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Entry  Fri Oct 10 03:05:09 2014, ericq, Update, LSC, Which side of optical spring are we on? comparison.pdf
    Reply  Fri Oct 10 03:25:11 2014, Jenne, Update, LSC, Which side of optical spring are we on (simulation) 10x
    Reply  Mon Oct 13 12:01:28 2014, ericq, Update, LSC, Which side of optical spring are we on? AOInjection_SqrtInv_REFLDC.pngAOinjection_SqrtInv_REFLDC.xml.zip
       Reply  Mon Oct 13 21:20:56 2014, Jenne, Update, LSC, Which side of optical spring are we on? (No progress) 
          Reply  Mon Oct 13 21:59:47 2014, rana, Update, Computer Scripts / Programs, Which side of optical spring are we on? (No progress) 
             Reply  Tue Oct 14 17:38:31 2014, ericq, Update, Computer Scripts / Programs, Rossa and Allegra wiped, Ubuntu 12.04 installed 
                Reply  Tue Oct 14 23:44:42 2014, diego, Update, Computer Scripts / Programs, Rossa and Allegra wiped, Ubuntu 12.04 installed 
                   Reply  Wed Oct 15 17:18:10 2014, Jenne, Update, Computer Scripts / Programs, Dataviewer fix with Ubuntu 12.04 
          Reply  Wed Oct 15 02:58:03 2014, Jenne, Update, LSC, Which side of optical spring are we on?  PRFPMI_MC2injection_PosCARMoffset_REFLDC_TRX_response_14Oct2014_TRX.pdfPRFPMI_MC2injection_PosCARMoffset_REFLDC_TRX_response_14Oct2014_REFLDC.pdfPRFPMI_MC2injection_NegCARMoffset_REFLDC_TRX_response_14Oct2014_TRX.pdfPRFPMI_MC2injection_NegCARMoffset_REFLDC_TRX_response_14Oct2014_REFLDC.pdf
             Reply  Wed Oct 15 19:56:38 2014, Jenne, Update, LSC, Which side of optical spring are we on? Meas vs Model AntispringModel_NegOffsetMeas_comparison.pdfSpringModel_NegOffsetMeas_comparison.pdf
Message ID: 10612     Entry time: Wed Oct 15 19:56:38 2014     In reply to: 10607
Author: Jenne 
Type: Update 
Category: LSC 
Subject: Which side of optical spring are we on? Meas vs Model 

 I have plotted measured data from last night (elog 10607) with a version of the result from Rana's simulink CARM loop model (elog 10593).

The measured data that was taken last night (open circles in plots) is with an injection into MC2 position, and I'm reading out TRX.  This is for the negative side of the digital CARM offset, which is the one that we can only get to arm powers of 5ish.

The modeled data (solid lines in plots) is derived from what Rana has been plotting the last few days, but it's not quite identical.  I added another excitation point to the simulink model at the same place as the "CARM OUT" measurement point.  This is to match the fact that the measured transfer functions were taken by driving MC2.  I then asked matlab to give me the transfer function between this new excitation point (CARM CTRL point) and the IN1 point of the loop, which should be equivalent to our TRX_OUT.  So, I believe that what I'm plotting is equivalent to TRX/MC2.  The difference between the 2 plots is just that one uses the modeled spring-side optical response, and the other uses the modeled antispring-side response.

AntispringModel_NegOffsetMeas_comparison.pdf

SpringModel_NegOffsetMeas_comparison.pdf

I have zoomed the X-axis of these plots to be between 30 Hz - 3 kHz, which is the range that we had coherence of better than 0.8ish last night in the measurements.  The modeled data is all given the same scale factor (even between plots), and is set so that the lowest arm power traces (pink) line up around 150 Hz. 

I conclude from these plots that we still don't know what side of the CARM resonance we are on. 

 I have not plotted the measurements from the positive side of the digital CARM offset, because those transfer functions were to sqrtInvTRX, not plain TRX, whereas the model only is for plain TRX. There should only be an overall gain difference between them though, no phase difference.  If you look at last night's data, you'll see that the positive side of the CARM offset measured phase has similar characteristics to the negative offset, i.e. the phase is not flat, but it is roughly flat in both modeled cases, so even with that data, I still say that we don't know what side of the CARM resonance we are on.

 

 

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