AdV-AEI Squeezer Integration (General)Schreiber, Mehmet, Vahlbruch, Zendri, Ciani, Vardaro, Masserot, Bonnand, Mours, Eisenmann, Sorrentino; Delaurentis, Sequino, ... - 23:45 Wednesday 23 May 2018 (41541)
Print this reportSqueezing: Search for coherent control error signalAfter alignment work, the squeezer was put in squeezing mode and the beam send to the interferometer. To make a long story short, we finally saw the 7 MHz of the squeezer sideband on the B1 photodiode as shown in the figure taking in low-noise_3 mode were the purple line is with the shutter off, blue line with the shutter on.
The amplitude of this 7 MHz line was changing on a few second time scale, probably due to alignment.
No obvious effect on the shot noise level was observed, but the noise level is anyway fluctuating significantly without the squeezer on a few seconds time scale, again probably due to alignment (see the second figure).
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mwas - 10:45 Thursday 24 May 2018 (41547)
Print this reportDuring that time the alignment working point caused a bad common mode rejection.
Figure 1, this results in a large coupling of laser frequency noise, as shown by the ~50% coherence with LSC_PRCL which is an out-of-loop sensing of frequency noise. That coupling is fluctuating in time, the noise floor moves down at the same time as the line at 3345Hz (SSFS line) in B1 moves down in amplitude.
Figure 2, it also visible in the live noise budget, the quantum (shot) noise of the SSFS (laser frequency) sensing is at the same level as the DARM (B1_DC) shot noise.