Georgia noticed that the TCS_ITMX_CO2_PWR guardian had a notification that power was out of requested range. At 20:22UTC the CO2X laser output (measured at the laser head) jumped from 34W to 48W when it unlocked/relocked! Laser temperature and current provided agree. This is unexpected but good if it stays here as we were worried this laser was decaying and planning to replace it!
This increased the amount of CO2X annular heating into the IFO from 4.0W to 4.8W. I reduced this back to 4W and adjusted lscparams request from 2.2W down to 1.85W (different from LSRPWR_MTR value as calibrated for central heat). svn'ed and loaded CO2_PWR guardians.
The week after we installed the CO2Y laser it did a smaller jump (alog#65393) from 32W to 43W. We can check temperature and PZT lock points for both duing these times.
TJ pointed out that the new lock point could have been found as we swapped the CO2X chiller yesterday alog# 67265 and the temperature could be slightly different for the same set point. You can see in the attached plot that the laser temperature decreased by 0.3degC with the chiller swap although the CHILLER_TEMP1 remains at 22.1degC.
If the lasers start degrading again, we should adjust the temperature more than the TCS_ITMX/Y_CO2 guardian does incase there is more power to be found at a different temperature!
As Camilla noted, the laser temperature seems to change with the different chiller which is set to the same setpoint. The S/N 822 chiller that is currently running in X, is running with a ~20% higher supply pressure (~62 psi vs 54psi). Trending back, this seems to be the case with this particular chiller anytime that we've swapped it. S/N 617 and 813 tend to have around 54psi consistently. The last power jump in CO2Y came not too long after a chiller swap as well (7 days), pointing again toward the different chiller performance.
Moving forward I'd like to revisit the CO2 guardian to wait longer between chiller steps and maybe take a slower PZT scan. This carries the risk of affecting the IFO lock since it will take longer to relock, but should be worthwhile longterm.
Dan Brown noticed that this 8th Feb CO2X laser power jump also fixed our large extension ratio issue, see alog 67633.
