AURIGA: results from run1 

 

The first cryogenic run (run1) of the Auriga detector begun in June 1997. The detector operated until November 1999 when a vacuum leakage inside the cryostat forced the warming up and the stopping of the detector.

Follow this link for a step-by-step description of the Auriga detector in run1.

 

In the chart below we show the duty cycle of Auriga during run1. 

                            FIGURA LUCIO: duty cycle vs time
The recorded data cover a fraction of about 80% of the total elapsed time. After removal of periods when a veto is applied (either by the experimenter due to operation on the apparatus, either by the data analysis due to the presence of not modeled noise) the duty cycle (ie the time periods when the detector is sensible) is just 30% of the total time when AURIGA was running.

A sample of the AURIGA sensitivity is shown here: the data show the behavior of the detector over 24 hours. The top plot shows the effective temperature, which is a measure of the detector's sensitivity: it remained around 1mK during the whole day except when experimenter activity, consisting on cryogenic maintenance, disturbed the detector, thus causing a loss in sensitivity recovered after a few hours. The bottom plot shows the sensitivity in the frequency domain: this is actually the typical plot one uses to quote the sensitivity of a gravitational wave detector. The sensitivity Shh is maximum at the mechanical resonances (911Hz and 929Hz). In numbers, the sensitivity during RUN1 was:

During RUN1 the detector has reached a minimum thermodynamic temperature of **K. Actually, a lower temperature could have been reached easily but this has not become a goal since the performance of the detector (both in terms of duty cycle and sensitivity) would have not improved.

The detector data were analyzed in coincidence with the other gw detectors operating worldwide (see the IGEC website for more details): this is essential in order to reduce the false alarm rate and thus increase the confidence in the detection. In the period 1997-1999 the resulting global observatory was sensitive to *** at a Signal-to-Noise Ratio (SNR) of ***: this is equivalent to *** solar masses converted into gw at the center of the Galaxy.

Unfortunately, this sensitivity was not enough to permit a detection of gravitational waves. So, gravitational waves are still an elusive signal, never detected by any instrument.

The reasons for the AURIGA run2 are in the expected sensitivity (and bandwidth) improvement and thus increased detection probability.

 


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