Abstract
We describe a new geometry for electrostatic actuators to be used in sensitive laser interferometers, suited for prototype and table top experiments related to gravitational wave detection with mirrors of 100 g or less. The arrangement consists of two plates at the sides of the mirror (test mass), and therefore does not reduce its clear aperture as a conventional electrostatic drive (ESD) would do. Using the sample case of the AEI-10 m prototype interferometer, we investigate the actuation range and the influence of the relative misalignment of the ESD plates with respect to the test mass. We find that in the case of the AEI-10 m prototype interferometer, this new kind of ESD could provide a range of 0.28 μm when operated at a voltage of 1 kV. In addition, the geometry presented is shown to provide a reduction factor of about 100 in the magnitude of the actuator motion coupling to the test mass displacement. We show that therefore in the specific case of the AEI-10 m interferometer, it is possible to mount the ESD actuators directly on the optical table without spoiling the seismic isolation performance of the triple stage suspension of the main test masses.
Highlights
Since the force that may be obtained per applied voltage of this setup is smaller than for the conventional electrostatic drive (ESD) configuration, this type of ESD is mainly suited for the case of light ( 100 g ) mirrors such as in the AEI-10 m prototype interferometer or in the Glasgow speedmeter proof of principle experiment
The exact frequency range and expected rms actuation voltage of the ESDs will depend on the properties the aforementioned other actuators, as well as on the specific implementation of the longitudinal length control scheme
We presented a novel type of ESD for longitudinal test mass actuation in prototypes and table top interferometers in the field of gravitational wave detectors
Summary
Interferometric gravitational wave detectors, such as GEO 600 [1], advanced LIGO (aLIGO) [2], Advanced Virgo [3] and KAGRA [4] are large laser interferometers with the mirrors/test masses hung at the bottom of multi-stage pendulum chains. For the operation of these detectors, it is necessary to have low-noise, contact-free actuators for controlling the longitudinal and angular degrees of freedom of the mirrors. The ESD on the reaction mass needs its own seismic isolation to avoid the coupling of ground motion to the seismically isolated test mass It is hung as the lowest stage of a multi-stage pendulum, which again requires its own sensors and actuators for alignment and damping of the reaction mass. One particular issue that may introduce noise is squeezed film damping that arises due to residual gas in between the test- and reaction mass [6] This conventional type of ESD reduces the possible free aperture in transmission. Since the force that may be obtained per applied voltage of this setup is smaller than for the conventional ESD configuration, this type of ESD is mainly suited for the case of light ( 100 g ) mirrors such as in the AEI-10 m prototype interferometer or in the Glasgow speedmeter proof of principle experiment
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