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Entry  Wed Feb 13 19:09:32 2013, yuta, Summary, General, possible explanations to oval REFL beam REFL_1044844506.bmp
    Reply  Wed Feb 13 19:30:45 2013, Koji, Summary, General, possible explanations to oval REFL beam 
       Reply  Wed Feb 13 19:41:07 2013, yuta, Summary, General, possible explanations to oval REFL beam 
    Reply  Wed Feb 13 22:09:26 2013, Jenne, Update, Alignment, REFL is not clipped 
       Reply  Thu Feb 14 00:10:12 2013, yuta, Summary, Alignment, REFL is not clipped 
          Reply  Thu Feb 14 10:42:41 2013, Jamie, Summary, Alignment, MMT, curved TTs does not explain beam ellipticity at Faraday T.pdfS.pdf
Message ID: 8081     Entry time: Wed Feb 13 22:09:26 2013     In reply to: 8078     Reply to this: 8082
Author: Jenne 
Type: Update 
Category: Alignment 
Subject: REFL is not clipped 

We need to calculate whether this level of astigmatism is expected from the new active TT mirrors, but I claim that the beam is not clipped.

As proof, I provide a video (PS, why did it take me so long to be converted to using video capture??).  I'm just showing the REFL camera, so the REFL beam as seen out on the AS table.  I am moving PRM only.  I can move lots in pitch before I start clipping anywhere.  I have less range in yaw, but I still have space to move around.  This is not how a clipped beam behaves.  The clipping that I see after moving a ways is coincident with clipping seen by the camera looking at the back of the Faraday.  i.e. the first clipping that happens is at the aperture of the Faraday, as the REFL beam enters the FI.  

Also, I'm no longer convinced entirely that the beam entering the Faraday is a nice circle.  I didn't check that very carefully earlier, so I'd like to re-look at the return beam coming from TT1, when the PRM is misaligned such that the return beam is not overlapped with the input beam.  If the beam was circular going into the Faraday, I should have as much range in yaw as I do in pitch.  You can see in the movie that this isn't true.  I'm voting with the "astigmatism caused by non-flat active TT mirrors" camp. 

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