sheila.dwyer@LIGO.ORG - posted 12:53, Saturday 10 February 2018 - last comment - 15:52, Monday 12 February 2018(40480)
PSL is off
I came in to do some last DRMI/PRMI tests, and found the laser is off. This happened about 4:15 am pacific time. THe epics channels don't show any problems with the chillers, and it looks like the power watch dog tripped after the laser went off. (screenshot attached)
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It looks like this possibly was the power watchdog. The NPRO power and currents have been stable since the HPO has been off, but the PSL-AMP_PWR channels show that the power had been dropping before the laser shut off. The Beckhoff status screen shows that everything is normal except the power watchdog.
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Jason logged in remotely and restarted the PSL.
Various data trends are attached. At the time the power watchdog was engaged the output power was ~34.8 W. There is no indication that the power decreased by 15% since the watchdog was enabled. Trend data also suggests that the amplifier dropped out before the NPRO.
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Indeed the front end laser was tripped off by the power watchdog. The trigger signal for the watchdog is the output of the third
amplifier stage and not the output of the front end - something that is rectified with the upcoming front end laser modifications.
When the watchdog was last engaged the power was ~106. The watchdog tripped in at ~90, ie at the 15% drop level. So the watchdog
worked as it should.
Oh and the drop in power is most likely due to the large drop in relative humidity. We know the e-beam sputtered coatings
for the pick-offs have issues with relative humidity.
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