[Anchal, Paco]

Uneloged: yesterday, Paco and Ian tried locking the green laser on Yend to the Y-arm. Nothing noteworthy happened, no luck.

• Started with aligning the green injection to the Iris on table (it was misaligned) and getting it on the ITMY center.
• Then we realized that the beam is going through the focusing leans very offceter. This makes the beam warped and deflected inside that needs to be corrected by mirrors.
• So we decided to adjust the lens position first.
• We realized that lens position is hard to adjust along with keeping the beam hiting ITMY.
• So, we decided to remove the lens first and just align the green beam directly with the Iris on the table and the ITMY center. The beam became as big as ITMY when it reached there without the lens in path. We aligned it to fall on the mirror.
• Then we placed the lens back so that the beam goes through the center of the lens.
• Then we aligned ETMY to get the reflection back to the reflection PD.
• But then when we checked the beam at ITMY again, it was severely missing ITMY. The possible reason is that ETMY is a diverging lens for the beam as well and changing its position changed the beam direction in the beam tube.
• We decided to do another iteration of lens positioning with the new ETMY position. So same steps, removed lens, aligned beam with iris and ITMY, placed back the lens, aligned ETMY again to get reflection back on the PD.
• This time the beam was still reaching ITMY. So we were glad that our iterations converged in 2 repititions.
• Then we aligned ITMY to get counter propagating beam.
• At the end of this alignment:
  • We see dips in relfection photodiode counts from 12200 to 9500.
  • The ETMY oplev is partially out of range (only 1 of the quadrant seeing light) but that could be because we changed the lens position. So Oplev servo is off.
• We confirmed that the PDH servo is properly connected and loop is on. But we see no HOM catching lock for YARM even after us doing about 10 min search with ITMY-ETMY alignments.
• We are leaving things as it is. We'll continue trying to align the cavity tomorrow. Everyone is welcome to try as long as they restore the positions of the optics to a good state at the end.