Since we postponed the HAM1 in-vac mission today, we moved on to the interferometer alignment for now.

Here are what I did:

• The forward propagating beam was steered on the in-vac POP A and B QPDs.
  • To make the signals bigger, I increased the whitening gains of the QPDs from 0 to 45 dB.
  • Although the readouts are very tiny i.e. POP_A(B)_SUM ~ 4 counts, this was big enough to be discriminated from back ground noise.
  • This was done by steering IM4. I had to move IM4 mostly in pitch.
• PRM was then realigned to this new IM4 alignment such that we keep having the retroreflection back to PSL.
  • This means there is no impacts on the interferometer REFL paths.
• The PR2 and PR3 alignment were restored back to July 25th 1:00 AM PDT by using the bottom mass OSEMs as a reference.
• The BS alignment was restored back to July 25th 1:00 AM PDT by using the oplve as a reference.
• ITMY DC bias was restored back to July 25th 1:00 AM PDT.
  • We didn't trust the oplev for ITMY.

The attached is a screenshot of the resultant vertex alignment.