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Theory of General Relativity predicts the existence of gravitational waves (GW). These are changes in the curvature of space-time propagating with the speed of light. Their origin are accelerated masses. As detectable sources of GW only astrophysical objects or processes are a possibility. Typically they cause relative changes in the distance between test objects of 10-21.
GEO600 is a gravitational wave detector of 600 m armlength which is operated by AEI, Teilinstitut Hannover. Leading detector technology has been developed for GEO600 and is being exported to other GW detector in the world, i. e. LIGO and Virgo. The GEO600 team is also part of the LIGO Science Collaboration which means that data recording and detector blocking for tachnical upgrades are coordinated between the four major site of GW detectors, namely LIGO 1 & 2, Virgo and GEO600 such that at least two (or one) detectors are taking data in parallel. Furthermore, the data taken by these GW detectors are analsysed jointly within this collaboration.
During the last two years the other large gravitational wave observatories in the world have been down for upgrading, and the GEO600 gravitational wave detector has taken science data during the so-called Astrowatch period. From November 2007 to July 2009, a total of 522 days of science data have been collected with a sensitivity within a factor of 2 of the LIGO H2 sensitivity above 500Hz. This data is now being used for triggered burst searches. Together with the GEO S5 data from January 2006 to October 2007, this yields a total of 943 days of GEO science data taken over the last 3,5 years. In parallel to the S5 and Astrowatch activities, we have made tremendous progress in our understanding of the detector noise.
In July 2009, we have started to prepare for the GEO HF upgrade program for the GEO600 detector. In particular, DC readout and tuned signal recycling were implemented and both are now working in routine operations. This combination of DC readout and tuned signal recycling is employed by no other detector but it will be an integral part of both Advanced LIGO and Advanced VIRGO. A very important step here was the development of a novel technique for the generation of stable alignment control signals in GEO. The GEO600 noise curve is now completely explained and no mystery noise remains.
That clears the way for the major upgrade to improve the shot noise limited sensitivity taking place currently: The introduction of squeezed light into GEO600. This will be the first real application of non-classical light in a data taking gravitational wave instrument.
Furthermore, the total circulating light power will also be increased, greatly facilitated by the development of a thermal lensing compensation scheme which uses a thermal light source.
Projects:
Operation and enhancement of a Michelson interferometer at 600 m arm length for the direct detection of GW; a Nd:YAG laser serves as the lightsource, introduction of squeezing light technology to reduce shot noise level, DC readout, tuned signal recycling.
Film about GEO600
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