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Entry  Mon Oct 27 19:15:54 2014, ericq, Update, LSC, Trying to PRMI on 165 
    Reply  Wed Oct 29 03:33:38 2014, ericq, Update, LSC, Trying to PRMI on 165 
       Reply  Thu Oct 30 01:21:37 2014, Jenne, Update, LSC, No MICH in REFL165 MICH_to_REFL165_29Oct2014.pdf
Message ID: 10649     Entry time: Wed Oct 29 03:33:38 2014     In reply to: 10641     Reply to this: 10652
Author: ericq 
Type: Update 
Category: LSC 
Subject: Trying to PRMI on 165 

 

Short report: Further frustrated by 165 tonight. The weird thing is, the procedure I'm trying with the arms held off on ALS (i.e. excitation line in MICH and PRCL, adjust relative gains to make the signs and magnitudes mach, ezcastep over) works flawlessly with the ETMs misaligned. One can even acquire SB PRMI lock on 165 I&Q, with 80-90 degrees of demod angle between MICH and PRCL. The only real difference in REFL55 settings for misaligned vs. ALS-offset arms is an extra factor of two in the FM gains to maintain the same UGF, so I hoped that the matrix elements for 165 with misaligned arms would hold for ALS-offset arms. 

Alas, no such fortune. I still have no clear explanation for why we can't get MICH on 165Q with the arms held off on ALS. 

I also gave a quick try to measuring the PRCL->REFL55 demod phase difference between carrier and sideband lock (with arms misaligned), and got something on the order of 55 degrees, which really just makes me think I wasn't well set up / aligned, rather than actually conveying information about the PRC length...

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