M. Todd, S. Dwyer

We wanted to heat up OM2 and retake an OMC scan to get another measurement to compare against our models, as Sheila had the idea to use the SQZ beam which we know well at ZM5 and measure the overlap to the OMC. We were able to take some data at the very end of the maintanence period but we were having issues for a long time and gave up on having the OM2 hot for the measurement and let it cool down so that relocking could be on time today.

We did all the usual steps of turning the DC centering loops on for the OMs and put the OMC ASC on to center on the QPDs. In the future, here's what we should do.

Step 0 -- Turn on OM2 1hr45min before measurement

Go to IFO_OUT > OM2  and in the input box below "POWER_SET" in the bottom panel, set the power to 4.6. Wait 1hr45min.

Step 1 -- SQZ guardian to LOCKED_SEED_DITHER

Also make sure that there is no IFO power when you go to take your measurement.

Make sure the beam diverter is closed and that the seed launch power is around 75 (if not you may have to pico the half wave plate by going to SQZT0 and clicking on the lambda/2 near "Seed Launch"). Then take the SQZ manager to LOCKED_SEED_DITHER and make sure that OPO locks. You should also take the FC to misaligned, as this was causing flashes in our DCPDs we did not want and were confusing us.

Step 2 -- Open beam diverter and close DC centering

By opening the beam diverter and the fast shutter you should be able to get light on the AS_A and AS_B QPDs so that you can close the DC3 and DC3 centering loops. Then you can take the OMC guardian to OMC ASC and make sure the beam is centered on the OMC QPDs. The NSUM values we saw with the SQZ beam was around 0.001, so there isn't a ton of light on them.

--- You should be able to measure an OMC scan now  ---
If the HG10 peak is really high compared to the OM2 you may try closing the OMC LSC loop and waiting for things to settle before unlocking and remeasuring.

The OMC scans from today were not very good as the HG10 modes were much too high and don't make a good quadratic estimate of the mode-mismatch.