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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: 14721
Entry time: Tue Jul 2 19:36:18 2019
In reply to: 14693
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Author: |
aaron |
Type: |
Update |
Category: |
IOO |
Subject: |
IMC diagnostics |
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The latest in my fling with the PMC. Though PMC trans is back to nominal levels (~0.713 V), we'd still like to understand the PMC noise.
Last time, I took some spectra with the RF probe (Agilent 41800A). I had already measured the PDH error signal by sweeping the PZT at ~1 Hz. The notebook I used for analysis has been updated in /users/aaron/analysis/PDH_calibrate.ipynb. The analysis was the following:
- fit the PDH error signal, assuming a 35.5MHz modulation frequency. Here are the (approximate) fit parameters:
- Mapping of PZT mon voltage to Hz: 5.92 Hz/V_{PZT_mon}
- P_carrier*P_signal: 0.193 W^2
- HV mon voltage on resonance: 0.910 V
- Error signal far off resonance: 0.249 V
- Transmission: 0.00238
- yikes. The nominal transmission is T=0.003. I let this parameter be free as a check, and to avoid overconstraining the data; is this consistent with measurements of the PMC optics' transmission?
- Length: 0.0210 m
- This is consistent with the nominal PMC length
- Using the fit of the full PDH error signal, I am able to plot error signal vs frequency, and fit the linear portion of the carrier PDH signal. The results of this fit are:
- -9.75e-7 V_PDH per Hz
- 0.105 V error signal at DC
- I then divide the power spectra by the squared slope of the linear fit above (V_PDH^2/Hz^2) to get the spectra in Hz^2/rtHz
- I've plotted both the spectrum I took directly at the mixer I using the agilent probe, as well as the spectrum taken by sending the PMC servo card's mixer mon to an SR560 (G=2) then to the spectrum analyzer
There are a few problems remaining:
- There should be a gain of 100 between the mixer I and the servo board's mixer out. It's not clear to me that this is reflected in the spectra. Moreover, the header files on the spectra I grabbed from the Agilent say that the R (mixer I) channel has 20dB of input attenuation, which is also not reflected. If I have swapped the two spectra and not accounted for either the gain of the servo card or the attenuation of the spectrum analyzer, these two gains would cancel, but I'm not confident that's what's going on.
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