Technical Principles
GEO600 Specifications
Armlength, orientation, tube diameter, laser type, laser power, power recycling, optics, signal recycling, frequency range, bandwidth, sensitivity
The Sensitivity of GEO600
The sensitivity of GEO600 depends on the bandwidth which in its turn depends on the signal recycling factor. The signal recycling of GEO600 thus provides the opportunity to change the spectral characteristics of the detector response especially those due to the shot noise limitations.
The Optical Layout of GEO600
The small green arrows indicate beam waists. The greenish rectangles inside the tanks close to the walls are support platforms for the vibration isolation stacks. They restrict the area where the optical components can be placed. The large blue boxes represent the optical tables. Optical components are coloured in a light blue with black borders exept of those which (partially) reflect light, which are drawn in a darker shade of blue. The thickness of the beams is drawn according to their real diameter, whereas the colour of the beams indicate the intensity: the stronger the red of the beam the higher the intensity.
The Cleanrooms of GEO600
The handling of high quality optics requires cleanroom facilities to prevent even microscopic dust particles from entering the system. These dust particles would eventually be attached to the mirror surface and burnt into by the intense laser radiation of about 3 kW/cm2. As the handling of the high quality optics naturally takes place in the vicinity of and even in the tanks at least the surroundings of the tanks have to be of cleanroom quality. We hope to achieve a class <100 cleanroom (during the time a tank is opened) with the help of mobile plastic tents forming a laminar-flow box, large enough to enclose the tank and one or two people working with the optics.
The Vacuum System of GEO600
The vacuum tubes for GEO600 have been manufactured and welded by the Hans Skodock GmbH in Hannover. The basic unit consists of 0.75 m long corrugated pieces of stainless steel with 60 cm diameter, 0.9 mm thickness, and a mass of about 20 kg. Six pieces each are welded at the supplier. After cleaning, these 3 m tubes have been joint together at the site by means of an orbital welding machine. The tubes are suspended at thin steel cables within a trench. The suspension consists of rotating disks mounted on a rail. So the tube can be rotated during welding and pushed into the trench afterwards.
Baffle Positions
The baffles we will use for GEO600 will consist of a conical part (blue in the picture) and a cylindrical part (light green) forming an angle of 25.7 degrees. The total width of a baffle is 14 cm, giving a height of about 3 cm. The surfaces of the baffle will be blackened with an commercial oxidizing stuff called Ebonol (from the japanese company: Enthone-Imasa, German representative: Enthone-Imasa Germany, 40699 Erkrath, Niermannsweg 3-5) to give sufficiently low back-scatter and reflection. The backscatter measured is about 0.1 -1% /sterad depending on the surface roughness of the stainless steel. A direct reflex is not detectable. The multiple reflections at the baffles' blackened surfaces, necessary for the light to return to the mirror will thus sufficiently reduce it's amplitude.
Seismic Measurements in Ruthe
We did some measurements of the seismic motion at the GEO600 site in Ruthe. Most of the measurements were performed in the east end-building at the inner part of the split foundation. We used two accelerometers (Bruel&Kjær big ones) and the corresponding amplifiers (Roland Schilling design). For the measurements below 10 Hz we used additional amplifiers with a gain of 100 to increase the signal above the spectrum analyzer's input noise. By M. Pickenpack and B. Willke
Seismic Noise
Horizontal microseismic noise on the inner part of the split foundation in the E end building at Ruthe, produced by a person, a car, seismic background and electric noise. By David I. Robertson
Data Acquisition System
Here you find programs and tools that can be downloaded from this server as well as some outside links. By Andreas Freise
Interferometer Simulation Software
FINESSE (Frequency domain INterfErometer Simulation SotfwarE)
