Reports until 16:22, Monday 29 August 2022
H1 TCS
thomas.shaffer@LIGO.ORG - posted 16:22, Monday 29 August 2022 - last comment - 19:10, Friday 30 September 2022(64739)
TCS CO2 laser power check

Jason, Camilla, and myself went out to the two CO2 tables to measure the output directly out of the CO2 lasers themselves, not just from the power meters we have on table. We used the Thorlabs S314C sensor head since our beefier unit we couldn't get the fan to work. Since this unit can only handle up to 40W, we first checked that the power agreed with one on table downstream so we wouldn't burn the head. Unfortunately, it was the same story and the powers are far below nominal. (pictures for proof)

CO2X  - 37.72W

CO2Y - 31.74W

More unfortunate news, Jason spotted a lens on CO2X with what looks to be plastic burn marks on the plastic retainer ring and splattering on the lens itself (lens labeled LX-1060-Z-ET3.0 PL/CX 6.00” FL).

Images attached to this report
Comments related to this report
camilla.compton@LIGO.ORG - 09:23, Tuesday 30 August 2022 (64747)

These numbers are within 3W of the medm values (alog 64618): CO2Y is 28.7W. CO2X is 34.4W. 

aidan.brooks@LIGO.ORG - 16:10, Thursday 29 September 2022 (65156)

Updated measurement of output power. Looks like CO2 lasers have been off for the last month.

Images attached to this comment
camilla.compton@LIGO.ORG - 16:36, Thursday 29 September 2022 (65158)

Thanks Aidan, we've had the CO2's off during our vent. Next week we plan to swap CO2Y (currently SN 20306-20419D, installed 2016 alog29174) for our spare (20510-20816D). We'll then need to make a decision about what do do for CO2x. 

camilla.compton@LIGO.ORG - 08:43, Friday 30 September 2022 (65162)

Jason and I checked the spares located in the CO2 storage cupboard on the concrete slab through the egress door at the start of September:

  •  One complete laser and RF driver set (20510-20816D).  Notes say it was refurbished by access laser in 2016, I expect during the upgrade in alog 29174
  • One laser only, no RF driver (S/N  20710-21002D). There is a note on laser saying “tested 2014”, purchase/production date on laser is 2012.

From alogs I think current CO2X laser is SN 20706-21015D, CO2Y laser is SN 20306-20419D.

daniel.sigg@LIGO.ORG - 17:45, Friday 30 September 2022 (65171)

Not sure this is related, but this is the readback of the TCS RF distribution chassis. It started degrading about 4 years ago.

I check on the floor and the output of the RF distribution amp was showing -2.2dBm (nominal ~13dBm). I then proceeded to measure the N-output of the SG382 RF source, and it showed -2.7dBm. I noticed that it also has a BNC output that showed 9.5dBm, so I switched the cable. This resulted in the distribution amplifier to show +9.8dBm and the EPICS readback +18.2dBm.

Not sure what the nominal RF power should be, but this is still 3dB shy of the initial value 5-6 years ago. The SG382 output amplitude is set to 9.49dBm, meaning it is all consistent now. To recover the old values we would have to set the RF source to ~12.5dBm.

Images attached to this comment
aidan.brooks@LIGO.ORG - 19:10, Friday 30 September 2022 (65177)

For reference, there have been a few instances where we have noticed laser power issues that have been caused by the RF signal:

  • Problem with CO2Y, bad RF cable: 43549
    • Initial presentation of problem: 43458
  • TCS CO2Y laser tested: 40185
  • CO2 laser after power outage: 22675