Jennie W
As per work permit #13412 the SPI laser has been unshuttered using the shutter controller on the floor behind the R4 electronics racks.
This is to monitor SPI alignment as the pumpdown continues and uses powers below 100 mW.
See photo showing the demodulated signals for the Rreference and Measurement SPI interferometers after the laser was unshuttered at 18:08:11 UTC.
After consulting with Jim I set the guardian to take HAM2 and 3 to isolated at 19:23 UTC. They had been damped so this will change the HAM2-3 relative alignment a bit.
This caused HAM 3 tp trip so both ISIs have been taken to DAMPED.
Right ndscope is the QPD on HAM3, you can see the alignment changed massively when it tripped and then went back after both ISIs were taken to DAMPED.
Left ndscope shows the HAM2 QPD which doesn't have a big change between damped -> isolated -> damped.
Here is the plot for the GS13s on HAM3 as it tripped.
The RY blend filter was still set to the CRS damping path BLND7, so I changed it back to the nominal BLND4 path. Even after this change, the ISI was still ringing up.
Looks like the it's the Z loop that is unstable at 14.74Hz (see pictures). Having a good plant measurement will help retune the loop to avoid this ring up. If HAM3 needs to be isolated before then, the Z loop can be ran without the boost filter, which seem to be triggering the instability.
I think this ring up could be due to HEPI being locked on that chamber. I think this happened after the last vent as well. Could be that just adding a notch to the cps low pass will let us isolate the ISI. I will need a little bit of time to do some measurements.