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 Mon Jun 3 16:46:31 2019, gautam, Update, IOO, IMC not locking 
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 Tue Jun 4 10:56:31 2019, gautam, Update, IOO, IMC diagnostics
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Thu Jun 6 22:11:53 2019, Koji, Update, IOO, IMC diagnostics
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Thu Jun 13 18:01:18 2019, aaron, Update, IOO, IMC diagnostics
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Fri Jun 14 13:10:00 2019, aaron, Update, IOO, IMC diagnostics
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Mon Jun 17 12:37:16 2019, aaron, Update, IOO, IMC diagnostics
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Tue Jun 18 20:35:07 2019, aaron, Update, IOO, IMC diagnostics
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Wed Jun 19 19:12:51 2019, aaron, Update, IOO, IMC diagnostics
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Mon Jun 24 15:49:05 2019, aaron, Update, IOO, IMC diagnostics
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Tue Jul 2 19:36:18 2019, aaron, Update, IOO, IMC diagnostics
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Fri Jun 21 19:36:26 2019, Koji, Update, IOO, IMC diagnostics
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Sun Jun 23 08:09:53 2019, gautam, Update, IOO, NPRO diagnostics
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Sun Jun 23 09:36:32 2019, gautam, Update, IOO, IMC is locking normally again
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Sun Jun 23 14:43:14 2019, Koji, Update, IOO, IMC is locking normally again
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Mon Jun 24 08:12:10 2019, gautam, Update, IOO, IMC is locking normally again
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Mon Jun 24 11:48:35 2019, gautam, Update, IOO, IMC in-loop error spectra and OLTF
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Message ID: 14659
Entry time: Thu Jun 6 22:11:53 2019
In reply to: 14653
Reply to this: 14670
14686
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| Author: |
Koji |
| Type: |
Update |
| Category: |
IOO |
| Subject: |
IMC diagnostics |
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As per Gautam's request, I looked at the IMC situation.
Locking path
- Acquisition: IMC IN1 Gain +4 (nominal), Boost 0, VCO Gain (-32), FSS Common +6 (nominal), FSS FAST +20
This is too low gain. So oscillate VCO Gain between -32 and ~0 until TEM00 lock is acquired
- Once lock is acquired, bring the VCO gain to +11 (new nominal), and increase the FSS FAST to +23 (new nominal). Change the IMC BOOST to 3 (nominal)
Diagnosis
- The PMC servo gain was checked. The control signal monitor for the PMC actuation was hooked up to SR785. The nominal gain was +18dB. Increasing the gain to 20dB made the servo oscillating. So the nominal gain of +18dB seems still reasonable.
- The status of NOISE EATER was checked. Both the PMC REFL and TRANS were looked at by AG4395A. The power spectrum of them did not change much around the kHz~MHz region. It made the PSD slightly (x2~3) improved below 1kHz. I also did not recognize the relaxation oscillation peak. So I could not figure out where to see. NOISE EATSER was on and is still on.
- IFO Modulation Freq: I took this chance to look at the IMC absolute length using the peak at 3.6MHz. The TP1A output of the IMC servo board was hooked up to AG4395A.
The new FSR of the IMC (and thus the modulation frequency for the IFO) is 11.066275MHz (instead of the previous 11.066209MHz).
This corresponds to 0.16mm difference in the roundtrip length.
- (*Still working) IMC SERVO configuration:
- FAST 25 (nominal) sometimes invoke the oscilattion. 24 has gain peaking ~30kHz. There is a big line peak at 35kHz so wanted to avoid the servo bump (PZT-EOM cross over). So decided to use 23dB. (This is not optimal for the CM servo as we need as much as bandwidth for CM servo.)
- IMC VCO GAIN (bad name. this is actually overall output gain for IMC) was increased from the nominal 7 to 11. Increasing this above 11 makes the servo oscillating at ~200kHz.
- (*Still working) Measured power spectrum of the error signal. Too many line peaks.
- (*Still working) Single trigger observation: Oscilloscope monitoring started from 35kHz going up and ~20kHz oscillation +/-6V of the IMC servo output was observed. Could not capture good data for this. Try the other day.
I'll complete the entry later. |