ITF found in LOW_NOISE_1, the lock lasted since yesterday night. For the planned activity of the day ( ITF tuning ) we tried to reach LOW_NOISE_3, yet the OMC1 weren't able close the loop. I called M. Was (DET Oncall) and thanks to his help we were able to reach the locking state. From 7:40 UTC M. Mantovani and J. Casanueva took care of the tuning, then from around 10:30 UTC L. Aiello worked on improving the sidebands.
After an unlock at 11:54 UTC we faced, like yesterday afternoon, some issues during the lock acquisition related to the SSFS. Also, we had again problems with the OMC1 and we needed M.Was intervention.
ITF left unlocked.
Injection
Under the request of G. Pillant at 10:35 UTC we switched the LNFS to Internal PLL via VPM. The procedure was executed in LOW_NOISE_3 without unlock.
Figure 1 shows MICH, a comb of 1Hz lines disappears when the Internal PLL is engaged around 10:30 UTC, and reappears when the External PLL lock is engaged around 16:00 UTC.
Figure 2 shows spectra just before (purple) and after (before) engaging the internal LNFS PLL. The 1Hz comb disappears from MICH, PRCL and DARM. For DARM it is less clear as other broadband noise is present, but clear the 10Hz part of the comb is gone.
That 1Hz comb is also clear on the SPRB clock and on the B4 112MHz phase, but changing the LNFS PLL doesn't impact these two.
This is due to a cabling mistake done a few weeks ago, which causes the 100 MHz and IRIG-B signal being sent to the LNFS on the same cable instead of separately.
