Oli, Camilla, Sheila
Yesterday Camilla noted that she could not restore filter cavity flashes by restoring FC1 pitch top mass osems when the temperature shifted because the HAM5/6 cleanroom was on 89729.
Because we can't look at filter cavity flashes while HAM7 is vented, we rely on retro reflecting the beam off FC1 to point it down the filter cavity.
During this last vent, the cleanroom was turned on Dec 4th, where you can see the tempature rise, the top mass osem shows a shift of -205urad, the bottom mass osem shows a shift of +44 urad. The chamber was vented December 8th, top mass osem shows a shift of +300 urad, bottom mass -77urad. There was another shift in the osems on Decmember 23rd, Oli tracked down that Travis turned on the purge air at this time, top mass osems shift +167 urad, bottom mass osems shift -29 urad. (The top and bottom masses always show different directions, top mass is 4-5 times larger shift than the bottom mass).
We left the FC1 slider at the setting it had in O4, and aligned the new OPO to retro reflect off this alignment. On Jan 20th, 88806, we noticed that the osems said FC1 pointing was different from O4, so we moved FC1 sliders by -175 urad to bring the top mass osems back to where they were in O4. Looking at the bottom osems, this was a shift of -200 urad in the wrong direction, so this attempt to correct for the shifts seen by the top mass actually introduced a larger alignment shift than all of the other changes.
This morning, Camilla and I placed two irises on SQZT7 in the FGCS reflection path. We hope that we can restore FC1 pointing using those irises, and then use that as a reference to check FC1 alingment once we vent. We moved FC1 by 60 urad in either direction and can clearly see the beam clipping on the irises. We turned the cleanroom back on, and will try to see if this can restore the alignment tomorow.
Camilla put FC1 back to it's PIT slider position during the vent, ~50urad, gave us light on SQZT7 IR and the HAM7 WFS, so this is close to reproducing the FC1 alignment that we used during the vent.
So, the conclusion is that my mistake during the vent was to try to use top mass osems to correct for the changes in FC1 alignment.
This morning to get flashes maximized for time that the CR is now off, I moved ZM1 and ZM2 <10urad but moved FC1 P 30 urad, FC2 25urad and ZM3 70urad, plot.
Simular story from Wednesday AM once the CR was turned on, 65urad on FC1 but also 70urad on ZM3, plot.
This might complicate the 89751 plan of just using FC1 to gert flashes back.