[Ushiba, Hirose]

As the PRXarm lock trial, we tried it: PRX_3F_LOCKED state request at the Virtex Guardian → ETMX LOCK_ACQUISITION state request → IR_LOCKED state request at the Xarm Guardian 
However, at the PRXf3locked step, an offset appears in REFLf2(CARM). After adding an offset to the PRCL error, the RF45 offset was lowered, which could be related to the PRX resonator length. 
Xarm tried to lock, but the line width was not enough to lock. So next time we will try the Xarm ALS before PRX lock.

Detail

• For the initial alignment, we performed Xarm lock, Xarm ADS, PRX lock and ADS of PRX. The OPLEV values of the mirrors moved by ADS were recorded in the PRFPMI box.(FIG1)
• As above, we tried to do PRX_3F_LOCKED state request at the Virtex Guardian → LOCK_ACQUISITION state request at the ETMX Guardian → IR_LOCKED state request at the Xarm Guardian.
• When the ETMX is reqested LOCK_ACQUISITION, the Xarm flashes and the light comes to the PRX. 
  Because a threshold is set for the POP RF90 signal in PRXf3lock, glitches appear in the RF90 detection signal, which exceed the PRX threshold.
  Therefore, ETMX was requested to LOCK_ACQUISITION with the PRXf3lock guadian state "pause" at the VIRTEX Guardian.
• However, an offset appeared in RF45 at the PRXf3lock step. We did not understand what this offset was.
  The offset was at 800, so we added 60 to the PRCL filter offset and the offset was dropped. This adjustment of the resonator length lowered the POPRF90 signal. (FIG2)
  We need to think about how to handle this offset in the PRXarm LOCK scheme.
• After adjusting the offset, the Xarm IR lock was performed, but the lock failed due to insufficient line width.
  Next time we will try to do the Xarm ALS first, following the PRFPMI approach.
• In this case, the HWP of the REFL has not been adjusted to the correct angle. We need to do.