Abstract :
The last few years have brought a great break-through in the quest for earth-bound detection of gravitational waves: on five sites, but so far all on the northern hemisphere, detectors of armlengths from 0.3 to 4 km are being built. These projects have in common that one prominent noise source, the shot noise, is reduced by the use of power recycling. The British-German project GEO 600, although only intermediate in size (600 m), has good chances for a competitive sensitivity by using advanced optical technologies early on. Particularly the use of the so-called signal recycling will allow to search for faint sources of only slowly varying frequency (pulsars, close binaries). The talk will describe the particular GEO 600 interferometer topology, characterized by the use of a four-pass delay line and signal recycling. The major noise sources, particularly shot noise (also prominent in LISA) and thermal noise (a lesser concern in LISA), will be discussed, and the experimental effort aiming at their reduction. The projected sensitivity of GEO 600 is given for the examples of broad-band and narrow-band operation. The current status of the construction of GEO 600 will be outlined (civil engineering, vacuum, optics). First operation of GEO 600, like that of other ground-based interferometers, is expected around the years 2000/2001.
