[Yuta, Tega]

We needed to sort out the POXDC signal so we could work on X-arm alignment. Given that POXDC channel value was approx 6 compared to POYDC value of approx. 180, we decided to open the ITMX chamber to see if we could improve the situation. We worked on the alignment of POX beam but could not improve the DC level which suggests that this was already optimized for.  As an aside, we also noticed some stray IR beam from the BS chamber, just above the POX beam which we cold not identify.

Next we moved on to the POP beam alignment, where we noticed that the beam level on LO1 and POP_SM4 was a bit on the high side. Basically, the beam was completely missing the 1" POP_SM4 mirror and was close to the top edge of LO1. So we changed TT2 pitch value from 0.0143 to -0.2357 in order to move the beam position on POP_SM4 mirror. This changed the input alignment, so we compensated using PR2 (0.0 -> 49.0) and PR3 (-5976.560 -> -5689.800). This did not get back the alignment as anticipated, so we moved ITMY pitch from 0.9297 to 0.9107. All of these alignment changes moved the POP beam down by approx 1/5 of an inch from outside the mirro to the edge of POP_SM4 mirror, where about half of the beam is clipped.

Next Steps:

We need to repeat these aligment procedures with say 1.5 time the change in TT2 pitch to center the beam on POP_SM4 mirror.