO are scaled-up versions of the GEO600 design for the more massive 40 kg mirrors in the LIGO instruments.

Relevant publications

1.
M. Hewitson, K. Danzmann., H. Grote, S. Hild, J. Hough, H. Lück, S. Rowan, J. R. Smith, K. A. Strain, and B. Willke
Charge measurement and mitigation for the main test masses of the GEO 600 gravitational wave observatory
Class. Quantum Grav. 24 (2007)
2.
M. Bassan (Ed.)
Advanced Interferometers and the Search for Gravitational Waves
Lectures from the First VESF School on Advanced Detectors for Gravitational Waves (2014)
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