peter.king@LIGO.ORG - posted 07:09, Tuesday 05 July 2016 - last comment - 09:11, Tuesday 05 July 2016(28142)
Laser down
Came in to find the laser was off due to the power watchdog being tripped. Both chillers were still running. I have turned the laser back on but it hasn't returned to where it normally returns to. Looking into what happened.
Looks like the NPRO tripped out. Maybe due to a minor power surge due to the start of the week? Pre-modecleaner had some problems locking irrespective of the reference level. Found that a small tweak to the horizontal alignment brought things back right away. Note in passing: with no light the output of the locking photodiode was ~ +29 mV. Unlocked (ie with light incident on the pre-modecleaner) the output was ~ -230 mV. Which is sort of low, which might be consistent with a small mis-alignment. The locking photodiode is a 1 mm InGaAs photodiode after all.