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Entry  Thu Aug 20 02:31:09 2015, ericq, Update, LSC, PRFPMI is back lock.pdf
    Reply  Tue Aug 25 04:15:51 2015, ericq, Update, LSC, PRFPMI is back 
       Reply  Tue Aug 25 16:09:54 2015, ericq, Update, IOO, IMC Tweak imcTweak.pdfCARM_TF.pdf
          Reply  Fri Aug 28 19:05:53 2015, rana, Update, IOO, IMC Tweak 
             Reply  Tue Sep 1 11:56:56 2015, ericq, Update, IOO, IMC loop shapes IMCshapes_Aug31_2015.pdfIMC_Aug31_2015.zip
                Reply  Wed Sep 2 01:31:22 2015, ericq, Update, IOO, IMC loop shapes imc_olg_trend.pdfimc_xover_trend.pdf
       Reply  Thu Aug 27 04:23:04 2015, ericq, Update, LSC, PRFPMI is back 
          Reply  Fri Aug 28 02:20:35 2015, Ignacio, Update, LSC, PRFPMI and MCL FF carmin.pngcarmout.png
Message ID: 11555     Entry time: Tue Sep 1 11:56:56 2015     In reply to: 11538     Reply to this: 11558
Author: ericq 
Type: Update 
Category: IOO 
Subject: IMC loop shapes 

I took some transfer functions of the IMC loop and crossover, being careful that the PC drive never exceeding 1V during the measurements. 

I then did some algebra to try and back out the individual loop paths, without having to make assumptions/approximations about the loop gain being high enough. This only really works in the region where both the open loop and crossover measurements have coherence. 

It seems to me that the PZT path has pretty low phase margin on its own, but maybe this is ok, since its never really meant to run solo. The EOM path shape is harder to understand.


The data I took, and code that made the above plot is attached. This afternoon, I'll post an update comparing the measured OLG and crossover to earlier measurements. 

Attachment 1: IMCshapes_Aug31_2015.pdf  125 kB  | Hide | Hide all
Attachment 2: IMC_Aug31_2015.zip  25 kB  Uploaded Tue Sep 1 12:57:48 2015
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