aLIGO LHO Logbook

H1 TCS

camilla.compton@LIGO.ORG - posted 16:52, Tuesday 12 April 2022 - last comment - 14:16, Wednesday 27 April 2022(62581)

CO2X laser up and RS calibration

In the TCS_CO2 guardian script, I reduced limit for checking if the CO2 laser is on from 35W to 30W and reloaded it. Now the CO2X laser seems to be staying locked in LASER_UP. The laser has decreased from ~50W 2 years ago to 38W for CO2Y and 34.8W for CO2X, see here.

In the CO2X power control I requested search for home and then to 90deg to check the calibration numbers. They agreed. B: minimum power angle = 36.7deg, C: Minimum power 0.003. This is looking at LASER_POWER_ACTUAL. The values are slightly different for LSRPWR_MTR_OUTPUT. I haven't looked into how these are related yet.

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ryan.short@LIGO.ORG - 15:31, Tuesday 26 April 2022 (62823)

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I checked the calibration numbers for CO2Y also, and they agreed as well.

B: Minimum power angle = 60.37deg, C: Minimum power = 0.000. Again, this is looking at LASER_POWER_ACTUAL, and they again deviate slightly from LSRPWR_MTR_OUTPUT by ~1deg.

ryan.short@LIGO.ORG - 14:16, Wednesday 27 April 2022 (62848)

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Camilla, Ryan

As it turns out, we've been mistakenly checking our calibration numbers against the LASERPOWER_ACTUAL channel, which is, of course, the calibration curve itself. It's no surprise that we found the minimum power and minimum power angle to match exactly! The correct minimum power for CO2X is 0.091 W with an associated angle of 37.776 deg, and for CO2Y the minimum power is 0.031 W at 61.487 deg. We have updated these values in the calibration models appropriately. Screenshots of the old calibration values are included on this comment.

Also attached are plots from scanning the 90 degree range of the CO2 laser rotation stages to find the max power on ITMX and ITMY using central heating, annular heating, and no mask. As one could see, the ITMY CO2 laser was not on for these scans due to a trip (which we're still investigating) so we'll retake the scans for ITMY once we have the laser back on again. For now, we can still use this data to find the max power on ITMX from the LSRPWR_MTR_OUTPUT channel:

Heating Type	Requested power at max before updated calibration (W)	Max power (W)	Max power angle (deg)
No mask	4.95	12.10	80.77
Annular	4.95	5.88	82.91
Central	4.95	3.27	82.86

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