TITLE: 09/15 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
INCOMING OPERATOR: None
SHIFT SUMMARY:
IFO is in IDLE for CORRECTIVE MAINTENANCE
The mission today was to get to RESONANCE. We got really close!
The idea was that the calculated TR_CARM offset was likey incorrect so we had to step the offset to maintain stability as we went into resonance. So attempts below are all from CARM_TO_5_PICOMETERS.
While sitting in CARM_TO_REFL during handoff, took RF_DARM TF (attached).
I'm stealing Ryan S's format for his IFO troubleshooting today since it was so easy to read! (Thanks Ryan!)
Reference for healthy CARM to RESONANCE transition pre-outage: 2025/09/09 20:01 UTC, GPS: 1441483301
Relocked,
- TR_CARM_OFFSET set -52
- Lockloss ~2-3s into CARM_TO_REFL
- Could be a 5.3 EQ but unlikely
Relocked,
- TR_CARM_OFFSET set -52
- Lockloss ~2-3s into CARM_TO_REFL
- Alignment looked bad judging from INP1_INMON, buildups and AS_AIR so touched PRM to make better, which worked.
- Lockloss at 10s after CARM_TO_REFL, but the state finished
- Conclusion: alignment was still bad and more touching didn't help
Ran Initial Alignment - fully auto
Relocked,
- TR_CARM_OFFSET to -52
- CARM_TO_REFL Successful
- Sheila's advice was to step slowly into RESONANCE with the first line of code and see what happens, which I did
- SRM Saturated at 02:21:18 UTC (attached)
- Lockloss at 02:21:20 (DRMI)
- Looked at OPLEVS but no indication that they saw anything (attached)
Relocked,
- Took DHARD_P SS 2W OLG TF per Shela's instruction - no indication and the measurement didn't really look good due to low coherence. Phase was ok.
- Sheila came online
- TR_CARM_OFFSET to -52
- CARM_TO_REFL reached but PRG unstable
- Lockloss ~3s after
Plan now was to try to step the TR_CARM_GAIN up as we were stepping the TR_CARM_OFFSET down further from -52 to keep the UGF consistent and not cause a LL. Sheila plannd to measure this each time we stepped it.
Relocked,
- TR_CARM_OFFSET to -52, UGF measured, TR_CARM_GAIN to 1.2 (from 1)
- TR_CARM_OFFSET to -53, UGF measured, TR_CARM_GAIN to 1.4
- TR_CARM_OFFSET to -54, UGF measured, TR_CARM_GAIN to 1.7
- TR_CARM_OFFSET to -56, UGF measured, TR_CARM_GAIN to 2.1
- Sheila stepped into resonance by trying to split up the offset reduction (1st line of RESONANCE) but this failed either due to the problem or because there was 0 ramp time
- Lockloss
IFO in IDLE per Sheila's Instruction. We will try again tomorrow.
LOG:
None
Here are two screenshots to show our last attempt last night.
Second one show the TR_REFL 9 erorr signal as we stepped the TR_CARM offset closer to resonance. There is some noise in the TR_REFL9 signal, due to alignment fluctuations coupling when we are not on resonance. As we get closer to resonance by increasing the TR_CARM gain as the optical gain of the side of fringe signal drops, the refl signal gets a little quieter. The offset gets set to zero the error signal right before the handoff, and as you can see the handoff to the error signal works well and the refl 9 signal become quiet once it is in loop. Looking at the TR_CARM signal after the handoff, you can see that the arm powers fluctate because they are now seeing the noise from refl 9 which is now in loop.
When the offset is removed, TR_CARM goes to about 58. All build ups become wobbly when the offset is removed to go to resonance. This means that something seems wrong with the TR REFLAIR9 error signal, which could be due to an alignment problem or an issue with the sensor itself.
