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| 40m Log |
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 Mon Feb 4 20:13:39 2019, gautam, Update, SUS, ETMY suspension oddness 
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 Thu Feb 7 19:34:18 2019, gautam, Update, SUS, ETMY suspension oddness
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Fri Feb 8 20:48:52 2019, gautam, Update, LSC, IFO recovery
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Mon Feb 11 15:41:49 2019, gautam, Update, LSC, TRY 60 Hz solved - but clipping persists
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Mon Feb 11 16:38:34 2019, gautam, Update, LSC, ETMY OL calibration updated
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Fri Feb 15 18:42:57 2019, gautam, Update, LSC, TRY 60 Hz solved
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Message ID: 14445
Entry time: Fri Feb 8 20:48:52 2019
In reply to: 14441
Reply to this: 14446
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| Author: |
gautam |
| Type: |
Update |
| Category: |
LSC |
| Subject: |
IFO recovery |
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Several housekeeping tasks were carried out today in preparation for the Y-arm loss measurement.
- The mess around the OMC rack was cleared a bit. The vertex laptop paola now lives there, instead of on the ITMY optical table.
- Centering of beam on AS photodiodes on AS table (starting from the first optic in this path at the exit point from the vacuum), adjusted AS camera to bring the spot roughly to the center.
- POX/POY locking was restored, GTRY/GTRX levels are healthy. TRY was centered on the Thorlabs PD by triggering the LSC lock on AS110.
- Oplevs on all four TMs and BS were centered for post-vent alignment.
- ETMY OL transfer function was checked since we have swapped the HeNe during the vent, 4.5 Hz UGF for both DoFs and ~30 deg phase margin. The calibration of the error point to urad needs to be double checked.
- There are some huge 60 Hz harmonics in the TRY signal - hunting down the source of this. The one thing I can think of that was changed is that we plugged the c1auxey eurocrate into the ethernet powerstrip, I wonder if this created some kind of ground loop.
- I checked the signal from the PD with a battery powered scope, no evidence of any 60 Hz in the time domain or scope FFT (Attachment #1, FFT in red and time domain signal in green can be seen).
- Restored the power of c1auxey eurocrate to its original socket in the back of 1Y4 - harmonics still present --> points to the problem being in the whitening board / ADC electronics?
- The harmonics only seem to show up when TRY > ~0.5
- Some elog hunting revealed that this signal is being digitized through a modified D990399. So somehow the signal pollution is happening inside this board? Because from the output of this board, the signal is going straight into the ADC.
- To confirm, I will temporarily hijack another ADC channel and look at the spectrum. There is apparently some kind of daughter board (D040060), but how 60 Hz is coupling at this stage is unknown to me.
- The ASS system for both arms still isn't working properly, to be investigated. The dirty TRY signal probably isn't helping the situation.
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