jeffrey.kissel@LIGO.ORG - posted 11:03, Tuesday 15 April 2025 - last comment - 12:14, Tuesday 15 April 2025(83925)
ALS/SQZ Path Monitor PDs Post-vent/Post-Power Outage/Pre SPI Pickoff Install -- vs. PSL Environment
J. Kissel ECR E2400083 IIET 30642 WP 12453 We're getting started on installing the PSL Pick-off path for the future SPI, and we want to record the values of the ALS/SQZ fiber distribution path before any work gets started -- and also see how these PD's values depend on the PSL environment. These PDs are described thoroughly in LHO:83013, but in short, there's a monitor PD internal to the PSL, on the table, and a down stream fiber-coupled monitor PD inside the ALS/SQZ fiber distribution box. Note, because ISCT1 has been moved out of the way for the ISI HAM1 install, the ALS COMM 2f SHG power monitor PD is unexpected to be dead, reading zero. The good news: after the 2025-04-01 corner station vent and 2025-04-06 Power outage (LHO:83753), both ALS/SQZ path PDs report the same power as the did in Feb 2025 -- even though the PMC transmitted power is a few Watts less: Feb 24 2025 Today (Lights OFF) Today (Lights ON) H1:PSL-PWR_PMC_TRANS_OUTPUT [W] 105.0 104.6 104.6 H1:ALS-C_FIBR_EXTERNAL_DC_POWER [mW] 44.6 45.15 45.55 H1:ALS-C_FIBR_INTERNAL_DC_POWER [mW] 30.2 29.8 31.9 In LHO:83013, I reported the *log* of the power for the ALS path PDs rather than the absolute milliwats. Here, I quote both dates in absolute power [mW] for the record. Watching the long term trend of the PD internal to the ALS/SQZ fiber box, the power swings regularly by ~2 mW. The current max is ~31.5 mW, and min is 29.5 mW. During this morning's data, PSL environmental controls were on the fritz. My guess is that the optical fiber that feeds the ALS/SQZ internal monitor PD is quite sensitive to temperature, as you can see the INTERNAL power smoothly swing up and down. The free-space, on table EXTERNAL PD makes sharp 0.3 [mW] jumps when the lights are turned on and OFF, but otherwise no sensitivity to temperature. Finally, everything moves slightly with the PMC transmitted power, and the slightly smaller, seemingly random 0.2 [W] blips in PMC transmitted power are a result of Jason / Ryan going in and out of the main PSL room to try to assess with the environmental controls and turning on/off the lights. Upsettingly interesting! So, here should be our goal powers for on-table EXTERNAL PD and fiber-coupled INTERNAL PD should be somewhere around Environmental Controls and Lights OFF EXTERNAL / ON TABLE / Free-space PD 45.2 +/- 0.1 [mW] INTERNAL / IN RACK / Fiber-Coupled PD 31.2 +/- 0.2 [mW] Environmental Controls and Lights ON EXTERNAL / ON TABLE / Free-space PD 45.5 +/- 0.1 [mW] INTERNAL / IN RACK / Fiber-Coupled PD 30.6 +/- 1.0 [mW]
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UPDATE: Eric rescued the PSL environmental controls after a full system reboot. The systems communications to the actually HVAC had not been recovered since the power outage, so it required a full-system restart. This was complete and the system was functional by 2025-04-15 18:20 UTC.
Attached are the same PD trends as the environmental controls turn on, and the temperature in the enclosure adapts.
The PMC transmitted power went DOWN from 104.6 [W] to 103.7 [W].
The EXTERNAL, on table, free-space PD went DOWN from 45.5 [mW] to 45.2 [mW].
The INTERNAL, fiber-coupled ALS/SQZ distribution box PD became more stable at 31.2 [mW].
So... NEW GOALS for the PDs with the environmental controls on and functioning normally, with the lights on:
H1:ALS-C_FIBR_EXTERNAL_DC_POWER 45.2 +/- 0.2 [mW]
H1:ALS-C_FIBR_INTERNAL_DC_POWER 31.2 +/- 0.2 [mW]
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