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Entry  Sat Feb 23 07:14:58 2013, yuta, Update, LSC, can't lock Y arm TRYPOY.png
    Reply  Sat Feb 23 14:52:03 2013, Jenne, Update, LSC, ETMYT camera back to normal 
    Reply  Sat Feb 23 16:54:24 2013, Jenne, Update, LSC, can't lock Y arm 
       Reply  Sat Feb 23 17:14:59 2013, yuta, Update, LSC, can't lock Y arm 
Message ID: 8150     Entry time: Sat Feb 23 17:14:59 2013     In reply to: 8149
Author: yuta 
Type: Update 
Category: LSC 
Subject: can't lock Y arm 

Jenne found that;
  0. If all mirrors are "aligned," Yarm flashes.
  1. If SRM is misaligned, Yarm doesn't flash.
  2. If BS is misaligned, Yarm doesn't flash.
  3. If ITMX is misaligned, Yarm still flashes.

So, my hypothesis from this is that I was playing with " TT1 -> TT2 -> ITMY -> BS -> SRM -> BS -> Yarm "  configuration last night.
This hypothesis can explain;
  1. Why I could not get TRY peak more than 0.5 (additional BS reflection makes incident power to Yarm less).
  2. Why I had to change POY11 I/Q mixing angle by ~ 45 deg (because EOM to Yarm length changed).
  3. Why I couldn't lock Yarm stably (additional reflection by BS and SRM made too much beam jitter?).

We are now trying to get "real" Yarm flash.

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