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Entry  Wed Nov 25 23:17:34 2015, yutaro, Update, LSC, strange behavior of ASDC 14.png
    Reply  Mon Nov 30 16:33:06 2015, ericq, Update, LSC, strange behavior of ASDC AScentering.png
       Reply  Mon Nov 30 18:27:30 2015, Koji, Update, LSC, strange behavior of ASDC 
    Reply  Thu Dec 10 12:33:04 2015, yutaro, Update, LSC, strange behavior of ASDC 07.png28.pngASDC.png
       Reply  Thu Dec 10 19:53:22 2015, yutaro, Update, LSC, strange behavior of ASDC 30.png11.png49.png
Message ID: 11871     Entry time: Thu Dec 10 19:53:22 2015     In reply to: 11870
Author: yutaro 
Type: Update 
Category: LSC 
Subject: strange behavior of ASDC 

To check if the strange behavior of ASDC is caused by SR2/SR3 or not, I did the following measurement:

ASDC measures the power of the light reflected by ITMX. POXDC measures the power of the light reflected by ITMX and SRM successively. Then I varied the angle of ITMX in YAW direction and compared the behaviors of ASDC and POXDC.

The results are shown in Attachments 1-3.

As you can see in these figures, the strange up-and-down behavior appeared ONLY in ASDC. Therefore, the cause of this behavior exists between AS table and SRM (I had confirmed that the angle of SRM did not affect ASDC).

And this behavior is fringe-like, as can be seen in the figures (there seems to be 3 "peaks" and 2 "valleys"), so the cause could be interference between main path and not good AR reflection at a mirror after SRM before AS table (I suspect a mirror is flipped mistakenly).   

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