Today we took advantage of some time available during the night shift to perform colored noise injections on the SSFS with the aim of measuring the CMRF as done before O2 and reported in 38675 (attached below some GPS). The data will be processed shortly to derive a new estimation of this parameter.
While we were there, we tried also to exclude trivial and unlikely causes for the change of recycling gain in the PRC experienced after the long break occurred last winter.
- scanned PRCL offset in PRCL_SET = -2e-4,...,1e-4 --> no striking surprise, leave the original PRCL_SET = 0
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moved PR mirror longitudinal position where it was before the break (namely on Sep 23, when we reached 31Mpc) --> recycling gain of the 56MHz seems a bit higher than before (TBC), leave it at Sa_PR_F0_Z = -1200 in the DSP
- in this new working point, we tried to measure again the CMRF by injecting again noise on the SSFS to see if something had changed --> data to be processed
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finally, still sitting there, and following Paolo's indication, we tried to null the alignment signals WI(E)_Y_AA by acting on WI(E)_F0_Y_SET in the DSP cards SaWICD and SaWECD; the purpose being to bring the west arm axis closer to the injected beam axis --> final state is:
- SaWICD card: WI_F0_Y_SET = -200 (was -543)
- SaWECD card: WE_F0_Y_SET = 145 (was 255)
Unfortunately we could not complete the investigation due to a "grey storm" on the DMS at around 23:17 UTC which left us with many servers in red condition and unrestartable from the VPM, (e.g. CoilsSbNE and others). 
ITF_LOCK is paused.
Attached a preliminary SSFS TF for the CMRF measurement in the original working point, more plots and analysis will follow when data and dataDisplay will be back.
During the shift, started at around 19.00 LT, we experienced some locklosses not directly related to our activities, to be investigated.
Interesting GPS are:
CMRF noise injections with original PR and WI/E positions:
1210531145 May16,18-18:39:05 UTC (May16,18-20:39:05 CEST)
colored noise amp 40 200 - 1KHz
1210532161 May16,18-18:56:01 UTC (May16,18-20:56:01 CEST)
colored noise amp 30 10 - 200Hz
Change PRCL offset
1210533183 May16,18-19:13:03 UTC (May16,18-21:13:03 CEST)
1210537038 May16,18-20:17:18 UTC (May16,18-22:17:18 CEST)
CMRF noise injections with new PR position:
1210541246 May16,18-21:27:26 UTC (May16,18-23:27:26 CEST)
colored noise amp 20 10 - 200Hz
1210541796 May16,18-21:36:36 UTC (May16,18-23:36:36 CEST)
colored noise amp 40 200 - 1KHz
