Commissioning of the GEO600 gravitational wave detector

During the last decade an international network of large scale interferometric gravitational wave detectors, based on kilometre long Michelson interferometers, has been constructed to pioneer a new window to the universe: Gravitational Wave Astronomy.

One of the most advanced instruments is the British/German gravitational wave detector GEO600 [1], [2] located near Hannover, Germany. Pushing the sensitivity of this interferometer to the limit results in a highly complex experiment, consisting out of about 300 partly coupled control loops. The core of the detector comprises about 30 high quality optics, suspended by multi-stage vibration isolations and enclosed by an ultra high vacuum system of a volume of about 400 cubic meters. The alignment systems of GEO600 automatically controls 38 angular degrees of freedom. Each day about 100 gigabytes of science data are being collected and processed.

[GEO600 Cleanroom]

The complexity of modern gravitational wave detectors requires experienced scientists and a long phase of optimisation until all subsystems operate at their technical limit. Often year-long periods of intense commissioning work (during which the sensitivity of the instrument improves by several orders of magnitude [see figure below]) are required, before a gravitational wave detector can provide sensitive and well understood science data.

[GEO600 Sensitivity]

Our group has a wide experience in commissioning of ground based gravitational wave detectors [3-5] and is actively participating in the commissioning of the GEO600 detector. We currently focus on the optical technology (Interferometry, Signal-Recycling, optical readout, squeezed light) and simulations (see GEO Simulation Group).

The next steps in the commissioning of the GEO600 detector are: Modelling of noise couplings to guide future improvements Realisation of DC-readout (homodyne detection) with tuned Signal-Recycling Implementation of squeezed light R&D for GEO-HF