Abstract:

GRX and IRX flash were found and X arm can be locked with both IR and GR.

Detail:

1. Alignment of PR3, ITMX, and ETMX:

First, we aligned PR3 so that GRX hit the center of the TMSX GR PD by scaning PR3 alignment.
Then, I scaned ETMX good alignment so that reflection beam was hit on the GR REFL PD (ITMX was MISALIGNED state at that time).
After that, ITMX was scaned so that reflection from ITMX is hit on the GRX REFL PD center.
Then, GRX is flashed, so I ran the script (search_FRX_alignment.py) to find the better alignment of PR3, ITMX, and ETMX.

2. Alignment of PR2:

After alignment of GRX, I tweeked PR2 alignment so that IR reflection from ITMX hit on the REFL PD.
Then, IRX flash can be seen.
After the alignment, PR2 OpLev is cmpletely out of range, so we need PR2 OpLev centering to remember the good PR2 alignment.

3. Lock trial of GRX:

I requested ALS_LOCKED state toXARM guardian and GRX can be locked with TEM00 without any problem.

4. Lock trial of IRX:

I rotated IFO REFL HWP from 176 to 146 degrees to increase the laser power on REFL PD.
Then, I requested IR_LOCKED state to XARM guardian.
Though IR seems resonating, IMC trans power oscilated a lot due to the oscillation of MCL control.
The reason of the oscillation is gain change of MCE actuator, so I added a gain of 0.3 in FM1 (3,500) of LSc:MCL filter bank.
After this modification, IRX can be locked with TEM00 without any problems.