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Entry  Tue Feb 21 16:10:29 2012, kiwamu, Update, IOO, degradation in input PZT1 
    Reply  Mon Mar 5 03:50:49 2012, kiwamu, Update, IOO, PZT1 PITCH railing 
       Reply  Mon Mar 5 17:07:58 2012, kiwamu, Update, IOO, realigned MC 
          Reply  Thu Mar 8 23:37:03 2012, kiwamu, Update, IOO, dither Y arm dither script 
          Reply  Wed Mar 14 04:03:37 2012, kiwamu, Update, IOO, PZT1 and associate extra works 
Message ID: 6357     Entry time: Mon Mar 5 17:07:58 2012     In reply to: 6351     Reply to this: 6388   6410
Author: kiwamu 
Type: Update 
Category: IOO 
Subject: realigned MC 

I have slightly shifted the MC beam pointing to relax the PZT1 PITCH. As a result the TRY value went to 0.97 in a first lock trial.

However another issue arose:

   The polarity for controlling the PZT1 PITCH seems to have flipped for some reason.

Since it is still sort of controllable, I am leaving it as it is.

If I remember correctly, sliding the PZT1 pitch value to the positive side brought the beam spot upward in the AS CCD. But now it moves in the opposite way.

Also the ASS feedback looks tending to push the PZT1 pitch to the wrong direction.

I am not 100 % sure if the polarity really flipped, but this is my current conclusion.



(MC pointing)

  1. Locked the Y arm and aligned ITMY and ETMY with the ASS servos such that the beam spot on each test mass is well centered on the test mass.
    • With this process the eigen axis of the Y arm cavity is well prepared.
  2. Checked the beam positions of the prompt reflection light and cavity leakage field in the AS CCD.
    • It looked the incident beam needed to go upward in the CCD view.
  3. Offloaded the MC WFS feedback values to the MC suspension DC biases in a manual way.
  4. Disabled the MC WFS servos. The MC transmitted light didn't become worse, which means the suspensions were well aligned to the input beam
  5. Changed the DC bias in the MC2 PITCH, to bring the beam spot upward. I changed the DC bias by ~ 0.1 or in the EPICS counts.
  6. Aligned the zig-zag steering mirrors on the PSL table to match the incident beam to the new MC eigen beam axis.
    • The transmitted DC light and reflected DC values went back to 27000 counts and 0.58 counts respectively without the WFS servos.
  7. Re-engaged the WFS servos.

Quote from #6351

PZT1 started railing in the pitch direction and because of this TRY doesn't go more than 0.7. I will leave it as it is for tonight.

Tomorrow I will shift the alignment of the MC to make the PZT1 happier. 


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