40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log  Not logged in ELOG logo
Entry  Mon Jun 3 16:46:31 2019, gautam, Update, IOO, IMC not locking PCdrive_RMS.png
    Reply  Tue Jun 4 10:56:31 2019, gautam, Update, IOO, IMC diagnostics IMCdiag.pdf
       Reply  Thu Jun 6 22:11:53 2019, Koji, Update, IOO, IMC diagnostics 
          Reply  Thu Jun 13 18:01:18 2019, aaron, Update, IOO, IMC diagnostics 
             Reply  Fri Jun 14 13:10:00 2019, aaron, Update, IOO, IMC diagnostics 
                Reply  Mon Jun 17 12:37:16 2019, aaron, Update, IOO, IMC diagnostics 
                   Reply  Tue Jun 18 20:35:07 2019, aaron, Update, IOO, IMC diagnostics 
                      Reply  Wed Jun 19 19:12:51 2019, aaron, Update, IOO, IMC diagnostics PMC_Error_Spectrum.pdfPDH_signal.pdfPDH_signal_full.pdf
                         Reply  Mon Jun 24 15:49:05 2019, aaron, Update, IOO, IMC diagnostics sweep_config_updated.png
                            Reply  Tue Jul 2 19:36:18 2019, aaron, Update, IOO, IMC diagnostics PDH_error.pdfPMC_Error_Spectrum.pdf
          Reply  Fri Jun 21 19:36:26 2019, Koji, Update, IOO, IMC diagnostics IMC_error.pdf
             Reply  Sun Jun 23 08:09:53 2019, gautam, Update, IOO, NPRO diagnostics consolidatedOscopeScreenCaps.pdfRINcomp.pdfPLL_OLTF.pdfPLLnoise.pdf
                Reply  Sun Jun 23 09:36:32 2019, gautam, Update, IOO, IMC is locking normally again PMCdiag.pdf
                   Reply  Sun Jun 23 14:43:14 2019, Koji, Update, IOO, IMC is locking normally again 
                   Reply  Mon Jun 24 08:12:10 2019, gautam, Update, IOO, IMC is locking normally again IMCdutycycle.png
                      Reply  Mon Jun 24 11:48:35 2019, gautam, Update, IOO, IMC in-loop error spectra and OLTF IMCfreqNoise.pdfIMC_OLTF.pdfIMC_CMboard.jpg
Message ID: 14683     Entry time: Wed Jun 19 19:12:51 2019     In reply to: 14681     Reply to this: 14693
Author: aaron 
Type: Update 
Category: IOO 
Subject: IMC diagnostics 

Here are the results from the fit. Data can be found on nodus in /users/aaron/40m/data/PMC/190617/. I've put a jupyter notebook with the analysis in /users/aaron/40m/analysis/PDH_calibrate.ipynb (might be some filename issues due to different directory structure on my laptop).

Here's a summary of the current measurement. I'll be referencing the diagram for the PMC servo card.

  1. With the PMC servo loop open, sweep the PMC PZT by sending a triangle wave in to J5 (external drive on the servo card).
    1. I used a 100Hz drive, but should use something slower so my drive isn't filtered out by the 100Hz pole on the servo card and the 10Hz pole on the PZT.
  2. Monitor the voltage at the HV drive, as well as at "mixer out" (J8 on the servo board)
    1. Note that I took this PDH error signal from FP2TEST rather than "mixer out", which means my error signal was not low pass filtered.
  3. Calibrate the HV mon in units of Hz by fitting the PDH signal. The sidebands should be 35.5Mhz away from the carrier peak.
    1. This part needs to be done differently to account for thermal locking in the PMC.
  4. You now have the PDH error signal as a function of PMC resonance in Hz, and can use that to calibrate the PDH error spectrum.
    1. The spectrum is taken when the PMC is locked, so the Hz/V scaling is the slope of the PDH error signal.

In the figures below, I obesrved that for fast (100Hz) drives, the PDH error signal had a pi/2 phase shift relative to the triangle wave, which means even though the resonance appears near the turnaround of the triangle, it is actually occuring near the center of the range.

There are several problems with this data:

  • PMC error signal spectrum is not properly calibrated, even according to the process described above
  • The drive was faster than the response of the PZT.
  • I was driving with a ~1V excitation, so I've lost a factor of 10 somewhere on the way to the external drive curve. Probably just a problem with how I've read the data dump from the scope.
Attachment 1: PMC_Error_Spectrum.pdf  54 kB  Uploaded Wed Jun 19 20:20:10 2019  | Hide | Hide all
PMC_Error_Spectrum.pdf
Attachment 2: PDH_signal.pdf  64 kB  Uploaded Wed Jun 19 20:25:16 2019  | Hide | Hide all
PDH_signal.pdf
Attachment 3: PDH_signal_full.pdf  151 kB  Uploaded Wed Jun 19 20:25:25 2019  | Hide | Hide all
PDH_signal_full.pdf
ELOG V3.1.3-