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Register a new userStudy of Parametric Instability of gravitational wave detectors using silicon test masses
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Parametric instability is an intrinsic risk in high power laser interferometer gravitational wave detectors, in which the optical cavity modes interact with the acoustic modes of the mirrors leading to exponential growth of the acoustic vibration. In this paper, we investigate the potential parametric instability for a proposed next generation gravitational wave detector based on cooled silicon test masses. It is shown that there would be about 2 unstable modes per test mass, with the highest parametric gain of ~76. The importance of developing suitable instability suppression schemes is emphasized.
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A key action for enhancing the sensitivity of gravitational wave (GW) detectors based on laser interferometry is to increase the laser power. However, in such a high-power regime, a nonlinear optomechanical phenomenon called parametric instability (PI) leads to the amplification of the mirrors vibrational modes preventing the detector functioning. Thus this phenomenon limits the detectors maximum power and so its performances. Our group has started an experimental research program aiming at realizing a exible and active mitigation system, based on the radiation pressure applied by an auxiliary laser. A summary on the PI mitigation techniques will be presented, we will explain the working principle of the system that we are implementing and report about the first experimental results.
Space-based gravitational wave detectors based on the Laser Interferometer Space Antenna (LISA) design operate by synthesizing one or more interferometers from fringe velocity measurements generated by changes in the light travel time between three spacecraft in a special set of drag-free heliocentric orbits. These orbits determine the inclination of the synthesized interferometer with respect to the ecliptic plane. Once these spacecraft are placed in their orbits, the orientation of the interferometers at any future time is fixed by Keplers Laws based on the initial orientation of the spacecraft constellation, which may be freely chosen. Over the course of a full solar orbit, the initial orientation determines a set of locations on the sky were the detector has greatest sensitivity to gravitational waves as well as a set of locations where nulls in the detector response fall. By artful choice of the initial orientation, we can choose to optimize or suppress the antennas sensitivity to sources whose location may be known in advance (e.g., the Galactic Center or globular clusters).
Coincident observations with gravitational wave (GW) detectors and other astronomical instruments are in the focus of the experiments with the network of LIGO, Virgo and GEO detectors. They will become a necessary part of the future GW astronomy as the next generation of advanced detectors comes online. The success of such joint observations directly depends on the source localization capabilities of the GW detectors. In this paper we present studies of the sky localization of transient sources with the future advanced detector networks and describe their fundamental properties. By reconstructing sky coordinates of ad hoc signals injected into simulated detector noise we study the accuracy of the source localization and its dependence on the strength of injected signals, waveforms and network configurations.
The detection of gravitational waves from compact binary mergers by LIGO has opened the era of gravitational wave astronomy, revealing a previously hidden side of the cosmos. To maximize the reach of the existing LIGO observatory facilities, we have
designed a new instrument that will have 5 times the range of Advanced LIGO, or greater than 100 times the event rate. Observations with this new instrument will make possible dramatic steps toward understanding the physics of the nearby universe, as well as observing the universe out to cosmological distances by the detection of binary black hole coalescences. This article presents the instrument design and a quantitative analysis of the anticipated noise floor.
Earth-based gravitational-wave detectors will be limited by quantum noise in a large part of their spectrum. The most promising technique to achieve a broadband reduction of such noise is the injection of a frequency dependent squeezed vacuum state from the output port of the detector, whit the squeeze angle rotated by the reflection off a Fabry-Perot filter cavity. One of the most important parameters limiting the squeezing performance is represented by the optical losses of the filter cavity. We report here the operation of a 300 m filter cavity prototype installed at the National Astronomical Observatory of Japan (NAOJ). The cavity is designed to obtain a rotation of the squeeze angle below 100 Hz. After achieving the resonance of the cavity with a multi-wavelength technique, the round trip losses have been measured to be between 50 ppm and 90 ppm. This result demonstrates that with realistic assumption on the input squeeze factor and on the other optical losses, a quantum noise reduction of at least 4 dB in the frequency region dominated by radiation pressure can be achieved.
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