The Site: Since S1 (April 2003)
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GEO's successful first Science Run (S1) had been performed without
signal recycling and without the final optics. So the next aim was to
exchange the test optics and to implement signal recycling. The
installation of the signal recycling mirror (T = 1 %)
took place in October. November was spent to lock both recycling
cavities. The SR cavity remained in lock not longer than 2 min.
It became obvious that the radii of curvature of the
endmirrors do not match our demands. So it was very difficult to
obtain a stable lock.
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After installation of the beamsplitter and the endmirrors MNC and MCE
with monolithic suspensions in December, work on dual recycling lock
continued. In January and February 2003, we tried to change the radii
of curvature of the mirrors by means of adaptive optics. A ring-shaped
heater behind the mirror produces a temperature gradient ensuring the
correction of the curvature. With this measure we obtain a near
perfect dark fringe and now continue work on signal recycling.
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Because of these problems we were not able to take part in the second
Science Run (S2 during March and April 2003). At the time being, we
try hard to obtain again long-time stable performance. Our aim is to
take part in the third Science Run as the first detector with dual
recycling and completely monolithic suspensions.
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