The two-stage vibration isolation and positioning platform provides passive and active isolation in all directions and translation. It uses a unique combination of position sensors, geophones and ...broadband seismometers to provide unprecedented levels of isolation.
•The paper presents the two-stage vibration isolation and positioning platform used in Advanced LIGO gravitational waves detectors.•The system can support a 1000kg of sensitive equipment and operate in ultra-high vacuum.•Each of the two stages provide passive and active isolation in all directions of translation and rotation (12 axis).•The active control strategy uses a unique combination of relative sensors, geophones and broadband seismometers.•The system reduces the motion to the level of 10−11 m/Hz at 1Hz and 10−12 m/Hz at 10Hz.
New generations of gravity wave detectors require unprecedented levels of vibration isolation. This paper presents the final design of the vibration isolation and positioning platform used in Advanced LIGO to support the interferometer's core optics. This five-ton two-and-half-m wide system operating in ultra-high vacuum. It features two stages of isolation mounted in series. The stages are imbricated to reduce the overall height. Each stage provides isolation in all directions of translation and rotation. The system is instrumented with a unique combination of low noise relative and inertial sensors. The active control provides isolation from 0.1Hz to 30Hz. It brings the platform motion down to 10−11 m/Hz at 1Hz. Active and passive isolation combine to bring the platform motion below 10−12 m/Hz at 10Hz. The passive isolation lowers the motion below 10−13 m/Hz at 100Hz. The paper describes how the platform has been engineered not only to meet the isolation requirements, but also to permit the construction, testing, and commissioning process of the fifteen units needed for Advanced LIGO observatories.
The two-stage vibration isolation and positioning platform (BSC-ISI) provides three orders of magnitude of isolation at all frequencies above 1Hz.
•The paper presents near a decade of research on the ...two-stage twelve-axis vibration isolation platforms developed for Advanced LIGO.•This system positions and isolates 1000kg of very sensitive equipment in all directions of translation and rotation.•The system provides more than three orders of magnitude of isolation over a very large bandwidth.•We show how results from the prototyping phases have been used for the production and commissioning of 15 units.•Isolation results show that the system brings the motion below 10−11m/Hz at 1Hz and 10−12 m/Hz at 10Hz.
This paper presents the results of the past seven years of experimental investigation and testing done on the two-stage twelve-axis vibration isolation platform for Advanced LIGO gravity waves observatories. This five-ton two-and-half-meter wide system supports more than a 1000kg of very sensitive equipment. It provides positioning capability and seismic isolation in all directions of translation and rotation. To meet the very stringent requirements of Advanced LIGO, the system must provide more than three orders of magnitude of isolation over a very large bandwidth. It must bring the motion below 10−11 m/Hz at 1Hz and 10−12 m/Hz at 10Hz. A prototype of this system has been built in 2006. It has been extensively tested and analyzed during the following two years. This paper shows how the experimental results obtained with the prototype were used to engineer the final design. It highlights how the engineering solutions implemented not only improved the isolation performance but also greatly simplified the assembly, testing, and commissioning process. During the past two years, five units have been constructed, tested, installed and commissioned at each of the two LIGO observatories. Five other units are being built for an upcoming third observatory. The test results presented show that the system meets the motion requirements, and reach the sensor noise in the control bandwidth.
The Laser Interferometer Gravitational-Wave Observatory has performed a third science run with much improved sensitivities of all three interferometers. We present an analysis of approximately 200 ...hours of data acquired during this run, used to search for a stochastic background of gravitational radiation. We place upper bounds on the energy density stored as gravitational radiation for three different spectral power laws. For the flat spectrum, our limit of omega0 < 8.4 x 10(-4) in the 69-156 Hz band is approximately 10(5) times lower than the previous result in this frequency range.
High-quality optical resonant cavities require low optical loss, typically on the scale of parts per million. However, unintended micron-scale contaminants on the resonator mirrors that absorb the ...light circulating in the cavity can deform the surface thermoelastically, and thus increase losses by scattering light out of the resonant mode. The point absorber effect is a limiting factor in some high-power cavity experiments, for example, the Advanced LIGO gravitational wave detector. In this Letter, we present a general approach to the point absorber effect from first principles and simulate its contribution to the increased scattering. The achievable circulating power in current and future gravitational-wave detectors is calculated statistically given different point absorber configurations. Our formulation is further confirmed experimentally in comparison with the scattered power in the arm cavity of Advanced LIGO measured by in-situ photodiodes. The understanding presented here provides an important tool in the global effort to design future gravitational wave detectors that support high optical power, and thus reduce quantum noise.
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