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Reports until 20:09, Friday 08 March 2019
H1 ISC (ISC)
georgia.mansell@LIGO.ORG - posted 20:09, Friday 08 March 2019 - last comment - 03:05, Saturday 09 March 2019(47412)
Afternoon locking notes

DRMI ASC vs Full IFO ASC

We've been having a hard time with the full IFO ASC taking us to a bad alignment and causing locklosses. After a lockloss today I tried doing a WFS relief to a previous time we were at DC readout with good alignment, but even with this alignment we lost lock at engage_asc_for_full_ifo.

I plotted the witness monitors from a time when we survived the ASC engagement, the SRM yaw alignment changes dramatically when we engage the full ASC, as does PRM and IM4 - cyan, brown, and pale yellow in the attachment. Maybe we need to revisit the AS72 phasing?

Bounce-roll mode

A couple of days ago we noted that the LOWNOISE_ASC state took a long time while we waited for the bouce-roll mode to ring down. I raised the threshold for what is "rung up" in the guardian checker, so we could get through quicker. Today we had a lockloss due to the ITMY ITMX and ETMX bounce modes ringing up, so i reverted the checker.

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daniel.brown@LIGO.ORG - 03:05, Saturday 09 March 2019 (47414)

We found that we struggled getting through the locking when DRMI ASC had lower and noisier RF18. Spent some time finding an alignment which got us RF18~75 and that seems to get through much easier. RF18 drops a lot when engaging ASC but the PRG stays constant.

Bounce modes rung up a several times too and caused a few locklosses.

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