Suddenly I found that the EX green beam is not clipped much any more by looking at the QPD spectrum, and it turned out that the green beam was totally misaligned. This happened as the EX green QPD centering servo was turned off yesterday, and eventually TMS drifted away.
Anyway, I turned the QPD centering back on, and the clipping was immediately back.
I adjusted the QPD PIT offsets and found that setting QPDA PIT offset to -0.9-ish while keeping QPDB PIT offset to zero-ish fixes the clipping and keeps both of the QPD NSUMs to be about 1.02 to 1.03 (good).
First attachment shows clipping spectra, the second one is after the big offset was set.
Elli took pictures of the green beam in both of these states, and the beam is at a nice position when being clipped, and the beam moves down below by maybe a couple cm or more when it's not clipping.
Since we cannot move TMS up or down, there's not much hope to unclip the beam without drastically off-center the green beam.
Here are two images of ETMx front surface taken with the pcalx camera. The beam is not locked to the arm. (I was having trouble focusing in the low light, but you can still get the picture.)
LHOX_0109 shows the green beam location which we use for locking. The beam is clipping in this configuration.The beam is fairly centered on the optic.
LHOX_0111 shows the beam location when Keita aligned the green beam so that it is not clipping. The beam is aat least a few centimeters below the center of the optic.
