[Sheila, Jennie, Jenne, RyanS, Corey]
We have been able to get PRMI locked (with arms held off resonance using ALS). To do this we:
- Increased POP18 analog whitening gain, and redid its dark offsets
- Phased POP90 by -180 deg. RyanS noticed that POP90 was flashing negative, when it should have been positive. We realized that POP18 was fine because the RF9s didn't need rephasing with the new EOM, but the RF45s needed to be phased by 90 degrees, so the RF90 would need a 180 deg phase.
- Increased REFLAIR_A_RF9 analog whitening gain. No dark offset change needed
- Increased REFLAIR_A_RF45 analog whitening gain and adjusted dark offsets.
- Took the ratio of REFLAIR RF peak heights now vs a time with the same IFO config on Nov 16th 2025, and increased the MICH and PRCL LSC input matrix values by those ratios.
- Jennie calculated what the updated MICH LSC trigger thresholds should be, but with the whitening gain up on POP18 we ended up being okay with the default from guardian.
PRMI locked without too much fuss. Since we've effectively also increased the noise on the error signals, it's a bit delicate, and I lost lock twice while touching up alignment. The third lock I was able to go a bit slower when touching up BS and PRM alignment, and we've now been locked for more than 20 mins (aka infinity). Jennie is taking PRCL and MICH OLGs.
The attached image shows all the things that I had changed.
- POP18 analog gain to 45dB
- POP18 dark offsets
- REFLAIR_RF9 analog gain to 36 dB
- REFLAIR_RF45 analog gain to 30 dB
- REFLAIR_45_Q to MICH input matrix element to 22.7 (5.6x times default of 4.0)
- REFLAIR_9_I to PRCL input matrix element to 18.6 (10.6x times default of 1.75)
Nothing is in guardian (except maybe some trigger thresholds which should be reverted), and nothing is saved in SDF.
I used the lscparams to change the MICH triggers so I shave put these values back.
Below are OLG TFs I ran from userapps/lsc/h1/templates/PRCL and userapps/lsc/h1/templates/MICH
For PRCL the measurement is shown here where blue is the reference measurement in the tenplate, and red and green are the measurements I took today with different injection amplitudes.
We had to raise the injection in PRCL by a factor of 2.5 ti check the wiggles we can see in the gain between 10 to 30Hz are real.
Here is the measurement for MICH. Not sure we understand either of these yet. More investigation to come tomorrow.
Here is an ndscope with the 'good PRMI ACQUIRE time' we were using to scale gains and trigger levels. That is a prmi where we eventually locked and I picked the highest flash that occurred before we did.
