[Paco, Yuta]

We have increased the output power from the PSL table to 951 mW (it was 96.7 mW).
IMC was recovered including WFS, and both arms are flashing nicely in IR.
We tweaked the alignment of GRX and GRY injection to align them with IR, but it was hard.
Right now IR beams are not centered on TMs. We should center them first.

What we did:
Power increase and IMC recovery
 - Replaced a beam splitter which splits the beam into IMC REFL RF PD path and WFS path from R=98% to R=10% one. Reflection goes to RF PD.
 - Put a R=98% beam splitter back into WFS path.
 - We also tried to put a window in front of IMC REFL camera to recover the arrangement in 40m wiki, but the beam reflected from the window was too weak for us to align. So, we decided not to place a window in front of the camera.
 - Attached photos are the IMC REFL path before and after the work.
 - Measured the PSL output power as Koji did in elog 40m/16672. It was measured to be 96.7+/- 0.5 mW.
 - Rotated the HWP using the Universal Motion Controller (it was not possible for us to do it from the MEDM screen). The position was changed from 73.99 deg to 36.99 deg. Output power was measured to be 951 +/- 1 mW
 - IMC locked without any other changes.
 - Changed C1:IOO-WFS_TRIGGER_THRESH_ON to 5000 (was 500). IMC WFS also worked.
 - After running MC WFS relief script, WFS DC offsets and RF offsets are adjusted following the steps in elog 40m/16835. Below are the results.

C1:IOO-WFS1_SEG1_DC.AOFF => -0.0008882080010759334
C1:IOO-WFS1_SEG2_DC.AOFF => -0.0006527877490346629
C1:IOO-WFS1_SEG3_DC.AOFF => -0.0005847311617496113
C1:IOO-WFS1_SEG4_DC.AOFF => -0.0010395992663688955
C1:IOO-WFS2_SEG1_DC.AOFF => -0.0025944841559976334
C1:IOO-WFS2_SEG2_DC.AOFF => -0.003191715502180159
C1:IOO-WFS2_SEG3_DC.AOFF => -0.0036688060499727726
C1:IOO-WFS2_SEG4_DC.AOFF => -0.004011172490815322

IOO-WFS1_I1         :  +1977.7 ->    +2250 (Significant change)
IOO-WFS1_I2         :  +3785.8 ->  +3973.2
IOO-WFS1_I3         :  +2014.2 ->  +2277.7 (Significant change)
IOO-WFS1_I4         :  -208.83 ->  +430.96 (Significant change)
IOO-WFS1_Q1         :  +2379.5 ->  +1517.4 (Significant change)
IOO-WFS1_Q2         :  +2260.4 ->  +2172.6
IOO-WFS1_Q3         :  +588.86 ->  +978.98 (Significant change)
IOO-WFS1_Q4         :  +1654.8 ->  +195.38 (Significant change)
IOO-WFS2_I1         :  -1619.9 ->  -534.25 (Significant change)
IOO-WFS2_I2         :  +1610.4 ->  +1619.8
IOO-WFS2_I3         :  +1919.6 ->  +2179.8 (Significant change)
IOO-WFS2_I4         :    +1557 ->  +1426.6
IOO-WFS2_Q1         :   -62.58 ->  +345.56 (Significant change)
IOO-WFS2_Q2         :  +777.01 ->  +805.41
IOO-WFS2_Q3         :  -6183.6 ->  -5365.8 (Significant change)
IOO-WFS2_Q4         :  +4457.2 ->  +4397.

IFO Alignment
 - Aligned both arms using IR. Both arm flashes at the following, which is consistent with the power increase.
 C1:SUS-ETMX_TRX_OUT_DQ ~1.1
 C1:SUS-ETMY_TRY_OUT_DQ ~0.6
 - With this, we tried to tweak GRX and GRY injection. The following is after the work. We could increase GTRX to 0.204 when the Xarm is aligned to green. This suggests that GRX injection is not aligned nicely yet. But the beams are also not centered on TMs. We should center them first.
 C1:ALS-TRX_OUT_DQ ~0.13
 C1:ALS-TRY_OUT_DQ ~0.07
 - GTRX and GTRY cameras are adjusted to have nicer images. In GRX path, the second and last lens before the PD and CCD was pulled ~ 1 cm behind its original position and both beams realigned. Then, on GRY path, the beam was re-centered on the first and only lens, the whole assembly pushed forward by ~ 2 cm and the beams re-centered.

Next:
 - Center the IR beam on TMs (first by our eyeballs; better to use A2L after arm locking is recovered and coils are balanced)
 - Tweak GRX and GRY injection (restore GRY PZTs?)
 - Install ETMXT camera (if it is easy)
 - Lock Xarm and Yarm (C1:LSC-TRX/Y_OUT needs to be fixed for triggering. Can we use other PDs for triggering?)
 - MICH locking (REFL and AS PDs might need to be re-aligned; they are not receiving much light)
 - RTS model for BHD needs to be updated