As the PZT1 has not been functional, I have been aligning the Y arm to the input beam instead of aligning the beam to the Y arm.

It turned out that this procedure leads to two extra works everytime after alignments of the Y arm:

1. The Y green beam must be always aligned to the Y arm
   • The amount of the misalignment was found to be relatively big compared with how it used to be.
2. The PSL beat note setup must be always realigned because the Y green path is determined by the orientation of the Y arm.
   • In the past I didn't often realign the beat note path, but currently it needs to be pay more attentions.

Sad ..