georgia.mansell@LIGO.ORG - posted 18:54, Wednesday 01 February 2023 - last comment - 19:31, Tuesday 07 February 2023(67174)
Y arm RH test started
We have started our Y arm ring heater test.
- I turned off the ITMY mode5 damping (nominal gain -0.1) and ETMY mode1 damping (nominal gain 0.1), since these are sensitive modes
- If they look like they start growing we might want to try damping them with these gains first
- I turned on the AWG LINES including intensite noise lines
- We started using the inverse RH filter but don't understand what it was doing so instead manually set the RH powers to 0.4 W on ITMY and 1W on ETMY.
First image shows the HWS spherical power changes from this RH change, in a thermalised state both optics are reading out around 80uD of lensing in the ITM+CP, so reasonably balanced. The RH Y change has increased the differential lensing. Second image shows the increase in frequency noise couplings as we increase the differenital lensing.
We should try reducing the annular CO2Y power next and see if we can bring this back to 80uD of lensing and hopefully reduce the frequency noise coupling again.
I just took the IFO down, because something was causing a ring up in the DCPD_WINDOW channels. None of the fundamental or 1st harmoic violin monitors were ringing up, so this may have been a PI not a violin mode. I think it's probably safer to take the IFO down and watch the violins more carefully tomorow.
This morning I asked the IFO to relock itself. I did initial alignment and noticed that it looks like we could adjust the dark offset on POP A DC to help SRY triggering, or possibly just lower the trigger thresholds.
The IFO locked fine, but we lost lock with a 10 Hz oscillation that showed up in LSC MICH and DARM when we tried to power up to 10W. I've requested CHECK_VIOLINS_BEFORE_POWER_UP and will leave the IFO there until we can investigate the lockloss.
Comparing the change in Y-arm RH to the 13th Jan change to our X-arm RHs (alog66801): Last nights Spherical power reduced by ~24uD for ITMX with 0.4W ring heater change but in January ITMX reduced by 30uD with 0.44W change. These are pretty close..?
Before Sheila preventatively put the IFO in down there was a PI mode ringing up at 10.431kHz (see attached screenshot). This mode was seen in December also.
Second attachment shows the buildups during the lock as the ring heater thermalized. the POP18 took a bit of a hit, AS_A increased, other buildups weren't super interesting.
We were wondering about the phase changes we saw during and after the ring heater test, so I made a quick script which takes the I and Q of a selection of photodiodes and converts them to magnitude and phase. I plotted POPAIR_B_RF18 and RF90, AS_A_RF36, RF72, and RF45 for a "normal" lock, and compared them to a lock where we turned on the Y arm ring heater.
Normal lock is red in the attached plot and the ring heater test is blue.
In the ~5 hours we were locked with the ring heater, the most interesting results are