The power of the CO2 lasers seems to be degrading quickly for CO2Y in particular. See trend attached. It's also possible that the CO2 laser servos and setpoints need updating.
I found the TCS_ITMY_CO2 guardian in DOWN with a notification that the "laser appears off" when the laser was on. This is looking at LSRPWR_HD_PD_OUTPUT is the power of the laser measured by the CO2 laser itself. I have reduced this check from 30W down to 20W, it was 40W in O3. The current value of LSRPWR_HD_PD_OUTPUT for CO2Y is 28.7W. CO2X is 34.4W.
This is bad. They will not work much longer if this continues. I suggest measuring the output power directly to determine if the issue is with the LSR_HD monitor somehow, or is a real drop in laser power.
I compared all the settings on the CO2 laser screen from 2019 to this week. See attached. I can't see that anything meaningful is different. PZT_SERVO_GAIN is different but this is set by the CO2 guardian when finding the lock point.
Jason commented that when these lasers were first turned back on after the end of O3 at 21/09/18 they came back noisy and at low power but this was actually not a real readback (see alog 61027 and alog 60538). As seen in attached plots the lasers were off at that time. We may ahve damaged some elecrronics by driving pzts with non-real signals at this time though.
>> nds_query -v -n nds.ligo.caltech.edu -p 31200 -s 1345401600 -d 1 --samples-per-line 1 H1:TCS-ITMY_CO2_LSRPWR_HD_PD_OUT16 H1:TCS-ITMY_CO2_PZT_MON_OUT16 [..more channels here separated by spaces] H1:TCS-ITMY_CO2_CHILLER_OUT_GAIN_LIMIT > 1345401600.txt>> bash /ligo/home/camilla.compton/Documents/scripts/CompareChannels/compare_channels.sh 1345401600.txt >> cat 1345401600.txt
