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Reports until 17:26, Monday 01 August 2016
H1 PSL (PSL)
peter.king@LIGO.ORG - posted 17:26, Monday 01 August 2016 - last comment - 08:12, Tuesday 02 August 2016(28795)
FSS optical path tweak
The alignment into the reference cavity was tweaked.  Mostly a vertical adjustment followed by a
minor adjustment to the yaw.  The transmission as reported on the MEDM screen went from ~2.6V to
~4.6V.

    Measured the power before the lens located in front of the ALS fibre to be 33.4 mW.  At this
time MEDM reported 4.62V.

    With a DMM, the DC output of the locking photodiode was measured.
 - locked: 0.124 - 0.134 V
 - unlocked: 0.772 - 0.777 V
So the reference cavity visibility is 83.3%.  The gain of the filter yielding the DC output of the
locking photodiode was changed from -0.050 to +0.500 as this agreed better with the value measured
with the DMM.  Not sure why the big change other than I had noticed that since the CDS reboot of a
couple of weeks ago, the reflected DC was different.  Perhaps this gain setting wasn't saved?

    For the transmission photodiode, when the FSS was unlocked the DMM measured -1.8mV.  MEDM
reported ~0.121V at the same time.  When the FSS was locked and MEDM reported ~4.6V in transmission
the DMM measured -2.766V to -2.777V.



Jason/Peter
Comments related to this report
matthew.heintze@LIGO.ORG - 08:12, Tuesday 02 August 2016 (28801)

For a comparison I just happened to measure the ref cav visibility yesterday as part of the PSL rebuild and LLO also get ~83% visibility

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