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Wed Jan 29 14:49:48 2020, anchal, DailyProgress, BEAT, Beanote Spectrum vs FSS Gain Values
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Wed Jan 29 15:58:26 2020, anchal, DailyProgress, BEAT, Beanote Spectrum vs FSS Gain Values
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Fri Feb 7 09:57:32 2020, anchal, DailyProgress, BEAT, Spanned gain parameter space in NFSS and checked beatnote
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Fri Feb 7 18:12:03 2020, anchal, DailyProgress, BEAT, Spanned gain parameter space in SFSS and checked beatnote
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Mon Feb 10 11:07:33 2020, anchal, DailyProgress, BEAT, Spanned gain parameter space in PMCs and checked beatnote
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Thu Feb 13 15:27:18 2020, anchal, DailyProgress, BEAT, Further iterated back and forth to optimized FSS Gains.
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Message ID: 2522
Entry time: Wed Jan 29 15:58:26 2020
In reply to: 2521
Reply to this: 2524
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Author: |
anchal |
Type: |
DailyProgress |
Category: |
BEAT |
Subject: |
Beanote Spectrum vs FSS Gain Values |
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Quote: |
I'll repeat this measurement again to make sure this optimal gain setting region was not a coincidence due to some other parameter out of my control. |
Measurement
- Everything is almost the same as the last measurement.
- This time, if you notice from orange to yellow curve, I had to manually lower down the gain on the south common path by 12 dB instead of 3 dB to ensure the south path doesn't go into oscillations.
- From there onwards, the gains were reduced normally by 3 dB in each step/
Inference
- The beatnote spectrum indeed drops down to lowest when the gains are 3 dB below the maximum gains where I keep the loops.
- Maybe keeping a large gain margin is important. But I need help to understand this result.
- Also, it is kind of clear that the laser noise starts showing up from the yellow curve onwards only. So in current gain settings, the noise floor is probably due to something else.
- Another weird fact I saw was that the RMS of error signal taken at "Mixer" port which is the TP5 point in LIGO-D040105-C_CTN_North increases significantly only after the gain values of the loop is decreased by more than 15 dB (to -1 dB each on FAST and COM).
- The same thing can't be said for the south path where I see a gradual increase in this error signal RMS value as the gains are reduced.
- If someone has a better idea of understanding these results or has some suggestions on further tests or a combination of parameter changes I should do, please let me know.
Data |
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