[Keita, Sheila, Kiwamu]
We spent hours trying to align the infrared path on the transmon suspension in BSC6. This mission hasn't been completed yet.

Mysterious off-centering at a QPD
There was a mystery which we are not sure at the moment and this currently prevents us from finishing the mission --- one of the two infrared QPDs always had a horizontally off-centered beam on it (by about 5 mm from the center) when every optics else have a well-centered beam. This is quite strange since all the optics in the QPD sled had been well-adjusted in the lab before it was installed in the chamber. Therefore in principle the beam on this QPD must be well-centered too when everyone else is well-centered.
One possible scenario can be due to the fact that we've been using the green light instead of the actual infrared light. There is a 50/50 beam splitter before this QPD and the reflection of the beam splitter is supposed to go to the QPD. But the beam splitter is meant for 1064 nm and thus the HR surface may not be high reflective for 532 nm and the AR surface may be high reflective for 532 nm. In this case the beam splitter can provide such an offset for the beam at the QPD because the beam is reflected off of the AR surface rather than the HR.

A test will be performed in the lab
 In order to test this hypothesis, we are planning to do a simple test in the lab where we measure the reflectivity of the same beam splitter with green light. During this test we don't need to jump in to BSC6 and therefore somebody can work on some vacuum/suspension businesses while we are at the lab.

TMSY damping was not great
The damping of TMSY was not really useful in the sense that it took a fairly long time (~ 20 sec or more) to quiet down the motion every time when the suspension rung up due to our alignment work. Because of this we spent large portion of our time just standing by the suspension and doing nothing. We increased the gain of the servo loops, but it didn't help at all. We suspect that the DOFs are coupling to each other too much. Jeff K. will be taking a look at it when he gets a chance.