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Entry  Thu Mar 5 21:42:05 2015, Jenne, Update, LSC, AS55Q flat at DARM zero crossing DARM_TimeSeries_5March2015.pdf
    Reply  Fri Mar 6 04:49:08 2015, Jenne, Update, LSC, AS55Q transition DARM_AS55Qnormalized_5March2015.png
Message ID: 11105     Entry time: Thu Mar 5 21:42:05 2015     Reply to this: 11108
Author: Jenne 
Type: Update 
Category: LSC 
Subject: AS55Q flat at DARM zero crossing 

I think we've seen this in simulations, but it's a little disheartening to see in real life.  AS55Q looks like it flattens out pretty significantly right around the DARM=0 point. 

Right now I have the arms held on ALS (CARM=-1*MC2, DARM=2*ETMY, as Q used last night), and the PRFPMI is on REFL165I&Q.  I have set CARM to be as close to zero offset as I can (so I get all the usual buzzing), and then I'm sweeping the DARM offset between +3 and -3 counts (roughly +/-3nm) with a 3 second ramp and looking at normalized AS55Q.  The channel called "DARM_B_ERR" is 0.006*AS55Q/(TRX + TRY).  The arm transmissions, as well as the ASDC are plotted as well - ASDC is scaled to fit on the same axes as the transmissions.

Anyhow, here's the time series of the DARM sweeps.  AS55 demod phase of -55 degrees seems to give the cleanest signal (within 5deg steps); this is the same phase that we've been using all week.

DARM_TimeSeries_5March2015.pdf

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DARM_TimeSeries_5March2015.pdf
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