In order to compare with previous measurements before the WE replacement (https://logbook.virgo-gw.eu/virgo/?r=65254) I have made this morning scans of the OMC with SR aligned and misaligned (initially planned for yesterday evening). The data analysis and comparison with previous scans of the SDB1 OMC and the EDB OMC remains to be done.

Figure 1 One thing that I have noticed is that when misaligning SR in CARM NULL 1F around 07:40 UTC, the power on B4 (carrier recycling gain) has increased. Which would mean that the effect of the point absorber, even with the beam off-center on WE depends on signal recycling, and with signal recycling misaligned the losses due to the point absorber are smaller.

Measurements times

06:06 UTC - OMC scan start in CARM NULL 1F (20min after lock)
unlock near the end of the scan

relock, SR_TY steady around -225.0 wihle SR/BS TX moving (due to the
mis-centering on WE), starting to add offset on SR_TY while the other
transients are ongoing. But SR TY moved -225.4 just before that, so using that as a reference of aligned SR to add ~2urad of misalignment to.

7:25 UTC, SR_TY_SET = 0.3
7:28 UTC, SR_TY_SET = 0.5
7:30 UTC, SR_TY_SET = 0.15 to stabilize at SR TY = -224

7:33 UTC - OMC scan start with SR misaligned
7:40-7:44 increase SR_TY_SET to 0.25 and then reverted to 0.2 to recover DCP around 190Hz and lower B1p power
Overshoots to DCP of ~150Hz, continously adjusting the SR TY offset to try to stay around 190Hz.

08:04 restoring SR alignment