camilla.compton@LIGO.ORG - posted 10:25, Monday 17 June 2024 (78486)
Checked SQZ OPO ISS, no noise added this morning, but increased noise since O4 break
Sheila, Camilla
Last week we saw that when the OPO ISS was off, squeezing improved: 78445. This worried us, but we repeated this morning 15:33 - 15:41UTC and saw what is expected: sqz got worse without OPO ISS.
Plots from sqz/h1/Templates/dtt/SQZ_ISS_inloop_noises.xml of 2023 reference, SQZ ISS ON and OFF attached.
Sheila suggested that what happened on June 14th was that SQZ OPO temperature or angle wasn't well tuned for the green OPO power, when the OPO ISS as off, the SHG launch power dropped from 28.8mW to 24.5mW. it was just chance that SQZ was happier here. Since Saturday we've been injecting ~25.5mW 78467.
While looking at this, you can see the SQZ-OPO_TRANS_LF signal has got more noisier since the January break in the 0-60Hz region. Plot here. Maybe this is expected from the PMC install?
Images attached to this report
