Virgo Logbook

We started the activity by opening the SDB1 Faraday shutter and setting the external SQZ PLL frequency to 7 MHz. With the squeezer set to bright beam mode, we first tried to optimize the BAB alignment on OMC1 by minimizing the amplitude ratio of the 7 MHz beat note on B1s1_PD1 and on B1s2_PD1 photodiodes. Then we unlocked the IMC and misaligned the IMC end mirror, and we scanned the OMC1 temperature to check the BAB mode matching. We found the mismatch to be badly dominated by misalignment, so we restored the initial position of steering mirrors actuators and set the PLL offset frequency back to 0.

Then Henning and Moritz realigned the green pump of the OPO which was previously found to be misaligned. With the source set to squeezed vacuum mode, we tested the effect of injecting squeezed vacuum in the ITF. In the attached plot of Hrec spectrum, purple trace refers to the sensitivity without SQZ, blue trace is with SQZ. No coherent control was active during the test, i.e. the SQZ phase was random and so we observed on average the dominant effect of anti-squeezing. In addition, we have no precise estimate of optical losses during the test. Nevertheless the effect on quantum noise is clearly visible.