Jeff K, Alastair (by phone), Nutsinee
Jeff noticed that TCS CO2Y was throwing a bunch of guardian error messages which led him to investigate and found that the CO2Y actual output power was lower since the laser recovered from maintenance activity this morning. Timeseries shows that CO2Y power dropped out at 15:41 UTC (8:41 local time) and never came back to its nominal (~57W). Chiller temperature which is read off the front end was down at the same time indicating CO2Y was down due to some front end maintenance activity. The supply current to CO2Y was also low compared to CO2X (19A vs 22A) suggesting that the low power output was real. And indeed, we went out and measured about 40W at the table (we stick a handheld power meter right before the first steering mirror).
We don't know why would the Front End maintenance today would affect CO2Y output power (CO2X is fine by the way). On the plus side, the heating profile looks good on the FLIR camera which means nothing was misaligned and we can still use CO2Y laser. The beam dump that was in front of the FLIR screen hasn't been put back so be mindful if you ever want to blast full power through the rotation stage.
I commented out the output power fault checker part in TCS power guardian so that ISC_LOCK can still tell it to go places. I added a temporary +1 degree offset to the minimum angle parameter for CO2Y rotation stage calibration so it would go to requested powers. We requested TCS CO2 laser stabilization guardian to down because it's not usable given a current output power.
Quick conclusion: CO2Y is still functional. The reason for power loss is to be investigated.
J. Kissel, S. Dwyer, N. Kijbunchoo, J. Bartlett, V. Sandberg A few checks we forgot to mention to Nutsinee last night: - Nutsinee and I checked the flow rate on the mechanical flowmeter for both the supply and return for TCSY chiller line, and it showed (what Nutsinee said was) nominal ~3 Gallon per minute. This was after we manually measured the power to be 41 W coming out of the laser head to confirm the EPICs readout. - Sheila and I went to the TCS chillers on the mezzanine. Their front-panel display confirmed the ~20.1 deg C EPICs setting for temperature. - On our way out, we also noticed that a power supply in the remote rack that is by the chillers marked "TCSY" was drawing ~18 mA, and was fluctuating by about +/- 2mA. We didn't know what this meant, but it was different than the power supply marked TCSX. We didn't do anything about it. - The RF oscillator mounted in that same remote rack appeared functional spitting out some MHz frequency sine wave. Sheila and I did not diagnose any further than "merp -- looks like an oscillator; looks on; looks to be programed to spit out some MHz sine wave."
Alastair, Nutsinee
Today I went and check the CO2Y power supply set point. Voltage limit is set to 30V and current limit is set to 28A. Same goes for CO2X power supply. These are correct settings, which means CO2Y laser is really not behaving properly.