IMC was bypassed.
Right now the IMC is aligned and is flashing with a wrong polarization, and the rerouted MC_REFL beam is on top of the MC transmission but with different polarization. MC transmission is all rejected by Faraday, and only a part of rerouted MC_REFL beam comes out of Faraday, but that beam is strong enough we can see the IM4 transmission all the way down to the ISS diode array.
Details to follow, but anyway conclusion is that HAM2 is ready for ISS diode array work.
PSL and IMC alignment:
At first we couldn't use PZT mirror on the PSL periscope for YAW at all. It turns out that the cables were disconnected and then a wrong cable was connected a few weeks ago. The correct cable was connected back and it was fine.
We followed Cheryl's instruction to install IMC irises to the correct location (see attached for MC1, MC2 and MC3).
Used PZT mirror to direct the beam to the center of MC2 iris, and MC1 iris was fine without doing anything.
Tweaked MC2 to bring the beam to the center of MC3 iris, and IMC started flashing immediately with occational 00 mode without touching MC1.
There was no point spending too much time on tweaking the alignment as this is in-air, so we tweaked only MC3 and stopped when the flashing became mainly of 00, 01 and 02 mode (in YAW).
The flashing light was going into Faraday, and all light was immediately rejected by Faraday (because we were injecting a wrong polarization).
Bypassing IMC:
We installed two temporary mirrors (dirty mounts wiped as good as can be done, iLIGO H2 POP periscope optics, on top of class A base plates) in the MC_REFL path, and directed that beam to MC3 such that the direct reflection off of the MC3 becomes colinear with the flashing. This is Chris-Rodica method in T1300327.
IM1, 2, 3 and 4 were all damped and the offset values were put back.
One person looks at the beams right after MC3, and the other person looks at the beams in front of IM2, and we iterated until we weren't sure if we were making things any better.
Both the MC transmission and rerouted MC REFL went into the Faraday input aperture, only the latter came out (because of the crappy polarization of the latter due to geometric rotation, which works for us in this case).
At this point, we were already able to see the IM4 transmission. Compared with the mark on the wall that Sheila made back in May, YAW was almost good, PIT was not. A small YAW adjustment was made using IM3.
Then we went back to IM1 to center on IM2 (did nothing because it was good), IM2 to center on Faraday output baffle (only adjusted PIT, YAW looked a bit off but OK), then IM to bring the IM4 transmission on the wall back to where it used to be, and after that the beam looked quite well centered on IM4.
We damped PRM, put back the old offset and the IFO REFL beam was on the REFL beam baffle. Since this depends on IM4 angle and PRM angle and since it's a big job to check the angle of IM4, we decided that at this point it was good enough to confirm that the REFL beam clears the REFL baffle hole cleanly with a minor PRM tweaking.
IM4 transmission was going to IM4 trans QPD, however the signal was so small that all we could do is to confirm that the SUM changed when we blocked the beam.
Then we confirmed that the IM4 transmission goes to the pico mirror for the ISS array, reflected and goes to the ISS array.
We need to check the PSL beam mark on the wall, because when the mark was made yesterday by Sheila and Volker, the PZT was not working for YAW.