The replacement turbine flow sensor seems to be working okay and without any leaks.

Whilst the laser was down, the dark voltage of the pre-modecleaner locking photodiode
and frequency stabilisation reflection photodiode was measured.
  PMC locking photodiode : 23.5 - 23.7 mV
       FSS RF photodiode : -4.6 - -4.7 mV

    Whilst engaging the PMC, the output of the locking photodiode would saturate and latch
at random intervals, causing the PMC to oscillate.  This photodiode was replaced with a
spare.
  old : S1107847
  new : S1107848
The measured maximum power that could fall incident on the locking photodiode was ~63 mW.
These occurred at ~83 degrees and 265 degrees.  The minimum power was ~1 mW, and this
occurred at 167 degrees and 347 degrees.

    After locking the FSS, ~10.1 mW was measured after the Faraday isolator located behind
the reference cavity.  This was increased to ~30 mW by rotating WP4 from 98 degrees to 86
degrees.

    Had problems with the stability of the power stabilisation.  The free-running power
fluctuations transmitted by the PMC were perhaps at most 3%.  Yet when the power stabilisation
servo was engaged, it was working far harder than this figure would suggest.  Not obvious why.
Perhaps it's a scattered light issue?





Jason, Peter