jenne.driggers@LIGO.ORG - posted 10:38, Friday 25 January 2019 (46636)
Locking Notes
- Found IFO trying to acquire DRMI, wasn't well enough aligned to catch. Far enough from catching that normal low-level alignment tweaks weren't getting me close enough, so doing an initial alignment.
- Notable thing: I had to move the PR3 sliders a lot more than usual, and moved both pit and yaw. Often this optic doesn't need touching, but today I moved it by about half a microradian in each pitch and yaw.
- Still couldn't catch even PRMI lock with good flashes. Looked at error signal, and there's nothing there.
- Out on the floor, the REFLAIR_9 RF_In at the demod board was totally loose, and making no electrical connection at all. After I grabbed the torque wrench to tighten it, I had a mini-campaign of checking SMA connections, and several other REFL connections were finger tight but not torqued. All the POP diodes seemed okay.
- I spent some time this morning trying to get a better measure of DHARD_P, while we were in the POWER_30W state.
- First figure, plot_ASC-DHARD_P.png shows the OLG as-is, with several measurements stitched together.
- Second figure, plot_ASC-DHARD_P_new.png shows the same data in blue. In orange, that data is multiplied by a gain factor of 0.9, and FM4 (the less aggressive cutoff filter). You can see that if we didn't lower the gain, we'd ring up an instability by just engaging FM4.
- After these measurements, I let the guardian do LOWNOISE_ASC, which currently has no gain or filter changes for DHARD_P.
- I have by-hand done this, first lowering the gain from -50 to -45, and then engaged FM4.
- Seems good, and I have gone up to NomLowNoise and handed the IFO off to JeffK for some calibration measurements.
- New DHARD_P settings are in the guardian, in LOWNOISE_ASC.
Images attached to this report
