GEO Sensitivity and First Results

GEO Sensitivity

The sensitivity of GEO 600 depends on the bandwidth which in its turn depends on the signal recycling factor. The signal recycling of GEO 600 thus provides the opportunity to change the spectral characteristics of the detector response especially those due to the shot noise limitations. By choosing low or high mirror reflectivites of the signal recycling mirror we can selcect a wideband or a narrowband behaviour, respectively. The center frequency of the maximum sensitivity can be tuned to the desired frequency by shifting the signal recycling mirror thus changing the resonance frequency of the signal recycling cavity.

Click on this picture to obtain recent and past sensitivity curves of GEO 600:


GEO/LIGO – First Results

The direct detection of gravitational waves is an issue that necessitates worldwide cooperation. Only a network of detectors provides accurate information on the observables and gives confidence in a claimed detection.

The LIGO Scientific Collaboration (LSC) was founded in 1997 as a forum for organizing research, publication and all other scientific activities in graviational wave research. At present the LSC comprises about 450 scientists from LIGO, GEO 600 and TAMA 300.

In the Fall of 2002 a first common data run (S1) between all three LIGO detectors and GEO 600 was undertaken consisting of 17 days of mostly uninterrupted operation. Since the detectors had not yet achieved the designed sensitivity, the aim was rather to rehearse data acquisition and data analysis.

The results of the analysis of the first data run S1 have been published in 2004 in the Physical Review D. No gravitational waves have been detected, but in all cases new upper limits have been stablished. The papers are also available at the arXiv Preprint Server:

The results of the analysis of the second data run S2 have been published in 2005 in the Physical Review D.

The third LIGO Scientific Collaboration (LSC) science run, S3, was performed between November 1st 2003 and January 9th 2004. The commissioning work produced a stably-locking DRMI only about two weeks before the start of S3, and thus left little time for testing and sensitivity optimization. Therefore it was decided that GEO600 would run for about one week, near the beginning of S3, then go offline to allow time to improve the sensitivity and stability of the detector, and finally rejoin the run.

Thus, the GEO600 S3 science run was divided into two separate periods of time, having somewhat different interferometer configurations and sensitivities. The first ran from November 5th through 11th, and the second, from December 30th to January 13th (a few days after the end of the LSC S3). We refer to these as S3 I and S3 II respectively.

The first publication on the S3 run:

The S4 run was performed during March 2005.

On November 4, 2005 LIGO started the S5 science run with the aim to take data for more than a year. On May 2, 2006 GEO600 joined S5.

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