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Entry  Wed Dec 2 17:14:33 2015, yutaro, Update, LSC, Beam on POX11 is possibly not centered well 47.png41.png
    Reply  Fri Dec 4 12:33:52 2015, yutaro, Update, LSC, Beam on POX11 is possibly not centered well image1-3.JPG07.png47.png
       Reply  Fri Dec 4 23:02:13 2015, yutaro, Update, LSC, Beam on POX11 is possibly not centered well image1.JPG56.png04.png
Message ID: 11850     Entry time: Fri Dec 4 23:02:13 2015     In reply to: 11847
Author: yutaro 
Type: Update 
Category: LSC 
Subject: Beam on POX11 is possibly not centered well 

[yutaro, Koji]

Now, the beam on POX11 PD is well centered and well focused.

We found out why POXDC had behaved as reported in elog 11839. There were a few reasons: the beam was not focused enough, hight of a mirror was not matched to the beam well, path of the light reflected by misaligned SRM was occasionally close to the path of POX beam.

Then, What we did is following:

- changed orientation of SRM slightly

- changed the hight of the mirror whose hight had not matched well, by changing the pedestal (hight of which mirror was changed is shown in Attachment 1.)

- put a lens with f=250 mm (where the lens is located is shown in Attachment 1.)

- refined alignment for the POX beam to hit on the center of POX11 PD.  

As a result, POX DC level behaved as shown in Attachment 2&3 when the orientation of ITMX was varied (Attachment 2: POX DC vs ITMX PIT, Attachment 3: POX DC vs ITMX YAW). 

You can see broad plateau when varied in both PIT and YAW directions, and the beam is at the center of the plateau if ITMX is aligned ideally.

 

 

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