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 Thu Apr 29 11:51:27 2021, Anchal, Summary, LSC, Start of measuring IMC WFS noise contribution in ar cavity length noise
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 Thu Apr 29 15:11:33 2021, gautam, Update, CDS, RFM 
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Thu Apr 29 17:43:16 2021, Koji, Update, CDS, RFM
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Thu Apr 29 17:43:48 2021, Anchal, Update, CDS, F2A Filters double check
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Fri Apr 30 00:20:30 2021, gautam, Update, CDS, F2A Filters double check
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Thu Apr 29 17:51:19 2021, Anchal, Summary, LSC, Start of measuring IMC WFS noise contribution in arm cavity length noise
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Fri Apr 30 00:18:40 2021, gautam, Summary, LSC, Start of measuring IMC WFS noise contribution in arm cavity length noise
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Mon May 3 09:14:01 2021, Anchal, Paco, Update, LSC, IMC WFS noise contribution in arm cavity length noise
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Mon May 3 17:28:58 2021, Anchal, Paco, Rana, Update, LSC, IMC WFS noise contribution in arm cavity length noise
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Tue May 4 11:43:09 2021, Anchal, Paco, Update, LSC, IMC WFS noise contribution in arm cavity length noise
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Fri May 7 11:54:02 2021, Anchal, Paco, Update, LSC, IMC WFS noise contribution in arm cavity length noise
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Mon May 10 18:19:12 2021, Anchal, Paco, Update, LSC, IMC WFS noise contribution in arm cavity length noise, Corrections
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Wed May 12 10:53:20 2021, Anchal, Paco, Update, LSC, PSL-IMC PDH Loop and XARM PDH Loop diagram
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Message ID: 16117
Entry time: Tue May 4 11:43:09 2021
In reply to: 16112
Reply to this: 16127
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| Author: |
Anchal, Paco |
| Type: |
Update |
| Category: |
LSC |
| Subject: |
IMC WFS noise contribution in arm cavity length noise |
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We redid the WFS noise injection test and have compiled some results on noise contribution in arm cavity noise and IMC frequency noise due to angular noise of IMC.
Attachment 1: Shows the calibrated noise contribution from MC1 ASCPIT OUT to ARM cavity length noise and IMC frequency noise.
- For calibrating the cavity length noise signals, we sent 100 cts 100Hz sine excitation to ITMX/Y_LSC_EXC, used actuator calibration for them as 2.44 nm/cts from 13984, and measured the peak at 100 hz in time series data. We got calibration factors: ETMX-LSC_OUT: 60.93 pm/cts , and ETMY-LSC_OUT: 205.0 pm/cts.
- For converting IMC frequency noise to length noise, we used conversion factor given by
 where L is 37.79m and lambda is wavelength of light.
- For converting MC1 ASCPIT OUT cts data to frequency noise contributed to IMC, we sent 100,000 amplitude bandlimited noise (see attachment 3 for awggui config) from 25 Hz to 30 Hz at C1:IOO-MC1_PIT_EXC. This noise was seen at both MC_F and ETMX/Y_LSC_OUT channels. We used the noise level at 29 Hz to get a calibration for MC1_ASCPIT_OUT to IMC Frequency in Hz/cts. See Attachment 2 for the diaggui plots.
- Once we got the calibration above, we measured MC1_ASCPIT_OUT power spectrum without any excitaiton and multiplied it with the calibration factor.
- However, something must be wrong because the MC_F noise in length units is coming to be higher than cavity length noise in most of the frequency band.
- It can be due to the fact that control signal power spectrum is not exactly cavity length noise at all frequencies. That should be only above the UGF of the control loop (we plan to measure that in afternoon).
- Our calibration for ETMX/Y_LSC_OUT might be wrong.
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