Since we postponed the HAM1 in-vac mission today, we moved on to the interferometer alignment for now.
Here are what I did:
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The forward propagating beam was steered on the in-vac POP A and B QPDs.
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To make the signals bigger, I increased the whitening gains of the QPDs from 0 to 45 dB.
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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.
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This was done by steering IM4. I had to move IM4 mostly in pitch.
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PRM was then realigned to this new IM4 alignment such that we keep having the retroreflection back to PSL.
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This means there is no impacts on the interferometer REFL paths.
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The PR2 and PR3 alignment were restored back to July 25th 1:00 AM PDT by using the bottom mass OSEMs as a reference.
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The BS alignment was restored back to July 25th 1:00 AM PDT by using the oplve as a reference.
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ITMY DC bias was restored back to July 25th 1:00 AM PDT.
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We didn't trust the oplev for ITMY.
The attached is a screenshot of the resultant vertex alignment.