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Entry  Wed Nov 25 16:40:32 2015, yutaro, Update, LSC, round trip loss of Y arm 
    Reply  Wed Nov 25 23:34:52 2015, yutaro, Update, LSC, round trip loss of Y arm 14.png
       Reply  Fri Nov 27 03:38:23 2015, yutaro, Summary, LSC, round trip loss of Y arm image1.png
          Reply  Fri Nov 27 22:20:24 2015, yutaro, Update, LSC, round trip loss of Y arm log.txt.zip17.png
          Reply  Sat Nov 28 11:46:40 2015, yutaro, Update, LSC, possible error source of loss map measurement 
          Reply  Mon Nov 30 10:41:45 2015, yutaro, Update, LSC, Does a baffle in front of ETMY have effect on loss map measurement? 
             Reply  Mon Nov 30 17:17:30 2015, yutaro, Update, LSC, Does a baffle in front of ETMY have effect on loss map measurement? element2-2.pngelement0-0.pngelement4-4.png
          Reply  Mon Dec 7 11:11:25 2015, yutaro, Summary, LSC, round trip loss of X arm image1-2.JPGsymmetry.png
Message ID: 11816     Entry time: Wed Nov 25 23:34:52 2015     In reply to: 11810     Reply to this: 11818
Author: yutaro 
Type: Update 
Category: LSC 
Subject: round trip loss of Y arm 

[yutaro, Koji]

Due to the strange behavior (elog 11815) of ASDC level, we checked if it is possible to use POYDC instead of ASDC to measure the power of reflected light of YARM. Attached below is the spectrum of them when the arm is locked. This spectrum shows that it is not bad to use POYDC, in terms of noise. The spectrum of them when ETMY is misaligned looked similar.

So I am going to use POYDC instead of ASDC to measure arm loss of YARM. 


Ed by KA:
The spectra of POYDC and ASDC were measured. We foudn that they have coherence at around 1Hz (good).
It told us that POYDC is about 1/50 smaller than ASDC. Therefore in the attached plot, POYDC x50 is shown.
That's the meaning of the vertical axis unit "ASDC".

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